will SARS-CoV2 infected people develop immunity? Is cross protection possible?

Cross-reactive neutralization of SARS-CoV-2 by serum antibodies from recovered SARS patients and immunized animals

The current COVID-19 pandemic, caused by a novel coronavirus SARS-CoV-2, poses serious threats to public health and social stability, calling for urgent need for vaccines and therapeutics. SARS-CoV-2 is genetically close to SARS-CoV, thus it is important to define the between antigenic cross-reactivity and neutralization. In this study, we firstly analyzed 20 convalescent serum samples collected from SARS-CoV infected individuals during the 2003 SARS outbreak. All patient sera reacted strongly with the S1 subunit and receptor-binding domain (RBD) of SARS-CoV, cross-reacted with the S ectodomain, S1, RBD, and S2 proteins of SARS-CoV-2, and neutralized both SARS-CoV and SARS-CoV-2 S protein-driven infections. Multiple panels of antisera from mice and rabbits immunized with a full-length S and RBD immunogens of SARS-CoV were also characterized, verifying the cross-reactive neutralization against SARS-CoV-2. Interestingly, we found that a palm civet SARS-CoV-derived RBD elicited more potent cross-neutralizing responses in immunized animals than the RBD from a human SARS-CoV strain, informing a strategy to develop a universe vaccine against emerging CoVs. Summary Serum antibodies from SARS-CoV infected patients and immunized animals cross-neutralize SARS-CoV-2 suggests strategies for universe vaccines against emerging CoVs.

Can the protection be among us? Previous viral contacts and prevalent HLA alleles could be avoiding an even more disseminated COVID-19 pandemic.

Background: COVID-19 is bringing scenes of sci-fi movies into real life, and it seems to be far from over. Infected individuals exhibit variable severity, with no relation between the number of cases and mortality, suggesting the involvement of the populational genetic constitution and previous cross-reactive immune contacts in the individuals' disease outcome. Methods: A clustering approach was conducted to investigate the involvement of human MHC alleles with individuals' outcomes. HLA frequencies from affected countries were used to fuel the Hierarchical Clusterization Analysis. The formed groups were compared regarding their death rates. To prospect the T cell targets in SARS-CoV-2, and by consequence, the epitopes that are conferring cross-protection in the current pandemic, we modeled 3D structures of HLA-A*02:01 presenting immunogenic epitopes from SAR-CoV-1, recovered from Immune Epitope Database. These pMHC structures were also compared with models containing the corresponding SARS-CoV-2 epitope, with alphacoronavirus sequences, and with a panel of immunogenic pMHC structures contained in CrossTope. Findings: The combined use of HLA-B*07, HLA-B*44, HLA-DRB1*03, and HLADRB1*04 allowed the clustering of affected countries presenting similar death rates, based only on their allele frequencies. SARS-CoV HLA-A*02:01 epitopes were structurally investigated. It reveals molecular conservation between SARS-CoV-1 and SARS-CoV-2 peptides, enabling the use of formerly SARS-CoV-1 experimental epitopes to inspect actual targets that are conferring cross-protection. Alpha-CoVs and, impressively, viruses involved in human infections share fingerprints of immunogenicity with SARS-CoV peptides. Interpretation: Wide-scale HLA genotyping in COVID-19 patients shall improve prognosis prediction. Structural identification of previous triggers paves the way for herd immunity examination and wide spectrum vaccine development. Funding: This work was supported by the National Council for Scientific and Technological Development (CNPq) and National Council for the Improvement of Higher Education (CAPES) for their support

Does SARS-Cov-2 invade the brain? Translational lessons from animal models

The current coronavirus disease (COVID-19) outbreak, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has raised the possibility of potential neurotropic properties of this virus. Indeed, neurological sequelae of SARS-CoV-2 infection have already been reported and highlight the relevance of considering the neurological impact of coronavirus (CoV) from a translational perspective. Animal models of SARS and Middle East respiratory syndrome, caused by structurally similar CoVs during the 2002 and 2012 epidemics, have provided valuable data on nervous system involvement by CoVs and the potential for central nervous system spread of SARS-CoV-2. One key finding that may unify these pathogens is that all require angiotensin-converting enzyme 2 as a cell entry receptor. The CoV spike glycoprotein, by which SARS-CoV-2 binds to cell membranes, binds angiotensin-converting enzyme 2 with a higher affinity compared with SARS-CoV. The expression of this receptor in neurons and endothelial cells hints that SARS-CoV-2 may have higher neuroinvasive potential compared with previous CoVs. However, it remains to be determined how such invasiveness might contribute to respiratory failure or cause direct neurological damage. Both direct and indirect mechanisms may be of relevance. Clinical heterogeneity potentially driven by differential host immune-mediated responses will require extensive investigation. Development of disease models to anticipate emerging neurological complications and to explore mechanisms of direct or immune-mediated pathogenicity in the short and medium term is therefore of great importance. In this brief review, we describe the current knowledge from models of previous CoV infections and discuss their potential relevance to COVID-19.

Cross-immunity between respiratory coronaviruses may limit COVID-19 fatalities

Of the seven coronaviruses associated with disease in humans, SARS-CoV, MERS-CoV and SARS-CoV-2 cause considerable mortality but also share significant sequence homology, and potentially antigenic epitopes capable of inducing an immune response. The degree of similarity is such that perhaps prior exposure to one virus could confer partial immunity to another. Indeed, data suggests a considerable amount of cross-reactivity and recognition by the hosts immune response between different coronavirus infections. While the ongoing COVID-19 outbreak rapidly overwhelmed medical facilities of particularly Europe and North America, accounting for 78% of global deaths, only 8% of deaths have occurred in Asia where the outbreak originated. Interestingly, Asia and the Middle East have previously experienced multiple rounds of coronavirus infections, perhaps suggesting buildup of acquired immunity to the causative SARS-CoV-2 that underlies COVID-19. This article hypothesizes that a causative factor underlying such low morbidity in these regions is perhaps (at least in part) due to acquired immunity from multiple rounds of coronavirus infections and discusses the mechanisms and recent evidence to support such assertions. Further investigations of such phenomenon would allow us to examine strategies to confer protective immunity, perhaps aiding vaccine development.

Children's vaccines do not induce cross reactivity against SARS-CoV.

In contrast with adults, children infected by severe acute respiratory syndrome-corona virus (SARS-CoV) develop milder clinical symptoms. Because of this, it is speculated that children vaccinated with various childhood vaccines might develop cross immunity against SARS-CoV. Antisera and T cells from mice immunised with various vaccines were used to determine whether they developed cross reactivity against SARS-CoV. The results showed no marked cross reactivity against SARS-CoV, which implies that the reduced symptoms among children infected by SARS-CoV may be caused by other factors.

Long-term and herd immunity against SARS-CoV-2: implications from current and past knowledge

Effective herd immunity against SARS-CoV-2 will be determined on many factors: the percentage of the immune population, the length and effectiveness of the immune response and the stability of the viral epitopes. The required percentage of immune individuals has been estimated to be 50-66% of the population which, given the current infection rates, will take long to be achieved. Furthermore, data from SARS-CoV suggest that the duration of immunity may not be sufficiently significant, while the immunity response against SARS-CoV-2 may not be efficiently effective in all patients, as relapses have already been reported. In addition, the development of mutant strains, which has already been documented, can cause the reemergence of the epidemic. In conclusion, the development of an effective vaccine is an urgent necessity, as long-term natural immunity to SARS-CoV-2 may not be sufficient for the control of the current and future outbreaks.

Effective herd immunity against SARS-CoV-2 will be determined on many factors: the percentage of the immune population, the length and effectiveness of the immune response and the stability of the viral epitopes. The required percentage of immune individuals has been estimated to be 50–66% of the population which, given the current infection rates, will take long to be achieved. Furthermore, data from SARS-CoV suggest that the duration of immunity may not be sufficiently significant, while the immunity response against SARS-CoV-2 may not be efficiently effective in all patients, as relapses have already been reported. In addition, the development of mutant strains, which has already been documented, can cause the reemergence of the epidemic. In conclusion, the development of an effective vaccine is an urgent necessity, as long-term natural immunity to SARS-CoV-2 may not be sufficient for the control of the current and future outbreaks.

How the SARS vaccine effort can learn from HIV—speeding towards the future, learning from the past

A remarkable collaborative effort coordinated by the severe acute respiratory syndrome (SARS) team at WHO resulted in discovery of the etiologic agent of severe acute respiratory syndrome less than 2 months after the announcement of global alert. The development of a vaccine to prevent SARS should be pursued with the same urgency and cooperative spirit, as SARS is highly lethal and, if not controlled during the first few generations of transmission, is likely to become endemic in regions of the world where health-care infrastructure is underdeveloped and epidemiological control measures are weak. The scientific community already learned many important lessons from HIV vaccine development; these should be heeded. For example, consideration should be given to the development of a vaccine that will protect across regional strains of SARS, as the newly emergent coronavirus SARS-coronavirus (SARS-CoV) is proving to be variable and may be mutating in response to immune pressure. SARS-specific research reagents should also be collected and shared. These would include SARS peptides, adjuvants, DNA vaccine vectors and clinical grade viral vectors. Rapidly developing a collaborative approach to developing a SARS vaccine that will be both effective and safe is the only way to go. This article reviews parallels between HIV and SARS and proposes an approach that would accelerate the development of a SARS vaccine.

Protective immunity after COVID-19 has been questioned: What can we do without SARS-CoV-2-IgG detection?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces a severe acute respiratory syndrome that is called COVID-19. Clinical manifestations of COVID-19 include diarrhea, pneumonia, lymphopenia, exhausted lymphocytes, and pro-inflammatory cytokine production. Immunology is part of the process of clinical evolution, but there are some questions around immunity-based protection: (1) why some infected people have only mild symptoms of the disease or are asymptomatic; (2) why delayed and weak antibody responses are associated with severe outcomes; and (3) why positivity in molecular tests does not represent protective antibody IgG. Perhaps T cell responses may be the key to solving those questions. SARS-CoV-2-specific memory T cells persist in peripheral blood and may be capable of providing effective information about protective immunity. The T cells studies can be helpful in elucidating the pathways for development of vaccines, therapies, and diagnostics for COVID-19 and for filling these immunology knowledge gaps.

SARS-CoV originated from bats in 1998 and may still exist in humans

SARS-CoV is believed to originate from civets and was thought to have been eliminated as a threat after the 2003 outbreak. Here, we show that human SARS-CoV (huSARS-CoV) originated directly from bats, rather than civets, by a cross-species jump in 1991, and formed a human-adapted strain in 1998. Since then huSARS-CoV has evolved further into highly virulent strains with genotype T and a 29-nt deletion mutation, and weakly virulent strains with genotype C but without the 29-nt deletion. The former can cause pneumonia in humans and could be the major causative pathogen of the SARS outbreak, whereas the latter might not cause pneumonia in humans, but evolved the ability to co-utilize civet ACE2 as an entry receptor, leading to interspecies transmission between humans and civets. Three crucial time points - 1991, for the cross-species jump from bats to humans; 1998, for the formation of the human-adapted SARS-CoV; and 2003, when there was an outbreak of SARS in humans - were found to associate with anomalously low annual precipitation and high temperatures in Guangdong. Anti-SARS-CoV sero-positivity was detected in 20% of all the samples tested from Guangzhou children who were born after 2005, suggesting that weakly virulent huSARS-CoVs might still exist in humans. These existing but undetected SARS-CoVs have a large potential to evolve into highly virulent strains when favorable climate conditions occur, highlighting a potential risk for the reemergence of SARS.

Chapter 36 SARS

Abstract Five years after the first severe acute respiratory syndrome (SARS) outbreak, several candidate SARS-coronavirus (CoV) vaccines are at various stages of preclinical and clinical development. Based on the observation that SARSCoV infection is efficiently controlled upon passive transfer of antibodies directed against the spike (S) protein of SARS-CoV, vaccines containing the S protein have been formulated. Animals immunized with inactivated whole virus vaccines or live-recombinant vaccines expressing the SARS-CoV S protein (e.g., using rabies virus, vesicular stomatitis virus, bovine parainfluenza virus type 3, adenovirus, or attenuated vaccinia virus MVA as a vector), as well as mice immunized with DNA vaccines expressing the S protein gene all developed neutralizing antibodies to SARS-CoV and were protected against SARS-CoV challenge. Although much effort has been focused on developing a SARS vaccine, the commercial viability of such a vaccine for SARS-CoV will ultimately depend on whether the virus re-emerges in the near future. This vaccine should induce highly cross-reactive neutralizing antibodies to protect against newly emerging viruses related to SARS-CoV and protect both the gastrointestinal and respiratory tract in the absence of significant side effects. Given the fact that in the previous outbreak mainly the elderly succumbed to the infection, special attention should be given to vaccines that are able to efficiently protect aged individuals.

Antibody Dependent Enhancement Due to Original Antigenic Sin and the Development of SARS

Human coronavirus (HCoV) is one of the most common causes of respiratory tract infections throughout the world. Two phenomena observed so far in the development of the SARS-CoV-2 pandemic deserve further attention. First, the relative absence of clinical signs of infections in children, second, the early appearance of IgG in certain patients. From the point of view of immune system physiology, such an early rise of specific IgG is expected in secondary immune responses when memory to a cross-reactive antigen is present, usually from an earlier infection with a coronavirus. It is actually typical for the immune system to respond, to what it already knows, a phenomenon that has been observed in many infections with closely related viruses and has been termed "original antigenic sin." The question then arises whether such cross-reactive antibodies are protective or not against the new virus. The worst scenario would be when such cross-reactive memory antibodies to related coronaviruses would not only be non-protective but even enhance infection and the clinical course. Such a phenomenon of antibody dependent enhancement (ADE) has already been described in several viral infections. Thus, the development of IgG against SARS-CoV-2 in the course of COVID-19 might not be a simple sign of viral clearance and developing protection against the virus. On the contrary, due to cross-reaction to related coronavirus strains from earlier infections, in certain patients IgG might enhance clinical progression due to ADE. The patient's viral history of coronavirus infection might be crucial to the development of the current infection with SARS-CoV-2. Furthermore, it poses a note of caution when treating COVID-19 patients with convalescent sera.

Protective immunity after COVID-19 has been questioned: what can we do without SARS-CoV-2-IgG detection?

Abstract Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces a severe acute respiratory syndrome that is called COVID-19. Clinical manifestations of COVID-19 include diarrhea, pneumonia, lymphopenia, exhausted lymphocytes, and pro-inflammatory cytokine production. Immunology is part of the process of clinical evolution, but there are some questions around immunity-based protection: (1) why some infected people have only mild symptoms of the disease or are asymptomatic; (2) why delayed and weak antibody responses are associated with severe outcomes; and (3) why positivity in molecular tests does not represent protective antibody IgG. Perhaps T cell responses may be the key to solving those questions. SARS-CoV-2-specific memory T cells persist in peripheral blood and may be capable of providing effective information about protective immunity. The T cells studies can be helpful in elucidating the pathways for development of vaccines, therapies, and diagnostics for COVID-19 and for filling these immunology knowledge gaps.

Human coronavirus (HCoV) is one of the most common causes of respiratory tract infections throughout the world. Two phenomena observed so far in the development of the SARS-CoV-2 pandemic deserve further attention. First, the relative absence of clinical signs of infections in children, second, the early appearance of IgG in certain patients. From the point of view of immune system physiology, such an early rise of specific IgG is expected in secondary immune responses when memory to a cross-reactive antigen is present, usually from an earlier infection with a coronavirus. It is actually typical for the immune system to respond, to what it already knows, a phenomenon that has been observed in many infections with closely related viruses and has been termed “original antigenic sin.” The question then arises whether such cross-reactive antibodies are protective or not against the new virus. The worst scenario would be when such cross-reactive memory antibodies to related coronaviruses would not only be non-protective but even enhance infection and the clinical course. Such a phenomenon of antibody dependent enhancement (ADE) has already been described in several viral infections. Thus, the development of IgG against SARS-CoV-2 in the course of COVID-19 might not be a simple sign of viral clearance and developing protection against the virus. On the contrary, due to cross-reaction to related coronavirus strains from earlier infections, in certain patients IgG might enhance clinical progression due to ADE. The patient's viral history of coronavirus infection might be crucial to the development of the current infection with SARS-CoV-2. Furthermore, it poses a note of caution when treating COVID-19 patients with convalescent sera.

Long-term coexistence of SARS-CoV-2 with antibody response in COVID-19 patients

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causing coronavirus disease 2019 (COVID-19) has spread worldwide. Whether antibodies are important for the adaptive immune responses against SARS-CoV-2 infection needs to be determined. Here, 26 cases of COVID-19 in Jinan, China, were examined and shown to be mild or with common clinical symptoms, and no case of severe symptoms was found among these patients. Strikingly, a subset of these patients had SARS-CoV-2 and virus-specific IgG coexist for an unexpectedly long time, with two cases for up to 50 days. One COVID-19 patient who did not produce any SARS-CoV-2-bound IgG successfully cleared SARS-CoV-2 after 46 days of illness, revealing that without antibody-mediated adaptive immunity, innate immunity alone may still be powerful enough to eliminate SARS-CoV-2. This report may provide a basis for further analysis of both innate and adaptive immunity in SARS-CoV-2 clearance, especially in nonsevere cases.

Spread of SARS-CoV-2.

Does SARS‐Cov‐2 invade the brain? Translational lessons from animal models

The current coronavirus disease (COVID‐19) outbreak, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has raised the possibility of potential neurotropic properties of this virus. Indeed, neurological sequelae of SARS‐CoV‐2 infection have already been reported and highlight the relevance of considering the neurological impact of coronavirus (CoV) from a translational perspective. Animal models of SARS and Middle East respiratory syndrome, caused by structurally similar CoVs during the 2002 and 2012 epidemics, have provided valuable data on nervous system involvement by CoVs and the potential for central nervous system spread of SARS‐CoV‐2. One key finding that may unify these pathogens is that all require angiotensin‐converting enzyme 2 as a cell entry receptor. The CoV spike glycoprotein, by which SARS‐CoV‐2 binds to cell membranes, binds angiotensin‐converting enzyme 2 with a higher affinity compared with SARS‐CoV. The expression of this receptor in neurons and endothelial cells hints that SARS‐CoV‐2 may have higher neuroinvasive potential compared with previous CoVs. However, it remains to be determined how such invasiveness might contribute to respiratory failure or cause direct neurological damage. Both direct and indirect mechanisms may be of relevance. Clinical heterogeneity potentially driven by differential host immune‐mediated responses will require extensive investigation. Development of disease models to anticipate emerging neurological complications and to explore mechanisms of direct or immune‐mediated pathogenicity in the short and medium term is therefore of great importance. In this brief review, we describe the current knowledge from models of previous CoV infections and discuss their potential relevance to COVID‐19.

Characterization of spike glycoprotein of SARS-CoV-2 on virus entry and its immune cross-reactivity with SARS-CoV

Since 2002, beta coronaviruses (CoV) have caused three zoonotic outbreaks, SARS-CoV in 2002-2003, MERS-CoV in 2012, and the newly emerged SARS-CoV-2 in late 2019. However, little is currently known about the biology of SARS-CoV-2. Here, using SARS-CoV-2 S protein pseudovirus system, we confirm that human angiotensin converting enzyme 2 (hACE2) is the receptor for SARS-CoV-2, find that SARS-CoV-2 enters 293/hACE2 cells mainly through endocytosis, that PIKfyve, TPC2, and cathepsin L are critical for entry, and that SARS-CoV-2 S protein is less stable than SARS-CoV S. Polyclonal anti-SARS S1 antibodies T62 inhibit entry of SARS-CoV S but not SARS-CoV-2 S pseudovirions. Further studies using recovered SARS and COVID-19 patients' sera show limited cross-neutralization, suggesting that recovery from one infection might not protect against the other. Our results present potential targets for development of drugs and vaccines for SARS-CoV-2.

Potent cross-reactive neutralization of SARS coronavirus isolates by human monoclonal antibodies.

The severe acute respiratory syndrome coronavirus (SARS-CoV) caused a worldwide epidemic in late 2002/early 2003 and a second outbreak in the winter of 2003/2004 by an independent animal-to-human transmission. The GD03 strain, which was isolated from an index patient of the second outbreak, was reported to resist neutralization by the human monoclonal antibodies (hmAbs) 80R and S3.1, which can potently neutralize isolates from the first outbreak. Here we report that two hmAbs, m396 and S230.15, potently neutralized GD03 and representative isolates from the first SARS outbreak (Urbani, Tor2) and from palm civets (SZ3, SZ16). These antibodies also protected mice challenged with the Urbani or recombinant viruses bearing the GD03 and SZ16 spike (S) glycoproteins. Both antibodies competed with the SARS-CoV receptor, ACE2, for binding to the receptor-binding domain (RBD), suggesting a mechanism of neutralization that involves interference with the SARS-CoV-ACE2 interaction. Two putative hot-spot residues in the RBD (Ile-489 and Tyr-491) were identified within the SARS-CoV spike that likely contribute to most of the m396-binding energy. Residues Ile-489 and Tyr-491 are highly conserved within the SARS-CoV spike, indicating a possible mechanism of the m396 cross-reactivity. Sequence analysis and mutagenesis data show that m396 might neutralize all zoonotic and epidemic SARS-CoV isolates with known sequences, except strains derived from bats. These antibodies exhibit cross-reactivity against isolates from the two SARS outbreaks and palm civets and could have potential applications for diagnosis, prophylaxis, and treatment of SARS-CoV infections.

Serologic cross-reactivity of SARS-CoV-2 with endemic and seasonal Betacoronaviruses

In order to properly understand the spread of SARS-CoV-2 infection and development of humoral immunity, researchers have evaluated the presence of serum antibodies of people worldwide experiencing the pandemic. These studies rely on the use of recombinant proteins from the viral genome in order to identify serum antibodies that recognize SARS-CoV-2 epitopes. Here, we discuss the cross-reactivity potential of SARS-CoV-2 antibodies with the full spike proteins of four other Betacoronaviruses that cause disease in humans, MERS-CoV, SARS-CoV, HCoV-OC43, and HCoV-HKU1. Using enzyme-linked immunosorbent assays (ELISAs), we detected the potential cross-reactivity of antibodies against SARS-CoV-2 towards the four other coronaviruses, with the strongest cross-recognition between SARS-CoV-2 and SARS /MERS-CoV antibodies, as expected based on sequence homology of their respective spike proteins. Further analysis of cross-reactivity could provide informative data that could lead to intelligently designed pan-coronavirus therapeutics or vaccines.

In silico multi-epitope vaccine against covid19 showing effective interaction with HLA-B*15:03

The recent outbreak of severe acute respiratory syndrome (SARS) coronavirus (CoV)-2 (SARS-CoV-2) causing coronavirus disease (covid19) has posed a great threat to human health. Previous outbreaks of SARS-CoV and Middle East respiratory Syndrome CoV (MERS-CoV) from the same CoV family had posed similar threat to human health and economic growth. To date, not even a single drug specific to any of these CoVs has been developed nor any anti-viral vaccine is available for the treatment of diseases caused by CoVs. Subunits present in spike glycoproteins of SARS-CoV and SARS-CoV-2 are involved in binding to human ACE2 Receptor which is the primary method of viral invasion. As it has been observed in the previous studies that there are very minor differences in the spike glycoproteins of SARS-CoV and SARS-CoV-2. SARS-CoV-2 has an additional furin cleavage site that makes it different from SARS-CoV (Walls et al., 2020). In this study, we have analyzed spike glycoproteins of SARS-CoV-2 and SARS-CoV phylogenetically and subjected them to selection pressure analysis. Selection pressure analysis has revealed some important sites in SARS-CoV-2 and SARS-CoV spike glycoproteins that might be involved in their pathogenicity. Further, we have developed a potential multi-epitope vaccine candidate against SARS-CoV-2 by analyzing its interactions with HLA-B*15:03 subtype. This vaccine consists of multiple T-helper (TH) cells, B-cells, and Cytotoxic T-cells (CTL) epitopes joined by linkers and an adjuvant to increase its immunogenicity. Conservation of selected epitopes in SARS, MERS, and human hosts, suggests that the designed vaccine could provide cross-protection. The vaccine is designed in silico by following a reverse vaccinology method acknowledging its antigenicity, immunogenicity, toxicity, and allergenicity. The vaccine candidate that we have designed as a result of this work shows promising result indicating its potential capability of simulating an immune response.

Potential neurological effects of severe COVID-19 infection

Coronaviruses (CoVs) are large positive stranded enveloped RNA viruses that generally cause enteric and respiratory diseases in humans and in animals. Most human CoVs have recently attracted global attention to their lethal potential and great infectious capacity. A highly pathogenic CoV, called COVID-19 or SARS-CoV-2, dramatically emerged in December 2019 in Wuhan, China. This new CoV has caused severe pneumonia in China and rapidly spreads around the world, the COVID-19 pandemic. Growing evidence pieces show that viruses, such as CoVs, can enter the central nervous system from different pathways and inducing neurotoxicity. Therefore, it is urgent to make clear whether SARS-CoV-2 has access to the central nervous system and can cause direct neuronal effects. Moreover, a brain-lung-brain axis is been proposed from the scientific community where severe neurological dysfunction and injury are associated with lung injury, and vice versa. In this axis, virus-induced inflammation and oxidative stress could be the common mechanisms responsible for CoV neurological symptoms. Therefore, is important to make clear whether SARS-CoV-2 lung damage can cause direct or indirect neuronal effects.

SARS-CoV-2 targets cortical neurons of 3D human brain organoids and shows neurodegeneration-like effects

COVID-19 pandemic caused by SARS-CoV-2 infection is a public health emergency. COVID-19 typically exhibits respiratory illness. Unexpectedly, emerging clinical reports indicate that neurological symptoms continue to rise, suggesting detrimental effects of SARS-CoV-2 on the central nervous system (CNS). Here, we show that a Düsseldorf isolate of SARS-CoV-2 enters 3D human brain organoids within two days of exposure. Using COVID-19 convalescent serum, we identified that SARS-CoV-2 preferably targets soma of cortical neurons but not neural stem cells, the target cell type of ZIKA virus. Imaging cortical neurons of organoids reveal that SARS-CoV-2 exposure is associated with missorted Tau from axons to soma, hyperphosphorylation, and apparent neuronal death. Surprisingly, SARS-CoV-2 co-localizes specifically with Tau phosphorylated at Threonine-231 in the soma, indicative of early neurodegeneration-like effects. Our studies, therefore, provide initial insights into the impact of SARS-CoV-2 as a neurotropic virus and emphasize that brain organoids could model CNS pathologies of COVID-19. One sentence summary COVID-19 modeling in human brain organoids

Spread of SARS-CoV-2

Coronaviruses (CoVs) are large positive stranded enveloped RNA viruses that generally cause enteric and respiratory diseases in humans and in animals. Most human CoVs have recently attracted global attention to their lethal potential and great infectious capacity. A highly pathogenic CoV, called COVID-19 or SARS‐CoV2, dramatically emerged in December 2019 in Wuhan, China. This new CoV has caused severe pneumonia in China and rapidly spreads around the world, the COVID-19 pandemic. Growing evidence pieces show that viruses, such as CoVs, can enter the central nervous system from different pathways and inducing neurotoxicity. Therefore, it is urgent to make clear whether SARS-CoV-2 has access to the central nervous system and can cause direct neuronal effects. Moreover, a brain–lung–brain axis is been proposed from the scientific community where severe neurological dysfunction and injury are associated with lung injury, and vice versa. In this axis, virus-induced inflammation and oxidative stress could be the common mechanisms responsible for CoV neurological symptoms. Therefore, is important to make clear whether SARS-CoV-2 lung damage can cause indirect or indirect neuronal effects.

Since 2002, beta coronaviruses (CoV) have caused three zoonotic outbreaks, SARS-CoV in 2002–2003, MERS-CoV in 2012, and the newly emerged SARS-CoV-2 in late 2019. However, little is currently known about the biology of SARS-CoV-2. Here, using SARS-CoV-2 S protein pseudovirus system, we confirm that human angiotensin converting enzyme 2 (hACE2) is the receptor for SARS-CoV-2, find that SARS-CoV-2 enters 293/hACE2 cells mainly through endocytosis, that PIKfyve, TPC2, and cathepsin L are critical for entry, and that SARS-CoV-2 S protein is less stable than SARS-CoV S. Polyclonal anti-SARS S1 antibodies T62 inhibit entry of SARS-CoV S but not SARS-CoV-2 S pseudovirions. Further studies using recovered SARS and COVID-19 patients’ sera show limited cross-neutralization, suggesting that recovery from one infection might not protect against the other. Our results present potential targets for development of drugs and vaccines for SARS-CoV-2.

Neuroinvasive potential of SARS-CoV-2 revealed in a human brain organoid model

Although COVID-19 is considered to be primarily a respiratory disease, SARS-CoV-2 affects multiple organ systems including the central nervous system (CNS). Reports indicate that 30-60% of patients with COVID-19 suffer from CNS symptoms. Yet, there is no consensus whether the virus can infect the brain, or what the consequences of infection are. Following SARS-CoV-2 infection of human brain organoids, clear evidence of infection was observed, with accompanying metabolic changes in the infected and neighboring neurons. Further, no evidence for the type I interferon responses was detected. We demonstrate that neuronal infection can be prevented either by blocking ACE2 with antibodies or by administering cerebrospinal fluid from a COVID-19 patient. Finally, using mice overexpressing human ACE2, we demonstrate in vivo that SARS-CoV-2 neuroinvasion, but not respiratory infection, is associated with mortality. These results provide evidence for the neuroinvasive capacity of SARS-CoV2, and an unexpected consequence of direct infection of neurons by SARS-CoV2.

SARS-CoV-2 and SARS-CoV Spike-RBD Structure and Receptor Binding Comparison and Potential Implications on Neutralizing Antibody and Vaccine Development

SARS-CoV-2 and SARS-CoV share a common human receptor ACE2. Protein-protein interaction structure modeling indicates that spike-RBD of the two viruses also has similar overall binding conformation and binding free energy to ACE2. In vitro assays using recombinant ACE2 proteins and ACE2 expressing cells confirmed the two coronaviruses’ similar binding affinities to ACE2. The above studies provide experimental supporting evidences and possible explanation for the high transmissibility observed in the SARS-CoV-2 outbreak. Potent ACE2-blocking SARS-CoV neutralizing antibodies showed limited cross-binding and neutralizing activities to SARS-CoV-2. ACE2-non-blocking SARS-CoV RBD antibodies, though with weaker neutralizing activities against SARS-CoV, showed positive cross-neutralizing activities to SARS-CoV-2 with an unknown mechanism. These findings suggest a trade-off between the efficacy and spectrum for therapeutic antibodies to different coronaviruses, and hence highlight the possibilities and challenges in developing broadly protecting antibodies and vaccines against SARS-CoV-2 and its future mutants.

Cross-neutralization of SARS-CoV-2 by a human monoclonal SARS-CoV antibody.

SARS-CoV-2 is a newly emerged coronavirus responsible for the current COVID-19 pandemic that has resulted in more than 3.7 million infections and 260,000 deaths as of 6 May 20201,2. Vaccine and therapeutic discovery efforts are paramount to curb the pandemic spread of this zoonotic virus. The SARS-CoV-2 spike (S) glycoprotein promotes entry into host cells and is the main target of neutralizing antibodies. Here we describe multiple monoclonal antibodies targeting SARS-CoV-2 S identified from memory B cells of an individual who was infected with SARS-CoV in 2003. One antibody, named S309, potently neutralizes SARS-CoV-2 and SARS-CoV pseudoviruses as well as authentic SARS-CoV-2 by engaging the S receptor-binding domain. Using cryo-electron microscopy and binding assays, we show that S309 recognizes a glycan-containing epitope that is conserved within the sarbecovirus subgenus, without competing with receptor attachment. Antibody cocktails including S309 along with other antibodies identified here further enhanced SARS-CoV-2 neutralization and may limit the emergence of neutralization-escape mutants. These results pave the way for using S309- and S309-containing antibody cocktails for prophylaxis in individuals at high risk of exposure or as a post-exposure therapy to limit or treat severe disease.

Long-term protection from SARS coronavirus infection conferred by a single immunization with an attenuated VSV-based vaccine

Abstract Although the recent SARS coronavirus (SARS-CoV) that appeared in 2002 has now been contained, the possibility of re-emergence of SARS-CoV remains. Due to the threat of re-emergence, the overall fatality rate of ∼10%, and the rapid dispersion of the virus via international travel, viable vaccine candidates providing protection from SARS are clearly needed. We developed an attenuated VSV recombinant (VSV-S) expressing the SARS coronavirus (SARS-CoV) spike (S) protein. In cells infected with this recombinant, S protein was synthesized, glycosylated at approximately 17 Asn residues, and transported via the Golgi to the cell surface. Mice vaccinated with VSV-S developed SARS-neutralizing antibody and were able to control a challenge with SARS-CoV performed at 1 month or 4 months after a single vaccination. We also demonstrated, by passive antibody transfer, that the antibody response induced by the vaccine was sufficient for controlling SARS-CoV infection. A VSV-vectored SARS vaccine could have significant advantages over other SARS vaccine candidates described to date.

Cross-reactive Antibody Response between SARS-CoV-2 and SARS-CoV Infections

The World Health Organization has declared the ongoing outbreak of COVID-19, which is caused by a novel coronavirus SARS-CoV-2, a pandemic. There is currently a lack of knowledge about the antibody response elicited from SARS-CoV-2 infection. One major immunological question concerns antigenic differences between SARS-CoV-2 and SARS-CoV. We address this question by analyzing plasma from patients infected by SARS-CoV-2 or SARS-CoV and from infected or immunized mice. Our results show that, although cross-reactivity in antibody binding to the spike protein is common, cross-neutralization of the live viruses may be rare, indicating the presence of a non-neutralizing antibody response to conserved epitopes in the spike. Whether such low or non-neutralizing antibody response leads to antibody-dependent disease enhancement needs to be addressed in the future. Overall, this study not only addresses a fundamental question regarding antigenicity differences between SARS-CoV-2 and SARS-CoV but also has implications for immunogen design and vaccine development.

SARS-CoV-2: An Update on Potential Antivirals in Light of SARS-CoV Antiviral Drug Discoveries.

Coronaviruses (CoVs) are a group of RNA viruses that are associated with different diseases in animals, birds, and humans. Human CoVs (HCoVs) have long been known to be the causative agents of mild respiratory illnesses. However, two HCoVs associated with severe respiratory diseases are Severe Acute Respiratory Syndrome-CoV (SARS-CoV) and Middle East Respiratory Syndrome-CoV (MERS-CoV). Both viruses resulted in hundreds of deaths after spreading to several countries. Most recently, SARS-CoV-2 has emerged as the third HCoV causing severe respiratory distress syndrome and viral pneumonia (known as COVID-19) in patients from Wuhan, China, in December 2019. Soon after its discovery, SARS-CoV-2 spread to all countries, resulting in millions of cases and thousands of deaths. Since the emergence of SARS-CoV, many research groups have dedicated their resources to discovering effective antivirals that can treat such life-threatening infections. The rapid spread and high fatality rate of SARS-CoV-2 necessitate the quick discovery of effective antivirals to control this outbreak. Since SARS-CoV-2 shares 79% sequence identity with SARS-CoV, several anti-SARS-CoV drugs have shown promise in limiting SARS-CoV-2 replication in vitro and in vivo. In this review, we discuss antivirals described for SARS-CoV and provide an update on therapeutic strategies and antivirals against SARS-CoV-2. The control of the current outbreak will strongly depend on the discovery of effective and safe anti-SARS-CoV-2 drugs.

Two-way antigenic cross-reactivity between severe acute respiratory syndrome coronavirus (SARS-CoV) and group 1 animal CoVs is mediated through an antigenic site in the N-terminal region of the SARS-CoV nucleoprotein.

In 2002, severe acute respiratory syndrome-associated coronavirus (SARS-CoV) emerged in humans, causing a global epidemic. By phylogenetic analysis, SARS-CoV is distinct from known CoVs and most closely related to group 2 CoVs. However, no antigenic cross-reactivity between SARS-CoV and known CoVs was conclusively and consistently demonstrated except for group 1 animal CoVs. We analyzed this cross-reactivity by an enzyme-linked immunosorbent assay (ELISA) and Western blot analysis using specific antisera to animal CoVs and SARS-CoV and SARS patient convalescent-phase or negative sera. Moderate two-way cross-reactivity between SARS-CoV and porcine CoVs (transmissible gastroenteritis CoV [TGEV] and porcine respiratory CoV [PRCV]) was mediated through the N but not the spike protein, whereas weaker cross-reactivity occurred with feline (feline infectious peritonitis virus) and canine CoVs. Using Escherichia coli-expressed recombinant SARS-CoV N protein and fragments, the cross-reactive region was localized between amino acids (aa) 120 to 208. The N-protein fragments comprising aa 360 to 412 and aa 1 to 213 reacted specifically with SARS convalescent-phase sera but not with negative human sera in ELISA; the fragment comprising aa 1 to 213 cross-reacted with antisera to animal CoVs, whereas the fragment comprising aa 360 to 412 did not cross-react and could be a potential candidate for SARS diagnosis. Particularly noteworthy, a single substitution at aa 120 of PRCV N protein diminished the cross-reactivity. We also demonstrated that the cross-reactivity is not universal for all group 1 CoVs, because HCoV-NL63 did not cross-react with SARS-CoV. One-way cross-reactivity of HCoV-NL63 with group 1 CoVs was localized to aa 1 to 39 and at least one other antigenic site in the N-protein C terminus, differing from the cross-reactive region identified in SARS-CoV N protein. The observed cross-reactivity is not a consequence of a higher level of amino acid identity between SARS-CoV and porcine CoV nucleoproteins, because sequence comparisons indicated that SARS-CoV N protein has amino acid identity similar to that of infectious bronchitis virus N protein and shares a higher level of identity with bovine CoV N protein within the cross-reactive region. The TGEV and SARS-CoV N proteins are RNA chaperons with long disordered regions. We speculate that during natural infection, antibodies target similar short antigenic sites within the N proteins of SARS-CoV and porcine group 1 CoVs that are exposed to an immune response. Identification of the cross-reactive and non-cross-reactive N-protein regions allows development of SARS-CoV-specific antibody assays for screening animal and human sera.

Serological differentiation between COVID-19 and SARS infections.

In response to the coronavirus disease 2019 (COVID-19) outbreak, caused by the SARS-CoV-2 virus, multiple diagnostic tests are required globally for acute disease diagnosis, contact tracing, monitoring of asymptomatic infection rates and assessing herd immunity. While PCR remains the frontline test of choice in the acute diagnostic setting, serological tests are urgently needed to fulfil the other requirements. Unlike PCR tests which are highly specific for each virus, cross-reactivity could potentially be a major challenge for COVID-19 antibody tests considering there are six other coronaviruses known to infect humans. Among the human pathogens, SARS-CoV is genetically most related to SARS-CoV-2 sharing approximately 80% sequence identity and both belong to the species SARS related coronavirus (SARSr-CoV) in the genus Betacoronavirus of family Coronaviridae. In this study, we developed and compared the performance of four different serological tests to comprehensively assess the cross-reactivity between COVID-19 and SARS patient sera. Our results indicate that there is a significant cross-reactivity when N protein of either SARS-CoV or SARS-CoV-2 is used. The S1 or RBD derived the spike (S) protein offers better specificity. Amongst the different platforms, capture ELISA performed best. Finally, we found that SARS survivors all have significant level of antibodies remaining in their blood 17 years after infection. We discovered that anti-N antibodies waned more than anti-RBD antibodies, and the latter is known to play a more important role in providing protective immunity.

Neutralizing antibody and soluble ACE2 inhibition of a replication-competent VSV-SARS-CoV-2 and a clinical isolate of SARS-CoV-2.

Abstract Antibody-based interventions against SARS-CoV-2 could limit morbidity, mortality, and possibly transmission. An anticipated correlate of such countermeasures is the level of neutralizing antibodies against the SARS-CoV-2 spike protein, which engages with host ACE2 receptor for entry. Using an infectious molecular clone of vesicular stomatitis virus (VSV) expressing eGFP as a marker of infection, we replaced the glycoprotein gene (G) with the spike protein of SARS-CoV-2 (VSV-eGFP-SARS-CoV-2) and developed a high-throughput imaging-based neutralization assay at biosafety level 2. We also developed a focus-reduction neutralization test with a clinical isolate of SARS-CoV-2 at biosafety level 3. Comparing the neutralizing activities of various antibodies and ACE2-Fc soluble decoy protein in both assays revealed a high degree of concordance. These assays will help define correlates of protection for antibody-based countermeasures and vaccines against SARS-CoV-2. Additionally, replication-competent VSV-eGFP-SARS-CoV-2 provides a tool for testing inhibitors of SARS-CoV-2 mediated entry under reduced biosafety containment.

Cross-reactive antibody response between SARS-CoV-2 and SARS-CoV infections

Summary The World Health Organization has declared the ongoing outbreak of COVID-19, which is caused by a novel coronavirus SARS-CoV-2, as pandemic. There is currently a lack of knowledge about the antibody response elicited from SARS-CoV-2 infection. One major immunological question concerns antigenic differences between SARS-CoV-2 and SARS-CoV. We address this question by analyzing plasma from patients infected by SARS-CoV-2 or SARS-CoV, and from infected or immunized mice. Our results show that, while cross-reactivity in antibody binding to the spike protein is common, cross-neutralization of the live viruses may be rare, indicating the presence of non-neutralizing antibody response to conserved epitopes in the spike. Whether such low or non-neutralizing antibody response leads to antibody-dependent disease enhancement needs to be addressed in the future. Overall, this study not only addresses a fundamental question regarding antigenicity differences between SARS-CoV-2 and SARS-CoV, but also has implications for immunogen design and vaccine development.

SARS-CoV-2 will continue to circulate in the human population: an opinion from the point of view of the virus-host relationship

At the population level, the virus-host relationship is not set up to end with the complete elimination of either or both. Pathogen-resistant individuals will always remain in the host population. In turn, the virus can never completely eliminate the host population, because evolutionarily such an event is a dead end for the virus as an obligate intracellular parasite. A certain existential balance exists in the virus-host relationship. Against this backdrop, viral epidemics and pandemics only become manifest and egregious to human beings when tens and hundreds of thousands of people die and the question emerges what caused the high mortality peaks on the death chart. The answer seems clear; the emerging strain of the virus is new to the host population, and new mutations of the virus and natural selection will lead to a survival of only genetically resistant individuals in a host population. The dangers inherent to a novel virus are due to new features generally inthe molecular structure of proteins, which enable the virus to infect the cells of the host organism more intensively, dramatically challenging host immunity, and thus be transmitted more readily in the host population. In this article, we will concentrate on the facts currently available about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has caused COVID-19 (coronavirus disease 2019) pandemic and try to predict its development and consequences based on the virus-host relationship. In fact, only two scenarios will occur simultaneously in the very near future: people who are genetically resistant to the virus will get sick, recover, and develop immunity, while people who are sensitive to the virus will need drugs and vaccines, which will have to be researched and developed if they are to recover. If the pandemic does not stop, in a few decades it is anticipated that SARS-CoV-2 will become as safe as the four non-severe acute respiratory syndrome human coronaviruses (HCoV-NL63, HCoV-HKU1, HCoV-OC43, and HCoV-229E) currently circulating but causing low mortality in the human population.

The importance of naturally attenuated SARS-CoV-2in the fight against COVID-19

The current SARS-CoV-2 pandemic is wreaking havoc throughout the world and has rapidly become a global health emergency. A central question concerning COVID-19 is why some individuals become sick and others not. Many have pointed already at variation in risk factors between individuals. However, the variable outcome of SARS-CoV-2 infections may, at least in part, be due also to differences between the viral subspecies with which individuals are infected. A more pertinent question is how we are to overcome the current pandemic. A vaccine against SARS-CoV-2 would offer significant relief, although vaccine developers have warned that design, testing and production of vaccines may take a year if not longer. Vaccines are based on a handful of different designs (i), but the earliest vaccines were based on the live, attenuated virus. As has been the case for other viruses during earlier pandemics, SARS-CoV-2 will mutate and may naturally attenuate over time (ii). What makes the current pandemic unique is that, thanks to state-of-the-art nucleic acid sequencing technologies, we can follow in detail how SARS-CoV-2 evolves while it spreads. We argue that knowledge of naturally emerging attenuated SARS-CoV-2 variants across the globe should be of key interest in our fight against the pandemic.

The emergence of a novel coronavirus (SARS-CoV-2) disease and their neuroinvasive propensity may affect in COVID-19 patients

An outbreak of a novel coronavirus (SARS-CoV-2) infection has recently emerged and rapidly spreading in humans causing a significant threat to international health and the economy. Rapid assessment and warning are crucial for an outbreak analysis in response to serious public health. SARS-CoV-2 shares highly homological sequences with SARS-CoVs causing highly lethal pneumonia with respiratory distress and clinical symptoms similar to those reported for SARS-CoV and MERS-CoV infections. Notably, some COVID-19 patients also expressed neurologic signs like nausea, headache, and vomiting. Several studies have reported that coronaviruses are not only causing respiratory illness but also invade the central nervous system through a synapse-connected route. SARS-CoV infections are reported in both patients and experimental animals' brains. Interestingly, some COVID-19 patients have shown the presence of SARS-CoV-2 virus in their cerebrospinal fluid. Considering the similarities between SARS-CoV and SARS-CoV-2 in various aspects, it remains to clarify whether the potent invasion of SARS-CoV-2 may affect in COVID-19 patients. All these indicate that more detailed criteria are needed for the treatment and the prevention of SARS-CoV-2 infected patients. In the absence of potential interventions for COVID-19, there is an urgent need for an alternative strategy to control the spread of this disease.

Masking the general population might attenuate COVID-19 outbreaks

The effect of masking the general population on a COVID-19 epidemic is estimated by computer simulation using two separate state-of-the-art web-based softwares, one of them calibrated for the SARS-CoV-2 virus. The questions addressed are these: 1. Can mask use by the general population limit the spread of SARS-CoV-2 in a country? 2. What types of masks exist, and how elaborate must a mask be to be effective against COVID-19? 3. Does the mask have to be applied early in an epidemic? 4. A brief general discussion of masks and some possible future research questions regarding masks and SARS-CoV-2. Results are as follows: (1) The results indicate that any type of mask, even simple home-made ones, may be effective. Masks use seems to have an effect in lowering new patients even the protective effect of each mask (here dubbed"one-mask protection") is low. Strict adherence to mask use does not appear to be critical. However, increasing the one-mask protection to>50% was found to be advantageous. Masks seemed able to reduce overflow of capacity, e.g. of intensive care. As the default parameters of the software included another intervention, it seems possible to combine mask and other interventions. (2) Masks do seem to reduce the number of new cases even if introduced at a late stage in an epidemic. However, early implementation helps reduce the cumulative and total number of cases. (3) The simulations suggest that it might be possible to eliminate a COVID-19 outbreak by widespread mask use during a limited period. The results from these simulations are encouraging, but do not necessarily represent the real-life situation, so it is suggested that clinical trials of masks are now carried out while continuously monitoring effects and side-effects.

Molecular mechanisms and epidemiology of COVID-19 from an allergist's perspective

The global pandemic caused by the newly described severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused worldwide suffering and death of unimaginable magnitude from coronavirus disease 2019 (COVID-19). The virus is transmitted through aerosol droplets, and causes severe acute respiratory syndrome. SARS-CoV-2 uses the receptor-binding domain of its spike protein S1 to attach to the host angiotensin-converting enzyme 2 receptor in lung and airway cells. Binding requires the help of another host protein, transmembrane protease serine S1 member 2. Several factors likely contribute to the efficient transmission of SARS-CoV-2. The receptor-binding domain of SARS-CoV-2 has a 10- to 20-fold higher receptor-binding capacity compared with previous pandemic coronaviruses. In addition, because asymptomatic persons infected with SARS-CoV-2 have high viral loads in their nasal secretions, they can silently and efficiently spread the disease. PCR-based tests have emerged as the criterion standard for the diagnosis of infection. Caution must be exercised in interpreting antibody-based tests because they have not yet been validated, and may give a false sense of security of being "immune" to SARS-CoV-2. We discuss how the development of some symptoms in allergic rhinitis can serve as clues for new-onset COVID-19. There are mixed reports that asthma is a risk factor for severe COVID-19, possibly due to differences in asthma endotypes. The rapid spread of COVID-19 has focused the efforts of scientists on repurposing existing Food and Drug Administration-approved drugs that inhibit viral entry, endocytosis, genome assembly, translation, and replication. Numerous clinical trials have been launched to identify effective treatments for COVID-19. Initial data from a placebo-controlled study suggest faster time to recovery in patients on remdesivir; it is now being evaluated in additional controlled studies. As discussed in this review, till effective vaccines and treatments emerge, it is important to understand the scientific rationale of pandemic-mitigation strategies such as wearing facemasks and social distancing, and implement them.

Molecular mechanisms and epidemiology of COVID-19 from an allergist’s perspective

The global pandemic caused by the newly described severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused worldwide suffering and death of unimaginable magnitude from coronavirus disease 2019 (COVID-19). The virus is transmitted through aerosol droplets, and causes severe acute respiratory syndrome. SARS-CoV-2 uses the receptor-binding domain of its spike protein S1 to attach to the host angiotensin-converting enzyme 2 receptor in lung and airway cells. Binding requires the help of another host protein, transmembrane protease serine S1 member 2. Several factors likely contribute to the efficient transmission of SARS-CoV-2. The receptor-binding domain of SARS-CoV-2 has a 10- to 20-fold higher receptor-binding capacity compared with previous pandemic coronaviruses. In addition, because asymptomatic persons infected with SARS-CoV-2 have high viral loads in their nasal secretions, they can silently and efficiently spread the disease. PCR-based tests have emerged as the criterion standard for the diagnosis of infection. Caution must be exercised in interpreting antibody-based tests because they have not yet been validated, and may give a false sense of security of being “immune” to SARS-CoV-2. We discuss how the development of some symptoms in allergic rhinitis can serve as clues for new-onset COVID-19. There are mixed reports that asthma is a risk factor for severe COVID-19, possibly due to differences in asthma endotypes. The rapid spread of COVID-19 has focused the efforts of scientists on repurposing existing Food and Drug Administration–approved drugs that inhibit viral entry, endocytosis, genome assembly, translation, and replication. Numerous clinical trials have been launched to identify effective treatments for COVID-19. Initial data from a placebo-controlled study suggest faster time to recovery in patients on remdesivir; it is now being evaluated in additional controlled studies. As discussed in this review, till effective vaccines and treatments emerge, it is important to understand the scientific rationale of pandemic-mitigation strategies such as wearing facemasks and social distancing, and implement them.

Protections against the Risk of Airborne SARS-CoV-2 Infection

An in-silico approach to develop of a multi-epitope vaccine candidate against SARS-CoV-2 envelope (E) protein

Since the first appearance of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS- CoV-2) in China on December 2019, the world has now witnessed the emergence of the SARS- CoV-2 outbreak. Therefore, due to the high transmissibility rate of virus, there is an urgent need to design and develop vaccines against SARS-CoV-2 to prevent more cases affected by the virus. In this study, a computational approach is proposed for vaccine design against the envelope (E) protein of SARS-CoV-2, which contains a conserved sequence feature. First, we sought to gain potential B-cell and T-cell epitopes for vaccine designing against SARS-CoV-2. Second, we attempted to develop a multi-epitope vaccine. Immune targeting of such epitopes could theoretically provide defense against SARS-CoV-2. Finally, we evaluated the affinity of the vaccine to major histocompatibility complex (MHC) molecules to stimulate the immune system response to this vaccine. We also identified a collection of B-cell and T-cell epitopes derived from E proteins that correspond identically to SARS-CoV-2 E proteins. The in-silico design of our potential vaccine against E protein of SARS-CoV-2 demonstrated a high affinity to MHC molecules, and it can be a candidate to make a protection against this pandemic event.

SARS-CoV-2 Virulence: Interplay of Floating Virus-Laden Particles, Climate, and Humans

With the emergence of COVID-19, it is important to address the possible scenarios of SARS-CoV-2 virulence. Although several researchers have addressed the possible mechanisms of enveloped virus transfection, for example, influenza, here, the relationship between exhaled virus laden-particles, the climate, and transfection probability is discussed by interpreting the findings of prior studies. Importantly, the higher probability of viral transfection in cold and dry public spaces such as near cold shelves of groceries is illustrated. Thus, additional protective measures in such spaces are recommended.

Key residues of the receptor binding motif in the spike protein of SARS-CoV-2 that interact with ACE2 and neutralizing antibodies

Coronavirus disease 2019 (COVID-19), caused by the novel human coronavirus SARS-CoV-2, is currently a major threat to public health worldwide. The viral spike protein binds the host receptor angiotensin-converting enzyme 2 (ACE2) via the receptor-binding domain (RBD), and thus is believed to be a major target to block viral entry. Both SARS-CoV-2 and SARS-CoV share this mechanism. Here we functionally analyzed the key amino acid residues located within receptor binding motif of RBD that may interact with human ACE2 and available neutralizing antibodies. The in vivo experiments showed that immunization with either the SARS-CoV RBD or SARS-CoV-2 RBD was able to induce strong clade-specific neutralizing antibodies in mice; however, the cross-neutralizing activity was much weaker, indicating that there are distinct antigenic features in the RBDs of the two viruses. This finding was confirmed with the available neutralizing monoclonal antibodies against SARS-CoV or SARS-CoV-2. It is worth noting that a newly developed SARS-CoV-2 human antibody, HA001, was able to neutralize SARS-CoV-2, but failed to recognize SARS-CoV. Moreover, the potential epitope residues of HA001 were identified as A475 and F486 in the SARS-CoV-2 RBD, representing new binding sites for neutralizing antibodies. Overall, our study has revealed the presence of different key epitopes between SARS-CoV and SARS-CoV-2, which indicates the necessity to develop new prophylactic vaccine and antibody drugs for specific control of the COVID-19 pandemic although the available agents obtained from the SARS-CoV study are unneglectable.

Analysis of Serologic Cross-Reactivity Between Common Human Coronaviruses and SARS-CoV-2 Using Coronavirus Antigen Microarray

The current practice for diagnosis of SARS-CoV-2 infection relies on PCR testing of nasopharyngeal or respiratory specimens in a symptomatic patient at high epidemiologic risk. This testing strategy likely underestimates the true prevalence of infection, creating the need for serologic methods to detect infections missed by the limited testing to date. Here, we describe the development of a coronavirus antigen microarray containing immunologically significant antigens from SARS-CoV-2, in addition to SARS-CoV, MERS-CoV, common human coronavirus strains, and other common respiratory viruses. A preliminary study of human sera collected prior to the SARS-CoV-2 pandemic demonstrates overall high IgG reactivity to common human coronaviruses and low IgG reactivity to epidemic coronaviruses including SARS-CoV-2, with some cross-reactivity of conserved antigenic domains including S2 domain of spike protein and nucleocapsid protein. This array can be used to answer outstanding questions regarding SARS-CoV-2 infection, including whether baseline serology for other coronaviruses impacts disease course, how the antibody response to infection develops over time, and what antigens would be optimal for vaccine development.

Serological differentiation between COVID-19 and SARS infections

SARS-CoV-2: too infectious to handle?

Receptor-binding domain as a target for developing SARS vaccines.

A decade ago, severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) caused a global pandemic with a mortality rate of 10%. Reports of recent outbreaks of a SARS-like disease caused by Middle East respiratory syndrome coronavirus (MERS-CoV) have raised serious concerns of a possible reemergence of SARS-CoV, either by laboratory escape or the presence of a natural reservoir. Therefore, the development of effective and safe SARS vaccines is still needed. Based on our previous studies, we believe that the receptor-binding domain (RBD) in the S1 subunit of the SARS-CoV spike (S) protein is the most important target for developing a SARS vaccine. In particular, RBD of S protein contains the critical neutralizing domain (CND), which is able to induce highly potent neutralizing antibody response and cross-protection against divergent SARS-CoV strains. Furthermore, a RBD-based subunit vaccine is expected to be safer than other vaccines that may induce Th2-type immunopathology. This review will discuss key advances in the development of RBD-based SARS vaccines and the possibility of using a similar strategy to develop vaccines against MERS-CoV.

Human antibodies can neutralize SARS-CoV-2

ACE2 polymorphisms and individual susceptibility to SARS-CoV-2 infection: insights from an in silico study

The current SARS covid-19 epidemic spread appears to be influenced by ethnical, geographical and sex-related factors that may involve genetic susceptibility to diseases. Similar to SARS-CoV, SARS-CoV-2 exploits angiotensin-converting enzyme 2 (ACE2) as a receptor to invade cells, notably type II alveolar epithelial cells. Importantly, ACE2 gene is highly polymorphic. Here we have used in silico tools to analyze the possible impact of ACE2 single-nucleotide polymorphisms (SNPs) on the interaction with SARS-CoV-2 spike glycoprotein. We found that S19P (common in African people) and K26R (common in European people) were, among the most diffused SNPs worldwide, the only two SNPs that were able to potentially affect the interaction of ACE2 with SARS-CoV-2 spike. FireDock simulations demonstrated that while S19P may decrease, K26R might increase the ACE2 affinity for SARS-CoV-2 Spike. This finding suggests that the S19P may genetically protect, and K26R may predispose to more severe SARS-CoV-2 disease.

Cross-sectional evaluation of humoral responses against SARS-CoV-2 Spike

The SARS-CoV-2 virus is responsible for the current worldwide coronavirus disease 2019 (COVID-19) pandemic, infecting millions of people and causing hundreds of thousands of deaths. The Spike glycoprotein of SARS-CoV-2 mediates viral entry and is the main target for neutralizing antibodies. Understanding the antibody response directed against SARS-CoV-2 is crucial for the development of vaccine, therapeutic and public health interventions. Here we performed a cross-sectional study on 98 SARS-CoV-2-infected individuals to evaluate humoral responses against the SARS-CoV-2 Spike. The vast majority of infected individuals elicited anti-Spike antibodies within 2 weeks after the onset of symptoms. The levels of receptor-binding domain (RBD)-specific IgG persisted overtime, while the levels of anti-RBD IgM decreased after symptoms resolution. Some of the elicited antibodies cross-reacted with other human coronaviruses in a genus-restrictive manner. While most of individuals developed neutralizing antibodies within the first two weeks of infection, the level of neutralizing activity was significantly decreased over time. Our results highlight the importance of studying the persistence of neutralizing activity upon natural SARS-CoV-2 infection.

Anti-SARS coronavirus agents: a patent review (2008 - present).

INTRODUCTION A novel coronavirus (CoV), unlike previous typical human coronaviruses (HCoVs), was identified as causative agent for severe acute respiratory syndrome (SARS). SARS first surfaced as a pandemic in late 2002 and originated in southern China. SARS-CoV rapidly spread to > 30 countries by 2003, infecting nearly 8,000 people and causing around 800 fatalities. After 10 years of silence, a 2012 report alarmed researchers about the emergence of a new strain of CoV causing SARS-like disease. AREAS COVERED To combat SARS, scientists applied for patents on various therapeutic agents, including small-molecule inhibitors targeting the essential proteases, helicase and other proteins of the virus, natural products, approved drugs, molecules binding to the virus, neutralizing antibodies, vaccines, anti-sense RNA, siRNA and ribozyme against SARS-CoV. In this article, the patents published from 2008 to the present for the new therapeutics that could potentially be used in the prophylaxis and treatment of SARS are reviewed. EXPERT OPINION The therapeutic interventions or prophylaxis discussed in this review seems to offer promising solutions to tackle SARS. Rather than being complacent about the results, we should envisage how to transform them into drug candidates that may be useful in combating SARS and related viral infections in the future.

Does COVID19 infect the brain? If so, smokers might be at a higher risk.

COVID19 is a devastating global pandemic with epicenters in China, Italy, Spain, and now the United States. While the majority of infected cases appear mild, in some cases individuals present serious cardiorespiratory complications with possible long-term lung damage. Infected individuals report a range of symptoms from headaches to shortness of breath to taste and smell loss. To that end, less is known about the how the virus may impact different organ systems. The SARS-CoV2 virus, which is responsible for COVID19, is highly similar to SARS-CoV. Both viruses have evolved an ability to enter host cells through direct interaction with the angiotensin converting enzyme 2 (ACE2) protein at the surface of many cells. Published findings indicate that SARS-CoV can enter the human nervous system with evidence from both postmortem brains and detection in cerebrospinal fluid of infected individuals. Here we consider the ability of SARS-CoV2 to enter and infect the human nervous system based on the strong expression of the ACE2 target throughout the brain. Moreover, we predict that nicotine exposure through various kinds of smoking (cigarettes, e-cigarettes, or vape) can increase the risk for COVID19 neuroinfection based on known functional interactions between the nicotinic receptor and ACE2. We advocate for higher surveillance and analysis of neuro-complications in infected cases.

Any contribution of the season change to the spread of covid-19 caused by sars-cov-2?

Background: Most people raise a similar concern during this tough time of the COVID-19 pandemic caused by SARS-CoV-2 infection regarding when this outbreak will come to end. A recent thorough-general study on the success of China dealing with COVID-19 outbreak has concluded to recommend the need for a multi-sectoral approach to prevent future outbreaks of emerging infectious diseases including for the still-occurring COVID-19 outbreak with the initiative for the highest interest of the health of mankind Discussion: The prevalence of SARS-CoV as the predecessor of SARS-CoV-2 has been concluded to be more suitable in spring than autumn and winter, with nothing prevalence in summer. No coincidence that SARS-CoV-2 infection has outbreak around the world from January 2020 to the present, April 2020, as ever predicted to reoccur based on its predecessor, SARS-CoV, that have prevalence been high since January, February, March, April, until early May 2003. As opposed to other seasons, summer has low atmospheric pressure as its exemption that provenly causes virus inactivation. Conclusions: The denotative nature of SARS-CoV-2 seems to reflect its predecessor, SARS-CoV, which begins nearing the end of the year and reaches its optimum hence in spring, thereafter, finally ends in summer. Low atmospheric pressure in the summer impresses that it is the potential cause of ending the outbreak by deactivating SARS-CoV-2, apart from the hot temperature of weather. The knowledge to be gained here is further closely correlated to the fact that coronavirus is able to have genetic recombination that may bring about new genotypes and, consequently, outbreaks later occurring.

Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein

The emergence of SARS-CoV-2 has resulted in >90,000 infections and >3,000 deaths. Coronavirus spike (S) glycoproteins promote entry into cells and are the main target of antibodies. We show that SARS-CoV-2 S uses ACE2 to enter cells and that the receptor-binding domains of SARS-CoV-2 S and SARS-CoV S bind with similar affinities to human ACE2, correlating with the efficient spread of SARS-CoV-2 among humans. We found that the SARS-CoV-2 S glycoprotein harbors a furin cleavage site at the boundary between the S(1)/S(2) subunits, which is processed during biogenesis and sets this virus apart from SARS-CoV and SARS-related CoVs. We determined cryo-EM structures of the SARS-CoV-2 S ectodomain trimer, providing a blueprint for the design of vaccines and inhibitors of viral entry. Finally, we demonstrate that SARS-CoV S murine polyclonal antibodies potently inhibited SARS-CoV-2 S mediated entry into cells, indicating that cross-neutralizing antibodies targeting conserved S epitopes can be elicited upon vaccination.

Development of a COVID-19 vaccine based on the receptor binding domain displayed on virus-like particles

The recently ermerging disease COVID-19 is caused by the new SARS-CoV-2 virus first detected in the city of Wuhan, China. From there it has been rapidly spreading inside and outside China. With initial death rates around 4%, COVID-19 patients at longer distances from Wuhan showed reduced mortality as was previously observed for the SARS coronavirus. However, the new coronavirus spreads more strongly, as it sheds long before onset of symptoms or may be transmitted by people without symptoms. Rapid development of a protective vaccine against COVID-19 is therefore of paramount importance. Here we demonstrate that recombinantly expressed receptor binding domain (RBD) of the spike protein homologous to SARS binds to ACE2, the viral receptor. Higly repetitive display of RBD on immunologically optimized virus-like particles derived from cucumber mosaic virus resulted in a vaccine candidate (RBD-CuMVTT) that induced high levels of specific antibodies in mice which were able to block binding of spike protein to ACE2 and potently neutralized the SARS-CoV-2 virus in vitro.

The first three months of the COVID-19 epidemic: Epidemiological evidence for two separate strains of SARS-CoV-2 viruses spreading and implications for prevention strategies

About one month after the COVID-19 epidemic peaked in Mainland China and SARS-CoV-2 migrated from China westward to Europe and then the U.S., the epidemiological data begin to provide important insights into the risks associated with the disease and the effectiveness of intervention strategies. Like other respiratory diseases, including the 2003 SARS epidemic, the virus remains only about two months in any given population, yet the peak incidence and the lethality can vary. The data suggest that at least two strains of the 2020 SARS-CoV-2 virus have evolved during its migration from Mainland China to Europe. South Korea, Iran, and Italy were hit by the more dangerous "SKII" variant. While the epidemic in China is about to end, and in Europe about to level off, the course of the epidemic in the younger US population is still increasing and the peak level will likely depend on which of the strains has entered the US first. The same models that help us to understand the epidemic also help us to choose prevention strategies. While containment merely prolongs the time the disease circulates until the proportion of immune people is high enough for "herd immunity", reducing disease severity, either by vaccination or by early treatment of complications, is the best strategy against a respiratory virus disease.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2): a global pandemic and treatment strategies

The emergence and rapid spread of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a potentially fatal disease, is swiftly leading to public health crises worldwide. The origin of SARS-CoV-2 infection was first reported in people exposed to a seafood market in Wuhan City, China in December 2019. It has been suggested that the infection is likely to be of zoonotic origin and transmitted to humans through a not-yet-known intermediary. As of 22 May 2020, the World Health Organization reported that there were approximately 4,995,996 confirmed cases and 327,821 deaths. SARS-CoV-2 is transmitted via inhalation or direct contact with droplets from infected people. It has an incubation period ranging from 2 to ≥14 days. The rate of spread of SARS-CoV-2 is greater than that for severe acute respiratory syndrome coronavirus and Middle East respiratory coronavirus. The symptoms are similar to influenza (i.e. breathlessness, sore throat and fatigue) and infected cases are isolated and treated. Infection is mild in most cases, but in elderly (>50 years) patients and those with cardiac and respiratory disorders, it may progress to pneumonia, acute respiratory distress syndrome and multi-organ failure. People with strong immunity or those who have developed herd immunity are asymptomatic. The fatality rate ranges from 3% to 4%. Recommended methods for diagnosis of COVID-19 are molecular tests (e.g. polymerase chain reaction) on respiratory secretions, chest scan and common laboratory diagnosis. Currently, treatment is essentially supportive, and the role of antiviral agents is yet to be established as a vaccine is not yet available. This review will focus on epidemiology, symptoms, transmission, pathogenesis, ongoing available treatments and future perspectives of SARS-CoV-2.

A systematic review of antibody mediated immunity to coronaviruses: antibody kinetics, correlates of protection, and association of antibody responses with severity of disease

The duration and nature of immunity generated in response to SARS-CoV-2 infection is unknown. Many public health responses and modeled scenarios for COVID-19 outbreaks caused by SARSCoV-2 assume that infection results in an immune response that protects individuals from future infections or illness for some amount of time. The timescale of protection is a critical determinant of the future impact of the pathogen. The presence or absence of protective immunity due to infection or vaccination (when available) will affect future transmission and illness severity. The dynamics of immunity and nature of protection are relevant to discussions surrounding therapeutic use of convalescent sera as well as efforts to identify individuals with protective immunity. Here, we review the scientific literature on antibody immunity to coronaviruses, including SARS-CoV-2 as well as the related SARS-CoV-1, MERS-CoV and human endemic coronaviruses (HCoVs). We reviewed 1281 abstracts and identified 322 manuscripts relevant to 5 areas of focus: 1) antibody kinetics, 2) correlates of protection, 3) immunopathogenesis, 4) antigenic diversity and cross-reactivity, and 5) population seroprevalence. While studies of SARS-CoV-2 are necessary to determine immune responses to it, evidence from other coronaviruses can provide clues and guide future research.

SARS

The emergence of SARS-CoV-2 has resulted in >90,000 infections and >3,000 deaths. Coronavirus spike (S) glycoproteins promote entry into cells and are the main target of antibodies. We show that SARS-CoV-2 S uses ACE2 to enter cells and that the receptor-binding domains of SARS-CoV-2 S and SARS-CoV S bind with similar affinities to human ACE2, correlating with the efficient spread of SARS-CoV-2 among humans. We found that the SARS-CoV-2 S glycoprotein harbors a furin cleavage site at the boundary between the S1/S2 subunits, which is processed during biogenesis and sets this virus apart from SARS-CoV and SARS-related CoVs. We determined cryo-EM structures of the SARS-CoV-2 S ectodomain trimer, providing a blueprint for the design of vaccines and inhibitors of viral entry. Finally, we demonstrate that SARS-CoV S murine polyclonal antibodies potently inhibited SARS-CoV-2 S mediated entry into cells, indicating that cross-neutralizing antibodies targeting conserved S epitopes can be elicited upon vaccination.

Pre-existing immunity to SARS-CoV-2: the knowns and unknowns

SARS, MERS and SARS-CoV-2 (COVID-19) treatment: a patent review

INTRODUCTION: Coronavirus has been responsible for several virus outbreaks since 2003, caused by SARS-CoV-1, MERS-CoV, and currently SARS-CoV-2 (COVID-19), the causative agent of coronavirus disease in 2019. COVID-19 has become a global public health emergency because of its high virulence and mortality capacity. This patent review aims to provide an overview of the patents that present possible treatments for SARS-CoV-1, SARS-CoV-2 and MERS-CoV. AREAS COVERED: To treat SARS, MERS and SARS-CoV-2, researchers have filed patents for a number of therapeutic agents. Most of the treatments found were protease inhibitors aimed at proteases such as PLpro, 3 CLpro, RNA helicase, and Spike protein, or used monoclonal antibodies and interferons. In addition, the use of Chinese folk medicine and its multitude of medicinal plants with strong antiviral properties was reinforced. Thus, these therapies used in previous epidemics can serve as an aid in the new pandemic by SARS-CoV-2 and be a starting point for new treatments. EXPERT OPINION: The various antiviral alternatives presented in this review offer therapeutic options to fight coronavirus infections. If shown to be effective, these drugs may be extremely important in the current pandemic.

Increasing host cellular receptor-angiotensin-converting enzyme 2 expression by coronavirus may facilitate 2019-nCoV (or SARS-CoV-2) infection

The ongoing outbreak of a new coronavirus (2019-nCoV, or severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) has caused an epidemic of the acute respiratory syndrome known as coronavirus disease (COVID-19) in humans. SARS-CoV-2 rapidly spread to multiple regions of China and multiple other countries, posing a serious threat to public health. The spike (S) proteins of SARS-CoV-1 and SARS-CoV-2 may use the same host cellular receptor, angiotensin-converting enzyme 2 (ACE2), for entering host cells. The affinity between ACE2 and the SARS-CoV-2 S protein is much higher than that of ACE2 binding to the SARS-CoV S protein, explaining why SARS-CoV-2 seems to be more readily transmitted from human to human. Here, we report that ACE2 can be significantly upregulated after infection of various viruses, including SARS-CoV-1 and SARS-CoV-2, or by the stimulation with inflammatory cytokines such as interferons. We propose that SARS-CoV-2 may positively induce its cellular entry receptor, ACE2, to accelerate its replication and spread; high inflammatory cytokine levels increase ACE2 expression and act as high-risk factors for developing COVID-19, and the infection of other viruses may increase the risk of SARS-CoV-2 infection. Therefore, drugs targeting ACE2 may be developed for the future emerging infectious diseases caused by this cluster of coronaviruses.

The brain, another potential target organ, needs early protection from SARS-CoV-2 neuroinvasion

SARS: future research and vaccine

Summary Severe acute respiratory syndrome (SARS) is a new infectious disease of the 21st century that has pandemic potential. A novel coronavirus (CoV) was identified as its aetiological agent and its genome was sequenced within months of the World Health Organisation issuing a global threat on SARS. The high morbidity and mortality of this potentially pandemic infection demands a rapid research response to develop effective antiviral treatment and vaccine. This will depend on understanding the pathogenesis and immune response to SARS CoV. Further understanding of the ecology of SARS CoV in human and animals will help prevent future cross species transmission. Likewise for the super-spreading events, clarification of the underlying reasons will be important to prevent a large scale outbreak of SARS. Lastly it is of utmost importance that international research collaboration should be strengthened to deal with SARS and any other emerging infectious disease that can seriously threaten our future.

Cross-reactive antibody response between SARS-CoV-2 and SARS-CoV infections

The World Health Organization has recently declared the ongoing outbreak of COVID-19, which is caused by a novel coronavirus SARS-CoV-2, as pandemic. There is currently a lack of knowledge in the antibody response elicited from SARS-CoV-2 infection. One major immunological question is concerning the antigenic differences between SARS-CoV-2 and SARS-CoV. We address this question by using plasma from patients infected by SARS-CoV-2 or SARS-CoV, and plasma obtained from infected or immunized mice. Our results show that while cross-reactivity in antibody binding to the spike protein is common, cross-neutralization of the live viruses is rare, indicating the presence of non-neutralizing antibody response to conserved epitopes in the spike. Whether these non-neutralizing antibody responses will lead to antibody-dependent disease enhancement needs to be addressed in the future. Overall, this study not only addresses a fundamental question regarding the antigenicity differences between SARS-CoV-2 and SARS-CoV, but also has important implications in vaccine

Molecular Mechanism of Evolution and Human Infection with SARS-CoV-2

The outbreak of a novel coronavirus, which was later formally named the severe acute respiratory coronavirus 2 (SARS-CoV-2), has caused a worldwide public health crisis. Previous studies showed that SARS-CoV-2 is highly homologous to SARS-CoV and infects humans through the binding of the spike protein to ACE2. Here, we have systematically studied the molecular mechanisms of human infection with SARS-CoV-2 and SARS-CoV by protein-protein docking and MD simulations. It was found that SARS-CoV-2 binds ACE2 with a higher affinity than SARS-CoV, which may partly explain that SARS-CoV-2 is much more infectious than SARS-CoV. In addition, the spike protein of SARS-CoV-2 has a significantly lower free energy than that of SARS-CoV, suggesting that SARS-CoV-2 is more stable and may survive a higher temperature than SARS-CoV. This provides insights into the evolution of SARS-CoV-2 because SARS-like coronaviruses have originated in bats. Our computation also suggested that the RBD-ACE2 binding for SARS-CoV-2 is much more temperature-sensitive than that for SARS-CoV. Thus, it is expected that SARS-CoV-2 would decrease its infection ability much faster than SARS-CoV when the temperature rises. These findings would be beneficial for the disease prevention and drug/vaccine development of SARS-CoV-2.

Considerations around the SARS-CoV-2 Spike Protein with particular attention to COVID-19 brain infection and neurological symptoms.

Spike protein (S protein) is the virus 'key' to infect cells being able to strongly bind to the human angiotensin-converting enzyme2 (ACE2), as it has been reported. In fact, Spike structure and function is known to be highly important for cell infection as well as entering the brain. Growing evidence indicates that different types of coronaviruses not only affect the respiratory system, but they might also invade the central nervous system (CNS). However, very few evidence have been so far reported on the presence of COVID-19 in the brain and the potential exploitation, by this virus, of lung to brain axis to reach neurons has not completely understood. In this article we assessed the SARS-CoV and SARS-CoV-2 Spike protein sequence, structure and electrostatic potential using computational approaches. Our results showed that the S proteins of SARS-CoV-2 and SARS-CoV are highly similar, sharing a sequence identity of 77%. In addition, we found that the SARS-CoV-2 S protein is slightly more positively charged than that of SARS-CoV since it contains four more positively charged residues and five less negatively charged residues which may lead to an increased affinity to bind to negatively charged regions of other molecules through non-specific and specific interactions. Analyzing of the S protein binds to the host ACE2 receptor showed a 30% higher binding energy for SARS-CoV-2 than the SARS-CoV S protein. These results might be useful for understanding the mechanism of cell entry, blood brain barrier crossing and clinical features related to the CNS infection by SARS-CoV-2.

SARS, MERS and SARS-CoV-2 (COVID-19) treatment: a patent review.

Introduction: Coronavirus has been responsible for several virus outbreaks since 2003, caused by SARS-CoV-1, MERS-CoV, and currently SARS-CoV-2 (COVID-19), the causative agent of coronavirus disease in 2019. COVID-19 has become a global public health emergency because of its high virulence and mortality capacity. This patent review aims to provide an overview of the patents that present possible treatments for SARS-CoV-1, SARS-CoV-2 and MERS-CoV.Areas covered: To treat SARS, MERS and SARS-CoV-2, researchers have filed patents for a number of therapeutic agents. Most of the treatments found were protease inhibitors aimed at proteases such as PLpro, 3CLpro, RNA helicase, and Spike protein, or used monoclonal antibodies and interferons. In addition, the use of Chinese folk medicine and its multitude of medicinal plants with strong antiviral properties was reinforced. Thus, these therapies used in previous epidemics can serve as an aid in the new pandemic by SARS-CoV-2 and be a starting point for new treatments.Expert opinion: The various antiviral alternatives presented in this review offer therapeutic options to fight coronavirus infections. If shown to be effective, these drugs may be extremely important in the current pandemic.

Vaccine design for severe acute respiratory syndrome coronavirus.

Severe acute respiratory syndrome (SARS) is an emerging infectious disease caused by a new coronavirus (SARS-CoV). Recent studies suggest that SARS-CoV is zoonotic and may have a broad host range besides humans. Although the global outbreak of SARS has been contained, there are serious concerns over its re-emergence and bioterrorism potential. As a part of preparedness, development of a safe and effective vaccine is one of the highest priorities in fighting SARS. A number of candidate vaccines, using a variety of approaches, are under development. The first vaccine tested in clinical trial is made from the inactivated form of SARS-CoV. Several live attenuated, genetically engineered or vector vaccines encoding the SARS-CoV spike (S) protein have been in pre-clinical studies. These vaccine candidates are effective in terms of eliciting protective immunity in the vaccinated animals. However, caution should be taken with the safety of whole virus or full-length S protein-based immunogens in humans because they may induce harmful immune or inflammatory responses. We propose to use the receptor-binding domain (RBD) of SARS-CoV S protein (residues 318--510) for developing a safe and effective subunit SARS vaccine, as it is not only a functional domain that mediates virus-receptor binding but also a major neutralization determinant of SARSCoV. It has been demonstrated that the RBD of SARS-CoV S protein contains multiple conformational epitopes capable of inducing highly potent neutralizing antibody responses and protective immunity.

Coronavirus infections: Epidemiological, clinical and immunological features and hypotheses

Coronaviruses (CoVs) are a large family of enveloped, positive-strand RNA viruses Four human CoVs (HCoVs), the non-severe acute respiratory syndrome (SARS)-like HCoVs (namely HCoV 229E, NL63, OC43, and HKU1), are globally endemic and account for a substantial fraction of upper respiratory tract infections Non-SARS-like CoV can occasionally produce severe diseases in frail subjects but do not cause any major (fatal) epidemics In contrast, SARS like CoVs (namely SARS-CoV and Middle-East respiratory syndrome coronavirus, MERS-CoV) can cause intense short-lived fatal outbreaks The current epidemic caused by the highly contagious SARS-CoV-2 and its rapid spread globally is of major concern There is scanty knowledge on the actual pandemic potential of this new SARS-like virus It might be speculated that SARS-CoV-2 epidemic is grossly underdiagnosed and that the infection is silently spreading across the globe with two consequences: (i) clusters of severe infections among frail subjects could haphazardly occur linked to unrecognized index cases;(ii) the current epidemic could naturally fall into a low-level endemic phase when a significant number of subjects will have developed immunity Understanding the role of paucisymptomatic subjects and stratifying patients according to the risk of developing severe clinical presentations is pivotal for implementing reasonable measures to contain the infection and to reduce its mortality Whilst the future evolution of this epidemic remains unpredictable, classic public health strategies must follow rational patterns The emergence of yet another global epidemic underscores the permanent challenges that infectious diseases pose and underscores the need for global cooperation and preparedness, even during inter-epidemic periods

Single-cell RNA Analysis on ACE2 Expression Provides Insight into SARS-CoV-2 Blood Entry and Heart Injury

COVID-19 is a global pandemic with high infectivity and pathogenicity, accounting for tens of thousands of deaths worldwide. Recent studies have found that the pathogen of COVID-19, SARS-CoV-2, shares the same cell receptor Angiotensin converting enzyme II (ACE2) with SARS-CoV. The pathological investigation of COVID-19 death showed that the lung had the characteristics of pulmonary fibrosis. However, how SARS-CoV-2 spreads from the lungs to other organs has not yet been determined. Here, we performed an unbiased evaluation of cell-type specific expression of ACE2 in healthy and fibrotic lungs, as well as in normal and failed adult human hearts, using published single-cell RNA-seq data. We found that ACE2 expression in fibrotic lungs mainly locates in arterial vascular cells, which might provide the route for bloodstream spreading of SARS-CoV-2. The failed human hearts have a higher percentage of ACE2-expressing cardiomyocytes, and SARS-CoV-2 might attack cardiomyocytes through the bloodstream in patients with heart failure. Moreover, ACE2 was highly expressed in cells infected by RSV or MERS-CoV and in mice treated by LPS. Our findings indicate that patients with pulmonary fibrosis, heart failure, and virus infection have a higher risk and are more susceptible to SARS-CoV-2 infection. SARS-CoV-2 might attack other organs by getting into the bloodstream. This work provides new insights into SARS-CoV-2 blood entry and heart injury and might propose a therapeutic strategy to prevent patients from developing severe complications.

Long-term Co-existence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) with Antibody Response in Non-severe Coronavirus Disease 2019 (COVID-19) Patients

Severe acute respiratory syndrome coronavirus 2 infection causing coronavirus disease 2019 has spread worldwide. Whether antibodies are important for the adaptive immune responses against SARS-CoV-2 infection needs to be determined. Here, 26 cases of COVID-19 in Jinan, China, were examined and shown to be mild or with common clinical symptoms and no cases of severe symptoms were found among these patients. A striking feature of some patients is that SARS-CoV-2 could exist in patients who have virus-specific IgG antibodies for a very long period, with one case for up to 36 days. One COVID-19 patient who did not produce any SARS-CoV-2-bound IgG successfully cleared SARS-CoV-2 after 46 days of illness, revealing that without antibody-mediated adaptive immunity, innate immunity may still be powerful enough to eliminate SARS-CoV-2. Overall, this report may provide a basis for further analysis of both innate and adaptive immunity in SARS-CoV-2 clearance, especially in non-severe cases. This study also has implications for understanding the pathogenesis and treatment of SARS-CoV-2.

Occupational health responses to COVID-19: What lessons can we learn from SARS?

On 31 December 2019, the World Health Organization (WHO) received reports of pneumonia cases of unknown etiology in the city of Wuhan in Hubei Province, China. The agent responsible was subsequently identified as a coronavirus-SARS-CoV-2. The WHO declared this disease as a Public Health Emergency of International Concern at the end of January 2020. This event evoked a sense of déjà vu, as it has many similarities to the outbreak of severe acute respiratory syndrome (SARS) of 2002-2003. Both illnesses were caused by a zoonotic novel coronavirus, both originated during winter in China and both spread rapidly all over the world. However, the case-fatality rate of SARS (9.6%) is higher than that of COVID-19 (<4%). Another zoonotic novel coronavirus, MERS-CoV, was responsible for the Middle East respiratory syndrome, which had a case-fatality rate of 34%. Our experiences in coping with the previous coronavirus outbreaks have better equipped us to face the challenges posed by COVID-19, especially in the health care setting. Among the insights gained from the past outbreaks were: outbreaks caused by viruses are hazardous to healthcare workers; the impact of the disease extends beyond the infection; general principles of prevention and control are effective in containing the disease; the disease poses both a public health as well as an occupational health threat; and emerging infectious diseases pose a continuing threat to the world. Given the perspectives gained and lessons learnt from these past events, we should be better prepared to face the current COVID-19 outbreak.

Monoclonal antibodies for the S2 subunit of spike of SARS-CoV cross-react with the newly-emerged SARS-CoV-2

The emergence of a novel coronavirus, SARS-CoV-2, at the end of 2019 has resulted in widespread human infections across the globe. While genetically distinct from SARS-CoV, the etiological agent that caused an outbreak of severe acute respiratory syndrome (SARS) in 2003, both coronaviruses exhibit receptor binding domain (RBD) conservation and utilize the same host cell receptor, angiotensin-converting enzyme 2 (ACE2), for virus entry. Therefore, it will be important to test the cross-reactivity of antibodies that have been previously generated against the surface spike (S) glycoprotein of SARS-CoV in order to aid research on the newly emerged SARS-CoV-2. Here, we show that an immunogenic domain in the S2 subunit of SARS-CoV S is highly conserved in multiple strains of SARS-CoV-2. Consistently, four murine monoclonal antibodies (mAbs) raised against this immunogenic SARS-CoV fragment were able to recognise the S protein of SARS-CoV-2 expressed in a mammalian cell line. Importantly, one of them (mAb 1A9) was demonstrated to detect S in SARS-CoV-2-infected cells. To our knowledge, this is the first study showing that mAbs targeting the S2 domain of SARS-CoV can cross-react with SARS-CoV-2 and this observation is consistent with the high sequence conservation in the S2 subunit. These cross-reactive mAbs may serve as tools useful for SARS-CoV-2 research as well as for the development of diagnostic assays for its associated coronavirus disease COVID-19.

Neutralizing antibody and soluble ACE2 inhibition of a replication-competent VSV-SARS-CoV-2 and a clinical isolate of SARS-CoV-2

Antibody-based interventions against SARS-CoV-2 could limit morbidity, mortality, and possibly disrupt epidemic transmission. An anticipated correlate of such countermeasures is the level of neutralizing antibodies against the SARS-CoV-2 spike protein, yet there is no consensus as to which assay should be used for such measurements. Using an infectious molecular clone of vesicular stomatitis virus (VSV) that expresses eGFP as a marker of infection, we replaced the glycoprotein gene (G) with the spike protein of SARS-CoV-2 (VSV-eGFP-SARS-CoV-2) and developed a high-throughput imaging-based neutralization assay at biosafety level 2. We also developed a focus reduction neutralization test with a clinical isolate of SARS-CoV-2 at biosafety level 3. We compared the neutralizing activities of monoclonal and polyclonal antibody preparations, as well as ACE2-Fc soluble decoy protein in both assays and find an exceptionally high degree of concordance. The two assays will help define correlates of protection for antibody-based countermeasures including therapeutic antibodies, immune γ-globulin or plasma preparations, and vaccines against SARS-CoV-2. Replication-competent VSV-eGFP-SARS-CoV-2 provides a rapid assay for testing inhibitors of SARS-CoV-2 mediated entry that can be performed in 7.5 hours under reduced biosafety containment.

SARS-CoV-2 Spike protein variant D614G increases infectivity and retains sensitivity to antibodies that target the receptor binding domain

Virus genome sequence variants that appear over the course of an outbreak can be exploited to map the trajectory of the virus from one susceptible host to another. While such variants are usually of no functional significance, in some cases they may allow the virus to transmit faster, change disease severity, or confer resistance to antiviral therapies. Since the discovery of SARS-CoV-2 as the cause of COVID-19, the virus has spread around the globe, and thousands of SARS-CoV-2 genomes have been sequenced. The rate of sequence variation among SARS-CoV-2 isolates is modest for an RNA virus but the enormous number of human-to-human transmission events has provided abundant opportunity for selection of sequence variants. Among these, the SARS-CoV-2 Spike protein variant, D614G, was not present in the presumptive common ancestor of this zoonotic virus but was first detected in late January in Germany and China. The D614G variant steadily increased in frequency and now constitutes >97% of isolates world-wide, raising the question whether D614G confers a replication advantage to SARS-CoV-2. Structural models predict that D614G would disrupt contacts between the S1 and S2 domains of the Spike protein and cause significant shifts in conformation. Using single-cycle vectors we showed that D614G is three to nine-fold more infectious than the ancestral form on human lung and colon cell lines, as well as on other human cell lines rendered permissive by ectopic expression of human ACE2 and TMPRSS2, or by ACE2 orthologues from pangolin, pig, dog, or cat. Nonetheless, monoclonal antibodies targeting the receptor binding domain of the SARS-CoV-2 Spike protein retain full neutralization potency. These results suggest that D614G was selected for increased human-to-human transmission, that it contributed to the rapidity of SARS-CoV-2 spread around the world, and that it does not confer resistance to antiviral therapies targeting the receptor binding domain.

Antigenic evolution on global scale reveals potential natural selection of SARS-CoV-2 by pre-existing cross-reactive T cell immunity

The mutation pattern of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is constantly changing with the places of transmission, but the reason remains to be revealed. Here, we presented the study that comprehensively analyzed the potential selective pressure of immune system restriction, which can drive mutations in circulating SARS-CoV-2 isolates. The results showed that the most common mutation sites of SARS-CoV-2 proteins were located on the non-structural protein ORF1ab and the structural protein Spike. Further analysis revealed mutations in cross-reactive epitopes between SARS-CoV-2 and seasonal coronavirus may help SARS-CoV-2 to escape cellular immunity under the long-term and large-scale community transmission. Meanwhile, the mutations on Spike protein may enhance the ability of SARS-CoV-2 to enter the host cells and escape the recognition of B-cell immunity. This study will increase the understanding of the evolutionary direction and warn about the potential immune escape ability of SARS-CoV-2, which may provide important guidance for the potential vaccine design.

Comparative replication and immune activation profiles of SARS-CoV-2 and SARS-CoV in human lungs: an ex vivo study with implications for the pathogenesis of COVID-19

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an emerging coronavirus that has resulted in nearly 1,000,000 laboratory-confirmed cases including over 50,000 deaths. Although SARS-CoV-2 and SARS-CoV share a number of common clinical manifestations, SARS-CoV-2 appears to be highly efficient in person-to-person transmission and frequently cause asymptomatic infections. However, the underlying mechanism that confers these viral characteristics on high transmissibility and asymptomatic infection remain incompletely understood. METHODS: We comprehensively investigated the replication, cell tropism, and immune activation profile of SARS-CoV-2 infection in human lung tissues with SARS-CoV included as a comparison. RESULTS: SARS-CoV-2 infected and replicated in human lung tissues more efficiently than that of SARS-CoV. Within the 48-hour interval, SARS-CoV-2 generated 3.20 folds more infectious virus particles than that of SARS-CoV from the infected lung tissues (P<0.024). SARS-CoV-2 and SARS-CoV were similar in cell tropism, with both targeting types I and II pneumocytes, and alveolar macrophages. Importantly, despite the more efficient virus replication, SARS-CoV-2 did not significantly induce types I, II, or III interferons in the infected human lung tissues. In addition, while SARS-CoV infection upregulated the expression of 11 out of 13 (84.62%) representative pro-inflammatory cytokines/chemokines, SARS-CoV-2 infection only upregulated 5 of these 13 (38.46%) key inflammatory mediators despite replicating more efficiently. CONCLUSIONS: Our study provided the first quantitative data on the comparative replication capacity and immune activation profile of SARS-CoV-2 and SARS-CoV infection in human lung tissues. Our results provided important insights on the pathogenesis, high transmissibility, and asymptomatic infection of SARS-CoV-2.

Considerations around the SARS-CoV-2 Spike Protein with particular attention to COVID-19 brain infection and neurological symptoms

Identification of potential vaccine candidates against SARS-CoV-2, A step forward to fight novel coronavirus 2019-nCoV: A Reverse Vaccinology Approach

The recent Coronavirus Disease 2019 (COVID-19) causes an immense health crisis to global public health. The World Health Organization (WHO) declared the COVID-19 as a pandemic. The COVID-19 is the etiologic agent of a recently arose disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Presently, there is no vaccine available against this emerged viral disease. Therefore, it is indeed a need of the hour to develop an effectual and safe vaccine against this decidedly pandemic disease. In the current study, we collected SARS-CoV-2 genome from Indian geographical origin against human host, further more using reverse vaccinology and immunoinformatics tools here we claim effective vaccine candidates that can be mile stone in battle against COVID19. This novel study divulged two promising antigenic peptide GVYFASTEK and NFRVQPTESIV from surface glycoproteins (protein accession no. – QIA98583.1 and QHS34546.1) of SARS-CoV-2, which were predicated to be interacted with class I and class II MHC alleles and showed up to 90% conservancy and high value of antigenicity. Subsequently, the molecular docking studies were verified molecular interaction of these prime antigenic peptides with the residues of HLA-A*11-01 allele for MHC Class I and HLA DRB1*04-01 allele for MHC class II. After vigorous analysis, these peptides were predicted to be suitable epitopes which are capable to elicit the strong cell-mediated immune response against the SARS-CoV-2. Consequences from the present study could facilitate selecting SARS-CoV-2 epitopes for vaccine production pipelines in the immediate future. This novel research will certainly pave the way for a fast, reliable and virtuous platform to provide timely countermeasure of this dangerous pandemic disease, COVID-19.

SARS-CoV-2: A New Song Recalls an Old Melody

The viruses causing the SARS outbreak of 2002–2003 and current COVID-19 pandemic are related betacoronaviruses. What insights were learned from SARS that can inform SARS-CoV-2 vaccine development? Focusing on important lessons from SARS vaccine development and two SARS vaccines evaluated in humans may guide SARS-CoV-2 vaccine design, testing, and implementation.

Understanding the neurotropic characteristics of SARS-CoV-2: from neurological manifestations of COVID-19 to potential neurotropic mechanisms

Coronavirus disease 2019 (COVID-19), a disease caused by the novel betacoronavirus (SARS-CoV-2), has become a global pandemic threat. The potential involvement of COVID-19 in central nervous system (CNS) has attracted considerable attention due to neurological manifestations presented throughout the disease process. In addition, SARS-CoV-2 is structurally similar to SARS-CoV, and both bind to the angiotensin-converting enzyme 2 (ACE2) receptor to enter human cells. Thus, cells expressing ACE2, such as neurons and glial cells may act as targets and are thus vulnerable to SARS-CoV-2 infection. Here, we have reviewed the neurological characteristics of COVID-19 and summarized possible mechanisms of SARS-CoV-2 invasion of the CNS. COVID-19 patients have presented with a number of different neurological symptoms such as headache, dizziness, hyposmia, and hypogeusia during the course of illness. It has also been reported recently that some cases of COVID-19 have presented with concurrent acute cerebrovascular disease (acute ischemic stroke, cerebral venous sinus thrombosis, cerebral hemorrhage, subarachnoid hemorrhage), meningitis/encephalitis, acute necrotizing hemorrhagic encephalopathy, and acute Guillain-Barré syndrome. Furthermore, SARS-CoV-2 RNA detected in a cerebrospinal fluid specimen of a patient with COVID-19 have provided direct evidence to support the theory of neurotropic involvement of SARS-CoV-2. However, the underlying neurotropic mechanisms of SARS-CoV-2 are yet to be established. SARS-CoV-2 may affect CNS through two direct mechanisms (hematogenous dissemination or neuronal retrograde dissemination) or via indirect routes. The underlying mechanisms require further elucidation in the future.

Coronaviruses pandemics: Can neutralizing antibodies help?

For the first time in Homo sapiens history, possibly, most of human activities is stopped by coronavirus disease 2019 (COVID-19). Nearly eight billion people of this world are facing a great challenge, maybe not "to be or not to be" yet, but unpredictable. What happens to other major pandemics in the past, and how human beings went through these hurdles? The human body is equipped with the immune system that can recognize, respond and fight against pathogens such as viruses. Following the innate response, immune system processes the adaptive response by which each pathogen is encoded and recorded in memory system. The humoral reaction containing cytokines and antibodies is expected to activate when the pathogens come back. Exploiting this nature of body protection, neutralizing antibodies have been investigated. Learning from past, in parallel to SARS-CoV-2, other coronaviruses SARS-CoV and MERS-CoV who caused previous pandemics, are recalled in this review. We here propose insights of origin and characteristics and perspective for the future of antibodies development.

Pathways of cross-species transmission of synthetically reconstructed zoonotic severe acute respiratory syndrome coronavirus.

Zoonotic severe acute respiratory syndrome coronavirus (SARS-CoV) likely evolved to infect humans by a series of transmission events between humans and animals in markets in China. Virus sequence data suggest that the palm civet served as an amplification host in which civet and human interaction fostered the evolution of the epidemic SARS Urbani strain. The prototypic civet strain of SARS-CoV, SZ16, was isolated from a palm civet but has not been successfully cultured in vitro. To propagate a chimeric recombinant SARS-CoV bearing an SZ16 spike (S) glycoprotein (icSZ16-S), we constructed cell lines expressing the civet ortholog (DBT-cACE2) of the SARS-CoV receptor (hACE2). Zoonotic SARS-CoV was completely dependent on ACE2 for entry. Urbani grew with similar kinetics in both the DBT-cACE2 and the DBT-hACE2 cells, while icSZ16-S only grew in DBT-cACE2 cells. The SZ16-S mutant viruses adapted to human airway epithelial cells and displayed enhanced affinity for hACE2 but exhibited severe growth defects in the DBT-cACE2 cells, suggesting that the evolutionary pathway that promoted efficient hACE2 interactions simultaneously abolished efficient cACE2 interactions. Structural modeling predicted two distinct biochemical interaction networks by which zoonotic receptor binding domain architecture can productively engage hACE2, but only the Urbani mutational repertoire promoted efficient usage of both hACE2 and cACE2 binding interfaces. Since dual species tropism was preserved in Urbani, it is likely that the virus evolved a high affinity for cACE2/hACE2 receptors through adaptation via repeated passages between human and civet hosts. Furthermore, zoonotic SARS-CoV was variably neutralized by antibodies that were effective against the epidemic strain, highlighting their utility for evaluating passive immunization efficacy.

Retest positive for SARS-CoV-2 RNA of "recovered" patients with COVID-19: Persistence, sampling issues, or re-infection?

"Retest Positive" for severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) from "recovered" coronavirus disease-19 (COVID-19) has been reported and raised several important questions for this novel coronavirus and COVID-19 disease. In this commentary, we discussed several questions: (a) Can SARS-CoV-2 re-infect the individuals who recovered from COVID-19? This question is also associated with other questions: whether or not SARS-CoV-2 infection induces protective reaction or neutralized antibody? Will SARS-CoV-2 vaccines work? (b) Why could some recovered patients with COVID-19 be re-tested positive for SARS-CoV-2 RNA? (c) Are some recovered pwith atients COVID-19 with re-testing positive for SARS-CoV-2 RNA infectious? and (d) How should the COVID-19 patients with retest positive for SARS-CoV-2 be managed?

Coronavirus disease 2019 (COVID-19), a disease caused by the novel betacoronavirus (SARS-CoV-2), has become a global pandemic threat. The potential involvement of COVID-19 in central nervous system (CNS) has attracted considerable attention due to neurological manifestations presented throughout the disease process. In addition, SARS-CoV-2 is structurally similar to SARS-CoV, and both bind to the angiotensin-converting enzyme 2 (ACE2) receptor to enter human cells. Thus, cells expressing ACE2, such as neurons and glial cells may act as targets and are thus vulnerable to SARS-CoV-2 infection. Here, we have reviewed the neurological characteristics of COVID-19 and summarized possible mechanisms of SARS-CoV-2 invasion of the CNS. COVID-19 patients have presented with a number of different neurological symptoms such as headache, dizziness, hyposmia, and hypogeusia during the course of illness. It has also been reported recently that some cases of COVID-19 have presented with concurrent acute cerebrovascular disease (acute ischemic stroke, cerebral venous sinus thrombosis, cerebral hemorrhage, subarachnoid hemorrhage), meningitis/encephalitis, acute necrotizing hemorrhagic encephalopathy, and acute Guillain–Barré syndrome. Furthermore, SARS-CoV-2 RNA detected in a cerebrospinal fluid specimen of a patient with COVID-19 have provided direct evidence to support the theory of neurotropic involvement of SARS-CoV-2. However, the underlying neurotropic mechanisms of SARS-CoV-2 are yet to be established. SARS-CoV-2 may affect CNS through two direct mechanisms (hematogenous dissemination or neuronal retrograde dissemination) or via indirect routes. The underlying mechanisms require further elucidation in the future.

SARS

Abstract Severe acute respiratory syndrome (SARS) emerged in southern China in late 2002. It first spread within Guangdong Province and then to other parts of China. Via air travelers, it quickly reached various countries around the globe, causing several major hospital outbreaks. Within weeks, the causative agent, a previously unknown coronavirus (SARS-CoV), was identified, thanks to an unprecedented international effort led by the World Health Organization (WHO). Its origin was quickly traced to wild animals traded locally for culinary purposes. Masked palm civet and some other species seem to have acted as intermediate hosts. Since then, SARS-like coronaviruses were found in different bat species in China and elsewhere, and bats are now regarded as the wildlife reservoir for SARS-CoV. Fortunately, the SARS outbreak could be contained within months. Until July 2003, it had caused 8096 cases, with 774 deaths. Once adequate measures such as isolating patients and quarantining their contacts were strictly adhered to, further transmission between human beings could be interrupted. SARS is an example of how rapidly an infectious agent can spread in the modern world. At the same time, it should serve as a showcase of how international cooperation and modern science can help to combat the spread of infectious diseases.

The «moonlighting protein» able to explain the T(h)1 immune lockdown in severe COVID-19()

COVID-19 is a major public health issue around the world and new data about its etiological agent, SARS-CoV-2, are urgently necessary, also translating the scientific knowledge acquired on its more similar predecessors, SARS-CoV-1 and MERS-CoV, the coronaviruses responsible for SARS and MERS, respectively. Like SARS-CoV-1, SARS-CoV-2 exploits the ACE2 receptors to enter the host cells; nevertheless, recent bioinformatics insights suggest a potential interaction of SARS-CoV-2 with the «moonlighting protein» CD26/DPP4, exactly how MERS-CoV works. CD26/DPP4 is overexpressed on T-helper type 1 (T(h)1) cells and its expression increases with aging, all factors which could well explain the T(h)1 immune lockdown, especially in the elderly, during fatal SARS-CoV-2 infections. Facing with this scenario, it is possible that T(h)1 and T-cytotoxic lymphocytes are the immune cells most affected by SARS-CoV-2, and that the immune system is forced to mount a T-helper type 2 (T(h)2) response, the only one still mountable, in the attempt to counteract the viral load. However, in this way, the symptomatic patient experiences all the negative effects of the T(h)2 response, which can seriously aggravate the clinical picture.

Structural basis for neutralization of SARS-CoV-2 and SARS-CoV by a potent therapeutic antibody

The COVID-19 pandemic caused by the SARS-CoV-2 virus has resulted in an unprecedented public health crisis. There are no approved vaccines or therapeutics for treating COVID-19. Here we reported a humanized monoclonal antibody, H014, efficiently neutralizes SARS-CoV-2 and SARS-CoV pseudoviruses as well as authentic SARS-CoV-2 at nM level by engaging the S receptor binding domain (RBD). Importantly, H014 administration reduced SARS-CoV-2 titers in the infected lungs and prevented pulmonary pathology in hACE2 mouse model. Cryo-EM characterization of the SARS-CoV-2 S trimer in complex with the H014 Fab fragment unveiled a novel conformational epitope, which is only accessible when the RBD is in open conformation. Biochemical, cellular, virological and structural studies demonstrated that H014 prevents attachment of SARS-CoV-2 to its host cell receptors. Epitope analysis of available neutralizing antibodies against SARS-CoV and SARS-CoV-2 uncover broad cross-protective epitopes. Our results highlight a key role for antibody-based therapeutic interventions in the treatment of COVID-19. One sentence summary A potent neutralizing antibody conferred protection against SARS-CoV-2 in an hACE2 humanized mouse model by sterically blocking the interaction of the virus with its receptor.

Temporal Correlation Between Neurological and Gastrointestinal Symptoms of SARS-CoV-2

Severe Acute Respiratory Syndrome Coronavirus-2 (SAR-CoV-2) has been shown to invade brain tissue. Based on the evolutionary similarity with SARS-CoV, researchers propose that SARS-CoV-2 can invade the olfactory bulb and gastrointestinal (GI) system through angiotensin-converting enzyme 2. However, how SARS-CoV-2 causes neurological or GI symptoms is not clear. Many suggested intestinal and neural inflammations, caused by viral invasion, as the most likely reason for the GI and neurological symptoms; however, the patients with coronavirus disease 2019 (COVID-19) without neurological or GI symptoms indicate that this is not the case. The gut-brain axis could explain the reason for why some with COVID-19 do not have these symptoms. COVID-19 patients mostly show respiratory distress first, then diarrhea, anorexia, stroke, or loss of consciousness comes into view. Obviously, GI invasion is a mechanical process that begins with oral invasion and, therefore, most probably exists before the brain invasion, as indicated in case reports. However, when the GI tract is invaded, the virus may enter the central nervous system through vascular and lymphatic systems or the vagal nerve. SARS-CoV-2 can infect leukocytes and migrate with them into the brain, or the viral particles can be directly transported across the blood-brain barrier to the brain. Also, more recent research has revealed that SARS-CoV-2 can invade the peripheral lymphatic vessels connecting with the glymphatic system of the brain. The temporal correlation between neurological and gastrointestinal symptoms suggests the lymph vessels around the GI tract, the vascular system, or the gut-brain axis (enteric nervous system) as the most likely entry route for SARS-CoV-2 to the brain.

Sofosbuvir protects human brain organoids against SARS-CoV-2

COVID-19 was rapidly declared a pandemic by the World Health Organization, only three months after the initial outbreak in Wuhan, China. Early clinical care mainly focused on respiratory illnesses. However, a variety of neurological manifestations in both adults and newborns are also emerging. To determine whether SARS-CoV-2 could target the human brain, we infected iPSC-derived human brain organoids. Our findings show that SARS-CoV-2 was able to infect and kill neural cells, including cortical neurons. This phenotype was accompanied by impaired synaptogenesis. Finally, Sofosbuvir, an FDA-approved antiviral drug, was able to rescue these alterations. Given that there are currently no vaccine or antiviral treatments available, urgent therapies are needed. Our findings put Sofosbuvir forward as a potential treatment to alleviate COVID-19-related neurological symptoms. One Sentence Summary SARS-CoV-2 infection causes neuronal death and impaired synaptogenesis, both rescued by Sofosbuvir treatment.

Multi-epitope-based peptide vaccine design against SARS-CoV-2 using its spike protein

SARS CoV-2 has particularly been efficient in ensuring that many countries are brought to a standstill. With repercussions ranging from rampant mortality, fear, paranoia and economic recession, the virus has brought together countries in order to look at possible therapeutic countermeasures. With prophylactic interventions possibly months away from being particularly effective, a slew of measures and possibilities concerning the design of vaccines are being worked upon. We attempted a structure-based approach utilizing a combination of epitope prediction servers to develop a multi-epitope-based subunit vaccine that involves the two major domains of the spike glycoprotein of SARS CoV-2 (S1 and S2) coupled with a substantially effective chimeric adjuvant to create stable vaccine constructs through MD simulations. The designed constructs were evaluated based on their docking with Toll Like Receptor (TLR) 4. Our findings provide an epitope-based peptide fragment; which can be a potential candidate for the development of a vaccine against SARS-CoV-2. Recent experimental studies based on determining immunodominant regions across the spike glycoprotein of SARS-CoV-2 indicate the presence of the predicted epitopes included in this study.

Implications of SARS-CoV-2 Genetic Diversity and Mutations on Pathogenicity of COVID-19 and Biomedical Interventions

ABSTRACT Objective Coronavirus disease 2019 (COVID-19) has caused an unprecedented global health emergency. The COVID-19 pandemic has claimed over 350,000 human lives within five months of its emergence, especially in the USA and the European continent. This study analysed the implications of the genetic diversity and mutations in SARS-CoV-2 on its virulence diversity and investigated how these factors could affect the successful development and application of antiviral chemotherapy, immunotherapy, serodiagnosis, and vaccination. Methods All the suitable and eligible full text articles published between 31st December 2019 and 31st May 2020 were filtered and extracted from “PubMed”, “Scopus”, “Web of Science”, and “Hinari” and were critically reviewed. We used the Medical Subject Headings (MeSH) terms “COVID-19, “Mutation”, “Genetic diversity”, “SARS-CoV-2”, “Virulence”, “Pathogenicity”, “Evolution” and “SARS-CoV-2 transmission” for this search. Results Our search showed that SARS-CoV-2 has persistently undergone significant mutations in various parts of its non-structural proteins (NSPs), including NSP2 and NSP3, S protein, and RNA-dependent RNA polymerase (RdRp). In particular, the S protein was found to be the key determinant of evolution, transmission, and virulence of SARS-CoV-2, and could be a potential target for vaccine development. Additionally, RdRp could be a major target in the development of antivirals for the treatment of COVID-19. Conclusion Given the critical importance of mutations in the pathogenicity of SARS-CoV-2 and in the development of sero-diagnostics, antivirals, and vaccines, this study recommends continuous molecular surveillance of SARS-CoV-2. This approach would potentially prompt identification of new mutants and their impact on ongoing biomedical interventions and COVID-19 control measures.

Binding Ability Prediction between Spike Protein and Human ACE2 Reveals the Adaptive Strategy of SARS-CoV-2 in Humans

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is a novel coronavirus causing an outbreak of COVID-19 globally in the past six months. A relatively higher divergence on the spike protein of SASR-CoV-2 enables it to transmit across species efficiently. We particularly believe that the adaptive mutations of the receptor-binding domain (RBD) of spike protein in SARS-CoV-2 might be essential to its high transmissibility among humans. Thus here we collected 2,142 high-quality genome sequences of SARS-CoV-2 from 160 regions in over 50 countries and reconstructed their phylogeny, and also analyzed the interaction between the polymorphisms of spike protein and human ACE2 (hACE2). Phylogenetic analysis of SARS-CoV-2 and coronavirus in other hosts show SARS-CoV-2 is highly possible originated from Bat-CoV (RaTG13) found in horseshoe bat and a recombination event may occur on the spike protein of Pangolin-CoV to imbue it the ability to infect humans. Moreover, compared to the S gene of SARS-CoV-2, it is more conserved in the direct-binding sites of RBD and we noticed that spike protein of SARS-CoV-2 may under a consensus evolution to adapt to human hosts better. 3,860 amino acid mutations in spike protein RBD (T333-C525) of SARS-CoV-2 were simulated and their stability and affinity binding to hACE2 (S19-D615) were calculated. Our analysis indicates SARS-CoV-2 could infect humans from different populations with no preference, and a higher divergence in the spike protein of SARS-CoV-2 at the early stage of this pandemic may be a good indicator that could show the pathway of SARS-CoV-2 transmitting from the natural reservoir to human beings.

Developing a SARS-CoV-2 Vaccine at Warp Speed

Does COVID19 Infect the Brain? If So, Smokers Might Be at a Higher Risk

COVID19 is a devastating global pandemic with epicenters in China, Italy, Spain, and now the United States. While the majority of infected cases appear mild, in some cases, individuals present serious cardiorespiratory complications with possible long-term lung damage. Infected individuals report a range of symptoms from headaches to shortness of breath to taste and smell loss. To that end, less is known about how the virus may impact different organ systems. The SARS-CoV2 virus, which is responsible for COVID19, is highly similar to SARS-CoV. Both viruses have evolved an ability to enter host cells through direct interaction with the angiotensin converting enzyme (ACE) 2 protein at the surface of many cells. Published findings indicate that SARS-CoV can enter the human nervous system with evidence from both postmortem brains and detection in cerebrospinal fluid of infected individuals. Here, we consider the ability of SARS-CoV2 to enter and infect the human nervous system based on the strong expression of the ACE2 target throughout the brain. Moreover, we predict that nicotine exposure through various kinds of smoking (cigarettes, electronic cigarettes, or vape) can increase the risk for COVID19 neuroinfection based on known functional interactions between the nicotinic receptor and ACE2. We advocate for higher surveillance and analysis of neurocomplications in infected cases. SIGNIFICANCE STATEMENT: The COVID19 epidemic has spurred a global public health crisis. While many of the cases requiring hospitalization and intensive medical care center on cardiorespiratory treatment, a growing number of cases present neurological symptoms. Viral entry into the brain now appears a strong possibility with deleterious consequences and an urgent need for addressing.