Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), also known by their taxonomical names Human alphaherpesvirus 1 and Human alphaherpesvirus 2, are two members of the human Herpesviridae family, a set of viruses that produce viral infections in the majority of humans. Both HSV-1 and HSV-2 are very common and contagious. They can be spread when an infected person begins shedding the virus. As of 2016, about 67% of the world population under the age of 50 had HSV-1. In the United States, about 47.8% and 11.9% are estimated to have HSV-1 and HSV-2, respectively, though actual prevalence may be much higher. Because it can be transmitted through any intimate contact, it is one of the most common sexually transmitted infections. Symptoms
Many of those who are infected never develop symptoms. Symptoms, when they occur, may include watery blisters in the skin or mucous membranes of the mouth, lips, nose, genitals, or eyes (herpes simplex keratitis). Lesions heal with a scab characteristic of herpetic disease. Sometimes, the viruses cause mild or atypical symptoms during outbreaks. However, they can also cause more troublesome forms of herpes simplex. As neurotropic and neuroinvasive viruses, HSV-1 and -2 persist in the body by hiding from the immune system in the cell bodies of neurons, particularly in sensory ganglia. After the initial or primary infection, some infected people experience sporadic episodes of viral reactivation or outbreaks.
two or more viruses per host cell), MR is observed. Enhanced survival of HSV-1 due to MR occurs upon exposure to different DNA damaging agents, including methyl methanesulfonate, trimethylpsoralen (which causes inter-strand DNA cross-links), and UV light. After treatment of genetically marked HSV with trimethylpsoralen, recombination between the marked viruses increases, suggesting that trimethylpsoralen damage stimulates recombination. MR of HSV appears to partially depend on the host cell recombinational repair machinery since skin fibroblast cells defective in a component of this machinery (i.e. cells from Blooms syndrome patients) are deficient in MR.These observations suggest that MR in HSV infections involves genetic recombination between damaged viral genomes resulting in production of viable progeny viruses. HSV-1, upon infecting host cells, induces inflammation and oxidative stress. Thus it appears that the HSV genome may be subjected to oxidative DNA damage during infection, and that MR may enhance viral survival and virulence under these conditions. Use as an anti-cancer agent
Modified Herpes simplex virus is considered as a potential therapy for cancer and has been extensively clinically tested to assess its oncolytic (cancer killing) ability. Interim overall survival data from Amgens phase 3 trial of a genetically attenuated herpes virus suggests efficacy against melanoma. Use in neuronal connection tracing
Herpes simplex virus is also used as a transneuronal tracer defining connections among neurons by virtue of traversing synapses. Other related outcomes
HSV-2 the most common cause of Mollarets meningitis. HSV-1 can lead to potentially fatal cases of herpes simplex encephalitis.