For mammalian influenza viruses and low pathogenic AIVs, cleavage is extracellular, which limits infection to cells that have the appropriate proteases, whereas for highly pathogenic AIVs, cleavage is intracellular and performed by ubiquitous proteases, which allows for infection of a greater variety of cells, thereby contributing to more severe disease. Immunology
Cells possess sensors to detect viral RNA, which can then induce interferon production. Interferons mediate expression of antiviral proteins and proteins that recruit immune cells to the infection site, and they also notify nearby uninfected cells of infection. Some infected cells release pro-inflammatory cytokines that recruit immune cells to the site of infection. Immune cells control viral infection by killing infected cells and phagocytizing viral particles and apoptotic cells. An exacerbated immune response, however, can harm the host organism through a cytokine storm. To counter the immune response, influenza viruses encode various non-structural proteins, including NS1, NEP, PB1-F2, and PA-X, that are involved in curtailing the host immune response by suppressing interferon production and host gene expression.B cells, a type of white blood cell, produce antibodies that bind to influenza antigens HA and NA (or HEF) and other proteins to a lesser degree. Once bound to these proteins, antibodies block virions from binding to cellular receptors, neutralizing the virus. In humans, a sizeable antibody response occurs ~1 week after viral exposure. This antibody response is typically robust and long-lasting, especially for ICV and IDV.
Ingenol mebutate, sold under the brand name Picato, is a substance that is found in the sap of the plant Euphorbia peplus, commonly known as milkweed, and is an inducer of cell death. A gel formulation of the drug has been approved by the U.S. Food and Drug Administration (FDA) and by the European Medicines Agency (EMA) for the topical treatment of actinic keratosis. Two different strengths of the gel have been approved for use on either the face and scalp (0.015%) or the trunk and extremities (0.05%), respectively. In 2020 the drug was withdrawn from the market in the EU. Adverse effects
Irritation of the application site is very common. The various types of irritation include redness, scaling, crusting, pain, severe itching, and sometimes infection. Additional possible side effects include eye irritation, such as periorbital edema (3% of patients in studies), headaches (2%) and nasopharyngitis (running nose, 2%).Allergic reactions, shingles, changes in pigmentation at application site, chemical conjunctivitis, and corneal burns may also occur.The European Medicines Agency recommended suspending the marketing authorisation of ingenol mebutate due to concerns regarding increased incidence of skin cancer in patients treated with topical ingenol mebutate compared to vehicle or imiquimod. Physicians were advised to refrain from prescribing ingenol and to use different treatment options. Subsequently, the marketing authorization holder requested withdrawal of the manufacturing authorization for commercial reasons. The withdrawal was granted and therefore, ingenol mebutate is no longer registered in the EU.