The immune response to viral infection comprises innate and adaptive defenses. The innate response, which we have discussed previously, functions continuously in a normal host without exposure to any virus. Most viral infections are controlled by the innate immune system. However, if viral replication outpaces innate defenses, the adaptive response must be mobilized. The adaptive …
During the earliest stages of a virus infection, cytokines are produced when innate immune defenses are activated. The rapid release of cytokines at the site of infection initiates new responses with far-reaching consequences that include inflammation. One of the earliest cytokines produced is tumor necrosis factor alpha (TNF-α), which is synthesized by activated monocytes and …
Mutation is an important source of RNA virus diversity that is made possible by the error-prone nature of RNA synthesis. Viruses with segmented genomes, such as influenza virus, have another mechanism for generating diversity: reassortment. When an influenza virus infects a cell, the individual RNA segments enter the nucleus. There they are copied many times …
The RNA genome of influenza viruses is segmented . The virions of influenza A and B viruses contain 8 different RNAs, while those of influenza C viruses contain 7. How is the correct number of RNA segments inserted into newly synthesized virus particles? During influenza virus assembly, viral RNAs and viral proteins €“ called a …
Soon after the new influenza H1N1 strain emerged in April 2009, I began a series of blog posts on basic aspects of influenza virus replication and pathogenesis. The goal of this series is to provide information that will allow everyone to better understand the events surrounding emergence and spread of the new pandemic strain. Unfortunately …
The influenza virus hemagglutinin (HA) is the viral protein that attaches to cell receptors. The HA also plays an important role in the release of the viral RNA into the cell, by causing fusion of viral and cellular membranes. HA must be cleaved by cellular proteases to be active as a fusion protein. The HA …
Influenza HA cleavage is required for infectivity Read More »
