Influenza A virus - A model for viral antigen presentation to cytotoxic T lymphocytes

Human influenza A virus is characterized by its high degree of variability and by its ability to cause frequent epidemics of disease. Most of the variation occurs in the two surface glycoproteins of the virus, against which protective antibodies are directed. In contrast, the strong MHC class I-restricted CTL response to infection with virus is predominantly specific for internal viral proteins which are relatively well conserved, and is cross-reactive between different strains of influenza A virus. However, the natural evolution of influenza viruses is largely driven by selection with antibody, with no firm evidence of selection by CTL. In normal individuals influenza virus produces an acute, localized infection, and this in part may reflect an inability to escape the CTL response.