Immunochemistry of variants of influenza virus hemagglutinin and neuraminidase.

Influenza is impossible to control by vaccination because of variation in the two surface antigens of the virus, the hemagglutinin (HA) and neuraminidase (NA). This variation is caused by sequence changes in the genes coding these antigens and this article summarizes recent information on the structure of the HA and NA, the way in which these glycoproteins vary and the effects of the changes on the antigenic properties of the virus.