Antigenic variation and the structure of influenza virus glycoproteins.

Influenza is impossible to control by vaccination because of variation in the two surface antigens of the virus, the haemagglutinin (HA) and neuraminidase (NA). This variation is caused by sequence changes in the genes coding these antigens and this review 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.