Antigenicity and Antigenic Variation

A viral antigen elicits a host immune response, in which antibodies develop and recognize antigenic sites with high specificity. These antigenic sites define the virus antigenicity and generally reside on the outer capsid proteins for non-enveloped viruses and on the surface-exposed glycoproteins for enveloped viruses. Neutralizing antibodies drive antigenic variation in these sites, and this can be related to the nature of the amino acid substitution in the site. Antigenic variation is closely monitored for major pathogenic viruses (e.g., influenza virus and enteroviruses) circulating in endemic regions, for the effect it will have on vaccine choices. Understanding antigenicity and associated antigenic change is therefore instructive for the development of vaccines and anti-viral therapeutics.