Antigenic variation

Antigenic variation is the process by which an infectious organism alters its surface proteins in order to evade a host immune response. This change in antigenic profile may occur as the pathogen passes through a host population (also called "antigenic diversity") or may take place in the originally infected host. The strategy is particularly important for organisms that target long-lived hosts, repeatedly infect a single host, and are easily transmitted. Pathogens that express these characteristics and undergo antigenic variation have a selective advantage over their more genetically stable counterparts.

Antigenic variation can occur through three broadly defined genetic processes: gene mutation, recombination, and switching. In all cases, antigenic variation results in pathogens that are immunologically distinct from the parental strains.

One possible consequence of antigenic variation is antigenic escape.