Bacterial antigenic variation, host immune response, and pathogen-host coevolution.

Many bacterial pathogens are exquisitely adapted to host parasitization. Their niche is primarily determined by the biochemical milieu of the host. As such, pathogens are selected to exhibit environmentally responsive and adaptive molecular traits which allow adherence, entrance, and replication within the host (7, 26). One major set of selective forces which operates to shape the phenotype of the bacterial pathogen is the host immune system. The host immune response following contact with the pathogen is itself adaptive and seeks to eliminate or restrict bacterial replication. Thus, successful bacterial pathogens must be able to avoid