Phase and antigenic variation--the impact on strategies for bacterial vaccine design

Many pathogens have the ability to vary the antigenic composition of surface-associated antigens. Often, this variation is mediated by the regulation of gene expression. By varying its antigenicity, the pathogen is able to avoid host immune responses more efficiently; however, this makes the design of vaccines against pathogens that exhibit antigenic variation difficult. In this review, we use the pathogenic Neisseria as an example of antigenically variable bacteria and discuss some attempts to overcome the problems of vaccine design posed by such organisms.