Prime-boost immunization strategies for infectious diseases.

New vaccination strategies that induce the cellular arm of the immune response are needed for the development of effective prophylactic and therapeutic vaccines against a number of intracellular pathogens. DNA vaccines, recombinant viral vectors and recombinant proteins are all effective antigen delivery systems for inducing cellular immunity; however, when used alone, the levels of specific responses they induce are low. Prime-boost immunization strategies involve using two different vaccines, each encoding the same antigen, some weeks apart. Such strategies have been shown to enhance cellular immunity in several different animal and disease models.