B7 co-stimulatory requirements differ for induction of immune responses byDNA, protein and recombinant pox virus vaccination

Whether B7-1 and B7-2 have distinct functions for eliciting immune response s to antigens that are presented to the immune system by intracellular and extracellular antigen processing pathways is an unresolved question. To inv estigate this issue we compared the humoral and cellular immune responses e licited by immunizing wild-type, B7-1(-/-) and B7-2(-/-) mice with either H IV-1 gp120 plasmid DNA, recombinant gp120 protein or vaccinia virus express ing gp120. The generation of both humoral and cellular immune responses to an antigen produced intracellularly following DNA vaccination had critical requirements for B7-2, but not B7-1. Neither of the molecules was essential for the generation of antibody responses to an extracellular protein antig en administered with adjuvant; B7-1 had little effect on the elicited immun e responses. When recombinant vaccinia virus was used to present antigen in tracellularly in the context of a viral infection, B7-2 was absolutely requ ired for antibody and T cell proliferative responses, but it exerted a supp ressive effect on the elicited CTL activity. These results demonstrate that antigens presented to the immune system by different mechanisms have disti nct B7-1 and B7-2 co-stimulatory requirements.