Functional equivalency of B7-1 and B7-2 for costimulating plasmid DNA vaccine-elicited CTL responses

A costimulatory signal in addition to an Ag-specific stimulus is required f or optimal activation of T lymphocytes, CD28, the primary positive costimul atory receptor on T cells, has two identified ligands, B7-1 and B7-2, Wheth er B7-1 and B7-2 have identical, overlapping, or distinct functions remains unresolved. In this study, we show that mice lacking B7-2 were unable to g enerate CTL responses following immunization with a plasmid DNA vaccine. Th e ability of these B7-2-deficient mice to generate CTL responses following plasmid gp120 DNA vaccination was fully reconstituted by coadministering ei ther a plasmid expressing B7-2 or B7-1, Moreover, the ability to generate C TL responses following plasmid DNA vaccination in mice lacking both B7-1 an d B7-2 could be reconstituted by administering either plasmid B7-1 or plasm id B7-2 with the vaccine construct. These data demonstrate that either B7-1 or B7-2 administered concurrently with a plasmid DNA vaccine can fully cos timulate vaccine-elicited CTL responses, Functional differences between B7- 1 and B7-2 observed in vivo therefore may not reflect inherent differences in the interactions of CD28 with these ligands.