544. Strong, Long-Lasting Immune Responses Against Lentivirus Antigens Using rSV40 Vectors Carrying HIV Tat and Envelope

Abstract

Background: Analysis of blood and cells from HIV-positive patients has demonstrated specific cytotoxic T cells and antibodies directed vs. most HIV proteins. These findings suggest that even proteins that are predicted to be sub-dominant epitopes, can be targeted by the immune system. Thus, just as it is unclear what form(s) an effective prophylactic or therapeutic immune response against HIV might take, the critical antigenic targets are also unknown. A promising approach to HIV vaccine development is use of live viral vectors to deliver HIV antigens in vivo. However, this approach has been hampered by the inability to reinoculate any individual vector more than once: thus one cannot both prime and boost responses using the same vector. Uniquely, recombinant SV40 vectors (rSV40s) circumvent this limitation: they do not elicit neutralizing responses against themselves. rSV40s thus may be administered multiple times. We tested the ability of two rSV40s bearing HIVNL4-3 antigens to prime and boost immune responses: SV(gp120), carrying the cDNA for HIV Env gp120, and SV(Tat) which bears the coding sequences for Tat. Most importantly, the longevity of these immune responses, particularly cytotoxic lymphocyte responses, was assessed.