LONG-TERM PROTECTION OF CHIMPANZEES AGAINST HIGH-DOSE HIV-1 CHALLENGEINDUCED BY IMMUNIZATION

A combination AIDS vaccine approach consisting of priming with adenovi rus-HIV-1(MN)gp160 recombinants followed by boosting with HIV-1(SF2)gp 120 was evaluated in chimpanzees. Long-lasting protection, requiring o nly three immunizations, was achieved against a low-dose challenge wit h the SF2 strain of HIV-1 and a subsequent high-dose SF2 challenge adm inistered 1 year later without an intervening boost. Notably, neutrali zing antibody responses against both clinical and laboratory isolates developed in three chimpanzees and persisted until the time of high-do se challenge. The possibility that cytotoxic T-lymphocytes contribute to row-dose protection of a chimpanzee lacking neutralizing antibodies is suggested. Our results validate the live vector priming/subunit bo oster approach and should stimulate interest in assessing this combina tion vaccine approach in humans.