A prime-boost regime that combines Montanide ISA720 and Alhydrogel to induce antibodies against the HIV-1 derived multiepitope polypeptide TAB9.

A phase I clinical trial with the HIV-1-derived multi-epitope polypeptide (MEP) TAB9 in the oil adjuvant Montanide ISA720 (M-ISA720) was recently performed. Although severe local reactions were reported after the second and third injections of this vaccine candidate, the first inoculation was well tolerated. In this article we evaluated a prime-boost regime consisting of one inoculation of TAB9 in M-ISA720 followed by a booster with the same antigen in aluminum hydroxide. This combination of adjuvants elicited similar antibody levels in rabbits than the traditional two-dose schedule with M-ISA720. A control group injected three times with TAB9 in aluminum hydroxide developed markedly lower antibody titers. These results showed that although oil adjuvants are better than alum for priming the immune system for antibody production against TAB9, both kinds of adjuvants can be equally effective in booster immunizations. Therefore, by using the more reactogenic oil adjuvant only for priming, we should be able to eliminate the undesirable reactions characteristic of these compounds while achieving equivalent levels of specific antibodies.