6th International AIDS Conference San Francisco, California, USA — June 20-23, 1990

Int Conf AIDS 1990 Jun 20-23; 6:340 (abstract no. 1107)
Montefiori DC, Graham B, Robinson WE Jr, Wright P; Departments of Pathology and Medicine, Vanderbilt University Medical School, Nashville, TN, USA

OBJECTIVE: To assess functional immune responses to a fourth administration of an HIV-1 gp160 vaccine in normal volunteers.

METHODS: In a multicenter randomized, double-blind study, healthy adult volunteers received 40 ug or 80 ug of a baculovirus-derived, recombinant HIV-1 gp160 (rgp160) vaccine (MicroGeneSys) on days 0, 30, 180 and 544. A control set of subjects received placebo or hepatitis B vaccine. Neutralizing (NT) and complement-mediated, infection-enhancing antibody (C'-ADE) titers were measured in an MT-2 cell cytopathic infection assay. Antibody responses were also assessed by Western immunoblot.

RESULTS: Sera from day 559, 2 weeks after the fourth dose, were tested from 14 vaccinees. NT antibodies were found in 2/8 subjects at the 40 ug dose, and in 2/6 subjects at the 80 ug dose. NT titers were moderately higher in the 80 ug group. C'-ADE was only detected in the two individuals with NT antibodies at the 80 ug dose. Titers of C'-ADE activity were lower than NT antibody titers. No NT or C'-ADE antibodies were detected in the control groups. Functional antibodies correlated with gp160, gp120 and gp41 immunoblot reactivities.

CONCLUSIONS: The MicroGeneSys rgp160 vaccine candidate can elicit antibody responses in humans at 40 ug and 80 ug doses that have functional activity in vitro. A long interval between boosts enhances antibody response.

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