A recombinant human immunodeficiency virus 1 IIIB (HIV-1IIIB) gp120 subunit vaccine (IIIB-rgp120/HIV-1, Genentech) was tested for safety and immunogenicity in a randomised, double-blind, placebo-controlled phase-I trial. HIV-1- seronegative adult volunteers received three 100 μg or 300 μg doses of IIIB-rgp120/HIV-1 in alum adjuvant (10 vaccinees in each group), or alum adjuvant alone (8 vaccinees), at 0, 4, and 32 weeks by intramuscular injection. The three injections were well tolerated in both vaccine groups. Antibodies that neutralised homologous HIV-1IIIB were induced in 9 of 10 recipients after three 300 μg doses, and 6 of these 9 sera also neutralised heterologous HIV-1SF2. A dose response was evident, since three 100 μg injections induced lower titres of HIV-1IIIB neutralising antibodies and in fewer recipients (5 of 9) than the higher dose, with no neutralisation of HIV-1SF2. Similarly, syncytia-inhibiting, CD4-rgp120- blocking, and HIV-1IIIB V3-binding antibodies were induced in a dose dependent manner. Response to the 300 μg per dose vaccination occurred in a larger proportion of volunteers and at higher mean titres than seen in previous human trials with other recombinant envelope subunit vaccines or live vaccinia-env priming followed by envelope subunit boosting.
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