Safety and immunogenicity of a candidate HIV-1 vaccine in healthy adults: Recombinant glycoprotein (rgp) 120 - A randomized, double-blind trial

Objective: To evaluate the safety and immunogenicity of recombinant glycoprotein (rgp) 120, a candidate vaccine for the human immunodeficiency virus (HIV), formulated with a novel adjuvant, MF59, with or without a biological response modifier, MTP-PE. Design: Multicenter, double-blind, randomized trial. Setting: University medical centers. Participants: 49 healthy, HIV-seronegative volunteers 18 to 60 years of age who were at low risk for HIV type 1 (HIV-1) infection. Interventions: In part A of the study, 32 participants were randomly assigned to receive either 15 mu g of rgp120 in MF59, 15 mu g of rgp120 in MF59 plus 50 mu g of MTP-PE, 50 mu g of rgp120 in MF59, or 50 mu g of rgp120 in MF59 plus 50 mu g of MTP-PE. Participants were vaccinated at 0, 1, 6, and 12 to 18 months. In part B, 17 participants were randomly assigned to receive five monthly injections of either 50 mu g of rgp120 in MF59 or MF59 alone followed by a booster injection at 12 to 18 months. Main Outcome Measures: Local and systemic reactions; laboratory measures of hepatic renal, immunologic, and bone marrow toxicity; and HIV-specific serologic and cell-mediated immune responses. Results: 13 patients in part A received 50-mu g doses of rgp120; type-specific neutralizing antibody responses against the SF-2 strain of HIV-1 (HIV-1/SF-2) were induced in ail 13, Nine of the 13 had crossreactive neutralizing activity against the MN strain of HIV-1 (HIV-1/MN), and 2 had crossreactive neutralizing activity against the IIIB strain of HIV-1 (HIV-1/IIIB). Twelve patients had type-specific fusion inhibition activity; only 1 had crossreactive fusion inhibition activity against HIV-1/MN. The monthly vaccination schedule used in part B resulted in decreased antibody titers, indicating that a rest period in the schedule is necessary for maximal immunogenicity, Lymphoproliferative responses against gp120 were induced in all vaccine recipients, The stimulation index to gp120 was persistently greater than 15 for 6 months after the last booster vaccination was given. CD8(+) cytotoxic T-lymphocyte activity was detected in 1 of the 11 participants tested. Vaccine that contained MTP-PE caused a greater number of moderate or severe local and systemic reactions (of 16 participants, 4 had local reactions and 13 had systemic reactions) than did vaccine formulated with MF59 alone (of 16 participants, 7 had local reactions [P <0.01] and 0 had systemic reactions [P < 0.001]). Conclusions: The SF-2 rgp120 vaccine is safe and immunogenic. Three vaccinations with rgp120 in MF59 can induce type-specific and crossreactive neutralizing antibody against B-subtype laboratory strains of HIV-1. Human immunodeficiency virus-specific lymphoproliferative responses were induced in all vaccinated participants, and CD8(+) cytotoxic T-lymphocyte activity was shown in one participant. A trend toward the augmentation of lymphoproliferative and humoral responses by MTP-PE was seen in the participants receiving 15 mu g of rgp120. However, MTP-PE caused a statistically significant increase in the incidence of local and systemic side effects, which was felt to outweigh the small increase in immunogenicity provided by this biological response modifier in an otherwise well-tolerated vaccine.