Similar antibody responses to subtype C ALVAC-HIV/gp120 vaccine regimens using different adjuvants

Background: The partially efficacious RV144 HIV-1 vaccine trial utilized a gp120 protein boost adjuvanted with alum, whereas the non-efficacious HVTN 702 preventive HIV vaccine utilized a gp120 protein boost adjuvanted with MF59. We compared Env-specific IgG and IgA responses in HVTN 107, a phase 1/2a partially double-blinded clinica trial, utilizing a Clade C ALVAC-HIV prime and 100 mcg gp120 protein boost adjuvanted with alum or MF59 vs. a protein-only boost. Methods: We randomized 132 participants into 4 groups and analyzed Env-specific IgG and IgA binding antibodies at Months 6.5 and 12 (NCT03284710). Results: Robust IgG (96.3% to 100%) and IgA (92% to 93%) responses were seen for all trial arms at the month 6.5 timepoint to gp120 Env proteins contained in the vaccine regimen (ZM96, TV1.C and 1086.C). Compared to all other trial arms, T3 (MF59-adjuvanted co-administration) exhibited significantly greater response rates and magnitudes to vaccine-matched Env proteins at the month 12 time-point. Comparable IgG response rates and magnitudes to vaccine-matched Env proteins were observed between the alum and MF59 prime-boost trial arms. Compared to other groups, T3 exhibited significantly higher IgG response rates to V1V2 panel antigens gp70_B.CaseA_V1V2 (83% vs. 18%-48%, p