Determinants of antibody response after recombinant gp160 boosting in vaccinia-naive volunteers primed with gp160-recombinant vaccinia virus. The National Institute of Allergy and Infectious Diseases AIDS Vaccine Clinical Trials Network.

Priming with a live recombinant vector followed by subunit boosting is a promising strategy for human immunodeficiency virus (HIV) immunization. Twenty-nine vaccinia-naive volunteers were primed with gp160-recombinant vaccinia virus (HIVAC-1e) and boosted with recombinant (r) gp160 to define factors associated with the magnitude and specificity of antibody response after booster immunization. A longer interval between inoculation and boost, two inoculations of HIVAC-1e with lesion formation occurring after the first, and Western blot-detectable antibody to gp160 after inoculation were significantly associated with higher neutralizing antibody titers and fusion-inhibiting activity after boosting. HIVAC-1e-primed vaccinees were more likely to have antibody to V3- and CD4-binding regions of gp120 and less likely to have antibody to constant regions 2 and 3 than vaccinees immunized with rgp160 alone. Priming volunteers with HIVAC-1e was a key determinant of the epitope specificity and magnitude of functional antibody responses induced by rgp160 boosting.