Modulation of epitope-specific antibody response by HIV Env immune-complex vaccines

Abstract

Abstract HIV-1 envelope (Env) antigen is an important target for both neutralizing and non-neutralizing antibodies (Ab) against the virus. In the RV144 vaccine trial, correlate for reduced risk of HIV acquisition is the presence of binding but non-neutralizing Ab to V1V2 and V3 loops of HIV Env gp120. However, induction of high titer, durable, and cross-reactive Ab responses against these Env regions by vaccination is still an elusive goal. Our past studies have shown that V3 immunogenicity can be significantly enhanced by vaccination with gp120/mAb immune complexes (IC) vs gp120 alone. Current study further examined parameters that confer enhanced immunogenicity to IC by testing in mice IC vaccines made with different HIV Env gp120 (clade B vs clade E) and mAb of different specificities (V3, V2, or CD4 binding site (CD4bs)). In addition, IC made of clade C gp140 and CD4bs mAb were also tested. The data showed that Greater titers of cross-reactive V3-binding Ab were induced by IC made of clade B gp120 and mAb to V2 or CD4bs as compare with gp120 alone, although the gp120/CD4bs IC was more potent in eliciting neutralizing V3 Ab. IC made with clade E gp120 or clade C gp140 did not show the same effects.Greater Ab responses to V1V2 were induced by IC made of clade E gp120 vs gp120 alone, regardless of the mAb used for IC, but the Ab were not neutralizing. IC made with clade B gp120 and clade C gp140 did not enhance V1V2 Ab titers. These results demonstrate the capacity of Env/mAb IC vaccines to modulate induction of Ab responses to V1V2 and V3, and this activity is dependent on both Env proteins and mAb used to form IC. Further exploration using a cocktail of IC is proposed to improve Ab repertoires generated upon vaccination.