Inhibition of the Anti-V3 Loop Response to a Recombinant gp120SF2 Vaccine by Preexisting Monoclonal Antibody

Abstract

Our previous studies have shown that maternally transferred MAb 83.1 (Repligen), which recognizes the V3 loop of HIV-1SF2, inhibited the anti-V3 IgG response of offspring BALB/c mice immunized with rgp120SF2(Chiron). To determine the mechanism of this epitope-specific inhibition, MAb 83.1 was directly administered intraperitoneally to 19-day-old BALB/c mice, followed by immunization with rgp120SF2 adjuvant at 21 days of age. The total serum anti-rgp120SF2 MAb 83.1, but the anti-V3 IgG response was significantly inhibited (p 0.03) 12 weeks after immunization. These results confirm epitope-specific inhibition of the immunodominant V3 loop and are consistent with epitope masking by preexisting antibody. Idiotypic dysregulation is unlikely since MAb 83.1 exposure was not required during the period of repertoire development in neonatal mice. Treatment with MAb prior to immunization may redirect the epitope specificity of an HIV vaccine response. in Freund's complete IgG response was not inhibited by preexisting