Dual specificity of a monoclonal anti-idiotypic antibody for HIV-1 neutralizing monoclonals 110.3 and 110.4 as well as the V3 loop of gp120.

Monoclonal antibodies (MAbs) 110.3 and 110.4 bind an epitope at the tip of the third hypervariable region (V3) of the envelope protein gp120 of human immunodeficiency virus type 1 (HIV-1). These MAbs inhibit HIV-induced syncytium formation and neutralize cell-free virus infection. Anti-idiotypic MAb alpha-id8, generated against 110.3, was found to mimic the V3 loop of gp120, as demonstrated by competition ELISA and by the generation of anti-anti-idiotypic sera which bound gp120 and a peptide representing the tip of the V3 loop. Interestingly, alpha-id8 itself also reacted specifically with both gp120 and the V3 loop peptide. Thus, alpha-id8 both mimics and binds directly to the V3 loop, suggesting that the V3 loop of gp120 may associate with itself.