Loss of antibody reactivity directed against the V3 domain of certain human immunodeficiency virus type 1 variants during disease progression.

We have previously shown that in AIDS patients a predominant species of infectious virus can be found which is not neutralized by homologous serum. The presence of the infectious virus was associated with the lack of type-specific antibody directed against the V3 domains of these virions. In contrast to this lack of V3-specific antibody, the other V3 domains of non-infectious virions were well recognized by antibody. To determine whether the lack of a V3-specific antibody response is due to a progressive loss of antibody during human immunodeficiency virus type 1 (HIV-1) infection, we monitored the anti-V3 antibody response in 90 patients over time. Anti-V3 antibodies were monitored by a V3-specific ELISA using 21 different V3 domains as a fusion with glutathione S-transferase (GST-V3) based upon sequences from 11 HIV-1 patient isolates and 10 sequences from an HIV-1 B subtype consensus-like GST-V3 expression library. This strictly heterologous screening showed a loss of V3-specific antibodies in 20 out of the 90 patients tested. To study the in vivo relevance of these findings we analysed V3 antibody loss in two patients. This strictly autologous antibody screening was performed based upon V3 sequences of the patients' cell-free virions. In both patients the loss of a V3-specific antibody could be detected in parallel to a decline of CD4+ T cells. Moreover, the escape of a distinct V3 variant was shown to correlate closely with the loss of the V3-specific antibody.