Background: A better understanding of maturation of humoral immune response in HIV infection may help in the evaluation of antibody responses in different subtype infections and development of subtype-independent serologic assays for detecting recent HIV infection for incidence estimates.

Methods: Longitudinal specimens (n = 529) from 90 seroconverters with subtype B (n = 18) or subtype E (n = 72) infections were tested by a variety of quantitative assays to determine the changing parameters of HIV antibody following seroconversion. Multi-subtype peptide antigens from gp41-immunodominant region (BED peptide) and V3 (B+E) of gp120 were used. We used BED-less sensitive EIA as a surrogate for titer, IgG-Capture BED-EIA to measure proportion of HIV-IgG, and gp41-BED-EIA (±8 M urea) to measure antibody avidity. V3 (B+E)-specific EIA was used to detect anti-V3 antibodies.

Results: Titer, proportion, and avidity of antibodies to gp41-BED increased following seroconversion. However, the increase was at a slower rate in subtype B than in E infections. In most subtype B-infected individuals, titer and proportion of HIV-IgG increased for over 2 years, whereas those parameters reached plateau in many subtype E-infected individuals within 1 year. Antibody avidity to BED reached peak levels in about 4–5 months after seroconversion but was slower in subtype B than in E infections. Kinetics of antibodies to V3 loop epitope was also slower in subtype B than in E infections with significant differences in median slopes.

Conclusions: These data suggest that humoral antibody to HIV may be elicited at somewhat different rates in subtype B or E infections and may be related to differences in early viral load. These findings have implications for development of subtype-independent assays for detecting recent infection and they shed further light to host-virus interactions.