Materials and Methods:

Samples (N= 2614) were obtained from 114 women aged 18–45 years in the Ugandan Genital Shedding and Disease Progression Study cohort (2001–2009; 82 subtype A, 32 subtype D; median 23 samples/women, range 3–41 samples, median follow-up of 6.6 years). Samples were analyzed using the BED capture immunoassay (cutoff, 0.8 OD-n) and the avidity assay (cutoff, 90% Avidity Index). Antibody maturation was assessed by having the BED capture enzyme immunoassay (BED-CEIA) or avidity value exceed the assay cutoff 1 or 2 years after infection. The waning antibody response was measured by having the BED-CEIA or avidity value fall> 20% below the maximum value.

Results:

For the BED-CEIA, 8 women with subtype A infection and 3 women with subtype D infection never progressed previously the cutoff value (median, 5.9 years follow-up after infection). Six women with subtype D infection never achieved an avidity index> 90%. Subtype did not impact the proportion of women whose assay values regressed by> 20% of the maximal value (for BED-CEIA: 33% for A, 41% for D, P= 0.51; for avidity: 1% for A, 6% for D, P= 0.19).

Discussion:

The higher frequency of misclassification of individuals with long-term subtype D infection as recently infected using serologic incidence assays reflects a weak initial antibody response to HIV infection that is sustained over time.