LAUSR

OBJECTIVE To estimate time of HIV infection in participants from the Bangkok Tenofovir Study (BTS) with daily oral tenofovir disoproxil fumarate (TDF) for pre-exposure prophylaxis (PrEP) and relate infection with adherence patterns. DESIGN We used the diversity structure of the virus population at the first RNA-positive sample to estimate the date of infection, and mapped these estimates to medication diaries obtained under daily directly observed therapy (DOT). METHODS HIV genetic diversity was investigated in all 17 PrEP breakthrough infections and in 16 placebo recipients. We generated 10 to 25 HIV env sequences from each participant by single genome amplification, and calculated time since infection (and 95% confidence interval) using Poisson models of early virus evolution. Study medication diaries obtained under daily DOT were then used to compute the number of missed TDF doses at the approximate date of infection. RESULTS Fifteen of the 17 PrEP breakthrough infections were successfully amplified. Of these, 13 were initiated by a single genetic variant and generated reliable estimates of time since infection (median=47 [IQR=35] days). Eleven of these 13 were under daily DOT at the estimated time of infection. Analysis of medication diaries in these 11 participants showed 100% adherence in five, 90-95% adherence in two, 55% adherence in one, and non-adherence in three. CONCLUSIONS We estimated time of infection in participants from BTS and found several infections when high levels of adherence to TDF were reported. Our results suggest that the biological efficacy of daily TDF against parenteral HIV exposure is not 100%.