CAPRISA 004 tenofovir microbicide trial: No impact of tenofovir gel on the HIV transmission bottleneck

Alterations of the genital mucosal barrier may influence the number of viruses transmitted from a human immunodeficiency virus-infected source host to the newly infected individual. We used heteroduplex tracking assay and single-genome sequencing to investigate the effect of a tenofovir-based microbicide gel on the transmission bottleneck in women who seroconverted during the CAPRISA 004 microbicide trial. Seventy-seven percent (17 of 22; 95 confidence interval [CI], 56-90) of women in the tenofovir gel arm were infected with a single virus compared with 92 (13 of 14; 95 CI, 67->99) in the placebo arm (P =. 37). Tenofovir gel had no discernable impact on the transmission bottleneck. © 2012 The Author.