Phylodynamics of HIV-1 from a Phase-III AIDS Vaccine Trial in North America

In 2003, a phase III placebo-controlled trial (VAX004) of a candidate HIV-1 vaccine (AIDSVAX B/B) was completed in 5,403 volunteers at high risk for HIV-1 infection from North America and the Netherlands. A total of 368 individuals became infected with HIV-1 during the trial. The envelope glycoprotein gene (gp120) from the HIV-1 subtype B viruses infecting 349 patients was sequenced from clinical samples taken as close as possible to the time of diagnosis, rendering a final data set of 1,047 sequences (1,032 from North America and 15 from the Netherlands). Here, we used these data in combination with other sequences available in public databases to assess HIV-1 variation as a function of vaccination treatment, geographic region, race, risk behavior, and viral load. Viral samples did not show any phylogenetic structure for any of these factors, but individuals with different viral loads showed significant differences (P = 0.009) in genetic diversity. The estimated time of emergence of HIV-1 subtype B was 1966-1970. Despite the fact that the number of AIDS cases has decreased in North America since the early 90s, HIV-1 genetic diversity seems to have remained almost constant over time. This study represents one of the largest molecular epidemiologic surveys of viruses responsible for new HIV-1 infections in North America and could help the selection of epidemiologically representative vaccine antigens to include in the next generation of candidate HIV-1 vaccines.