Multiple-infection and recombination in HIV-1 within a longitudinal cohort of women.

Multiple-infection and recombination in HIV-1 within a longitudinal cohort of women.

Recombination between strains of HIV-1 only occurs in individuals with multiple infections, and the incidence of recombinant forms implies that multiple infection is common. Most direct studies indicate that multiple infection is rare. Templeton and colleagues set out to determine the rate of multiple infection in a longitudinal study of 58 HIV-1 positive participants from The Women’s Interagency HIV Study with a richer sampling design than previous direct studies, and they investigated the role of recombination and sampling design on estimating the multiple infection rate. 40% of their sample had multiple HIV-1 infections. This rate of multiple infection is statistically consistent with previous studies once differences in sampling design are taken into account. Injection drug use significantly increased the incidence of multiple infections. In general there was rapid elimination of secondary strains to undetectable levels, but in 3 cases a superinfecting strain displaced the initial infecting strain and in two cases the strains coexisted throughout the study. All but one secondary strain was detected as an inter- and/or intra-genic recombinant. Injection drug use significantly increased the rate of observed recombinants. The study’s multiple infection rate is consistent with rates estimated from the frequency of recombinant forms of HIV-1. The fact that the results are also consistent with previous direct studies that had reported a much lower rate illustrates the critical role of sampling design in estimating this rate. Multiple infection and recombination significantly add to the genetic diversity of HIV-1 and its evolutionary potential, and injection drug use significantly increases both.

Editors’ note: Multiple infection may mean co-infection, where the host is infected by two or more strains of HIV, or superinfection, where the initial infection is followed by a later secondary infection. In this detailed genetic study of 23 women with multiple infections, 10 were detected as potentially co-infected at the first study visit and 13 were definitely superinfected during the study. All of them experienced recombination between pol and env genes, with most eventually losing the recombinant strain. Among the 13 superinfected women, the original strain was replaced by the second strain in 3 cases. This suggests that most of the time selection works to eliminate recombinants and superinfecting strains unless they have very superior fitness and competitive ability. However, the bottom line is that initial HIV infection does not protect against superinfection, underscoring the personal benefits of positive prevention for people living with HIV.