HIV-1 sequence evolution in vivo after superinfection with three viral strains

Abstract

With millions of people infected worldwide, the evolution of HIV-1 in vivo has been the subject of much research. Although recombinant viruses were detected early in the epidemic, evidence that HIV-1 dual infections really occurred came much later. Dual infected patients, consisting of coinfected (second infection before seroconversion) and superinfected (second infection after seroconversion) individuals, opened up a new area of HIV-1 evolution studies. Here, we describe the in-depth analysis of HIV-1 over time in a patient twice superinfected with HIV-1, first with a subtype B (B2) strain and then with CRF01Æ after initial infection with a subtype B (B1) strain. The nucleotide evolution of gagand env-V3 of the three strains followed a similar pattern: a very low substitution rate in the first 2-3 years of infection, with an increase in synonymous substitutions thereafter. Convergent evolution at the protein level was rare: only a single amino acid in a gag p24 epitope showed convergence in the subtype B strains. Reversal of CTL-epitope mutations were also rare, and did not converge. Recombinant viruses were observed between the two subtype B strains. Luciferase-assays suggested that the CRF01Æ long terminal repeat (LTR) constituted the strongest promoter, but this was not reflected in the plasma viral load. Specific real-time PCR assays based upon the env gene showed that strain B2 and CRF01Æ RNA was present in equal amounts, while levels of strain B1 were 100-fold lower. All three strains were detected in seminal plasma, suggesting that simultaneous transmission is possible. © 2007 Kozaczynska et al; licensee BioMed Central Ltd.