HIV type-1 transmission dynamics in recent seroconverters: relationship with transmission of drug resistance and viral diversity.

BACKGROUND: HIV type-1 (HIV-1) has been shown to be frequently transmitted by acutely infected patients. We investigated the relationship between the dynamics of HIV-1 transmission within recently infected patients, the HIV-1 variability and the transmission of antiretroviral drug resistance.
METHODS: We included patients infected between 1996 and 2006, with a plasma sample obtained <18 months after seroconversion and prior to antiretroviral therapy initiation. Reverse transcriptase (RT) and protease sequences were determined by direct population sequencing from plasma samples. Genotypic resistance was interpreted with the Agence Nationale de Recherches sur le SIDA et les Hépatites Virales 2006 algorithm and International AIDS Society-USA list. Phylogenetic analysis (neighbour-joining and maximum likelihood methods) of RT sequences was used to determine the HIV-1 subtype and the interrelationship between sequences.
RESULTS: Genotypic resistance was detected in 37/263 (14.1%) patients. Patients were infected by HIV-1 clade B in 222 (84%) cases and with non-B subtypes in 41 (16%). A total of 80 (30.4%) RT sequences were segregated in 24 clusters with bootstrap values >98% for 22 clusters. The frequency of grouping in clusters was higher within B sequences compared with non-B sequences (35.1% versus 4.9%; P<2.10(-4)). Drug-resistant isolates were retrieved in only 3 clusters, but the prevalence of resistance in clustering viruses (10/80, 12.5%) was not different than in isolated sequences.
CONCLUSIONS: The segregation into clusters suggested frequent forward transmission events in patients infected with HIV-1 subtype B, including the possibility of transmission of drug-resistant isolates. These findings warrant increasing prevention efforts and serological screening in the at-risk populations.