Genotypic analysis of the protease and reverse transcriptase of HIV type 1 isolates from recently infected injecting drug users in western China.

The partial pol gene was analyzed to determine circulating HIV-1 subtypes and the prevalence of drug resistance among recently infected injecting drug users in the west of China. Phylogenetic and bootscanning analyses showed that all 25 sequences belonged to CRF07_BC. No major drug resistance mutations were found, while the CRF07_BC sequences harbored a few highly prevalent polymorphic positions in both the protease and reverse transcriptase regions. It is notable that D60E, L63P and I93L substitutions, which were more common in HIV-1 isolates from PI-treated than untreated patients, were present in most of the isolates. Compared with subtype B, the CRF07_BC strains had a decreased genetic barrier for the V106M mutation, which is selected by efavirenz and leads to high-level resistance to all present nonnucleoside RT inhibitors. Further studies are needed to determine the impact of genetic features of CRF07-BC on antitretroviral susceptibility and evolution of drug resistance mutations.