Genomic characteristics of the new HIV-1 CRF07_BC K 28 E 32 variant.

Accompanied with the appearance and prevalence of the new K28E32 variant among MSM, HIV-1 CRF07_BC was becoming the most predominant subtype circulating in China. The K28E32 variant with 5 specific mutations in reverse transcriptase (RT) coding region appears to have significantly higher in vitro HIV-1 replication ability than the wild-type (WT) strain. In this study, we characterized the special mutations/substitutions in the K28E32 variant at the genomic level. Ten specific mutations that rarely appeared in other 6 main HIV-1 subtypes/CRFs (A-D, CRF01_AE and CRF02_AG) were identified in the coding genes/regions of the K28E32 variant, including S77L and a novel 7-amino acid detection (32DKELYPL38) (p6Δ7) in p6, I135L in integrase (IN), T189S in Vif, H/Y15L/F in Vpr, I264V/A and LV/LI328-329VG in gp41, and H82C and S97P in Rev. The special locations of the novel p6Δ7, and gp41 mutations I264V/A and LV/LI328-329VG in crucial protein functional domains suggest that these mutations might be functional important to the K28E32 variant. Furthermore, 8 specific substitutions were identified in Rev responsive element (RRE) of the K28E32 variant, and were revealed to increase the stability of RRE structure with a lower minimum free energy. Whether these mutations/substitutions contribute to improved transmissibility of the CRF07_BC K28E32 variant needs to be further confirmed.