Genomic Characteristics of the New HIV-1 CRF07_BC K28E32 Variant.

Accompanied with the appearance and prevalence of the new K₂₈E₃₂ variant among men who have sex with men, HIV-1 circulating recombinant form 07_BC (CRF07_BC) was becoming the most predominant subtype circulating in China. The K₂₈E₃₂ variant with five specific mutations in reverse transcriptase coding region appears to have significantly higher in vitro HIV-1 replication ability than the wild-type 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 six 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 seven-amino acid detection (32DKELYPL38) (p6Δ7) in p6, I135L in integrase, 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 functionally important to the K₂₈E₃₂ variant. Furthermore, eight 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.