Phenotypic and genotypic characterization of Human Immunodeficiency Virus type 1 CRF07_BC strains circulating in the Xinjiang Province of China

Twelve HIV-1 CRF07_BC variants were isolated from the blood of the HIV-1-infected IDUs in Xinjiang province, and 20 subtype B' isolates were obtained from the FPDs in Anhui and Shanxi provinces of China. All the CRF07_BC viruses utilized CCR5 co-receptor, whereas 12 subtype B' viruses were R5-tropic, and the remaining B' isolates were dual (R5X4) tropic. CRF07_BC viruses had lower net charge value in the V3 loop and exhibited slower replication kinetics than subtype B' viruses. The number and location of the potential N-linked glycosylation sites in V1/V2 and the C2 region of the CRF07_BC viruses were significantly different from those of the subtype B' viruses.The HIV-1 CRF07_BC recombinant strains with relatively lower net charges in the V3 loop exclusively utilize CCR5 co-receptor for infection and exhibit slow replication kinetics in the primary target cells, suggesting that CRF07_BC may be superior over B' and other HIV-1 subtypes in initiating infection in high-risk population. These findings have molecular implications for the adaptive evolution of HIV-1 circulating in China and the design of tailored therapeutic strategy for treatment of HIV-1 CRF07_BC infection.The human immunodeficiency virus type 1 (HIV-1) which has high genetic diversity is classified into groups M, N, and O. The group M viruses that are responsible for the global AIDS epidemic have been further categorized into nine HIV-1 genetic subtypes – A, B, C, D, F, G, H, J, and K, as well as more than 34 circulating recombinant forms (CRFs) [1]. The recombinants may have enhanced fitness over their parental strains, resulting in increased pathogenicity [2,3]. In addition, a high prevalence of intersubtype recombinants (ISR) has also been reported in some areas [4].In late 1980s, initial HIV-1 epidemic among intravenous drug users (IDUs) in Yunnan province, in the southwest of China, was caused by a mixture of subtype B and Thai subtype B (B'), but the B' subtype became dominate in the middle of t