Tracing the origin and history of HIV-1 subtype B' epidemic by near full-length genome analyses.

Objective: To investigate the origin and evolutionary history of HIV-1 subtype B' responsible for the epidemic among injecting drug users (IDUs), former plasma donors (FPDs) and the subsequent heterosexual transmission in China. Methods: A total of 33 sequences of subtype B' near full-length genomes (NFLGs) sampled during 1998-2009 in 11 provinces across China were determined. The NFLGs were subjected to Bayesian molecular clock analyses to estimate the time of the most recent common ancestors (tMRCAs) and to reconstitute the time-space process of subtype B' dissemination in China. Results: The study revealed that subtype B' strains in China can be classified into two distinct subgroups: a monophyletic B' cluster (B'CN*) consisting of subtype B' sequences mainly from FPDs and heterosexuals across China outside of Yunnan; B' strains circulating among IDUs in Yunnan (B'YN) that occupy the most basal position of B' clade in China. The tMRCAs of B'YN and B'CN* were estimated to be 1985 (1982-1987) and 1989 (1987-1991), respectively. The skyline plot profile revealed the explosive nature of subtype B' expansion in central China in the mid-1990s. Conclusion: Our results suggest that subtype B' epidemics among FPDs and heterosexuals in inland China were most likely originated from a single founding subtype B' strain that had been circulating among IDUs in Yunnan province. Yunnan province plays a pivotal role in bridging the preexisting subtype B' epidemics in south-east Asia with the subsequent epidemic among FPDs and heterosexuals in inland China. (C) 2012 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins