17th International AIDS Conference Mexico City, Mexico - August 13 - 18, 2008

PHYLODYNAMICS OF HIV-1 CRF08_BC AND CRF07_BC IN ASIA: A BAYESIAN COALESCENT STRATEGY

Int Conf AIDS. 2008 Aug 13-18;17 Abstract No. MOAA0205

K.K. Tee ¹, O.G. Pybus², X.J. Li³, X. Han⁴, H. Shang⁴, A. Kamarulzaman⁵, Y. Takebe^1
1National Institute of Infectious Diseases, Laboratory of Molecular Virology and Epidemiology, AIDS Research Center, Tokyo, Japan, ²University of Oxford, Department of Zoology, Oxford, United Kingdom, ³Shanghai Jiao Tong University, Department of Dermatology, The First People's Hospital, Shanghai, China, ⁴China Medical University, Key Laboratory of AIDS Immunology, The First Affiliated Hospital, Liaoning, China, ⁵University of Malaya, Department of Medicine, Faculty of Medicine, Kuala Lumpur, Malaysia

BACKGROUND: HIV-1 CRF08_BC and CRF07_BC are two closely-related recombinants descended from subtype B´ and C that predominate among injecting drug users (IDU) in China. Despite their massive epidemic impact, the divergence times and migration patterns of these recombinants remain unknown.

METHODS: Phylogenetic and population genetic analyses were performed on 228 HIV-1 nucleotide sequences, representing CRF08_BC, CRF07_BC and subtype C strains isolated from different locations across China, India and Myanmar. The genome-specific rates of evolution were independently estimated using a Bayesian MCMC framework under various evolutionary models. Using these rates, the times of the most recent common ancestors of CRF08_BC, CRF07_BC and subtype C were estimated.

RESULTS: Genealogy-based analyses show that CRF08_BC originated in 1990.3 (95% credible region, CR: 1988.6-1991.9) in Yunnan province, before spreading to Guangxi (south) and Liaoning (northeast) around 1995. Inside Guangxi region, the eastward expansion of CRF08_BC continued from Baise city (west) to Binyang (central) between 1997 and 1998, and later spread into Pingxiang around 1999 in the south (near the Vietnamese border), mainly through injecting drug use. Additionally, CRF07_BC diverged from its common ancestor in 1993.3 (95% CR: 1991.2-1995.2) before crossing the border into southern Taiwan in the late 1990s. Phylogenetic analysis indicates that both CRF08_BC and CRF07_BC can trace their origin to Yunnan. The parental Indian subtype C lineage likely entered China around 1981.2 (95% CR: 1976.7-1985.9), possibly through Myanmar.

CONCLUSIONS: This is the first phylodynamic survey of the eastward dissemination of HIV-1 CRF08_BC, CRF07_BC and subtype C in China. We highlight the significance of their evolutionary histories to viral epidemiology, migration and molecular taxonomy.

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2008-08-13
MOAA0205

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