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High HIV-1 genetic complexity in men who have sex with men (MSM) in Bangkok, Thailand
W. Leelawiwat1, M. Arroyo2, F. Mueanpai1, O. Kongpechsatit1, C. Kittinunvorakoon1, V. Assawadarachai2, M. de Souza2, S. Chaikummao1, W. Chonwattana1, J. Tongtoyai1, A. Sangiamkittikul1, F. van Griensven1,3, J. Mcnicholl1,4
1Thailand MOPH - U.S. CDC Collaboration, Nonthaburi, Thailand, 2The Armed Forces Research Institute of Medical Sciences, Department of Retrovirology, Bangkok, Thailand, 3Centers for Disease Control and Prevention, Atlanta, GA, United States, 4Centers for Disease Control and Prevention, Atlanta, United States
Background: The HIV-1 epidemic in Thailand is characterized by two HIV-1 subtypes: CRF01_AE, which predominates, and Thai B, also known as B'. Because of the high risk of HIV-1 infection in MSM and reports of increasing numbers of CRF01/B' recombinant strains in high-risk heterosexuals and intravenous drug users in Thailand, we expected high HIV-1 genetic diversity in MSM in Thailand. Here we report the distribution of HIV-1 subtypes, recombinants and dual infections in a cohort of MSM in Bangkok, Thailand.
Methods: From April 2006 to January 2009, 1,292 MSM were enrolled in a prospective cohort study. Men were tested for HIV-1 infection at baseline and every 4 months using oral fluid (OraQuick, OraSureTechnologies, USA) and confirmed by enzyme immunoassay. Genotyping, using a multi-region hybridization assay optimized for subtypes B, C and CRF_01AE, was performed on plasma from 278/290 (95.9%) HIV-1 seroprevalent baseline samples and 62/82 (75.6%) seroincident samples from men infected during follow-up.
Results: HIV-1 prevalence in the cohort is 22% and incidence is 5.6/100 person-years. Of 278 seroprevalent samples, 78.3% were CRF01_AE, 3.9 % subtype B, 16.5% CRF01/B, 0.4% B/C and 0.8% CRF01/B/C. Of 62 serocoincident samples, 81.8% were CRF01_AE, 16.4% CRF01/B and 1.8% B/C. Putative dual infections were observed in 4.8% seroprevalent and 7.3% seroincident samples.
Conclusions: This is the first comprehensive report of HIV-1 subtypes in MSM in Thailand using molecular techniques. The high prevalence of HIV-1 CRF01_AE suggests a predominantly local epidemic. The high prevalence of CRF01/B recombinants and of putative dual infections in MSM supports the hypothesis that high-risk populations provide the opportunity for HIV-1 to diversify. This increasing diversity impacts sequence-based technologies and HIV-1 vaccine design.
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