High HIV-1 genetic complexity in men who have sex with men (MSM) in Bangkok, Thailand
W. Leelawiwat1, M. Arroyo2, F. Mueanpai1, O. Kongpechsatit1, W. Rutvisuttinunt2, V. Assawadarachai2, M. de Souza2, S. Chaikummao1, W. Chonwattana1, J. Tongtoyai1, A. Sangiamkittikul1, F. van Griensven1,3, J. McNicholl1,3
1Thailand MOPH – U.S. CDC Collaboration, Department of Medical Sciences, Nonthaburi, Thailand, 2Department of Retrovirology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand, 3Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, United States
Background: The HIV-1 epidemic in Thailand is characterized by infections with CRF01_AE, which predominates, and Thai B (B’). Both these subtypes are specific to Thailand and uncommon elsewhere. In MSM, the high prevalence and incidence of HIV-1 infection and risk behaviors may generate new recombinants or dual infections. Here, we examine the frequency of recombinants and dual infections in a cohort of MSM in Bangkok, Thailand.
Methods: A total of 1,292 MSM were enrolled in a prospective cohort study from April 2006 to January 2008. Men were tested for HIV-1 infection at baseline and every 4 months using oral fluid (OraQuick, OraSure Technologies, USA) and confirmed by 3 HIV rapid tests. Genotyping was performed using a multi-region hybridization assay (MHA), optimized for subtypes B, C, CRF01_AE and their recombinants. Dual infections were identified by cloning and MHA. Available plasma from 278 HIV-1 seroprevalent baseline samples and 99 newly infected MSM was evaluated.
Results: Baseline HIV-1 prevalence was 22.4% (290/1,292) and HIV-1 incidence was 6.1/100 person-years (118/1,934). In seroprevalent samples, 78.3% were CRF01_AE, 3.9% B, 16.5% CRF01_AE/B recombinants, 0.4% B/C recombinants, and 0.8% triple CRF01_AE/B/C recombinants. In seroincident samples, 82.4% were CRF01_AE, 1.1% B, 15.4% CRF01_AE/B recombinants, and 1.1% B/C recombinants. Eleven seroprevalent and 5 seroincident samples had putative dual infections, of which 3 seroprevalent samples could be confirmed as having dual CRF01_AE and B infections. The remaining putative dual infections were identified as single infections after cloning.
Conclusions: The predominance of CRF01_AE infections suggests that the HIV-1 epidemic in Thai MSM is primarily a local one. However, the high frequency of CRF01_AE/B recombinants and dual infections supports the hypothesis that high-risk populations provide an opportunity for HIV-1 to diversify. This increasing diversity impacts sequence-based diagnostic technologies and has implications for HIV-1 vaccine design.