Molecular epidemiology of HIV type 1 in Singapore and identification of novel CRF01_AE/B recombinant forms.

To investigate HIV-1 molecular epidemiology in Singapore, we sequenced portions of three regions of the HIV-1 genome (protease HXB2: 2163 to 2620, gp120 HXB2: 6904 to 7628, and gp41 HXB2: 7817 to 8264) from 212 plasma samples collected between February 2008 and August 2009. From these samples, 109 (51.4%) generated interpretable data in all regions. Sixty-one (56.0%) were identified as CRF01_AE, 26 (23.9%) as subtype B and 14 (12.8%) as possible novel recombinant forms. The main novel recombinant pattern, detected in 13 sequences, had subtype B in protease and gp41 and CRF01_AE in gp120. There was intermixing of subtypes within transmission risk groups. However, 85% of subjects infected with the novel recombinant forms self-identified as men who have sex with men or bisexuals compared with only 41% of individuals infected with CRF01_AE and 62% infected with subtype B (p = 0.001).