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277 Circulating Strains of HIV-1 in Community Cohorts in Thailand Are Not Purely CRF01_AE
V. Watanaveeradej1, J. K. Carr*2, M. Hoelscher 3, N. Sirisopana1, M. Benenson4, A. Brown4, D. Birx5, and F. E. McCutchan2
1Royal Thai Army, Bangkok, Thailand; 2 Henry M. Jackson Fndn., Rockville, MD, USA; 3Univ. of Munich, Germany; 4Armed Forces Res. Inst. of Med. Sci., Bangkok, Thailand; and 5Walter Reed Army Inst. of Res., Rockville, MD, USA
Background: HIV-1 viruses circulating in the general population in Thailand have been, almost exclusively, the circulating recombinant form, CRF01_AE. In preparation for vaccine trials, the incident viruses in 2 cohorts in Thailand were subjected to full genome sequencing and analysis.
Methods: Prospective studies in 2 communities in Thailand have been performed and newly infected individuals identified. DNA was extracted from PBMC, amplified in a single large amplicon and used for automated sequencing in an ABI 3100 capillary sequencer. We developed a new screening technique using real-time PCR with subtype-specific fluorescent probes to detect subtypes B, C, or CRF01 and recombinants of these that might be circulating in the population. The assay was tested on 28 known genotype samples including all of the seroincident cases in these 2 cohorts.
Results: There were 6 incident HIV-1 infections in the family planning cohort in Rayong and 15 infections in the community cohort in Chon Buri. All viruses from Rayong but only 13 of the viruses from Chon Buri were CRF01_AE. One of the non-CRF01 Chon Buri viruses was subtype B and one was a B/CRF01 recombinant. The recombinant was mostly CRF01, with part of vpr and tat from subtype B. Through real-time PCR analysis of 4 genomic regions, the genotypes of 28 known samples were confirmed. This assay showed a sensitivity of at least 80% in each of the genomic regions and detected correctly 5 out of 5 B/CRF01 recombinants and 1 C/CRF01 recombinant.
Conclusions: Although CRF01_AE is the predominant genetic form of HIV-1 in presumed heterosexually exposed populations in Thailand, there is a small but substantial minority of subtype B and other recombinants. It is significant that incident infections include strains other than CRF01_AE in a potential vaccine trial cohort. Vaccine candidates should include genetic components from both CRF01_AE and subtype B.
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