8th International AIDS Conference Amsterdam, Netherlands — July 19-24, 1992

Int Conf AIDS 1992 Jul 19-24; 8:We49 (abstract no. WeC 1025)
Ou CY, Auwanit W, Pau CP, Luo CC, Kalish M, Takebe Y, Bandea C, Lee-Thomas S, George JR, Schochetman G, et al; Division of HIV/AIDS, Centers for Disease Control, Atlanta, Georgia.

OBJECTIVES: To determine the molecular epidemiology of the HIV explosion in Thailand since 1988 and to develop peptide-based serologic assays to facilitate HIV-1 subtyping.

METHODS: Blood samples were collected in 1991 from infected persons with various risk behaviors from 7 provinces. HIV proviral DNA was amplified through the polymerase chain reaction and sequenced. Enzyme-linked immunoassays based on peptides derived from the V3 loops of HIV-1 subtypes were developed for serosurveys.

RESULTS: Only 2 genetically distinct HIV-1 subtypes (A and B) were identified among 52 infected persons. Subtype A was genetically distant from American HIV-1 consensus sequences while subtype B was genetically more related. Average sequence difference between subtypes A and B was 22%, too high to have diverged from a common HIV-1 precursor since 1988. Both genetic and serologic subtyping revealed that 91% (20/22) of persons presumably infected through sexual transmission had HIV-1 subtype A, while 75% (21/28) of injecting drug users had subtype B (p less than 0.001). Subtype A also appeared to be predominant in the northern region of Thailand.

CONCLUSION: Two HIV-1 subtypes independently entered Thailand in the late 1980s and infected most of the estimated 300,000 HIV-positive Thais by 1991. Subtype A was primarily sexually transmitted whereas subtype B was parenterally transmitted. These findings will assist in understanding the epidemiologic patterns of HIV transmission, and developing a vaccine in Thailand.

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