HIV-1 subtypes and male-to-female transmission in Thailand.

ABSTRACT

PIP: A case control study was conducted during February 1992-April 1993 in Bangkok, Thailand, among 62 couples of which both partners were HIV seropositive (concordant couples [cases]) and 46 couples of which the man was HIV seropositive and the woman was HIV seronegative. The subjects were patients in the Immune Clinic in Chulalongkorn Hospital and in 15 drug detoxification (IDU) clinics. Couples in the immune clinic were more likely to be HIV seroconcordant than those in the IDU clinics (69% vs. 48%; 67% vs. 27%, after excluding females who were intravenous [IV] drug users; p 0.01). HIV-1 serotype B (subtype B) was more common among men in the IDU clinics while HIV-1 serotype A (subtype E) (79%) was more common among men in the immune clinic (92%). Seroconcordance was much more common when HIV-1 was of serotype A than when it was of serotype B (70% vs. 52%; odds ratio [OR] = 2.1; p 0.05). Further, when the researchers did not include couples of which the woman was an IV drug user, the difference in concordance was even greater (70% vs. 26%, OR = 6.8; p 0.01). These differences in concordance suggest that HIV-1 serotype A may be more efficiently transmitted than HIV-1 serotype B. The multivariate logistic regression analysis showed that independent risk factors of HIV seroconcordance were HIV-1 serotype A of male partners (adjusted OR = 3.1) and history of IV drug use in female partners (AOR = 4.8). HIV-1 subtype E may be linked to a higher risk of heterosexual transmission than subtype B. If so, the predominance of HIV-1 subtype E in Thailand could explain the rapid spread of HIV infection in Thailand.