Determination of HIV-1 subtypes in injecting drug users in Bangkok, Thailand, using peptide-binding enzyme immunoassay and heteroduplex mobility assay: evidence of increasing infection with HIV-1 subtype E.

OBJECTIVES: To evaluate the sensitivity and specificity of peptide-binding enzyme immunoassay (PEIA) and heteroduplex mobility assay (HMA) for the determination of HIV-1 subtypes B and E; to determine the proportions of infections due to subtypes B and E over time; and to generate data on DNA sequences of the C2-V3 region of the env genes.
METHODS: HIV-1 subtyping was conducted by PEIA and HMA on blood specimens obtained from 97 injecting drug users (IDU) infected with HIV between 1988 and 1993. Genetic sequencing was performed on 84 specimens.
RESULTS: Both laboratory methods were highly sensitive and specific for the determination of HIV-1 subtypes B and E. The two tests were complementary; samples which could not be typed by HMA were correctly typed by PEIA and vice versa. While subtype B accounted for 80.4% (78 out of 97) of infections overall, the proportion of new infections due to subtype E increased from 2.6% (one out of 38) in 1988-1989 to 25.6% (11 out of 43) in 1990-1991, and to 43.8% (seven out of 16) in 1992-1993 (chi 2 for linear trend, P < 0.001).
CONCLUSIONS: HMA and PEIA are practical, sensitive and specific laboratory methods for the determination of HIV-1 subtypes in Thailand, and may be useful in other geographic areas to define the molecular epidemiology of the global HIV-1 pandemic. Data suggest that the proportion subtype E infections have increased among Bangkok IDU from 1988 through 1993.