Sequence and phylogenetic analyses of HIV-1 infection in Vietnam: subtype E in commercial sex workers (CSW) and injection drug users (IDU).

More than 4,000 persons with human immunodeficiency virus type 1 (HIV-1) infection have been identified in Vietnam through sentinel surveillance since 1990, when the first case of HIV-1 infection was diagnosed in a young woman in Ho Chi Minh City. Currently, the estimated HIV-1 seroprevalences of 10% for injection drug users (IDU) and 3% for female commercial sex workers (CSW) in Vietnam are comparable to those observed in the same risk groups in Thailand five years ago. To clarify if concurrent epidemics with different HIV-1 subtypes (or clades) are occurring among different high-risk behavior groups in Vietnam, we conducted a genotypic analysis of HIV-1 by amplifying and sequencing a 325-nucleotide region spanning the principal neutralizing domain, or V3 loop, of the gp120-encoding env gene from genomic DNA extracted from dried, filter paper-blotted blood samples, collected in April/May and August/September 1995 from 8 HIV-1-seropositive CSW in Ho Chi Minh City, Can Tho and An Giang provinces and from 16 IDU in Ho Chi Minh City, Hanoi, Nha Trang and An Giang province. Sequence alignment and comparison with other HIV-1 subtypes indicated that the HIV-1 strains from CSW and IDU in Vietnam were genetically most similar to subtype E strains from Cambodia. The interstrain genetic variation among the Vietnam HIV-1 env sequences ranged from 0.3% to 9.0% (mean, 4.6%). Phylogenetic analysis verified that some of the Vietnam HIV-1 strains formed discrete clusters and were indistinguishable from other Southeast Asian strains. The demonstration of subtype E in both CSW and IDU in Vietnam contrasts sharply with the previously observed HIV-1 clade restriction in these high-risk behavior groups in nearby Thailand.