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 surveill ance 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 s eroprevalences of 10% for injection drug users (IDU) and 3% for female commercial sex workers (CSW) in Vietnam are comparable to those obser ved in the same risk groups in Thailand five years ago. To clarify if concurrent epidemics with different HIV-1 subtypes (or clades) are occ urring among different high-risk behavior groups in Vietnam, we conduc ted a genotypic analysis of HIV-1 by amplifying and sequencing a 325-n ucleotide region spanning the principal neutralizing domain, or V3 loo p, of the gp120-encoding env gene from genomic DNA extracted from drie d, filter paper-blotted blood samples, collected in April/May and Augu st/September 1995 from 8 HIV-1-seropositive CSW in Ho Chi Minh City, C an Tho and An Clang provinces and from 16 IDU in Ho Chi Minh City, Han oi, Nha Trang and An Giang province. Sequence alignment and comparison with other HIV-1 subtypes indicated that the HIV-1 strains from CSW a nd IDU in Vietnam were genetically most similar to subtype E strains f rom Cambodia. The interstrain genetic variation among the Vietnam HIV- 1 env sequences ranged from 0.3% to 9.0% (mean, 4.6%). Phylogenetic an alysis verified that some of the Vietnam HIV-1 strains formed discrete clusters and were indistinguishable from other Southeast Asian strain s. The demonstration of subtype E in both CSW and IDU in Vietnam contr asts sharply with the previously observed HIV-1 clade restriction in t hese high-risk behavior groups in nearby Thailand.