762-W. Microepidemiology of HIV in Vietnam: Distinct Nucleotide Substitutions in the gp120 V3 and C3 Regions

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Session 100 Poster Session
Molecular Epidemiology
Session Time: 4:30-6:30 pm
Room 4E-F

762-W.

Microepidemiology of HIV in Vietnam: Distinct Nucleotide Substitutions in the gp120 V3 and C3 Regions
F. Isami*¹, T. H. Pham^{1, 2}, H. T. Nguyen¹, A. H. Mai³, C. K. Pham¹, L. T. Hoang¹, R. Detels⁴, R. Yanagihara¹, and V. R. Nerurkar¹
¹Univ. of Hawaii, Honolulu; ²Natl. Inst. of Hygiene & Epidemiology, Hanoi; ³Preventive Med. Ctr., An Giang, Vietnam; and ⁴Univ. of California, Los Angeles

Background: Previously we demonstrated high prevalence of a methionine substitution at the tip of the V3 loop (MGPGQ) among HIV CRF_AE strains from Vietnam. The aim of this study was to identify other molecular markers or “signature sequences” for mapping the spread of HIV in Vietnam and in neighboring Southeast Asian countries.
Methods: A 293-bp region of the HIV-1 gp120 env gene was amplified from RNA extracted from plasma collected during 1995-1999 from 125 HIV-infected injection drug users (IDU) and 68 virus-infected commercial sex workers (CSW) from Vietnam. Sequences were aligned and compared to 143 HIV CRF_AE strains from Thailand, Cambodia, and China. Genetic distances and the distribution of the specific substitutions were ascertained for all sequences.
Results: We identified 3 distinct substitutions as molecular markers, which separated the HIV CRF_AE strains from Vietnam in 4 groups: ET, ECV, ECM, and EC, where the first letter represents CRF_AE, the second letter represents the nucleotide at position 7273, and the third letter represents amino acids methionine or valine at positions 309 and 314, respectively. ET, the most divergent strain, was predominant in Thailand and among CSW in Vietnam. ECM and EC were observed mainly in both CSW and IDU in South Vietnam whereas ECV was unique to IDU in North Vietnam.
Conclusions: Analysis of the sequence diversity and molecular grouping suggested that the ET strain initially gained entry in CSW in southern Vietnam. Unique substitutions among ECM and EC strains in IDU and CSW from southern Vietnam suggested independent introduction and spread of HIV among these high-risk groups. Unique and identical amino acid substitutions found in ECV strains from IDU in northern Vietnam and southern China suggested cross-border travel of virus-infected IDU and further strengthens the hypothesis of HIV spread via drug trafficking from Myanmar/Laos to northern Vietnam and into southern China.