title: The evolving molecular epidemiology of HIV-1 envelope subtypes in injecting drug users in Bangkok, Thailand: implications for HIV vaccine trials.
abstract: OBJECTIVE
  To genetically characterize HIV-1 strains in injecting drug users (IDU) in Bangkok, Thailand in 1994, and compare these with strains found earlier in Thai IDU; such information is essential for HIV-1 vaccine development and evaluation.
  
  
  METHODS
  Peripheral blood mononuclear cells were collected from 84 IDU attending 14 drug treatment clinics in Bangkok in 1994. DNA was amplified using a nested polymerase chain reaction (PCR) procedure and sequenced directly (without cloning) from the PCR products. The V3 and flanking regions (345 nucleotides) of the env gene were analyzed using a neighbor-joining tree.
  
  
  RESULTS
  Only one (1%) strain was a typical subtype B virus, 69 (82%) were genetically distinct subtype B' viruses (Thai B), and 14 (17%) were subtype E strains (Thai A). Persons with recently acquired infection were more likely to have subtype E viruses (P < 0.001) than those in our 1991 survey, who were more likely to have subtype B' viruses. Pairwise intra-subtype differences within subtypes E and B' were 5.3 and 4.3%, respectively, compared with 3.4 and 3.5% among strains collected in 1991 in Thailand.
  
  
  CONCLUSIONS
  The genetic diversity within subtypes B' and E in Thailand and the proportion of new infections due to subtype E viruses among Bangkok IDU are increasing significantly. These data highlight the importance of monitoring the molecular epidemiology of HIV-1 in populations being considered for HIV-1 vaccine trials.
authors.affiliation: Division of HIV/AIDS, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Kalish
authors.forename: A
authors.initials: A
authors.lastname: Baldwin
authors.forename: S
authors.initials: S
authors.lastname: Raktham
authors.forename: C
authors.initials: C
authors.lastname: Wasi
authors.forename: C C
authors.initials: CC
authors.lastname: Luo
authors.forename: G
authors.initials: G
authors.lastname: Schochetman
authors.forename: T D
authors.initials: TD
authors.lastname: Mastro
authors.forename: N
authors.initials: N
authors.lastname: Young
authors.forename: S
authors.initials: S
authors.lastname: Vanichseni
authors.forename: H
authors.initials: H
authors.lastname: Rübsamen-Waigmann
mesh_terms: D016915:AIDS Vaccines / Q000494:pharmacology; D000595:Amino Acid Sequence; D001483:Base Sequence; D002986:Clinical Trials as Topic; D017931:DNA Primers / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D015752:Genes, env; D014644:Genetic Variation; D006031:Glycosylation; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics; D015658:HIV Infections / Q000150:complications* / Q000453:epidemiology / Q000821:virology*; D015497:HIV-1 / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D015819:Substance Abuse, Intravenous / Q000150:complications* / Q000821:virology*; D013785:Thailand / Q000453:epidemiology
chemical_list: D016915:AIDS Vaccines; D017931:DNA Primers; D004279:DNA, Viral; D015699:HIV Envelope Protein gp120