title: [Molecular epidemiology related to human immunodeficiency virus type 1 infection in men having sex with men in Xi'an].
abstract: OBJECTIVE
  To investigate the subtype distribution of HIV-1 infection among men having sex with men (MSM) in Xi'an city.
  
  
  METHODS
  5 ml anti-coagulating blood samples were collected from MSM who had been reported during 2010-2012 in Xi'an. Both gag and env genes were amplified by nested RT-PCR from the extracted RNA and then sequenced. The acquired sequences were compared with international subtype references, and then the genetic distances were calculated and phylogenetic trees were constructed by Mega 5.2. Epidemiological information including sexual behavior characteristics, history of drug use, blood donation, etc. were gathered.
  
  
  RESULTS
  168 samples were successfully amplified and sequenced. Results from Phylogenic analysis showed that the gag and env sequences of 165 samples shared the same subtypes, of which 79 (47.0%) were CRF01_AE, 74 (44.0%) were CRF07_BC and 12 (7.1%) belonged to subtype B. There were 3 samples with gag and env sequences classified into different subtypes, of which 2(1.2%) were CRF01_AE/A1, and the other 1 was CRF07_BC/CRF01_AE.
  
  
  CONCLUSIONS
  At least three HIV-1 subtypes including CRF01_AE, CRF07_BC were identified among MSM population in Xi'an city.
authors.affiliation: The Fourth Military Medical University, Xi'an 710032, China; Xi'an Center for Disease Control and Prevention.
authors.forename: Hailan
authors.initials: H
authors.lastname: Zhang
authors.affiliation: The Fourth Military Medical University, Xi'an 710032, China. Email: yanyping@fmmu.edu.cn.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Xi'an Center for Disease Control and Prevention.
authors.forename: Hengxin
authors.initials: H
authors.lastname: Li
authors.affiliation: The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Duan
authors.initials: D
authors.lastname: Li
authors.affiliation: Xi'an Center for Disease Control and Prevention.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wei
authors.affiliation: Xi'an Center for Disease Control and Prevention.
authors.forename: Haichao
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Xi'an Center for Disease Control and Prevention.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
mesh_terms: D000293:Adolescent; D000328:Adult; D002681:China / Q000453:epidemiology; D005838:Genotype; D015658:HIV Infections / Q000453:epidemiology*; D015497:HIV-1 / Q000145:classification*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D055815:Young Adult