title: High prevalence of CXCR4 usage among treatment-naive CRF01_AE and CRF51_01B-infected HIV-1 subjects in Singapore.
abstract: BACKGROUND
  Recent studies suggest HIV-1 inter-subtype differences in co-receptor usage. We examined the correlation between HIV-1 subtype and co-receptor usage among treatment-naïve HIV-1 subjects in Singapore. Additionally, we investigated whether the subtype co-receptor association was influenced by stage of infection.
  
  
  METHODS
  V3 sequences of HIV-1 envelope protein gp120 were obtained from 110 HIV treatment-naïve patients and genotypic co-receptor tropism determination was performed using Geno2pheno. Two false-positive rate (FPR) cut-offs, 10% and 5.75% were selected for tropism testing.
  
  
  RESULTS
  Subtype assignment of viral strains from 110 HIV-infected individuals based on partial sequencing of HIV-1 pol, gp120 and gp41 were as follows: 27 subtype B, 64 CRF01_AE, 10 CRF51_01B, and 9 other subtypes. At FPR=10%, 10 (100%) CRF51_01B-infected subjects and 26 (40.6%) CRF01_AE-infected subjects had CXCR4-using virus, compared to 7 (25.9%) subtype B subjects and 1 (11.1%) CRF33_01B-infected subject (P < 0.001). At FPR=5.75%, 10 (100%) CRF51_01B-infected subjects and 20 (31.3%) CRF01_AE-infected subjects had CXCR4-using virus, compared to 4 (14.8%) subtype B and 1 (11.1%) CRF33_01B-infected subjects (P < 0.001). Among those with evidence of seroconversion within 2 years prior to study enrolment, 100% of CRF51_01B-infected subjects had CXCR4-using virus, independent of Geno2pheno FPR.
  
  
  CONCLUSIONS
  CRF51_01B and CRF01_AE-infected individuals have higher prevalence of CXCR4-usage compared to subtype B infected individuals. Further studies examining these differences could help optimise the use of CCR5-antagonist in populations with these subtypes, and increase our understanding of HIV-1 biology.
authors: Institute of Infectious Disease and Epidemiology, Communicable Disease Centre, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors: Kah Ying
authors: KY
authors: Ng
authors: Kuan Kiat
authors: KK
authors: Chew
authors: Palvinder
authors: P
authors: Kaur
authors: Joe Yap
authors: JY
authors: Kwan
authors: Wei Xin
authors: WX
authors: Khong
authors: Li
authors: L
authors: Lin
authors: Arlene
authors: A
authors: Chua
authors: Mei Ting
authors: MT
authors: Tan
authors: Thomas C
authors: TC
authors: Quinn
authors: Oliver
authors: O
authors: Laeyendecker
authors: Yee Sin
authors: YS
authors: Leo
authors: Oon Tek
authors: OT
authors: Ng
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D005838:Genotype; D015699:HIV Envelope Protein gp120 / Q000235:genetics; D015658:HIV Infections / Q000453:epidemiology / Q000276:immunology / Q000821:virology*; D015497:HIV-1 / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D019713:Receptors, CCR5 / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism*; D012846:Singapore / Q000453:epidemiology; D056189:Viral Tropism; D055815:Young Adult
chemical_list: D015699:HIV Envelope Protein gp120; D019713:Receptors, CCR5; D019718:Receptors, CXCR4