title: Retrovirus infections in a sample of injecting drug users in Rio de Janeiro City, Brazil: prevalence of HIV-1 subtypes, and co-infection with HTLV-I/II.
abstract: BACKGROUND
  Retrovirus infections among injecting drug users (IDUs), a core at-risk population for both HIV-1 and HTLV-I/II infections in Brazil, were assessed within an ongoing cooperative research.
  
  
  OBJECTIVE
  The study assessed the seroprevalences of HIV-1 and HTLV-I/II infections, as well as the prevalence of HIV-1 subtypes in a sample of IDUs from Rio de Janeiro, Brazil. An attempt to evaluate HIV incidence was carried out using a dual 'sensitive/less sensitive' testing strategy.
  
  
  METHODS
  Cross-sectional evaluation of 175 IDUs. Serostatus for HIV-1 and HTLV-I/II were established by enzyme-linked immunosorbent assays, and confirmed by western blot. The dual testing strategy aimed to estimate HIV-1 incidence rates. Differentiation between HTLV-I and -II was performed by western blot. DNA samples were polymerase chain reaction amplified by a nested protocol, and HIV-1 subtyping was determined by heteroduplex mobility assay.
  
  
  RESULTS
  Forty-six and 29 samples were found to be, respectively, positive for HIV-1 and HTLV-I/II, 15 of them co-infected by both viruses. Among HTLV-I/II-infected patients, 75.9% were infected by HTLV-I. Thirty-one HIV samples were identified as B subtype, with seven of them showing the typical "Brazilian B" pattern in the gp120 V3 loop, and ten were identified as F subtype. The use of less sensitive assays for HIV infection wrongly identified a deeply immunocompromised patient as an incident case.
  
  
  CONCLUSIONS
  Moderately high seroprevalences were found for both HIV-1 and HTLV-I/II infections, HIV-1/HTLV-I co-infections being of special concern. A non-statistically significant higher prevalence of F subtype was observed, when compared with the distribution of F/B subtypes among Brazilian patients from other exposure categories. No recent HIV-1 infections were detected, but a limitation of the "sensitive/less-sensitive" testing strategy was made evident.
authors.affiliation: Laboratory of AIDS and Molecular Immunology, Department of Immunology, Oswaldo Cruz Institute, FIOCRUZ (UNAIDS Collaborative Centre), Av. Brasil, 4365 Manguinhos, 21045-900 Rio de Janeiro, Brazil.
authors.forename: M L
authors.initials: ML
authors.lastname: Guimarães
authors.forename: F I
authors.initials: FI
authors.lastname: Bastos
authors.forename: P R
authors.initials: PR
authors.lastname: Telles
authors.forename: B
authors.initials: B
authors.lastname: Galvão-Castro
authors.forename: R S
authors.initials: RS
authors.lastname: Diaz
authors.forename: V
authors.initials: V
authors.lastname: Bongertz
authors.forename: M G
authors.initials: MG
authors.lastname: Morgado
mesh_terms: D000328:Adult; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000150:complications / Q000453:epidemiology* / Q000821:virology; D015528:HIV Seroprevalence; D015497:HIV-1 / Q000145:classification*; D015490:HTLV-I Infections / Q000150:complications / Q000453:epidemiology*; D015491:HTLV-II Infections / Q000150:complications / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D015819:Substance Abuse, Intravenous / Q000150:complications*