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

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. Study design: 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. Conclusion: 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. (C) 2001 Elsevier Science B.V. All rights reserved.State Univ Rio de Janeiro, Ctr Drug Abuse Treatment & Res NEPAD, Rio de Janeiro, BrazilFIOCRUZ, UNAIDS Collaborat Ctr, Goncalo Moniz Res Ctr, Adv Publ Hlth Lab, Salvador, BA, BrazilUniversidade Federal de São Paulo, Lab Retrovirol, São Paulo, BrazilUniversidade Federal de São Paulo, Lab Retrovirol, São Paulo, BrazilWeb of Scienc