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 asse ssed 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, Brazi l. An attempt to evaluate HIV incidence was carried out using a dual 'sensi tive/less sensitive' testing strategy. Study design: Cross-sectional evalua tion of 175 IDUs. Serostatus for HIV-1 and HTLV-I,II were established by en zyme-linked immunosorbent assays, and confirmed by western blot. The dual t esting strategy aimed to estimate HIV-1 incidence rates. Differentiation be tween HTLV-I and -II was performed by western blot. DNA samples were polyme rase chain reaction amplified by a nested protocol, and HIV-1 subtyping was determined by heteroduplex mobility assay. Results: Forty-six and 29 sampl es 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 subtyp e, with seven of them showing the typical 'Brazilian B' pattern in the gp12 0 V3 loop, and ten were identified as F subtype. The use of less sensitive assays for HIV infection wrongly identified a deeply immunocompromised pati ent as an incident case. Conclusion: Moderately high seroprevalences were f ound for both HIV-1 and HTLV-I/II infections, HIV-1/HTLV-I co-infections be ing of special concern. A non-statistically significant higher prevalence o f F subtype was observed, when compared with the distribution of F/B subtyp es among Brazilian patients from other exposure categories. No recent HIV-1 infections were detected, but a limitation of the 'sensitive/less-sensitiv e' testing strategy was made evident. (C) 2001 Elsevier Science B.V. All ri ghts reserved.