Résumé
In order to assess the molecular epidemiology of HIV-1 in two neighboring cities located near the epicenter of the HIV-1 epidemics in Brazil (Santos and São Paulo), we investigated 83 HIV-1 strains obtained from samples collected in 1995 from intravenous drug users. The V3 through V5 region of the envelope of gp 120 was analyzed by heteroduplex mobility analysis. Of the 95 samples, 12 (12.6 percent) were PCR negative (6 samples from each group); low DNA concentration was the reason for non-amplification in half of these cases. Of the 42 typed cases from São Paulo, 34 (81 percent, 95 percent confidence limits 74.9 to 87.0 percent) were B and 8 (19 percent, 95 percent confidence limits 12.9 to 25.0 percent) were F, whereas of the 41 typed cases from Santos, 39 (95 percent, 95 percent confidence limits 91.6 to 98.4 percent) were B and 2 (5 percent, 95 percent confidence limits 1.6 to 8.4 percent) were C. We therefore confirm the relationship between clade F and intravenous drug use in São Paulo, and the presence of clade C in Santos. The fact that different genetic subtypes of HIV-1 are co-circulating indicates a need for continuous surveillance for these subtypes as well as for recombinant viruses in Brazil