Serologic and genetic characterization of HIV type 1 subtypes on Reunion Island

The aim of this study was to determine the HN subtypes present on Reunion I sland, a French island located in the Indian Ocean, where the first case of AIDS was diagnosed in 1987. Paired sera and blood samples were collected b etween September 1996 and September 1997 from 53 HIV-1-positive patients. S ubtyping was performed by serotyping with a previously described subtype-sp ecific enzyme immunoassay (SSEIA) and by genotyping with the heteroduplex m obility assay (HMA), When samples gave uninterpretable results with either of the methods, or discordant results, the V3 env region was sequenced and genetic subtypes were determined by phylogenetic analysis, Genetic subtypin g showed that 48 of 53 patients were infected with HIV-1 subtype B (90.5%). This high prevalence of subtype B on Reunion Island is probably due to the regular exchanges with metropolitan France. The other five patients were i nfected with subtype A (9.5%); they had been directly linked to African pop ulations. Of the 48 subtype B samples, 44 (91.7%) were correctly subtyped b y SSEIA and 43 (89.6%) by HMA, However, the SSEIA did not allow the subtypi ng of A strains in three of five patients. Thus, the SSEIA could be an alte rnative routine technique for screening subtype B versus nonsubtype B HIV-1 strains.