EPIDEMIOLOGIC AND MOLECULAR CHARACTERISTICS OF HIV-INFECTION IN GABON, 1986-1994

Objective: To describe trends in the prevalence of HIV-1 infection in different populations in Gabon, and the molecular characteristics of c irculating HIV strains. Methods: Data were collected on HIV prevalence through sentinel surveillance surveys in different populations in Lib reville (the capital) and in Franceville. In Libreville, a total of 70 82 individuals (hospitalized patients, tuberculosis patients, pregnant women, asymptomatic adults, prisoners) were recruited between 1986 an d 1994. In Franceville, we tested 771 pregnant women and 886 healthy a symptomatic adults (1986-1988). Sera were screened for HIV antibodies by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot or line immunoassay (LIA). Reactive samples in ELISA were tested for the presence of antibodies to HIV-1 group O viruses by ELISA using V3 peptides from HIV-1(ANT-70) and HIV-1(MVP-5180) followed by confir mation by LIA and a specific Western blot. Seventeen HIV-1 strains wer e isolated (1988-1993) and a 900 base-pair fragment encoding the env r egion containing V3, V4, V5 and beginning of gp41 was sequenced and a phylogenetic tree was constructed. Results: HIV prevalence was relativ ely low and remained stable (0.7-1.6% in pregnant women, 2.7-2.2% in t he general population). The prevalence was also stable among prisoners (2.1-2.6%). Among hospitalized and tuberculosis patients prevalence w as higher and increased (1.8-12.7% and 1.5-16.2%, respectively). On ly three sera had antibodies to HIV-1 group O. The 17 HIV-1 strains repr esent six different genetic subtypes including type O. Conclusion: Our data from 1986 to 1994 show a stable and low HIV prevalence in Gabon, and a high genetic diversity of HIV-1 strains. This, also observed in Cameroon, is in contrast to that found elsewhere in Africa. Differenc es in rate of spread of HIV infection are probably explained by interp lay between numerous factors. The role of different HIV subtypes in th e dynamics of the HIV epidemic should be examined further.