Competitive EIA for anti-HIV-2 detection in The Gambia: use as a screening assay and to identify possible dual infections.

The performance of a competitive EIA for the detection of HIV-2-specific antibody utilising a viral lysate antigen was assessed over a 3 year period in The Gambia, West Africa, and compared with a commercially available assay, ELAVIA-2, using three panels of sera. An immunodominant region of the transmembrane glycoprotein of an HIV-2 isolate (ANT 53) was also cloned and expressed in E. coli as a beta-galactosidase fusion protein and the resulting recombinant protein substituted in place of the existing viral lysate antigen. Competitive EIAs were found to be both a specific and sensitive means of reliably determining the HIV-2 status of an individual with a high predictive value, particularly when a strategy of concordant positive results in the two EIAs was used. When either anti-HIV-2 competitive EIAs were used in conjunction with a competitive EIA for anti-HIV-1 detection it was possible in the vast majority of cases to identify the virus-type infecting an individual and speciate HIV-1 and HIV-2 infections. A few sera which showed similar regression profiles when diluted over a serial tenfold dilution steps were identified as possible dual infections.