Performance characteristics of a novel immunoassay based on hybrid Ty virus-like particles (Ty-VLPs): rapid differentiation between HIV-1 and HIV-2 infection.

Recombinant antigens containing all or parts of the HIV-1 proteins p24, Nef and gp41 and HIV-2 gp36 have been purified and used to develop a rapid immunoassay to detect and differentiate between HIV-1 and HIV-2 antibodies in a single test. The antigens were produced as particulate fusion proteins by exploiting the ability of a protein encoded by the yeast retrotransposon Ty to assemble into virus-like particles (Ty-VLPs). Hybrid HIV: Ty-VLPs carrying each of the antigens were applied to nitrocellulose strips at specified locations in a slot-blot format and then used to detect antibodies present in human serum and plasma samples of diverse geographical origin. Previously confirmed HIV-1- and HIV-2-positive samples were readily and reliably identified. The assay was used to identify a case of HIV-2 infection in an African woman who had been resident in the Oxford region for the last 3 years and to analyse the prevalence of anti-HIV antibodies in a longitudinal study of seroconverting patients. We also demonstrate that the assay works efficiently with whole blood.