Abstract

Serological methods are the main methods in diagnosis of human immunodeficiency virus (HIV)-1 and HIV-2 infection. The western Blot (WB) is considered as a gold standard test for the confirmation of enzyme-linked immunosorbent assay (ELISA) and/or other rapid screened reactive results samples in the diagnosis of HIV infection. However, problems of WB, particularly in regard to the significance of indeterminate results, still remain. To develop and evaluate a recombinant HIV-1/2 antigens-based line immunoassay as confirmatory assay for HIV-1 and HIV-2 infections is the objective of this study. HIV-1 envelope proteins (gp160, gp120, gp41), HIV-1 integrase protein (p31), HIV-1 gag proteins (p24, p17) and HIV-2 envelope protein (gp 36) were cloned and expressed inEscherichia coli. All recombinant HIV antigens were purified and immobilized on nitrocellulose membranes and applied in a line immunoassay, which supplement detected anti-HIV antibodies in a single strip. Specific antibodies to these antigens in human sera were revealed using an alkaline phosphatase labeled anti-human immunoglobulin G (IgG) as second antibody. Two anti-human IgG lines were used as a control for the addition of serum. Positive or negative results were determined by visual comparison of the antigen lines intensity with the two control lines. The recombinant HIV antigens-based line immunoassay identified seropositive individuals with a high degree of accuracy; none of the HIV-seropositive subjects yielded a negative result. Reactivity with these antigens, demonstrated 100% sensitivity and specificity in distinguishing seronegative from seropositive sera. This line immunoassay was much more sensitive and specific than WB. In particular, the line immunoassay allowed for a significant reduction in the number of indeterminate results and for more accurate distinction between HIV-1 and/or HIV-2 infections.

Key words: HIV antibodies, line immunoassay, recombinant antigens, confirmatory test.