Rapid whole blood assay for HIV-1 seropositivity using an Fab-peptide conjugate

A rapid whole blood test has been developed for circulating antibodies to human immunodeficiency virus type 1 (HIV-1), based on agglutination of autologous red blood cells. Evaluation of the test revealed that 100% of seropositive HIV-1 patients (both asymptomatic and AIDS cases) were detected (n = 94) with a specificity of 99.5% in healthy blood donors (n = 596). The assay uses an Fab fragment of a monoclonal antibody specifically directed against glycophorin (a transmembrane glycoprotein present on the surface of human red blood cells). This anti-red blood cell Fab is conjugated via the inter-heavy chain cysteines to a synthetic peptide corresponding to the immunodominant epitope of the HIV-1 viral coat protein gp41 (579-613). Addition of this reagent to 10 microliters of whole blood results in the Fab-peptide conjugate coating the red blood cells with peptide. In the presence of circulating antibodies to the HIV-1 peptide, red cell agglutination occurs within 2 min. The sensitivity and specificity of this reagent indicate that it is appropriate for use as a rapid diagnostic test for HIV-1 seropositivity.