CLINICAL UTILITY OF AN ENHANCED HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 P24 ANTIGEN CAPTURE ASSAY

The presence of p24 core antigen in the serum of individuals with huma n acquired immunodeficiency syndrome has been used as one of the impor tant prognostic markers of HIV-1 infection and also as an end point in evaluating antiviral drugs and vaccines. Unfortunately the majority o f p24 antigen present in serum exists as an antigen-antibody complex a nd is not detected with the commercial kits currently available to mea sure p24 antigen. In this study, we report a simple procedure utilizin g treatment of serum samples with glycine buffer (pH 1.85) to dissocia te antigen-antibody complexes prior to assaying for p24 antigen. A 300 % increase in the number of p24-reactive samples and a 3- to 12-fold i ncrease in the quantity of antigen detected were observed when samples were pretreated with 1.5 M glycine buffer (pH 1.85) for 1 hr. Glycine treatment of samples did not result in nonspecific positive tests and samples previously shown to be reactive remained positive. In reconst ruction experiments the release of antigen was found to be inversely p roportional to the amount of p24 antibody present in the serum. The pe rcentage of HIV-1-infected patients positive for p24 antigen was clear ly a function of CD4 count. Forty-nine percent of patients with more t han 500 CD4 cells and 100% of patients with less than 200 CD4 were p24 positive. The improved sensitivity for detection of p24 provided by t his procedure enhances our understanding of the pathogenesis of AIDS b y showing that the majority of patients with HIV-1 infection is p24 po sitive and facilitates the analysis of data obtained in clinical trial s involving anti-HIV compounds.