[Detection of human immunodeficiency virus antigen both free and in immune complexes]

The aim of this work was to increase sensitivity in the detection of antigens from HIV-infected patients, through a process of immune complex dissociation without loss of antigenicity. 500 microliters of sera were mixed with 100 microliters of PEG 12%, stored one night in refrigerator, and centrifuged at 2000 g during 20 minutes. 200 microliters of buffer AcH/Ac- (pH 3.5) were added to the sediment, and incubated at 37 degrees C during one hour with periodic shaking. This was neutralized with 100 microliters of buffer TRIS/CIH (pH 8.6). The antigen was investigated in the original sample, supernatant and sediment. Samples of 105 patients with positive serology, confirmed by Western Blot following CDC criteria, were processed. The antigen was detected in 62 (59%) samples precipitated with PEG, but only 35 (33%) when conventional methods were used. Applying statistics X2: 13.97, P < 0.001, a highly significant association can be observed between PEG dissociation treatment and antigen detection. 27 negative sera by the standard method became positive in the whole sediment, and only 8 in the supernatant. In addition, 40 negative sera were processed, which had not become positive for the antigen by PEG treatment.