Enhanced detection with an enzyme-linked immunosorbent assay of candida mannan in antibody-containing serum after heat extraction

Abstract

A double-antibody, solid-phase enzyme-linked immunosorbent assay was developed for detection of candida antigen(s) in serum and body fluids. The assay detected mannan purified from Candida albicans cells with a sensitivity of 1 ng/ml in buffer, but it was 1,000-fold less sensitive in pooled human serum. Because antibody appeared to be the major blocking factor in serum, a rapid and efficient heat-extraction method for recovering mannan from antibody-containing serum was devised. The assay detected antigenemia within 24 hr in all of 30 lethally infected rats, and antigenemia persisted until their deaths. Eight of 15 patients with documented or suspected candidiasis had antigenemia at levels ranging from 5 to greater than 1,000 ng/ml.