Detection of Antibody to Candida albicans Proteinase in Sera from C. albicans - Cultured Patients and Healthy Controls

ABSTRACT

To investigate whether anti-Candida proteinase antibody could be a diagnostic marker, we examined seroreactivity to proteinase in sera from 90 healthy controls and 8 of C. albicans culture-positive patients. Previously we purified proteinases of C. albicans, C. tropicalis, and C. parapsilosis using a series of chromatographic steps consisting of DEAE- Sepharose, Sephacryl S-200, and size-exclusion HPLC. ELISA and Western blot technique were adopted to examine seroreactivity of C. albicans proteinase with sera. On ELISA, the seroreactivities of healthy controls and C. albicans-cultured patients were 0.601 +- 0.014 (mean+SEM), and 0.695 +- 0.079, respectively (P=0.084, t-test). In C. albicans-cultured patients, the positive rate was 62.5% (5/8) and the positive rate of healthy controls was 39% (35/90). On Western blot analysis, C. albicans proteinase molecule was blotted by all sera tested. But the intensity of blotted band was different with the same dilution of sera; the intensity of C. albicans proteinase molecule band blotted by 2 sera of 3 healthy control's sera was distinctively lower than that by C. albicans-cultured patients sera. However, all sera including C. albicans-cultured patient's sera did not blot the proteinase secreted by C. tropicalis and C. parapsilosis. It is necessary to collect sequential sera of patients with candidiasis and to establish a cut-off value for ELISA or serum dilution for Western blot analysis that will give reliable test sensitivity and specificity.