Diagnostic utility of a microarray based on 11 proteins of Candida albicans for the diagnosis of invasive candidiasis

Objective. The purpose of this study was to set up a protein microarray test based on 11 proteins of C. albicans for the detection of IgG antibodies in sera from patients with invasive candidiasis (IC) and determine its diagnostic utility. Methods and patients. The microarray was set up with 10 C. albicans recombinant proteins: Eno1, Als3-N, Hwp1-N, Eno1-RM, Bgl2, Grp, Pgk1, Fba, Pdc, Adh1, and an enolase purified from a dithiothreitol-extract of cell walls from C. albicans mycelial phase (CW-Eno). Antigens, IgG standard curve, and controls were printed onto glass slides using computer controlled high speed robotics. The arrays were processed with sera from IC and control patients and then fluorescence labeled secondary antibodies were added. The signal captured by each spot was detected by a laser scan reader and quantified. When possible, the cut-off values werecalculated as mean mass of antibody detected in the control group sera plus 2 times the standard deviation. Twenty three sera from 15 patients with proven IC due to C. albicans and 33 sera from 28 patients at risk for IC but without clinical or microbiological data confirming a fungal infection (control group) were studied. Results. The performance of the microarray assay for each antigen is shown in Table 1. The best results were obtained with CW-Eno, showing a sensitivity and a specificity of 80 and 96.43%, respectively. Pgk1, Grp and Eno1 exhibited lower sensitivity values (33-47%), but their specificity reached values equal or greater than 93% Also, for all the other antigens, the specificity was very high with values above 96%. Furthermore, we clustered those antigens which separately had returned the best sensitivity. As shown in Table 2, the clustering raised the sensitivity up to 100%, while the specificity ranged between 85 and dropped to 89% . Conclusions. The detection of serum IgG antibodies against proteins of C. albicans by a protein microarray exhibited moderate diagnostic utility values when assessed independently, being CW-Eno the main exception. However, when considering the microarray results either as a whole or as clusters of selected proteins (CW-Eno, Pgk1, Eno1 and Grp; or CW-eno and Pgk1), the system proved to be an efficient diagnostic tool for IC. Further studies with a larger number of patients are needed to confirm the results of the present study.