Production of hybrid phage displaying secreted aspartyl proteinase epitope of Candida albicans and its application for the diagnosis of disseminated candidiasis.

The secreted aspartyl proteinases (Saps) of Candida albicans have been implicated as immunodominant antigens and virulence factors associated with adherence and tissue invasion. A hybrid phage displaying the Sap epitope VKYTS was constructed by cloning the corresponding DNA fragments into the pfd88 vector. Similar to native Sap, the phage-displayed epitope showed reactivity to sera from mice and patients with systemic C. albicans infection but not from those with oropharyngeal candidiasis and healthy individuals on Western blot. Furthermore, a new enzyme-linked immunosorbent assay was developed to detect the anti-Sap antibody with hybrid phage displaying Sap epitope VKYTS that can be recognised by anti-Sap antibodies. Sequential sera were tested from patients and mice with systemic candidiasis and oropharyngeal candidiasis, and serum samples from healthy individuals were also included. The sensitivity and specificity were 77% and 88.3% for experimental mice, respectively. These values reached 60% and 85%, respectively, for human patients. These data indicate this phage-displayed epitope as an effective and less expensive reagent would be a valuable probe for the detection of specific Sap antibody in the sera of patients and mice with systemic C. albicans infection.