Evaluation of Polyclonal Antiserum Against Secretory Aspartyl Proteinase of Candida albicans as a Potential Serodiagnostic Tool for Invasive Candidiasis

Objective: Candida albicans ( C. albicans ) is an important agent of human Candidiasis. It expresses different virulence factors to evade host immunity and facilitate tissue invasion, including secretory aspartyl proteinases (Saps) secretion. For early and quick detection of systemic candidiasis, serological tests can be used instead of traditional blood cultures. This study aims to develop a polyvalent antiserum against (Sap) secreted by C. albicans and test its ability to be used as a diagnostic method in systemic Candida infections. Materials and Methods: Candida was obtained from clinical samples, and its different species were specifically characterized, and followed by C. albicans extracellular protease purification. Antiserum against purified (Sap1) was prepared by immunizing two rabbits with 10 µg of purified (Sap1) protein followed by three booster doses (once/week). Prepared anti (Sap1) antibodies were tested for the detection of (Sap1) in Candida species extracts by western blotting technique in addition to constructing indirect ELISA using prepared anti (Sap1) antiserum. Results: Among the tested species, C. albicans showed the highest extracellular proteases activity (18.6-fold with 2142 U/mg specific activity and 39% recovery). Polyclonal anti (Sap1) antiserum showed maximum ELISA titer and strong reactivity with many pathogenic Candida strains protein bands. Prepared antiserum had a greater binding capacity to pathogenic than non-pathogenic Candida strains and reacted strongly with pathogenic Candida strains even at low dilution. Conclusion: Our findings suggested that the prepared anti (Sap1) antiserum showed high productivity in detecting pathogenic Candida and could be used in serodiagnosis of invasive candidiasis.