Candida parapsilosis-specific monoclonal antibodies and their use for detection of Candida antigens in experimental systemic candidiasis

Candida parapsilosis has emerged as one of the most common causes of bloodstream infection worldwide. The diagnosis of invasive candidiasis etiological agents to the species level remains a laboratory and clinical challenge. Thus, specific monoclonal antibodies to detect systemic candidiasis and to identify Candida virulence factors and associated pathogenesis through immunohistochemistry would be very useful. Inbred Balb/c mice were immunized with C. parapsilosis antigens, and blood was checked for the presence of reactive antibodies using ELISA. Fusion was performed using the harvested spleen cells and NS1 myeloma cells, and the clones were screened for the presence of antibody producing hybrid cells by dot-blot. The 1B11 clone secreted IgG2a monoclonal antibody that was reactive with the C. parapsilosis antigen at MW of 59 kDa and cross-reacted with C. tropicalis but not with other fungal and bacterial antigens tested. Another 3D1 clone secreted IgG1 monoclonal antibody that was reactive with C. parapsilosis antigen at MW of 30 kDa. The 3D1 monoclonal antibody was found to be species specific. Experimental systemic candidiasis in rats was induced through intravenous injection of C. parapsilosis, and all the vital organs were collected for immunohistochemistry study. These monoclonal antibodies were reactive against surface epitopes on the yeast cells, pseudohyphae, and immune complexes in tissue sections. Sandwich ELISAs using these antibodies were developed and were able to detect circulating antigens in experimental candidiasis in rats at 0.2 μg/μL. These monoclonal antibodies may have potential as primary capture antibodies for the development of rapid diagnostic test for human systemic fungal infection.