Characterization of two monoclonal antibodies against secretory proteinase of Candida tropicalis DSM 4238.

Two murine IgM monoclonal antibodies (mAb; MT1 and MT2), which were produced against the secretory aspartic proteinase of Candida tropicalis DSM 4238, are described. Both antibodies reacted with the native and denatured conformations of the homologous proteinase antigen but showed different patterns of reactivity with other related proteinases (Candida albicans CBS 2730, serotype A; C. albicans ATCC 48867, serotype B; Candida parapsilosis DSM 4237) and with porcine pepsin. Neither of the antibodies inhibited the proteolytic activity of the homologous enzyme. MT1 also reacted with mannoproteins of C. tropicalis DSM 4238 and C. albicans CBS 2730 and immunofluorescence revealed that this antibody bound to the surface of blastoconidia and pseudomycelia of these two Candida species. A reaction with blastoconidia only was observed with C. albicans serotype B. MT1 also reacted weakly with Candida guilliermondii, but not with C. parapsilosis, Candida glabrata, Candida krusei or Candida kefyr. MT2 did not bind to fungal surfaces. Preliminary experiments suggested that mAb MT1 may recognize a carbohydrate epitope, while MT2 binds to an epitope consisting of the protein part of the enzyme. The two antibodies were used in an ELISA for the detection of proteinase antigen. ELISA with MT1 or MT2 as coating antibodies and a specific protein epitope recognizing mAb-biotin conjugate was able to detect 4 ng ml-1 of antigen. Trials with 26 sera from fungemic patients and 14 sera from controls suggest that MT2 is of potential value in antigen-directed serodiagnosis.