CHARACTERIZATION OF CANDIDA-ALBICANS CELL-WALL ANTIGENS WITH MONOCLONAL-ANTIBODIES

The antigenic composition of Candida albicans is very complex. In orde r to study the antigenic relationship between blastoconidia and germ t ubes of C. albicans, we produced several monoclonal antibodies and ana lyzed their reactivity against cell wall antigens either in intact cel ls or in cells treated with dithiothreitol. Overall, four types of rea ctivity were found. Monoclonal antibodies 3D9 and 15C9 stained the ger m tubes only when tested by indirect immunofluorescence. However, they showed a different reactivity by immunoblotting. Monoclonal antibody 3D9 reacted with antigens with molecular masses of > 200 and 180 kDa s pecifically expressed in the germ tube. Monoclonal antibody 15C9 react ed with antigens of 87, 50, and 34 kDa present in the germ tube extrac t and with antigens of 92, 50, 34, and 32 kDa present in the blastocon idium extract. The reactivity of blastoconidia treated for different t imes with dithiothreitol with these monoclonal antibodies was also stu died by enzyme-linked immunosorbent assay. The reactivity of monoclona l antibody 3D9 did not significantly change during the cell wall extra ction. However, the reactivity of monoclonal antibody 15C9 was increas ed for blastoconidia extracted for 60 min and decreased markedly for b lastoconidia extracted for 120 min. Monoclonal antibody G3B was nonrea ctive by indirect immunofluorescence but reacted with antigens of 47 a nd 38 kDa present in the germ tube extract and with an antigen of 47 k Da present in the blastoconidium extract. Monoclonal antibody B9E stai ned both morphological phases by indirect immunofluorescence. By immun oblotting, it reacted with antigens of > 70 kDa present in the germ tu be extract and with antigens of > 63, 56, 47, and 38 kDa present in th e blastoconidium extract. Based on the results presented in this study , four types of antigens are described. Type I antigens are expressed on the outermost layers of the germ tube cell wall only. Type II antig ens are expressed both on the germ tube cell wall surface and within t he blastoconidium cell wall. Type III antigens are found within the ce ll wall of both blastoconidia and germ tubes. Type IV antigens are exp ressed on both the blastoconidium and germ tube surface. Two types mor e can be hypothesized for antigens expressed on the blastoconidium cel l surface and within the germ tube cell wall (type V) and for those ex pressed on the blastoconidium surface only (type VI).