Epitope mapping Candida albicans proteinase (SAP 2)

The continuous epitopes of Candida albicans proteinase SAP 2 were derived by epitope mapping with sera from patients with oral candidiasis (n = 3), necropsy-proven disseminated candidiasis (n = 5), paired sera from patients who had recovered from blood culture-proven disseminated candidiasis (n = 3) and infection due to Candida parapsilosis (n = 2) and Candida tropicalis (n = 2). In C. albicans infection, IgM identified epitopes in amino acid positions 57-61 (QAVPV), 146-151 (SQGTLY) and 346-351 (PYDKCQ) and IgG at position 386-390 (VKYTS). For C. tropicalis IgM and IgG were positive for the same epitopes whilst IgG also detected epitopes at 78-83 (SNNQKL) and 159-164 (GVSIKN). For C. parapsilosis, IgM was positive for SNNQKL and IgG detected no epitopes. Reactivity of two of the epitopes as peptides KTSKRQAVPVTL and SLAQVKYTSASSI was confirmed in an indirect ELISA. At a cut-off optical density of 0.4, IgM against either peptide was associated with survival but present in only about half of the sera (n = 60) from patients who recovered from disseminated candidiasis whilst IgG levels were disappointing. Human recombinant antibodies from a patient who had recovered from disseminated candidiasis against either of these peptides had no activity in a lethal mouse model of candidal infection.