Elevated antibody levels against the yeast Saccharomyces cerevisiae have been reported in sera from patients with Crohn's disease and not with ulcerative colitis. The aim of the study was to identify the nature of the epitopes supporting this antibody response. Whole cells from different S. cerevisiae strains were selected in immunofluorescence assay for their ability to differentiate the antibody responses of patients with Crohn's disease and ulcerative colitis. Their cell wall phosphopeptidomannans were then tested as antigen in enzymelinked immunosorbent assay (ELISA) against sera from 42 patients with Crohn's disease, 20 patients with ulcerative colitis, and 34 healthy controls. Graded chemical degradations were performed on the most reactive strain phosphopeptidomannan. The discriminating epitope was determined through gas-liquid chromatography-mass spectrometry. The greatest discrimination among patients with Crohn's disease, ulcerative colitis, and controls was obtained with Su1, a S. cerevisiae strain used in brewing of beer. ELISA directed against phosphopeptidomannan of this strain was 64% sensitive and 77% specific for discriminating Crohn's disease versus ulcerative colitis and 71% sensitive and 89% specific for Crohn's disease versus controls. Periodate oxidation and selective degradation demonstrated that the most important polysaccharide epitope was shared by both the acid-stable and the alkali-labile domains of the phosphopeptidomannan. The determination of oligomannose sequences of S. cerevisiae Su1 phosphopeptidomannans suggested that a mannotetraose, Man(133)Man(132)Man(132)Man, supported the serological response seen in Crohn's disease. Further identification of the immunogen eliciting this antibody response as a marker of the disease may help to understand its etiology.

Six monoclonal antibodies (MAbs) from various laboratory sources (EB-CA1, EB-CA2, H5, AF1, C6, and 5B2), reacting with the polysaccharidic moieties of Candida albicans mannoproteins, were used for epitope mapping by an enzyme-linked immunosorbent assay (ELISA) with neoglycolipids and by Western blotting (immunoblotting) of a C. albicans germ tube extract. The ELISA involved neoglycolipids constructed from three families of oligomannosides released by sequential depolymerization of C. albicans phosphopeptidomannan by acid hydrolysis (NGLH), 1-elimination (NGLO), and acetolysis (NGLA). All of the MAbs exhibited low reactivities against NGLO. MAbs EB-CA1, EB-CA2, and H5 reacted mainly against NGLA, and MAbs C6 and AF1 recognized mainly NGLH, whereas MAb 5B2 reacted with both families of neoantigens. When this method was compared with Western blotting, strong reactivity to NGLA was associated with the presence of epitopes shared by high-molecular-weight mannoproteins, whereas strong reactivity to NGLH was associated with a * Corresponding author.

The minimal epitope of an anti-Candida albicans mannan monoclonal antibody (MAb) EB-CA1, used to detect mannanemia in patient sera, was determined. MAb EB-CA1 exhibited reactivity with oligomannosides released from the mannan acid stable domain, converted into neoglycolipids (NGLs) and coated onto ELISA plates. Reactivity occurred with mannopentaose and higher oligomers, whereas mannotriose and mannotetraose were unreactive. MAb EB-CA1 binding to mannan acid stable mannopentaose NGL displayed a dose dependent and saturable specific reactivity curve whereas there was a complete absence of binding, even at high concentrations, with NGLs constructed from the L-1,2-linked mannopentaose derived from the mannan acid labile fraction. MAb EB-CA1 binding to acid stable mannopentaose NGL was inhibited by the homologous oligomannoside but not by mannotriose and mannotetraose. NMR analysis showed that mannotriose and mannotetraose contained exclusively K-1,2-linked D-mannopyranose units and that mannopentaose was a mixture of a mannopentaose K-1,2-linked and an isomer in which the fifth mannose was K-1,6-linked to the reducing unit of manno-K-1,2 tetraose. Western blot analysis has shown that MAb EB-CA1 epitope was expressed on a wide range of C. albicans manno-glycoconjugate as well as on manno-glycoconjugates of other pathogenic species of the genus Candida, viz. C. tropicalis, C. glabrata, C. parapsilosis and C. krusei. z

Kinetic analysis of candidosis patients' immunoglobulin G3 response has shown that reactivity towards beta(1-2)-linked mannan-derived oligomannosides was associated with the recognition through metaperiodate-sensitive epitopes of a 14- to 18-kDa Candida albicans antigen unreactive with concanavalin A.