Characterization of protein and mannan polysaccharide antigens of yeasts, moulds, and actinomycetes.

Abstract

Antigens in coccidioidin were compared with purified subfractions via tandem immunoelectrophoresis (IEP) and by a combination of advancing line and crossed IEP. Rocket IEP was suitable for titrating the reactions and showing the relationship between column fractions. These techniques required multicomponent antisera produced by hyperimmunization over many months and by the use of known standard migration pairs. The IEP variations were used to chart the development of antisera against coccidioidin factors, to monitor antigen purifications, and to test the immunochemical homogeneity of an isolated antigen. Mannose-based heteroglycans of Cryptococcus neoformans were recovered from the culture filtrate. After precipitation of the major viscous glucuronoxylomannan (GXM) with ethanol or cetyltrimethylammonium bromide, the supernate is reserved because it contains a galactoxylomannan (GalXM). After removal of glucuronic acid from the GXM, the resulting xylomannan of serotype A was amenable to 13C-nuclear magnetic resonance (NMR) spectrometry; it revealed nonreducing xylose, alpha-1,3-mannose, and alpha-1,2/1,3 disubstituted mannose, thus confirming by an independent means what was previously known. The characterization sequence of GalXM included: (1) gas-liquid chromatography (GLC) of neutral sugars as peracetylated aldononitriles; (2) methylation-fragmentation GLC mass spectrometry to determine the glycosidic linkages; and (3) 13C-NMR showing similarities to mannan of Saccharomyces cerevisiae. Affinity chromatography of the GalXM on concanavalin A separated the galactoxylo component from an adsorbed mannoprotein. Selection of monoclonal antibodies (MAbs) relies on presumptive enzyme immunoassays (EIAs) or radioimmunoassays for rapid screening of clones and for determination of isotypes; however, higher resolution confirmatory tests are needed to obtain MAbs of desired specificity. MAbs against Candida tropicalis mannan were labeled with horseradish peroxidase to use for detecting mannan in serum. MAbs against the partially purified "m" factor of histoplasmin were characterized by the enzyme-linked immunoelectro-transfer blot technique (EITB), revealing unsuspected complexity in the antigen. Secreted proteins of Nocardia asteroides were isoelectrically focused; three proteins, identified by EITB as promising to be specific for that actinomycete, were cut out of gels and used to immunize mice for production of MAbs. The fimbriae of Actinomyces viscosus and A. naeslundii that mediate lactose-reversible coagglutination with Streptococcus sanguis have been used to evoke MAbs.(ABSTRACT TRUNCATED AT 400 WORDS)