Isolation and Purification of a Peptido-Rhamnomannan from the Yeast Form of Sporothrix Schenckii . Structural and Immunochemical Studies

Abstract

A peptido-rhamnomannan was isolated from the cells and culture medium of the human pathogenic fungus Sporothrix schenckii, grown in the yeast phase. It was purified by precipitation of its borate complex with hexadecyltrimethylammonium bromide and then by DEAE-Sephadex chromatography. The sugars in the polysaccharide were identified as d-mannose (50%) and l-rhamnose (33%). The amino acid composition of the peptide resembled that of the peptide moiety of other fungal peptido-polysaccharides. The polymer was almost entirely (91%) precipitated by concanavalin A and the ratio of mannose to rhamnose in the precipitate was unchanged, showing that the sugars are components of the same polymer. Methylation analysis and partial acid hydrolysis showed that the basic structure of the polysaccharide is a peptido-mannan to which numerous l-rhamnose residues are attached. About 60% of the rhamnose residues could be preferentially removed by mild acid hydrolysis. The peptido-rhamnomannan precipitated with the sera of individuals (3) with sporotrichosis. Sera from a small number of patients with other fungal diseases and from normal individuals did not precipitate within the sensitivity limits of the method. The specificity of two of the sera were examined in more detail by studying their cross-reactions with other fungal mannans.