NOVEL ANTIGENIC DETERMINANTS FROM PEPTIDORHAMNOMANNANS OF SPOROTHRIX-SCHENCKII

Antisera were raised in rabbits against acetone-dried yeast-like and mycelium forms of Sporothrix schenckii. These antisera were tested for immunoprecipitation of peptido-rhamnomannans isolated from both cell types. Both antisera reacted strongly with S.schenckii peptidorhamnomannans, but the reactions were weak with beta-eliminated peptidopolysaccharides. These antisera did not recognize the Saccharomyces cerevisiae mannoprotein, and reacted poorly with Ceratocystis (Ophiostoma) stenoceras cell wall glycopeptides. Since beta-eliminated glycopeptides were poorly reactive, we investigated the activity of O-glycosidically linked oligosaccharides which were liberated from the peptidorhamnomannans by mild alkaline hydrolysis, using a hapten inhibition test. The rates of inhibition showed that the immunodominant epitopes in O-linked tetra- and pentasaccharides had the following novel structures: alpha-L-Rhap (1-->4)-alpha-D-GlcpA and alpha-L-Rhap(1-->4)-[alpha-L-Rhap(1-->2)]alpha-D-GlcpA. Results suggest that peptidorhamnomannans or synthetic antigens bearing these epitopes should be used for the specific detection of anti-S.schenckii antibodies rather than the long-chain N-linked polysaccharides.