ANIONOGENIC GROUPS AND SURFACE SIALOGLYCOCONJUGATE STRUCTURES OF YEAST FORMS OF THE HUMAN PATHOGEN PARACOCCIDIOIDES-BRASILIENSIS

The surface anionogenic groups and sialoglycoconjugate structures of P aracoccidioides brasiliensis yeast forms were analysed by cell microel ectrophoresis, binding assays with lectins and viral particles, ultras tructural cytochemistry, enzymic digestion and flow cytofluorimetry. P . brasiliensis yeast forms, particularly the budding primordia, reacte d strongly with cationized ferritin. Binding assays showed that the re action with sialic-acid-specific Limax flavus lectin (LFA) was distrib uted over the entire P. brasiliensis cell wall. Treatment of yeast for ms with neuraminidase significantly reduced their negative surface cha rge and LFA labelling, which suggests that sialic acid residues are ma jor anionogenic groups exposed on the P. brasiliensis surface. Further more, after neuraminidase treatment, labelling with Arachis hypogaea ( peanut) agglutinin increased due to unmasking of subterminal beta-D-ga lactopyranosyl residues. The sialic acid linkages to galactose are alp ha 2,6 and alpha 2,3 as assessed, respectively, by fungal attachment t o M1/5 and M1/5 HS8 strains of influenza A virus and binding of Sambuc us niger and Maackia amurensis agglutinins. The alpha 2,6 linkage clea rly predominated in both experiments. Flow cytofluorimetry analysis re vealed the heterogenicity of P. brasiliensis yeast cell populations, w hich comprised young and mature budding yeasts. Both express binding s ites to LFA and Limulus polyphemus agglutinin.