Navegando por Palavras-chave "sialic acids"

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    Anionogenic groups and surface sialoglycoconjugate structures of yeast forms of the human pathogen Paracoccidioides brasiliensis
    (Soc General Microbiology, 1998-02-01) Soares, Regina MA; Silva-Filho, Fernando Costa; Rozental, Sonia; Angluster, Jayme; Souza, Wanderley de; Alviano, Celuta Sales; Travassos, Luiz Rodolpho [UNIFESP]; Universidade Federal do Rio de Janeiro (UFRJ); Univ Estadual Norte Fluminense; Universidade Federal de São Paulo (UNIFESP)
    The surface anionogenic groups and sialoglycoconjugate structures of Paracoccidioides brasiliensis yeast forms were analysed by cell microelectrophoresis, binding assays with lectins and viral particles, ultrastructural cytochemistry, enzymic digestion and flow cytofluorimetry. P. brasiliensis yeast forms, particularly the budding primordia, reacted strongly with cationized ferritin. Binding assays showed that the reaction with sialic-acid-specific Limax flavus lectin (LFA) was distributed over the entire P. brasiliensis cell wall. Treatment of yeast forms with neuraminidase significantly reduced their negative surface charge and LFA labelling, which suggests that sialic acid residues are major anionogenic groups exposed on the P. brasiliensis surface. Furthermore, after neuraminidase treatment, labelling with Arachis hypogaea (peanut) agglutinin increased due to unmasking of subterminal beta-D-galactopyranosyl residues. The sialic acid linkages to galactose are alpha 2,6 and alpha 2,3 as assessed, respectively, by fungal attachment to M1/5 and M1/5 HS8 strains of influenza A virus and binding of Sambucus niger and Maackia amurensis agglutinins. The alpha 2,6 linkage clearly predominated in both experiments. Flow cytofluorimetry analysis revealed the heterogenicity of P. brasiliensis yeast cell populations, which comprised young and mature budding yeasts. Both express binding sites to LFA and Limulus polyphemus agglutinin.
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    Polyclonal B-cell activation by Neisseria meningitidis capsular polysaccharides elicit antibodies protective against Trypanosoma cruzi infection in vitro
    (Wiley-Blackwell, 1996-01-01) Oliveira, T. G.; Milani, SR; Travassos, L. R.; Universidade Federal de São Paulo (UNIFESP)
    A hyperimmune rabbit antiserum against group C Neisseria meningitidis agglutinated and lysed Trypanosoma cruzi metacyclic trypomastigotes in a complement-mediated reaction. Immunization of rabbits with the purified polysaccharide C from N. meningitidis and of human volunteers with the AC-polysaccharide vaccine against meningitis also resulted in antibody production cross-reactive with T. cruzi infective forms, the rabbit antibodies bound to parasites, lysed metacyclic forms, and recognized several components from lysates of cell-derived trypomastigotes. the sera from six human volunteers reacted with cell-cultured trypomastigotes in vitro, lysed these forms, and recognized glycoconjugates migrating diffusely on the top of immunoblots. One serum also reacted with the isolated mucin-like glycoconjugate carrying the Ssp-3 epitope from cell-derived trypomastigotes, but treatment with sialidase did not abolish this reactivity. the anti-AC human antiserum also protected against HeLa cell infection and markedly decreased the number of parasites liberated after cell burst. the polyclonal response that resulted from human immunization with N. meningitidis polysaccharides A and C comprised trypanolytic antibodies that recognized nonsialylated epitopes expressed on infective forms of the parasite. It is suggested that human AC vaccination could be potentially helpful as an adjuvant to a specific immunotherapy of Chagas disease, developed with native or recombinant antigens of the parasite. (C) 1996 Wiley-Liss, Inc.
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    Sialic acids in fungi: A minireview
    (Kluwer Academic Publ, 1999-09-01) Alviano, C. S.; Travassos, L. R. [UNIFESP]; Schauer, R.; Univ Kiel; Universidade Federal do Rio de Janeiro (UFRJ); Universidade Federal de São Paulo (UNIFESP)
    The increasing number of reports on the presence of sialic acids in fungi (N-acetyl, N-glycolyl-and 5,9-N,O-diacetyl neuraminic acids) based on direct and indirect evidence warrants the present review. Formerly suggested as sialidase-sensitive sources of anionic groups at the cell surface of fungal species grown in chemically defined media (e.g., Fonsecaea pedrosoi), sialic acids have also been found in Sporothrix schenckii, Paracoccidioides brasiliensis, Cryptococcus neoformans and recently, in Candida albicans. Methods used involved adequate hydrolysis and extraction procedures, HTPLC, gas-chromatography, colorimetry, mass spectroscopy, sialidase-sensitive lectin and influenza virus binding. Apart from protecting fungal cells against phagocytosis (S. schenckii, C. neoformans) and playing a cellular structural role (F. pedrosoi), other biological functions of sialic acids are still being investigated.