Galactosaminogalactan secreted from Aspergillus fumigatus and Aspergillus flavus induces platelet activation |
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| Affiliation: | 1. Division of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020, Innsbruck, Austria;2. Department of Microbiology and Immunology, McGill University, Montréal, H3A 0G4, Canada;3. Department of Anesthesiology and Critical Care Medicine, 6020, Innsbruck, Austria;1. Department of Parasitology, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil;2. Department of Physics, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil;3. School of Medical Sciences, Universidade Federal de Mato Grosso, Cuiabá, MT, 78060-900, Brazil;1. Laboratory of Medical Investigation Unit 56, Division of Clinical Dermatology, Medical School, University of São Paulo, São Paulo, Brazil;2. Division of Clinical Dermatology, Medical School, University of São Paulo, São Paulo, Brazil;3. Tropical Medicine Institute, University of São Paulo, São Paulo, Brazil;1. Department of Infection Control and Prevention, Kurume University School of Medicine, 67 Asahi-machi, Kurume City, Fukuoka 830-0011, Japan;2. Division of Clinical Research, Medical Mycology Research Center, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba 260-8673, Japan |
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| Abstract: | Platelets are meanwhile recognized as versatile elements within the immune system and appear to play a key role in the innate immune response to pathogens including fungi. Previous experiments revealed platelet activation by direct contact with the hyphal-associated polysaccharide galactosaminogalactan (GAG). Since secreted fungal products may also be relevant and trigger immune reactions or thrombosis, we screened culture supernatants (SN) of human-pathogenic fungi for their capacity to activate platelets. For that purpose, platelets were incubated with SN from various fungal species; platelet activation and GAG deposition on the surface of platelets were detected by flow cytometry and electron and confocal microscopy, Culture supernatants of Aspergillus fumigatus and flavus isolates were potent platelet stimulators in a dose- and time-dependent manner, while SN of other Aspergillus species and all tested mucormycete species did not significantly induce platelet activation. The capacity of culture SN to activate platelets was dependent on fungal production of GAG and deposition of secreted GAG on the platelet surface; supernatants from mucormycetes or mutants of A. fumigatus lacking GAG secretion did not affect platelet activity. These results suggest that invading fungi can stimulate platelets not only locally through direct interactions with fungal hyphae, but can also act over a certain distance through secreted GAG. |
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| Keywords: | Galactosaminogalactan Platelets Mucormycosis Innate immunity Secreted fungal metabolites |
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