TLR4 recognizes Pseudallescheria boydii conidia and purified rhamnomannans.
Pseudallescheria boydii (Scedosporium apiospermum) is a saprophytic fungus widespread in the environment, and has recently emerged as an agent of localized as well as disseminated infections, particularly mycetoma, in immunocompromised and immunocompetent hosts. We have previously shown that highly purified α-glucan from P. boydii activates macrophages through Toll-like receptor TLR2, however, the mechanism of P. boydii recognition by macrophage is largely unknown. In this work, we investigated the role of innate immune receptors in the recognition of P. boydii. Macrophages responded to P. boydii conidia and hyphae with secretion of proinflammatory cytokines. The activation of macrophages by P. boydii conidia required functional MyD88, TLR4, and CD14, whereas stimulation by hyphae was independent of TLR4 and TLR2 signaling. Removal of peptidorhamnomannans from P. boydii conidia abolished induction of cytokines by macrophages. A fraction highly enriched in rhamnomannans was obtained and characterized by NMR, high performance TLC, and GC-MS. Preparation of rhamnomannans derived from P. boydii triggered cytokine release by macrophages, as well as MAPKs phosphorylation and IκBα degradation. Cytokine release induced by P. boydii-derived rhamnomannans was dependent on TLR4 recognition and required the presence of non-reducing end units of rhamnose of the rhamnomannan, but not O-linked oligosaccharides from the peptidorhamnomannan. These results imply that TLR4 recognizes P. boydii conidia and this recognition is at least in part due to rhamnomannans expressed on the surface of P. boydii.
Departamento de Imunologia, Laboratório de Inflamação e Imunidade, Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 941-902 Brazil.
Rodrigo T
RT
Figueiredo
Patrícia L
PL
Fernandez
Fabianno F
FF
Dutra
Yissett
Y
González
Lívia Cristina
LC
Lopes
Vera Carolina B
VC
Bittencourt
Guilherme L
GL
Sassaki
Eliana
E
Barreto-Bergter
Marcelo T
MT
Bozza
D000818:Animals; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D025301:Hyphae / Q000276:immunology / Q000378:metabolism; D007113:Immunity, Innate / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000276:immunology / Q000378:metabolism; D008262:Macrophage Activation / Q000276:immunology*; D017737:Macrophages, Peritoneal / Q000276:immunology* / Q000378:metabolism; D008351:Mannans / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020929:Mitogen-Activated Protein Kinase Kinases / Q000276:immunology / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology / Q000378:metabolism; D011541:Pseudallescheria / Q000276:immunology* / Q000378:metabolism; D013172:Spores, Fungal / Q000276:immunology* / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000276:immunology* / Q000378:metabolism
D016207:Cytokines; D018950:Lipopolysaccharide Receptors; D008351:Mannans; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D020929:Mitogen-Activated Protein Kinase Kinases