ABSTRACTThe mechanisms that govern the initial interaction betweenParacoccidioides brasiliensis, a primary dimorphic fungal pathogen, and cells of the innate immunity need to be clarified. Our previous studies showed that Toll-like receptor 2 (TLR2) and TLR4 regulate the initial interaction of fungal cells with macrophages and the pattern of adaptive immunity that further develops. The aim of the present investigation was to assess the role of MyD88, an adaptor molecule used by TLRs to activate genes of the inflammatory response in pulmonary paracoccidioidomycosis. Studies were performed with normal and MyD88−/−C57BL/6 mice intratracheally infected withP. brasiliensisyeast cells. MyD88−/−macrophages displayed impaired interaction with fungal yeast cells and produced low levels of IL-12, MCP-1, and nitric oxide, thus allowing increased fungal growth. Compared with wild-type (WT) mice, MyD88−/−mice developed a more severe infection of the lungs and had marked dissemination of fungal cells to the liver and spleen. MyD88−/−mice presented low levels of Th1, Th2, and Th17 cytokines, suppressed lymphoproliferation, and impaired influx of inflammatory cells to the lungs, and this group of cells comprised lower numbers of neutrophils, activated macrophages, and T cells. Nonorganized, coalescent granulomas, which contained high numbers of fungal cells, characterized the severe lesions of MyD88−/−mice; the lesions replaced extensive areas of several organs. Therefore, MyD88−/−mice were unable to control fungal growth and showed a significantly decreased survival time. In conclusion, our findings demonstrate that MyD88 signaling is important in the activation of fungicidal mechanisms and the induction of protective innate and adaptive immune responses againstP. brasiliensis.
77. TLR and Myd88 Signaling Pathway Is Required for the Full Induction of Host Adaptive Immune Responses to Adenoviral Vectors and Transgenes
