Toll-like receptor (TLR)-based signaling pathways in the host may be modulated by pathogens during the course of infection. We describe a novel immunomodulatory mechanism in which Aspergillus fumigatus conidia induce attenuation of TLR2- and TLR4-mediated interleukin (IL)-6 and IL-1β proinflammatory responses in human mononuclear cells with suppression of IL-1β mRNA transcription. Background TLR2 and TLR4 mRNA transcription was not influenced. A. fumigatus conidia induced TLR2 internalization and uptake into the phagosome with a resultant decrease in surface receptor expression. A. fumigatus hyphae, on the other hand, selectively downregulated the TLR4-mediated response. These novel immunosuppressive effects may facilitate the invasiveness of A. fumigatus.

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Infection and Immunity
Erasmus MC: University Medical Center Rotterdam

Chai, L., Kullberg, B. J., Vonk, A., Warris, A., Cambi, A., Latgé, J. P., … Netea, M. (2009). Modulation of toll-like receptor 2 (TLR2) and TLR4 responses by Aspergillus fumigatus. Infection and Immunity, 77(5), 2184–2192. doi:10.1128/IAI.01455-08