Aspergillus fumigatus conidia upregulates NOD2 protein expression both in vitro and in vivo

Aim: To determine if NOD2 is involved in host recognition of Aspergillus fumigatus (Af) conidia. Methods: An Af conidia pulmonary infection murine model was established by intranasal inoculation of Af onidia suspensions. Protein levels of NOD2 in lung tissue were determined by immunohistochemistry. A549 and phorbol-12-myristate 13-acetate (PMA)-activated THP-1 cell lines were treated with heat-killed Af conidia, then the presence of NOD2 protein in these cell lines was detected by Western blotting. The ability of muramyl dipeptide (MDP) to induce the secretion of TNF-alpha after incubation with heat-killed Af conidia was measured by enzyme-linked immunosorbent assay. Results: The expression of NOD2 protein in lung tissue increased after Af conidia infection. Heat-killed Af conidia significantly upregulated NOD2 protein expression in A549 cells and PMA-activated THP-1 cells. Additionally, Af conidia in conjuction with MDP, significantly increased the secretion of TNF-alpha in A549 cells and PMA-activated THP-1 cells. Conclusion: Af conidia upregulates NOD2 protein expression in vitro and in vivo. These findings indicate that NOD2 protein may respond to Af conidia.