Goose toll-like receptor 3 (TLR3) mediated IFN-γ and IL-6 in anti-H5N1 avian influenza virus response

Induction of the innate immune pathways is critical for early anti-viral defense. How geese recognize viral molecules and activate these pathways is not well understood. In mammals, Toll-like receptor 3 (TLR3) recognizes double-stranded RNA. Activation of TLR3 induces the activation of NF-кB and the production of type-I interferon. In this study, the goose TLR3 gene was cloned using rapid amplification of cDNA ends. Goose TLR3 encoded an 896-amino-acid protein, containing a signal secretion peptide, 14 extracellular leucine-rich repeat domains, a transmembrane domain, a Toll/interleukin-1 receptor signaling domain, and shared 46.7-84.4% homology with other species. Tissue expression of goose TLR3 varied markedly and was highest in the pancreas and lowest in the skin. Human embryonic kidney 293 cells transfected with goose TLR3 and NF-κB-luciferase-containing plasmids responded significantly to poly i:c. The expression of TLR3, IL-6 and IFN-γ mRNA, but not IL-1 mRNA, was significantly upregulated after poly i:c or high pathogenic avian influenza virus (H5N1) stimulation in goose peripheral blood mononuclear cells cultured in vitro. Furthermore, geese infected with H5N1 showed significant upregulation of TLR3, especially in the lung and brain. We conclude that goose TLR3 is a functional TLR3 homologue of the protein in other species and plays an important role in virus recognition.