Molecular cloning of Peking duck Toll-like receptor 3 (duTLR3) gene and its responses to reovirus infection.

BACKGROUND: Toll-like receptors (TLRs) play an important role in detecting pathogen-associated molecular patterns (PAMPs). Among the TLRs, TLR3 is involved in the recognition of double-stranded RNA. This study was designed to explore the relationship between duTLR3 and duck reovirus (DRV) infection. METHODS: In this study, we cloned and performed a molecular characterization of the complete sequence of Peking duck TLR3 (duTLR3). The expression level of duTLR3 was also determined, along with the relative levels of Mx and IFN-α mRNA after DRV infection. RESULTS: The duTLR3 gene is 2776-bp long and encodes an 895-amino-acid-long protein. Sequence analysis of the product revealed the complete transcript of Peking duck TLR3, including the 88-bp 5'UTR, the 2688-bp coding sequence (ORF), and the 76-bp 3'UTR and poly(A) tail. DuTLR3 was found to share a high amino acid sequence similarity with TLR3 from Jing ding duck (99.6 %), Muscovy duck (97.1 %) and chicken (86.3 %). Additionally, the tissue distribution of duTLR3 suggested that it was abundantly expressed in various tissues, especially in the trachea, esophagus and pancreatic gland. Duck reovirus (DRV) infection resulted in high mRNA expression levels of duTLR3 in the spleen, liver, lung and brain. CONCLUSION: These results suggest that duTLR3 may play an important role in anti-viral defense mechanisms.