Cloning, expression and functional analysis of the duck Toll-like receptor 5 (TLR5) gene

Abstract

Toll-like receptor 5 (TLR5) is responsible for the recognition of bacterial flagellin in vertebrates. In the present study, the first TLR5 gene in duck was cloned. The open reading frame (ORF) of duck TLR5 (dTLR5) cDNA is 2580 bp and encodes a polypeptide of 859 amino acids. We also cloned partial sequences of myeloid differentiation factor 88, 2'-5'-oligoadenylate synthetase (OAS), and myxovirus resistance (Mx) genes from duck. dTLR5 mRNA was highly expressed in the bursa of Fabricius, spleen, trachea, lung, jejunum, rectum, and skin; moderately expressed in the muscular and glandular tissues, duodenum, ileum, caecum, and pancreas; and minimally expressed in the heart, liver, kidney, and muscle. DF-1 or HeLa cells transfected with DNA constructs encoding dTLR5 can activate NF-κB leading to the activation of interleukin-6 (IL-6) promoter. When we challenged ducks with a Herts33 Newcastle disease virus (NDV), mRNA transcription of the antiviral molecules Mx, Double stranded RNA activated protein kinase (PKR), and OAS was up-regulated in the liver, lung, and spleen 1 and 2 days post-inoculation.

Pathologic Mechanisms of the Newcastle Disease Virus

“…It was further detected that NDV-derived dsRNA colocalizes with TLR3 in subcellular structures, and the activation of TLR3 and TLR7 is associated with the NF-κB pathway of innate immune responses, proving the monitoring role of the TLRs against NDV infection [54]. Apart from TLR3 and TLR7, the overexpression of duck TLR5 in DF-1 and HeLa cells also initiated the NF-κB pathway and upregulated IL-6 promoter activities [57]. In geese, TLR1, TLR3, TLR5, TLR7, and TLR15 expressions were all upregulated after NDV genotype VIId strain infection, suggesting that these TLRs may also participate in anti-NDV responses, which needs further exploration [45].…”

Innate immune responses to duck Tembusu virus infection

“…TLR, a group of conserved type I transmembrane proteins, is one of the most critical PRRs which can sense the different invading pathogens outside the cell membrane and internally in endosomes and lysosomes. Currently, 10 TLR have been reported in human, and 10 TLR in chicken, while only 5 TLR (TLR 2 [ 62 ], TLR3 [ 63 ], TLR4 [ 64 ], TLR5 [ 65 ], and TLR7 [ 66 ]) in duck. Furthermore, there are some differences between avian and mammal TLR, including the absence of TLR8 and TLR9 and the presence of TLR1La, TLR1Lb, TLR15, and TLR21 in chickens [ 67 , 68 ].…”

Two myeloid differentiation factor 88 (MyD88) isoforms identified in ducks

“…To date, 6 duck (Anas platyrhynchos) TLRs (duTLRs), duTLR1 (Huang et al, 2011), duTLR2 (Huang et al, 2011), duTLR3 (Jiao et al, 2012), duTLR 4 (Jia et al, 2012), duTLR5 (Cheng et al, 2015), and duTLR7 (MacDonald et al, 2008) have been identified. However, most components of the TLR pathway of duck remain elusive, including the MyD88 key adaptor protein coordinating the Toll pathway.…”