Molecular Cloning of Toll-like Receptor 2 and 4 (, ) and Expression of TLR-Related Genes from after Poly (I:C) Stimulation.

Toll-like receptor (TLR) signaling is conserved between fish and mammals, except for TLR4, which is absent in most fish. In the present study, we aimed to evaluate whether TLR4 is expressed in (). The and were cloned and identified, and their tissue distribution was examined. The cDNA encoding and complete coding sequences (CDS) were identified and cloned. Additionally, we examined the expression levels of seven (, , , , , , and ), as well as and in the liver, head kidney, hindgut, and spleen of , after intraperitoneal injection of polyinosinic-polycytidylic acid (poly (I:C)). The TLR2 and TLR4 shared amino acid sequence identity of 42.15-96.21% and 36.21-93.58%, respectively, with sequences from other vertebrates. and were expressed in all tissues examined, particularly in immune-related tissues. Poly (I:C) significantly upregulated most of the genes evaluated in the four immune organs compared with the PBS-control ( < 0.05); expression of these different genes was tissue-specific. Our findings demonstrate that TLR2 and TLR4 are expressed in and that poly (I:C) affects the expression of nine TLR-related genes, which are potentially involved in antiviral immunity or mediating pathological processes with differential kinetics. This will contribute to a better understanding of the roles of these TLR-related genes in antiviral immunity.