Ligand recognition by the toll‐like receptor family

Molecular characterization and gene expression of pattern recognition receptors in brown-marbled grouper (Epinephelus fuscoguttatus) fingerlings responding to vibriosis infection

The pathogen recognition system involves receptors and genes that play a crucial role in activating innate immune response in brown-marbled grouper (Epinephelus fuscoguttatus) as a control agent against various infections including vibriosis. Here, we report the molecular cloning of partial open reading frames, sequences characterization, and expression profiles of Pattern Recognition Receptors (PRRs) in brown-marbled grouper. The PRRs, namely pglyrp5, tlr5, ctlD, and ctlE in brown-marbled grouper, possess conserved domains and showed shared evolutionary relationships with other fishes, humans, mammals, birds, reptilians, amphibians, and insects. In infection experiments, up to 50% mortality was found in brown-marbled grouper fingerlings infected with Vibrio alginolyticus compared to 27% mortality infected Vibrio parahaemolyticus and 100% survival of control groups. It is also demonstrated that all four PRRs had higher expression in samples infected with V. alginolyticus compared to V. parahaemolyticus. This PRRs gene expression analysis revealed that all four PRRs expressed rapidly at 4-h post-inoculation even though the Vibrio count was only detected earliest at 12-h post-inoculation in samples. The highest expression recorded was from V. alginolyticus inoculated fish spleen with up to 73-fold change for pglyrp5 gene, followed by 14 to 38-fold expression for the same treatment in spleen, head kidney, and blood samples for other PRRs, namely tlr5, ctlD, and ctlE genes. Meanwhile less than a 10% increase in expression of all four genes was detected in spleen, head kidney, and blood samples inoculated with V. parahaemolyticus. These findings indicated that pglyrp5, tlr5, ctlD, and ctlE play important roles in the early immune response to vibriosis infected, brown-marbled grouper fingerlings.

Molecular cloning and functional studies on magang goose toll-like receptor 5

Disease outbreaks heavily impact the economic viability of animal industries. Little is known about the mechanisms of immune system-related diseases in geese. Toll-like receptors (TLRs) play a major role in the anti-inflammatory immunity process in most animal species, but they have not been studied in the Magang goose. To elucidate the role of TLRs, reverse transcription polymerase chain reaction (RT-PCR) and PCR amplification of cDNA ends (Smart RACE) were used to clone the Magang goose TLR5 gene (mgTLR5). The full-length cDNA of mgTLR5 was 2967 bp in length, including a 5'-terminal untranslated region (UTR) of 215 bp, a 3'-terminal UTR of 384 bp, and an open reading frame of 2583 bp that encodes a protein of 860 amino acids. Structurally, mgTLR5 has a toll/interleukin-receptor (TIR) domain, a transmembrane domain, and seven leucine-rich repeats (LRRs) domains. Homology alignment of TLR5 and its TIR domains with other species revealed that mgTLR5 shared 98 % and 81.3 % of sequence similarity with white goose TLR5 and chicken TLR5, respectively. Quantitative RT-PCR showed that the mgTLR5 gene of the goose is widely expressed in all tested tissues, with the highest expression in the kidney and spleen. The increase in NF-κB promoter activity stimulated by flagellin was dependent on mgTLR5 expression in 293 T cells. Salmonella pullorum and flagellin significantly upregulated the expression of TLR5, IL-8, and IL-1 mRNA in peripheral blood mononucleotide cells of Magang goose cultured in vitro. Stimulation by S. pullorum for 24 h upregulated mgTLR5 expression in the cecum and kidney. We conclude that Magang goose TLR5 is a functional TLR5 homologue of the protein in other species and plays an important role in bacterial recognition.