Abstract:Expression of channel catfish TLR5 and TLR5S genes in the head kidney, intestine, liver and spleen were analyzed by quantitative real time PCR method at 0 h, 12 h, 24 h, 48 h, 72 h and 7 d after infection with Edwardsiella tarda, Aeromonas hydrophila, Streptococcus iniae and channel catfish hemorrhage reovirus (CCRV), respectively. The results showed that TLR5 and TLR5S mRNAs were largely up-regulated by E. tarda and S. iniae and the most significant increase of TLR5S gene expression occurred in head kidney 12h after being challenged with S. iniae, which was 132-fold higher than the PBS control. After infection with A. hydrophila, TLR5 and TLR5S showed up regulation at 12h and 24h and obvious down-regulation at 48h to 7d post-infection. TLR5 and TLR5S genes expression were suppressed by infection with CCRV in most tissues. In spleen, the expression of TLR5 was 0.017-fold while TLR5S was only 0.01-fold compared with PBS control. Among the four immune-related different tissues, the expression of TLR5 and TLR5S showed significant up-regulation in intestine and head kidney. For example, after being challenged with E. tarda and S. iniae, at time point of 12h, the expression of TLR5 increased 50.4-fold and 14.8-fold respectively in intestine, and the expression of TLR5S increased 52.8-fold and 132-fold respectively in head kidney. All data suggested that TLR5 and TLR5S were involved in the immune response of channel catfish against the intracellular bacterial and virus pathogen in a tissue-specific and pathogen-specific manner, and further confirmed that both of them played significant roles in the channel catfish innate immunity.
