Class II, major histocompatibility complex, transactivator (CIITA) in channel catfish: identification and expression patterns responding to different pathogens.

NLRs are a large family belonging to pattern recognition receptors which could recognize pathogen associated molecular patterns. Class II, major histocompatibility complex, transactivator (CIITA) is a member of NLR family. It is a critical transcription factor which could regulate the expression of MHC class II. In this study, a full-length cDNA of CIITA was cloned from channel catfish according to ten sequenced ESTs. This cDNA contains a 5'-UTR of 71 bp, a 3'-UTR of 238 bp and an ORF of 3,210 bp encoding 1,069 amino acids. Phylogenetic analysis showed that catfish CIITA was conserved with other CIITAs. Quantitative real-time PCR was conducted to detect the expression profiles of CIITA in normal tissues and responding to different pathogens (Edwardsiella tarda, Streptococcus iniae and channel catfish Hemorrhage Reovirus (CCRV)). The expression profile in blood was the highest (53.879-fold) in normal tissues. E. tarda and S. iniae could induce catfish CIITA in head kidney, liver and spleen. CCRV virus could also induce CIITA in head kidney and liver but reduce it in spleen. And S. iniae could induce the expression of CIITA to the highest extent and contrarily CCRV virus to the lowest extent. The expression data showed the tissue-specific and pathogen-specific expression patterns of CIITA responding to different pathogens. These expression data indicated the immune-related functions of CIITA. The data obtained in this study provide a basis for further research aimed at explore the precise immune-related molecular mechanism of CIITA in catfish.