Characterization And Expression Analysis Of Grouper’s(Epinephelus Coioides) APC-related Genes Post Cryptocaryon Irritans Infection

An antigen-presenting cell(APC) is a cell that displays antigen complexed with major histocompatibility complexes(MHCs)on their surfaces. T cells may recognize these complexes using their T cell receptors(TCRs). These cells process antigens and present them to T-cells. Professional APCs including dendritic cells, macrophages, and B cells,specialize in presenting foreign antigen-MHC II complex to T helper cells and elicit the adaptive immune response. Cryptocaryon irritans is an obligate ectoparasitic ciliate parasite, which is causing destructive economic losses in tropical and subtropical marine aquaculture. C. irritans has been demonstrated that can elicit a strong adaptive immune response post infection. To reveal the potential function of APC during the infection of C.irritans, we search the transcriptome data of C. irritans infective grouper, and 7APC-related genes(Ec IL-34, Ec MCSF2, Ec MCSFR2, Ec CCR6 A, Ec CCR6 B, Ec CD83,Ec CD208) were obtained and cloned. The ORF of Ec IL-34, Ec MCSF2 and Ec MCSFR2 was 657 bp, 804 bp and 3141 bp which encoding 218, 267 and 1046 deduced amino acids sequence with a theoretical molecular mass of 25.50 k Da, 31.02 k Da and 117.72 k Da,respectively. The ORF of Ec CCR6 A, Ec CCR6 B, Ec CD83 and Ec CD208 was 1134 bp,1089 bp, 1113 bp, 675 bp and 771 bp which encoding 377, 362, 224 and 256 deduced amino acids sequence with a theoretical molecular mass of 43.03 k Da, 40.81 k Da, 24.78 k Da and28.12 k Da, respectively. Together with the structural, homologous and phylogeny analysis of each sequence, respectively, it confirmed that all 7 genes were identified to other animals.Tissue distributions analysis showed that the expression pattern of each gene is various, but mainly express in immune tissues. Ec IL-34 was highest expressed in the brain, followed bygill, spleen, skin and muscle, low expressions of Ec IL-34 were found in the liver and thymus; Ec MCSF2, was high expressed in trunk kidney and head kidney, followed by brain,skin, heart, muscle, and low expressed in liver, gill, and thymus; Ec MCSFR2 was high expressed in head kidney and followed by spleen, gill, low expressed in muscle, thymus and heart; Both Ec CCR6 s were high expressed in gill, but not detected in liver, muscle and heart, Ec CCR6 B seems to dominate in head kidney and trunk kidney while Ec CCR6 A pronouncedly dominates in brain; Ec CD83 was high expressed in thymus and low expressed in non- lymphoid tissues; Ec CD208 was high expressed in head kidney, followed by gill, skin, brain and heart, low expressions in the rest tissues. Genes expression pattern post C. irritans infection shown that all 6 surface molecules(Ec MCSFR1, Ec MCSFR2,Ec CCR6 A, Ec CCR6 B, Ec CD83 and Ec CD208) were significantly up-regulated in infective skin. The significant up-regulation of those genes in C. irritans infection sites indicates the higher density of these molecules on single cell or the higher numbers of positive cells accumulated in these sites. The expression pattern in other tested tissues is various, but mainly up-regulated in gill and head kidney, and down-regulated in spleen. It suggests that positive cells may proliferate or differentiate in this primary hemopoietic organ, and migrate to C. irritans infected sites.