Characterization and expression analysis of grouper (Epinephelus coioides) co-stimulatory molecules CD83 and CD80/86 post Cryptocaryon irritans infection

Co-stimulatory molecules (CD83, CD80 and CD86), belong to immunoglobulin superfamily, are type I membrane glycoprotein, which express on antigen presenting cells and provide the second signal for the activation of T lymphocytes. In the present study, we cloned the grouper's CD83 (675 bp) and CD80/86 (876 bp). Homology analysis showed that both EcCD83 and EcCD80/86 shares the highest amino acid similarity (51% and 47%) for the overall sequence with puffer fish (Takifugu rubripes). Some conserved features and important functional residues in mammalian CD83, CD80 and CD86 were also identified from these molecules of teleosts including grouper, suggesting the function of both molecules may be conserved among vertebrates. In transfected HEK293T cells, both molecules localized on the membrane surface. Tissue distribution analysis showed both EcCD83 and EcCD80/86 mRNAs were mainly expressed in immune organs, and EcCD80/86 was extremely higher expressed in mucosal immune tissues including skin and gill than systematic immune organs, which indicates these co-stimulatory molecules may prime T cell activation in local mucosal tissues. In Cryptocaryon irritans infected groupers, the expression level of EcCD83 and EcCD80/86 were both seen significant up-regulation in the skin at most tested time points.