Abstract: CD80 is a member of immunoglobulin superfamily, which is an important costimulatory signal necessary for T cell proliferation and activation. In this study, CD80 gene sequence of Cynoglossus semilaevis(CsCD80)(GenBank accession number: XR_521517.2) was obtained from its whole genome sequence. The open reading frame contains 882 bp encoding 293 amino acids with an estimated molecular weight of 32.45 ku and a theoretical pI of 7.97. Amino acid sequence alignment indicated that CsCD80 contained a predicted signal peptide, an immunoglobulin(Ig) domain and a transmembrane(TM) domain. Multiple sequence alignment showed that CsCD80 shared the highest amino acid sequence identity(41.37%) with Japanese flounder CD80 . Quantitative real-time PCR analysis showed that CsCD80 had the highest expression level in liver and spleen. When infected with V. harveyi and megalocytivirus, the expression level of CsCD80 significantly incresed in liver, spleen and kidney. Immunofluorescence test was used for the determination of the recombinant CsCD80 protein(rCsCD80) binding to the surface of peripheral blood lymphocytes(PBLs) when incubated with recombinant CsCD80 protein(rCsCD80) expressed by prokaryotic expression system. These results indicated that CsCD80 might play an important role in the immune response against bacteria and virus in C. semilaevis.

Key words: C. semilaevis, CD80, expression analysis, peripheral blood lymphocytes