Effects of inactivated Streptococcus iniae, Edwardsiella tarda, and Poly I:C on mRNA Expression Levels of CXCL-10 and CXCL-9 Genes in Japanese Flounder

Abstract

The present study accomplished the successful cloning and sequencing of the JfCXCL9_L and JfCXCL10_L genes found in the spleen cDNA of the Japanese flounder (Paralichthys olivaceus). The tissue distribution of these two genes was determined before any stimuli administration at the zero-hour mark. The qRT-PCR analysis demonstrated that the expression of JfCXCL10_L closely mirrored that of IL1-β, displaying an upregulation following the application of Poly I:C (Viral mimic) and formalin-killed Edwardsiella tarda (Gram-Negative mimic), while showing a downregulation after the application of formalin-killed Streptococcus iniae (Gram-Positive mimic) treatment. These findings strongly suggest a role for JfCXCL10_L in the immune response to viral and gram-negative bacterial stimuli. Regarding JfCXCL9_L, mRNA levels were found to be significantly downregulated after FKCET and FKCSI treatments, though to varying extents. Interestingly, at specific time points, JfCXCL9_L levels were even lower compared to Poly I:C treatment. These intriguing findings shed valuable light on the roles of both JfCXCL9_L and JfCXCL10_L in potential functions of immune response mechanisms of the Japanese flounder'.