Gene expression and in silico analysis of snakehead murrel interleukin 8 and antimicrobial activity of C-terminal derived peptide WS12.

Chemokines have been known for their wide range of functions including chemoattractant property in humans and other vertebrate organisms. They act as a bridge between innate and adaptive immune system. In the present study, we have identified a CXC chemokine from the cDNA library of C. striatus; on the basis of orthology study, it was found highly identical to interleukin 8 (IL8). The bioinformatics analysis of the chemokine revealed the presence of a typical γ-core domain and a CXC motif at the N-terminal region of the molecule. Based on the amphipathic nature at the C terminal helical region of CstIL8 and their antimicrobial propensity observed during bioinformatics analysis, a short peptide namely WS12 comprising 12 amino acid residues was predicted and synthesized to determine its antimicrobial activity. The peptide WS12 was active against Bacillus cereus, a Gram positive bacterium. Scanning electron microscopy (SEM) results showed bleb-like formation on the surface of the bacteria after the treatment of WS12. Additionally, WS12 did not exhibit any cytotoxic activity against the fish leukocytes. Further, the gene expression studies also revealed that CstIL8 was expressed significantly in liver of Channa striatus (Cst) at basal level. The immune challenge studies with pathogens and immune-stimulants revealed an increase in the mRNA levels at different time points post-challenge. Hence, it is possible to conclude that WS12 was a potent antimicrobial agent and it was significantly expressed during the pathogen stress.