Innate immune gene expression in individual zebrafish after Listonella anguillarum inoculation

Zebrafish were intraperitoneally injected with 106 CFU (LD50) Listonella anguillarum. Three inoculated and control fish were collected at 1, 2, 4, 6 and 22 h post infection (hpi) and the expression of genes related to the immune response (il1b, cebpb, tfa, mpx, tnfa, nitr9, tlr22, hsc70, cp, mrlp1, c3b and lyz) in each fish was monitored by means of real-time RT-PCR. A similar experiment was performed considering an intermediate time point at 15 hpi. Different relative levels of expression were found among genes. Also, wide interindividual variation in gene expression for most genes was detected among fish, inoculated or not.A steady increase of expression starting from the initial stages of the interaction was found for interleukin-1β. An initial increase in levels of gene expression was found for the genes coding for the CCAAT/Enhancer Binding Protein subunit β and the Novel Immune-Type Receptor 9, although their levels decreased later on and were indistinguishable from the controls at 22 hpi. Finally, some genes (Transferrin, Myeloid-specific Peroxidase and Tumour Necrosis Factor α) were upregulated at 22 hpi.Taken together, our results show an induction in gene expression of genes involved in the inflammatory and immune response upon L. anguillarum infection but also reveal the existence of a wide variation in the levels of expression of the studied genes in the zebrafish population.