The Anti‐Infective Immune Mechanism of the CCL2 and CCL3 Chemokines in the Large Yellow Croaker (Larimichthys Crocea)

Chemokines are low‐molecular‐weight proteins that play an important role in the inflammatory response. During the development of aquaculture for the large yellow croaker (Larimichthys crocea, L. crocea), infectious diseases caused by viruses, bacteria, and parasites have become increasingly frequent and severe. In particular, bacterial infections caused by Vibrio anguillarum result in significant economic losses. The widespread usage of antibiotics as a traditional treatment has led to an imbalance in microenvironmental conditions, which causes environmental pollution and has an ultimately negative effect on human health. In this research, we studied the gene expression of the C‐C motif chemokine ligand 2 (CCL2) and C‐C motif chemokine ligand 3 (CCL3) chemokines in different organs of L. crocea after infection with V. anguillarum. The novel nucleotide sequences encoding L. crocea CCL2 and CCL3 were determined as a result of the performed analysis. We identified the transcriptional levels of these chemokine genes (CCL2 and CCL3) in the organs of L. crocea individuals infected with V. anguillarum and studied the effective domain of the response mechanism of CCL2 and CCL3. Real‐time PCR results showed a quantitative increase in the expression of the two types of genes in certain organs. These results could be useful for the study of the mechanisms of innate immune activation in fish species and the role of chemokines in enhancing the immune response. This information could help in developing methods of disease resistance in the aquaculture industry and, thus, decrease the amounts of antibiotic and chemical drugs used to treat fish.