Trans-Cinnamaldehyde Primes More Robust Channel Catfish Immune Responses to Edwardsiella ictaluri Infection

Abstract

Infection with Edwardsiella ictaluri, a causative agent of enteric septicemia of catfish, threatens profitable catfish production through inventory losses. We previously demonstrated that trans-cinnamaldehyde (TC) enhances the survival of catfish following E. ictaluri infection. The present study was conducted to investigate catfish immune responses to TC feeding and E. ictaluri infection. The expression of 13 proinflammatory, innate, and adaptive immune-related genes was evaluated over time in two sets of experiments using real-time polymerase chain reaction (PCR). In the first experiment, catfish were fed a basal diet with or without TC supplementation, while in the second they were fed a TC-supplemented or normal diet followed by infection with E. ictaluri. The catfish group infected with E. ictaluri and fed a TC-diet showed significant changes in the expression of innate and adaptive immune-related genes compared to control group. At 21 and 28 days post-infection, recovered fish showed significant increases in the expression of IgM in the anterior kidney and spleen. These results suggest that the supplemental dietary intake of TC can improve the immune status of catfish via engaging innate and adaptive immune responses and the production of memory cells in immunocompetent tissues. Together, this study provides an important foundation for the potential application of TC as an antimicrobial alternative in aquaculture.

Keywords: adaptive immunity; enteric septicemia of catfish; innate immunity; pro-inflammatory genes; real-time PCR.

Figure 1

Gene expression profiles in the liver, spleen, and anterior kidney (AK) of channel catfish fingerlings that received a TC-supplemented diet as compared to those in catfish fed a normal diet on days 1 (red), 7 (orange), 14 (green), and 21 (blue). Each subfigure (A–M) represents the expression level of one gene. Data are represented as fold change in gene expression over the control group ± standard error. Four technical replicates were analyzed from a pool of ten catfish per time point. * p < 0.05, two-tailed Student’s t-test.

Figure 2

Gene expression profiles in the liver, spleen, and AK of channel catfish injected with E. ictaluri and fed a TC-supplemented diet as compared to catfish fed a regular diet on day 1 (red), 7 (orange), 14 (green), 21 (blue), and 28 (dark blue). Each subfigure (A–M) represents the expression level of one gene. Data are represented as fold change over the control group (received normal diet) following E. ictaluri challenge ± standard error. Four technical replicates were analyzed from a pool of ten tissue samples per time point. * p < 0.05, two-tailed Student’s t-test.