Trained Immunity Provides Long-Term Protection against Bacterial Infections in Channel Catfish.

Area of Science:

• Immunology
• Fish Health
• Molecular Biology

Background:

• Bacterial diseases like Edwardsiella ictaluri and Edwardsiella piscicida cause significant losses in channel catfish aquaculture.
• Trained immunity, a form of innate immune memory, has been observed in mammals but its mechanisms in fish are less understood.

Purpose of the Study:

• To investigate the effects of beta glucan on trained immunity in channel catfish.
• To elucidate the molecular mechanisms underlying beta glucan-induced trained immunity and protection against Edwardsiella infections.

Main Methods:

• Channel catfish were exposed to beta glucan, followed by challenge with Edwardsiella ictaluri and Edwardsiella piscicida.
• Flow cytometry was used to analyze immune cell phagocytosis.
• Histone modification analysis (H3K4 monomethylation/trimethylation, H3K27 acetylation/trimethylation) and KEGG pathway analysis were performed.

Main Results:

• Beta glucan exposure conferred long-term protection against Edwardsiella infections one month post-exposure.
• Macrophages and neutrophils showed enhanced phagocytosis of E. ictaluri and E. piscicida.
• Beta glucan induced specific changes in histone modifications, affecting genes involved in phagocytosis, phagosome function, and immune signaling.

Conclusions:

• Beta glucan induces trained immunity in channel catfish, enhancing innate immune responses and conferring protection against bacterial pathogens.
• The study demonstrates conserved mechanisms of trained immunity, including chromatin reconfiguration, in fish similar to mammals.
• Findings support the development of non-antibiotic therapies and vaccines for bacterial disease prevention in aquaculture.