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Repression of the fliC gene as an immune evasion strategy in Yersinia ruckeri infection of rainbow trout (Oncorhynchus mykiss) Cover

Repression of the fliC gene as an immune evasion strategy in Yersinia ruckeri infection of rainbow trout (Oncorhynchus mykiss)

Open Access
|Oct 2025

Abstract

Introduction

The virulence of Yersinia ruckeri, the causative agent of enteric redmouth disease in salmonids, is influenced by multiple factors, including flagellar gene expression. This study investigates the role of fliC gene expression in the pathogenicity of Y. ruckeri and its impact on the immune response of infected rainbow trout (Oncorhynchus mykiss).

Material and Methods

Using two virulent strains differing in fliC expression, clinical symptoms, mortality rates and key immune parameters were evaluated. Ninety farmed rainbow trout with average body weight of 110.5 ± 24.1 g and average length of 20.7 ± 1.9 cm were used. Allocation was made of 10 fish each to a control group, a low-dose group challenged with one strain, a high-dose group challenged with that strain, and low- and high-dose groups challenged with the second strain, and each challenge group was duplicated.

Results

Fish infected with the fliC-repressed strain exhibited more severe symptoms, higher mortality rates and a weaker immune response regardless of infectious dose compared to those infected with the fliC-expressing strain. The lack of an active fliC gene was associated with a lower gammaglobulin level, decreased respiratory burst and suppressed T-cell proliferation. However, increased potential killing activity was noted for that strain.

Conclusion

These findings clearly demonstrate the dual role of the fliC gene in the pathogenicity of Y. ruckeri and host immune modulation in rainbow trout.

Language: English
Submitted on: Mar 5, 2025
Accepted on: Oct 16, 2025
Published on: Oct 22, 2025
Published by: National Veterinary Research Institute in Pulawy
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year

© 2025 Patrycja Schulz, Joanna Pajdak-Czaus, Karolina Pospiech, Elżbieta Fornal, Amanda Kobiera, Justyna Matczak, Paweł Foksiński, Andrzej Krzysztof Siwicki, published by National Veterinary Research Institute in Pulawy
This work is licensed under the Creative Commons Attribution 4.0 License.

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