INRAE, Auteur Nicolas Bertrand (bassin de truites en pisciculture)

Publication Microbes and Infection, VIM, GABI, IERP

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Publication Microbes and Infection, VIM, GABI, IERP

Phenotyping isogenic trout lines to elucidate mechanisms of resistance to bacterial infection

In a study published in Microbes & Infection, researchers from the Infection et Immunité des Poissons team (Virologie et Immunologie Moléculaires - VIM unit, INRAE/UVSQ/UPSaclay, Jouy-en-Josas), in collaboration with INRAE's GABI and IERP units, have established a set of phenotypes linked to pathogenesis through the characterization of a collection of isogenic trout lines with contrasting resistance. Guided by the 3Rs principle, individual monitoring by non-lethal blood sampling has been applied for the first time in trout to monitor bacterial infection and host response; this approach makes it possible both to reduce the number of fish used and to increase the power of the experimental set-up.

Infectious diseases are an obstacle to the rational development of "sustainable" aquaculture. Flavobacterium psychrophilum is responsible for flavobacteriosis, a disease whose recurrent infectious episodes are associated with high mortalities and the use of antibiotics, with a major economic and ecological impact on salmonid fish farms worldwide. In the absence of effective vaccines, understanding the infectious process and the molecular basis of disease resistance is a key step towards developing effective preventive strategies.

The study showed that resistance is associated with better control of bacterial growth by fish; in the blood of resistant animals, certain immune genes involved in arginine metabolism and in the detection and destruction of pathogenic bacteria are over-expressed.

This study was made possible by funding from the French National Research Agency (ANR-17-CE20-0020-0) and the European Union (Horizon 2020 # 817923, AQUAFAANG).

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Bo-Hyung Lee, Edwige Quillet, Dimitri Rigaudeau, Nicolas Dechamp, Eric Duchaud, Jean-François Bernardet, Pierre Boudinot, Tatiana Rochat. 2023. Interplay between a bacterial pathogen and its host in rainbow trout isogenic lines with contrasted susceptibility to Cold Water Disease. Microbes and Infection, 105140.
ISSN 1286-4579,
https://doi.org/10.1016/j.micinf.2023.105140.
(https://www.sciencedirect.com/science/article/pii/S1286457923000436)
Abstract: Infectious diseases are a major constraint on aquaculture. Genetic lines with different susceptibilities to diseases are useful models to identify resistance mechanisms to pathogens and to improve prophylaxis. Bacterial cold-water disease (BCWD) caused by Flavobacterium psychrophilum represents a major threat for freshwater salmonid farming worldwide. A collection of rainbow trout (Oncorhynchus mykiss) isogenic lines was previously produced from a French domestic population. Here, we compared BCWD resistance phenotypes using a subset of isogenic lines chosen for their contrasted susceptibilities to F. psychrophilum. We applied individual monitoring to document the infection process, including time-course quantification of bacteremia and innate immune response. Strikingly, BCWD resistance was correlated with a lower bacterial growth rate in blood. Several immune genes were expressed at higher levels in resistant fish regardless of infection: the Type II arginase (arg2), a marker for M2 macrophages involved in anti-inflammatory responses and tissue repair, and two Toll-like receptors (tlr2/tlr7), responsible for pathogen detection and inflammatory responses. This study highlights the importance of innate and intrinsic defense mechanisms in determining the outcome of F. psychrophilum infections, and illustrates that non-lethal time-course blood sampling for individual monitoring of bacteremia is a powerful tool to resolve within-host pathogen behavior in bacterial fish diseases.
Keywords: bacteremia; physiologic monitoring; genetic fitness; disease resistance; innate immunity; aquaculture

Modification date : 02 November 2023 | Publication date : 23 May 2023 | Redactor : Edition P. Huan