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

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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Référence

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 : 05 October 2023 | Publication date : 25 May 2023 | Redactor : Edition P. Huan