Transcriptional Responses of Resistant and Susceptible Fish Clones to the Bacterial Pathogen Flavobacterium psychrophilum

Abstract

Flavobacterium psychrophilum is a bacterial species that represents one of the most important pathogens for aquaculture worldwide, especially for salmonids. To gain insights into the genetic basis of the natural resistance to F. psychrophilum, we selected homozygous clones of rainbow trout with contrasted susceptibility to the infection. We compared the transcriptional response to the bacteria in the pronephros of a susceptible and a resistant line by micro-array analysis five days after infection. While the basal transcriptome of healthy fish was significantly different in the resistant and susceptible lines, the transcriptome modifications induced by the bacteria involved essentially the same genes and pathways. The response to F. psychrophilum involved antimicrobial peptides, complement, and a number of enzymes and chemokines. The matrix metalloproteases mmp9 and mmp13 were among the most highly induced genes in both genetic backgrounds. Key genes of both pro- and anti-inflammatory response such as IL1 and IL10, were up-regulated with a greater magnitude in susceptible animals where the bacterial load was also much higher. While higher resistance to F. psychrophilum does not seem to be based on extensive differences in the orientation of the immune response, several genes including complement C3 showed stronger induction in the resistant fish. They may be important for the variation of susceptibility to the infection.

Assessment of Genetic Correlation between Bacterial Cold Water Disease Resistance and Spleen Index in a Domesticated Population of Rainbow Trout: Identification of QTL on Chromosome Omy19

“…At present, we have not identified a mechanistic connection between spleen size and BCWD resistance. The transcriptional response of BCWD resistant and susceptible rainbow trout homozygous clones have identified differential up-regulation of IL1 and IL10 gene transcript in susceptible clonal line B57 while complement factor C3 gene transcript showed stronger up-regulation in resistant clonal line A3 at day 5 post-challenge [54]. It will be of interest to determine whether these gene candidates are differentially expressed in our QTL population and whether they map to genomic regions with QTL detected in this study.…”

Infectious disease, shifting climates, and opportunistic predators: cumulative factors potentially impacting wild salmon declines

“…) and Flavobacterium psychrophilum (Langevin et al. ). A single study on ISAV contradicted the pattern of enhanced response with higher microbe loads and more susceptible hosts; Workenhe et al.…”

“…For IPNV, survivors generally elicited a stronger innate immune responses (Marjara et al 2011), whereas for IHNV, the efficiency of viral entry and strength of host down-regulation of cell transcription and translation appeared to be more important determinates of susceptibility (Miller et al 2007 and K. M. Miller, unpublished data;Purcell et al 2011). Alternately, the strength of complement activation appeared to be more predictive of resistance to bacteria A. salmonicida ( Skugor et al 2009) and Flavobacterium psychrophilum (Langevin et al 2012). A single study on ISAV contradicted the pattern of enhanced response with higher microbe loads and more susceptible hosts; Workenhe et al (2009) found that a low virulent strain of ISAV elicited a stronger host response than highly virulent strains.…”

In vivo adherence of Flavobacterium psychrophilum to mucosal external surfaces of rainbow trout (Oncorhynchus mykiss) fry

“…; Langevin et al . ). Rainbow trout skin surface constitutes a large area for possible adhesion of bacterial pathogens such as Yersinia ruckeri (Tobback et al .…”