The impact of outbreeding on the immune function and disease status of eight hybrid Chinook salmon crosses after Vibrio anguillarum challenge

Abstract

Aquaculture in North America is currently dominated by Atlantic salmon, but there has been an increasing interest in the production of species native to the Pacific coast.Chinook salmon is relatively new to production; therefore, the selection of appropriate stocks is critical. Often genes from wild populations are incorporated into farmed stocks to avoid performance decreases associated with inbreeding. The present study focuses on assessing the immunological performance of one inbred stock and seven outbred/hybrid crosses after challenge with the marine pathogen, Vibrio anguillarum.Throughout exposure challenge to both pathogen and sterile PBS, significant differences in mortality were observed between crosses. Fish were also assessed for major histocompatibility complex (MHC) class II β1 genotype, and although particular alleles did not confer resistance, crosses with better survival had more individuals presenting a heterozygous genotype. The stress induced during infection resulted in several individuals presenting signs of Bacterial Kidney Disease (Renibacterium salmoninarum) indicating that chronic co-infection may have contributed to susceptibility. When spleen samples from the highest and lowest performing hybrid crosses were assessed for cytokine and respiratory burst gene expression throughout bacterial challenge, high surviving crosses presented lower expression of inflammatory cytokine transcripts (IL-1β, IL-6 and TNFα) when compared to low performing crosses. Interestingly, microsatellite analysis revealed no significant differences in inbreeding coefficient or allelic richness between crosses despite observed variation in immune performance.Understanding the impact of outbreeding on the immune function of farmed, and often inbred, Chinook salmon could aid in future development of high-quality aquaculture stocks for this species.

The effects of Pediococcus acidilactici MA18/5M on growth performance, gut integrity, and immune response using in vitro and in vivo Pacific salmonid models

“…The fish pathogen, V. anguillarum , is well known for inducing immune transcripts of the inflammatory response when infecting salmonids ( 26 , 69 ). Therefore, it is not surprising to see an increase in the expression of il1b , il8 , and myd88 after inoculation with heat-killed V. anguillarum J382.…”

“…This strain has shown promising results promoting growth performance, modulation of both innate and adaptive immunity, improved survival rates, and resistance to infection ( 12 , 17 – 20 ). To date, available research has demonstrated that P. acidilactici increases growth, blood leucocyte levels, immunoglobulin (Ig) levels, serum lysozyme activity, and transcripts encoding il1b , il8 , il10 , and tnfa , among others, in salmonids species utilized in aquaculture such as rainbow trout ( Oncorhynchus mykiss ) ( 21 – 23 ) and Atlantic salmon ( Salmo salar ) ( 1 , 24 – 26 ).…”

“…In particular, Chinook salmon (Oncorhynchus tshawytscha) is the largest species of this family and presents potential economic and environmental advantages compared to farming of its Atlantic counterpart on the Pacific Northwest (28)(29)(30)(31). However, Chinook salmon farming is hampered by the risk of escapees diluting the genetic diversity of wild populations and their poor tolerance to commercial production conditions (25,26). Sterile triploid salmon effectively circumvents escapee issues, however these fish exhibit 10-30% higher mortality rate due to infectious disease compared to diploid fish (Data provided by Yellow Island Aquaculture Ltd.).…”

Comparative Genomic Analysis of Virulent Vibrio (Listonella) anguillarum Serotypes Revealed Genetic Diversity and Genomic Signatures in the O-Antigen Biosynthesis Gene Cluster

“…In 1999, a strain of V. anguillarum O1, designated here as J382, was isolated from a winter steelhead trout in the Little Campbell River, British Columbia, Canada [ 23 ] and used in the present study. This study, therefore, aimed to characterize this strain and describe the characteristics of the complete genome.…”

Physiological and Biochemical Characteristics of Rainbow Trout with Severe, Moderate and Asymptomatic Course of Vibrio anguillarum Infection

“…In this work, we aimed to characterize the clinical signs of infectious processes caused by V. anguillarum in cultured trout, including alterations in the composition of plasma proteins and populations of blood cells. At the molecular level, the pathogenesis of natural V. anguillarum infection has not previously been studied in the field, where the variation in bacterial loads gives particular individuals a chance to overcome the disease at the early stages, in contrast to experiments where an effective pathogen titer is deliberately used [ 4 , 12 , 13 ]. Therefore, the article discusses a possible relationship between the production of certain blood proteins in individual fish, their hematological profile, physiological state, and the severity of the infection process.…”