Unknown,Transcriptomics,Genomics,Proteomics

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Transcriptional response of Atlantic salmon (Salmo salar) after primary versus secondary exposure to Infectious Salmon Anemia Virus (ISAV)

ABSTRACT: Following an infection with a specific pathogen, the acquired immune system of many teleostean fish, including salmonids, is known to retain a specific memory of the infectious agent, which protects the host against subsequent infections. For example Atlantic salmon (Salmo salar), which have survived an infection with a low-virulence infectious salmon anemia virus (ISAV) isolate are less susceptible against subsequent infections with high-virulence ISAV isolates. A greater understanding of the mechanisms and immunological components involved in this acquired protection against ISAV is fundamental for the development of efficacious vaccines and treatments against this pathogen. To better understand the immunity components involved in this observed resistance, we have used an Atlantic salmon DNA microarray and RT-qPCR assays to study the global gene expression responses of preexposed Atlantic salmon (fish having survived an infection with a low-virulence ISAV isolate) during the course of a secondary infection with a high-virulence ISAV isolate Atlantic salmon which had survived a primary infection with a low-virulence ISAV isolate (preexposed H5R fish) were reinfected by cohabitation (H5Rc fish) or IP injection (H5Rip fish) with a high-virulence ISAV isolate and compared to preexposed H5R fish non-reinfected and naïve Atlantic salmon infected by cohabitation (Nc fish) with the high-virulence ISAV isolate using 4x44k Agilent arrays. H5Rc fish (n~6) and Nc fish (n~6) were sampled at 20d, 23d, 29d, 41d and 63d following the infection, while H5Rip fish (n~6) were sampled at 6h, 24h, 3d, 10d, 20d and 63d. Microarrays were performed using a 1-color approach

ORGANISM(S): Salmo salar

SUBMITTER: Francis LeBlanc

PROVIDER: E-GEOD-28357 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Infectious diseases among fish present an important economic burden for the aquaculture and fisheries industries around the world. For example, the infectious salmon anemia virus (ISAV) is known to infect farmed Atlantic salmon (Salmo salar), and results in millions of dollars of lost revenue to salmon farmers. Although improved management and husbandry practices over the last few years have minimized the losses and the number of outbreaks, the risk of new virulent isolates emerging is still a looming threat to the viability and sustainability of this industry. An understanding of the host-pathogen interactions at the molecular level during the course of an infection thus remains of strategic importance for the development of molecular tools and efficient vaccines capable of minimizing losses in the eventual case of a new outbreak. Using a 32 k cDNA microarray platform (cGRASP), we have studied various signaling pathways and immune regulated genes, activated or repressed, in Atlantic salmon head-kidney during the course of an ISAV infection. Gene expressions were measured at 5 different time-points: 6h, 24h, 3d, 7d and 16d post infection to get an overall view of changes as they occurred in time. The earliest time points showed only a few differentially expressed genes in infected fish, relative to controls, although as time progressed, many additional genes involved in key defense pathways were up-regulated including MHC type I, beta-2 microglobulin, TRIM 25 and CC-chemokine 19. During the latest stage of the infection process, many genes related to oxygen transportation were under-expressed, which correlates well with the anemia observed prior to death in Atlantic salmon infected with virulent strains of ISAV. Atlantic salmon smolts from 2 families of Atlantic salmon were IP injected with either 0.1mL of 10e5 TCID50 mL-1 of virus or 0.1mL of sham solution (L15 culture medium) and divided equally in four 1000 L tanks: 2 duplicate tanks containing ISAV injected fish and 2 duplicate control tanks containing sham solution injected fish. Four fish per family were sampled immediately prior to injection. An additional two fish per family per tank (four fish per family total) were sampled at 6h, 24h, 3d, 7d and 16d post injection. Head-kidney was dissected from each fish and used for microarray analysis. ISAV infected Atlantic salmon were compared to non-infected Atlantic salmon for each time-point.

Project description:Simple cost-effective bacterins are the earliest and most successfully used commercial vaccines in fish. In particular, those prepared from Yersinia ruckeri have proven effective at controlling Enteric Red Mouth Disease (ERM) and yersiniosis in rainbow trout and Atlantic salmon, respectively. However, the emergence of outbreaks of ERM caused by atypical biotypes of Y. ruckeri and reports of vaccine failure resulting in mass mortality of hatchery Atlantic salmon has reinvigorated interest in vaccines against fish bacterial diseases. Therefore the objective of this study was to identify surrogates of protection against yersiniosis using cDNA microarray to characterise the response of host genes in the gills of unvaccinated and vaccinated Atlantic salmon challenged with Y. ruckeri. Differentially expressed genes were identified using two-way ANOVA and restricted to those with >2.5-fold change at P<0.05. Using cDNA microarray we identified the expression of 6 genes in response to infection and 4 genes associated with the protective host response to yersiniosis. Analysis by real-time PCR confirmed that three immunologically relevant genes, namely a cathelicidin (47-fold) and a C-type lectin (19-fold) increased in response to yersiniosis. Including collagenase (17-fold increase), an important tissue remodelling and repair enzyme, these genes represent 3 of 6 non-protective and/or pathological responses to yersiniosis. Genes associated with the protective host response included an immunoglobulin gene and a selenoprotein that showed significant fold changes (15-fold increases each), highlighting the importance of antibody-mediated protection against yersiniosis. These findings provide much needed knowledge of the host-pathogen interaction in response to bacterial infection and immunisation in fish. Significantly, we identified a transcriptional biosignature consisting of predominantly immune-relevant genes (14 up and 3 down-regulated) in the gills of Atlantic salmon after immersion vaccination and before bacterial challenge. This biosignature may be used as a surrogate of protection and therefore as a predictor of vaccine success against yersiniosis. 36 microarray slides representing 6 individual fish (biological replicates) at 0 h (pre-challenge), 8 h, and 72 h post-challenge from both vaccinated and unvaccinated fish. Two-colour array using sample cDNA labelled with Cy5 and a common reference aRNA labelled with Cy3 hybridized to each slide.