Unknown,Transcriptomics,Genomics,Proteomics

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Transcriptome profiling of immune responses to cardiomyopathy syndrome (CMS) in Atlantic salmon

ABSTRACT: Cardiomyopathy syndrome (CMS) is a disease associated with severe myocarditis in adult Atlantic salmon (Salmo salar L.), which is presumably caused with a double-stranded RNA virus (piscine myocarditis virus; PMCV). This study addressed the host immune response in Atlantic salmon during experimentally induced CMS as assessed by microarray transcriptome profiling. Post-smolts were infected by intraperitoneal injection of PMCV and developed cardiac pathology consistent with CMS. From analysis of heart samples at several time points and different tissues at early and clinical stages by oligonucleotide microarrays, six gene sets representing a broad range of immune responses were identified. Histopathological examination of cardiac tissue showed myocardial lesions from 6 weeks post infection (wpi) that peaked at 8-9 wpi and was followed by a recovery. Viral RNA was detected in all organs from 2 wpi. The highest and equal viral load was observed in heart, spleen and kidney, peaking at 8-9 wpi. Strong and systemic induction of antiviral and IFN-dependent genes from 2 wpi that leveled off during infection, was followed by a biphasic activation of pathways for B cells and MHC antigen presentation, both peaking at clinical pathology. This was preceded by a distinct cardiac activation of complement at 6 wpi. Most severe cardiac pathology and peak viraemia coincided with a cardiac-specific activation of T cell responses dominated by genes involved in effector CD8 cell responses and splenic induction of complement. These changes preceded the reduction in viral load and pathology, suggesting an important role of cytotoxic T cells for viral elimination in infected heart. Atlantic salmon post-smolts (average weight 50g) were challenged with the putative CMS-causing pathogen (PMCV). Hearts were sampled from challenged and control fish at 2, 4, 6, 8, 9 and 10 wpi. Pools of equal amounts of total RNA from three fish hearts each were combined and hybridized against control pools of 8 to 10 fish hearts per time point. Spleen, liver, mid-kidney, red blood cells (RBC) and peripheral blood leukocytes (PBL) were analyzed at 4 wpi (latest time point before clinical stage) and 8 wpi (peak pathology). The samples of infected fish were labeled with Cy5 and hybridized to control samples from the same time-points labeled with Cy3. Competitive hybridization to the arrays was followed by washing, scanning, image analysis, and data analysis. Selected genes were analyzed with RT-qPCR.

ORGANISM(S): Salmo salar

SUBMITTER: Aleksei Krasnov

PROVIDER: E-GEOD-28843 | 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.

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Transcriptome profiling of immune responses to cardiomyopathy syndrome (CMS) in Atlantic salmon

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