Submitted to: Virus Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2008
Publication Date: 6/4/2008
Citation: Schiotz, B.L., Jorgensen, S.M., Rexroad III, C.E., Gjoen, T., Krasnov, A. 2008. Transcriptomic analysis of responses to infectious salmon anemia virus infection in macrophage-like cells. Virus Research. 136:65-74. Interpretive Summary: The infectious salmon anemia virus (ISAV) is an aquatic orthomyxovirus (genus Isavirus) causing high mortalities in aquaculture worldwide. Although improved control management has reduced the number of outbreaks, it is still considered a major threat due to high risks of emergence of new pathogenic strains and asymptomatic infections in feral fish. ISAV causes a multisystemic disease characterized by high mortality with exophthalmia, pale gills, severe anemia, decreased hematocrit value, ascites and severe hemorrhagic necrosis of internal organs. The structural characteristics and viral binding and entry of ISAV are well described but the molecular and functional understanding of the host-pathogen interaction needs further investigation. To this end we investigated protective mechanisms induced by host cells and pathological alterations caused by ISAV with microarray analysis, which is regarded as one of the most promising approaches for systemic insight into cellular processes. We used a high-density salmonid fish microarray representing a large number of fish immune genes to characterize responses to pathogens and stressors. Our findings shed new light on the molecular basis of pathogenesis of cytopathic ISAV infection in a common target cell-type, provide foundation for further insight into virulence factors and potential protective host responses, and contribute to improved disease control of this important aquaculture disease.
Technical Abstract: The aquatic orthomyxovirus infectious salmon anemia virus (ISAV) is an important pathogen for salmonid aquaculture, however little is known about protective and pathological host responses to infection. We have investigated intracellular responses during cytopathic ISAV infection in the macrophage-like Atlantic salmon kidney (ASK) cell line by microarray analysis (1.8K SFA2.0 immunochip) and a functional assay for glutathione. Gene transcription changed rapidly and consistently with time and with minor differences between two virus isolates. While several pro-inflammatory and antiviral immune genes were induced, genes involved in cell signaling and integrity were down-regulated, suggesting isolation of infected cells from cell-to-cell interaction and responses to external signals. Differential expression of genes regulating cell cycle and apoptosis implied opposite cues from host cell and virus. This was in pace with massive down-regulation of genes involved in biosynthesis and processing of nucleotides and nucleic acids. Significant down-regulation of several genes involved in metabolism of reactive oxygen species suggested increased oxidative stress, which was confirmed by a functional assay showing reduced levels of glutathione during infection. Testing of expression data against a microarray database containing diverse experiments revealed candidate marker genes for ISAV infection. Our findings provide novel insight into cellular host responses and determinants for acute cytopathic ISAV infection.