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Thorarinsson R, Ramstad A, Wolf JC, Sindre H, Skjerve E, Rimstad E, Evensen Ø, Rodriguez JF. Effect of pancreas disease vaccines on infection levels and virus transmission in Atlantic salmon ( Salmo salar) challenged with salmonid alphavirus, genotype 2. Front Immunol 2024; 15:1342816. [PMID: 38515753 PMCID: PMC10955579 DOI: 10.3389/fimmu.2024.1342816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Accepted: 02/21/2024] [Indexed: 03/23/2024] Open
Abstract
Salmonid alphavirus (SAV) causes pancreas disease (PD), which negatively impacts farmed Atlantic salmon. In this study, fish were vaccinated with a DNA-PD vaccine (DNA-PD) and an oil-adjuvanted, inactivated whole virus PD vaccine (Oil-PD). Controls were two non-PD vaccinated groups. Fish were kept in one tank and challenged by cohabitation with SAV genotype 2 in seawater. Protection against infection and mortality was assessed for 84 days (Efficacy study). Nineteen days post challenge (dpc), subgroups of fish from all treatment groups were transferred to separate tanks and cohabited with naïve fish (Transmission study 1) or fish vaccinated with a homologous vaccine (Transmission study 2), to evaluate virus transmission for 26 days (47 dpc). Viremia, heart RT-qPCR and histopathological scoring of key organs affected by PD were used to measure infection levels. RT-droplet digital PCR quantified shedding of SAV into water for transmission studies. The Efficacy study showed that PD associated growth-loss was significantly lower and clearance of SAV2 RNA significantly higher in the PD-DNA group compared to the other groups. The PD-DNA group had milder lesions in the heart and muscle. Cumulative mortality post challenge was low and not different between groups, but the DNA-PD group had delayed time-to-death. In Transmission study 1, the lowest water levels of SAV RNA were measured in the tanks containing the DNA-PD group at 21 and 34 dpc. Despite this, and irrespective of the treatment group, SAV2 was effectively transmitted to the naïve fish during 26-day cohabitation. At 47 dpc, the SAV RNA concentrations in the water were lower in all tanks compared to 34 dpc. In Transmission study 2, none of the DNA-PD immunized cohabitants residing with DNA-PD-vaccinated, pre-challenged fish got infected. In contrast, Oil-PD immunized cohabitants residing with Oil-PD-vaccinated, pre-challenged fish, showed infection levels similar to the naïve cohabitants in Transmission study 1. The results demonstrate that the DNA-PD vaccine may curb the spread of SAV infection as the DNA-PD vaccinated, SAV2 exposed fish, did not spread the infection to cohabiting DNA-PD vaccinated fish. This signifies that herd immunity may be achieved by the DNA-PD vaccine, a valuable tool to control the PD epizootic in farmed Atlantic salmon.
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Affiliation(s)
| | | | - Jeffrey C. Wolf
- Experimental Pathology Laboratories Inc., Sterling, VA, United States
| | | | - Eystein Skjerve
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | - Espen Rimstad
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | - Øystein Evensen
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
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2
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Vilatte A, Spencer-Milnes X, Jackson HO, Purton S, Parker B. Spray Drying Is a Viable Technology for the Preservation of Recombinant Proteins in Microalgae. Microorganisms 2023; 11:microorganisms11020512. [PMID: 36838478 PMCID: PMC9967251 DOI: 10.3390/microorganisms11020512] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 01/28/2023] [Accepted: 01/30/2023] [Indexed: 02/22/2023] Open
Abstract
Microalgae are promising host organisms for the production of encapsulated recombinant proteins such as vaccines. However, bottlenecks in bioprocess development, such as the drying stage, need to be addressed to ensure feasibility at scale. In this study, we investigated the potential of spray drying to produce a recombinant vaccine in microalgae. A transformant line of Chlamydomonas reinhardtii carrying a subunit vaccine against salmonid alphavirus was created via chloroplast engineering. The integrity of the recombinant protein after spray drying and its stability after 27 months storage at -80 °C, +4 °C and room temperature were assessed by immunoblotting. The protein withstood spray drying without significant losses. Long-term storage at +4 °C and room temperature resulted in 50% and 92% degradation, respectively. Optimizing spray drying and storage conditions should minimize degradation and favour short-term storage at positive temperatures. Using data on yield and productivity, the economics of spray drying- and freeze drying-based bioprocesses were compared. The drying stage corresponded to 41% of the total production cost. Process optimization, genetic engineering and new market strategies were identified as potential targets for cost reduction. Overall, this study successfully demonstrates the suitability of spray drying as a process option for recombinant protein production in microalgae at the industrial scale.
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Affiliation(s)
- Anaëlle Vilatte
- Department of Biochemical Engineering, University College London, Gower Street, London WC1E 6BT, UK
| | - Xenia Spencer-Milnes
- Department of Biochemical Engineering, University College London, Gower Street, London WC1E 6BT, UK
- Algal Research Group, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Harry Oliver Jackson
- Algal Research Group, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Saul Purton
- Algal Research Group, Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Brenda Parker
- Department of Biochemical Engineering, University College London, Gower Street, London WC1E 6BT, UK
- Correspondence:
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Emergence of Salmonid Alphavirus Genotype 2 in Norway-Molecular Characterization of Viral Strains Circulating in Norway and Scotland. Viruses 2021; 13:v13081556. [PMID: 34452421 PMCID: PMC8402823 DOI: 10.3390/v13081556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/27/2021] [Accepted: 07/29/2021] [Indexed: 12/30/2022] Open
Abstract
Pancreas disease (PD) and sleeping disease (SD), caused by an alphavirus, are endemic in European salmonid aquaculture, causing significant mortality, reduced growth and poor flesh quality. In 2010, a new variant of salmonid alphavirus emerged in Norway, marine salmonid alphavirus genotype 2 (SAV2). As this genotype is highly prevalent in Scotland, transmission through well boat traffic was hypothesized as one possible source of infection. In this study, we performed full-length genome sequencing of SAV2 sampled between 2006 and 2012 in Norway and Scotland, and present the first comprehensive full-length characterization of Norwegian marine SAV2 strains. We analyze their relationship with selected Scottish SAV2 strains and explore the genetic diversity of SAV. Our results show that all Norwegian marine SAV2 share a recent last common ancestor with marine SAV2 circulating in Scotland and a higher level of genomic diversity among the Scottish marine SAV2 strains compared to strains from Norway. These findings support the hypothesis of a single introduction of SAV2 to Norway sometime from 2006-2010, followed by horizontal spread along the coast.
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4
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Aksnes I, Braaen S, Markussen T, Åkesson CP, Villoing S, Rimstad E. Genetically modified attenuated salmonid alphavirus: A potential strategy for immunization of Atlantic salmon. JOURNAL OF FISH DISEASES 2021; 44:923-937. [PMID: 33591590 DOI: 10.1111/jfd.13352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/29/2021] [Accepted: 01/31/2021] [Indexed: 06/12/2023]
Abstract
Pancreas disease (PD) is a serious challenge in European salmonid aquaculture caused by salmonid alphavirus (SAV). In this study, we report the effect of immunization of Atlantic salmon with three attenuated infectious SAV3 strains with targeted mutations in a glycosylation site of the envelope E2 protein and/or in a nuclear localization signal in the capsid protein. In a pilot experiment, it was shown that the mutated viral strains replicated in fish, transmitted to naïve cohabitants and that the transmission had not altered the sequences. In the main experiment, the fish were immunized with the strains and challenged with SAV3 eight weeks after immunization. Immunization resulted in infection both in injected fish and 2 weeks later in the cohabitant fish, followed by a persistent but declining load of the mutated virus variants in the hearts. The immunized fish developed clinical signs and pathology consistent with PD prior to challenge. However, fish injected with the virus mutated in both E2 and capsid showed little clinical signs and had higher average weight gain than the groups immunized with the single mutated variants. The SAV strain used for challenge was not detected in the immunized fish indicating that these fish were protected against superinfection with SAV during the 12 weeks of the experiment.
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Affiliation(s)
- Ida Aksnes
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
| | - Stine Braaen
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
| | - Turhan Markussen
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
| | | | | | - Espen Rimstad
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Oslo, Norway
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LaPointe AT, Sokoloski KJ. De-Coding the Contributions of the Viral RNAs to Alphaviral Pathogenesis. Pathogens 2021; 10:pathogens10060771. [PMID: 34205345 PMCID: PMC8233893 DOI: 10.3390/pathogens10060771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/14/2021] [Accepted: 06/17/2021] [Indexed: 11/16/2022] Open
Abstract
Alphaviruses are positive-sense RNA arboviruses that are capable of causing severe disease in otherwise healthy individuals. There are many aspects of viral infection that determine pathogenesis and major efforts regarding the identification and characterization of virulence determinants have largely focused on the roles of the nonstructural and structural proteins. Nonetheless, the viral RNAs of the alphaviruses themselves play important roles in regard to virulence and pathogenesis. In particular, many sequences and secondary structures within the viral RNAs play an important part in the development of disease and may be considered important determinants of virulence. In this review article, we summarize the known RNA-based virulence traits and host:RNA interactions that influence alphaviral pathogenesis for each of the viral RNA species produced during infection. Overall, the viral RNAs produced during infection are important contributors to alphaviral pathogenesis and more research is needed to fully understand how each RNA species impacts the host response to infection as well as the development of disease.
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Affiliation(s)
- Autumn T. LaPointe
- Department of Microbiology and Immunology, School of Medicine, University of Louisville, Louisville, KT 40202, USA;
| | - Kevin J. Sokoloski
- Center for Predictive Medicine and Emerging Infectious Diseases, University of Louisville, Louisville, KT 40202, USA
- Correspondence:
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Tighe AJ, Gallagher MD, Carlsson J, Matejusova I, Swords F, Macqueen DJ, Ruane NM. Nanopore whole genome sequencing and partitioned phylogenetic analysis supports a new salmonid alphavirus genotype (SAV7). DISEASES OF AQUATIC ORGANISMS 2020; 142:203-211. [PMID: 33331288 DOI: 10.3354/dao03546] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Salmon pancreas disease virus, more commonly known as salmonid alphavirus (SAV), is a single-stranded positive sense RNA virus and the causative agent of pancreas disease and sleeping disease in salmonids. In this study, a unique strain of SAV previously isolated from ballan wrasse was subjected to whole genome sequencing using nanopore sequencing. In order to accurately examine the evolutionary history of this strain in comparison to other SAV strains, a partitioned phylogenetic analysis was performed to account for variation in the rate of evolution for both individual genes and codon positions. Partitioning the genome alignments almost doubled the observed branch lengths in the phylogenetic tree when compared to the more common approach of applying one model of substitution across the genome and significantly increased the statistical fit of the best-fitting models of nucleotide substitution. Based on the genomic data, a valid case can be made for the viral strain examined in this study to be considered a new SAV genotype. In addition, this study adds to a growing number of studies in which SAV has been found to infect non-salmonid fish, and as such we have suggested that the viral species name be amended to the more inclusive 'piscine alphavirus'.
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Affiliation(s)
- Andrew J Tighe
- Fish Health Unit, Marine Institute, Oranmore H91 R673, Ireland
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7
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Differential Alphavirus Defective RNA Diversity between Intracellular and Extracellular Compartments Is Driven by Subgenomic Recombination Events. mBio 2020; 11:mBio.00731-20. [PMID: 32817101 PMCID: PMC7439471 DOI: 10.1128/mbio.00731-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Our understanding of viral defective RNAs (D-RNAs), or truncated viral genomes, comes largely from passaging studies in tissue culture under artificial conditions and/or packaged viral RNAs. Here, we show that specific populations of alphavirus D-RNAs arise de novo and that they are not packaged into virions, thus imposing a transmission bottleneck and impeding their prior detection. This raises important questions about the roles of D-RNAs, both in nature and in tissue culture, during viral infection and whether their influence is constrained by packaging requirements. Further, during the course of these studies, we found a novel type of alphavirus D-RNA that is enriched intracellularly; dubbed subgenomic D-RNAs (sgD-RNAs), they are defined by deletion boundaries between the capsid-E3 region and the E1-3′ untranslated region (UTR) and are common to chikungunya, Mayaro, Sindbis, and Aura viruses. These sgD-RNAs are enriched intracellularly and do not appear to be selectively packaged, and additionally, they may exist as subgenome-derived transcripts. Alphaviruses are positive-sense RNA arboviruses that can cause either a chronic arthritis or a potentially lethal encephalitis. Like other RNA viruses, alphaviruses produce truncated, defective viral RNAs featuring large deletions during replication. These defective RNAs (D-RNAs) have primarily been isolated from virions after high-multiplicity-of-infection passaging. Here, we aimed to characterize both intracellular and packaged viral D-RNA populations during early-passage infections under the hypothesis that D-RNAs arise de novo intracellularly that may not be packaged and thus have remained undetected. To this end, we generated next-generation sequencing libraries using RNA derived from passage 1 (P1) stock chikungunya virus (CHIKV) 181/clone 25, intracellular virus, and P2 virions and analyzed samples for D-RNA expression, followed by diversity and differential expression analyses. We found that the diversity of D-RNA species is significantly higher for intracellular D-RNA populations than P2 virions and that specific populations of D-RNAs are differentially expressed between intracellular and extracellular compartments. Importantly, these trends were likewise observed in a murine model of CHIKV AF15561 infection, as well as in vitro studies using related Mayaro, Sindbis, and Aura viruses. Additionally, we identified a novel subtype of subgenomic D-RNA that is conserved across arthritogenic alphaviruses. D-RNAs specific to intracellular populations were defined by recombination events specifically in the subgenomic region, which were confirmed by direct RNA nanopore sequencing of intracellular CHIKV RNAs. Together, these studies show that only a portion of D-RNAs generated intracellularly are packaged and D-RNAs readily arise de novo in the absence of transmitted template.
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8
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Gallagher MD, Karlsen M, Petterson E, Haugland Ø, Matejusova I, Macqueen DJ. Genome Sequencing of SAV3 Reveals Repeated Seeding Events of Viral Strains in Norwegian Aquaculture. Front Microbiol 2020; 11:740. [PMID: 32390982 PMCID: PMC7193772 DOI: 10.3389/fmicb.2020.00740] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 03/30/2020] [Indexed: 01/14/2023] Open
Abstract
Understanding the dynamics of pathogen transfer in aquaculture systems is essential to manage and mitigate disease outbreaks. The goal of this study was to understand recent transmission dynamics of salmonid alphavirus (SAV) in Norway. SAV causes significant economic impacts on farmed salmonids in European aquaculture. SAV is classified into six subtypes, with Norway having ongoing epidemics of SAV subtypes 2 and 3. These two viral subtypes are present in largely distinct geographic regions of Norway, with SAV2 present in Trondelag, SAV3 in Rogaland, Sogn og Fjordane, and Hordaland, and Møre og Romsdal having outbreaks of both subtypes. To determine likely transmission routes of Norwegian SAV an established Nanopore amplicon sequencing approach was used in the current study. After confirming the accuracy of this approach for distinguishing subtype level co-infections of SAV2 and SAV3, a hypothetical possibility in regions of neighboring epidemics, twenty-four SAV3 genomes were sequenced to characterize the current genetic diversity of SAV3 in Norwegian aquaculture. Sequencing was performed on naturally infected heart tissues originating from a range of geographic locations sampled between 2016 and 2019. Phylogenetic analyses revealed that the currently active SAV3 strains sampled comprise several distinct lineages sharing an ancestor that existed ∼15 years ago (95% HPD, 12.51-17.7 years) and likely in Hordaland. At least five of these lineages have not shared a common ancestor for 7.85 years (95% HPD, 5.39-10.96 years) or more. Furthermore, the ancestor of the strains that were sampled outside of Hordaland (Sogn of Fjordane and Rogaland) existed less than 8 years ago, indicating a lack of long-term viral reservoirs in these counties. This evident lack of geographically distinct subclades is compatible with a source-sink transmission dynamic explaining the long-term movements of SAV around Norway. Such anthropogenic transport of the virus indicates that at least for sink counties, biosecurity strategies might be effective in mitigating the ongoing SAV epidemic. Finally, genomic analyses of SAV sequences were performed, offering novel insights into the prevalence of SAV genomes containing defective deletions. Overall, this study improves our understanding of the recent transmission dynamics and biology of the SAV epidemic affecting Norwegian aquaculture.
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Affiliation(s)
- Michael D. Gallagher
- School of Biological Sciences, University of Aberdeen, Aberdeen, United Kingdom
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Edinburgh, United Kingdom
| | | | | | | | - Iveta Matejusova
- Marine Laboratory, Marine Scotland Science, Aberdeen, United Kingdom
| | - Daniel J. Macqueen
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Edinburgh, United Kingdom
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9
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Gallagher MD, Matejusova I, Nguyen L, Ruane NM, Falk K, Macqueen DJ. Nanopore sequencing for rapid diagnostics of salmonid RNA viruses. Sci Rep 2018; 8:16307. [PMID: 30397226 PMCID: PMC6218516 DOI: 10.1038/s41598-018-34464-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 10/19/2018] [Indexed: 12/16/2022] Open
Abstract
Analysis of pathogen genome variation is essential for informing disease management and control measures in farmed animals. For farmed fish, the standard approach is to use PCR and Sanger sequencing to study partial regions of pathogen genomes, with second and third-generation sequencing tools yet to be widely applied. Here we demonstrate rapid and accurate sequencing of two disease-causing viruses affecting global salmonid aquaculture, salmonid alphavirus (SAV) and infectious salmon anaemia virus (ISAV), using third-generation nanopore sequencing on the MinION platform (Oxford Nanopore Technologies). Our approach complements PCR from infected material with MinION sequencing to recover genomic information that matches near perfectly to Sanger-verified references. We use this method to present the first SAV subtype-6 genome, which branches as the sister to all other SAV lineages in a genome-wide phylogenetic reconstruction. MinION sequencing offers an effective strategy for fast, genome-wide analysis of fish viruses, with major potential applications for diagnostics and robust investigations into the origins and spread of disease outbreaks.
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Affiliation(s)
- Michael D Gallagher
- School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Midlothian, EH25 9RG, United Kingdom
| | - Iveta Matejusova
- Marine Scotland Science, Marine Laboratory, Aberdeen, AB11 9DB, United Kingdom
| | - Lien Nguyen
- School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom
| | - Neil M Ruane
- Fish Health Unit, Marine Institute, Rinville Oranmore, Co, Galway, Ireland
| | - Knut Falk
- Norwegian Veterinary Institute, Ullevålsveien 68, 0454, Oslo, Norway
| | - Daniel J Macqueen
- School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, United Kingdom.
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Midlothian, EH25 9RG, United Kingdom.
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Pham PH, Tong WWL, Misk E, Jones G, Lumsden JS, Bols NC. Atlantic salmon endothelial cells from the heart were more susceptible than fibroblasts from the bulbus arteriosus to four RNA viruses but protected from two viruses by dsRNA pretreatment. FISH & SHELLFISH IMMUNOLOGY 2017; 70:214-227. [PMID: 28882807 DOI: 10.1016/j.fsi.2017.09.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 08/23/2017] [Accepted: 09/01/2017] [Indexed: 06/07/2023]
Abstract
Heart diseases caused by viruses are major causes of Atlantic salmon aquaculture loss. Two Atlantic salmon cardiovascular cell lines, an endothelial cell line (ASHe) from the heart and a fibroblast cell line (BAASf) from the bulbus arteriosus, were evaluated for their response to four fish viruses, CSV, IPNV, VHSV IVa and VHSV IVb, and the innate immune agonist, double-stranded RNA mimic poly IC. All four viruses caused cytopathic effects in ASHe and BAASf. However, ASHe was more susceptible to all four viruses than BAASf. When comparing between the viruses, ASHe cells were found to be moderately susceptible to CSV and VHSV IVb, but highly susceptible to IPNV and VHSV IVa induced cell death. All four viruses were capable of propagating in the ASHe cell line, leading to increases in virus titre over time. In BAASf, CSV and IPNV produced more than one log increase in titre from initial infection, but VHSV IVb and IVa did not. When looking at the antiviral response of both cell lines, Mx proteins were induced in ASHe and BAASf by poly IC. All four viruses induced Mx proteins in BAASf, while only CSV and VHSV IVb induced Mx proteins in ASHe. IPNV and VHSV IVa suppressed Mx proteins expression in ASHe. Pretreatment of ASHe with poly IC to allow for Mx proteins accumulation protected the culture from subsequent infections with IPNV and VHSV IVa, resulting in delayed cell death, reduced virus titres and reduced viral proteins expression. These data suggest that endothelial cells potentially can serve as points of infections for viruses in the heart and that two of the four viruses, IPNV and VHSV IVa, have mechanisms to avoid or downregulate antiviral responses in ASHe cells. Furthermore, the high susceptibility of the ASHe cell line to IPNV and VHSV IVa can make it a useful tool for studying antiviral compounds against these viruses and for general detection of fish viruses.
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Affiliation(s)
- Phuc H Pham
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Winnie W L Tong
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Ehab Misk
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Ginny Jones
- Elanco Canada Limited, Aqua Business R&D, Victoria, PEI, Canada
| | - John S Lumsden
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada; St. George's University, True Blue, Grenada
| | - Niels C Bols
- Department of Biology, University of Waterloo, Waterloo, ON, Canada.
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11
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Ramsey J, Mukhopadhyay S. Disentangling the Frames, the State of Research on the Alphavirus 6K and TF Proteins. Viruses 2017; 9:v9080228. [PMID: 28820485 PMCID: PMC5580485 DOI: 10.3390/v9080228] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Revised: 08/03/2017] [Accepted: 08/16/2017] [Indexed: 01/04/2023] Open
Abstract
For 30 years it was thought the alphavirus 6K gene encoded a single 6 kDa protein. However, through a bioinformatics search 10 years ago, it was discovered that there is a frameshifting event and two proteins, 6K and transframe (TF), are translated from the 6K gene. Thus, many functions attributed to the 6K protein needed reevaluation to determine if they properly belong to 6K, TF, or both proteins. In this mini-review, we reevaluate the past research on 6K and put those results in context where there are two proteins, 6K and TF, instead of one. Additionally, we discuss the most cogent outstanding questions for 6K and TF research, including their collective importance in alphavirus budding and their potential importance in disease based on the latest virulence data.
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Affiliation(s)
- Jolene Ramsey
- Department of Biology at Indiana University, Bloomington, IN 47405, USA.
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12
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Sánchez-Aparicio MT, Garcin D, Rice CM, Kolakofsky D, García-Sastre A, Baum A. Loss of Sendai virus C protein leads to accumulation of RIG-I immunostimulatory defective interfering RNA. J Gen Virol 2017; 98:1282-1293. [PMID: 28631605 PMCID: PMC5962894 DOI: 10.1099/jgv.0.000815] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 04/19/2017] [Indexed: 12/15/2022] Open
Abstract
Retinoic acid inducible gene (RIG-I)-mediated innate immunity plays a pivotal role in defence against virus infections. Previously we have shown that Sendai virus (SeV) defective interfering (DI) RNA functions as an exclusive and potent RIG-I ligand in DI-RNA-rich SeV-Cantell infected cells. To further understand how RIG-I is activated during SeV infection, we used a different interferon (IFN)-inducing SeV strain, recombinant SeVΔC, which, in contrast to SeV-Cantell is believed to stimulate IFN production due to the lack of the SeV IFN antagonist protein C. Surprisingly, we found that in SevΔC-infected cells, DI RNAs also functioned as an exclusive RIG-I ligand. Infections with wild-type SeV failed to generate any RIG-I-associated immunostimulatory RNA and this correlated with the lack of DI genomes in infected cells, as well as with the absence of cellular innate immune responses. Supplementation of the C protein in the context of SeVΔC infection led to a reduction in the number of DI RNAs, further supporting the potential role of the C protein as a negative regulator of DI generation and/or accumulation. Our findings indicate that limiting DI genome production is an important function of viral IFN antagonist proteins.
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Affiliation(s)
- Maria Teresa Sánchez-Aparicio
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Dominique Garcin
- Department of Genetics and Microbiology, University of Geneva School of Medicine, CMU, CH1211 Geneva, Switzerland
| | - Charles M. Rice
- Center for the Study of Hepatitis C, Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY 10065, USA
| | - Daniel Kolakofsky
- Department of Genetics and Microbiology, University of Geneva School of Medicine, CMU, CH1211 Geneva, Switzerland
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029, USA
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029, USA
- Department of Medicine Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Alina Baum
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY 10029, USA
- Present address: Regeneron Pharmaceuticals, Inc, 777 Old Saw Mill River Road, Tarrytown, NY 10591, USA
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Petterson E, Guo TC, Evensen Ø, Mikalsen AB. Experimental piscine alphavirus RNA recombination in vivo yields both viable virus and defective viral RNA. Sci Rep 2016; 6:36317. [PMID: 27805034 PMCID: PMC5090867 DOI: 10.1038/srep36317] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 10/07/2016] [Indexed: 11/22/2022] Open
Abstract
RNA recombination in non-segmented RNA viruses is important for viral evolution and documented for several virus species through in vitro studies. Here we confirm viral RNA recombination in vivo using an alphavirus, the SAV3 subtype of Salmon pancreas disease virus. The virus causes pancreas disease in Atlantic salmon and heavy losses in European salmonid aquaculture. Atlantic salmon were injected with a SAV3 6K-gene deleted cDNA plasmid, encoding a non-viable variant of SAV3, together with a helper cDNA plasmid encoding structural proteins and 6K only. Later, SAV3-specific RNA was detected and recombination of viral RNA was confirmed. Virus was grown from plasmid-injected fish and shown to infect and cause pathology in salmon. Subsequent cloning of PCR products confirming recombination, documented imprecise homologous recombination creating RNA deletion variants in fish injected with cDNA plasmid, corresponding with deletion variants previously found in SAV3 from the field. This is the first experimental documentation of alphavirus RNA recombination in an animal model and provides new insight into the production of defective virus RNA.
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Affiliation(s)
- Elin Petterson
- Norwegian University of Life Sciences, Faculty of Veterinary Medicine and Biosciences, P.O. Box 8146 Dep., N-0033 Oslo, Norway
| | - Tz-Chun Guo
- Norwegian University of Life Sciences, Faculty of Veterinary Medicine and Biosciences, P.O. Box 8146 Dep., N-0033 Oslo, Norway
| | - Øystein Evensen
- Norwegian University of Life Sciences, Faculty of Veterinary Medicine and Biosciences, P.O. Box 8146 Dep., N-0033 Oslo, Norway
| | - Aase B Mikalsen
- Norwegian University of Life Sciences, Faculty of Veterinary Medicine and Biosciences, P.O. Box 8146 Dep., N-0033 Oslo, Norway
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14
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Stene A, Hellebø A, Viljugrein H, Solevåg SE, Devold M, Aspehaug V. Liquid fat, a potential abiotic vector for horizontal transmission of salmonid alphavirus? JOURNAL OF FISH DISEASES 2016; 39:531-537. [PMID: 25952607 DOI: 10.1111/jfd.12382] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 03/29/2015] [Accepted: 03/29/2015] [Indexed: 06/04/2023]
Abstract
Viral diseases represent serious challenge in marine farming of Atlantic salmon (Salmo salar L). Pancreas disease (PD) caused by a salmonid alphavirus (SAV) is by far the most serious in northern Europe. To control PD, it is necessary to identify virus transmission routes. One aspect to consider is whether the virus is transported as free particles or associated with potential vectors. Farmed salmonids have high lipid content in their tissue which may be released into the environment from decomposing dead fish. At the seawater surface, the effects of wind and ocean currents are most prominent. The aim of this study was primarily to identify whether the lipid fraction leaking from dead infected salmon contains SAV. Adipose tissue from dead SAV-infected fish from three farming sites was submerged in beakers with sea water in the laboratory and stored at different temperature and time conditions. SAV was identified by real-time RT-PCR in the lipid fractions accumulating at the water surface in the beakers. SAV-RNA was also present in the sea water. Lipid fractions were transferred to cell culture, and viable SAV was identified. Due to its hydrophobic nature, fat with infective pathogenic virus at the surface may contribute to long-distance transmission of SAV.
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Affiliation(s)
- A Stene
- Ålesund University College, Ålesund, Norway
| | - A Hellebø
- Marine Department, Møreforsking AS, Ålesund, Norway
| | | | | | - M Devold
- PatoGen Analyse AS, Ålesund, Norway
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15
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Taksdal T, Jensen BB, Böckerman I, McLoughlin MF, Hjortaas MJ, Ramstad A, Sindre H. Mortality and weight loss of Atlantic salmon, Salmon salar L., experimentally infected with salmonid alphavirus subtype 2 and subtype 3 isolates from Norway. JOURNAL OF FISH DISEASES 2015; 38:1047-61. [PMID: 25322679 DOI: 10.1111/jfd.12312] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/20/2014] [Accepted: 08/20/2014] [Indexed: 05/13/2023]
Abstract
Pancreas disease (PD) caused by salmonid alphavirus (SAV) has a significant negative economic impact in the salmonid fish farming industry in northern Europe. Until recently, only SAV subtype 3 was present in Norwegian fish farms. However, in 2011, a marine SAV 2 subtype was detected in a fish farm outside the PD-endemic zone. This subtype has spread rapidly among fish farms in mid-Norway. The PD mortality in several farms has been lower than expected, although high mortality has also been reported. In this situation, the industry and the authorities needed scientific-based information about the virulence of the marine SAV 2 strain in Norway to decide how to handle this new situation. Atlantic salmon post-smolts were experimentally infected with SAV 2 and SAV 3 strains from six different PD cases in Norway. SAV 3-infected fish showed higher mortality than SAV 2-infected fish. Among the SAV 3 isolates, two isolates gave higher mortality than the third one. At the end of the experiment, fish in all SAV-infected groups had significantly lower weight than the uninfected control fish. This is the first published paper on PD to document that waterborne infection produced significantly higher mortality than intraperitoneal injection.
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Affiliation(s)
- T Taksdal
- Norwegian Veterinary Institute, Oslo, Norway
| | | | - I Böckerman
- Norwegian Veterinary Institute, Oslo, Norway
| | | | | | | | - H Sindre
- Norwegian Veterinary Institute, Oslo, Norway
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16
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Petterson E, Guo TC, Evensen Ø, Haugland Ø, Mikalsen AB. In vitro adaptation of SAV3 in cell culture correlates with reduced in vivo replication capacity and virulence to Atlantic salmon (Salmo salar L.) parr. J Gen Virol 2015; 96:3023-3034. [PMID: 26297344 DOI: 10.1099/jgv.0.000242] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Salmonid alphavirus (SAV) is the causative agent of pancreas disease affecting Atlantic salmon and rainbow trout and causes a major burden to the aquaculture industry. This study describes a Norwegian subtype SAV3 virus isolate (SAV3-H10) subjected to serial passages in Chinook salmon embryo cells (CHSE-214) followed by Asian Grouper skin cells (AGK). Two passages from CHSE and one after transfer to AGK cells were chosen for further investigation, based on variation in degree and development of cytopathic effect (CPE). After plaque purification, several in vitro studies were performed. Cell viability after infection, viral replication and ability to cause morphological changes in CHSE and AGK cells was studied for the three isolates. The AGK-transferred isolate was identified with the strongest abilities to reduce cell viability, replicate more and cause more CPE in cell culture when compared with the early and late CHSE-grown isolates. Subsequently, the isolates were tested in an experimental fish challenge, showing higher viral load and higher pathological score for the least cell-cultured isolate. Full-length sequencing of the viral genome of the three isolates revealed divergence in four amino acid positions and the AGK-grown isolate also had a 3 nt deletion in the 3'UTR. In conclusion, we show that cell culture of SAV3-H10 selects for strains inducing earlier CPE in vitro with increased viral replication. In vivo, the effect is reversed, with lower replication levels and lower pathology scores in target organs. This study outlines a path to identify potential virulence motifs of SAV3.
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Affiliation(s)
- Elin Petterson
- Norwegian University of Life Sciences, Department of Basic Science and Aquatic Medicine, PO Box 8146 Dep., 0033 Oslo, Norway
| | - Tz-Chun Guo
- Norwegian University of Life Sciences, Department of Basic Science and Aquatic Medicine, PO Box 8146 Dep., 0033 Oslo, Norway
| | - Øystein Evensen
- Norwegian University of Life Sciences, Department of Basic Science and Aquatic Medicine, PO Box 8146 Dep., 0033 Oslo, Norway
| | - Øyvind Haugland
- Norwegian University of Life Sciences, Department of Basic Science and Aquatic Medicine, PO Box 8146 Dep., 0033 Oslo, Norway
| | - Aase B Mikalsen
- Norwegian University of Life Sciences, Department of Basic Science and Aquatic Medicine, PO Box 8146 Dep., 0033 Oslo, Norway
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17
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The effect of dietary n-3/n-6 polyunsaturated fatty acid ratio on salmonid alphavirus subtype 1 (SAV-1) replication in tissues of experimentally infected rainbow trout (Oncorhynchus mykiss). Vet Microbiol 2015; 178:19-30. [DOI: 10.1016/j.vetmic.2015.04.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 04/01/2015] [Accepted: 04/20/2015] [Indexed: 01/05/2023]
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18
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de Aguiar MAM, Schneider DM, do Carmo E, Campos PRA, Martins AB. Error catastrophe in populations under similarity-essential recombination. J Theor Biol 2015; 374:48-53. [PMID: 25843218 DOI: 10.1016/j.jtbi.2015.03.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 02/24/2015] [Accepted: 03/24/2015] [Indexed: 10/23/2022]
Abstract
Organisms are often more likely to exchange genetic information with others that are similar to themselves. One of the most widely accepted mechanisms of RNA virus recombination requires substantial sequence similarity between the parental RNAs and is termed similarity-essential recombination. This mechanism may be considered analogous to assortative mating, an important form of non-random mating that can be found in animals and plants. Here we study the dynamics of haplotype frequencies in populations evolving under similarity-essential recombination. Haplotypes are represented by a genome of B biallelic loci and the Hamming distance between individuals is used as a criterion for recombination. We derive the evolution equations for the haplotype frequencies assuming that recombination does not occur if the genetic distance is larger than a critical value G and that mutation occurs at a rate μ per locus. Additionally, uniform crossover is considered. Although no fitness is directly associated to the haplotypes, we show that frequency-dependent selection emerges dynamically and governs the haplotype distribution. A critical mutation rate μc can be identified as the error threshold transition, beyond which this selective information cannot be stored. For μ<μc the distribution consists of a dominant sequence surrounded by a cloud of closely related sequences, characterizing a quasispecies. For μ>μc the distribution becomes uniform, with all haplotypes having the same frequency. In the case of extreme assortativeness, where individuals only recombine with others identical to themselves (G=0), the error threshold results μc=1/4, independently of the genome size. For weak assortativity (G=B-1)μc=2(-(B+1)) and for the case of no assortativity (G=B) μc=0. We compute the mutation threshold for 0<G<B and show that, for large B, it depends only on the ratio G/B. We discuss the consequences of these results for recombination in viruses and for speciation.
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Affiliation(s)
- Marcus A M de Aguiar
- Instituto de Física 'Gleb Wataghin', Universidade Estadual de Campinas, 13083-970, Campinas, SP, Brazil.
| | - David M Schneider
- Instituto de Física 'Gleb Wataghin', Universidade Estadual de Campinas, 13083-970, Campinas, SP, Brazil
| | - Eduardo do Carmo
- Universidade Federal da Integração Latino Americana, 85867-970 Foz do Iguaçu, PR, Brazil
| | - Paulo R A Campos
- Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil
| | - Ayana B Martins
- Instituto de Física 'Gleb Wataghin', Universidade Estadual de Campinas, 13083-970, Campinas, SP, Brazil; Instituto de Biociências, Universidade de São Paulo, 05508-090 São Paulo, SP, Brazil
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19
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Karlsen M, Andersen L, Blindheim SH, Rimstad E, Nylund A. A naturally occurring substitution in the E2 protein of Salmonid alphavirus subtype 3 changes viral fitness. Virus Res 2014; 196:79-86. [PMID: 25445347 DOI: 10.1016/j.virusres.2014.11.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 11/09/2014] [Accepted: 11/12/2014] [Indexed: 10/24/2022]
Abstract
Phylogenetic analyses of the Salmonid alphavirus subtype 3 (SAV3) epizootic have suggested that a substitution from proline to serine in the receptor binding protein E2 position 206 has occurred after the introduction of virus from a wild reservoir to farmed salmonid fish in Norway. We modelled the 3D structure of P62, the uncleaved E3-E2 precursor, of SAVH20/03 based on its sequence homology to the Chikungunya virus (CHIKV), and studied in vitro and in vivo effects of the mutation using reverse genetics. E2(206) is located on the surface of the B-domain of E2, which is associated with receptor attachment in alphaviruses. Recombinant virus expressing the E2(206S) codon replicated slower and produced significantly less genomic copies than virus expressing the ancestral E2(206P) codon in vitro in Bluegill Fry (BF2) cells. The E2(206S) mutant was out-competed by the E2(206P) mutant after 5 passages in an in vitro competition assay, confirming that the substitution negatively affects the efficacy of virus multiplication in cell culture. Both mutants were highly infectious to Atlantic salmon (Salmo salar), produced similar viral RNA loads in gills, heart, kidney and brain, and induced similar histopathologic changes in these organs. The E2(206S) mutant produced a less persistent infection in salmon and was shed more rapidly to water than the E2(206P) mutant. Reduced generation time through more rapid shedding could therefore explain why a serine in this position became dominant in the viral population after SAV3 was introduced to farmed salmon from the wild reservoir.
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Affiliation(s)
- Marius Karlsen
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway.
| | - Linda Andersen
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway
| | - Steffen H Blindheim
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway
| | - Espen Rimstad
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine and Biosciences, Norwegian University of Life Sciences, P.O. 8146 Dep, 0033 Oslo, Norway
| | - Are Nylund
- Department of Biology, University of Bergen, Thor Møhlens gt 55, 5020 Bergen, Norway
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20
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Schmidt-Posthaus H, Diserens N, Jankowska Hjortaas M, Knüsel R, Hirschi R, Taksdal T. First outbreak of sleeping disease in Switzerland: disease signs and virus characterization. DISEASES OF AQUATIC ORGANISMS 2014; 111:165-171. [PMID: 25266904 DOI: 10.3354/dao02766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Sleeping disease is a contagious disease mainly of freshwater farmed rainbow trout, caused by salmonid alphavirus (SAV) Subtype 2. Here we describe the first case in Switzerland. Pathological changes ranged from acute pancreas necrosis to more chronic lesions with complete loss of exocrine pancreas and simultaneous degenerative, inflammatory and regenerative heart and muscle lesions. The partial sequencing of SAV E2 and nsp3 genes placed the Swiss SAV variant within the Subtype 2 clustering together with freshwater isolates from UK and continental Europe. Although mortality stayed low, growth rates were significantly reduced, making the disease economically relevant.
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Affiliation(s)
- Heike Schmidt-Posthaus
- Centre for Fish and Wildlife Health, Department of Infectious Disease and Pathobiology, University of Berne, Laenggassstrasse 122, PO Box 8466, 3001 Berne, Switzerland
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21
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Mikalsen AB, Nilsen P, Frøystad-Saugen M, Lindmo K, Eliassen TM, Rode M, Evensen Ø. Characterization of a novel calicivirus causing systemic infection in atlantic salmon (Salmo salar L.): proposal for a new genus of caliciviridae. PLoS One 2014; 9:e107132. [PMID: 25203050 PMCID: PMC4159302 DOI: 10.1371/journal.pone.0107132] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 08/11/2014] [Indexed: 12/30/2022] Open
Abstract
The Caliciviridae is a family of viruses infecting humans, a wide range of animals, birds and marine fish and mammals, resulting in a wide spectrum of diseases. We describe the identification and genetic characterization of a novel calicivirus replicating in Atlantic salmon. The virus has a high prevalence in farmed salmon and is found in fish suffering from several diseases and conditions and also in presumable healthy fish. A challenge and vaccination trial shows that the calicivirus replicates in Atlantic salmon and establishes a systemic infection, which can be reduced by vaccination with formalin-inactivated virus preparation. The virus, named Atlantic salmon calicivirus (ASCV), is found in two genetically distinct variants, a cell culture isolated and a variant sequenced directly from field material. The genomes are 7,4 kb and contain two open reading frames where typical conserved amino acid motifs and domains predict a gene order reminiscent of calicivirus genomes. Phylogenetic analysis performed on extracted capsid amino acid sequences segregated the two ASCV variants in a unique cluster sharing root with the branch of noroviruses infecting humans and the unassigned Tulane virus and St-Valérien like viruses, infecting rhesus monkey and pig, respectively, with relatively large distance to the marine calicivirus subgroup of vesiviruses. Based on the analyses presented, the ASCV is predicted to represent a new genus of Caliciviridae for which we propose the name Salovirus.
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Affiliation(s)
- Aase B. Mikalsen
- Norwegian University of Life Sciences, Faculty of Veterinary Medicine and Biosciences, Dept. of Basic Sciences and Aquatic Medicine, Oslo, Norway
- * E-mail:
| | | | | | | | | | | | - Øystein Evensen
- Norwegian University of Life Sciences, Faculty of Veterinary Medicine and Biosciences, Dept. of Basic Sciences and Aquatic Medicine, Oslo, Norway
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22
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Guo TC, Johansson DX, Haugland Ø, Liljeström P, Evensen Ø. A 6K-deletion variant of salmonid alphavirus is non-viable but can be rescued through RNA recombination. PLoS One 2014; 9:e100184. [PMID: 25009976 PMCID: PMC4091863 DOI: 10.1371/journal.pone.0100184] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 05/23/2014] [Indexed: 01/13/2023] Open
Abstract
Pancreas disease (PD) of Atlantic salmon is an emerging disease caused by Salmonid alphavirus (SAV) which mainly affects salmonid aquaculture in Western Europe. Although genome structure of SAV has been characterized and each individual viral protein has been identified, the role of 6K protein in viral replication and infectivity remains undefined. The 6K protein of alphaviruses is a small and hydrophobic protein which is involved in membrane permeabilization, protein processing and virus budding. Because these common features are shared across many viral species, they have been named viroporins. In the present study, we applied reverse genetics to generate SAV3 6K-deleted (Δ6K) variant and investigate the role of 6K protein. Our findings show that the 6K-deletion variant of salmonid alphavirus is non-viable. Despite viral proteins of Δ6K variant are detected in the cytoplasm by immunostaining, they are not found on the cell surface. Further, analysis of viral proteins produced in Δ6K cDNA clone transfected cells using radioimmunoprecipitation (RIPA) and western blot showed a protein band of larger size than E2 of wild-type SAV3. When Δ6K cDNA was co-transfected with SAV3 helper cDNA encoding the whole structural genes including 6K, the infectivity was rescued. The development of CPE after co-transfection and resolved genome sequence of rescued virus confirmed full-length viral genome being generated through RNA recombination. The discovery of the important role of the 6K protein in virus production provides a new possibility for the development of antiviral intervention which is highly needed to control SAV infection in salmonids.
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Affiliation(s)
- Tz-Chun Guo
- Norwegian University of Life Sciences, Department of Basic Sciences and Aquatic Medicine, Oslo, Norway
| | - Daniel X. Johansson
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Øyvind Haugland
- Norwegian University of Life Sciences, Department of Basic Sciences and Aquatic Medicine, Oslo, Norway
| | - Peter Liljeström
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Øystein Evensen
- Norwegian University of Life Sciences, Department of Basic Sciences and Aquatic Medicine, Oslo, Norway
- * E-mail:
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23
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Luque A, González Granja A, González L, Tafalla C. Establishment and characterization of a rainbow trout heart endothelial cell line with susceptibility to viral hemorrhagic septicemia virus (VHSV). FISH & SHELLFISH IMMUNOLOGY 2014; 38:255-264. [PMID: 24698994 DOI: 10.1016/j.fsi.2014.03.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 02/19/2014] [Accepted: 03/07/2014] [Indexed: 06/03/2023]
Abstract
In the current work, we have established and characterized a novel cell line from rainbow trout (Oncorhynchus mykiss). The cell line, designated as RTH (rainbow trout heart), was obtained by immortalizing heart cells with recombinant retroviruses that transduced polyoma middle T antigen. This is the first time such a strategy is used to obtain an immortalized fish cell line. The cells showed an endothelial-like morphology and characteristics, constitutively transcribing collagen, selectin and VCAM (vascular cell adhesion molecule), as well as different chemokines and chemokine receptors, but not cytokeratin. As already described for heart endothelial cells, RTH cells actively phagocytized latex beads. Furthermore, RTH cells showed a high susceptibility to viral hemorrhagic septicemia virus (VHSV). VHSV modulated the transcription of Mx, major histocompatibility complex II (MHC-II), VCAM and many of the chemokine and chemokine receptors expressed in these cells. Therefore, RTH cells constitute an excellent model to study the immune regulation of endothelial cells in fish and their role in leukocyte extravasation.
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Affiliation(s)
- Alfonso Luque
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain
| | | | - Lucia González
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain
| | - Carolina Tafalla
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain.
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