Christel Moræus Olsen
Norwegian University of Life Sciences
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Featured researches published by Christel Moræus Olsen.
Veterinary Research | 2014
Øystein W. Finstad; Maria Krudtaa Dahle; Tone Hæg Lindholm; Ingvild Berg Nyman; Marie Løvoll; Christian Wallace; Christel Moræus Olsen; Anne K. Storset; Espen Rimstad
Piscine orthoreovirus (PRV) belongs to the Reoviridae family and is the only known fish virus related to the Orthoreovirus genus. The virus is the causative agent of heart and skeletal muscle inflammation (HSMI), an emerging disease in farmed Atlantic salmon (Salmo salar L.). PRV is ubiquitous in farmed Atlantic salmon and high loads of PRV in the heart are consistent findings in HSMI. The mechanism by which PRV infection causes disease remains largely unknown. In this study we investigated the presence of PRV in blood and erythrocytes using an experimental cohabitation challenge model. We found that in the early phases of infection, the PRV loads in blood were significantly higher than in any other organ. Most virus was found in the erythrocyte fraction, and in individual fish more than 50% of erythrocytes were PRV-positive, as determined by flow cytometry. PRV was condensed into large cytoplasmic inclusions resembling viral factories, as demonstrated by immunofluorescence and confocal microscopy. By electron microscopy we showed that these inclusions contained reovirus-like particles. The PRV particles and inclusions also had a striking resemblance to previously reported viral inclusions described as Erythrocytic inclusion body syndrome (EIBS). We conclude that the erythrocyte is a major target cell for PRV infection. These findings provide new information about HSMI pathogenesis, and show that PRV is an important factor of viral erythrocytic inclusions.
Veterinary Research | 2015
Øystein Wessel; Christel Moræus Olsen; Espen Rimstad; Maria Krudtaa Dahle
Piscine orthoreovirus (PRV) is a reovirus that has predominantly been detected in Atlantic salmon (Salmo salar L.). PRV is associated with heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon, and recently erythrocytes were identified as major target cells. The study of PRV replication and pathogenesis of the infection has been impeded by the inability to propagate PRV in vitro. In this study we developed an ex vivo cultivation system for PRV in Atlantic salmon erythrocytes. PRV was successfully passaged to naïve erythrocytes using lysates of blood cells from infected salmon. During cultivation a significant increase in viral load was observed by RT-qPCR and flow cytometry, which coincided with the formation of cytoplasmic inclusions. The inclusions resembled viral factories and contained both PRV protein and dsRNA. In addition, the erythrocytes generated an antiviral immune gene activation after PRV infection, with significant up-regulation of IFN-α, RIG-I, Mx and PKR transcripts. Supernatants from the first passage successfully transmitted virus to naïve erythrocytes. This study demonstrates that PRV replicates in Atlantic salmon erythrocytes ex vivo. The ex vivo infection model closely reflects the situation in vivo and can be used to study the infection and replication mechanisms of PRV, as well as the antiviral immune responses of salmonid erythrocytes.
Journal of Neuroscience Methods | 2007
Christoffer Lund; Christel Moræus Olsen; Heidi Tveit; Michael A. Tranulis
The monoclonal antibody (MAb) 3F4 has for nearly two decades been one of the most commonly used tools in prion research. This MAb has contributed significantly to our understanding of the normal cell biology of the prion protein (PrP(C)), as well as the disease related abnormalities occurring in prion diseases. The 3F4 antibody binds strongly to human and hamster PrP, with a specific requirement of two Met residues at positions 109 and 112 in the human PrP. Other species in which PrP lack one of the Met residues, like cattle and sheep, or both, like rat and mouse, do not react with the 3F4 antibody. These and other observations have led to the commonly accepted notion that the 3F4 epitope consists of the tetra-peptide Met-Lys-His-Met. In this study, we have identified the minimal epitope for 3F4 by studying its binding to synthetic peptides and by analysis of mutated ovine PrP::GFP constructs expressed in cell culture. We have found that the 3F4 epitope consists of a hepta-peptide (Lys-Thr-Asn-Met-Lys-His-Met), which in sheep encompass residues 109-115. We found that Lys 109 is critically important for 3F4 binding, as omission, or substitution of this residue to Ala resulted in no binding. We also demonstrate that the hepta-peptide constituting the minimal 3F4 epitope, can be used as a discrete, moveable high-affinity molecular tag. Thus, the 3F4 antibody can find its use beyond prion research.
Vaccine | 2013
Christel Moræus Olsen; Anand Kumar Pemula; Stine Braaen; Krishnan Sankaran; Espen Rimstad
The Salmonid alphavirus (SAV) is the etiological agent of pancreas disease in Atlantic salmon (Salmo salar) and Sleeping disease in rainbow trout (Oncorhynchus mykiss). SAV differs from alphaviruses infecting terrestrial animals in that it infects salmonid fish at low temperatures and does not use an arthropod vector for transmission. In this study we have shown that a SAVbased replicon could express proteins when driven by the subgenomic promoter in vitro in cells from fish, mammals and insects, as well as in vivo in shrimps (Litopanaeus vannamei). The SAV-replicon was found to be functional at temperatures ranging from 4 to 37°C. Protein expression was slow and moderate compared to that reported from terrestrial alphavirus replicons or from vectors where protein expression was under control of the immediate early CMV-promoter. No cytopathic effect was visually observable in cells transfected with SAV-replicon vectors. Double stranded RNA was present for several days after transfection of the SAV-replicon in fish cell lines and its presence was indicated also in shrimp. The combination of prolonged dsRNA production, low toxicity, and wide temperature range for expression, may potentially be advantageous for the use of the SAV replicon to induce immune responses in aquaculture of fish and shrimp.
Virus Research | 2013
Rimatulhana B. Ramly; Christel Moræus Olsen; Stine Braaen; Espen Rimstad
Infectious salmon anaemia virus (ISAV) is an orthomyxovirus causing anaemia and circulatory disease with high mortality in farmed Atlantic salmon (Salmo salar). Orthomyxoviruses are unusual as RNA viruses as they replicate in the nucleus and some viral transcripts undergo splicing. The nuclear replication necessitates a tightly controlled nuclear import and export of viral proteins. From ISAV genomic segment 7 two known mRNAs are transcribed; one collinear with the genomic segment, coding for the non-structural protein, and one spliced transcript, S7ORF2, coding for a protein with unknown function. Here we report initial functional analysis of the S7ORF2 protein. The results indicate that S7ORF2 protein gradually accumulates in the host cell during virus replication cycle, locates predominantly in the cytoplasm and is a part of purified virus particles. Trapping of S7ORF2 in the nucleus was obtained by treatment with leptomycin B, an inhibitor of CRM1-mediated nuclear export, indicating that S7ORF2 use CRM1 for the nuclear exit. Immunofluorescent staining of cells over-expressing both S7ORF2 and matrix protein (M) showed co-localization in the nucleus. However, S7ORF2 protein was found to interact with both the viral nucleoprotein (NP) and M proteins in ISAV infected cells as well as in purified viral particles. These results indicate that the S7ORF2 could be called the ISAV nuclear export protein, ISAV/NEP.
Journal of Biological Chemistry | 2009
Christoffer Lund; Christel Moræus Olsen; Susan Skogtvedt; Heidi Tveit; Kristian Prydz; Michael A. Tranulis
Cytoplasmic localization of the prion protein (PrP) has been observed in different species and cell types. We have investigated this poorly understood phenomenon by expressing fusion proteins of sheep prion protein and green fluorescent protein (GFPPrP) in N2a cells, with variable sequence context surrounding the start codon Met1. GFPPrP expressed with the wild-type sequence was transported normally through the secretory pathway to the cell surface with acquisition of N-glycan groups, but two N-terminal fragments of GFPPrP were detected intracellularly, starting in frame from Met17. When GFPPrP was expressed with a compromised Kozak sequence (GFPPrP*), dispersed intracellular fluorescence was observed. A similar switch from pericellular to intracellular PrP localization was seen when analogous constructs of sheep PrP, without inserted GFP, were expressed, showing that this phenomenon is not caused by the GFP tag. Western blotting revealed a reduction in glycosylated forms of GFPPrP*, whereas the N-terminal fragments starting from Met17 were still present. Formation of these N-terminal fragments was completely abolished when Met17 was replaced by Thr, indicating that leaky ribosomal scanning occurs for normal sheep PrP and that translation from Met17 is the cause of the aberrant cytoplasmic localization observed for a fraction of the protein. In contrast, the same phenomenon was not detected upon expression of similar constructs for mouse PrP. Analysis of samples from sheep brain allowed immunological detection of N-terminal PrP fragments, indicating that sheep PrP is subject to similar processing mechanisms in vivo.
PLOS ONE | 2016
Valentina Panzarin; Anna Toffan; Miriam Abbadi; Alessandra Buratin; Marzia Mancin; Stine Braaen; Christel Moræus Olsen; Luca Bargelloni; Espen Rimstad
Betanodaviruses are the causative agents of viral nervous necrosis (VNN), a devastating disease for the Mediterranean mariculture. Four different betanodavirus species are recognized, Striped jack-, Redspotted grouper-, Tiger puffer-, and Barfin flounder nervous necrosis virus (SJNNV, RGNNV, TPNNV and BFNNV), but there is little knowledge on their antigenic properties. In order to describe the serological relationships among different betanodavirus genotypes, serum neutralization assays were performed using rabbit polyclonal antisera against eight fish nodaviruses that cover a wide species-, temporal-, spatial- and genetic range. The results indicate that the SJNNV and RGNNV are antigenically distinct, constituting serotypes A and C, respectively. The TPNNV and BFNNV, the latter representing cold-water betanodaviruses, are antigenically related and cluster within serotype B. The reassortant viruses RGNNV/SJNNV and SJNNV/RGNNV group within serotypes A and C, respectively, indicating that the coat protein encoded by RNA2 acts as major immunoreactivity determinant. Immunostaining of in vitro expressed wild type and chimeric capsid proteins between the RGNNV and the SJNNV species indicated that the C-terminal part of the capsid protein retains the immunoreactive portion. The amino acid (aa) residues determining RGNNV and SJNNV antigenic diversity were mapped to aa residues 217–256 and aa 257–341, respectively. Neutralization of reverse genetics derived chimeric viruses indicated that these areas determine the neutralizing epitopes. The data obtained are crucial for the development of targeted serological tests for the diagnosis of VNN, and informative for development of cross-protective vaccines against various betanodavirus genotypes.
Viruses | 2016
Christel Moræus Olsen; Turhan Markussen; Bernd Thiede; Espen Rimstad
Infectious salmon anaemia virus (ISAV) is an orthomyxovirus infecting salmonid fish. The virus is adapted to low temperature and has a replication optimum between 10–15 °C. In this study the subcellular localization and protein interactions for the protein encoded by the largest open reading frame of gene segment 8 (s8ORF2) were investigated. In ISAV infected cells the s8ORF2 protein was found mainly in the cytosol but a minor fraction of cells expressed the protein in the nucleus as well. Green fluorescent protein-tagged s8ORF2 did not leak out of the cell when the plasma membrane was permeabilized, suggesting interactions with intracellular structural components. The s8ORF2 protein exists both as monomer and homodimer, and co-immunoprecipitation experiments strongly suggests it binds to the ISAV fusion-, nucleo- and matrix proteins. Two versions of s8ORF2 were detected with apparent molecular weights of 24–26 and 35 kDa in lysates of infected cells. The 35 kDa type is an early viral protein while the smaller version appears during the later phases of infection. The 24–26 kDa type was also the predominant form in viral particles. The s8ORF2 protein has previously been shown to bind RNA and interfere with interferon induction and signaling. Here we found that a fraction of the s8ORF2 protein pool in infected cells is likely to be conjugated to the interferon stimulated gene 15 (ISG15) and ubiquitin. Furthermore, several endogenous proteins pulled down by the s8ORF2 protein were identified by liquid chromatography mass spectrometry (LC-MS).
Virus Genes | 2018
Vandana Thukral; Bhavna Varshney; Rimatulhana B. Ramly; Sanket Singh Ponia; Sumona Karjee Mishra; Christel Moræus Olsen; Akhil C. Banerjea; Rana Zaidi; Espen Rimstad; Sunil K. Lal
The infectious salmon anaemia virus (ISAV) is a piscine virus, a member of Orthomyxoviridae family. It encodes at least 10 proteins from eight negative-strand RNA segments. Since ISAV belongs to the same virus family as Influenza A virus, with similarities in protein functions, they may hence be characterised by analogy. Like NS1 protein of Influenza A virus, s8ORF2 of ISAV is implicated in interferon antagonism and RNA-binding functions. In this study, we investigated the role of s8ORF2 in RNAi suppression in a well-established Agrobacterium transient suppression assay in stably silenced transgenic Nicotiana xanthi. In addition, s8ORF2 was identified as a novel interactor with SsMov10, a key molecule responsible for RISC assembly and maturation in the RNAi pathway. This study thus sheds light on a novel route undertaken by viral proteins in promoting viral growth, using the host RNAi machinery.
Viruses | 2015
Azila Abdullah; Christel Moræus Olsen; Kjartan Hodneland; Espen Rimstad
Vaccination is an important strategy for the control and prevention of infectious pancreatic necrosis (IPN) in farmed Atlantic salmon (Salmo salar) in the post-smolt stage in sea-water. In this study, a heterologous gene expression system, based on a replicon construct of salmonid alphavirus (SAV), was used for in vitro and in vivo expression of IPN virus proteins. The large open reading frame of segment A, encoding the polyprotein NH2-pVP2-VP4-VP3-COOH, as well as pVP2, were cloned and expressed by the SAV replicon in Chinook salmon embryo cells (CHSE-214) and epithelioma papulosum cyprini (EPC) cells. The replicon constructs pSAV/polyprotein (pSAV/PP) and pSAV/pVP2 were used to immunize Atlantic salmon (Salmo salar) by a single intramuscular injection and tested in a subsequent IPN virus (IPNV) challenge trial. A low to moderate protection against IPN was observed in fish immunized with the replicon vaccine that encoded the pSAV/PP, while the pSAV/pVP2 construct was not found to induce protection.
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International Centre for Genetic Engineering and Biotechnology
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