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Dive into the research topics where Simon Chioma Weli is active.

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Featured researches published by Simon Chioma Weli.


Journal of Virology | 2012

Expression of the Infectious Salmon Anemia Virus Receptor on Atlantic Salmon Endothelial Cells Correlates with the Cell Tropism of the Virus

Maria Aamelfot; Ole Bendik Dale; Simon Chioma Weli; Erling Olaf Koppang; Knut Falk

ABSTRACT Infectious salmon anemia (ISA) is a World Organization for Animal Health (OIE)-listed disease of farmed Atlantic salmon, characterized by slowly developing anemia and circulatory disturbances. The disease is caused by ISA virus (ISAV) in the Orthomyxoviridae family; hence, it is related to influenza. Here we explore the pathogenesis of ISA by focusing on virus tropism, receptor tissue distribution, and pathological changes in experimentally and naturally infected Atlantic salmon. Using immunohistochemistry on ISAV-infected Atlantic salmon tissues with antibody to viral nucleoprotein, endotheliotropism was demonstrated. Endothelial cells lining the circulatory system were found to be infected, seemingly noncytolytic, and without vasculitis. No virus could be found in necrotic parenchymal cells. From endothelium, the virus budded apically and adsorbed to red blood cells (RBCs). No infection or replication within RBCs was detected, but hemophagocytosis was observed, possibly contributing to the severe anemia in fish with this disease. Similarly to what has been done in studies of influenza, we examined the pattern of virus attachment by using ISAV as a probe. Here we detected the preferred receptor of ISAV, 4-O-acetylated sialic acid (Neu4,5Ac2). To our knowledge, this is the first report demonstrating the in situ distribution of this sialic acid derivate. The pattern of virus attachment mirrored closely the distribution of infection, showing that the virus receptor is important for cell tropism, as well as for adsorption to RBCs.


Journal of Virology | 2006

Rabies Virus Infection of Primary Neuronal Cultures and Adult Mice: Failure To Demonstrate Evidence of Excitotoxicity

Simon Chioma Weli; Courtney A. Scott; Christopher A. Ward; Alan C. Jackson

ABSTRACT Cultures derived from the cerebral cortices and hippocampi of 17-day-old mouse fetuses infected with the CVS strain of rabies virus showed loss of trypan blue exclusion, morphological apoptotic features, and activated caspase 3 expression, indicating apoptosis. The NMDA (N-methyl-d-aspartate acid) antagonists ketamine (125 μM) and MK-801 (60 μM) were found to have no significant neuroprotective effect on CVS-infected neurons, while the caspase inhibitor Ac-Asp-Glu-Val aspartic acid aldehyde (25 μM) exerted a marked neuroprotective effect. Glutamate-stimulated increases in levels of intracellular calcium were reduced in CVS-infected hippocampal neurons. Ketamine (120 mg/kg of body weight/day intraperitoneally) given to CVS-infected adult mice produced no beneficial effects. We have found no supportive evidence that excitotoxicity plays an important role in rabies virus infection.


Journal of Virology | 2007

Therapy with Minocycline Aggravates Experimental Rabies in Mice

Alan C. Jackson; Courtney A. Scott; James S. Owen; Simon Chioma Weli; John P. Rossiter

ABSTRACT Minocycline is a tetracycline derivative with antiapoptotic and anti-inflammatory properties, and the drug has been shown to have beneficial effects in a variety of models of neurological disorders. The potentially neuroprotective role of minocycline was assessed in experimental in vitro and in vivo models of rabies virus infection. In this study, 5 nM minocycline did not improve the viability of embryonic mouse cortical and hippocampal neurons infected in vitro with the attenuated SAD-D29 strain of rabies virus, based on assessments using trypan blue exclusion. Two-day-old ICR mice were inoculated in the right hind limb thigh muscle with SAD-D29, and they received daily subcutaneous injections of either 50 mg/kg minocycline or vehicle (phosphate-buffered saline). Infected minocycline-treated mice experienced an earlier onset of neurologic signs and greater mortality (83% versus 50%) than those receiving vehicle (log rank test, P = 0.002 and P = 0.003, respectively). Immunohistochemical analysis of rabies virus antigen distribution was performed at early time points and in moribund mice. There were greater numbers of infected neurons in the regional brain areas of minocycline-treated mice than in vehicle-treated mice, which was significant in the CA1 region of the hippocampus. There was less apoptosis (P = 0.01) and caspase 3 immunostaining (P = 0.0008) in the midbrains of mice treated with minocycline than in mice treated with vehicle, consistent with a neuroprotective role of neuronal apoptosis that may have had a mild effect of inhibiting viral spread. Reduced infiltration of CD3+ T cells was observed in the pons/medulla of moribund mice that received minocycline therapy (P = 0.008), suggesting that the anti-inflammatory actions of minocycline may intensify the neurologic disease. These findings indicate that minocycline has important detrimental effects in the therapy of experimental rabies. Empirical therapy with minocycline should therefore be approached with caution in cases of human rabies and possibly other viral encephalitides until more experimental data become available.


Virology Journal | 2013

Infectious salmon anaemia virus infection of Atlantic salmon gill epithelial cells

Simon Chioma Weli; Maria Aamelfot; Ole Bendik Dale; Erling Olaf Koppang; Knut Falk

Infectious salmon anaemia virus (ISAV), a member of the Orthomyxoviridae family, infects and causes disease in farmed Atlantic salmon (Salmo salar L.). Previous studies have shown Atlantic salmon endothelial cells to be the primary targets of ISAV infection. However, it is not known if cells other than endothelial cells play a role in ISAV tropism. To further assess cell tropism, we examined ISAV infection of Atlantic salmon gill epithelial cells in vivo and in vitro. We demonstrated the susceptibility of epithelial cells to ISAV infection. On comparison of primary gill epithelial cell cultures with ISAV permissive fish cell cultures, we found the virus yield in primary gill epithelial cells to be comparable with that of salmon head kidney (SHK)-1 cells, but lower than TO or Atlantic salmon kidney (ASK)-II cells. Light and transmission electron microscopy (TEM) revealed that the primary gill cells possessed characteristics consistent with epithelial cells. Virus histochemistry showed that gill epithelial cells expressed 4-O-acetylated sialic acid which is recognized as the ISAV receptor. To the best of our knowledge, this is the first demonstration of ISAV infection in Atlantic salmon primary gill epithelial cells. This study thus broadens our understanding of cell tropism and transmission of ISAV in Atlantic salmon.


Developmental and Comparative Immunology | 2014

Transcriptional response of immune genes in gills and the interbranchial lymphoid tissue of Atlantic salmon challenged with infectious salmon anaemia virus.

Lars Austbø; Ida Bergva Aas; Melanie König; Simon Chioma Weli; Mohasina Syed; Knut Falk; Erling Olaf Koppang

Previously, it has been assumed that fish lack organized mucosa-associated lymphoid structures. Recently, an interbranchial lymphoid tissue (ILT) was described in salmonid gills at a site with substantial exposure to antigen. In this study, immune responses were examined in gills, mid-kidney and the laser-dissected ILT of Atlantic salmon (Salmo salar L.) infected with infectious salmon anaemia virus (ISAV). A strong innate response was observed in gills and mid-kidney and even in the laser-dissected ILT, despite the fact that no virus could be traced in this tissue. A small delayed increase in IgT transcripts, exclusively in the ILT, could indicate that this tissue has a role as a secondary lymphoid organ with clonal expansion of IgT expressing B-cells. Compared to the other examined tissues, gills displayed the earliest replication of the virus, further supporting this tissue as the main entry route for infection with ISAV.


Fish & Shellfish Immunology | 2012

A sequential study of incomplete Freund's adjuvant-induced peritonitis in Atlantic cod.

Mona Cecilie Gjessing; Knut Falk; Simon Chioma Weli; Erling Olaf Koppang; Agnar Kvellestad

Development of diagnostic and prophylactic methodologies is dependent on knowledge of the hosts defence system and reaction to different vaccine adjuvants. Here we present a sequential morphological study of peritonitis and inflammatory cell processing of incomplete Freunds adjuvant (IFA) in intraperitoneally injected Atlantic cod. The peritoneal tissue responses were characterised using necropsy, histology and electron microscopy. An extensive inflammatory response as characterised by leukocyte morphology and contents of enzymes, presence of apoptotic cells and IFN-γ-expressing cells was observed. Three days post injection, IFA droplets were surrounded by different types of inflammatory cells and two different patterns could be discerned. The first was characterised by flattened and concentrically arranged interdigitating cells connected by desmosomes and with macrophage-like cells (MLCs) predominant in the periphery. The second type possessed four stratified layers with an inner layer containing many apoptotic MLCs; a second layer containing flattened and shrunken cells and outer layers comprising moderately flattened cells and an outermost layer of mononuclear cells expressing IFN-γ. Oil was detected both inside and outside MLCs. The two types of processes, of which the second was clearly stratified, were similar to those observed in other teleosts, indicating a variety of reaction modes or alternatively sequential process development. The numerous dead MLCs contributed to inflammation.


Journal of Anatomy | 2013

Characterisation of a monoclonal antibody detecting Atlantic salmon endothelial and red blood cells, and its association with the infectious salmon anaemia virus cell receptor

Maria Aamelfot; Simon Chioma Weli; Ole Bendik Dale; Erling O. Koppang; Knut Falk

Endothelial cells (ECs) line the luminal surfaces of the cardiovascular system and play an important role in cardiovascular functions such as regulation of haemostasis and vasomotor tone. A number of fish and mammalian viruses target these cells in the course of their infection. Infectious salmon anaemia virus (ISAV) attacks ECs and red blood cells (RBCs) of farmed Atlantic salmon (Salmo salar L.), producing the severe disease of infectious salmon anaemia (ISA). The investigation of ISA has up to now been hampered by the lack of a functional marker for ECs in Atlantic salmon in situ. In this study, we report the characterisation and use of a novel monoclonal antibody (MAb) detecting Atlantic salmon ECs (e.g. vessel endothelium, endocardial cells and scavenger ECs) and RBCs. The antibody can be used with immunohistochemistry, IFAT and on Western blots. It appears that the epitope recognised by the antibody is associated with the ISAV cellular receptor. Besides being a tool to identify ECs in situ, it could be useful in further studies of the pathogenicity of ISA. Finally, the detection of an epitope shared by ECs and RBCs agrees with recent findings that these cells share a common origin, thus the MAb can potentially be used to study the ontogeny of these cells in Atlantic salmon.


PLOS ONE | 2018

Development and characterization of two cell lines from gills of Atlantic salmon

Mona Cecilie Gjessing; Maria Aamelfot; William N. Batts; Sylvie L. Benestad; Ole Bendik Dale; Even Thoen; Simon Chioma Weli; James R. Winton

Gill disease in Atlantic salmon, Salmo salar L., causes big losses in the salmon farming industry. Until now, tools to cultivate microorganisms causing gill disease and models to study the gill responses have been lacking. Here we describe the establishment and characterization of two cell lines from the gills of Atlantic salmon. Atlantic salmon gill cell ASG-10 consisted of cells staining for cytokeratin and e-cadherin and with desmosomes as seen by transmission electron microscopy suggesting the cells to be of epithelial origin. These structures were not seen in ASG-13. The cell lines have been maintained for almost 30 passages and both cell lines are fully susceptible to infection by infectious hematopoietic necrosis virus (IHNV), viral hemorrhagic septicemia virus (VHSV), infectious pancreatic necrosis virus (IPNV), Atlantic salmon reovirus TS (TSRV) and Pacific salmon paramyxovirus (PSPV). While infectious salmon anemia virus (ISAV) did not cause visible CPE, immunofluorescent staining revealed a sub-fraction of cells in both the ASG-10 and ASG-13 lines may be permissive to infection. ASG-10 is able to proliferate and migrate to close scratches in the monolayer within seven days in vitro contrary to ASG-13, which does not appear to do have the same proliferative and migratory ability. These cell lines will be useful in studies of gill diseases in Atlantic salmon and may represent an important contribution for alternatives to experimental animals and studies of epithelial–mesenchymal cell biology.


Acta Neuropathologica | 2006

Comparative pathogenesis of recombinant rabies vaccine strain SAD-L16 and SAD-D29 with replacement of Arg333 in the glycoprotein after peripheral inoculation of neonatal mice: less neurovirulent strain is a stronger inducer of neuronal apoptosis

Alan C. Jackson; Pamini Rasalingam; Simon Chioma Weli


Glycoconjugate Journal | 2014

The in situ distribution of glycoprotein-bound 4-O-Acetylated sialic acids in vertebrates

Maria Aamelfot; Ole Bendik Dale; Simon Chioma Weli; Erling Olaf Koppang; Knut Falk

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Knut Falk

National Veterinary Institute

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Ole Bendik Dale

National Veterinary Institute

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Erling Olaf Koppang

Norwegian University of Life Sciences

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Mona Cecilie Gjessing

National Veterinary Institute

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Sylvie L. Benestad

National Veterinary Institute

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Agnar Kvellestad

Norwegian University of Life Sciences

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Erling O. Koppang

Norwegian University of Life Sciences

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