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Gordon D. Harkiss - One of the best experts on this subject based on the ideXlab platform.
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Phenotypic characterisation and infection of ovine microglial cells with Maedi-Visna Virus
2013Co-Authors: Bahram Ebrahimi, John K Fazakerley, Gordon D. HarkissAbstract:Maedi-Visna Virus (MVV) infection of the central nervous system (CNS) results in pathological changes, the mechanisms of which are poorly understood. MVV preferentially infects cell of the monocyte/macrophage lineage in vivo. The neuroparenchymal microglial cells are the resident tissue macrophages in the CNS and therefore likely targets for MVV infection. However, no information is currently available on the susceptibility of these cells to MVV infection or their contribution to neuropathological changes as a result of MVV infection. Highly enriched primary ovine microglial cell cultures were set up from brain tissues of lambs. These cells were amoeboid or bipolar with spikes, a morphology consistent with microglial cells of other species, and stained positive for CD1, CD11a, CD11c, CD14, MHC-class I, MHC-class II, and b-N-acetyl galactose, but not with markers of astrocytes or oligodendrocytes. These sheep microglial cells were permissive for MVV infection. Productive MVV infection resulted in selective transcriptional upregulation of the pro-in¯ammatory cytokines TNFa and IL-6. In contrast, there was no change in levels of transcripts for TGFb1, IL-1b, GM-CSF, IL-10, or IL-12. These data provide the ®rst evidence that ovine microglial cells can support productive infection with MVV, and that this leads to a selective upregulation of proin¯ammatory cytokines. These may contribute to visn
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granulocyte macrophage colony stimulating factor is elevated in alveolar macrophages from sheep naturally infected with Maedi Visna virus and stimulates Maedi Visna virus replication in macrophages in vitro
Clinical and Experimental Immunology, 2002Co-Authors: Z Zhang, J Hopkins, Gordon D. Harkiss, C J WoodallAbstract:Infection by Maedi-Visna virus, a lentivirus of sheep, leads to chronic inflammatory reactions of various tissues. In this report we have analysed the role of specific cytokines in the disease process. A significant increase in expression of interleukin-6, interleukin-10, granulocyte macrophage-colony stimulating factor (GM-CSF) and transforming growth factor-beta1 mRNA was observed in alveolar macrophages isolated from the lungs of naturally infected animals when compared with lungs of seronegative controls. Levels of GM-CSF mRNA expression in alveolar macrophages correlated with the presence of lung lesions, but there was no correlation of interleukin-10, interleukin-6, tumour necrosis factor-alpha and transforming growth factor-beta1 mRNA levels in alveolar macrophages from animals with pulmonary lesions. In vitro investigation showed that GM-CSF in the range 0.1-10 ng/ml induced a significant increase in viral p25 production after 7 days in acutely infected blood monocyte-derived macrophages. The production of p25 peaked between 7 and 14 days exposure to 10 ng/ml of GM-CSF. Quantitative polymerase chain reaction showed that the level of viral DNA in monocyte-derived macrophages was dose-dependent following GM-CSF treatment in the range 0.1-100 ng/ml after 7 days. Viral mRNA expression was also enhanced. These findings indicate a role for GM-CSF in the pathogenesis of lymphoid interstitial pneumonia in infected animals.
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phenotypic characterisation and infection of ovine microglial cells with Maedi Visna virus
Journal of NeuroVirology, 2000Co-Authors: Bahrain Ebrahimi, Timothy E Allsopp, John K Fazakerley, Gordon D. HarkissAbstract:Maedi-Visna Virus (MVV) infection of the central nervous system (CNS) results in pathological changes, the mechanisms of which are poorly understood. MVV preferentially infects cell of the monocyte/macrophage lineage in vivo. The neuroparenchymal microglial cells are the resident tissue macrophages in the CNS and therefore likely targets for MVV infection. However, no information is currently available on the susceptibility of these cells to MVV infection or their contribution to neuropathological changes as a result of MVV infection. Highly enriched primary ovine microglial cell cultures were set up from brain tissues of lambs. These cells were amoeboid or bipolar with spikes, a morphology consistent with microglial cells of other species, and stained positive for CD1, CD11a, CD11c, CD14, MHC-class I, MHC-class II, and beta-N-acetyl galactose, but not with markers of astrocytes or oligodendrocytes. These sheep microglial cells were permissive for MVV infection. Productive MVV infection resulted in selective transcriptional up-regulation of the pro-inflammatory cytokines TNFalpha and IL-6. In contrast, there was no change in levels of transcripts for TGFbeta1, IL-1beta, GM-CSF, IL-10, or IL-12. These data provide the first evidence that ovine microglial cells can support productive infection with MVV, and that this leads to a selective up-regulation of proinflammatory cytokines. These may contribute to Visna neuropathology.
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neurotoxic mechanisms of transactivating protein tat of Maedi Visna virus
Neuroscience Letters, 1995Co-Authors: Paul J L M Strijbos, M R Zamani, Nancy J Rothwell, G W Arbuthnott, Gordon D. HarkissAbstract:Infection by lentiviruses such as human immunodeficiency virus (HIV) and Maedi-Visna virus (MVV) is associated with neurodegenerative disorders. We have investigated the neurotoxic mechanisms of a synthetic peptide of transactivating protein tat of MVV in striatal neuronal cultures. Tat peptide (but not control peptide) caused neuronal death, without affecting glial viability, in a time- and dose-dependent manner. Significant neuronal death was not observed until 6-8 h after tat peptide application (2.35-2350 nM), whereas half maximal and maximal cell death was observed after 12 and 24 h respectively. Tat peptide neurotoxicity could be partially inhibited by blockade of either N-methyl-D-aspartate (NMDA)- or non-NMDA receptors, suggesting that excessive neuroexcitation by glutamate or its analogues may contribute to tat-neurotoxicity. Furthermore, when both these glutamate receptor subtypes were blocked simultaneously, an increased degree of neuroprotection was observed. Finally, tat peptide toxicity was also reduced by blockade of L-type calcium channels. Calcium imaging revealed that intracellular calcium increases slowly upon tat application, predominantly due to entry of extracellular calcium. These results indicate that cellular calcium entry through voltage-gated calcium channels following activation of both NMDA and non-NMDA receptors, and subsequent accumulation of intracellular calcium may contribute to the neuronal death induced by tat protein.
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Neurotoxicity of peptide analogues of the transactivating protein tat from Maedi-Visna virus and human immunodeficiency virus
Neuroscience, 1993Co-Authors: M.r. Hayman, Gordon W. Arbuthnott, Gordon D. Harkiss, H. Brace, P. Filippi, V. Philippon, D. Thomson, R. Vigne, Ann K. WrightAbstract:Abstract Infection by lentiviruses such as human immunodeficiency virus, Maedi-Visna virus and Caprine Arthritis Encephalitis Virus, is associated with a variety of neurological syndromes, 4,5,10,18,19,22 but the mechanism by which the damage occurs to the nervous system is not known. The viruses do not infect neurons and so the neurotoxic actions must be mediated indirectly. Here we applied synthetic peptide analogues derived from basic regions of Maedi-Visna virus and human immunodeficiency virus transactivating protein, tat, to rat brain in vivo and found them to be potent neurotoxins. The toxicity of the Maedi-Visna virus peptide was demonstrated to be reduced by blockade of nitric oxide synthase and of N -methyl- d -aspartate channel opening. These experiments suggest that peptides derived from lentiviral tat may share a common neurotoxic action.
Lynn M Herrmannhoesing - One of the best experts on this subject based on the ideXlab platform.
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evaluation of a caprine arthritis encephalitis virus Maedi Visna virus indirect enzyme linked immunosorbent assay in the serological diagnosis of ovine progressive pneumonia virus in u s sheep
Clinical and Vaccine Immunology, 2010Co-Authors: Stephe N White, Katherine L Marshall, Liam E Oughtonneiswange, Kimberly C. Gouine, Michelle R. Mousel, Lynn M Herrmannhoesing, Gregory S. Lewis, Donald P KnowlesAbstract:A caprine arthritis-encephalitis virus (CAEV)/Maedi-Visna virus (MVV) indirect enzyme-linked immunosorbent assay (iELISA) was validated with samples from U.S. sheep and by the use of radioimmunoprecipitation as the standard for comparison. The sensitivity and the specificity were 86.0% (5.8%) and 95.9% (2.9%), respectively. The iELISA format and phylogenetic differences based on the MVV gag sequence contribute to the reduced sensitivity.
Valgerdur Andrésdóttir - One of the best experts on this subject based on the ideXlab platform.
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Maedi Visna virus persistence antigenic variation and latency
Comparative Immunology Microbiology and Infectious Diseases, 2017Co-Authors: H Arnarson, Margrét Gudnadóttir, Arnar Palsson, Valgerdur AndrésdóttirAbstract:Maedi-Visna virus (MVV), a lentivirus of sheep, shares with other lentiviruses the ability to establish a lifelong infection. In this study five sheep were infected intravenously with MVV and housed together with a number of uninfected sheep for natural transmission. All virus isolates from ten sheep that had been infected naturally had multiple mutations in the principal neutralization domain in Env and were antigenic variants, while three of four isolates from the carrier sheep had identical sequences to the infecting strain and were not antigenic variants. There was evidence of positive selection in the gene, particularly in amino acids comprising the neutralization epitope and some adjacent glycosylation sites. Together these results suggest that virus persistence is acquired by a reservoir of latent viruses, and that there is selection for antigenic variants of virus that is transmitted naturally.
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construction and characterization of an infectious molecular clone of Maedi Visna virus that expresses green fluorescent protein
Journal of Virological Methods, 2010Co-Authors: Holmfridur Sunna Gudmundsdottir, Katrin Olafsdottir, Sigridur Rut Franzdottir, Valgerdur AndrésdóttirAbstract:The construction of a molecular clone of Maedi-Visna virus (MVV) expressing the enhanced green fluorescent protein (EGFP) is described. The egfp gene was inserted into the gene for dUTPase since it has been shown that dUTPase is dispensable for MVV replication both in vitro and in vivo. MVV-egfp is infectious and EGFP expression is stable over at least six passages. This fluorescent virus will be a useful tool for monitoring MVV infections.
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duplicated sequence motif in the long terminal repeat of Maedi Visna virus extends cell tropism and is associated with neurovirulence
Journal of Virology, 2007Co-Authors: Thordur Oskarsson, Sigrídur Matthíasdóttir, Gudmundur Georgsson, Ólafur S. Andrésson, Gudrún Agnarsdóttir, Hulda S Hreggvidsdottir, Margret H Ogmundsdottir, Stefan R Jonsson, Sigurdur Ingvarsson, Valgerdur AndrésdóttirAbstract:Maedi-Visna virus (MVV) is a lentivirus of sheep causing chronic inflammatory disease of the lungs (Maedi) and the nervous system (Visna). We have previously shown that a duplicated sequence in the long terminal repeat (LTR) of MVV is a determinant of cell tropism. Here, we demonstrate that deletion of a CAAAT sequence from either one of the repeats resulted in poor virus growth in sheep choroid plexus cells. A duplication in the LTR encompassing the CAAAT sequence was found in four neurological field cases that were sequenced, but no duplication was present in the LTRs from seven Maedi cases; one Maedi isolate was mixed. These results indicate that the duplication in the LTR is associated with neurovirulence.
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mucosal vaccination with an attenuated Maedi Visna virus clone
Vaccine, 2005Co-Authors: Gudmundur Pétursson, Sigrídur Matthíasdóttir, Vilhjálmur Svansson, Gudmundur Georgsson, Valgerdur Andrésdóttir, Gudrún Agnarsdóttir, Agnes Helga Martin, Eyglo Gisladottir, Steinunn Arnadottir, Svava HognadottirAbstract:Four sheep were infected intratracheally with an attenuated molecular clone of Maedi-Visna virus (MVV). All four became infected. Ten months later these sheep were challenged intratracheally with a genetically similar but pathogenic clone of MVV. Four unvaccinated sheep were infected simultaneously. All sheep became infected by the challenge virus. The vaccinated sheep were not protected against superinfection with the challenge clone. However, virus was isolated more frequently from the blood of the unvaccinated controls than of the vaccinated animals and ten times more frequently from lungs of unvaccinated sheep than from lungs of vaccinated sheep at sacrifice, indicating partial protection.
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the vif gene of Maedi Visna virus is essential for infectivity in vivo and in vitro
Virology, 2004Co-Authors: Helga Bryndis Kristbjornsdottir, Sigurbjörg Torsteinsdóttir, Sigrídur Matthíasdóttir, Vilhjálmur Svansson, Valgerdur Andrésdóttir, Ólafur S. AndréssonAbstract:We have investigated the role of vif in Maedi-Visna virus (MVV), a lentivirus of sheep, by studying in vitro replication of vif-deleted MVV in several cell types, and the effects of vif deletion on in vivo infection. By measuring RT activity, we found that in comparison to wild-type MVV, growth of vif-deleted MVV was similar in fetal ovine synovial (FOS) cells, highly attenuated in sheep choroid plexus (SCP) cells, and not detectable in macrophages, natural target cells of MVV. Productive infection by vif-deleted MVV could not be demonstrated in sheep. An increased mutation frequency was observed in DNA produced by endogenous reverse transcription of viral RNA in vif-deleted virions, indicating the existence of a factor comparable in action to human APOBEC3G. These results suggest that the vif gene of MVV is essential for infectivity and that the Vif protein protects the viral genome from enpackaged mutagenic activities.
B A Blacklaws - One of the best experts on this subject based on the ideXlab platform.
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immune response to individual Maedi Visna virus gag antigens
Journal of Virology, 2006Co-Authors: Inderpal Singh, Ian Mcconnell, B A BlacklawsAbstract:The lesions caused by Maedi-Visna virus (MVV) are known to be immune mediated with a presumed contribution by the response to viral antigens. However, very little is known about the T-cell response to individual viral proteins. We have therefore expressed the three individual gag antigens of MVV strain EV1 (p16, p25, and p14) in a bacterial expression system and used the purified recombinant proteins to analyze the antibody and CD4+ T-cell response to MVV. Plasma samples were taken from sheep after 1 year of infection with MVV. The titers for antibodies in these samples were determined by indirect enzyme-linked immunosorbent assays and were as follows: anti-p25 antibody, 1:400 to >1:3,200; anti-p16 antibody, 1:400 to 1:3,200; and anti-p14 antibody, 1:<100 to 1:3,200. When the induction of antibodies was followed over time postinfection (p.i.), samples positive for anti-p25 were seen by day 24 p.i., followed by anti-p16 by day 45 p.i., and lastly anti-p14 by day 100 p.i. T-cell proliferative responses to all three gag antigens were detected in persistently infected sheep peripheral blood lymphocytes. The antigens were therefore used to raise T-cell lines from persistently infected sheep. These T-cell lines were shown to be specific for the recombinant gag antigens and for viral antigen expressed on infected macrophages. The proliferative response was restricted to major histocompatibility complex class II HLA-DR and so was due to CD4+ T lymphocytes. All three gag antigens may therefore play a role in immune-mediated lesion formation in MVV disease by presentation on infected macrophages in lesions.
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recombinant single chain fv antibodies that recognize the p25 protein of the Maedi Visna virus
Folia Microbiologica, 2003Co-Authors: Vladimir Celer, B A Blacklaws, Daniel Blazek, Iva Navratilova, Petr Skládal, R. BujdosoAbstract:Single chain Fv (scFv) antibodies (generated by phage display technology, molecules repre- senting new and efficient tools in the research and diagnostics of infectious diseases) against the capsid protein (p25) of Maedi-Visna virus were selected. Several clones of p25 specific scFv antibodies were iden- tified; one of them was expressed as a soluble scFv molecule, purified by immobilized metal-affinity chromatography and further characterized by sequencing and determination of the kinetic equilibrium asso- ciation constant. Sequence analysis showed that the rearranged VL and VH domains of the analyzed scFv clone used sequences from the VL3 family (germline DPL16/VL3.1) and VH1 family (germline VH20), res- pectively. The kinetic equilibrium association constant was determined as KA = 1.12 ± 0.52 L/µmol. Ovine lentiviruses (OvLV) represented by Maedi-Visna (MV) virus cause a slowly progressing disease characterized by interstitial pneumonia, encephalitis, indurative mastitis and non-suppurative arthri- tis (Gudnadottir 1974). The virus shows an affinity for cells of the monocyte/macrophage lineage (Gen- delman et al. 1986). It persists in animals despite cellular and humoral immune responses, with the majority of infected animals remaining asymptomatic for years. The identification of virus carriers in a flock can be based on culture or molecular techniques for the detection of virus-infected cells or the detection of specific conventional antibodies to MVV. The immunological response in infected animals confers no protection from the disease, and infection always persists for life. To date, numerous murine monoclonal antibodies
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Infection of Dendritic Cells by the Maedi-Visna Lentivirus
Journal of Virology, 2000Co-Authors: Susanna Ryan, Ian Mcconnell, Laurence Tiley, B A BlacklawsAbstract:The early stages of lentivirus infection of dendritic cells have been studied in an in vivo model. Maedi-Visna virus (MVV) is a natural pathogen of sheep with a tropism for macrophages, but the infection of dendritic cells has not been proven, largely because of the difficulties of definitively distinguishing the two cell types. Afferent lymphatic dendritic cells from sheep have been phenotypically characterized and separated from macrophages. Dendritic cells purified from experimentally infected sheep have been demonstrated not only to carry infectious MVV but also to be hosts of the virus themselves. The results of the in vivo infection experiments are supported by infections of purified afferent lymph dendritic cells in vitro, in which late reverse transcriptase products are demonstrated by PCR. The significance of the infection of afferent lymph dendritic cells is discussed in relation to the initial spread of lentivirus infection and the requirement for CD4 T cells.
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cytotoxic activity against Maedi Visna virus infected macrophages
Journal of Virology, 1994Co-Authors: W C Lee, I Mcconnell, B A BlacklawsAbstract:The cell type predominantly infected by Maedi-Visna virus (MVV) is the macrophage, and we have looked at the ability of MVV-infected macrophages to interact with cytotoxic T lymphocytes (CTL), important effector cells against virus infections. MVV-specific CTL precursors were detected, after in vitro culture with MVV antigen and recombinant human interleukin-2, in peripheral blood lymphocytes of all MVV-infected sheep. MVV-infected monocyte-derived macrophages and alveolar macrophages were able to stimulate CTL activity in vitro and were targets for these activated CTL. The major effector cell population using MVV-infected macrophage targets was CD8+ lymphocytes, although another population, lymphokine-activated killer cells, may also have been involved. There was no direct cytotoxic activity found in alveolar lymphocytes from MVV-infected sheep without lung lesions.
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circulating cytotoxic t lymphocyte precursors in Maedi Visna virus infected sheep
Journal of General Virology, 1994Co-Authors: B A Blacklaws, P Bird, Deborah J Allen, I McconnellAbstract:Maedi-Visna virus (MVV)-specific cytotoxic T lymphocytes (CTL) were detected, after in vitro culture with MVV antigen and recombinant human interleukin-2, in the efferent lymph and peripheral blood of sheep chronically infected with MVV. Cytotoxicity was mediated by CD8+ lymphocytes and was specific for particular strains of MVV. These precursor CTL were detected in the blood between day 23 and day 100 after infection via the skin. In one out of seven persistently infected sheep MVV-specific cytotoxicity was seen in uncultured peripheral blood cells. Again the effector population consisted of CD8+ lymphocytes. The only other viral infections in which CTL have been detected in peripheral blood mononuclear cells prior to secondary stimulation are those caused by the simian and human immunodeficiency viruses.
Ian Mcconnell - One of the best experts on this subject based on the ideXlab platform.
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immune response to individual Maedi Visna virus gag antigens
Journal of Virology, 2006Co-Authors: Inderpal Singh, Ian Mcconnell, B A BlacklawsAbstract:The lesions caused by Maedi-Visna virus (MVV) are known to be immune mediated with a presumed contribution by the response to viral antigens. However, very little is known about the T-cell response to individual viral proteins. We have therefore expressed the three individual gag antigens of MVV strain EV1 (p16, p25, and p14) in a bacterial expression system and used the purified recombinant proteins to analyze the antibody and CD4+ T-cell response to MVV. Plasma samples were taken from sheep after 1 year of infection with MVV. The titers for antibodies in these samples were determined by indirect enzyme-linked immunosorbent assays and were as follows: anti-p25 antibody, 1:400 to >1:3,200; anti-p16 antibody, 1:400 to 1:3,200; and anti-p14 antibody, 1:<100 to 1:3,200. When the induction of antibodies was followed over time postinfection (p.i.), samples positive for anti-p25 were seen by day 24 p.i., followed by anti-p16 by day 45 p.i., and lastly anti-p14 by day 100 p.i. T-cell proliferative responses to all three gag antigens were detected in persistently infected sheep peripheral blood lymphocytes. The antigens were therefore used to raise T-cell lines from persistently infected sheep. These T-cell lines were shown to be specific for the recombinant gag antigens and for viral antigen expressed on infected macrophages. The proliferative response was restricted to major histocompatibility complex class II HLA-DR and so was due to CD4+ T lymphocytes. All three gag antigens may therefore play a role in immune-mediated lesion formation in MVV disease by presentation on infected macrophages in lesions.
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Infection of Dendritic Cells by the Maedi-Visna Lentivirus
Journal of Virology, 2000Co-Authors: Susanna Ryan, Ian Mcconnell, Laurence Tiley, B A BlacklawsAbstract:The early stages of lentivirus infection of dendritic cells have been studied in an in vivo model. Maedi-Visna virus (MVV) is a natural pathogen of sheep with a tropism for macrophages, but the infection of dendritic cells has not been proven, largely because of the difficulties of definitively distinguishing the two cell types. Afferent lymphatic dendritic cells from sheep have been phenotypically characterized and separated from macrophages. Dendritic cells purified from experimentally infected sheep have been demonstrated not only to carry infectious MVV but also to be hosts of the virus themselves. The results of the in vivo infection experiments are supported by infections of purified afferent lymph dendritic cells in vitro, in which late reverse transcriptase products are demonstrated by PCR. The significance of the infection of afferent lymph dendritic cells is discussed in relation to the initial spread of lentivirus infection and the requirement for CD4 T cells.
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Early events in infection of lymphoid tissue by a lentivirus, Maedi-Visna
Trends in Microbiology, 1995Co-Authors: Pru Bird, Ian McconnellAbstract:Abstract All members of the lentivirus family infect cells of the monocyte-macrophage lineage, although this may be obscured during infection in vivo by the effect of the virus on other cells, such as CD4 + lymphocytes. Macrophages are the major cell type infected by the ruminant lentivirus Maedi-Visna, making it a valuable model for studying the pathogenesis of lentiviruses in these cells.
