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Avirulent Strains

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Bennie Osburn – One of the best experts on this subject based on the ideXlab platform.

  • sequential distribution of neurovirulent and Avirulent Strains of bluetongue virus in neonatal mice by rt pcr
    Archives of Virology, 1998
    Co-Authors: A W Brewer, Bennie Osburn


    Neurotropism of bluetongue virus (BLU) has been demonstrated in the developing brain of fetal ruminants and neonatal mouse models. Two Strains of BLU serotype 11, UC8 and UC2, differentiated by their electrophoretic characteristics and abilities to cause brain lesions in bovine fetuses and neonatal mice were investigated to determine differences in tissue distribution in new born mice following subcutaneous inoculation. Tissue analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) showed selective distribution of both BLU Strains to the brain and spleen as early as 3 h post-inoculation (PI) but viral RNA was not detected in the blood or other tissues for the duration of the 15 day experiment. UC2 persisted within the brain and spleen until 9 h PI without development of CNS lesions. In contrast, UC8 persisted within the spleen for 24 h and in the brain through the end of the experiment. UC8 infected mice developed necrotizing lesions throughout the cerebrum and cerebellum that were most severe on PI days 11 and 13. Immunohistochemical staining for BLU identified infected cells within the brains of UC8 inoculated mice before inflammatory lesions were present and gave supportive evidence of the ability of UC2 to infect brain cells. Our results show that both UC8 and UC2 selectively target the brain and spleen in neonatal mice early after inoculation and suggest that the differences in neurovirulence between these Strains are due to differences in replicative efficacy within host target cells.

  • infection of bovine fetuses at 120 days gestation with virulent and Avirulent Strains of bluetongue virus serotype 11
    Comparative Immunology Microbiology and Infectious Diseases, 1992
    Co-Authors: Bennie Osburn, Andreas S Waldvogel, G A Anderson, D L Phillips


    Abstract Bluetongue virus infection in sheep and cattle during fetal development causes neuropathology. Two Strains of bluetongue virus serotype 11 designated as UC-2 and UC-8 have different virulence patterns in newborn mice. These viruses have distinctly different electropherotype patterns on polyacrylamide gel electrophoresis indicating a genetic difference in these two viruses of the same serotype. Four bovine fetuses each were inoculated intramuscularly with either UC-2 or UC-8, and one fetus was inoculated with placebo. The inoculation was made intramuscularly through the uterine wall at 120 days’ gestation, and the bovine fetuses were recovered by cesarean section 12 or 20 days after inoculation. Fetal blood was collected for virus isolation and serology. Virus was reisolated from brain, blood, lung and liver. Both Strains, UC-2 and UC-8, cause severe lesions in the 120 day fetuses. The encephalomalacic lesions occurred earlier and were more severe in fetuses inoculated with UC-8 as compared to those inoculated with UC-2. The subtle differences observed in the fetuses inoculated with the two different Strains suggest that there is a difference in pathogenic potential of the two viruses. These differences do not appear to be completely dependent upon the host species.

Laura L Brown – One of the best experts on this subject based on the ideXlab platform.

  • molecular characterization and quantitative analysis of superoxide dismutases in virulent and Avirulent Strains of aeromonas salmonicida subsp salmonicida
    Journal of Bacteriology, 2003
    Co-Authors: Andrew Dacanay, Stewart C Johnson, R Bjornsdottir, Roger O Ebanks, Neil W Ross, Michael Reith, Rama K Singh, Laura L Brown


    Aeromonas salmonicida subsp. salmonicida is a facultatively intracellular gram-negative bacterium that is the etiological agent of furunculosis, a bacterial septicemia of salmonids that causes significant economic loss to the salmon farming industry. The mechanisms by which A. salmonicida evades intracellular killing may be relevant in understanding virulence and the eventual design of appropriate treatment strategies for furunculosis. We have identified two open reading frames (ORFs) and related upstream sequences that code for two putative superoxide dismutases (SODs), sodA and sodB. The sodA gene encoded a protein of 204 amino acids with a molecular mass of approximately 23.0 kDa (SodA) that had high similarity to other prokaryotic Mn-SODs. The sodB gene encoded a protein of 194 amino acids with a molecular mass of approximately 22.3 kDa that had high similarity to other prokaryotic Fe-SODs. Two enzymes with activities consistent with both these ORFs were identified by inhibition of O2−-catalyzed tetrazolium salt reduction in both gels and microtiter plate assays. The two enzymes differed in their expression patterns in in vivo- and in vitro-cultured bacteria. The regulatory sequences upstream of putative sodA were consistent with these differences. We could not identify other SOD isozymes such as sodC either functionally or through data mining. Levels of SOD were significantly higher in virulent than in Avirulent Strains of A. salmonicida subsp. salmonicida strain A449 when cultured in vitro and in vivo.

Martin A Hofmann – One of the best experts on this subject based on the ideXlab platform.

  • analysis of classical swine fever virus replication kinetics allows differentiation of highly virulent from Avirulent Strains
    Veterinary Microbiology, 2000
    Co-Authors: Christian Mittelholzer, Christian Moser, Jonduri Tratschin, Martin A Hofmann


    To study the replication of classical swine fever virus (CSFV) in cell culture, kinetics of viral plus-strand RNA synthesis, of viral structural and non-structural protein expression as well as of secreted and cell-associated infectious virus were determined. Highly virulent, moderately virulent and Avirulent Strains that were tested in standardized animal experiments to confirm their virulence were used to search for in vitro parameters allowing the differentiation of Strains according to their virulence. No significant qualitative or quantitative differences were found between the Strains studied when either RNA replication or protein synthesis were investigated. However, the ratio of cell-associated virus versus secreted virus proved to be considerably lower for the highly virulent Strains when compared to Avirulent or moderately virulent Strains. These data suggest that highly virulent Strains of CSFV can be distinguished in cell culture from Strains with reduced virulence.