T cells bite the hand that feeds them.
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Animals↗
Biomedical subjects
David C Tscharke
Publications and source records attributed to David C Tscharke.
The vaccinia virus kelch-like protein C2L affects calcium-independent adhesion to the extracellular matrix and inflammation in a murine intradermal model.
Chordate poxviruses encode several uncharacterized POZ-kelch proteins and three of these are present in Vaccinia virus (VV) strain Western Reserve. VV gene C2L is predicted to encode a protein of 512 amino acid residues with a POZ/BTB domain in the N-terminal region and three kelch motifs in the C-terminal half of the protein. We have identified the C2L gene product as an intracellular protein of 56 kDa and constructed and characterized a VV mutant lacking the C2L gene (v Delta C2L). Compared to wild-type and revertant viruses, v Delta C2L had unaltered growth in vitro, but had a different plaque morphology due to an altered cytopathic effect (CPE) of infected cells. Deleting C2L had no effect on VV-induced formation of actin tails or enhanced cell motility, but affected the development of VV-induced cellular projections and the Ca(2+)-independent cell/extracellular matrix adhesion late during infection. In an intranasal mouse model, C2L did not contribute to virus virulence. However, in an intradermal mouse model, infection with v Delta C2L resulted in larger lesions and more cell infiltration into the infected ears during recovery from infection. Thus, in this model, C2L protein inhibits inflammation and reduces immunopathology. In summary, we found that C2L is not required for virus replication in vitro but contributes to aspects of VV-induced CPE and reduces immunopathology in vivo.
Animals↗
The vaccinia virus C12L protein inhibits mouse IL-18 and promotes virus virulence in the murine intranasal model.
A bioassay that measured the interleukin (IL)-12-induced production of interferon (IFN)-gamma from mouse splenocytes was used to identify a soluble factor in the supernatants of vaccinia virus (VV)-infected cells that inhibited the production of IFN-gamma. This soluble factor was expressed by 14 out of 16 VV strains including the Western Reserve (WR) strain, but strains Copenhagen and Tashkent and a mutant of strain WR called 6/2 lacked this activity. The gene encoding this activity was identified as C12L by transferring DNA present in VV WR but missing in VV WR 6/2 into VV Copenhagen and testing for expression of the soluble factor. The C12L protein shows amino acid similarity to IL-18 binding proteins that are encoded by poxviruses, mice and humans, and C12L protein produced from VV or baculovirus inhibited the biological activity of mouse IL-18 in vitro. Thus the inhibition of IL-12-induced IFN-gamma production was due to indirect effects of C12L on IL-18, illustrating the synergistic action of these pro-inflammatory cytokines. To study the role of the C12L protein in the virus life-cycle, we constructed a deletion mutant lacking the C12L gene and a revertant virus in which the gene was reinserted into the deletion mutant. In vitro the replication and plaque size of these viruses were indistinguishable. However, infection of BALB/c mice by the intranasal route showed that the deletion mutant was attenuated and induced lower weight loss and signs of illness compared to controls.
Administration, Intranasal↗
The vaccinia virus B9R protein is a 6 kDa intracellular protein that is non-essential for virus replication and virulence.
Vaccinia virus (VV) strain Western Reserve gene B9R is shown to encode an intracellular 6 kDa protein that is expressed late during the infectious cycle. In vitro transcription and translation produced two polypeptides in the presence of microsomal membranes, but only the larger protein in the absence of membranes. The smaller protein sedimented with microsomes during centrifugation, suggesting it was inserted into the lipid membrane or into the microsomal lumen via the N-terminal hydrophobic signal sequence that was subsequently cleaved proteolytically. A VV mutant lacking B9R was constructed and found to replicate normally in cell culture and two in vivo models.
Base Sequence↗
A study of the vaccinia virus interferon-gamma receptor and its contribution to virus virulence.
Vaccinia virus (VV) strain Western Reserve gene B8R encodes a 43 kDa glycoprotein that is secreted from infected cells early in infection as a homodimer. This protein has amino acid similarity with the extracellular domain of cellular IFN-gamma receptor (IFN-gammaR) and binds and inhibits IFN-gamma from a wide range of species. Here we demonstrate that the B8R protein also inhibits equine IFN-gamma. The 5' end of the B8R mRNA has been mapped by primer extension analysis and the contribution of IFN-gammaRs to VV virulence was studied by the construction of a deletion mutant lacking the B8R gene (vDeltaB8R) and a revertant virus (vB8R-R) in which the B8R gene was re-inserted into the deletion mutant. A recombinant virus that expressed a soluble form of the mouse IFN-gammaR was also constructed and studied. The virulence of these viruses was tested in rodent models of infection. In mice, the loss of the VV IFN-gammaR did not affect virulence compared with WT and revertant viruses, consistent with the low affinity of the VV IFN-gammaR for mouse IFN-gamma. However, expression of the mouse soluble IFN-gammaR increased virus virulence slightly. In rabbit skin, loss of the VV IFN-gammaR produced lesions with histological differences compared with WT and revertant viruses. Lastly, the affinity constants of the VV IFN-gammaR for human and mouse IFN-gamma were determined by surface plasmon resonance.
Amino Acid Sequence↗
The vaccinia virus N1L protein is an intracellular homodimer that promotes virulence.
The vaccinia virus (VV) N1L gene encodes a protein of 14 kDa that was identified previously in the concentrated supernatant of virus-infected cells. Here we show that the protein is present predominantly (>90%) within cells rather than in the culture supernatant and it exists as a non-glycosylated, non-covalent homodimer. The N1L protein present in the culture supernatant was uncleaved at the N terminus and was released from cells more slowly than the VV A41L gene product, a secreted glycoprotein that has a conventional signal peptide. Bioinformatic analyses predict that the N1L protein is largely alpha-helical and show that it is conserved in many VV strains, in other orthopoxviruses and in members of other chordopoxvirus genera. However, database searches found no non-poxvirus proteins with significant amino acid similarity to N1L. A deletion mutant lacking the N1L gene replicated normally in cell culture, but was attenuated in intranasal and intradermal murine models compared to wild-type and revertant controls. The conservation of the N1L protein and the attenuated phenotype of the deletion mutant indicate an important role in the virus life-cycle.
Animals↗
Dermal infection with vaccinia virus reveals roles for virus proteins not seen using other inoculation routes.
Previously, we developed a model for testing the virulence and immunogenicity of vaccinia virus (VV) mutants based on the intradermal injection of BALB/c mouse ear pinnae. The model is characterized by a local infection in the inoculated skin without signs of systemic illness, mimicking dermal vaccination with VV. Here a further characterization of this model is presented, including the responses of mice to infectious virus doses as low as 10 p.f.u., a quantification of the infiltrate at the site of infection and use of different virus and mouse strains. The model was then used to compare the pathogenesis of six mutants of VV strain Western Reserve (WR) lacking genes A36R, A40R, A44L, B12R, B13R or B15R with that of appropriate control viruses. All of these genes except B12R and B15R influence the outcome of dermal infection with WR and for A40R and B13R this is the first role that has been reported after infection of mammals. A comparison of new and published results from intradermal and intranasal models is presented, showing that out of 16 gene deletion or insertion mutants of VV, half have phenotypes distinct from controls in only one of these models. Thus, the intranasal and intradermal models are complementary tools for dissecting the genetic basis of VV virulence.
Age Factors↗
Notes on transient host range selection for engineering vaccinia virus strain MVA.
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Cell Line↗
Vaccinia virus semaphorin A39R is a 50-55 kDa secreted glycoprotein that affects the outcome of infection in a murine intradermal model.
Vaccinia virus (VV) protein A39R has amino acid similarity to the extracellular domain of a glycosylphosphatidylinositol-linked cell surface semaphorin (SEMA7A/CDw108) that has an immunological expression profile and binding properties, thereby implicating A39R as an immunomodulator. Previously, a closely related A39R protein expressed by ectromelia virus was shown to induce cytokine production and up-regulate ICAM-1 expression in mouse monocytes in vitro. In this study, we show that the A39R gene of VV strain Copenhagen (COP) encodes a 50-55 kDa secreted glycoprotein and is expressed late during infection. The A39R protein was secreted by eight of 15 strains of VV, but not by strain Western Reserve (WR). To analyse the VV A39R function, several recombinant viruses were made, including an A39R deletion mutant of VV COP and a WR mutant containing the A39R sequence from COP. Loss of the gene from COP did not affect virus growth in vitro, or VV virulence in a mouse intranasal model, and had only a slight effect on lesion size in an intradermal model. In contrast, expression of COP A39R by VV WR was associated with an increase in the severity and persistence of skin lesions after intradermal infection of mice. Finally, a histological examination of mouse skin infected with recombinant viruses suggested that A39R has direct or indirect pro-inflammatory properties.
Amino Acid Sequence↗
The vaccinia virus A41L protein is a soluble 30 kDa glycoprotein that affects virus virulence.
Vaccinia virus (VV) gene A41L encodes an acidic protein with amino acid similarity to the 35 kDa protein of VV strain Lister, a soluble protein called vCKBP that binds CC chemokines, and to a protein from orf virus, called GIF, that binds GM-CSF and IL-2. However, despite the similarity, recombinant A41L protein was found not to bind these ligands or a variety of other chemoattractant molecules when tested using surface plasmon resonance. The A41L gene is expressed early and late during infection and encodes a 30 kDa protein that contains both N- and O-linked carbohydrate and is secreted from the infected cell. All 16 strains of VV and 2 strains of cowpox virus that were tested express the A41L protein, implying it has an important function for orthopoxviruses. Nonetheless, a VV strain Western Reserve deletion mutant lacking the A41L gene (vDeltaA41L) formed normal sized plaques and replicated to the same titre as wild-type and revertant viruses. The importance of the A41L protein in vivo was demonstrated in a mouse intradermal model in which infection with vDeltaA41L caused more severe lesions compared to wild-type and revertant viruses. Further examination in this model revealed that deletion of A41L enhanced clearance of infectious virus, suggesting that A41L expression reduces immunopathology. Consistent with this, histological examination of infected rabbit skin showed that the A41L protein could reduce the infiltration of inflammatory cells into the infected area. Together, these data suggest that the A41L protein constitutes a novel immunomodulatory protein.
Amino Acid Sequence↗
A model for vaccinia virus pathogenesis and immunity based on intradermal injection of mouse ear pinnae.
Vaccinia virus (VV) proteins that interfere with the host response to infection are of interest because they provide insight into virus-host relationships and may affect the safety and immunogenicity of recombinant VV (rVV) vaccines. Such vaccines need assessment in animal models and with this aim a model of VV infection based on intradermal injection of BALB/c ear pinnae was developed and characterized. In this model, the outcome of infection is affected by the dose of virus inoculated but virus spread is minimal and the mice suffer no signs of systemic illness. Cellular and humoral immune responses to these infections were measured readily and were independent of virus dose over a 100-fold range. Thus the model seems suitable for the analysis of the safety and immunogenicity of VV mutants lacking specific immunomodulatory proteins or bearing foreign antigens.
Animals↗