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Philip Griebel

Publications and source records attributed to Philip Griebel.

7 recordsLinked to original sources
PubMed2006

Insights into gene expression changes impacting B-cell transformation: cross-species microarray analysis of bovine leukemia virus tax-responsive genes in ovine B cells.

Large-animal models for leukemia have the potential to aid in the understanding of networks that contribute to oncogenesis. Infection of cattle and sheep with bovine leukemia virus (BLV), a complex retrovirus related to human T-cell leukemia virus type 1 (HTLV-1), is associated with the development of B-cell leukemia. Whereas the natural disease in cattle is characterized by a low tumor incidence, experimental infection of sheep leads to overt leukemia in the majority of infected animals, providing a model for studying the pathogenesis associated with BLV and HTLV-1. Tax(BLV), the major oncoprotein, initiates a cascade of events leading toward malignancy, although the basis of transformation is not fully understood. We have taken a cross-species ovine-to-human microarray approach to identify Tax(BLV)-responsive transcriptional changes in two sets of cultured ovine B cells following retroviral vector-mediated delivery of Tax(BLV). Using cDNA-spotted microarrays comprising 10,336 human genes/expressed sequence tags, we identified a cohort of differentially expressed genes, including genes related to apoptosis, DNA transcription, and repair; proto-oncogenes; cell cycle regulators; transcription factors; small Rho GTPases/GTPase-binding proteins; and previously reported Tax(HTLV-1)-responsive genes. Interestingly, genes known to be associated with human neoplasia, especially B-cell malignancies, were extensively represented. Others were novel or unexpected. The results suggest that Tax(BLV) deregulates a broad network of interrelated pathways rather than a single B-lineage-specific regulatory process. Although cross-species approaches do not permit a comprehensive analysis of gene expression patterns, they can provide initial clues for the functional roles of genes that participate in B-cell transformation and pinpoint molecular targets not identified using other methods in animal models.

Animals↗
PubMed2005

Transcriptional analysis of avian embryonic tissues following infection with avian infectious bronchitis virus.

Avian infectious bronchitis virus (IBV) infection is one of the major viral respiratory diseases of chickens. Better understanding of the molecular basis of viral pathogenesis should contribute significantly towards the development of improved prophylactic, therapeutic and diagnostic reagents to control infections. In the present investigation, transcriptional profiles were analyzed by using RNA recovered from the lung tissue of IBV infected 18-day-old chicken embryos at 6, 24, 48 and 72 h post IBV infection. This microarray analysis was completed using avian cDNA arrays comprised of fragments of 1191 unique chicken and turkey gene transcripts. These arrays were generated from normalized cDNA subtraction libraries that were derived from avian pneumovirus (APV) infected chicken embryo fibroblast (CEF) cultures and tissues obtained from APV infected turkeys subtracted with their respective uninfected cultures and tissues. Of the 1191 unique genes represented on the array, the expression of a total of 327 genes (27% of total) were altered by two-fold or more from 6 through 72 h post-infection. A comparative analysis of IBV regulated genes with genes previously reported to change in expression following infection with other avian respiratory viruses revealed both conserved and unique changes. Real-time qRT-PCR was used to confirm the regulated expression of genes related to several functional classes including kinases, interferon induced genes, chemokines and adhesion molecules, vesicular trafficking and fusion protein genes, extracellular matrix protein genes, cell cycle, metabolism, cell physiology and development, translation, RNA binding, lysosomal, protein degradation and ubiquitination related genes. Microarray analysis served as an efficient tool in facilitating a comparative analysis of avian respiratory viral infections and provided insight into host transcriptional changes that were conserved as well as those which were unique to individual pathogens.

Animals↗
PubMed2003

Disruption of B-cell homeostatic control mediated by the BLV-Tax oncoprotein: association with the upregulation of Bcl-2 and signaling through NF-kappaB.

Transactivating proteins associated with complex onco-retroviruses including human T-cell leukemia virus-1 (HTLV-1) and bovine leukemia virus (BLV) mediate transformation using poorly understood mechanisms. To gain insight into the processes that govern tumor onset and progression, we have examined the impact of BLV-Tax expression on ovine B-cells, the targets of BLV in experimentally infected sheep, using B-cell clones that are dependent on CD154 and gammac-common cytokines. Tax was capable of mediating progression of B-cells from cytokine dependence to cytokine independence, indicating that the transactivator can over-ride signaling pathways typically controlled by cytokine receptor activation in B-cells. When examined in the presence of both CD154 and interleukin-4, Tax had a clear supportive role on B-cell growth, with an impact on B-cell proliferation, cell cycle phase distribution, and survival. Apoptotic B-cell death mediated by growth factor withdrawal, physical insult, and NF-kappaB inhibition was dramatically reduced in the presence of Tax. Furthermore, the expression of Tax was associated with higher Bcl-2 protein levels, providing rationale for the rescue signals mediated by the transactivator. Finally, Tax expression in B-cells led to a dramatic increase of nuclear RelB/p50 and p50/p50 NF-kappaB dimers, indicating that cellular signaling through NF-kappaB is a major contributory mechanism in the disruption of B-cell homeostasis. Although Tax is involved in aspects of pathogenesis that are unique to complex retroviruses, the viral strategies associated with this transactivating oncoprotein may have wide-ranging effects that are relevant to other B-cell malignancies.

Animals↗
PubMed2003

Innate immune responses induced by CpG oligodeoxyribonucleotide stimulation of ovine blood mononuclear cells.

Examples exist in the literature that demonstrate that treatment with immunostimulatory cytosine-phosphate-guanosine (CpG)-DNA can protect mice against infection by intracellular pathogens. There are, however, few studies reporting that CpG-DNA offers similar disease protection in other species. In this study, we assessed the potential of a class A and class B CpG oligodeoxynucleotide (ODN) to induce innate immune responses in sheep, an outbred species. Using peripheral blood mononuclear cells, we have for the first time demonstrated CpG-ODN-induced innate immune responses, including natural-killer-like activity [non-major histocompatibility complex (MHC)-restricted cytotoxicity], interferon-alpha secretion and 2'-5'A oligoadenylate synthetase activity, that could contribute to immune protection in sheep. The type and magnitude of these responses were dependent on ODN class and non-MHC-restricted killing was not associated with interferon-gamma production. The latter observation is in contrast with observations reported for mice and humans. These observations support the conclusion that differences in CpG-ODN-induced responses exist among species and that specific ODN sequences can significantly influence innate immune responses.

2',5'-Oligoadenylate Synthetase↗
PubMed2003

Bovine and ovine blood mononuclear leukocytes differ markedly in innate immune responses induced by Class A and Class B CpG-oligodeoxynucleotide.

Cytosine-phosphate-guanosine (CpG)-DNA can induce an impressive array of innate immune responses that may directly or indirectly contribute to the clearance of infectious agents. Assays, such as lymphocyte proliferative responses, have been used to demonstrate that the immunostimulatory activity of CpG-DNA is conserved among a broad range of vertebrate species, but no studies have been completed to determine if qualitative differences exist among species for CpG-oligodeoxynucleotide (ODN)-induced innate immune responses. In this study, we assessed the capacity of a Class A (ODN 2216) and a Class B (ODN 2007) CpG-ODN to induce innate immune responses in two closely related species, ovine (n = 28) and bovine (n = 29). The secretion of interferon (IFN)-alpha and IFN-gamma and non-major histocompatability complex (MHC)-restricted cytotoxic activity were assayed with CpG-ODN-stimulated peripheral blood mononuclear cells (PBMC). These investigations revealed significant interspecies and intraspecies variation in the responses. As expected, ODN 2216 was a potent inducer of IFN-alpha secretion by both bovine and ovine PBMC, but ODN 2007 also induced dose-dependent, CpG-specific IFN-alpha secretion by ovine PBMC. In contrast, a significant dose-dependent, CpG-specific IFN-gamma secretion response was only observed following ODN 2216 stimulation of bovine PBMC. Furthermore, both ODN 2216 and ODN 2007 induced CpG-specific non-MHC-restricted cytotoxicity with ovine but not bovine PBMC. Finally, there was not a single assay in which PBMC from all sheep or cattle responded at a detectable level. A striking aspect of these results is that such marked differences in CpG-ODN induced innate responses existed both between and within two closely related species.

Animals↗
PubMed2000

The in vivo effects of recombinant bovine herpesvirus-1 expressing bovine interferon-gamma.

To study the biological relevance of using bovine herpesvirus-1 (BHV-1) as a vector for expressing cytokines, a BHV-1 virus that expressed bovine interferon-gamma (IFN-gamma) was constructed. This recombinant virus (BHV-1/IFNgamma) was then used to infect the natural host in a respiratory disease model. In vitro characterization of the recombinant interferon-gamma confirmed that the cytokine expressed in BHV-1-infected cells was biologically active. The in vivo effects of the recombinant IFN-gamma were then analysed during a primary infection and after reactivation of a latent infection. During the primary infection, similar body temperature, clinical responses and virus shedding were observed for calves infected with either recombinant BHV-1/IFNgamma or parental gC(-)/LacZ(+) virus. An analysis of cellular and humoral responses did not reveal any significant immunomodulation by BHV-1/IFNgamma during the primary infection. The stability and activity of recombinant IFN-gamma was also analysed following the establishment of a latent infection. The presence of recombinant IFN-gamma did not significantly alter virus shedding following reactivation. The isolation of reactivated BHV-1/IFNgamma virus confirmed that a functional IFN-gamma gene was retained during latency. Thus, herpesviruses may provide virus vectors that retain functional genes during latency and recrudescence.

Animals↗