Herpes virus induced proteasome-dependent degradation of the nuclear bodies-associated PML and Sp100 proteins.
The PML protein is associated to nuclear bodies (NBs) whose functions are as yet unknown. PML and two other NBs-associated proteins, Sp100 And ISG20 are directly induced by interferons (IFN). PML and Sp100 proteins are covalently linked to SUMO-1, and ubiquitin-like peptide. PML NBs are disorganized in acute promyelocytic leukemia and during several DNA virus infections. In particular, the HSV-1 ICP0 protein is known to delocalize PML from NBs. Thus, NBs could play an important role in oncogenesis, IFN response and viral infections. Here, we show that HSV-1 induced PML protein degradation without altering its mRNA level. This degradation was time- and multiplicity of infection-dependent. Sp100 protein was also degraded, while another SUMO-1 conjugated protein, RanGAP1 and the IFN-induced protein kinase PKR were not. The proteasome inhibitor MG132 abrogated the HSV-1-induced PML and Sp100 degradation and partially restored their NB-localization. HSV-1 induced PML and Sp100 degradation constitutes a new example of viral inactivation of IFN target gene products. (+info)
Characterization of transgenic mice with targeted disruption of the catalytic domain of the double-stranded RNA-dependent protein kinase, PKR.
The interferon-inducible, double-stranded RNA-dependent protein kinase PKR has been implicated in anti-viral, anti-tumor, and apoptotic responses. Others have attempted to examine the requirement of PKR in these roles by targeted disruption at the amino terminal-encoding region of the Pkr gene. By using a strategy that aims at disruption of the catalytic domain of PKR, we have generated mice that are genetically ablated for functional PKR. Similar to the other mouse model of Pkr disruption, we have observed no consequences of loss of PKR on tumor suppression. Anti-viral response to influenza and vaccinia also appeared to be normal in mice and in cells lacking PKR. Cytokine signaling in the type I interferon pathway is normal but may be compromised in the erythropoietin pathway in erythroid bone marrow precursors. Contrary to the amino-terminal targeted Pkr mouse, tumor necrosis factor alpha-induced apoptosis and the anti-viral apoptosis response to influenza is not impaired in catalytic domain-targeted Pkr-null cells. The observation of intact eukaryotic initiation factor-2alpha phosphorylation in these Pkr-null cells provides proof of rescue by another eukaryotic initiation factor-2alpha kinase(s). (+info)
Hydrophobic interaction of human, mouse, and rabbit interferons with immobilized hydrocarbons.
Interferons of human, mouse, and rabbit origin bind to straight chain hydrocarbons immobilized on agarose. The hydrophobic nature of binding is established by the following observations: (a) a positive correlation between the length of hydrocarbon ligand and the strength of interaction; (b) a stronger interaction with hydrocarbon ligands terminated with apolar rather than polar head groups; (c) a lack of dependence of binding on ionic strength and pH of the solvent; (d) a reversal of binding by ethylene glycol, a hydrophobic solute; (e) an increasing eluting efficacy of tetraalkylammonium ions with the length of their alkyl substituents. The hydrophobic interactions of human interferon underlie the efficiency of two-step chromatographic procedures. For example, human embryo kidney interferon can be purified about 3,600-fold by sequential chromatography on (a) concanavalin A-agarose, (b) octyl-agarose. Another two-step procedure: (a) concanavalin A-agarose, (b) L-tryptophan-agarose, gives about 10,000-fold purification. The overall recovery of interferon in both cases in close to 90%. (+info)
Herpetic keratitis. Proctor Lecture.
Although much needs to be learned about the serious clinical problem of herpes infection of the cornea, we have come a long way. We now have effective topical antiviral drugs. We have animal models which, with a high degree of reliability, clearly predict the effect to be expected clinically in man, as well as the toxicity. We have systemically active drugs and the potential of getting highly active, potent, completely selective drugs, with the possibility that perhaps the source of viral reinfection can be eradicated. The biology of recurrent herpes and stromal disease is gradually being understood, and this understanding may result in new and better therapy of this devastating clinical disease. (+info)
From myocarditis to cardiomyopathy: mechanisms of inflammation and cell death: learning from the past for the future.
A progression from viral myocarditis to dilated cardiomyopathy has long been hypothesized, but the actual extent of this progression has been uncertain. However, a causal link between viral myocarditis and dilated cardiomyopathy has become more evident than before with the tremendous developments in the molecular analyses of autopsy and endomyocardial biopsy specimens, new techniques of viral gene amplification, and modern immunology. The persistence of viral RNA in the myocardium beyond 90 days after inoculation, confirmed by the method of polymerase chain reaction, has given us new insights into the pathogenesis of dilated cardiomyopathy. Moreover, new knowledge of T-cell-mediated immune responses in murine viral myocarditis has contributed a great deal to the understanding of the mechanisms of ongoing disease processes. Apoptotic cell death may provide the third concept to explain the pathogenesis of dilated cardiomyopathy, in addition to persistent viral RNA in the heart tissue and an immune system-mediated mechanism. Beneficial effects of alpha1-adrenergic blocking agents, carteolol, verapamil, and ACE inhibitors have been shown clinically and experimentally in the treatment of viral myocarditis and dilated cardiomyopathy. Antiviral agents should be more extensively investigated for clinical use. The rather discouraging results obtained to date with immunosuppressive agents in the treatment of viral myocarditis indicated the importance of sparing neutralizing antibody production, which may be controlled by B cells, and raised the possibility of promising developments in immunomodulating therapy. (+info)
Interferon-induced human MxA GTPase blocks nuclear import of Thogoto virus nucleocapsids.
Interferon-induced human MxA protein belongs to the dynamin superfamily of large GTPases. It exhibits antiviral activity against a variety of RNA viruses, including Thogoto virus, an influenza virus-like orthomyxovirus transmitted by ticks. Here, we report that MxA blocks the transport of Thogoto virus nucleocapsids into the nucleus, thereby preventing transcription of the viral genome. This interaction can be abolished by a mAb that neutralizes the antiviral activity of MxA. Our results reveal an antiviral mechanism whereby an interferon-induced protein traps the incoming virus and interferes with proper transport of the viral genome to its ultimate target compartment within the infected cell. (+info)
Advances in the biological therapy and gene therapy of malignant disease.
Biological and gene therapy of cancer have become important components of clinical cancer research. Advances in this area are based on evidence for the presence of tumor antigens, antitumor immune responses, evasion of host control by tumors, and the recognition of host defense failure in cancer patients. These mechanisms are being corrected or exploited in the development of biological and gene therapy. Over the last decade, 9 biological therapies have received Food and Drug Administration approval, and another 12 appear promising and will likely be approved in the next few years. Our approach to gene therapy has been to allogenize tumors by the direct intratumoral injection of HLA-B7/beta2-microglobulin genes as plasmid DNA in a cationic lipid into patients with malignant melanoma. In four Phase I studies, we found a 36% response by the local injected tumor and a 19% systemic antitumor response. In other cancers, gene transfer, expression, and an intratumoral T-cell response were seen, but no clinical response was seen. A variety of follow-up studies with HLA-B7 and other genes are planned. Evasion of host control is now a major target of gene therapy. Strategies to overcome this include up-regulation of MHC and introduction of cell adhesion molecules into tumor cells, suppression of transforming growth factor and interleukin 10 production by tumor cells, and blockade of the fas ligand-fas interaction between tumor cells and attacking lymphocytes. With these approaches, it seems likely that gene therapy may become the fifth major modality of cancer treatment in the next decade. (+info)
Can we cure indolent lymphomas?
The current consensus is that indolent lymphomas are incurable disorders. There are some indications that these malignancies are potentially curable. Indeed, not all indolent lymphomas are currently incurable. For example, patients with Ann Arbor stage I-II indolent lymphomas can experience long-term disease-free survival and probable cure. Also, from the available literature data, it seems that the achievement of a molecular complete remission is a desirable objective. Patients who achieve a persistently negative PCR state seldom relapse, whereas the opposite is true for persistently positive cases. In view of its excellent correlation with disease-free survival when examined serially in multiple blood or marrow samples, the PCR technique has the potential of providing a tumor marker that can be used as an early end point for clinical trials. By serving as an early surrogate end point, PCR could play an important role in expediting the development of new treatment strategies. Whether IFN is capable of increasing the molecular complete remission rate as measured by PCR is not known. However, it is clear that from the clinical standpoint, IFN has been able to increase 2-fold the length of remission in patients with advanced indolent lymphomas. In at least two studies, this has been associated with prolongation of survival. More intensive regimens such as alternating triple therapy, when used in combination with IFN, seem to have improved the quality of remissions as judged by the PCR assay. Finally, the site where the bcl-2 breakpoint occurs seems to have clinical significance. Those follicular lymphomas with germ-line bcl-2, in our experience, have behaved more aggressively than the others, and their failure-free survival seems different from the usual indolent lymphomas and more closely resembles the large cell lymphomas. Although the biological significance of this observation is not yet understood, this group might actually constitute a prognostically different subset with a more aggressive and perhaps more curable lymphoma. Whether the plateau observed in their failure-free survival curve will be maintained with more follow-up and whether they might be a curable subset remain to be determined. (+info)