The HPV-16 E7 oncogene sensitizes malignant cells to IFN-alpha-induced apoptosis.

Interferons (IFNs) exert antitumor effects in several human malignancies, but their mechanism of action is unclear. There is a great variability in sensitivity to IFN treatment depending on both tumor type and the individual patient. The reason for this variable sensitivity is not known. The fact that several IFN-induced anticellular effects are exerted through modulation of proto-oncogenes and tumor suppressor genes may indicate that the malignant genotype may be decisive in the cell's sensitivity to IFN. To determine if a deregulated oncogene could alter the cellular response to IFN, a mouse lymphoma cell line (J3D) was stably transfected with the viral human papillomavirus-16 (HPV-16) E7 oncogene. The E7-transfected cells and their respective mock-transfected sister clones were treated with IFN-alpha and examined for possible IFN-induced anticellular effects. We found that the E7-transfected clones were greatly sensitized to IFN-alpha-induced apoptosis compared with their mock-transfected counterparts. Induction of apoptosis in the transfected cells correlated with the ability of IFN to activate parts of the proapoptotic machinery specifically in these cells, including activation of caspases and the proapoptotic protein Bak. In summary, our data suggest that transfection of malignant cells with the E7 oncogene can sensitize them to IFN-alpha-induced apoptosis. This demonstrates that an oncogenic event may alter the cellular sensitivity to IFN and might also have implications for treatment of HPV-related diseases with IFN.     

Interferons induce an antiviral state in human pancreatic islet cells

Enterovirus infections, in particular those with Coxsackieviruses, have been linked to the development of type 1 diabetes (T1D). Although animal models have demonstrated that interferons (IFNs) regulate virus-induced T1D by acting directly on the beta cell, little is known on the human pancreatic islet response to IFNs. Here we show that human islet cells respond to IFNs by expressing signature genes of antiviral defense. We also demonstrate that they express three intracellular sensors for viral RNA, the toll like receptor 3 (TLR3) gene, the retinoic acid-inducible gene I (RIG-I) and the melanoma differentiation-associated gene-5 (MDA-5), which induce type I IFN production in infected cells. Finally, we show for the first time that the IFN-induced antiviral state provides human islets with a powerful protection from the replication of Coxsackievirus. This may be critical for beta cell survival and protection from virus-induced T1D in humans.     

Type I interferons in host defense

Type I interferons (IFNs) are a family of cytokines specialized to coordinate immunity to viruses and other intracellular infections. In the past several years, many of the receptors and signaling pathways that link pathogen detection to induction of type I IFNs have been identified and characterized. An integrated picture has emerged in which type I IFNs have essential functions in several seemingly disparate processes: they restrict viral spread by engaging machinery that ultimately cripples and kills infected cells, yet they are also positively linked to the activation and expansion of lymphocytes that are important for control of intracellular infections. These advances highlight the context-specific actions of type I IFNs and clarify the multiple points at which they are integrated into both innate and adaptive immunity.     

Differential effects of type I and II interferons on myeloid cells and resistance to intracellular bacterial infections

The type I and II interferons (IFNs) play important roles in regulating immune responses during viral and bacterial infections and in the context of autoimmune and neoplastic diseases. These two IFN types bind to distinct cell surface receptors that are expressed by nearly all cells to trigger signal transduction events and elicit diverse cellular responses. In some cases, type I and II IFNs trigger similar cellular responses, while in other cases, the IFNs have unique or antagonistic effects on host cells. Negative regulators of IFN signaling also modulate cellular responses to the IFNs and play important roles in maintaining immunological homeostasis. In this review, we provide an overview of how IFNs stimulate cellular responses. We discuss the disparate effects of type I and II IFNs on host resistance to certain intracellular bacterial infections and provide an overview of models that have been proposed to account for these disparate effects. Mechanisms of antagonistic cross talk between type I and II IFNs are also introduced.     

Small ISGs coming forward.

Interferons (IFNs) were first characterized as antiviral proteins. Since then, IFNs have proved to be involved in malignant, angiogenic, inflammatory, immune, and fibrous diseases and, thus, possess a broad spectrum of pathophysiologic properties. IFNs activate a cascade of intracellular signaling pathways leading to upregulation of more than 1000 IFN-stimulated genes (ISGs) within the cell. The function of some of the IFN-induced proteins is well described, whereas that of many others remain poorly characterized. This review focuses on three families of small intracellular and intrinsically nonsecreted proteins (10-20 kDa) separated into groups according to their amino acid sequence similarity: the ISG12 group (6-16, ISG12, and ISG12-S), the 1-8 group (9-27/Leu13, 1-8U, and 1-8D), and the ISG15 group (ISG15/UCRP). These IFN-induced genes are abundantly and widely expressed and mainly induced by type I IFN. ISG15 is very well described and is a member of the ubiquitin-like group of proteins. 9-27/Leu-13 associates with CD81/TAPA-1 and plays a role in B cell development. The functions of 1-8U, 1-8D, 6-16, ISG12, and ISG12-S proteins are unknown at present.     

The phenomenology and treatment of interferon-induced depression

Interferon (IFN)-alpha, IFN-beta, and IFN-gamma are currently available for the treatment of malignancies, viral infections (e.g., hepatitis C virus), multiple sclerosis (MS), and skin conditions. In addition to their therapeutic effects, IFNs commonly cause various side effects. Most common among the side effects of IFN are "flu-like" symptoms such as chills, fever, and muscle soreness. However, IFN can also cause significant neuropsychiatric side effects, particularly symptoms of depression. A literature search was conducted in order to summarize current information on (1) the frequency, characteristics, and risk factors of IFN-induced depression, (2) possible biochemical mechanisms associated with IFN-induced depression, and (3) the treatment strategies for IFN-induced depression. Review of the literature suggests that symptoms of depression induced by IFN therapy, in particular IFN-alpha therapy, are common and can limit the treatment utility, often necessitating discontinuation of IFN therapy or the use of psychopharmacologic agents. Depression is also a suspected side effect of therapy with IFN-beta and IFN-gamma; however, the association has not been as convincingly confirmed. Importantly, IFNs affect neurochemical pathways putatively involved in the etiology of depression. While these depressive side effects usually resolve after the completion of IFN therapy, they can persist or reappear with dose escalations. It is recommended that health care providers, patients and their families be informed about the potential risk of the psychiatric disturbances that can occur with IFN-alpha therapy. Screening and monitoring, ideally using symptom rating scales for depression, and early antidepressant treatment intervention appear necessary to optimize IFN therapy for the majority of patients.     

Vaccinia virus recombinants as a model system to analyze interferon-induced pathways.

The interferons (IFNs) are a family of cytokines with broad antiviral activities that also control cell proliferation and modulate immune responses. IFNs exert their pleiotropic actions through the regulation of multiple pathways that have been subjected to extensive study using diverse approaches. The scope of this review is to show how we can take advantage of vaccinia virus (VV) to study IFN-related pathways. We summarize and present the different VV models available for studying IFN function and the possibilities that they offer to analyze IFN-induced pathways, IFN modulators, and the biologic effects at the molecular and cellular levels. Emphasis is given to studies of dsRNA-activated signaling with VV lacking E3L (VV DeltaE3L) and in RNA-activated protein kinase (PKR)-related pathways, through the use of VV recombinants (VVr) with inducible PKR (VV PKR). The latest system is versatile, as expression of PKR can be regulated and induced at different times; similarly, VVr can be generated expressing other PKR modulators. As an example of the utility of VVr, we describe how this model has been used to analyze the antiviral and proapoptotic functions of PKR, the impact of PKR on translation, and the PKR-induced activation of the nuclear factor-kappaB (NF-kappaB) pathway.     

Blocking monoclonal antibodies specific for mouse IFN-alpha/beta receptor subunit 1 (IFNAR-1) from mice immunized by in vivo hydrodynamic transfection.

Herein we report the generation of mouse monoclonal antibodies (mAbs) specific for the IFNAR-1 subunit of the mouse interferon-alpha/beta (IFN-alpha/beta) receptor (MAR1 mAbs) that block type I IFN receptor signaling and biologic response induction in vitro and in vivo. These mAbs were generated from Ifnar1 (/) mice immunized by in vivo hydrodynamic transfection with a plasmid encoding the extracellular domain (ECD) of murine IFNAR-1. All MAR1 mAbs bound native receptor expressed on cell surfaces and immunoprecipitated IFNAR-1 from solubilized cells, and two mAbs also detected IFNAR-1 by Western blot analysis. in vitro, the mAbs prevented ligand-induced intracellular signaling and induction of a variety of type I IFN-induced biologic responses but had no effect on IFN-gamma-induced responses. The most effective in vitro blocker, MAR1-5A3, also blocked type I IFN-induced antiviral, antimicrobial, and antitumor responses in vivo. We also explored whether murine IFNAR-1 surface expression required the presence of Tyk2. In contrast to Tyk2-deficient human cell lines, comparable IFNAR-1 expression was found on primary cells derived either from wild-type or Tyk2 (/) mice. These mAbs represent much needed tools to more clearly elucidate the biochemistry, cell biology, and physiologic function of the type I IFNs and their receptor in mediating host-protective immunity and immunopathology.     

IFN-λs

For decades, type I IFNs have been considered indispensable and unique antiviral mediators for the activation of rapid innate antiviral protection. However, the recent discovery of type III IFNs is challenging this paradigm. Since their identification in 2002/2003 by two independent groups, type III IFNs or IFN-λs, also known as IL-28/29, have been the subject of increased study with consequent recognition of their importance in virology and immunology. Initial reports suggested that IFN-λs functionally resemble type I IFNs. Although IFN-λs and classical type I IFNs (IFN-α/β) utilize distinct receptor complexes for signaling, both types of IFNs activate similar intracellular signaling pathways and biological activities, including the ability to induce antiviral state in cells, and both type I and type III IFNs are induced by viral infection. However, different antiviral potency, pattern of their induction and differential tissue expression of their corresponding receptor subunits suggest that the type I and type III IFN antiviral systems do not merely duplicate each other. Recent studies have started to reveal unique biological activities of IFN-λs in and beyond innate antiviral immunity.     

The effect of types I and III interferons on adrenocortical cells and its possible implications for autoimmune Addison's disease

Autoimmune Addison's disease (AAD) is caused by selective destruction of the hormone‐producing cells of the adrenal cortex. As yet, little is known about the potential role played by environmental factors in this process. Type I and/or type III interferons (IFNs) are signature responses to virus infections, and have also been implicated in the pathogenesis of autoimmune endocrine disorders such as type 1 diabetes and autoimmune thyroiditis. Transient development of AAD and exacerbation of established or subclinical disease, as well as the induction of autoantibodies associated with AAD, have been reported following therapeutic administration of type I IFNs. We therefore hypothesize that exposure to such IFNs could render the adrenal cortex susceptible to autoimmune attack in genetically predisposed individuals. In this study, we investigated possible immunopathological effects of type I and type III IFNs on adrenocortical cells in relation to AAD. Both types I and III IFNs exerted significant cytotoxicity on NCI‐H295R adrenocortical carcinoma cells and potentiated IFN‐γ‐ and polyinosine‐polycytidylic acid [poly (I : C)]‐induced chemokine secretion. Furthermore, we observed increased expression of human leucocyte antigen (HLA) class I molecules and up‐regulation of 21‐hydroxylase, the primary antigenic target in AAD. We propose that these combined effects could serve to initiate or aggravate an ongoing autoimmune response against the adrenal cortex in AAD.     

IFN-gamma induces apoptosis in HL-60 cells through decreased Bcl-2 and increased Bak expression.

Interferons (IFNs) are pleiotropic cytokines responsible for inducing innate and adaptive immunities against a wide range of viruses and other microbial pathogens. In addition, IFNs also exert antitumor activities due to their antiproliferative, immunomodulatory, proapoptotic functions. In the last decades, the successful clinical application of IFNs for treatment of cancer, particularly leukemia, has improved the quality and longevity of life for many patients. The induction of tumor cell apoptosis by IFNs is believed to contribute, at least in part, to the beneficial effects. IFN subtypes, such as IFN-alpha, IFN-beta, and IFN-gamma, induce apoptosis through cell type-specific signaling pathways, and several putative IFN-stimulated genes (ISGs) with proapoptotic functions have been identified. Here, we analyzed the ability of IFN-alpha, IFN-beta, or IFN-gamma to induce apoptosis in several malignant hematologic cell lines. We found that treatment with IFN-gamma, but not IFN-alpha, or IFN-beta, specifically induces HL-60 leukemia cells to undergo apoptosis. Roughly 30% of HL-60 cells treated for 48 h with IFN-gamma, but not IFN-gamma, or IFN-beta, underwent apoptosis as monitored by annexin V labeling to determine changes in phosphatidylserine (PS) asymmetry and TUNEL assay to detect DNA fragmentation. Consistent with these results, treatment with IFN-gamma, but not IFN-alpha or IFN-beta, induced the release of cytochrome c, activation of caspase-3, and cleavage of poly (ADP-ribose) polymerase (PARP), a well-characterized caspase-3 substrate. Further investigation into the potential mechanism responsible for mitochondrial disruption revealed that treatment with IFN-gamma caused decreased levels of Bcl-2 and increased levels of Bak. This study thus provides the basis for additional research to uncover the molecular mechanism by which IFN-gamma regulates the expression of Bcl-2 family members in various cell types.     

Herpes simplex virus-1 infection causes the secretion of a type I interferon-antagonizing protein and inhibits signaling at or before Jak-1 activation

Host cells respond to viral infection by the production of type I interferons (IFNs), which induce the expression of antiviral genes. Herpes simplex virus I (HSV-1) encodes many mechanisms that inhibit the type I IFN response, including the ICP27-dependent inhibition of type I IFN signaling. Here we show inhibition of Stat-1 nuclear accumulation in cells that express ICP27. ICP27 expression also induces the secretion of a small, heat-stable type I IFN antagonizing protein that inhibits Stat-1 nuclear accumulation. We show that the inhibition of IFN-induced Stat-1 phosphorylation occurs at or upstream of Jak-1 phosphorylation. Finally, we show that ISG15 expression is induced after IFNα treatment in mock-infected cells, but not cells infected with WT HSV-1 or ICP27⁻ HSV-1. These data suggest that HSV-1 has evolved multiple mechanisms to inhibit IFN signaling not only in infected cells, but also in neighboring cells, thereby allowing for increased viral replication and spread.     

Partial rescue of B cells in microphthalmic osteopetrotic marrow by loss of response to type I IFNs

The microphthalmic (mi) mouse exhibits deficiencies in the development of osteoclasts, melanocytes, mast cells and marrow B cells. Previously, we demonstrated that the marrow of such mice over-express receptor activator of nuclear factor kappaB (RANK) ligand (RANKL). RANKL has been shown to induce the production of IFN-beta, a type I IFN. Additionally, maturing B cells have been shown to undergo apoptosis in response to type I IFNs including IFN-beta during differentiation. We hypothesized that the loss of B cells in the marrow of mi mice was due to the over-expression of IFN-beta as a result of heightened RANK-RANKL signaling. Creating a mouse with the mi genotype that was non-responsive to IFN-beta (lacking the type I IFNR) allowed us to test this hypothesis. These mice demonstrated an elevated number of marrow B cells and marrow precursor cells compared with mi animals possessing the type I IFNR. Intriguingly, type I IFNR-deficient wild-type animals also demonstrated an increased number of precursor cells in the marrow, but not an expansion of B220-positive pre-B cells, compared with wild type, suggesting that modulation of type I IFN responses directly controls the development of marrow constituents.     

The pathogenesis of cutaneous lupus erythematosus: The aberrant distribution and function of different cell types in skin lesions

Cutaneous lupus erythematosus (CLE) is an autoimmune disease with a broad range of cutaneous manifestations. In skin lesions of CLE, keratinocytes primarily undergo apoptosis. Interferon‐κ(IFN‐κ) is belonged to type I interferons (type I IFNs) and is selectively produced by keratinocytes. Recently, keratinocytes selectively produced IFN‐κ is identified to be a key to trigger type I interferon responses in CLE. Other immune cells such as plasmacytoid dendritic cells (pDCs) are identified to be relevant origin of type I interferons (type I IFNs) which are central to the development of CLE lesions and responsible for mediating Th1 cell activity. Other types of cells such as neutrophils, B cells and Th17 cells also are involved in the development of this disease. The close interaction of those cells composes a comprehensive and complicated network in CLE. In this review, we discussed the aberrant distribution and function of different cells types involved in this disease and will offer a new direction for research and therapy in the near future.     

Enterovirus 71 blocks selectively type I interferon production through the 3C viral protein in mice

Type I interferons (IFNs) represent an essential innate defense mechanism for controlling enterovirus 71 (EV 71) infection. Mice inoculated with EV 71 produced a significantly lower amount of type I IFNs than those inoculated with poly (I:C), adenovirus type V, or coxsackievirus B3 (CB3). EV 71 infection, however, mounted a proinflammatory response with a significant increase in the levels of serum and brain interleukin (IL)‐6, monocyte chemoattractant protein‐1, tumor necrosis factor, and IFN‐γ. EV 71 infection abolished both poly (I:C)‐ and CB3‐induced type I IFN production of mice. Such effect was not extended to other enteroviruses including coxsackievirus A24, B2, B3, and echovirus 9, as mice infected with these viruses retained type I IFN responsiveness upon poly (I:C) challenge. In addition, EV 71‐infected RAW264.7 cells produced significantly lower amount of type I IFNs than non‐infected cells upon poly (I:C) stimulation. The inhibitory effect of EV 71 on type I IFN production was attributed to the viral protein 3C, which was confirmed using over‐expression systems in both mice and RAW264.7 cells. The 3C over‐expression, however, did not interfere with poly (I:C)‐induced proinflammatory cytokine production. These findings indicate that EV 71 can hamper the host innate defense by blocking selectively type I IFN synthesis through the 3C viral protein. J. Med. Virol. 84:1779–1789, 2012. © 2012 Wiley Periodicals, Inc.