Type 1 interferon as an antiinflammatory agent: inhibition of lipopolysaccharide-induced interleukin-1 beta and induction of interleukin-1 receptor antagonist

DNA methyltransferase inhibition promotes recruitment of myeloid-derived suppressor cells to the tumor microenvironment through induction of tumor cell-intrinsic interleukin-1

DNA methyltransferase (DNMT) inhibitors are used for treatment of certain hematological malignancies and exert anti-cancer activity through diverse mechanisms, including reexpression of tumor suppressor genes and anti-viral responses triggered by expression of endogenous retroviruses. Despite advances in the pharmacokinetic properties of DNMT inhibitors, the efficacy of these drugs in solid cancers remains low. Here, we show in cell lines and clinical and experimental tumors across multiple cancer types that DNMT inhibition induces the expression of interleukin-1 (IL-1), a cytokine with proinflammatory and protumorigenic properties. Specifically, this tumor-intrinsic IL-1 expression modulates the chemokine landscape of tumors and leads to the recruitment of monocytic myeloid-derived suppressor cells to the tumor microenvironment, processes that can be blocked by IL-1 antagonists. Molecular analysis demonstrates complex patterns of IL-1 and interferon activation and crosstalk in response to DNMT inhibition, which depend on the integrity of IRF- and NF-κB-mediated antiviral pathways and may determine the outcome of DNMT-inhibitor treatment. Together, our results show that DNMT inhibitors may negatively affect the microenvironment of a large subset of tumors and suggest that co-treatment with IL-1 antagonists may be a favorable combination for these patients.

Recombinant Interferon-β in the Treatment of Polycythemia Vera and Related Neoplasms: Rationales and Perspectives

About 30 years ago, the first clinical trials of the safety and efficacy of recombinant interferon-α2 (rIFN-α2) were performed. Since then, several single-arm studies have shown rIFN-α2 to be a highly potent anticancer agent against several cancer types. Unfortunately, however, a high toxicity profile in early studies with rIFN-α2 -among other reasons likely due to the high dosages being used-disqualified rIFN-α2, which was accordingly replaced with competitive drugs that might at first glance look more attractive to clinicians. Later, pegylated IFN-α2a (Pegasys) and pegylated IFN-α2b (PegIntron) were introduced, which have since been reported to be better tolerated due to reduced toxicity. Today, treatment with rIFN-α2 is virtually outdated in non-hematological cancers, where other immunotherapies-e.g., immune-checkpoint inhibitors-are routinely used in several cancer types and are being intensively investigated in others, either as monotherapy or in combination with immunomodulatory agents, although only rarely in combination with rIFN-α2. Within the hematological malignancies, rIFN-α2 has been used off-label for decades in patients with Philadelphia-negative chronic myeloproliferative neoplasms (MPNs)-i.e., essential thrombocythemia, polycythemia vera, and myelofibrosis-and in recent years rIFN-α2 has been revived with the marketing of ropeginterferon-α2b (Besremi) for the treatment of polycythemia vera patients. Additionally, rIFN-α2 has been revived for the treatment of chronic myelogenous leukemia in combination with tyrosine kinase inhibitors. Another rIFN formulation-recombinant interferon-β (rIFN-β)-has been used for decades in the treatment of multiple sclerosis but has never been studied as a potential agent to be used in patients with MPNs, although several studies and reviews have repeatedly described rIFN-β as an effective anticancer agent as well. In this paper, we describe the rationales and perspectives for launching studies on the safety and efficacy of rIFN-β in patients with MPNs.

Lyl1-deficiency promotes inflammatory responses and increases mycobacterial burden in response to Mycobacterium tuberculosis infection in mice

Lymphoblastic leukemia 1 (Lyl1) is a well-studied transcription factor known to exhibit oncogenic potential in various forms of leukemia with pivotal roles in hematopoietic stem cell biology. While its role in early hematopoiesis is well established, its function in mature innate cells is less explored. Here, we identified Lyl1 as a drastically perturbed gene in the Mycobacterium tuberculosis (Mtb) infected mouse macrophage transcriptome. We report that Lyl1 downregulation upon immune stimulation is a host-driven process regulated by NFκB and MAP kinase pathways. Interestingly, Lyl1-deficient macrophages have decreased bacterial killing potential with reduced nitric oxide (NO) levels while expressing increased levels of pro-inflammatory interleukin-1 and CXCL1. Lyl1-deficient mice show reduced survival to Mtb HN878 infection with increased bacterial burden and exacerbated inflammatory responses in chronic stages. We observed that increased susceptibility to infection was accompanied by increased neutrophil recruitment and IL-1, CXCL1, and CXCL5 levels in the lung homogenates. Collectively, these results suggest that Lyl1 controls Mtb growth, reduces neutrophilic inflammation and reveals an underappreciated role for Lyl1 in innate immune responses.

MDA5 signaling induces type 1 IFN- and IL-1-dependent lung vascular permeability which protects mice from opportunistic fungal infection

Lungs balance threat from primary viral infection, secondary infection, and inflammatory damage. Severe pulmonary inflammation induces vascular permeability, edema, and organ dysfunction. We previously demonstrated that poly(I:C) (pICLC) induced type 1 interferon (t1IFN) protected mice from Cryptococcus gattii (Cg) via local iron restriction. Here we show pICLC increased serum protein and intravenously injected FITC-dextran in the lung airspace suggesting pICLC induces vascular permeability. Interestingly, pICLC induced a pro-inflammatory signature with significant expression of IL-1 and IL-6 which depended on MDA5 and t1IFN. Vascular permeability depended on MDA5, t1IFN, IL-1, and IL-6. T1IFN also induced MDA5 and other MDA5 signaling components suggesting that positive feedback contributes to t1IFN dependent expression of the pro-inflammatory signature. Vascular permeability, induced by pICLC or another compound, inhibited Cg by limiting iron. These data suggest that pICLC induces t1IFN which potentiates pICLC-MDA5 signaling increasing IL-1 and IL-6 resulting in leakage of antimicrobial serum factors into lung airspace. Thus, induced vascular permeability may act as an innate defense mechanism against opportunistic fungal infection, such as cryptococcosis, and may be exploited as a host-directed therapeutic target.

Anti-Inflammatory Agents: An Approach to Prevent Cognitive Decline in Alzheimer's Disease

Systemic inflammation is an organism's response to an assault by the non-self. However, that inflammation may predispose humans to illnesses targeted to organs, including Alzheimer's disease (AD). Lesions in AD have pro-inflammatory cytokines and activated microglial/monocyte/macrophage cells. Up to this point, clinical trials using anti-amyloid monoclonal antibodies have not shown success. Maybe it is time to look elsewhere by combating inflammation. Neuroinflammation with CNS cellular activation and excessive expression of immune cytokines is suspected as the "principal culprit" in the higher risk for sporadic AD. Microglia, the resident immune cell of the CNS, perivascular myeloid cells, and activated macrophages produce IL-1, IL-6 at higher levels in patients with AD. Anti-inflammatory measures that target cellular/cytokine-mediated damage provide a rational therapeutic strategy. We propose a clinical trial using oral type 1 IFNs to act as such an agent; one that decreases IL-1 and IL-6 secretion by activating lamina propria lymphocytes in the gut associated lymphoid tissue with subsequent migration to the brain undergoing inflammatory responses. A clinical trial would be double-blind, parallel 1-year clinical trial randomized 1 : 1 oral active type 1 IFN versus best medical therapy to determine whether ingested type I IFN would decrease the rate of cognitive decline in mild cognitive impairment or mild AD. Using cognitive psychometrics, imaging, and fluid biomarkers (MxA for effective type I IFN activity beyond the gut), we can determine if oral type I IFN can prevent cognitive decline in AD.

Inflammasome-induced extracellular vesicles harbour distinct RNA signatures and alter bystander macrophage responses

Infectious organisms and damage of cells can activate inflammasomes, which mediate tissue inflammation and adaptive immunity. These mechanisms evolved to curb the spread of microbes and to induce repair of the damaged tissue. Chronic activation of inflammasomes, however, contributes to non-resolving inflammatory responses that lead to immuno-pathologies. Inflammasome-activated cells undergo an inflammatory cell death associated with the release of potent pro-inflammatory cytokines and poorly characterized extracellular vesicles (EVs). Since inflammasome-induced EVs could signal inflammasome pathway activation in patients with chronic inflammation and modulate bystander cell activation, we performed a systems analysis of the ribonucleic acid (RNA) content and function of two EV classes. We show that EVs released from inflammasome-activated macrophages carry a specific RNA signature and contain interferon β (IFNβ). EV-associated IFNβ induces an interferon signature in bystander cells and results in dampening of NLRP3 inflammasome responses. EVs could, therefore, serve as biomarkers for inflammasome activation and act to prevent systemic hyper-inflammatory states by restricting NLRP3 activation in bystander cells.

Interferon lambda 4 can directly activate human CD19+ B cells and CD8+ T cells

Compared with the ubiquitous expression of type I (IFNα and IFNβ) interferon receptors, type III (IFNλ) interferon receptors are mainly expressed in epithelial cells of mucosal barriers of the of the intestine and respiratory tract. Consequently, IFNλs are important for innate pathogen defense in the lung and intestine. IFNλs also determine the outcome of hepatitis C virus (HCV) infections, with IFNλ4 inhibiting spontaneous clearance of HCV. Because viral clearance is dependent on T cells, we explored if IFNλs can directly bind to and regulate human T cells. We found that human B cells and CD8+ T cells express the IFNλ receptor and respond to IFNλs, including IFNλ4. IFNλs were not inhibitors but weak stimulators of B- and T-cell responses. Furthermore, IFNλ4 showed neither synergistic nor antagonistic effects in co-stimulatory experiments with IFNλ1 or IFNα. Multidimensional flow cytometry of cells from liver biopsies of hepatitis patients from IFNλ4-producers showed accumulation of activated CD8+ T cells with a central memory-like phenotype. In contrast, CD8+ T cells with a senescent/exhausted phenotype were more abundant in IFNλ4-non-producers. It remains to be elucidated how IFNλ4 promotes CD8 T-cell responses and inhibits the host immunity to HCV infections.

Dose-dependent structural and immunological changes in the placenta and fetal brain in response to systemic inflammation during pregnancy

PROBLEM

Systemic maternal inflammation is associated with adverse neonatal sequelae. We tested the hypothesis that IL-1β is a key inflammatory regulator of adverse pregnancy outcomes.

METHOD OF STUDY

Pregnant mice were treated with intraperitoneal injections of IL-1β (0, 0.1, 0.5, or 1 μg) from embryonic day (E)14 to E17. Placenta and fetal brains were harvested and analyzed for morphologic changes and IL-1β signaling markers.

RESULTS

As compared with non-treated dams, maternal injections with IL-1β resulted in increased p-NF-κB and caspase-1 in placentas and fetal brains, but not consistently in spleens, suggesting induction of intrinsic IL-1β production. These findings were confirmed by increased levels of IL-1β in the placentas of the IL-1β-treated dams. Systemic treatment of dams with IL-1β suppressed Stat1 signaling. Maternal inflammation caused by IL-1β treatment reduced fetal viability to 80.6% and 58.9%, in dams treated with either 0.5 or 1 μg of IL-1β, respectively. In the placentas, there was an IL-1β dose-dependent distortion of the labyrinth structure, decreased numbers of mononuclear trophoblast giant cells, and reduced proportions of endothelial cells as compared to placentas from control dams. In fetal brains collected at E17, there was an IL-1β dose-dependent reduction in cortical neuronal morphology.

CONCLUSION

This work demonstrates that systemic IL-1β injection causes dose-dependent structural and functional changes in the placenta and fetal brain.

Targeting Evolutionary Conserved Oxidative Stress and Immunometabolic Pathways for the Treatment of Respiratory Infectious Diseases

Significance: Up until recently, metabolism has scarcely been referenced in terms of immunology. However, emerging evidence has shown that immune cells undergo an adaptation of metabolic processes, known as the metabolic switch. This switch is key to the activation, and sustained inflammatory phenotype in immune cells, which includes the production of cytokines and reactive oxygen species (ROS) that underpin infectious diseases, respiratory and cardiovascular disease, neurodegenerative disease, as well as cancer. Recent Advances: There is a burgeoning body of evidence that immunometabolism and redox biology drive infectious diseases. For example, influenza A virus (IAV) utilizes endogenous ROS production via NADPH oxidase (NOX)2-containing NOXs and mitochondria to circumvent antiviral responses. These evolutionary conserved processes are promoted by glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle that drive inflammation. Such metabolic products involve succinate, which stimulates inflammation through ROS-dependent stabilization of hypoxia-inducible factor-1α, promoting interleukin-1β production by the inflammasome. In addition, itaconate has recently gained significant attention for its role as an anti-inflammatory and antioxidant metabolite of the TCA cycle. Critical Issues: The molecular mechanisms by which immunometabolism and ROS promote viral and bacterial pathology are largely unknown. This review will provide an overview of the current paradigms with an emphasis on the roles of immunometabolism and ROS in the context of IAV infection and secondary complications due to bacterial infection such as Streptococcus pneumoniae. Future Directions: Molecular targets based on metabolic cell processes and ROS generation may provide novel and effective therapeutic strategies for IAV and associated bacterial superinfections.

Production of potent long-lasting consensus interferon using albumin fusion technology in Pichia pastoris expression system

Consensus interferon (cIFN) is a wholly synthetic therapeutic protein which is used to treat hepatitis C/B and certain types of malignancies. It has short serum half-life, therefore, to maintain its therapeutic level in the human body it requires thrice-weekly administration. Various strategies like PEGylation and micro-encapsulation have been developed during the last few years to enhance the pharmacokinetics of small therapeutic peptides. This study executed the human albumin-fusion technology, a simple and flexible approach to extend the serum circulating half-life of cIFN, because human serum albumin (HSA) has long circulating half-life (19 days) and very minute immunological activities. We integrated the codon-optimized HSA-cIFN fusion gene into Pichia pastoris genome by homologous recombination. The selection of hyper-resistant P. pastoris clone against Zeocin™ achieved a high-level secretory expression (250 mg/L) of fusion protein. HSA-cIFN fusion protein was purified using one-step purification by affinity chromatography with 34% recovery. The SDS-PAGE and SEC-HPLC analysis confirmed the final purified product has molecular weight of 87 kDa with 98% purity. Western blot analysis using anti-IFN antibodies further verified the purified HSA-cIFN fusion protein. The specific biological activity was 2.1 × 10⁶ IU/mg as assessed by cytopathic inhibition assay, and half-life of fusion protein was estimated by in vitro thermal and proteolytic stability studies. This work concludes that by using albumin fusion technology, codon optimization and one-step purification a high yield of 86 mg/L of biologically active protein with improved serum half-life was obtained.

IFN-α-2b treatment protects against diet-induced obesity and alleviates non-alcoholic fatty liver disease in mice

IFN-α is used for inflammatory purposes, and obesity and NAFLD are strongly correlated with inflammatory processes. We wondered whether IFN-α-2b can attenuate obesity development and its associated NAFLD in mice fed high fat diet (HFD) for 10 weeks. IFN-α-2b had a robust effect on body weight loss associated with NAFLD amelioration by decreasing hepatic inflammation. IFN-α-2b-treated mice showed increased plasma cholesterol levels together with decreased hepatic cholesterol, both on chow and HF diets. Interestingly, mice on IFN-α-2b treatment secreted smaller VLDL particles highly enriched in cholesterol. Mechanistically, we found that IFN-α-2b antiobesity effects were related to increased fatty acid oxidation; and its effects on cholesterol metabolism were due to both a decrease in the master cholesterogenic transcription factor SREBP-2 and in the rate limiting enzyme in cholesterol synthesis, HMGCR. To our knowledge, this is the first report showing the effects of IFN-α-2b on the prevention of the development of HFD-induced body weight gain and dyslipidemia through a mechanism that involves fatty acid oxidation and cholesterol decrease. These studies comprise necessary steps for understanding the amelioration of obesity and NAFLD. Results shed some light into the mechanism of action of natural cytokines, and their effects on ameliorating obesity and its related diseases.

Conserved Gammaherpesvirus Protein Kinase Selectively Promotes Irrelevant B Cell Responses

Gammaherpesviruses are ubiquitous pathogens that are associated with B cell lymphomas. In the early stages of chronic infection, these viruses infect naive B cells and subsequently usurp the B cell differentiation process through the germinal center response to ensure latent infection of long-lived memory B cells. A unique feature of early gammaherpesvirus chronic infection is a robust differentiation of irrelevant, virus-nonspecific B cells with reactivities against self-antigens and antigens of other species. In contrast, protective, virus-specific humoral responses do not reach peak levels until a much later time. While several host factors are known to either promote or selectively restrict gammaherpesvirus-driven germinal center response, viral mechanisms that contribute to the irrelevant B cell response have not been defined. In this report we show that the expression and the enzymatic activity of the gammaherpesvirus-encoded conserved protein kinase selectively facilitates the irrelevant, but not virus-specific, B cell responses. Further, we show that lack of interleukin-1 (IL-1) receptor attenuates gammaherpesvirus-driven B cell differentiation and viral reactivation. Because germinal center B cells are thought to be the target of malignant transformation during gammaherpesvirus-driven lymphomagenesis, identification of host and viral factors that promote germinal center responses during gammaherpesvirus infection may offer an insight into the mechanism of gammaherpesvirus pathogenesis.IMPORTANCE Gammaherpesviruses are ubiquitous cancer-associated pathogens that usurp the B cell differentiation process to establish life-long latent infection in memory B cells. A unique feature of early gammaherpesvirus infection is the robust increase in differentiation of B cells that are not specific for viral antigens and instead encode antibodies that react with self-antigens and antigens of other species. Viral mechanisms that are involved in driving such irrelevant B cell differentiation are not known. Here, we show that gammaherpesvirus-encoded conserved protein kinase and host IL-1 signaling promote irrelevant B cell responses and gammaherpesvirus-driven germinal center responses, with the latter thought to be the target of viral transformation.

Long-term familial Mediterranean fever remission on successful hepatitis C virus treatment in a patient not responding to colchicine: a case report

Background

Familial Mediterranean fever is an autosomal recessive disorder characterized by periodic febrile attacks of aseptic serositis and/or arthritis. The main treatment is colchicine which prevents attacks in the majority of patients except for a group of colchicine-resistant cases. Chronic hepatitis C is a viral infection causing chronic inflammation of liver tissue (hepatitis) which ultimately progresses to fibrosis and liver cirrhosis with a high chance of hepatocellular carcinoma. However, we found no data in the literature concerning the impact of hepatitis C on the course of attacks of familial Mediterranean fever.

Case presentation

We report a case of a 21-year-old white woman with familial Mediterranean fever who had not been responding to a high dose of colchicine (2 mg/day). She presented to our clinic with a finding of chronic hepatitis C genotype 3 infection. After successful antiviral therapy with peginterferon and ribavirin, she became attack-free for 2 years and went on to a lower dose of colchicine.

Conclusions

This unusual case illustrates complete resolution of attacks of autoinflammatory disease after drug-induced clearance of chronic hepatitis C infection. Coexisting infections should be viewed as potentially altering the course of autoinflammatory disorders, and any attempt to cure the infections should be made in order to gain an added value of benefiting the chronic disease. This case highlights the interrelation of external pathogen-related and genetically inherited alterations in immunity and the importance of considering the whole spectrum of possible causative factors rather than implementing separate guidelines in order to achieve best quality of medical care in any given patient.

Gut-liver axis and sterile signals in the development of alcoholic liver disease

BACKGROUND

Innate immunity plays a critical role in the development of alcohol-induced liver inflammation. Understanding the inter-relationship of signals from within and outside of the liver that trigger liver inflammation is pivotal for development of novel therapeutic targets of alcoholic liver disease (ALD).

AIM

The aim of this paper is to review recent advances in the field of alcohol-induced liver inflammation.

METHODS

A detailed literature review was performed using the PubMed database published between January 1980 and December 2016.

RESULTS

We provide an update on the role of intestinal microbiome, metabolome and the gut-liver axis in ALD, discuss the growing body of evidence on the diversity of liver macrophages and their differential contribution to alcohol-induced liver inflammation, and highlight the crucial role of inflammasomes in integration of inflammatory signals in ALD. Studies to date have identified a multitude of new therapeutic targets, some of which are currently being tested in patients with severe alcoholic hepatitis. These treatments aim to strengthen the intestinal barrier, ameliorate liver inflammation and augment hepatocyte regeneration.

CONCLUSION

Given the complexity of inflammation in ALD, multiple pathobiological mechanisms may need to be targeted at the same time as it seems unlikely that there is a single dominant pathogenic pathway in ALD that would be easily targeted using a single target drug approach.

SHORT SUMMARY

Here, we focus on recent advances in immunopathogenesis of alcoholic liver disease (ALD), including gut-liver axis, hepatic macrophage activation, sterile inflammation and synergy between bacterial and sterile signals. We propose a multiple parallel hit model of inflammation in ALD and discuss its implications for clinical trials in alcoholic hepatitis.

Interleukin-1β as emerging therapeutic target in hematological malignancies and potentially in their complications

Interleukin-1β (IL-1β) is a pleiotropic cytokine that exerts multiple roles in both physiological and pathological conditions. It is produced by different cell subsets, and drives a wide range of inflammatory responses in numerous target cells. Enhanced IL-1β signaling is a common event in patients of hematological malignancies. Recent body of evidence obtained in preclinical models shows the pathogenic role of these alterations, and the promising therapeutic value of IL-1 targeting. In this review, we further highlight a potential contribution of IL-1β linking to complications and autoimmune disease that should be investigated in future studies. Hence, drugs that target IL-1 may be helpful to improve outcome or reduce morbidity in patients. Some of them are FDA-approved, and used efficiently against autoimmune diseases, like IL-1 receptor antagonist. In the clinic, however, this agent seems to have limited properties. Current improved drugs will allow to determine the true potential of IL-1 and IL-1β targeting as therapy in hematological malignancies and their related complications.

Clash of the Cytokine Titans: counter-regulation of interleukin-1 and type I interferon-mediated inflammatory responses

Over the past decades the notion of 'inflammation' has been extended beyond the original hallmarks of rubor (redness), calor (heat), tumor (swelling) and dolor (pain) described by Celsus. We have gained a more detailed understanding of the cellular players and molecular mediators of inflammation which is now being applied and extended to areas of biomedical research such as cancer, obesity, heart disease, metabolism, auto-inflammatory disorders, autoimmunity and infectious diseases. Innate cytokines are often central components of inflammatory responses. Here, we discuss how the type I interferon and interleukin-1 cytokine pathways represent distinct and specialized categories of inflammatory responses and how these key mediators of inflammation counter-regulate each other.

Suppression of endotoxin-inducible cytokines in whole blood from human subjects following single dose of recombinant human interleukin-11

To determine whether a single injection of recombinant human interleukin-11 (rhIL-11) to human subjects would affect endotoxin-inducible cytokine production, 6 dialysis-dependent patients with renal failure and 4 healthy volunteers were subcutaneously injected with rhIL-11 (50 µg/kg). The circulating concentrations of rhIL-11 remained at a constant level of approximately 12 ng/ml for 0.25—6 h in healthy volunteers but were 2-fold higher in dialysis-dependent patients. Venous blood obtained before and after rhIL-11 was stimulated with 10 ng/ml of LPS for 24 h at 37°C and production of TNFα, IL-1β, and IL-8 determined. The maximum suppression of IL-1β, TNFα and IL-8 production (66%, 24% and 58%, respectively) was observed 1 h after rhIL-11 administration. After 24 h, when circulating concentration of rhIL-11 had decreased to near pre-injection levels, LPS-induced TNFα and IL-1β production remained suppressed (56 ± 17%, P < 0.05; 46 ± 4.7, P<0.01, respectively) but returned to baseline at 48 h. These findings suggest that there is a therapeutic benefit of single doses of rhIL-11 in reducing LPS-induced IL-1β and TNFα production.

Viral sensing at the blood-brain barrier: new roles for innate immunity at the CNS vasculature

Neurotropic viral infections are a major source of disease worldwide and represent a growing burden to public health. While the central nervous system (CNS) is normally protected from viral infection by the blood-brain barrier (BBB), many viruses are able to cross the BBB and establish CNS infection through processes that largely remain poorly understood. A growing body of recent research has begun to shed light on the viral and host factors that modulate BBB function, contributing to both protective and pathological disease processes. Central to these studies have been the actions of host cytokines and chemokines, which have increasingly been shown to be key regulators of BBB physiology. This review summarizes recent advances in understanding how BBB function governs both viral pathogenesis and host immune responses during neurotropic viral infections.

Viral pathogen-associated molecular patterns regulate blood-brain barrier integrity via competing innate cytokine signals

Pattern recognition receptor (PRR) detection of pathogen-associated molecular patterns (PAMPs), such as viral RNA, drives innate immune responses against West Nile virus (WNV), an emerging neurotropic pathogen. Here we demonstrate that WNV PAMPs orchestrate endothelial responses to WNV via competing innate immune cytokine signals at the blood-brain barrier (BBB), a multicellular interface with highly specialized brain endothelial cells that normally prevents pathogen entry. While Th1 cytokines increase the permeability of endothelial barriers, type I interferon (IFN) promoted and stabilized BBB function. Induction of innate cytokines by pattern recognition pathways directly regulated BBB permeability and tight junction formation via balanced activation of the small GTPases Rac1 and RhoA, which in turn regulated the transendothelial trafficking of WNV. In vivo, mice with attenuated type I IFN signaling or IFN induction (Ifnar^−/−Irf7^−/−) exhibited enhanced BBB permeability and tight junction dysregulation after WNV infection. Together, these data provide new insight into host-pathogen interactions at the BBB during neurotropic viral infection.

West Nile virus (WNV) is an emerging pathogen capable of infecting the central nervous system (CNS), causing fatal encephalitis. However, the mechanisms that control the ability of WNV to cross the blood-brain barrier (BBB) and access the CNS are unclear. In this study, we show that detection of WNV by host tissues induces innate immune cytokine expression at the BBB, regulating BBB structure and function and impacting transendothelial trafficking of WNV. This regulatory effect is shown to happen rapidly following exposure to virus, to occur independently of viral replication within BBB cells, and to require the signaling of cytoskeletal regulatory Rho GTPases. These results provide new understanding of host-pathogen interactions at the BBB during viral encephalitis.

The role of gut-liver axis in the pathogenesis of liver cirrhosis and portal hypertension

Because of the anatomical position and its unique vascular system, the liver is susceptible to the exposure to the microbial products from the gut. Although large amount of microbes colonize in the gut, translocation of the microbes or microbial products into the liver and systemic circulation is prevented by gut epithelial barrier function and cleansing and detoxifying functions of the liver in healthy subjects. However, when the intestinal barrier function is disrupted, large amount of bacterial products can enter into the liver and systemic circulation and induce inflammation through their receptors. Nowadays, there have been various reports suggesting the role of gut flora and bacterial translocation in the pathogenesis of chronic liver disease and portal hypertension. This review summarizes the current knowledge about bacterial translocation and its contribution to the pathogenesis of chronic liver diseases and portal hypertension.

Type I IFN-mediated regulation of IL-1 production in inflammatory disorders

Although contributing to inflammatory responses and to the development of certain autoimmune pathologies, type I interferons (IFNs) are used for the treatment of viral, malignant, and even inflammatory diseases. Interleukin-1 (IL-1) is a strongly pyrogenic cytokine and its importance in the development of several inflammatory diseases is clearly established. While the therapeutic use of IL-1 blocking agents is particularly successful in the treatment of innate-driven inflammatory disorders, IFN treatment has mostly been appreciated in the management of multiple sclerosis. Interestingly, type I IFNs exert multifaceted immunomodulatory effects, including the reduction of IL-1 production, an outcome that could contribute to its efficacy in the treatment of inflammatory diseases. In this review, we summarize the current knowledge on IL-1 and IFN effects in different inflammatory disorders, the influence of IFNs on IL-1 production, and discuss possible therapeutic avenues based on these observations.

Type I interferon inhibits interleukin-1 production and inflammasome activation

Type I interferon (IFN) is a common therapy for autoimmune and inflammatory disorders, yet the mechanisms of action are largely unknown. Here we showed that type I IFN inhibited interleukin-1 (IL-1) production through two distinct mechanisms. Type I IFN signaling, via the STAT1 transcription factor, repressed the activity of the NLRP1 and NLRP3 inflammasomes, thereby suppressing caspase-1-dependent IL-1β maturation. In addition, type I IFN induced IL-10 in a STAT1-dependent manner; autocrine IL-10 then signaled via STAT3 to reduce the abundance of pro-IL-1α and pro-IL-1β. In vivo, poly(I:C)-induced type I IFN diminished IL-1β production in response to alum and Candida albicans, thus increasing susceptibility to this fungal pathogen. Importantly, monocytes from multiple sclerosis patients undergoing IFN-β treatment produced substantially less IL-1β than monocytes derived from healthy donors. Our findings may thus explain the effectiveness of type I IFN in the treatment of inflammatory diseases but also the observed "weakening" of the immune system after viral infection.

The unfolding web of innate immune dysregulation in alcoholic liver injury

Inflammatory cell and cytokine cascade activation is present in humans with alcoholic liver disease as well as in animal models of alcohol-induced liver damage. Gut-derived lipopolysaccharide (LPS), a ligand of the Toll-like receptor 4 (TLR4), plays a central role in triggering and maintaining activation of Kupffer cells in alcoholic hepatitis. In this mini-review, we describe molecular mechanisms that lead to increased inflammatory cell activation by alcohol and LPS and discuss the mechanism for activation in alcohol-exposed macrophages. In alcohol-induced liver disease we discuss the role of MyD88-independent but IRF3-mediated TLR4 signaling in alcohol-related liver inflammation and liver damage.

Rationale and efficacy of interleukin-1 targeting in Erdheim-Chester disease

Erdheim-Chester disease (ECD) pathophysiology remains largely unknown. Its treatment is not codified and usually disappointing. Interferon (IFN)-α therapy lacks efficacy for some life-threatening manifestations and has a poor tolerance profile. Because interleukin (IL)-1Ra synthesis is naturally induced after stimulation by IFN-α, we hypothesized that recombinant IL-1Ra (anakinra) might have some efficacy in ECD. We treated 2 patients who had poor tolerance or contraindication to IFN-α with anakinra as a rescue therapy and measured their serum C-reactive protein, IL-1β, IL-6, and monocytic membranous IL-1α (mIL-1α) levels before, under, and after therapy. Another untreated ECD patient and 5 healthy subjects were enrolled as controls. After treatment, fever and bone pains rapidly disappeared in both patients, as well as eyelid involvement in one patient. In addition, retroperitoneal fibrosis completely or partially regressed, and C-reactive protein, IL-6, and mIL-1α levels decreased to within the normal and control range. Beside injection-site reactions, no adverse event was reported. Therefore, our results support a central role of the IL-1 network, which seemed to be overstimulated in ECD. Its specific blockade using anakinra thereby opens new pathophysiology and therapeutic perspectives in ECD.

Toll-like receptors in the pathogenesis of alcoholic liver disease

In the multifactorial pathophysiology of alcoholic liver disease (ALD), inflammatory cascade activation plays a central role. Recent studies demonstrated that Toll-like Receptors, the sensors of microbial and endogenous danger signals, are expressed and activated in innate immune cells as well as in parenchymal cells in the liver and thereby contribute to ALD. In this paper, we discuss the importance of gut-derived endotoxin and its recognition by TLR4. The significance of TLR-induced intracellular signaling pathways and cytokine production as well as the contribution of reactive oxygen radicals is evaluated. The contribution of TLR signaling to induction of liver fibrosis and hepatocellular cancer is reviewed in the context of alcohol-induced liver disease.

Tyrosine kinase 2 controls IL-1ß production at the translational level

IL-1beta is an important proinflammatory cytokine with a major role in several inflammatory diseases. Expression of IL-1beta is tightly regulated at the level of transcription, mRNA stability, and proteolytic processing. In this study, we report that IL-1beta expression in response to LPS is also regulated at the translational level. LPS-induced IL-1beta protein levels in macrophages derived from murine bone marrow are markedly increased in the absence of tyrosine kinase 2 (Tyk2). Increased IL-1beta is found intra- and extracellularly, irrespective of the efficiency of IL-1beta processing. We show that the absence of Tyk2 results both in higher translational rates and in enhanced association of IL-1beta mRNA with polysomes. Induction and stability of IL-1beta mRNA are not affected by the lack of Tyk2. We show further that the Tyk2-dependent translational inhibition is mediated by autocrine/paracrine type I IFN signaling and requires signal transducer and activator of transcription 1. Enhanced IL-1beta production in Tyk2- and IFN receptor 1-deficient macrophages is also observed following Listeria monocytogenes infection. Taken together, the data describe a novel mechanism for the control of IL-1beta synthesis.

Immune cell crosstalk in type 1 diabetes

The development of type 1 diabetes involves a complex interaction between pancreatic beta-cells and cells of both the innate and adaptive immune systems. Analyses of the interactions between natural killer (NK) cells, NKT cells, different dendritic cell populations and T cells have highlighted how these different cell populations can influence the onset of autoimmunity. There is evidence that infection can have either a potentiating or inhibitory role in the development of type 1 diabetes. Interactions between pathogens and cells of the innate immune system, and how this can influence whether T cell activation or tolerance occurs, have been under close scrutiny in recent years. This Review focuses on the nature of this crosstalk between the innate and the adaptive immune responses and how pathogens influence the process.

Alcoholic liver disease and the gut-liver axis

Alcoholic liver disease (ALD) is one of the leading causes of liver diseases and liver-related death worldwide. Of the many factors that contribute to the pathogenesis of ALD, gut-derived lipopolysaccharide (LPS) plays a central role in induction of steatosis, inflammation, and fibrosis in the liver. In this review, we discuss the mechanisms by which alcohol contributes to increased gut permeability, the activation of Kupffer cells, and the inflammatory cascade by LPS. The role of the Toll-like receptor 4 (TLR4) complex in LPS recognition and the importance of the TLR4-induced signaling pathways are evaluated in ALD.

Type I IFN induced IL1-Ra expression in hepatocytes is mediated by activating STAT6 through the formation of STAT2: STAT6 heterodimer

The biological activities of type I interferons (IFNs) are mediated by their binding to a heterodimer receptor complex (IFNAR1 and IFNAR2), resulting in the activation of the JAK (JAK1 and TYK2)-STAT (1, 2, 3, 5 isotypes) signalling pathway. Although several studies have indicated that IFN-alpha and IFN-beta can activate complexes containing STAT6, the biological role of this activation is still unknown. We found that exposure of hepatoma cells (HuH7 and Hep3B) to IFN-alpha or IFN-beta led to the activation of STAT6. Activated STAT6 in turn induced the formation of STAT2: STAT6 complexes, which led to the secretion of IL-1Ra. The activation of STAT6 by type I IFN in hepatocytes was mediated by JAK1 and Tyk2. In addition, IFN-alpha or IFN-beta significantly enhanced the stimulatory effect of IL-1beta on production of IL-1Ra. The present study suggests a novel function of IFN-alpha and IFN-beta signalling in human hepatocytes. Our results provide evidence for the mechanism how IFN-alpha and IFN-beta modulate inflammatory responses through activation of STAT6 and production of secreted IL-1Ra.

Interferon-alpha controls IL-17 expression in vitro and in vivo

The type I interferons interferon alpha (IFNalpha) and IFNbeta are the first line of defense potently induced upon viral infection, and at the same time are immunomodulatory cytokines bridging innate and adaptive immunity. T cells secreting interleukin-17 (IL-17) have recently been identified to regulate neutrophil-mediated inflammation, and have been implicated in the pathogenesis of experimental colitis and human inflammatory bowel disease, and are considered to regulate the inflammatory response in these models. We therefore hypothesized that type I IFNs as sentinels of viral infection might counteract the development of Th17 cells. We studied the effects of IFNalpha on IL-17 mRNA and protein expression in human peripheral blood mononuclear cells (PBMC) and during differentiation of human and murine naïve T cells into Th17 cells. In patients with ulcerative colitis (UC) treated systemically with IFNalpha, we studied colonic expression of IL-17 before and 4 weeks after therapy. IFNalpha potently suppressed IL-17 production in PBMC both at the mRNA and protein level. Th17 differentiation of human and murine naïve T cells was markedly suppressed in the presence of IFNalpha. UC patients exhibited increased IL-17 expression in colonic tissue biopsies compared to healthy controls, which was down-regulated during IFNalpha therapy. IL-17 expression in colonic tissue correlated with clinical remission in these patients. Our data suggest that IFNalpha down-regulates IL-17 expression and Th17 differentiation in vitro and in vivo. As a corollary, these effects might play a role in the mode of action of type I IFNs in the treatment of various diseases.

Anti-inflammatory properties of Type I interferons

The notion that Type I interferons (interferon-alpha and -beta) possess anti-inflammatory potential is supported by data from clinical application in multiple sclerosis, by studies on cultured immune-competent cells and by investigation of experimental diseases in whole animals. These observations deserve the attention of virologists for their potential role in the pathogenesis and clinical management of virus infections.

Type I interferons and their therapeutic role in Th2-regulated inflammatory disorders

Cytokines are pleiotropic molecules showing a wide variety of biological functions on various cells and tissues. Several different cytokines exert similar and overlapping functions on certain cells. Interferons (IFNs) play a crucial role in human disease and consist of type I IFNs (IFN-alpha and IFN-beta) and type II IFN (IFN-gamma). The importance of type I IFNs in inflammation, immunoregulation and T cell responses has been recognised, and dendritic cells have recently been identified as the major source of type I IFNs. Type I IFNs are multifunctional immunomodulatory cytokines with profound effects on the cytokine cascade, including several anti-inflammatory properties. They favour both the induction of T helper (Th) 1 cytokines as well as the suppression of Th2 cytokines such as IL-13. Therefore, it is not unexpected that type I IFNs show promising clinical effects in Th2-dominated diseases such as ulcerative colitis and allergic asthma. These newly identified immunoregulatory and anti-inflammatory functions of type I IFNs may be of importance in the treatment of various chronic inflammatory disorders.

Is delayed normalization of alanine aminotransferase a poor prognostic predictor in chronic hepatitis C patients treated with a combined interferon and ribavirin therapy?

BACKGROUND AND AIMS

Decreased alanine aminotransferase (ALT) level is the accepted basic indicator of an interferon (IFN) therapeutic effect in chronic hepatitis C. This study assessed whether delayed normalization of ALT predicts a poor response to a combined therapy of IFN and ribavirin in patients with chronic hepatitis C virus (HCV) infection.

METHODS

Patients were treated with IFN-alpha 2b three times weekly and oral ribavirin for 24 weeks. The ALT values were assessed monthly and patterns of changes in ALT activity were analyzed. Serum HCV-RNA was checked at weeks 0, 12, 24, and 48.

RESULTS

A total of 103 patients completed therapy and 69 (67%) of them achieved a sustained viral response (SVR). There was no significant difference in the SVR between patients with or without early normalization (week 12) of ALT level (69 vs 56%). Of the sustained responders, nine patients (13%) with delayed ALT normalization had a SVR. Nine of the 12 patients (75%) with abnormal ALT and negative HCV-RNA at week 12 had a SVR compared with none of four patients who had positive HCV-RNA at week 12 (P = 0.0192).

CONCLUSIONS

Lack of normalization of the ALT level at week 12 does not preclude successful virological outcome in hepatitis C patients receiving a combined therapy of IFN and ribavirin. Hepatitis C virus RNA at week 12 may be a useful predictor of treatment outcome in patients without early biochemical response.

Association of low-density lipoprotein receptor polymorphisms and outcome of hepatitis C infection

The low-density lipoprotein receptor (LDLR) has been proposed to promote hepatitis C virus endocytosis and the cell membrane protein CD81 may also promote HCV host cell entry. The CD81 gene was sequenced to screen for novel polymorphisms, but no SNPs were identified. Polymorphisms within the LDLR gene are associated with the pathogenesis of familial hypercholesterolemia, atherosclerosis and obesity. We therefore studied genetic variation within the LDLR gene and clinical features of hepatitis C infection. An amino acid change in exon 8 was associated with severity of fibrosis; a SNP in exon 10 correlated with viral clearance and overall inflammation, and a SNP in the 3'UTR appeared to influence treatment response. There were no other significant associations between any of the SNPs studied and the clinical measures of hepatitis C infection. We furthermore report on linkage disequilibrium within the gene and haplotype frequencies in our population. Our findings support a possible role for the LDLR in the modulation of disease progression by affecting immune responses, rather than functioning as receptor for HCV.

Interferon-alpha induces interleukin-18 binding protein in chronic hepatitis C patients

Interleukin-18 (IL-18), derived from macrophages and Kupffer cells, is the central pro-inflammatory cytokine leading to experimental liver failure. IL-18 binding protein (IL-18BP) is a circulating protein that binds IL-18 and neutralizes its activity. Since IL-18 production is increased in chronic HCV infection, we asked whether IFN-alpha might act on the IL-18/IL-18BP system in HCV patients. IL-18BP, total and free IL-18 plasma levels were determined in 13 HCV patients receiving 1 x 107 IU IFN-alpha subcutaneously daily for 28 days. The in vitro effects of IFN-alpha on macrophage IL-18BP and IL-18 were studied by enzyme-linked immunosorbent assays and Northern analysis. IFN-alpha administration increased IL-18BP plasma levels 3.24 fold 24 h after institution of therapy, resulting in a 67.4% reduction of free IL-18. Total IL-18 levels decreased from day +24 on. In vitro, IFN-alpha diminished IL-18 release from macrophages of healthy volunteers and chronic HCV patients. On top of its inhibitory effects on IL-1 and TNF-alpha release, IFN-alpha also exerts its anti-inflammatory action in vivo by induction of IL-18BP. These anti-inflammatory properties might account - together with its antiviral action - for its clinical efficacy in chronic hepatitis C.

Induction of IL-1Ra in resistant and responsive hepatitis C patients following treatment with IFN-con1

Hepatitis C virus (HCV) infection is resistant to interferon-alpha (IFN-alpha) in some patients. The mechanism of this resistance is unknown. Interleukin-1 receptor antagonist (IL-1Ra) is induced by IFN-alpha and is a good indicator of IFN activity. In the current study, we compared IL-1Ra levels in rapid virologic responders and flat responders who showed resistance to IFN. Three groups of patients were examined, including those who received a single dose of consensus IFN (IFN-con1), patients who received daily IFN-con1 for 1 week, and patients who received IFN-con1 daily for 24 weeks. Serum IL-1Ra, IL-6, and HCV RNA were measured serially in all groups. Serum IL-1Ra levels increased rapidly in all patients with hepatitis C after IFN-alpha administration, irrespective of their virologic response. IL-1Ra levels remained elevated at 1 week but were similar to baseline by week 2 of treatment in patients receiving continuous therapy. IL-6 levels also increased acutely but rose more slowly than IL-1Ra levels. The increase in IL-1Ra and IL-6 observed in both flat and rapid virologic responders indicates that IFN receptors are functioning in patients with IFN-resistant hepatitis C and that the lack of response is related to other virologic or immunologic factors.

IL-12 Induces IFN Regulating Factor-1 (IRF-1) Gene Expression in Human NK and T Cells

IL-12 is a critical immunoregulatory cytokine that promotes cell-mediated immune responses and the differentiation of naive CD4+ cells to Th1 cells; however, relatively few IL-12 target genes have been identified. To better clarify the molecular basis of IL-12 action, we set out to characterize genes up-regulated by IL-12, first by contrasting IL-12- and IFN-α-inducible genes. We identified several genes up-regulated by IL-12, namely, MIP-1α, MIP-1β, IL-1RA, and IFN regulatory factor-1 (IRF-1). IRF-1 is a transcription factor regulated by IFNs that is also essential for Th1 responses. We demonstrated that IL-12 directly up-regulates IRF-1 to the same extent as IFN-α in normal human T cells and in NK cells. We showed that IL-12 had a direct effect on IRF-1, an effect not mediated indirectly by the induction of IFN-γ production. Furthermore, IL-2 and IL-12 synergistically induced IRF-1, whereas IFN-α and IL-12 did not. The participation of STAT4 in the regulation of IRF-1 was demonstrated in two ways. First, STAT4 was required for the IL-12-dependent transactivation of an IRF-1 reporter construct, and second, STAT4 binding to the IRF-1 promoter was shown using EMSA. In contrast to IL-12, no up-regulation of IRF-1 was found in IL-4-stimulated cells, and IL-4 did not block IL-12-dependent up-regulation of IRF-1. Therefore, IRF-1 may be an important contributor to IL-12 signaling, and we speculate that the defective IL-12 responses seen in IRF-1−/− mice might be attributable, in part, to the absence of this transcription factor.

Amelioration of collagen-induced arthritis and suppression of interferon-gamma, interleukin-12, and tumor necrosis factor alpha production by interferon-beta gene therapy

OBJECTIVE

To investigate the therapeutic effects and possible mechanisms of action of constitutive expression of interferon-beta (IFNbeta) by syngeneic fibroblasts from DBA/1 mice in the collagen-induced arthritis (CIA) model.

METHODS

Immortalized embryonic DBA/1 fibroblasts were infected with a retrovirus expressing murine IFNbeta. IFNbeta-expressing fibroblasts were then implanted intraperitoneally into mice immunized with bovine type II collagen. The effect of IFNbeta on paw swelling, anticollagen antibody levels, IgG1/IgG2a isotype profiles, arthritis score, histologic joint damage, and cytokine secretion from lymph node cells and from bone marrow-derived macrophages was assessed.

RESULTS

A single injection of IFNbeta-secreting fibroblasts was sufficient to prevent arthritis or to ameliorate existing disease. Thus, IFNbeta reduced the clinical score and paw swelling irrespective of whether the injection was administered before or after disease onset in treated mice, compared with that in the untreated control group (P < 0.05). Histologic findings in the IFNbeta-treated mice were markedly less severe than in the control group (P < 0.001). This effect was accompanied by a decrease in total anticollagen IgG levels, a decrease in anticollagen IgG2a, and an increase in IgG1. In vitro, supernatants from these engineered fibroblasts inhibited collagen-induced interferon-gamma secretion from lymph node cells, and reduced the levels of tumor necrosis factor alpha and interleukin-12 produced by lipopolysaccharide/IFNgamma-treated bone marrow-derived macrophages. This effect was specific, since it was reversed with anti-IFNbeta polyclonal antibodies.

CONCLUSION

These results indicate that IFNbeta, which is currently used as a treatment for relapsing, remitting multiple sclerosis, is a potent immunomodulatory and antiinflammatory cytokine in CIA and should be considered for the treatment of rheumatoid arthritis.

Spontaneous and inducible cytokine responses in healthy humans receiving a single dose of IFN-alpha2b: increased production of interleukin-1 receptor antagonist and suppression of IL-1-induced IL-8

The present study was to determine whether the administration of a single dose of interferon-alpha2B (IFN-alpha2B) to healthy humans affects endogenous (or basal level) or inducible cytokines in a whole blood, ex vivo culture. Twenty-four healthy volunteers received an s.c. injection of IFN-alpha2b (3 x 10(6)U), and 4 volunteers received the vehicle as placebo. The study was blinded. Blood was drawn before and 3, 6, 12, and 24 h after the injection and incubated in the presence or absence of lipopolysaccharide (LPS) or interleukin-1beta (IL-1beta). After 24 hs, the plasma was assayed for tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, IL-1beta, IL-1 receptor antagonist (IL-1Ra), and IL-8. Treatment with IFN-alpha2b was associated with a 4.8-fold increase in the endogenous production of IL-1Ra in cultured blood sustained over 24 hs. In contrast, no change in endogenous IL-1Ra production was detected in the controls. A significant suppression (75%, p < 0.001) of IL-1beta-induced IL-8 production 3 and 6 h after IFN-alpha2b compared with control subjects was observed. These effects were also observed when IFN-alpha2b was added directly to whole blood cultures in vitro. In contrast to IL-1 stimulation, LPS stimulation of blood from IFN-alpha2b-treated subjects resulted in enhanced IL-1beta and TNF-alpha production. These results suggest that a single dose of IFN-alpha2b induces an anti-inflammatory state for endogenous stimuli but a proinflammatory state for exogenous endotoxin.

Treatment of chronic hepatitis C virus infection with recombinant consensus interferon

To assess the safety and efficacy of consensus interferon (IFN-Con-1), 55 patients with chronic hepatitis C infection were treated with either 3, 6, 9, 12, or 15 microg IFN-Con-1 s.c. three times a week for 24 weeks, followed by 24 weeks of observation. There was a dose-response relationship with respect to the number of patients with normalized ALT concentrations or undetectable HCV RNA. At the end of the 24-week treatment period, the serum ALT had normalized in 18% of patients given the 3 microg dose and 42% of patients given the 12 microg or 15 microg doses of IFN-Con-1. At the end of the posttreatment observation period, the serum ALT was still normal in 10% of patients given the 3 microg, 6 microg, or 9 microg doses and in 50% of patients given the 15 microg dose. Also, at the end of the 24-week treatment period, 27% of patients given the 3 microg dose and 75% given the 15 microg dose had undetectable serum HCV RNA. At the end of the posttreatment observation period, the proportion of patients with undetectable HCV RNA ranged from 9% of those given the 3 microg dose to 50% of those given the 15 microg dose. Our study indicates that treatment with IFN-Con-1 appears to be safe and effective. In addition, use of 15 microg of IFN-Con-1 resulted in significantly more patients with sustained ALT normalization and absence of HCV RNA 6 months after cessation of therapy compared with treatment with lower doses of IFN-Con-1. Additional trials are underway to confirm these findings.

Interferon-alpha and its effects on the cytokine cascade: a pro- and anti-inflammatory cytokine

Interferon-alpha (IFN alpha) has emerged as an important regulator of growth and differentiation, affecting cellular communication and signal transduction pathways as well as immunological control. The efficacy of IFN alpha has been demonstrated in many different diseases of viral, malignant, angiogenic, allergic, inflammatory, and fibrotic origin. Cytokines are pleiotropic and redundant molecules showing a wide variety of biologic functions on various tissues and cells, and several different cytokines exert similar and overlapping functions on certain cells. Data gained in the last years support this view also for IFN alpha. Initially thought to have mainly immunomodulating and proinflammatory effects, recent data suggest that IFN alpha has several anti-inflammatory properties. These newly identified anti-inflammatory and immunosuppressive functions may help to explain some of the IFN mechanisms.

Interferon-beta prevents the upregulation of interleukin-8 expression in human melanoma cells

The constitutive expression of interleukin-8 (IL-8) by human melanoma cells correlates with their metastatic potential. The exposure of human melanoma cells to the inflammatory cytokines IL-1 beta or tumor necrosis factor-alpha (TNF-alpha) upregulated IL-8 expression in a time-dependent and concentration-dependent manner. This enhanced expression of IL-8 was inhibited by cycloheximide or actinomycin-D. Treatment of melanoma cells with interferon (IFN) alpha, beta, or gamma did not affect the constitutive expression of IL-8, but IFN-alpha and IFN-beta blocked the upregulation of IL-8 expression in cells treated with IL-1 beta or TNF-alpha subsequent to or simultaneously with the IFN. These data suggest that the expression of IL-8 in human melanoma cells can be upregulated by inflammatory cytokines and that IFN-alpha and IFN-beta can counterregulate this stimulation.

The biologic activity and molecular characterization of a novel synthetic interferon-alpha species, consensus interferon

Consensus interferon (Infergen) is a wholly synthetic type I interferon (IFN), developed by scanning several interferon-alpha nonallelic subtypes and assigning the most frequently observed amino acid in each position, resulting in a consensus sequence. The antiviral, antiproliferative, NK cell activation activity, cytokine induction, and interferon-stimulated gene-induction activity of consensus interferon has been compared with naturally occurring type I interferons. In all of these comparisons, consensus interferon had a higher activity when compared, on a mass basis, with IFN-alpha 2a and IFN-alpha 2b, although the activity was the same for all of these parameters on an antiviral unit basis. That a synthetic type I interferon could have higher activities than naturally occurring molecules is surprising and may be a result of the higher affinity for the array of type I interferon receptors demonstrated for consensus interferon when compared with IFN-alpha. In contrast, consensus interferon was shown to be an inferior inducer of IL-1 beta when compared with IFN-alpha. These results may reflect differential binding to multiple accessory proteins interacting with a type I interferon receptor. These unique biologic properties may lead to a favorable clinical benefit for consensus interferon when compared with the naturally occurring recombinant molecules. Ongoing clinical trials will ascertain whether consensus interferon can be used in a wide array of disease situations, such as chronic viral infections and certain malignancies.