Prevention of Chronic Renal Allograft Rejection by SERP-1 Protein

Viral SERPINS-A Family of Highly Potent Immune-Modulating Therapeutic Proteins

Serine protease inhibitors, SERPINS, are a highly conserved family of proteins that regulate serine proteases in the central coagulation and immune pathways, representing 2-10% of circulating proteins in the blood. Serine proteases form cascades of sequentially activated enzymes that direct thrombosis (clot formation) and thrombolysis (clot dissolution), complement activation in immune responses and also programmed cell death (apoptosis). Virus-derived serpins have co-evolved with mammalian proteases and serpins, developing into highly effective inhibitors of mammalian proteolytic pathways. Through interacting with extracellular and intracellular serine and cysteine proteases, viral serpins provide a new class of highly active virus-derived coagulation-, immune-, and apoptosis-modulating drug candidates. Viral serpins have unique characteristics: (1) function at micrograms per kilogram doses; (2) selectivity in targeting sites of protease activation; (3) minimal side effects at active concentrations; and (4) the demonstrated capacity to be modified, or fine-tuned, for altered protease targeting. To date, the virus-derived serpin class of biologics has proven effective in a wide range of animal models and in one clinical trial in patients with unstable coronary disease. Here, we outline the known viral serpins and review prior studies with viral serpins, considering their potential for application as new sources for immune-, coagulation-, and apoptosis-modulating therapeutics.

ReDisX, a machine learning approach, rationalizes rheumatoid arthritis and coronary artery disease patients uniquely upon identifying subpopulation differentiation markers from their genomic data

Diseases originate at the molecular-genetic layer, manifest through altered biochemical homeostasis, and develop symptoms later. Hence, symptomatic diagnosis is inadequate to explain the underlying molecular-genetic abnormality and individual genomic disparities. The current trends include molecular-genetic information relying on algorithms to recognize the disease subtypes through gene expressions. Despite their disposition toward disease-specific heterogeneity and cross-disease homogeneity, a gap still exists in describing the extent of homogeneity within the heterogeneous subpopulation of different diseases. They are limited to obtaining the holistic sense of the whole genome-based diagnosis resulting in inaccurate diagnosis and subsequent management. Addressing those ambiguities, our proposed framework, ReDisX, introduces a unique classification system for the patients based on their genomic signatures. In this study, it is a scalable machine learning algorithm deployed to re-categorize the patients with rheumatoid arthritis and coronary artery disease. It reveals heterogeneous subpopulations within a disease and homogenous subpopulations across different diseases. Besides, it identifies granzyme B (GZMB) as a subpopulation-differentiation marker that plausibly serves as a prominent indicator for GZMB-targeted drug repurposing. The ReDisX framework offers a novel strategy to redefine disease diagnosis through characterizing personalized genomic signatures. It may rejuvenate the landscape of precision and personalized diagnosis and a clue to drug repurposing.

Myxomavirus Serp-1 Protein Ameliorates Inflammation in a Mouse Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is an X-linked disease afflicting 1 in 3500 males that is characterized by muscle weakness and wasting during early childhood, and loss of ambulation and death by early adulthood. Chronic inflammation due to myofiber instability leads to fibrosis, which is a primary cause of loss of ambulation and cardiorespiratory insufficiency. Current standard of care focuses on reducing inflammation with corticosteroids, which have serious adverse effects. It is imperative to identify alternate immunosuppressants as treatments to reduce fibrosis and mortality. Serp-1, a Myxoma virus-derived 55 kDa secreted glycoprotein, has proven efficacy in a range of animal models of acute inflammation, and its safety and efficacy has been shown in a clinical trial. In this initial study, we examined whether pegylated Serp-1 (PEGSerp-1) treatment would ameliorate chronic inflammation in a mouse model for Duchenne muscular dystrophy. Our data revealed a significant reduction in diaphragm fibrosis and increased myofiber diameter, and significantly decreased pro-inflammatory M1 macrophage infiltration. The M2a macrophage and overall T cell populations showed no change. These data demonstrate that treatment with this new class of poxvirus-derived immune-modulating serpin has potential as a therapeutic approach designed to ameliorate DMD pathology and facilitate muscle regeneration.

Serp-1 Promotes Corneal Wound Healing by Facilitating Re-epithelialization and Inhibiting Fibrosis and Angiogenesis

Purpose: Chemical corneal injuries carry a high morbidity and commonly lead to visual impairment. Here, we investigate the role of Serp-1, a serine protease inhibitor, in corneal wound healing.

Methods: An alkaline-induced corneal injury was induced in 14 mice. Following injury, five mice received daily topical saline application while nine mice received Serp-1 100 μL topically combined with a daily subcutaneous injection of 100 ng/gram body weight of Serp-1. Corneal damage was monitored daily through fluorescein staining and imaging. Cross sectional corneal H&E staining were obtained. CD31 was used as marker for neovascularization.

Results: Serp-1 facilitates corneal wound healing by reducing fibrosis and neovascularization while mitigating inflammatory cell infiltration with no noticeable harm related to its application.

Conclusions: Serp-1 effectively mitigates inflammation, decreases fibrosis, and reduce neovascularization in a murine model of corneal injury without affecting other organs.

Translational Relavence: Our study provides preclinical data for topical application of Serp-1 to treat corneal wounds.

Therapeutic SERPINs: Improving on Nature

Serine proteases drive important physiological processes such as coagulation, fibrinolysis, inflammation and angiogenesis. These proteases are controlled by serine protease inhibitors (SERPINs) that neutralize their activity. Currently, over 1,500 SERPINs are known in nature, but only 37 SERPINs are found in humans. Thirty of these are functional protease inhibitors. The inhibitory potential of SERPINs is in perfect balance with the proteolytic activities of its targets to enable physiological protease activity. Hence, SERPIN deficiency (either qualitative or quantitative) can lead to disease. Several SERPIN resupplementation strategies have been developed to treat SERPIN deficiencies, including concentrates derived from plasma and recombinant SERPINs. SERPINs usually inhibit multiple proteases, but only in their active state. Over the past decades, considerable insights have been acquired in the identification of SERPIN biological functions, their inhibitory mechanisms and specificity determinants. This paves the way for the development of therapeutic SERPINs. Through rational design, the inhibitory properties (selectivity and inhibitory potential) of SERPINs can be reformed and optimized. This review explores the current state of SERPIN engineering with a focus on reactive center loop modifications and backbone stabilization. We will discuss the lessons learned from these recombinant SERPINs and explore novel techniques and strategies that will be essential for the creation and application of the future generation of therapeutic SERPINs.

Fibrinolytic Serine Proteases, Therapeutic Serpins and Inflammation: Fire Dancers and Firestorms

The making and breaking of clots orchestrated by the thrombotic and thrombolytic serine protease cascades are critical determinants of morbidity and mortality during infection and with vascular or tissue injury. Both the clot forming (thrombotic) and the clot dissolving (thrombolytic or fibrinolytic) cascades are composed of a highly sensitive and complex relationship of sequentially activated serine proteases and their regulatory inhibitors in the circulating blood. The proteases and inhibitors interact continuously throughout all branches of the cardiovascular system in the human body, representing one of the most abundant groups of proteins in the blood. There is an intricate interaction of the coagulation cascades with endothelial cell surface receptors lining the vascular tree, circulating immune cells, platelets and connective tissue encasing the arterial layers. Beyond their role in control of bleeding and clotting, the thrombotic and thrombolytic cascades initiate immune cell responses, representing a front line, "off-the-shelf" system for inducing inflammatory responses. These hemostatic pathways are one of the first response systems after injury with the fibrinolytic cascade being one of the earliest to evolve in primordial immune responses. An equally important contributor and parallel ancient component of these thrombotic and thrombolytic serine protease cascades are the serine protease inhibitors, termed serpins. Serpins are metastable suicide inhibitors with ubiquitous roles in coagulation and fibrinolysis as well as multiple central regulatory pathways throughout the body. Serpins are now known to also modulate the immune response, either via control of thrombotic and thrombolytic cascades or via direct effects on cellular phenotypes, among many other functions. Here we review the co-evolution of the thrombolytic cascade and the immune response in disease and in treatment. We will focus on the relevance of these recent advances in the context of the ongoing COVID-19 pandemic. SARS-CoV-2 is a "respiratory" coronavirus that causes extensive cardiovascular pathogenesis, with microthrombi throughout the vascular tree, resulting in severe and potentially fatal coagulopathies.

PEGylated Serp-1 Markedly Reduces Pristane-Induced Experimental Diffuse Alveolar Hemorrhage, Altering uPAR Distribution, and Macrophage Invasion

Diffuse alveolar hemorrhage (DAH) is one of the most serious clinical complications of systemic lupus erythematosus (SLE). The prevalence of DAH is reported to range from 1 to 5%, but while DAH is considered a rare complication there is a reported 50-80% mortality. There is at present no proven effective treatment for DAH and the therapeutics that have been tested have significant side effects. There is a clear necessity to discover new drugs to improve outcomes in DAH. Serine protease inhibitors, serpins, regulate thrombotic and thrombolytic protease cascades. We are investigating a Myxomavirus derived immune modulating serpin, Serp-1, as a new class of immune modulating therapeutics for vasculopathy and lung hemorrhage. Serp-1 has proven efficacy in models of herpes virus-induced arterial inflammation (vasculitis) and lung hemorrhage and has also proved safe in a clinical trial in patients with unstable coronary syndromes and stent implant. Here, we examine Serp-1, both as a native secreted protein expressed by CHO cells and as a polyethylene glycol modified (PEGylated) variant (Serp-1m5), for potential therapy in DAH. DAH was induced by intraperitoneal (IP) injection of pristane in C57BL/6J (B6) mice. Mice were treated with 100 ng/g bodyweight of either Serp-1 as native 55 kDa secreted glycoprotein, or as Serp-1m5, or saline controls after inducing DAH. Treatments were repeated daily for 14 days (6 mice/group). Serp-1 partially and Serp-1m5 significantly reduced pristane-induced DAH when compared with saline as assessed by gross pathology and H&E staining (Serp-1, p = 0.2172; Serp-1m5, p = 0.0252). Both Serp-1m5 and Serp-1 treatment reduced perivascular inflammation and reduced M1 macrophage (Serp-1, p = 0.0350; Serp-1m5, p = 0.0053), hemosiderin-laden macrophage (Serp-1, p = 0.0370; Serp-1m5, p = 0.0424) invasion, and complement C5b/9 staining. Extracellular urokinase-type plasminogen activator receptor positive (uPAR+) clusters were significantly reduced (Serp-1, p = 0.0172; Serp-1m5, p = 0.0025). Serp-1m5 also increased intact uPAR+ alveoli in the lung (p = 0.0091). In conclusion, Serp-1m5 significantly reduces lung damage and hemorrhage in a pristane model of SLE DAH, providing a new potential therapeutic approach.

Preclinical Testing of Viral Therapeutic Efficacy in Pristane-Induced Lupus Nephritis and Diffuse Alveolar Hemorrhage Mouse Models

Systemic lupus erythematosus (SLE) is a multifactorial and heterogeneous autoimmune disease involving multiple organ systems and tissues. Lupus nephritis occurs in approximately 60% of patients with SLE and is the leading cause of morbidity. Diffuse alveolar hemorrhage (DAH) is a rare but very serious complication of SLE with a greater than 50% associated mortality. The etiology of SLE is unclear but has proposed genetic, hormonal, and environmental aspects. Pristane is a saturated terpenoid alkane and has become the most popular laboratory model for inducing lupus in mice. The pristane model of SLE has the capacity to reproduce many components of the human presentation of the disease. Previous studies have demonstrated that virus-derived immune-modulating proteins have the potential to control inflammatory and autoimmune disorders. Serp-1, a 55 kDa secreted and highly glycosylated immune modulator derived from myxoma virus (MYXV), has potent immunomodulatory activity in models of vasculitis, viral sepsis, collagen-induced arthritis, and transplant rejection. This chapter describes the mouse preclinical pristane lupus model as a method to examine virus-derived protein efficacy for treating autoimmune diseases and specifically lupus nephritis and DAH.

The Pathogenesis of Neurotrauma Indicates Targets for Neuroprotective Therapies

The spinal cord injury (SCI) initiates an extraordinarily protracted disease with 3 phases; acute, inflammatory, and resolution that are restricted to the cavity of injury (COI) or arachnoiditis by a unique CNS reaction against the severity of destructive inflammation. While the severity of inflammation involving the white matter is fueled by a potently immunogenic activity of damaged myelin, its sequestration in the COI and its continuity with the cerebrospinal fluid of the subdural space allow anti-inflammatory therapeutics infused subdurally to inhibit phagocytic macrophage infiltration and thus provide neuroprotection. The role of astrogliosis in containing and ultimately in eliminating severe destructive inflammation post-trauma appears obvious but is not yet sufficiently understood to use in therapeutic neuroprotective and neuroregenerative strategies. An apparent antiinflammatory activity of reactive astrocytes is paralleled by their active role in removing excess edema fluid in blood-brain barrier damaged by inflammation. Recently elucidated pathogenesis of neurotrauma, including SCI, traumatic brain injury (TBI), and stroke, calls for the following principal therapeutic steps in its treatment leading to the recovery of neurologic function: (1) inhibition and elimination of destructive inflammation from the COI with accompanying reduction of vasogenic edema, (2) insertion into the COI of a functional bridge supporting the crossing of regenerating axons, (3) enabling regeneration of axons to their original synaptic targets by temporary safe removal of myelin in targeted areas of white matter, (4) in vivo, systematic monitoring of the consecutive therapeutic steps. The focus of this paper is on therapeutic step 1.

Activity-based Protein Profiling Approaches for Transplantation

Enzyme activity may be more pathophysiologically relevant than enzyme quantity and is regulated by changes in conformational status that are undetectable by traditional proteomic approaches. Further, enzyme activity may provide insights into rapid physiological responses to inflammation/injury that are not dependent on de novo protein transcription. Activity-based protein profiling (ABPP) is a chemical proteomic approach designed to characterize and identify active enzymes within complex biological samples. Activity probes have been developed to interrogate multiple enzyme families with broad applicability, including but not limited to serine hydrolases, cysteine proteases, matrix metalloproteases, nitrilases, caspases, and histone deacetylases. The goal of this overview is to describe the overall rationale, approach, methods, challenges, and potential applications of ABPP to transplantation research. To do so, we present a case example of urine serine hydrolase ABPP in kidney transplant rejection to illustrate the utility and workflow of this analytical approach. Ultimately, developing novel transplant therapeutics is critically dependent on understanding the pathophysiological processes that result in loss of transplant function. ABPP offers a new dimension for characterizing dynamic changes in clinical samples. The capacity to identify and measure relevant enzyme activities provides fresh opportunities for understanding these processes and may help identify markers of disease activity for the development of novel diagnostics and real-time monitoring of patients. Finally, these insights into enzyme activity may also help to identify new transplant therapeutics, such as enzyme-specific inhibitors.

Deriving Immune Modulating Drugs from Viruses-A New Class of Biologics

Viruses are widely used as a platform for the production of therapeutics. Vaccines containing live, dead and components of viruses, gene therapy vectors and oncolytic viruses are key examples of clinically-approved therapeutic uses for viruses. Despite this, the use of virus-derived proteins as natural sources for immune modulators remains in the early stages of development. Viruses have evolved complex, highly effective approaches for immune evasion. Originally developed for protection against host immune responses, viral immune-modulating proteins are extraordinarily potent, often functioning at picomolar concentrations. These complex viral intracellular parasites have "performed the R&D", developing highly effective immune evasive strategies over millions of years. These proteins provide a new and natural source for immune-modulating therapeutics, similar in many ways to penicillin being developed from mold or streptokinase from bacteria. Virus-derived serine proteinase inhibitors (serpins), chemokine modulating proteins, complement control, inflammasome inhibition, growth factors (e.g., viral vascular endothelial growth factor) and cytokine mimics (e.g., viral interleukin 10) and/or inhibitors (e.g., tumor necrosis factor) have now been identified that target central immunological response pathways. We review here current development of virus-derived immune-modulating biologics with efficacy demonstrated in pre-clinical or clinical studies, focusing on pox and herpesviruses-derived immune-modulating therapeutics.

A Virus-Derived Immune Modulating Serpin Accelerates Wound Closure with Improved Collagen Remodeling

Numerous treatments have been developed to promote wound healing based on current understandings of the healing process. Hemorrhaging, clotting, and associated inflammation regulate early wound healing. We investigated treatment with a virus-derived immune modulating serine protease inhibitor (SERPIN), Serp-1, which inhibits thrombolytic proteases and inflammation, in a mouse excisional wound model. Saline or recombinant Serp-1 were applied directly to wounds as single doses of 1 μg or 2 µg or as two 1 µg boluses. A chitosan-collagen hydrogel was also tested for Serp-1 delivery. Wound size was measured daily for 15 days and scarring assessed by Masson’s trichrome, Herovici’s staining, and immune cell dynamics and angiogenesis by immunohistochemistry. Serp-1 treatment significantly accelerated wound healing, but was blocked by urokinase-type plasminogen activator (uPAR) antibody. Repeated dosing at a lower concentration was more effective than single high-dose serpin. A single application of Serp-1-loaded chitosan-collagen hydrogel was as effective as repeated aqueous Serp-1 dosing. Serp-1 treatment of wounds increased arginase-1-expressing M2-polarized macrophage counts and periwound angiogenesis in the wound bed. Collagen staining also demonstrated that Serp-1 improves collagen maturation and organization at the wound site. Serp-1 has potential as a safe and effective immune modulating treatment that targets thrombolytic proteases, accelerating healing and reducing scar in deep cutaneous wounds.

Serp-2, a virus-derived apoptosis and inflammasome inhibitor, attenuates liver ischemia-reperfusion injury in mice

BACKGROUND

Ischemia-reperfusion injury (IRI) is an antigen-independent, innate immune response to arterial occlusion and ischemia with subsequent paradoxical exacerbation after reperfusion. IRI remains a critical problem after vessel occlusion and infarction or during harvest and surgery in transplants. After transplant, liver IRI (LIRI) contributes to increased acute and chronic rejection and graft loss. Tissue loss during LIRI has been attributed to local macrophage activation and invasion with excessive inflammation together with hepatocyte apoptosis and necrosis. Inflammatory and apoptotic signaling are key targets for reducing post-ischemic liver injury.Myxomavirus is a rabbit-specific leporipoxvirus that encodes a suite of immune suppressing proteins, often with extensive function in other mammalian species. Serp-2 is a cross-class serine protease inhibitor (serpin) which inhibits the inflammasome effector protease caspase-1 as well as the apoptotic proteases granzyme B and caspases 8 and 10. In prior work, Serp-2 reduced inflammatory cell invasion after angioplasty injury and after aortic transplantation in rodents. In this report, we explore the potential for therapeutic treatment with Serp-2 in a mouse model of LIRI.

METHODS

Wildtype (C57BL/6 J) mice were subjected to warm, partial (70%) hepatic ischemia for 90 min followed by treatment with saline or Serp-2 or M-T7, 100 ng/g/day given by intraperitoneal injection on alternate days for 5 days. M-T7 is a Myxomavirus-derived inhibitor of chemokine-GAG interactions and was used in this study for comparative analysis of an unrelated viral protein with an alternative immunomodulating mechanism of action. Survival, serum ALT levels and histopathology were assessed 24 h and 10 days post-LIRI.

RESULTS

Serp-2 treatment significantly improved survival to 85.7% percent versus saline-treated wildtype mice (p = 0.0135), while M-T7 treatment did not significantly improve survival (p = 0.2584). Liver viability was preserved by Serp-2 treatment with a significant reduction in serum ALT levels (p = 0.0343) and infarct scar thickness (p = 0.0016), but with no significant improvement with M-T7 treatment. Suzuki scoring by pathologists blinded with respect to treatment group indicated that Serp-2 significantly reduced hepatocyte necrosis (p = 0.0057) and improved overall pathology score (p = 0.0046) compared to saline. Immunohistochemistry revealed that Serp-2 treatment reduced macrophage infiltration into the infarcted liver tissue (p = 0.0197).

CONCLUSIONS

Treatment with Serp-2, a virus-derived inflammasome and apoptotic pathway inhibitor, improves survival after liver ischemia-reperfusion injury in mouse models. Treatment with a cross-class immune modulator provides a promising new approach designed to reduce ischemia-reperfusion injury, improving survival and reducing chronic transplant damage.

Serpins: Development for Therapeutic Applications

Serine protease inhibitors, or serpins, function as central regulators for many vital processes in the mammalian body, maintaining homeostasis for clot formation and breakdown, immune responses, lung function, and hormone or central nervous system activity, among many others. When serine protease activity or serpin-mediated regulation becomes unbalanced or dysfunctional, then severe disease states and pathogenesis can ensue. With serpinopathies, genetic mutations lead to inactive serpins or protein aggregation with loss of function. With other disorders, such as sepsis, atherosclerosis, cancer, obesity, and the metabolic syndrome, the thrombotic and thrombolytic cascades and/or inflammatory responses become unbalanced, with excess bleeding and clotting and upregulation of adverse immune responses. Returning overall balance can be engineered through introduction of a beneficial serpin replacement as a therapeutic or through blockade of serpins that are detrimental. Several drugs have been developed and are currently in use and/or in development both to replace dysfunctional serpins and to block adverse effects induced by aberrant protease or serpin actions.With this chapter, we provide a general overview of the development of a virus-derived serpin, Serp-1, and serpin reactive center loop (RCL) peptides, as therapeutics. Serp-1 is a virus-derived serpin developed as a new class of immune modulator. We will use the development of Serp-1 as a general introduction to serpin-based drug development.

Reactive Center Loop (RCL) Peptides Derived from Serpins Display Independent Coagulation and Immune Modulating Activities

Serpins regulate coagulation and inflammation, binding serine proteases in suicide-inhibitory complexes. Target proteases cleave the serpin reactive center loop scissile P1-P1' bond, resulting in serpin-protease suicide-inhibitory complexes. This inhibition requires a near full-length serpin sequence. Myxomavirus Serp-1 inhibits thrombolytic and thrombotic proteases, whereas mammalian neuroserpin (NSP) inhibits only thrombolytic proteases. Both serpins markedly reduce arterial inflammation and plaque in rodent models after single dose infusion. In contrast, Serp-1 but not NSP improves survival in a lethal murine gammaherpesvirus68 (MHV68) infection in interferon γ-receptor-deficient mice (IFNγR(-/-)). Serp-1 has also been successfully tested in a Phase 2a clinical trial. We postulated that proteolytic cleavage of the reactive center loop produces active peptide derivatives with expanded function. Eight peptides encompassing predicted protease cleavage sites for Serp-1 and NSP were synthesized and tested for inhibitory function in vitro and in vivo. In engrafted aorta, selected peptides containing Arg or Arg-Asn, not Arg-Met, with a 0 or +1 charge, significantly reduced plaque. Conversely, S-6 a hydrophobic peptide of NSP, lacking Arg or Arg-Asn with -4 charge, induced early thrombosis and mortality. S-1 and S-6 also significantly reduced CD11b(+) monocyte counts in mouse splenocytes. S-1 peptide had increased efficacy in plasminogen activator inhibitor-1 serpin-deficient transplants. Plaque reduction correlated with mononuclear cell activation. In a separate study, Serp-1 peptide S-7 improved survival in the MHV68 vasculitis model, whereas an inverse S-7 peptide was inactive. Reactive center peptides derived from Serp-1 and NSP with suitable charge and hydrophobicity have the potential to extend immunomodulatory functions of serpins.

Quantitative proteomic profiling of renal tissue in human chronic rejection biopsy samples after renal transplantation

INTRODUCTION

Chronic rejection (CR) is the leading cause of late renal transplant failure and is characterized by a relatively slow but progressive loss of renal function in combination with proteinuria and hypertension >3 months after transplantation. To identify and quantify the protein profiles in renal tissues of CR patients, we used isotope tagging for relative and absolute quantification (iTRAQ)-based proteomic technology to perform global protein expression analyses in CR patients and control subjects.

MATERIALS AND METHODS

After protein extraction, quantitation, and digestion, samples were labeled with iTRAQ reagents and then separated by strong cation exchange and high-performance liquid chromatography. The fractions were further analyzed by tandem mass spectrometry. ProteinPilot version 4.0 software and the Swiss-Prot human database were applied for statistical analysis and database searching, respectively. Differentially expressed proteins were subjected to bioinformatic analysis by using the Gene Ontology database and the Kyoto Encyclopedia of Genes and Genomes database to further characterize their potential functional roles and related pathways in CR.

RESULTS

In total, 1857 distinct proteins (confidence >95%, ρ < .05) were identified and quantified. Using a strict cutoff value of 1.5-fold for expressed variation, 87 proteins showed significant differences in expression between the CR and control groups; 53 were up-regulated and 34 were down-regulated. The differentially expressed proteins were mainly involved in protein binding, structural molecule activity, and extracellular matrix structural constituent. Several proteins, such as the alpha-1 chain of collagen type IV and integrin alpha-1, may play roles in the pathogenesis of CR and were implicated in the extracellular matrix-receptor interaction pathway.

CONCLUSIONS

This study is the first to focus on iTRAQ-based quantitative proteomic characterization of renal tissue in CR. These insights may broaden our understanding of the molecular mechanisms underlying CR and provide potential biomarker candidates for future diagnostics.

Serpin treatment suppresses inflammatory vascular lesions in temporal artery implants (TAI) from patients with giant cell arteritis

Giant cell arteritis (GCA) and Takayasu’s disease are inflammatory vasculitic syndromes (IVS) causing sudden blindness and widespread arterial obstruction and aneurysm formation. Glucocorticoids and aspirin are mainstays of treatment, predominantly targeting T cells. Serp-1, a Myxomavirus-derived serpin, blocks macrophage and T cells in a wide range of animal models. Serp-1 also reduced markers of myocardial injury in a Phase IIa clinical trial for unstable coronary disease. In recent work, we detected improved survival and decreased arterial inflammation in a mouse Herpesvirus model of IVS. Here we examine Serp-1 treatment of human temporal artery (TA) biopsies from patients with suspected TA GCA arteritis after implant (TAI) into the aorta of immunodeficient SCID (severe combined immunodeficiency) mice. TAI positive for arteritis (GCA^pos) had significantly increased inflammation and plaque when compared to negative TAI (GCA^neg). Serp-1 significantly reduced intimal inflammation and CD11b⁺ cell infiltrates in TAI, with reduced splenocyte Th1, Th17, and Treg. Splenocytes from mice with GCA^pos grafts had increased gene expression for interleukin-1beta (IL-1β), IL-17, and CD25 and decreased Factor II. Serp-1 decreased IL-1β expression. In conclusion, GCA^pos TAI xenografts in mice provide a viable disease model and have increased intimal inflammation as expected and Serp-1 significantly reduces vascular inflammatory lesions with reduced IL-1β.

Suppression of collagen-induced arthritis with a serine proteinase inhibitor (serpin) derived from myxoma virus

Many viruses encode virulence factors to facilitate their own survival by modulating a host's inflammatory response. One of these factors, secreted from cells infected with myxoma virus, is the serine proteinase inhibitor (serpin) Serp-1. Because Serp-1 had demonstrated anti-inflammatory properties in arterial injury models and viral infections, it was cloned and evaluated for therapeutic efficacy in collagen-induced arthritis (CIA). Clinical severity was significantly lower in the Serp-1 protocols (p<0.0001) and blinded radiographs indicated that the Serp-1 group had significantly less erosions than the controls (p<0.01). Delayed-type hypersensitivity was lower in the Serp-1 group but antibody titers to type II collagen were not significantly altered. Recipients had minimal histopathologic synovial changes and did not develop neutralizing antibodies to Serp-1. These results indicate that Serp-1 impedes the pathogenesis of CIA and suggests that the therapeutic potential of serine proteinase inhibitors in inflammatory joint diseases, such as rheumatoid arthritis, should be investigated further.

Viral Anti-Inflammatory Proteins Target Diverging Immune Pathways with Converging Effects on Arterial Dilatation, Plaque and Apoptosis

Abdominal aortic aneurysms are often fatal due to atherosclerosis, thromboembolism, rupture, and hemorrhage, however, treatment is limited to expectant monitoring and surgical intervention. Inflammation is detected in aneurysms and in plaque with associated increased apoptosis, chemokines, cytokines, hemorrhage, and thrombosis. We compared treatment with three different myxomavirus-derived anti-inflammatory proteins targeting apoptosis, thrombosis, and chemokine pathways. The effect of each protein on aortic dilatation and plaque growth was assessed after angioplasty in Apolipoprotein Enull mice. Four myxomavirus-derived proteins were studied; Serp-1 a serine protease inhibitor (serpin) targeting thrombotic and thrombolytic proteases, Serp-2 a cross-class serpin inhibiting granzyme B and caspases 1 and 8, M-T7 a broad spectrum C, CC, and CXC chemokine inhibitor, and R171E, an inactive M-T7 mutant. Cell invasion, elastin breaks, plaque progression, and aortic dilatation were significantly reduced by Serp-1, Serp-2, or M-T7 protein treatment, but not by R171E. PCR array analysis detected altered expression of a group of shared 40 apoptotic genes in monocytes after treatment with each active protein, but not R171E. Interference with inflammatory cell responses, through highly divergent inflammatory response pathways, produces similar reductions in monocyte invasion, arterial dilatation, and plaque growth potentially through modified expression of apoptotic genes.

Myxomavirus-derived serpin prolongs survival and reduces inflammation and hemorrhage in an unrelated lethal mouse viral infection

Lethal viral infections produce widespread inflammation with vascular leak, clotting, and bleeding (disseminated intravascular coagulation [DIC]), organ failure, and high mortality. Serine proteases in clot-forming (thrombotic) and clot-dissolving (thrombolytic) cascades are activated by an inflammatory cytokine storm and also can induce systemic inflammation with loss of normal serine protease inhibitor (serpin) regulation. Myxomavirus secretes a potent anti-inflammatory serpin, Serp-1, that inhibits clotting factor X (fX) and thrombolytic tissue- and urokinase-type plasminogen activators (tPA and uPA) with anti-inflammatory activity in multiple animal models. Purified serpin significantly improved survival in a murine gammaherpesvirus 68 (MHV68) infection in gamma interferon receptor (IFN-γR) knockout mice, a model for lethal inflammatory vasculitis. Treatment of MHV68-infected mice with neuroserpin, a mammalian serpin that inhibits only tPA and uPA, was ineffective. Serp-1 reduced virus load, lung hemorrhage, and aortic, lung, and colon inflammation in MHV68-infected mice and also reduced virus load. Neuroserpin suppressed a wide range of immune spleen cell responses after MHV68 infection, while Serp-1 selectively increased CD11c(+) splenocytes (macrophage and dendritic cells) and reduced CD11b(+) tissue macrophages. Serp-1 altered gene expression for coagulation and inflammatory responses, whereas neuroserpin did not. Serp-1 treatment was assessed in a second viral infection, mouse-adapted Zaire ebolavirus in wild-type BALB/c mice, with improved survival and reduced tissue necrosis. In summary, treatment with this unique myxomavirus-derived serpin suppresses systemic serine protease and innate immune responses caused by unrelated lethal viral infections (both RNA and DNA viruses), providing a potential new therapeutic approach for treatment of lethal viral sepsis.

Prevention of chronic renal allograft rejection by soluble CD83

BACKGROUND

Recombinant human soluble CD83 had previously exhibited significant immunosuppressive properties that involved interference with dendritic cell maturation in both mouse and humans, inhibition of autoimmunity in mice, and induction of antigen-specific mouse cardiac allograft tolerance when used in combination with other immunosuppressive drugs. Our current research focus turned to examining the effects of peritransplant soluble CD83 (sCD83) administration on prevention of chronic renal allograft rejection.

METHODS

Fisher344-to-Lewis orthotopic rat renal transplants were performed with sequential recipient killing on postoperative days (PODs) 2, 14, and 140 to examine both the acute and chronic effects of peritransplant sCD83 treatment in rat recipients.

RESULTS

Recipients treated with sCD83 exhibited a marked decrease in IgM and IgG deposition in the graft and antidonor antibody levels in the circulation, as early as POD14 and persisting until POD140. sCD83 treatment also reduced the infiltration of T cells and monocytes into the graft tissue and inhibited intragraft expression of MyD88 and inflammatory cytokine levels during the observation period. sCD83-treated grafts demonstrated normal histology beyond POD140, including dramatic reductions in tubular atrophy and interstitial fibrosis compared with untreated recipients.

CONCLUSION

We have demonstrated that peritransplant treatment with recombinant sCD83 attenuates both innate and adaptive immune responses and leads to prevention of chronic rejection in a rat renal transplant model. Because sCD83 is of human origin, the therapeutic approach used in our rodent transplant model holds significant promise for clinical transplantation.

Plasma granzyme B as a predicting factor of coronary artery disease--clinical significance in patients with chronic renal failure

OBJECTIVES

To elucidate the role of granzyme B in coronary artery disease (CAD) in patients with chronic kidney disease (CKD). We hypothesized that granzyme B plays an important role in the formation of coronary artery lesions in patients with CKD.

PATIENTS AND METHODS

We studied 141 patients (116 men and 25 women; mean age, 64.2±9.6 years) and 16 control subjects. Diagnosis of CAD was confirmed by selective coronary angiography. CKD was defined as a sustained decrease in the estimated glomerular filtration (eGFR) rate less than 60 mL/min/1.73 m(2) over 3 months. We assigned patients to three groups: CAD without CKD (CAD group, n=46), CKD without CAD (CKD group, n=18), and CAD with CKD (CAD/CKD group, n=77). Plasma granzyme B was measured by enzyme-linked immunosorbent assay. Factors contributing to the severity of CAD were analyzed by multiple regression analysis in patients with CAD.

RESULTS

Plasma levels of high-sensitivity CRP (hs-CRP) and granzyme B in the CAD/CKD group were significantly higher than in other groups. A significant positive correlation was observed between plasma hs-CRP and granzyme B levels. A significant negative correlation was observed between eGFR and granzyme B levels. Multiple regression analysis revealed that granzyme B and hs-CRP levels were independent predicting variables of the number of stenoses in major coronary arteries.

CONCLUSIONS

These results indicate that granzyme B might be a novel risk factor for the formation of coronary atherosclerosis by inducing apoptosis of vascular tissues in patients with CKD.

Aligning antimicrobial drug discovery with complex and redundant host-pathogen interactions

Drug-resistant microorganisms pose an enormous threat to public health. Here we provide examples of experimental approaches that offer novel ways to think about drug development considering the complexity inherent to host-pathogen interactions. Emergent themes include (1) targeting pathogenicity rather than microbial growth, (2) targeting the host or host-pathogen interface rather than the pathogen, (3) facilitating pathogen-specific immune responses, and (4) utilizing systems-based approaches to identify new drug targets and validate drug efficacy. We posit that together these approaches may allow identification of drugs that disrupt pathogenesis and allow the immune system time to protect, but do not easily engender resistance.

The serpin saga; development of a new class of virus derived anti-inflammatory protein immunotherapeutics

Serine proteinase inhibitors, also called serpins, are an ancient grouping of proteins found in primitive organisms from bacteria, protozoa and horseshoe crabs and thus likely present at the time of the dinosaurs, up to all mammals living today. The innate or inflammatory immune system is also an ancient metazoan regulatory system, providing the first line of defense against infection or injury. The innate inflammatory defense response evolved long before acquired, antibody dependent immunity. Viruses have developed highly effective stratagems that undermine and block a wide variety of host inflammatory and immune responses. Some of the most potent of these immune modifying strategies utilize serpins that have also been developed over millions of years, including the hijacking by some viruses for defense against host immune attacks. Serpins represent up to 2-10 percent of circulating plasma proteins, regulating actions as wide ranging as thrombosis, inflammation, blood pressure control and even hormone transport. Targeting serpin-regulated immune or inflammatory pathways makes evolutionary sense for viral defense and many of these virus-derived inhibitory proteins have proven to be highly effective, working at very low concentrations--even down to the femptomolar to picomolar range. We are studying these viral anti-inflammatory proteins as a new class of immunomodulatory therapeutic agents derived from their native viral source. One such viral serpin, Serp-1 is now in clinical trial (conducted by VIRON Therapeutics, Inc.) for acute unstable coronary syndromes (unstable angina and small heart attacks), representing a 'first in class' therapeutic study. Several other viral serpins are also currently under investigation as anti-inflammatory or anti-immune therapeutics. This chapter describes these original studies and the ongoing analysis of viral serpins as a new class of virus-derived immunotherapeutic.

Myxoma viral serpin, Serp-1, inhibits human monocyte adhesion through regulation of actin-binding protein filamin B

Serp-1 is a secreted myxoma viral serine protease inhibitor (serpin) with proven, highly effective, anti-inflammatory defensive activity during host cell infection, as well as potent immunomodulatory activity in a wide range of animal disease models. Serp-1 binds urokinase-type plasminogen activator (uPA) and the tissue-type PA, plasmin, and factor Xa, requiring uPA receptor (uPAR) for anti-inflammatory activity. To define Serp-1-mediated effects on inflammatory cell activation, we examined the association of Serp-1 with monocytes and T cells, effects on cellular migration, and the role of uPAR-linked integrins and actin-binding proteins in Serp-1 cellular responses. Our results show that Serp-1 associates directly with activated monocytes and T lymphocytes, in part through interaction with uPAR (P<0.001). Serp-1, but not mammalian serpin PA inhibitor-1 (PAI-1), attenuated cellular adhesion to the extracellular matrix. Serp-1 and PAI-1 reduced human monocyte and T cell adhesion (P<0.001) and migration across endothelial monolayers in vitro (P<0.001) and into mouse ascites in vivo (P<0.001). Serp-1 and an inactive Serp-1 mutant Serp-1(SAA) bound equally to human monocytes and T cells, but a highly proinflammatory mutant, Serp-1(Ala(6)), bound less well to monocytes. Serp-1 treatment of monocytes increased expression of filamin B actin-binding protein and reduced CD18 (beta-integrin) expression (P<0.001) in a uPAR-dependent response. Filamin colocalized and co-immunoprecipitated with uPAR, and short interference RNA knock-down of filamin blocked Serp-1 inhibition of monocyte adhesion. We report here that the highly potent, anti-inflammatory activity of Serp-1 is mediated through modification of uPAR-linked beta-integrin and filamin in monocytes, identifying this interaction as a central regulatory axis for inflammation.

Myxoma virus and oncolytic virotherapy: a new biologic weapon in the war against cancer

Oncolytic virotherapy is an innovative alternative to more conventional cancer therapies. The ability of some viruses to specifically target and kill malignant cancerous cells while leaving normal tissue unscathed has opened a large repertoire of new and selective cancer killing therapeutic candidates. Poxviruses, such as vaccinia virus, have a long history of use in humans as live vaccines and have more recently been studied as potential platforms for delivery of immunotherapeutics and attenuated variants of vaccinia have been explored as oncolytic candidates. In contrast, the poxvirus myxoma virus is a novel oncolytic candidate that has no history of use in humans directly, as it has a distinct and absolute host species tropism to lagomorphs (rabbits). Myxoma virus has been recently shown to be able to also selectively infect and kill human tumor cells, a unique tropism that is linked to dysregulated intracellular signalling pathways found in the majority of human cancers. This review outlines the existing knowledge on the tropism of myxoma virus for human cancer cells, as well as preclinical data exhibiting its ability to infect and clear tumors in animal models of cancer. This is an exciting new therapeutic option for treating cancer, and myxoma virus joins a growing group of oncolytic virus candidates that are being developed as a new class of cancer therapies in man.

Adeno-associated viral vector-mediated interleukin-10 prolongs allograft survival in a rat kidney transplantation model

Interleukin-10 (IL-10) is a pleiotropic cytokine that plays a pivotal role in the regulation of immune responses. Hence, we evaluated the effects of a recombinant adeno-associated viral vector 1 (rAAV1) encoding rat IL-10 (rAAV1-IL-10) in a rat model of kidney allograft rejection. Dark Agouti rat kidneys were transplanted into Wistar-Furth (WF) rats 8 weeks following a single intramuscular administration of either rAAV1-IL-10 or rAAV1-green fluorescence protein (GFP). Isografts (WF-WF) served as an additional experimental control. Both allograft and isograft recipients received daily cyclosporine (10 mg/kg) for 14 days after transplantation. Serum IL-10 levels increased at 8, 12 and 16 weeks following vector administration in rAAV1-IL-10-treated animals, but not in rAAV1-GFP and isograft groups. rAAV1-IL-10 treatment resulted in lower BUN and creatinine levels (p<0.001), as well as increased allograft survival rates from 22% to 90%. Allograft histological abnormalities were significantly attenuated in the rAAV1-IL-10-treated rats compared with those of rAAV1-GFP controls. Serum levels of proinflammatory cytokines such as growth-related oncogene were also significantly higher in the rAAV1-GFP group than in the rAAV1-IL-10 group. These data suggest delivery of IL-10 using a rAAV1 vector improves renal function and prolongs graft survival in a rat model of kidney transplant rejection.

Immunopathogenesis of poxvirus infections: forecasting the impending storm

Variola virus, the causative agent of smallpox, is a member of the poxvirus family and one of the most virulent human pathogens known. Although smallpox was eradicated almost 30 years ago, it is not understood why the mortality rates associated with the disease were high, why some patients recovered, and what constitutes an effective host response against infection. As variola virus infects only humans, our current understanding of poxvirus infections comes largely from historical clinical data from smallpox patients and from animal studies using closely related viruses such as ectromelia, myxoma and monkeypox. The outcome of an infection is determined by a complex interaction between the type of immune response mounted by the host and by evasion mechanisms that the virus has evolved to subvert it. Disease pathogenesis is also a function of both host and viral factors. Poxviruses are not only cytopathic, causing host tissue damage, but also encode an array of immunomodulatory molecules that affect the severity of disease. The ability of the host to control virus replication is therefore critical in limiting tissue damage. However, in addition to targeting virus, the immune response can inadvertently damage the host to such a degree that it causes illness and even death. There is growing evidence that many of the symptoms associated with serious poxvirus infections are a result of a 'cytokine storm' or sepsis and that this may be the underlying cause of pathology.