Nasal cardiac myosin peptide treatment and OX40 blockade protect mice from acute and chronic virally-induced myocarditis

Regulatory T Cells in Pathological Cardiac Hypertrophy: Mechanisms and Therapeutic Potential

BACKGROUND

Pathological cardiac hypertrophy is linked to immune-inflammatory injury, and regulatory T cells (Tregs) play a crucial role in suppressing immune-inflammatory responses. However, the precise role of Tregs in pathological cardiac hypertrophy remains unclear.

OBJECTIVE

To summarize the current knowledge on the role and mechanisms of Tregs in pathological cardiac hypertrophy and explore their perspectives and challenges as a new therapeutic approach.

RESULTS

Treg cells may play an important protective role in pressure overload (hypertension, aortic stenosis), myocardial infarction, metabolic disorders (diabetes, obesity), acute myocarditis, cardiomyopathy (hypertrophic cardiomyopathy, storage diseases), and chronic obstructive pulmonary disease-related pathological cardiac hypertrophy. Although some challenges remain, the safety and efficacy of Treg-based therapies have been confirmed in some clinical trials, and engineered antigen-specific Treg cells may have better clinical application prospects due to stronger immunosuppressive function and stability.

CONCLUSION

Targeting the immune-inflammatory response via Treg-based therapies might provide a promising and novel future approach to the prevention and treatment of pathological cardiac hypertrophy.

Role of mitochondrial metabolic disorder and immune infiltration in diabetic cardiomyopathy: new insights from bioinformatics analysis

BACKGROUND

Diabetic cardiomyopathy (DCM) is one of the common cardiovascular complications of diabetes and a leading cause of death in diabetic patients. Mitochondrial metabolism and immune-inflammation are key for DCM pathogenesis, but their crosstalk in DCM remains an open issue. This study explored the separate roles of mitochondrial metabolism and immune microenvironment and their crosstalk in DCM with bioinformatics.

METHODS

DCM chip data (GSE4745, GSE5606, and GSE6880) were obtained from NCBI GEO, while mitochondrial gene data were downloaded from MitoCarta3.0 database. Differentially expressed genes (DEGs) were screened by GEO2R and processed for GSEA, GO and KEGG pathway analyses. Mitochondria-related DEGs (MitoDEGs) were obtained. A PPI network was constructed, and the hub MitoDEGs closely linked to DCM or heart failure were identified with CytoHubba, MCODE and CTD scores. Transcription factors and target miRNAs of the hub MitoDEGs were predicted with Cytoscape and miRWalk database, respectively, and a regulatory network was established. The immune infiltration pattern in DCM was analyzed with ImmuCellAI, while the relationship between MitoDEGs and immune infiltration abundance was investigated using Spearman method. A rat model of DCM was established to validate the expression of hub MitoDEGs and their relationship with cardiac function.

RESULTS

MitoDEGs in DCM were significantly enriched in pathways involved in mitochondrial metabolism, immunoregulation, and collagen synthesis. Nine hub MitoDEGs closely linked to DCM or heart failure were obtained. Immune analysis revealed significantly increased infiltration of B cells while decreased infiltration of DCs in immune microenvironment of DCM. Spearman analysis demonstrated that the hub MitoDEGs were positively associated with the infiltration of pro-inflammatory immune cells, but negatively associated with the infiltration of anti-inflammatory or regulatory immune cells. In the animal experiment, 4 hub MitoDEGs (Pdk4, Hmgcs2, Decr1, and Ivd) showed an expression trend consistent with bioinformatics analysis result. Additionally, the up-regulation of Pdk4, Hmgcs2, Decr1 and the down-regulation of Ivd were distinctly linked to reduced cardiac function.

CONCLUSIONS

This study unraveled the interaction between mitochondrial metabolism and immune microenvironment in DCM, providing new insights into the research on potential pathogenesis of DCM and the exploration of novel targets for medical interventions.

Targeting regulatory T cells for cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. The CVDs are accompanied by inflammatory progression, resulting in innate and adaptive immune responses. Regulatory T cells (Tregs) have an immunosuppressive function and are one of the subsets of CD4⁺T cells that play a crucial role in inflammatory diseases. Whether using Tregs as a biomarker for CVDs or targeting Tregs to exert cardioprotective functions by regulating immune balance, suppressing inflammation, suppressing cardiac and vascular remodeling, mediating immune tolerance, and promoting cardiac regeneration in the treatment of CVDs has become an emerging research focus. However, Tregs have plasticity, and this plastic Tregs lose immunosuppressive function and produce toxic effects on target organs in some diseases. This review aims to provide an overview of Tregs' role and related mechanisms in CVDs, and reports on the research of plasticity Tregs in CVDs, to lay a foundation for further studies targeting Tregs in the prevention and treatment of CVDs.

Natural Products as a Paradigm for the Treatment of Coxsackievirus - induced Myocarditis

Coxsackievirus B3 (CVB3), a member of the Picornaviridae family, is considered to be one of the most important infectious agents to cause virus-induced myocarditis. Despite improvements in studying viral pathology, structure and molecular biology, as well as diagnosis of this disease, there is still no virus-specific drug in clinical use. Structural and nonstructural proteins produced during the coxsackievirus life cycle have been identified as potential targets for blocking viral replication at the step of attachment, entry, uncoating, RNA and protein synthesis by synthetic or natural compounds. Moreover, WIN (for Winthrop) compounds and application of nucleic-acid based strategies were shown to target viral capsid, entry and viral proteases, but have not reached to the clinical trials as a successful antiviral agent. There is an urgent need for diverse molecular libraries for phenotype-selective and high-throughput screening.

T cell co-stimulation and co-inhibition in cardiovascular disease: a double-edged sword

The role of inflammation in cardiovascular disease (CVD) is now widely accepted. Immune cells, including T cells, are influenced by inflammatory signals and contribute to the onset and progression of CVD. T cell activation is modulated by T cell co-stimulation and co-inhibition pathways. Immune checkpoint inhibitors (ICIs) targeting T cell inhibition pathways have revolutionized cancer treatment and improved survival in patients with cancer. However, ICIs might induce cardiovascular toxicity via T cell re-invigoration. With the rising use of ICIs for cancer treatment, a timely overview of the role of T cell co-stimulation and inhibition molecules in CVD is desirable. In this Review, the importance of these molecules in the pathogenesis of CVD is highlighted in preclinical studies on models of CVD such as vein graft disease, myocarditis, graft arterial disease, post-ischaemic neovascularization and atherosclerosis. This Review also discusses the therapeutic potential of targeting T cell co-stimulation and inhibition pathways to treat CVD, as well as the possible cardiovascular benefits and adverse events after treatment. Finally, the Review emphasizes that patients with cancer who are treated with ICIs should be monitored for CVD given the reported association between the use of ICIs and the risk of cardiovascular toxicity.

Myocarditis in Humans and in Experimental Animal Models

Myocarditis is defined as an inflammation of the cardiac muscle. In humans, various infectious and non-infectious triggers induce myocarditis with a broad spectrum of histological presentations and clinical symptoms of the disease. Myocarditis often resolves spontaneously, but some patients develop heart failure and require organ transplantation. The need to understand cellular and molecular mechanisms of inflammatory heart diseases led to the development of mouse models for experimental myocarditis. It has been shown that pathogenic agents inducing myocarditis in humans can often trigger the disease in mice. Due to multiple etiologies of inflammatory heart diseases in humans, a number of different experimental approaches have been developed to induce myocarditis in mice. Accordingly, experimental myocarditis in mice can be induced by infection with cardiotropic agents, such as coxsackievirus B3 and protozoan parasite Trypanosoma cruzi or by activating autoimmune responses against heart-specific antigens. In certain models, myocarditis is followed by the phenotype of dilated cardiomyopathy and the end stage of heart failure. This review describes the most commonly used mouse models of experimental myocarditis with a focus on the role of the innate and adaptive immune systems in induction and progression of the disease. The review discusses also advantages and limitations of individual mouse models in the context of the clinical manifestation and the course of the disease in humans. Finally, animal-free alternatives in myocarditis research are outlined.

Comparative immunologic characterization of autoimmune giant cell myocarditis with ipilimumab

Autoimmune myocarditis is a rare but often fatal toxicity of checkpoint inhibitor immunotherapy. To improve the understanding of this complication, we performed immune profiling on post-mortem tissue from a patient with metastatic melanoma who had steroid-responsive hepatitis, steroid-refractory myocarditis, and shrinking lung metastases after ipilimumab treatment. Histological analysis of heart tissue demonstrated findings consistent with giant cell myocarditis (GCM). The immune infiltrate in the heart was largely comprised of CD4+ T cells, whereas the liver had very few T cells, and CD8+ T cells were predominant in the responding lung metastases. TCR sequencing identified high T cell clonality in the lung metastases. The TCR repertoire showed low clonality in the heart and minimal overlap with the liver (1.2%), but some overlap with lung metastases (9.9%). Transcriptional profiling identified several potential mediators of increased inflammation in the heart. These findings provide new insights into the pathogenesis of autoimmune myocarditis with ipilimumab.

Berberine Restricts Coxsackievirus B Type 3 Replication via Inhibition of c-Jun N-Terminal Kinase (JNK) and p38 MAPK Activation In Vitro

Background

At present, the treatment of coxsackievirus-induced myocarditis remains difficult. Berberine (BBR), an isoquinoline alkaloid isolated from traditional medicine herbs, exhibits significant anti-viral efficacy against various viruses. However, the underlying mechanism by which BBR controls CVB3 infection has not yet been reported. The purpose of this study was to investigate the anti-viral efficacy of BBR against CVB3 infection and its mechanism.

Material/Methods

In our experiments, the protein levels of VP1 and MAPKs signal pathway were measured by Western blot. The mRNA level of VP1 was measured by RT-PCR. The virus titers were determined by TCID₅₀ assay.

Results

We found that BBR treatment significantly decreased CVB3 replication in HeLa cells. In addition, the BBR treatment reduced the phosphorylation levels of JNK and p38 MAPK upon CVB3 infection in both HeLa cells and primary rat myocardial cells.

Conclusions

Taken together, these results suggest that BBR inhibits CVB3 replication through the suppression of JNK and p38 MAPK activation, shedding new light on the investigation of therapeutic strategies against CVB3-induced viral myocarditis.

T-cell immunity in myocardial inflammation: pathogenic role and therapeutic manipulation

T-cell-mediated immunity has been linked not only to a variety of heart diseases, including classic inflammatory diseases such as myocarditis and post-myocardial infarction (Dressler's) syndrome, but also to conditions without an obvious inflammatory component such as idiopathic dilated cardiomyopathy and hypertensive cardiomyopathy. It has been recently proposed that in all these conditions, the heart becomes the focus of T-cell-mediated autoimmune inflammation following ischaemic or infectious injury. For example, in acute myocarditis, an inflammatory disease of heart muscle, T-cell responses are thought to arise as a consequence of a viral infection. In a number of patients, persistent T-cell-mediated responses in acute viral myocarditis can lead to autoimmunity and chronic cardiac inflammation resulting in dilated cardiomyopathy. In spite of the major progress made in understanding the mechanisms of pathogenic T-cell responses, effective and safe therapeutic targeting of the immune system in chronic inflammatory diseases of the heart has not yet been developed due to the lack of specific diagnostic and prognostic biomarkers at an early stage. This has also prevented the identification of targets for patient-tailored immunomodulatory therapies that are both disease- and organ-selective. In this review, we discuss current knowledge of the development and functional characteristics of pathogenic T-cell-mediated immune responses in the heart, and, in particular, in myocarditis, as well as recent advances in experimental models which have the potential to translate into heart-selective immunomodulation.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

The CXCL10/CXCR3 Axis and Cardiac Inflammation: Implications for Immunotherapy to Treat Infectious and Noninfectious Diseases of the Heart

Accumulating evidence reveals involvement of T lymphocytes and adaptive immunity in the chronic inflammation associated with infectious and noninfectious diseases of the heart, including coronary artery disease, Kawasaki disease, myocarditis, dilated cardiomyopathies, Chagas, hypertensive left ventricular (LV) hypertrophy, and nonischemic heart failure. Chemokine CXCL10 is elevated in cardiovascular diseases, along with increased cardiac infiltration of proinflammatory Th1 and cytotoxic T cells. CXCL10 is a chemoattractant for these T cells and polarizing factor for the proinflammatory phenotype. Thus, targeting the CXCL10 receptor CXCR3 is a promising therapeutic approach to treating cardiac inflammation. Due to biased signaling CXCR3 also couples to anti-inflammatory signaling and immunosuppressive regulatory T cell formation when activated by CXCL11. Numbers and functionality of regulatory T cells are reduced in patients with cardiac inflammation, supporting the utility of biased agonists or biologicals to simultaneously block the pro-inflammatory and activate the anti-inflammatory actions of CXCR3. Other immunotherapy strategies to boost regulatory T cell actions include intravenous immunoglobulin (IVIG) therapy, adoptive transfer, immunoadsorption, and low-dose interleukin-2/interleukin-2 antibody complexes. Pharmacological approaches include sphingosine 1-phosphate receptor 1 agonists and vitamin D supplementation. A combined strategy of switching CXCR3 signaling from pro- to anti-inflammatory and improving Treg functionality is predicted to synergistically lessen adverse cardiac remodeling.

Intricacies of cardiac damage in coxsackievirus B3 infection: implications for therapy

Heart disease is the leading cause of death in humans, and myocarditis is one predominant cause of heart failure in young adults. Patients affected with myocarditis can develop dilated cardiomyopathy (DCM), a common reason for heart transplantation, which to date is the only viable option for combatting DCM. Myocarditis/DCM patients show antibodies to coxsackievirus B (CVB)3 and cardiac antigens, suggesting a role for CVB-mediated autoimmunity in the disease pathogenesis; however, a direct causal link remains to be determined clinically. Experimentally, myocarditis can be induced in susceptible strains of mice using the human isolates of CVB3, and the disease pathogenesis of postinfectious myocarditis resembles that of human disease, making the observations made in animals relevant to humans. In this review, we discuss the complex nature of CVB3-induced myocarditis as it relates to the damage caused by both the virus and the host's response to infection. Based on recent data we obtained in the mouse model of CVB3 infection, we provide evidence to suggest that CVB3 infection accompanies the generation of cardiac myosin-specific CD4 T cells that can transfer the disease to naïve recipients. The therapeutic implications of these observations are also discussed.

Learning from myocarditis: mimicry, chaos and black holes

Autoimmune myocarditis and its sequel, dilated cardiomyopathy, are major causes of heart failure, especially in children and young adults. We have developed animal models to investigate their pathogenesis by infecting genetically susceptible mice with coxsackievirus B3 or by immunizing them with cardiac myosin or its immunodominant peptide. A number of valuable lessons have emerged from our study of this paradigm of an infection-induced autoimmune disease. We understand more clearly how natural autoimmunity, as an important component of normal physiology, must be recalibrated regularly due to changes caused by infection or other internal and external stimuli. A new normal homeostatic platform will be established based on its evolutionary fitness. A loss of homeostasis with out-of-control normal autoimmunity leads to autoimmune disease. It is signified early on by a spread of an adaptive autoimmune response to novel epitopes and neighboring antigens. The progression from infection to normal, well-balanced autoimmunity to autoimmune disease and on to irreversible damage is a complex, step-wise process. Yet, chaos theory provides hope that the pattern is potentially predictable. Infection-induced autoimmune disease represents a sequence of events heading for a train wreck at the end of the line. Our aim in autoimmune disease research must be to stop the train before this happens.

The whole genome sequence of coxsackievirus B3 MKP strain leading to myocarditis and its molecular phylogenetic analysis

BACKGROUND

In recent years, the reported infection cases by coxsackievirus (CV) have been on the rise. In order to reveal the relationship between the nucleotide and amino acid sequences and the viral virulence of the CVB3/MKP strain causing myocarditis, we initially confirmed the virulence of the strain in myocardial tissue and then carried out the whole genome sequencing of CVB3/MKP strain and performed a phylogenetic analysis among different CVB3 strains.

METHODS

CVB3/MKP infected mouse model was established to check lesions of myocardial tissue in mice using immunohistochemical detection at different periods. RT-PCR analysis was used to amplify seven fragments covering the whole viral sequence and comparable analysis was performed.

RESULTS

The immunohistochemical results showed that particles of CVB3/MKP virus persisted in the cardiac tissue and caused severe pathology. The length of whole genome sequence of CVB3/MKP strain was 7400 bp. CVB3/MKP had 99.7% and 99.6% homology in nucleotide sequence with CVB3/28 and non-virulent CVB3/0, respectively. The former can induce pancreatitis and myocarditis. The nucleotide sequence in the 5'untranslated region of CVB3/MKP strain shared 99.6% and 99.5% homology with CVB3/20 and CVB3/Nancy, respectively.

CONCLUSION

We confirmed in our animal experiments that CVB3/MKP had cardiotoxicity. CVB3/MKP, CVB3/28, and CVB3/0 may share evolutionary convergence and the 5'untranslated region (5'UTR) may be associated with virulence phenotype. Our findings will provide a basis for identifying the genomic determinant of viral virulence of CVB3/MKP strain and phylogenetic relationship among different CVB3 strains.

Autoimmunity in viral myocarditis

PURPOSE OF REVIEW

To review how autoimmunity is induced in viral myocarditis.

RECENT FINDINGS

Clinical and experimental myocarditis follows microbial infections, but autoimmunity to cardiac antigens leads to heart failure since infected myocytes are sparse and virus clearance is rapid. In mice, CD4+ T cells specific for cardiac alpha myosin heavy chain (αMYHC) cause myocarditis and mice tolerized to αMYHC are protected from virus challenge proving pathogenesis depends upon autoimmunity. Most importantly, multiple microbes share the same mimicking epitope with αMYHC. Serial infections with very different microbes could result in memory responses to the shared epitope leading to aggressive and severe heart failure. A similar phenomenon may explain autoimmune diseases with suspected infectious causes, where specific pathogens have not been identified. Production of the relevant cardiac epitope for antigen presentation requires more than myosin release from dead myocytes. Otherwise, myocarditis would commonly follow myocardial infarcts. The inherent nature of the innate immune response associated with viral infections in the heart is crucial to cardiac epitope expression.

SUMMARY

Antigenic mimicry between microbes and cardiac proteins causes autoimmunity in myocarditis. Characteristics of innate immunity associated with cardiac infection determine relevant epitope expression (cryptic epitopes).

OX40L blockade is therapeutic in arthritis, despite promoting osteoclastogenesis

An immune response is essential for protection against infection, but, in many individuals, aberrant responses against self tissues cause autoimmune diseases such as rheumatoid arthritis (RA). How to diminish the autoimmune response while not augmenting infectious risk is a challenge. Modern targeted therapies such as anti-TNF or anti-CD20 antibodies ameliorate disease, but at the cost of some increase in infectious risk. Approaches that might specifically reduce autoimmunity and tissue damage without infectious risk would be important. Here we describe that TNF superfamily member OX40 ligand (OX40L; CD252), which is expressed predominantly on antigen-presenting cells, and its receptor OX40 (on activated T cells), are restricted to the inflamed joint in arthritis in mice with collagen-induced arthritis and humans with RA. Blockade of this pathway in arthritic mice reduced inflammation and restored tissue integrity predominantly by inhibiting inflammatory cytokine production by OX40L-expressing macrophages. Furthermore, we identify a previously unknown role for OX40L in steady-state bone homeostasis. This work shows that more targeted approaches may augment the "therapeutic window" and increase the benefit/risk in RA, and possibly other autoimmune diseases, and are thus worth testing in humans.

Control of inflammatory heart disease by CD4+ T cells

This review focuses on autoimmune myocarditis and its sequela, inflammatory dilated cardiomyopathy (DCMI), and the inflammatory and immune mechanisms underlying the pathogenesis of these diseases. Several mouse models of myocarditis and DCMI have improved our knowledge of the pathogenesis of these diseases, informing more general problems of cardiac remodeling and heart failure. CD4(+) T cells are critical in driving the pathogenesis of myocarditis. We discuss in detail the role of T helper cell subtypes in the pathogenesis of myocarditis, the biology of T cell-derived effector cytokines, and the participation of other leukocytic effectors in mediating disease pathophysiology. We discuss interactions between these subsets in both suppressive and collaborative fashions. These findings indicate that cardiac inflammatory disease, and autoimmunity in general, may be more diverse in divergent effector mechanisms than has previously been appreciated.

The autoimmune side of heart and lung diseases

The elevated cardiovascular morbidity in rheumatoid arthritis, systemic lupus erythematosus, and the antiphospholipid syndrome is well known, as well as the pulmonary involvement observed in these conditions and to a major extent in systemic sclerosis. These manifestations constitute a major challenge for clinicians involved in patient management. Moreover, several issues regarding the link between autoimmune rheumatic diseases and cardio pulmonary morbidity remain largely enigmatic. The mechanistic role of certain autoantibodies frequently observed in association with heart and lung diseases or the pathogenetic link between chronic inflammation and the pathways leading to atherosclerosis or pulmonary vascular changes are yet to be elucidated. As such, these questions as well as treatment strategies are of common interest to rheumatologists, immunologist, pulmonologists, and cardiologists and thus call for an interdisciplinary approach. This paradigm has been well established for rare conditions such as the Churg-Strauss syndrome. Nowadays, it seems that this approach should be expanded to encompass more common conditions such as coronary heart disease, pulmonary arterial hypertension or dilated cardiomyopathy. The present issue of Clinical Reviews in Allergy and Immunology addresses the new knowledge and concepts of autoimmune-related cardiopulmonary diseases. The issue derives from the 2010 International Autoimmunity Meeting held in Ljubljana, Slovenia and is thus timely and dedicated to the latest developments in this new multidisciplinary field.

The heart of the matter: protection of the myocardium from T cells

Myocardial inflammation and damage can lead to lethal acute or chronic cardiac failure. A variety of regulatory mechanisms limit the magnitude and duration of T cell responses in the heart. Insights into these regulatory mechanisms have come from studies of specific deficiencies in central or peripheral T cell tolerance which cause or enhance the severity of myocarditis. Under non-inflammatory conditions, constitutive DC presentation of cardiac peptides to naïve T cells in cardiac draining lymph nodes tolerizes recirculating naïve T cells specific for these antigens. Cardiac antigen-specific naïve T cells, especially those specific of α-myosin heavy chain peptides, become activated and differentiate into expanded clones of effector T cells under various conditions, such as cardiac infection and/or genetic variations in peripheral tolerance. The pathology that these effector cells cause in the myocardium is limited by PD-L1 expressed on myocardial cells in response to inflammatory cytokines, and by CTLA-4 dependent mechanisms. The PD-1:PD-L1 pathway works together with other control mechanisms to keep the heart safe from T cells, and combined impairment of this pathway along with other regulatory mechanisms synergize to cause myocarditis. T cell derived IFNγ contributes to the inflammatory damage to the heart in autoimmune myocarditis, but it also engages regulatory mechanisms that limit disease, including upregulation of PD-L1, and differentiation of TNF and iNOS expressing DCs from monocytes. iNOS derived from these DCs and other IFNγ stimulated cells inhibits expansion of T cells that cause myocarditis. Regulatory T cells also appear to be critical for suppression of effector T cells specific for myocardial antigens.

Autoimmunity in 2011

The mechanisms leading to the onset and perpetuation of systemic and tissue-specific autoimmune diseases are complex, and numerous hypotheses have been proposed or confirmed over the past 12 months. It is particularly of note that the number of articles published during 2011 in the major immunology and autoimmunity journals increased by 3 % compared to the previous year. The present article is dedicated to a brief review of the reported data and, albeit not comprehensive of all articles, is aimed at identifying common and future themes. First, clinical researchers were particularly dedicated to defining refractory forms of diseases and to discuss the use and switch of therapeutic monoclonal antibodies in everyday practice. Second, following the plethora of genome-wide association studies reported in most multifactorial diseases, it became clear that genomics cannot fully explain the individual susceptibility and additional environmental or epigenetic factors are necessary. Both these components were widely investigated, both in organ-specific (i.e., type 1 diabetes) and systemic (i.e., systemic lupus erythematosus) diseases. Third, a large number of 2011 works published in the autoimmunity area are dedicated to dissect pathogenetic mechanisms of tolerance breakdown in general or in specific conditions. While our understanding of T regulatory and Th17 cells has significantly increased in 2011, it is of note that most of the proposed lines of evidence identify potential targets for future treatments and should not be overlooked.

OX40 facilitates control of a persistent virus infection

During acute viral infections, clearance of the pathogen is followed by the contraction of the anti-viral T cell compartment. In contrast, T cell responses need to be maintained over a longer period of time during chronic viral infections in order to control viral replication and to avoid viral spreading. Much is known about inhibitory signals such as through PD-1 that limit T cell activity during chronic viral infection, but little is known about the stimulatory signals that allow maintenance of anti-viral T cells. Here, we show that the co-stimulatory molecule OX40 (CD134) is critically required in the context of persistent LCMV clone 13 infection. Anti-viral T cells express high levels of OX40 in the presence of their cognate antigen and T cells lacking the OX40 receptor fail to accumulate sufficiently. Moreover, the emergence of T cell dependent germinal center responses and LCMV-specific antibodies are severely impaired. Consequently, OX40-deficient mice fail to control LCMV clone 13 infection over time, highlighting the importance of this signaling pathway during persistent viral infection.

A robust T cell response is the hallmark of an effective immune response to a variety of invading viruses. In many acute infections, the clearance of the viral pathogen is associated with a short and vigorous T cell response followed by development of pathogen-specific immune memory. However, some viruses can establish persistent infection in their respective host, during which an ongoing T cell response is required in order to prevent overwhelming viral replication. Little is known about the factors that sustain the T cell response in the persistent phase of a viral infection. In this report, we demonstrate that ligation of the OX40 molecule, which is expressed on T cells targeting the virus, is critically required in order to sustain the anti-viral immune response. We show that virus-specific, OX40-deficient T cells fail to accumulate sufficiently and consequently, mice lacking the OX40 receptor are incapable of controlling viral replication. Collectively our data establish OX40 as a crucial signaling molecule during a persistent viral infection.

Coxsackievirus B3 infection leads to the generation of cardiac myosin heavy chain-α-reactive CD4 T cells in A/J mice

Enteroviruses like coxsackievirus B3 (CVB3) are common suspects in myocarditis/dilated cardiomyopathy patients. Autoimmunity has been proposed as an underlying mechanism, but direct evidence of its role is lacking. To delineate autoimmune response in CVB3 myocarditis, we used IA(k) dextramers for cardiac myosin heavy chain (Myhc)-α 334-352. We have demonstrated that myocarditis-susceptible A/J mice infected with CVB3 generate Myhc-α-reactive CD4 T cells and such a repertoire was absent in naïve mice as measured by proliferative response to Myhc-α 334-352 and IA(k) dextramer staining. We also detected Myhc-α 334-352 dextramer(+) cells in the hearts of CVB3-infected mice. The autoreactive T cell repertoire derived from infected mice contained a high frequency of interleukin-17-producing cells capable of inducing myocarditis in naïve recipients. The data suggest that CVB3, a bona fide pathogen of cardiovascular system that primarily infects the heart can lead to the secondary generation of autoreactive T cells and contribute to cardiac pathology.

Update on coxsackievirus B3 myocarditis

PURPOSE OF REVIEW

To present recent findings on the pathogenesis of coxsackievirus B3 (CVB3) myocarditis based on animal models, with a focus on the role of T helper (Th) immune responses in disease progression.

RECENT FINDINGS

Acute CVB3 myocarditis is known to be increased by Th1 immune responses, but recent findings indicate that Th1-type immunity protects against acute myocarditis by reducing viral replication and prevents the progression to chronic myocarditis and dilated cardiomyopathy (DCM) by inhibiting Th2 responses. Th2 responses reduce acute myocarditis by inhibiting Th1 responses via regulatory T cells and anti-inflammatory cytokines, but can be deleterious when they induce acute cardiac remodeling leading to chronic myocarditis/DCM. Th2-skewed immune responses allow resistant strains of mice to progress from myocarditis to DCM. In contrast, Th17 responses are elevated during acute and chronic myocarditis and have been found to contribute to cardiac remodeling and DCM.

SUMMARY

Recent data indicate that elevated Th2 and Th17 responses during acute CVB3 myocarditis are critical for the progression from myocarditis to DCM and heart failure because of their ability to induce cardiac remodeling. Th1 responses protect against CVB3 myocarditis by inhibiting Th2 responses and viral replication, but increase acute inflammation.

TNF superfamily in inflammatory disease: translating basic insights

The tumor necrosis factor (TNF) and TNF receptor superfamilies (TNFSF and TNFRSF) consist of approximately 50 membrane and soluble proteins that can modulate cellular function. Most of these molecules are expressed by or can target cells of the immune system, and they have a wide range of actions including promoting cellular differentiation, survival, and production of inflammatory cytokines and chemokines. Emerging data show that TNFSF ligand-receptor signaling pathways are active in inflammatory and autoimmune disease. Furthermore, several genetic polymorphisms in TNFSF and TNFRSF associate with susceptibility to developing disease. Here, we examine recent data regarding the potential of these molecules as targets for therapy of autoimmune and inflammatory disease.