Molecular pathology of inflammatory cardiomyopathy

Infectious factors in myocarditis: a comprehensive review of common and rare pathogens

BACKGROUND

Myocarditis is a significant health threat today, with infectious agents being the most common cause. Accurate diagnosis of the etiology of infectious myocarditis is crucial for effective treatment.

MAIN BODY

Infectious myocarditis can be caused by viruses, prokaryotes, parasites, and fungi. Viral infections are typically the primary cause. However, some rare opportunistic pathogens can also damage heart muscle cells in patients with immunodeficiencies, neoplasms and those who have undergone heart surgery.

CONCLUSIONS

This article reviews research on common and rare pathogens of infectious myocarditis, emphasizing the complexity of its etiology, with the aim of helping clinicians make an accurate diagnosis of infectious myocarditis.

Chinese Society of Cardiology guidelines on the diagnosis and treatment of adult fulminant myocarditis

Fulminant myocarditis is an acute diffuse inflammatory disease of myocardium. It is characterized by acute onset, rapid progress and high risk of death. Its pathogenesis involves excessive immune activation of the innate immune system and formation of inflammatory storm. According to China's practical experience, the adoption of the "life support-based comprehensive treatment regimen" (with mechanical circulation support and immunomodulation therapy as the core) can significantly improve the survival rate and long-term prognosis. Special emphasis is placed on very early identification,very early diagnosis,very early prediction and very early treatment.

Paradigm shift in myocarditis treatment

Although most cases of myocarditis are self-limiting with a gradual improvement in cardiac function, the involvement of myocarditis in sudden cardiac death among children and young adults remains substantial, with rates of 3-17 % and 8.6-12 %, respectively. Moreover, the risk of developing chronic dilated cardiomyopathy ranges from 21 % to 30 % in all cases confirmed by biopsy. Current therapeutic strategies for myocarditis and its complications range from standard supportive care for heart failure and arrhythmias to etiologically oriented, case-based therapeutic options. For example, immunosuppression is indicated only in certain forms of acute myocarditis with clinical or endomyocardial biopsy evidence of immune checkpoint inhibitor-induced myocarditis and autoimmune diseases, including giant cell myocarditis, eosinophilic myocarditis, vasculitis, or cardiac sarcoidosis. However, our views on myocarditis treatment have changed considerably over the past two decades, thanks to the emergence of regenerative cells/tissues as well as drug and gene delivery systems. Cell-based therapies are now growing in popularity in any field of medicine. Studies evaluating the therapeutic efficacy of different stem cells in the treatment of acute myocarditis and its chronic complications have shown that although the experimental characteristics varied from study to study, in general, these strategies reduced inflammation and myocardial fibrosis while preventing myocarditis-induced systolic dysfunction and adverse remodeling in animal models.

Prostaglandin E2 and myocarditis; friend or foe?

This review article summarizes the role of prostaglandin E2 (PGE2) and its receptors (EP1-EP4) as it relates to the inflammatory cardiomyopathy, myocarditis. During the COVID-19 pandemic, the onset of myocarditis in a subset of patients prompted a debate on the use of nonsteroidal anti-inflammatory drugs (NSAIDs), like ibuprofen, which act to inhibit the actions of prostaglandins. This review aims to further understanding of the role of PGE2 in the pathogenesis or protection of the myocardium in myocarditis. Inflammatory cardiomyopathies encompass a broad spectrum of disorders, all characterized by cardiac inflammation. Therefore, for the purpose of this review, the authors have placed particular emphasis on etiologies of myocarditis where effects of PGE2 have been documented.

Myocarditis: Etiology, Pathogenesis, and Their Implications in Clinical Practice

Myocarditis is an inflammatory disease of the myocardium caused by infectious or non-infectious agents. It can lead to serious short-term and long-term sequalae, such as sudden cardiac death or dilated cardiomyopathy. Due to its heterogenous clinical presentation and disease course, challenging diagnosis and limited evidence for prognostic stratification, myocarditis poses a great challenge to clinicians. As it stands, the pathogenesis and etiology of myocarditis is only partially understood. Moreover, the impact of certain clinical features on risk assessment, patient outcomes and treatment options is not entirely clear. Such data, however, are essential in order to personalize patient care and implement novel therapeutic strategies. In this review, we discuss the possible etiologies of myocarditis, outline the key processes governing its pathogenesis and summarize best available evidence regarding patient outcomes and state-of-the-art therapeutic approaches.

Diagnostics of messenger ribonucleic acid (mRNA) severe acute respiratory syndrome-corona virus‑2 (SARS-CoV‑2) vaccination-associated myocarditis—A systematic review

Background

Objective

Methods

Results

Conclusion

Supplementary Information

Prevalence, Cell Tropism, and Clinical Impact of Human Parvovirus Persistence in Adenomatous, Cancerous, Inflamed, and Healthy Intestinal Mucosa

Parvoviruses are single-stranded DNA viruses, infecting many animals from insects to humans. Human parvovirus B19 (B19V) causes erythema infectiosum, arthropathy, anemia, and fetal death, and human bocavirus (HBoV) 1 causes respiratory tract infections, while HBoV2-4 are enteric. Parvoviral genomes can persist in diverse non-permissive tissues after acute infection, but the host-cell tropism and the impact of their tissue persistence are poorly studied. We searched for parvoviral DNA in a total of 427 intestinal biopsy specimens, as paired disease-affected and healthy mucosa, obtained from 130 patients with malignancy, ulcerative colitis (UC), or adenomas, and in similar intestinal segments from 55 healthy subjects. Only three (1.6%) individuals exhibited intestinal HBoV DNA (one each of HBoV1, 2, and 3). Conversely, B19V DNA persisted frequently in the intestine, with 50, 47, 31, and 27% detection rates in the patients with malignancy, UC, or adenomas, and in the healthy subjects, respectively. Intra-individually, B19V DNA persisted significantly more often in the healthy intestinal segments than in the inflamed colons of UC patients. The highest loads of B19V DNA were seen in the ileum and colon specimens of two healthy individuals. With dual-RNAscope in situ hybridization and immunohistochemistry assays, we located the B19V persistence sites of these intestines in mucosal B cells of lymphoid follicles and vascular endothelial cells. Viral messenger RNA transcription remained, however, undetected. RNA sequencing (RNA-seq) identified 272 differentially expressed cellular genes between B19V DNA-positive and -negative healthy ileum biopsy specimens. Pathway enrichment analysis revealed that B19V persistence activated the intestinal cell viability and inhibited apoptosis. Lifelong B19V DNA persistence thus modulates host gene expression, which may lead to clinical outcomes.

Synthetic Extracellular Volume in Cardiac Magnetic Resonance Without Blood Sampling: a Reliable Tool to Replace Conventional Extracellular Volume

Background:

The calculation of extracellular volume (ECV) in cardiac magnetic resonance requires hematocrit, limiting its applicability in clinical practice. Based on the linear relationship between hematocrit and blood T1 relaxivity, a synthetic ECV could be estimated without a blood sample. We aim to develop and test regression models for synthetic ECV without blood sampling in 1.5-T and 3.0-T scanners.

Methods:

A total of 1101 subjects who underwent cardiac magnetic resonance scanning with native and postcontrast T1 mapping and venous hematocrit within 24 hours were retrospectively enrolled. Subjects were randomly split into derivation (n=550) and validation (n=551) subgroups for each scanner. Different regression models were derived controlling for sex, field strength, and left ventricle/right ventricle blood pool and validated in the validation group. We performed additional validation analyses in subgroups of patients with histological validation (n=17), amyloidosis (n=29), anemia (n=185), and reduced ejection fraction (n=322).

Results:

In the derivation group, 8 specific models and 2 common estimate models were derived. In the validation group, using specific models, synthetic ECV had high agreement with conventional ECV (R², 0.87; P<0.0001 and R², 0.88, P<0.0001; −0.16% and −0.10%, left ventricle and right ventricle model, respectively). Common models also performed well (R², 0.88; P<0.0001 and R², 0.89, P<0.0001; −0.21% and −0.18%, left ventricle and right ventricle model, respectively). Histological validation demonstrated equal performance of synthetic and measured ECV. Synthetic ECV as calculated by the common model showed a bias in the anemia cohort significantly reduced by the specific model (−2.45 to −1.28, right ventricle common and specific model, respectively).

Conclusions:

Synthetic ECV provided a promising way to calculate ECV without blood sampling. Specific models could provide the most accurate value, while common models could be more suitable in routine clinical practice because of their simplicity while maintaining adequate accuracy.

COVID-lateral damage: cardiovascular manifestations of SARS-CoV-2 infection

Early in the pandemic, concern that cardiovascular effects would accompany COVID-19 was fueled by lessons from the first SARS epidemic, knowledge that the SARS-COV2 entry receptor (Angiotensin-converting enzyme 2, ACE2) is highly expressed in the heart, early reports of myocarditis, and first-hand accounts by physicians caring for those with severe COVID-19. Over 18 months, our understanding of the cardiovascular manifestations has expanded greatly, leaving more new questions than those conclusively answered. Cardiac involvement is common (∼20%) but not uniformly observed in those who require treatment in a hospitalized setting. Cardiac MRI studies raise the possibility of manifestations in those with minimal symptoms. Some appear to experience protracted cardiovascular symptoms as part of a larger syndrome of post-acute sequelae of COVID-19. Instances of vaccine induced thrombosis and myocarditis are exceedingly rare but illustrate the need to monitor the cardiovascular safety of interventions that induce inflammation. Here, we will summarize the current understanding of potential cardiovascular manifestations of SARS-COV2. To provide proper context, paradigms of cardiovascular injury due to other inflammatory processes will also be discussed. Ongoing research and a deeper understanding COVID-19 may ultimately reveal new insight into the mechanistic underpinnings of cardiovascular disease. Thus, in this time of unprecedented suffering and risk to global health, there exists the opportunity that well conducted translational research of SARS-COV2 may provide health dividends that outlast the current pandemic.

Ultrastructural Changes in Mitochondria in Patients with Dilated Cardiomyopathy and Parvovirus B19 Detected in Heart Tissue without Myocarditis

Understanding the meaning of parvovirus B19 (PB19V) in an etiology of dilated cardiomyopathy (DCM) is difficult. Viruses change the dynamics of the mitochondria by interfering with the mitochondrial process/function, causing the alteration of mitochondrial morphology. In this study, the ultrastructural changes in the mitochondria in endomyocardial biopsy (EMB) samples from patients with DCM and PB19V were determined. Methods: The PB19V evaluation was performed in EMB specimens by real-time PCR in 20 patients (age: 28 ± 6 years). The biopsy specimens were examined by histo- and immunohistochemistry to detect the inflammatory response. The ultrastructural features of the mitochondria were evaluated by electron microscopy. Results: The presence of PB19V in the heart tissue without the presence of inflammatory process, defined according to Dallas and immunohistochemical criteria, was associated with ultrastructural changes in the mitochondria. Distinctive ultrastructural pathologies were indicated, such as the presence of mitochondria in the vicinity of the expanded sarcoplasmic reticulum with amorphous material, blurred structure of mitochondria, interrupted outer mitochondrial membrane and mitophagy. Conclusions: Extending diagnostics with ultrastructural analysis of biopsy samples provides new knowledge of the changes associated with the presence of PB19V in the heart tissue. The observed changes can be a basis for searching for the damage mechanisms, as well as for new therapeutic solutions.

Diagnosis of Cardiac Involvement in Amyloid A Amyloidosis by Cardiovascular Magnetic Resonance Imaging

Background: Diagnosis of cardiac involvement in amyloid A (AA) amyloidosis is challenging since AA amyloidosis is a rare disease and cardiac involvement even less frequent. The diagnostic yield of currently available non-invasive imaging methods is not well-studied and rather limited, and invasive endomyocardial biopsy (EMB) is rarely performed due to the potential risk of this procedure. Cardiovascular magnetic resonance (CMR)-based myocardial tissue characterization by late-gadolinium-enhancement (LGE) imaging and novel-mapping approaches may increase the diagnostic yield in AA amyloidosis.

Methods: Two patients with AA amyloidosis in whom cardiac involvement was suspected based on CMR findings and subsequently proven by biopsy work-up are presented. CMR studies were performed on a 1.5-T system and comprised a cine steady-state free precession pulse sequence for ventricular function and a late-gadolinium-enhancement (LGE) sequence for detection of myocardial pathology. Moreover, a modified Look-Locker inversion recovery (MOLLI) T1-mapping sequence was applied in basal, mid and apical short-axes prior to contrast agent administration and ~20 min thereafter to determine native T1 and ECV values.

Results: Both patients showed slightly dilated left ventricles (LV) with mild to moderate LV hypertrophy and preserved systolic function. Only a very subtle pattern of LGE was observed in both patients with AA amyloidosis. However, markedly elevated native T1 (max. 1,108 and 1,112 ms, respectively) and extracellular volume fraction (ECV) values (max. 39 and 48%, respectively) were measured in the myocardium suggesting the presence of cardiac involvement - with subsequent EMB-based proof of AA amyloidosis.

Conclusion: We recommend a multi-parametric CMR approach in patients with AA amyloidosis comprising both LGE-based contrast-imaging and T1-mapping-based ECV measurement of the myocardium for non-invasive work-up of suspected cardiac involvement. The respective CMR findings may be used as gatekeeper for additional invasive procedures (such as EMB) and as a non-invasive monitoring tool regarding assessment and modification of ongoing treatments.

The Desmin Mutation DES-c.735G>C Causes Severe Restrictive Cardiomyopathy by Inducing In-Frame Skipping of Exon-3

Currently, little is known about the genetic background of restrictive cardiomyopathy (RCM). Herein, we screened an index patient with RCM in combination with atrial fibrillation using a next generation sequencing (NGS) approach and identified the heterozygous mutation DES-c.735G>C. As DES-c.735G>C affects the last base pair of exon-3, it is unknown whether putative missense or splice site mutations are caused. Therefore, we applied nanopore amplicon sequencing revealing the expression of a transcript without exon-3 in the explanted myocardial tissue of the index patient. Western blot analysis verified this finding at the protein level. In addition, we performed cell culture experiments revealing an abnormal cytoplasmic aggregation of the truncated desmin form (p.D214-E245del) but not of the missense variant (p.E245D). In conclusion, we show that DES-c.735G>C causes a splicing defect leading to exon-3 skipping of the DES gene. DES-c.735G>C can be classified as a pathogenic mutation associated with RCM and atrial fibrillation. In the future, this finding might have relevance for the genetic understanding of similar cases.

Numbers and phenotype of non-classical CD14dimCD16+ monocytes are predictors of adverse clinical outcome in patients with coronary artery disease and severe SARS-CoV-2 infection

AIMS

To elucidate the prognostic role of monocytes in the immune response of patients with coronary artery disease (CAD) at risk for life-threatening heart and lung injury as major complications of SARS-CoV-2 infection.

METHODS AND RESULTS

From February to April 2020, we prospectively studied a cohort of 96 participants comprising 47 consecutive patients with CAD and acute SARS-CoV-2 infection (CAD + SARS-CoV-2), 19 CAD patients without infections, and 30 healthy controls. Clinical assessment included blood sampling, echocardiography, and electrocardiography within 12 h of admission. Respiratory failure was stratified by the Horovitz Index (HI) as moderately/severely impaired when HI ≤200 mmHg. The clinical endpoint (EP) was defined as HI ≤200 mmHg with subsequent mechanical ventilation within a follow-up of 30 days. The numbers of CD14dimCD16+ non-classical monocytes in peripheral blood were remarkably low in CAD + SARS-CoV-2 compared with CAD patients without infection and healthy controls (P < 0.0001). Moreover, these CD14dimCD16 monocytes showed decreased expression of established markers of adhesion, migration, and T-cell activation (CD54, CD62L, CX3CR1, CD80, and HLA-DR). Decreased numbers of CD14dimCD16+ monocytes were associated with the occurrence of EP. Kaplan-Meier curves illustrate that CAD + SARS-CoV-2 patients with numbers below the median of CD14dimCD16+ monocytes (median 1443 cells/mL) reached EP significantly more often compared to patients with numbers above the median (log-rank 5.03, P = 0.025).

CONCLUSION

Decreased numbers of CD14dimCD16+ monocytes are associated with rapidly progressive respiratory failure in CAD + SARS-CoV-2 patients. Intensified risk assessments comprising monocyte sub- and phenotypes may help to identify patients at risk for respiratory failure.

Cardiac inflammation in COVID-19: Lessons from heart failure

Cardiovascular disease (CVD) is the most common co-morbidity associated with COVID-19 and the fatality rate in COVID-19 patients with CVD is higher compared to other comorbidities, such as hypertension and diabetes. Preliminary data suggest that COVID-19 may also cause or worsen cardiac injury in infected patients through multiple mechanisms such as 'cytokine storm', endotheliosis, thrombosis, lymphocytopenia etc. Autopsies of COVID-19 patients reveal an infiltration of inflammatory mononuclear cells in the myocardium, confirming the role of the immune system in mediating cardiovascular damage in response to COVID-19 infection and also suggesting potential causal mechanisms for the development of new cardiac pathologies and/or exacerbation of underlying CVDs in infected patients. In this review, we discuss the potential underlying molecular mechanisms that drive COVID-19-mediated cardiac damage, as well as the short term and expected long-term cardiovascular ramifications of COVID-19 infection in patients.

Inflammatory dilated cardiomyopathy : Etiology and clinical management

Inflammatory dilated cardiomyopathy (DCMi) is a syndrome, not an etiological disease entity. The infective etiology and the immunopathology can be best determined through endomyocardial biopsy with a complete work-up by light microscopy, immunohistology, and polymerase chain reaction for microbial agents. This review focuses on the methodological advances in diagnosis in the past few years and exemplifies the importance of an etiology-orientated treatment in different case scenarios. In fulminant nonviral myocarditis, immunosuppressive treatment together with hemodynamic stabilization of the patient via mechanical circulatory support (e.g., microaxial pumps, extracorporeal membrane oxygenation, left ventricular assist device) can be life-saving. For viral inflammatory cardiomyopathy, intravenous immunoglobulin treatment can resolve inflammation and often eradicate the virus.

Role of Smoking in the Evolution of Cardiovascular Magnetic Resonance and Laboratory Findings of Acute Myocarditis

Purpose

The purpose is to investigate cardiac magnetic resonance and laboratory findings in patients with clinically suspected acute myocarditis and re-assess the evolution of findings in relation to clinical parameters and smoking habits.

Methods

We prospectively analyzed 68 consecutive patients (4 females, 64 males, median age 25 years) at baseline and 51 patients 12 months later with regard to age, symptoms, and signs, smoking history, cardiac troponin I, erythrocyte sedimentation rate, c-reactive protein blood levels, electrocardiography changes, and cardiac magnetic resonance findings. Statistical analysis included group comparisons and linear regression between clinical parameters and the obtained data.

Results

A statistically significant correlation was recorded between smoking and late gadolinium enhancement extent, both at baseline and follow-up study. Late gadolinium enhancement extent was positively associated with cardiac troponin I serum levels and c-reactive protein and negatively with left ventricular ejection fraction at baseline study. Myocardial segments 4 and 5 were most frequently involved. Late gadolinium enhancement persisted in 96% of patients with no significant extent change at 12-month follow-up, while improved.

Conclusions

A strong correlation was recorded between smoking patients with acute myocarditis and extent both at baseline and follow-up cardiac magnetic resonance. Myocardial segments 4 and 5 involvement was most prevalent. Late gadolinium enhancement persisted at follow-up, its incidence was higher than that reported in other studies and did not have an impact on the patient's clinical status or cardiac function. However, longer-term follow-up is highly recommended in these patients.

Regulation of cell death in the cardiovascular system

The adult heart is a post-mitotic terminally differentiated organ; therefore, beyond development, cardiomyocyte cell death is maladaptive. Heart disease is the leading cause of death in the world and aberrant cardiomyocyte cell death is the underlying problem for most cardiovascular-related diseases and fatalities. In this chapter, we will discuss the different cell death mechanisms that engage during normal cardiac development, aging, and disease states. The most abundant loss of cardiomyocytes occurs during a myocardial infarction, when the blood supply to the heart is obstructed, and the affected myocardium succumbs to cell death. Originally, this form of cell death was considered to be unregulated; however, research from the last half a century clearly demonstrates that this form of cell death is multifaceted and employees various degrees of regulation. We will explore all of the cell death pathways that have been implicated in this disease state and the potential interplay between them. Beyond myocardial infarction, we also explore the role and mechanisms of cardiomyocyte cell death in heart failure, myocarditis, and chemotherapeutic-induced cardiotoxicity. Inhibition of cardiomyocyte cell death has extensive therapeutic potential that will increase the longevity and health of the human heart.

Molecular determinants of mesenchymal cell activation in fibroproliferative diseases

Uncontrolled scarring, or fibrosis, can interfere with the normal function of virtually all tissues of the body, ultimately leading to organ failure and death. Fibrotic diseases represent a major cause of death in industrialized countries. Unfortunately, no curative treatments for these conditions are yet available, highlighting the critical need for a better fundamental understanding of molecular mechanisms that may be therapeutically tractable. The ultimate indispensable effector cells responsible for deposition of extracellular matrix proteins that comprise scars are mesenchymal cells, namely fibroblasts and myofibroblasts. In this review, we focus on the biology of these cells and the molecular mechanisms that regulate their pertinent functions. We discuss key pro-fibrotic mediators, signaling pathways, and transcription factors that dictate their activation and persistence. Because of their possible clinical and therapeutic relevance, we also consider potential brakes on mesenchymal cell activation and cellular processes that may facilitate myofibroblast clearance from fibrotic tissue-topics that have in general been understudied.

Calpain regulates CVB3 induced viral myocarditis by promoting autophagic flux upon infection

Calpains are calcium-activated neutral cysteine proteases. The dysregulation of calpain activity has been found to be related to cardiovascular diseases, for which calpain inhibition is used as a treatment. Viral myocarditis (VMC) is primarily caused by Coxsackievirus group B3 virus infection (CVB3). CVB3 virus infection induces autophagy and hijacks this process to facilitate its replication. In this study, we found that calpain was significantly activated in hearts affected by VMC. However, pharmacologically inhibiting calpain aggravated VMC symptoms in mice due to myocardial inflammation and cardiac dysfunction. The inhibition of calpain activity in vitro led to the accumulation of LC3-II and increased levels of p62/SQSTM1 protein expression, suggesting that autophagic flux was impaired by calpain inhibition. These effects of calpain inhibition were also observed in capn4-specific myocardial knockout mice in vivo. Furthermore, our results provided evidence that calpain inhibition in VMC, unlike other cardiovascular diseases, exacerbated the disease symptom by impairing CVB3-induced autophagic flux, which may subsequently reduce virus autolysosome degradation. Our findings indicated that calpain inhibition may not be a good treatment for VMC disease in a clinical setting.

An Out-of-Season Case of Coxsackie B Myocarditis with Severe Rhabdomyolysis

A 21-year-old woman was found to have fulminant myocarditis as a result of Coxsackie B infection (a virus shown to exhibit summer-fall seasonality) in mid-December. In this case report, seasonality of enteroviruses is examined, as well as additional factors which may contribute to sporadic cases during winter months. The case report also discusses clinical criteria for endomyocardial biopsy, utility of PCR vs. antibody serological tests, coinfection with multiple serotypes, and rhabdomyolysis in Coxsackie B.

Approximation of the Incidence of Myocarditis by Systematic Screening With Cardiac Magnetic Resonance Imaging

OBJECTIVES

This study sought to obtain an approximation of the true incidence of myocarditis by systematic screening of patients at risk using cardiac magnetic resonance imaging (CMR) in a tertiary care center.

BACKGROUND

Underdiagnosis of myocarditis and resulting uncertainty about its incidence remain a clinical dilemma. The authors hypothesized that systematic screening of patients presenting with angina-like symptoms, elevated troponin T, and no significant coronary artery disease using CMR will provide an approximation of the true incidence of myocarditis.

METHODS

The authors performed a retrospective chart review of patients presenting with angina-like symptoms and elevated high-sensitivity troponin T (TnT-hs ≥14 ng/l) in 2015 and 2016. During the year 2015, only patients with elevated TnT-hs, no significant coronary artery disease, and moderate-to-high clinical likelihood of myocarditis underwent CMR. Starting in 2016, CMR was obtained in patients with similar presentation, but independent of clinical likelihood of myocarditis.

RESULTS

A total of 1,788 patients (74% male, age 69 ± 14 years) qualified for our analysis. In 2015, 521 patients presented with angina-like symptoms and TnT-hs elevation. In 2016, the number increased to 1,267 patients. Although in the year 2015, a total of 4 of 88 (5%) CMRs were positive for myocarditis, the percentage of positive CMRs doubled (26 of 199; 13%; p = 0.03) in 2016.

CONCLUSIONS

A novel diagnostic screening algorithm led to a 6.3-fold increase of the incidence of myocarditis in our hospital. Furthermore, the percentage of CMRs positive for myocarditis doubled, supporting the diagnostic value of this method. Considering the potentially lethal adverse events of myocarditis if left untreated, we recommend a low threshold for the use of CMR in patients with angina-like symptoms and elevated TnT-hs after exclusion of coronary artery disease.

N-Terminomics TAILS Identifies Host Cell Substrates of Poliovirus and Coxsackievirus B3 3C Proteinases That Modulate Virus Infection

Enteroviruses encode proteinases that are essential for processing of the translated viral polyprotein. In addition, viral proteinases also target host proteins to manipulate cellular processes and evade innate antiviral responses to promote replication and infection. Although some host protein substrates of enterovirus proteinases have been identified, the full repertoire of targets remains unknown. We used a novel quantitative in vitro proteomics-based approach, termed terminal amine isotopic labeling of substrates (TAILS), to identify with high confidence 72 and 34 new host protein targets of poliovirus and coxsackievirus B3 (CVB3) 3C proteinases (3Cpros) in HeLa cell and cardiomyocyte HL-1 cell lysates, respectively. We validated a subset of candidate substrates that are targets of poliovirus 3Cproin vitro including three common protein targets, phosphoribosylformylglycinamidine synthetase (PFAS), hnRNP K, and hnRNP M, of both proteinases. 3Cpro-targeted substrates were also cleaved in virus-infected cells but not noncleavable mutant proteins designed from the TAILS-identified cleavage sites. Knockdown of TAILS-identified target proteins modulated infection both negatively and positively, suggesting that cleavage by 3Cpro promotes infection. Indeed, expression of a cleavage-resistant mutant form of the endoplasmic reticulum (ER)-Golgi vesicle-tethering protein p115 decreased viral replication and yield. As the first comprehensive study to identify and validate functional enterovirus 3Cpro substrates in vivo, we conclude that N-terminomics by TAILS is an effective strategy to identify host targets of viral proteinases in a nonbiased manner.IMPORTANCE Enteroviruses are positive-strand RNA viruses that encode proteases that cleave the viral polyprotein into the individual mature viral proteins. In addition, viral proteases target host proteins in order to modulate cellular pathways and block antiviral responses in order to facilitate virus infection. Although several host protein targets have been identified, the entire list of proteins that are targeted is not known. In this study, we used a novel unbiased proteomics approach to identify ∼100 novel host targets of the enterovirus 3C protease, thus providing further insights into the network of cellular pathways that are modulated to promote virus infection.

The Impact of Human Parvovirus B19 Infection on Heart Failure and Anemia with Reference to Iron Metabolism Markers in an Adult Woman

A 35-year-old woman with fever, edema and rash was admitted. Pleural effusion and cardiomegaly were observed. A laboratory analysis revealed anemia with iron deficiency and elevated human parvovirus B19 (B19V) immunoglobulin M. The patient's hepcidin-25 and erythroferrone levels were not elevated compared to those observed later in her clinical course. On the other hand, her growth differentiation factor-15 (GDF-15) levels were elevated. She was diagnosed to have heart failure symptoms and anemia with specific iron metabolism abnormalities due to a B19V infection. After providing supportive treatment, the heart failure symptoms disappeared and her anemia had improved. This case emphasizes the need to include a B19V infection in the differential diagnosis when we encounter cases demonstrating reversible heart failure with anemia.

TRAF6: A player in CVB3-induced myocarditis?

Coxsackievirus B3 (CVB3) is an important inducer of myocarditis, which, in susceptible individuals, can chronify and eventually lead to the development of dilated cardiomyopathy and heart failure. The respective mechanisms are not completely understood. Here, we analyzed expression of the TRAF6 gene, encoding TNF receptor-associated factor 6 (TRAF6), a signal transduction scaffold protein that acts downstream of cytokine receptors, in heart tissue of susceptible and non-susceptible mouse strains. We found that after infection, TRAF6 expression was upregulated in both non-susceptible C57BL/6 wildtype and susceptible A.BY/SnJ and C57BL/6-TLR3 (-/-) mice, however, to different degrees. In infected HeLa cells, we also found moderately elevated TRAF6 levels after infection, in addition, activity of the transcription factor nuclear factor kappa B (NFκB), which can be activated downstream of TRAF6, was strongly enhanced in infected cells. To functionally analyze the role of TRAF6 with regard to infection progression, TRAF6 expression was knocked down in cultured HeLa cells using specific siRNAs. We found that reduction of TRAF6 expression had no effect on NFκB activation in response to infection. Taken together, our data suggest that CVB3 infection enhances TRAF6 levels, however, this induction might not be necessary for infection-induced NFκB activation.

Outcome predictors in dilated cardiomyopathy or myocarditis

BACKGROUND

The objective of this study was to identify parameters of prognostic relevance in patients presenting with chronic left ventricular dysfunction who underwent endomyocardial biopsy.

MATERIALS AND METHODS

A total of 351 consecutive patients (age 47·7 ± 12·6 years, 281 male) with a chronic left ventricular dysfunction were enrolled. Endomyocardial biopsies were analysed by histopathology according to Dallas criteria and immunohistological WHO criteria. Virus genome was detected by polymerase chain reaction. The combined end point was time to death or heart transplantation.

RESULTS

About 19% of patients (n = 67) showed positive Dallas criteria and 39% (n = 118) immunohistochemical signs of inflammation. Viral genome was present in 58% (n = 155). During follow-up, 25% (n = 89; 76 death, 13 HTx) reached the end point. Dallas-positive histopathology (hazard ratio: 0·42; 95% CI: 0·29-0·84, P = 0·031), ejection fraction (hazard ratio: 0·97; 95% CI: 0·94-0·99, P = 0·019) and β-blocker therapy (hazard ratio: 0·41; 95% CI: 0·23-0·69, P = 0·003) were independent outcome predictors. For patients under β-blocker therapy, Dallas-positive histopathology (hazard ratio: 0·37; 95% CI: 0·25-0·76, P = 0·009) and NYHA class III and class IV (hazard ratio: 2·11; 95% CI: 1·04-3·12, P = 0·006) were independent predictors.

CONCLUSIONS

For patients with a chronic left ventricular dysfunction, Dallas-positive histopathology, β-blocker therapy and left ventricular ejection fraction are the most striking parameters for outcome prediction.

CMR-Derived Extracellular Volume Fraction as a Marker for Myocardial Fibrosis: The Importance of Coexisting Myocardial Inflammation

OBJECTIVES

The aim of the present study was to evaluate whether extracellular volume fraction (ECV) can reliably inform on the extent of diffuse fibrosis in the simultaneous presence of myocardial inflammation, which has not been verified to date.

BACKGROUND

Diffuse myocardial fibrosis is associated with unfavorable outcome in patients with cardiomyopathy, and is of prognostic relevance. Assessment of ECV bears promise for being a noninvasive surrogate parameter, but it may be altered by other pathologies.

METHODS

In this prospective study, 107 consecutive patients with clinical suspicion of inflammatory cardiomyopathy were included. All patients underwent left ventricular (LV) endomyocardial biopsy (EMB) and cardiac magnetic resonance imaging on a 1.5-T scanner. T1 mapping was obtained with the modified Look-Locker inversion recovery sequence, and ECV was calculated.

RESULTS

Myocardial inflammation was present in 66 patients. Patients with and without inflammation were of similar age and had comparable LV ejection fraction (37 ± 17% vs. 36 ± 18%; p = 0.9) and symptom duration (median 14 days [interquartile range: 5 to 36 days] vs. median 14 days [interquartile range: 7 to 30 days]; p = 0.73). Although LV collagen volume percentage was comparable between groups (inflammation 12.3 ± 17.8% vs. noninflammation 11.4 ± 7.9%; p = 0.577), ECV was significantly higher in patients with inflammation (0.37 ± 0.06%) than in those without inflammation (0.33 ± 0.08%; p = 0.02). Importantly, ECV adequately estimated the degree of LV fibrosis percentage only in patients without inflammation (r = 0.72; p < 0.0001) and not in those with inflammation (r = 0.24; p = 0.06).

CONCLUSIONS

These findings prove the theoretical concept of ECV as an estimate for diffuse myocardial fibrosis, but only in the absence of significant myocardial inflammation. Assuming that various degrees of myocardial inflammation and fibrosis coexist in such a scenario, the measured ECV will reflect a sum of these different pathologies but will not inform solely on the extent of diffuse fibrosis.

Plasma and Cardiac Galectin-3 in Patients With Heart Failure Reflects Both Inflammation and Fibrosis

Background—

Galectin (Gal)-3 is a β-galactoside-binding lectin and currently intensely studied as a biomarker in heart failure. Gal-3 also exerts proinflammatory effects, at least in extracardiac tissues. Objective of this study was to characterize the relationship of plasma and myocardial Gal-3 levels with cardiac fibrosis and inflammation in patients with nonischemic dilated cardiomyopathy and inflammatory cardiomyopathy (iCMP).

Methods and Results—

Endomyocardial biopsies and blood samples were obtained from patients with newly diagnosed cardiomyopathy and clinical suspicion of myocarditis. According to histopathologic findings, patients were classified as having dilated cardiomyopathy (n=40) or iCMP (n=75). Cardiac fibrosis was assessed histologically on endomyocardial biopsy sections. In patients with iCMP, myocardial Gal-3 expression significantly correlated with inflammatory cell count on endomyocardial biopsy ( r =0.56; P <0.05). In contrast, an inverse association was observed between myocardial Gal-3 expression and cardiac fibrosis in patients with iCMP ( r =−0.59; P <0.05). In patients with dilated cardiomyopathy, myocardial Gal-3 expression correlated with cardiac fibrosis on left ventricular biopsy ( P =0.63; P <0.01). Of note, in both groups, plasma Gal-3 levels did not correlate with myocardial Gal-3 levels or left ventricular fibrosis, whereas a positive correlation between plasma Gal-3 levels and inflammatory cell count on endomyocardial biopsy was observed in patients with iCMP.

Conclusions—

The present study suggests that myocardial Gal-3 can be considered as a possible marker for both cardiac inflammation and fibrosis, depending on the pathogenesis of heart failure. However, circulating concentrations of Gal-3 do not seem to reflect endomyocardial Gal-3 levels or cardiac fibrosis.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Relevance of cardiac parvovirus B19 in myocarditis and dilated cardiomyopathy: review of the literature

Over the last decade, parvovirus B19 (B19V) has frequently been linked to the pathogenesis of myocarditis (MC) and its progression towards dilated cardiomyopathy (DCM). The exact role of the presence of B19V and its load remains controversial, as this virus is also found in the heart of healthy subjects. Moreover, the prognostic relevance of B19V prevalence in endomyocardial biopsies still remains unclear. As a result, it is unclear whether the presence of B19V should be treated. This review provides an overview of recent literature investigating the presence of B19V and its pathophysiological relevance in MC and DCM, as well as in normal hearts. In brief, no difference in B19V prevalence is observed between MC/DCM and healthy control hearts. Therefore, the question remains open whether and how cardiac B19V may be of pathogenetic importance. Findings suggest that B19V is aetiologically relevant either in the presence of other cardiotropic viruses, or when B19V load is high and/or actively replicating, which both may maintain myocardial (low-grade) inflammation. Therefore, future studies should focus on the prognostic relevance of the viral load, replicative status and virus co-infections. In addition, the immunogenetic background of MC/DCM patients that makes them susceptible to develop heart failure upon presence of B19V should be more thoroughly investigated.

Endomyocardial biopsy in patients with cardiomyopathy of unknown origin: does specialized center experience apply to a tertiary care hospital?

BACKGROUND

In patients with cardiomyopathy of unknown origin, endomyocardial biopsy provides the possibility of improved diagnosis and tailored treatment. Specific guidance has been developed based on cardiovascular centre of excellence experience but it is unknown if the benefits also extend into the tertiary care hospital setting.

METHODS

Endomyocardial biopsies was performed in patients with cardiomyopathy of unknown origin. The outcomes were mirrored against the current ESC recommendations.

RESULTS

A total of 57 patients with cardiomyopathy of unknown origin underwent endomyocardial biopsy with a mean age of 54 years and 28 % being women. In 17 patients (30 %), viruses were detected in the biopsy material, in 6 patients (11 %) cardiac amyloidosis was found of which 3 had also a positive test for viruses. The overall mortality rate was 18 % in the mean follow up period of 30 months, with a rate of 24 % in those with virus detection (mean FU 24 months) and 15 % in those without virus detection (mean FU 31 months. Death rates were 83 % in patients with cardiac amyloidosis (mean FU 10 months).

CONCLUSION

We conclude that, limited by uncertainty stemming from the small number of included patients, endomyocardial biopsy may not prove to have a clinical impact on treatment decisions and outcomes in a tertiary care hospital setting. We consider cardiac amyloidosis to be an exception, since the mortality rate with or without concomitant virus load was extremely high.

A new monoclonal antibody (Cox mAB 31A2) detects VP1 protein of coxsackievirus B3 with high sensitivity and specificity

Human enteroviruses, e.g. coxsackieviruses, induce a variety of severe acute and chronic forms of disease, including myocarditis, meningitis and diabetes mellitus type 1. To visualize enterovirus infection with a diagnostic intent, many studies have applied a commercially available antibody (anti-CVB5 VP1, clone 5-D8/1, Dako, Hamburg, Germany) that identifies VP1 of different enteroviral serotypes. Many antibodies, however, have been found to bind non-specifically to proteins of cardiomyocytes and in the interstitial space, resulting in non-specific staining in immunohistochemistry. In this paper we show that the anti-CVB5 VP1 antibody, recognizing VP1 of coxsackieviruses and widely used in diagnostics and research, shows strong cross-reactivity with cellular proteins in the heart (and pancreas) of humans and mice, which calls for a more specific antibody to be used for diagnostic purposes. We observed by Western blot analyses of lysates from human heart tissue samples and HeLa cells two cross-reactive bands when using clone 5-D8/1. Peptide mass fingerprinting (MALDI-TOF) identified these proteins as creatine kinase (B-type) and tubulin, confirming that this mAb detects cellular proteins in addition to viral VP1. In order to overcome the problems of false positive VP1 staining we generated a new highly specific and sensitive monoclonal antibody (Cox mAB 31A2) that recognizes VP1 from CVB3. The new antibody was characterized and was found to function well in immunohistochemistry, immunofluorescence staining, Western blotting, ELISA and FACS analyses.

Myocarditis

Viral myocarditis remains a prominent infectious-inflammatory disease for patients throughout the lifespan. The condition presents several challenges including varied modes of clinical presentation, a range of timepoints when patients come to attention, a diversity of approaches to diagnosis, a spectrum of clinical courses, and unsettled perspectives on therapeutics in different patient settings and in the face of different viral pathogens. In this review, we examine current knowledge about viral heart disease and especially provide information on evolving understanding of mechanisms of disease and efforts by investigators to identify and evaluate potential therapeutic avenues for intervention.

Endomyocardial miR-133a levels correlate with myocardial inflammation, improved left ventricular function, and clinical outcome in patients with inflammatory cardiomyopathy

AIMS

Inflammatory heart disease represents an important cause of chronic dilated cardiomyopathy (DCM). Predicting the clinical course of patients with inflammatory cardiomyopathy (iCMP) is difficult, and the prognostic value of current biological markers remains controversial. We tested whether expression of selected microRNAs in endomyocardial biopsies (EMBs) is related to LV functional recovery and clinical events in iCMP patients.

METHODS AND RESULTS

EMBs were obtained from patients with iCMP (n = 76) and non-inflammatory DCM (n = 22). A set of six microRNAs implicated in inflammation (miR-155 and miR-146b), heart failure (miR-21 and miR-133a), and endothelial cell (miR-126) and skeletal muscle function (miR-206) was pre-defined. Endomyocardial expression of miR-155 and miR-133a, as quantified by reverse transcription-PCR (RT-PCR), was up-regulated in patients with iCMP as compared with patients with DCM. Levels of miR-133a (R = 0.73, P < 0.01) and miR-155 (R = 0.63, P < 0.01) correlated with inflammatory cell count on EMBs from patients with iCMP. Patients with iCMP and preserved LV function at study entry demonstrated higher expression of miR-133a than patients with reduced LV function. Also, increased expression of miR-133a was associated with less fibrosis and myocyte necrosis on EMB, and LV functional recovery during a mean follow-up of 3.1 years. Importantly, patients with iCMP and miR-133a levels in the upper tertile showed longer survival free of death, malignant arrhythmias, and hospitalizations for heart failure.

CONCLUSION

The present study demonstrates that miR-133a levels correlate with macrophage infiltration, cardiac injury, improved LV function, and clinical outcome in patients with iCMP. miR-133a may serve as a potential novel biomarker and therapeutic target in human iCMP.

Parvovirus B19 myocarditis in children: an observational study

BACKGROUND

The advent of PCR testing for the presence of viral genomes has led to the identification of parvovirus B19 (PVB19) as a causative agent of myocarditis.

METHODS

The clinical presentation, course and outcome of children with PVB19 myocarditis was ascertained through a retrospective review. The PVB19 viral genome was detected by PCR from whole blood or endomyocardial biopsy specimens in patients presenting with new onset heart failure.

RESULTS

Seventeen patients presented at a median age of 1.3 years (range: 0.4-15.4 years) in cardiac failure with a mean fractional shortening of 15±3%. Eleven patients required mechanical ventilation and intravenous inotropes and seven required extra-corporeal mechanical oxygenation. Four of the five deaths occurred in patients who had a short prodromal illness of less than 48 hours. All patients with ST segment elevation died (n=4). All non-fulminant cases survived. Event-free survival occurred in 11/17 (65%) patients. Five (29%) patients died and one patient underwent heart transplantation. Complete recovery of cardiac function occurred within a median of 12 months (range: 1-48) in five patients. There was incomplete recovery in five patients and one patient had persistent dilated cardiomyopathy.

CONCLUSIONS

PVB19 can cause a devastating myocarditis in children. Children with fulminant myocarditis, ST segment changes or a short prodrome have the worst outcome. Transplantation may be considered, but is rarely required in the acute period if mechanical circulatory support is utilised. If the initial presentation is survived, recovery of the myocardium can occur even in those who had fulminant myocarditis.

Clinical profile of patients with advanced age and inflammatoric dilated cardiomyopathy on endomyocardial biopsy

BACKGROUND

Endomyocardial biopsy (EMB) is an important tool when patients with inflammatoric cardiomyopathy (DCMi) are evaluated. We aimed to assess the clinical profile of elderly patients with DCMi on EMB.

METHODS

Retrospective study of all consecutive patients hospitalized from January 2007 to December 2011 with clinical suspicion of DCMi undergoing EMB. Patients with evidence of DCMi on EMB (Group 1 ≥ 70 years, n = 85; Group 3 < 70 years; n = 418) were compared to patients of the same age group without evidence of DCMi on EMB (Group 2 ≥ 70 years, n = 45; Group 4 < 70 years; n = 147).

RESULTS

Among 24,275 patients treated at our institution during the study period, 695 had clinical suspicion of DCMi and underwent EMB; 503 (2.1%) patients had DCMi on EMB. There were more male patients in Group 1, mean age was 74 ± 2.8 years, mean ejection fraction was 38% ± 14%. On presentation, signs of hemodynamic compromise (NYHA functional class III/IV, low cardiac output/index, and low cardiac power index) were more frequent in Group 1. EMB revealed viral genome in 78% of the patients, parvovirus B19 (PVB) was frequently encountered in both age groups (Group 1: 69.4% vs. Group 2: 59.6%); detection of more than one viral genome was more frequent in Group 1 (21.2% vs. 11.2%; P = 0.02) whereas the extent of immune response was significantly lower in individuals with advanced age.

CONCLUSIONS

In patients ≥ 70 years with DCMi on EMB signs of hemodynamic compromise, detection of multiple viral genomes together with an overall lower extent of immune response were more frequently observed.

Up-regulation of epithelial Na(+) channel ENaC by human parvovirus B19 capsid protein VP1

BACKGROUND

Clinical disorders caused by parvovirus B19 (B19V) infection include endothelial dysfunction with cardiac ischemia. The virus is effective in part by lysophosphatidylcholine-producing phospholipase A2 (PLA2) activity of B19V capsid protein VP1. Mechanisms compromising endothelial function include up-regulation of amiloride sensitive epithelial Na(+)-channel ENaC leading to endothelial cell stiffness. Regulators of ENaC include ubiquitin-ligase Nedd4-2. The present study explored whether VP1 modifies ENaC-activity.

METHODS

cRNA encoding ENaC was injected into Xenopus oocytes without or with cRNA encoding VP1. Experiments were made with or without coexpression of Nedd4-2. ENaC activity was estimated from amiloride (50 μM) sensitive current.

RESULTS

Injection of cRNA encoding ENaC into Xenopus oocytes was followed by appearance of amiloride sensitive current, which was significantly enhanced by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding PLA2-negative VP1 mutant (H153A). The effect of VP1 on ENaC was mimicked by treatment of ENaC expressing oocytes with lysophosphatidylcholine (1 μg/ml). The effect of VP1 and lysophosphatidylcholine was not additive. ENaC activity was downregulated by Nedd4-2, an effect not reversed by VP1.

CONCLUSIONS

The B19V capsid protein VP1 up-regulates ENaC, an effect at least partially due to phospholipase A2 (PLA) dependent formation of lysophosphatidylcholine.

Down-regulation of inwardly rectifying Kir2.1 K+ channels by human parvovirus B19 capsid protein VP1

Parvovirus B19 (B19V) has previously been shown to cause endothelial dysfunction. B19V capsid protein VP1 harbors a lysophosphatidylcholine producing phospholipase A2 (PLA2). Lysophosphatidylcholine inhibits Na(+)/K(+) ATPase, which in turn may impact on the activity of inwardly rectifying K(+) channels. The present study explored whether VP1 modifies the activity of Kir2.1 K(+) channels. cRNA encoding Kir2.1 was injected into Xenopus oocytes without or with cRNA encoding VP1 isolated from a patient suffering from fatal B19V-induced inflammatory cardiomyopathy or the VP1 mutant (H153A)VP1 lacking a functional PLA2 activity. K(+) channel activity was determined by dual electrode voltage clamp. In addition, Na(+)/K(+)-ATPase activity was estimated from K(+)-induced pump current (I(pump)) and ouabain-inhibited current (I(ouabain)). Injection of cRNA encoding Kir2.1 into Xenopus oocytes was followed by appearance of inwardly rectifying K(+) channel activity (I(K)), which was significantly decreased by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding (H153A)VP1. The effect of VP1 on I K was mimicked by lysophosphatidylcholine (1 μg/ml) and by inhibition of Na(+)/K(+)-ATPase with 0.1 mM ouabain. In the presence of lysophosphatidylcholine, I K was not further decreased by additional treatment with ouabain. The B19V capsid protein VP1 thus inhibits Kir2.1 channels, an effect at least partially due to PLA2-dependent formation of lysophosphatidylcholine with subsequent inhibition of Na(+)/K(+)-ATPase activity.

Evaluation of RT-PCR and immunohistochemistry as tools for detection of enterovirus in the human pancreas and islets of Langerhans

BACKGROUND

Enteroviruses have been implicated in the etiology of type 1 diabetes, supported by immunoreactivity of enteroviral protein in islets, but presence of enteroviral genome has rarely been reported. Failure to detect enterovirus with RT-PCR has been attributed to the possible presence of PCR inhibitors and that only few cells are infected.

OBJECTIVES

The aim of this study was to evaluate strategies for detection of enterovirus in human islets.

STUDY DESIGN

A scenario was modeled with defined infected islets among a large number of uninfected pancreatic cells and the sensitivity of immunohistochemistry and PCR for detection of enterovirus was evaluated.

RESULTS

Enterovirus was detected with PCR when only one single human islet, infected in vitro with a low dose of virus, was mixed with an uninfected pancreatic biopsy. Enterovirus could not be detected by immunohistochemistry under the same conditions, demonstrating the superior sensitivity of PCR also in pancreatic tissue with only a small fraction of infected cells. In addition, we demonstrate that pancreatic cell culture supernatant does not cause degradation of enterovirus at 37°C, indicating that under normal culture conditions released virus is readily detectable. Utilizing PCR, the pancreases of two organ donors that died at onset of type 1 diabetes were found negative for enterovirus genome despite islet cells being positive using immunohistochemistry.

CONCLUSIONS

These data suggest that PCR should be the preferred screening method for enterovirus in the pancreas and suggest cautious interpretation of immunostaining for enterovirus that cannot be confirmed with PCR.

Down-regulation of K⁺ channels by human parvovirus B19 capsid protein VP1

Parvovirus B19 (B19V) can cause inflammatory cardiomyopathy and endothelial dysfunction. Pathophysiological mechanisms involved include lysophosphatidylcholine producing phospholipase A2 (PLA2) activity of the B19V capsid protein VP1. Most recently, VP1 and lysophosphatidylcholine have been shown to inhibit Na(+)/K(+) ATPase. The present study explored whether VP1 modifies the activity of Kv1.3 and Kv1.5 K(+) channels. cRNA encoding Kv1.3 or Kv1.5 was injected into Xenopus oocytes without or with cRNA encoding VP1 isolated from a patient suffering from fatal B19V-induced myocarditis. K(+) channel activity was determined by dual electrode voltage clamp. Injection of cRNA encoding Kv1.3 or Kv1.5 into Xenopus oocytes was followed by appearance of Kv K(+) channel activity, which was significantly decreased by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding PLA2-negative VP1 mutant (H153A). The effect of VP1 on Kv current was not significantly modified by transcription inhibitor actinomycin (10 μM for 36 h) but was mimicked by lysophosphatidylcholine (1 μg/ml). The B19V capsid protein VP1 inhibits host cell Kv channels, an effect at least partially due to phospholipase A2 (PLA) dependent formation of lysophosphatidylcholine.

Dynamic mitochondrial changes during differentiation of P19 embryonic carcinoma cells into cardiomyocytes

Murine P19 embryonal carcinoma cells are multipotent cells that can differentiate into cardiomyocytes when treated with dimethyl sulfoxide. This experimental model provides an invaluable tool to study different aspects of cardiac differentiation, such as the function of cardiac‑specific transcription factors and signaling pathways, and the regulation of contractile protein expression. The role of mitochondria during cardiac differentiation is unclear. In this context, we have examined the mitochondrial-related changes in undifferentiated and differentiated P19 cells. We observed that mitochondrial DNA content sharply decreased in P19 cell aggregates compared to undifferentiated cells, accompanied by decreased levels of adenosine triphosphate (ATP) and reactive oxygen species (ROS). Following the aggregation stage, the mitochondrial DNA content reached its highest level on day 7 of the differentiation process, with the intracellular ROS level showing a trend to increase, similar to cellular ATP production. In conclusion, our study on differentiating P19 embryonal carcinoma cells provides new insights into the role of mitochondria in the differentiation of P19 stem cells into beating cardiomyocytes.

Antibody-mediated enhancement of parvovirus B19 uptake into endothelial cells mediated by a receptor for complement factor C1q

Despite its strong host tropism for erythroid progenitor cells, human parvovirus B19 (B19V) can also infect a variety of additional cell types. Acute and chronic inflammatory cardiomyopathies have been associated with a high prevalence of B19V DNA in endothelial cells of the myocardium. To elucidate the mechanisms of B19V uptake into endothelium, we first analyzed the surface expression of the well-characterized primary B19V receptor P antigen and the putative coreceptors α5β1 integrins and Ku80 antigen on primary and permanent endothelial cells. The receptor expression pattern and also the primary attachment levels were similar to those in the UT7/Epo-S1 cell line regarded as functional for B19V entry, but internalization of the virus was strongly reduced. As an alternative B19V uptake mechanism in endothelial cells, we demonstrated antibody-dependent enhancement (ADE), with up to a 4,000-fold increase in B19V uptake in the presence of B19V-specific human antibodies. ADE was mediated almost exclusively at the level of virus internalization, with efficient B19V translocation to the nucleus. In contrast to monocytes, where ADE of B19V has been described previously, enhancement does not rely on interaction of the virus-antibody complexes with Fc receptors (FcRs), but rather, involves an alternative mechanism mediated by the heat-sensitive complement factor C1q and its receptor, CD93. Our results suggest that ADE represents the predominant mechanism of endothelial B19V infection, and it is tempting to speculate that it may play a role in the pathogenicity of cardiac B19V infection. Importance: Both efficient entry and productive infection of human parvovirus B19 (B19V) seem to be limited to erythroid progenitor cells. However, in vivo, the viral DNA can also be detected in additional cell types, such as endothelial cells of the myocardium, where its presence has been associated with acute and chronic inflammatory cardiomyopathies. In this study, we demonstrated that uptake of B19V into endothelial cells most probably does not rely on the classical receptor-mediated route via the primary B19V receptor P antigen and coreceptors, such as α5β1 integrins, but rather on antibody-dependent mechanisms. Since the strong antibody-dependent enhancement (ADE) of B19V entry requires the CD93 surface protein, it very likely involves bridging of the B19V-antibody complexes to this receptor by the complement factor C1q, leading to enhanced endocytosis of the virus.

Molecular phenotypes of human parvovirus B19 in patients with myocarditis

AIM: To investigate molecular phenotypes of myocardial B19V-infection to determine the role of B19V in myocarditis and dilated cardiomyopathy (DCM).

METHODS: Endomyocardial biopsies (EMBs) from 498 B19V-positive patients with myocarditis and DCM were analyzed using molecular methods and functional experiments. EMBs were obtained from the University Hospitals of Greifswald and Tuebingen and additionally from 36 German cardiology centers. Control tissues were obtained at autopsy from 34 victims of accidents, crime or suicide. Identification of mononuclear cell infiltrates in EMBs was performed using immunohistological staining. Anti-B19V-IgM and anti-B19V-IgG were analyzed by enzyme-linked immunosorbent assay (ELISA). B19V viral loads were determined using in-house quantitative real-time polymerase chain reaction (PCR). For B19V-genotyping a new B19V-genotype-specific restriction fragment length polymorphism (RFLP)-PCR was established. B19V-genotyping was verified by direct DNA-sequencing and sequences were aligned using BLAST and BioEdit software. B19V P6-promoter and HHV6-U94-transactivator constructs were generated for cell culture experiments. Transfection experiments were conducted using human endothelial cells 1. Luciferase reporter assays were performed to determine B19V-replication activity. Statistical analysis and graphical representation were calculated using SPSS and Prism5 software.

RESULTS: The prevalence of B19V was significantly more likely to be associated with inflammatory cardiomyopathy (iCMP) compared to uninflamed DCM (59.6% vs 35.3%) (P < 0.0001). The detection of B19V-mRNA replication intermediates proved that replication of B19V was present. RFLP-PCR assays showed that B19V-genotype 1 (57.4%) and B19V-genotype 2 (36.7%) were the most prevalent viral genotypes. B19V-genotype 2 was observed more frequently in EMBs with iCMP (65.0%) compared to DCM (35%) (P = 0.049). Although there was no significant difference in gender-specific B19V-loads, women were more frequently infected with B19V-genotype 2 (44.6%) than men (36.0%) (P = 0.0448). Coinfection with B19V and other cardiotropic viruses was found in 19.2% of tissue samples and was associated with higher B19V viral load compared to B19V-monoinfected tissue (P = 0.0012). The most frequent coinfecting virus was human herpes virus 6 (HHV6, 16.5%). B19V-coinfection with HHV6 showed higher B19V-loads compared to B19V-monoinfected EMBs (P = 0.0033), suggesting that HHV6 had transactivated B19V. In vitro experiments confirmed a 2.4-fold increased B19V P6-promoter activity by the HHV6 U94-transactivator.

CONCLUSION: The finding of significantly increased B19V loads in patients with histologically proven cardiac inflammation suggests a crucial role of B19V-genotypes and reactivation of B19V-infection by HHV6-coinfection in B19V-associated iCMP. Our findings suggest that B19V-infection of the human heart can be a causative event for the development of an endothelial cell-mediated inflammatory disease and that this is related to both viral load and genotype.

Dominant-negative function of the C-terminal fragments of NBR1 and SQSTM1 generated during enteroviral infection

Coxsackievirus infection induces an abnormal accumulation of ubiquitin aggregates that are generally believed to be noxious to the cells and have a key role in viral pathogenesis. Selective autophagy mediated by autophagy adaptor proteins, including sequestosome 1 (SQSTM1/p62) and neighbor of BRCA1 gene 1 protein (NBR1), are an important pathway for disposing of misfolded/ubiquitin conjugates. We have recently demonstrated that SQSTM1 is cleaved after coxsackievirus infection, resulting in the disruption of SQSTM1 function in selective autophagy. NBR1 is a functional homolog of SQSTM1. In this study, we propose to test whether NBR1 can compensate for the compromise of SQSTM1 after viral infection. Of interest, we found that NBR1 was also cleaved after coxsackievirus infection. This cleavage took place at two sites mediated by virus-encoded protease 2A(pro) and 3C(pro), respectively. In addition to the loss-of-function, we further investigated whether cleavage of SQSTM1/NBR1 leads to the generation of toxic gain-of-function mutants. We showed that the C-terminal fragments of SQSTM1 and NBR1 exhibited a dominant-negative effect against native SQSTM1/NBR1, probably by competing for LC3 and ubiquitin chain binding. Finally, we demonstrated a positive, mutual regulatory relationship between SQSTM1 and NBR1 during viral infection. We showed that knockdown of SQSTM1 resulted in reduced expression of NBR1, whereas overexpression of SQSTM1 led to increased level of NBR1, and vice versa, further excluding the possible compensation of NBR1 for the loss of SQSTM1. Taken together, the findings in this study suggest a novel mechanism through which coxsackievirus infection induces increased accumulation of ubiquitin conjugates and subsequent viral damage.