Myocarditis, characterized by inflammatory cell infiltration, can have multiple etiologies, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or, rarely, mRNA-based coronavirus disease 2019 (COVID-19) vaccination. The underlying cellular and molecular mechanisms remain poorly understood. In this study, we performed single-nucleus RNA sequencing on left ventricular endomyocardial biopsies from patients with myocarditis unrelated to COVID-19 (Non-COVID-19), after SARS-CoV-2 infection (Post-COVID-19) and after COVID-19 vaccination (Post-Vaccination). We identified distinct cytokine expression patterns, with interferon-γ playing a key role in Post-COVID-19, and upregulated IL16 and IL18 expression serving as a hallmark of Post-Vaccination myocarditis. Although myeloid responses were similar across all groups, the Post-Vaccination group showed a higher proportion of CD4+ T cells, and the Post-COVID-19 group exhibited an expansion of cytotoxic CD8+ T and natural killer cells. Endothelial cells showed gene expression changes indicative of vascular barrier dysfunction in the Post-COVID-19 group and ongoing angiogenesis across all groups. These findings highlight shared and distinct mechanisms driving myocarditis in patients with and without a history of SARS-CoV-2 infection or vaccination. Maatz, Lindberg et al. identify molecular alterations and immune response changes in endomyocardial biopsies from patients with myocarditis after COVID-19 infection, after anti-COVID-19 vaccination or from non-COVID-related causes.

Was ist neu? Hypertrophe obstruktive Kardiomyopathie Mavacamten, der erste Myosin-Aktivator, konnte erfolgreich in dem EXPLORER-HCM-Studienprogramm getestet werden. Lebensqualität und linksventrikuläre Druckgradienten-Abnahme wurden optimiert. Ob damit jedoch auch die Überlebensrate und Prognose der betroffenen Patienten verbessert wird, kann bis heute noch nicht gesagt werden. Die europäischen Zulassungsbehörden sehen allerdings bisher die Ergebnisse als so bedeutsam an, dass mit einer Führung der Substanzklasse vielleicht schon in den nächsten 6–8 Monaten zu rechnen ist. In den USA ist die Substanz bereits seit April 2022 zugelassen. Der Einsatz der Substanz bei HCM-Patienten ohne Obstruktion wird ebenfalls zurzeit untersucht. Kardiale Transthyretin-Amyloidosen Kardiale Amyloidosen haben meist eine gute Ejektionsfraktion, jedoch sind auch EF mit 40 oder < 30 % möglich. Das Auftreten einer kardialen Amyloidose bei Patienten mit der Symptomatik einer Herzinsuffizienz mit erhaltener Ejektionsfraktion (HFpEF) ist in bis zu 15 % der Fälle nachzuweisen. Tafamidis ist die einzige zurzeit zugelassene erfolgreiche Therapiemöglichkeit bei Patienten mit kardialer ATTR-Amyloidose. Dies wurde auch durch weitere Beobachtungsregister der ATTR-ACT-Studie gezeigt. Für die Klinik ist zusätzlich wichtig, dass die Amyloidose auch die Aortenklappe befällt. Zahlreiche Patienten entwickeln somit auch eine Aortenstenose, die erkannt und meist interventionell zu behandeln ist.

Abstract Aim The acute phase of a coxsackievirus 3 (CVB3)‐induced myocarditis involves direct toxic cardiac effects and the systemic activation of the immune system, including the cardiosplenic axis. Consequently, the nucleotide‐binding oligomerization domain‐like receptor pyrin domain‐containing‐3 (NLRP3) inflammasome pathway is activated, which plays a role in disease pathogenesis and progression. The anti‐inflammatory drug colchicine exerts its effects, in part, via reducing NLRP3 activity, and has been shown to improve several cardiac diseases, including acute coronary syndrome and pericarditis. The aim of the present study was to evaluate the potential of colchicine to improve experimental CVB3‐induced myocarditis. Methods and results C57BL6/j mice were intraperitoneally injected with 1 × 105 plaque forming units of CVB3. After 24 h, mice were treated with colchicine (5 μmol/kg body weight) or phosphate‐buffered saline (PBS) via oral gavage (p.o.). Seven days post infection, cardiac function was haemodynamically characterized via conductance catheter measurements. Blood, the left ventricle (LV) and spleen were harvested for subsequent analyses. In vitro experiments on LV‐derived fibroblasts (FB) and HL‐1 cells were performed to further evaluate the anti‐(fibro)inflammatory and anti‐apoptotic effects of colchicine via gene expression analysis, Sirius Red assay, and flow cytometry. CVB3 + colchicine mice displayed improved LV function compared with CVB3 + PBS mice, paralleled by a 4.7‐fold (P < 0.01) and 1.7‐fold (P < 0.001) reduction in LV CVB3 gene expression and cardiac troponin‐I levels in the serum, respectively. Evaluation of components of the NLRP3 inflammasome revealed an increased percentage of apoptosis‐associated speck‐like protein containing a CARD domain (ASC)‐expressing, caspase‐1‐expressing, and interleukin‐1β‐expressing cells in the myocardium and in the spleen of CVB3 + PBS vs. control mice, which was reduced in CVB3 + colchicine compared with CVB3 + PBS mice. This was accompanied by 1.4‐fold (P < 0.0001), 1.7‐fold (P < 0.0001), and 1.7‐fold (P < 0.0001) lower numbers of cardiac dendritic cells, natural killer cells, and macrophages, respectively, in CVB3 + colchicine compared with CVB3 + PBS mice. A 1.9‐fold (P < 0.05) and 4.6‐fold (P < 0.001) reduced cardiac gene expression of the fibrotic markers, Col1a1 and lysyl oxidase, respectively, was detected in CVB3 + colchicine mice compared with CVB3 + PBS animals, and reflected by a 2.2‐fold (P < 0.05) decreased Collagen I/III protein ratio. Colchicine further reduced Col3a1 mRNA and collagen protein expression in CVB3‐infected FB and lowered apoptosis and viral progeny release in CVB3‐infected HL‐1 cells. In both CVB3 FB and HL‐1 cells, colchicine down‐regulated the NLRP3 inflammasome‐related components ASC, caspase‐1, and IL‐1β. Conclusions Colchicine improves LV function in CVB3‐induced myocarditis, involving a decrease in cardiac and splenic NLRP3 inflammasome activity, without exacerbation of CVB3 load.

Abstract Aims The alarmin S100A8/S100A9 (S100A8/A9) is released by activated monocytes/macrophages and neutrophils in the setting lymphocytic myocarditis (MC). We recently demonstrated its therapeutic potential in experimental acute MC. Now, we investigated the diagnostic relevance of S100A8/A9 serum levels in patients with suspected acute and chronic MC and in patients with heart failure without cardiac inflammation. Methods and Results Serum S100A8/A9 levels were analysed in patients with a recent onset of MC [≤ 30 days, n = 32; ejection fraction (EF): 45.4 ± 12.9%], dilated cardiomyopathy patients with inflammation (n = 112; EF: 29.0 ± 11.4%), or without inflammation (n = 58; EF: 26.6 ± 9.3%), and controls (n = 25; EF: 68.5 ± 4.6%), by using specific ELISAs. Blood samples were collected at Time Point 1 (T1), where also endomyocardial biopsies (EMBs) were withdrawn. Patients with a recent onset of MC showed a 4.6‐fold increase in serum S100A8/A9 levels vs. controls (MC: 1948 ± 1670 ng/mL vs. controls: 426 ± 307 ng/mL; P < 0.0001). Serum S100A8/A9 correlated with the disease activity, represented by EMB‐derived counts of inflammatory cells (CD3: r = 0.486, P = 0.0047, lymphocyte function‐associated antigen‐1: r = 0.558, P = 0.0009, macrophage‐1 antigen: r = 0.434, P = 0.013), the EMB mRNA levels of S100A8, S100A9 (r = 0.541, P = 0.002), and left ventricular ejection fraction (LVEF: r = 0.498, P = 0.0043). EMB immunofluorescence co‐stainings display macrophages/monocytes and neutrophils as the main source of S100A8 and S100A9 in recent onset MC. The diagnostic value of serum alarmin levels (cut‐off 583 ng/mL) was characterized by a specificity of 92%, a sensitivity of 90.6%, positive predictive value of 93.5%, negative predictive value of 88.5%, and an accuracy of 0.949 (95% confidence interval [0.89–1]). In a subgroup of MC patients, S100A8/A9 serum levels and EMBs at T1 (n = 12) and a follow‐up visit (T2, n = 12, mean follow‐up 8.5 months) were available. A fall of serum S100A8/A9 (T1: 2208 ± 1843 ng/mL vs. T2: 888.8 ± 513.7 ng/mL; P = 0.00052) was associated with a reduced cardiac inflammation (CD3 T1: 70.02 ± 107.4 cells per square millimetre vs. T2: 59.18 ± 182.5 cells per square millimetre; P = 0.0342, lymphocyte function‐associated antigen‐1 T1: 133.5 ± 187.1 cells per square millimetre vs. T2: 74.12 ± 190.5 cells per square millimetre; P = 0.0186, and macrophage‐1 antigen T1: 132.6 ± 129.5 cells per square millimetre vs. T2: 54.41 ± 65.16 cells per square millimetre; P = 0.0015). Serum S100A8/A9 levels were only slightly increased in patients within the chronic phase of MC and in heart failure patients without inflammation vs. controls. Conclusions Serum S100A8/A9 might serve as an additional tool in the diagnostic workup of suspected acute MC patients.

Abstract Background The alarmin S100A8/A9 has been shown to be of importance in several inflammatory cardiovascular disorders. We recently demonstrated the pivotal role of cardiac S100A8/A9 in human and experimental Coxsackievirus B3 (CVB3)-induced myocarditis (MC). Purpose We aimed to evaluate whether serum S100A8/A9 levels are a marker in patients with a recent onset of MC Methods Serum S100A8/A9, hsCRP, and NT pro-BNP levels were analyzed in patients with a recent onset of MC (≤30 days (d), n=29; ejection fraction (EF): 44.3%±13%), dilated cardiomyopathy patients with inflammation (DCMi: n=112; EF: 28.8%±12%) or without inflammation (DCM: n=58; EF: 26.7%±9%), and controls (co: n=25; EF: 68.5%±5%). Blood samples and endomyocardial biopsies (EMB) were collected at time point (T1). In a subgroup, S100A8/A9 serum levels and EMB were available at T1 (n=10) and follow-up (T2, n=10, mean follow-up 8 months). Results MC ≤30 d patients showed a 4.5-fold (p<0.0001), 19.3-fold (p<0.0001), and 4.0-fold (p<0.0001) increase in S100A8/A9, hsCRP, NT pro-BNP levels vs co, respectively. S100A8/A9 levels correlated with the disease activity, displayed by EMB counts of inflammatory cells (CD3: r=0.464, p=0.0128, XY pairs=28, LFA-1: r=0.551, p=0.002, XY pairs=28, Mac-1: r=0.418, p=0.026, XY pairs=28), and the EF (r=0.545, p=0.0027, XY pairs=28). MC ≤30 d patients showed an association between serum S100A8/A9 levels and EMB S100A8 (r=0.482, p=0.060, XY pairs=16), S100A9 (r=0.441, p=0.088, XY pairs=16), nucleotide-binding oligomerization domain containing-protein 2 (NOD2, r=0.55, p=0.035, XY=15), and Nod-like receptor family, pyrin domain-containing 3 protein (NLRP3, r=0.52, p=0.048, XY=15) mRNA levels. Also EMB S100A8 and S100A9 mRNA levels showed a significant correlation with EMB NOD2 and NLRP3 mRNA expression. Serum S100A8/A9 levels were increased by 3.0-fold (p<0.0001) and 1.8-fold (p=0.0005) in DCMi (n=112), and DCM (n=58) patients vs co, respectively. However, the S100A8/A9 levels of DCMi and DCM patients were 1.5-fold (p=0.07) and 2.5-fold (p<0.0001) lower vs MC ≤30 d patients. ROC analyses of S100A8/A9 in MC ≤30 d provided a cut-off of 583 ng/ml with a specificity=92%, sensitivity=86.2%, a PPV=92.6%, a NPV=85.2%, and an AUC=0.934 vs co, which was superior to hsCRP (cut-off=5 mg/l): specificity=95.8%, sensitivity=58.6%, a PPV=94.4%, a NPV=65.7%, AUC=0.885. In the subgroup, S100A8/A9 levels decreased after heart failure medication (T1: 2454±1931 ng/ml vs T2: 934.4±552 ng/ml; p=0.002), reflected by a decrease of EMB inflammatory cells. Baseline serum S100A8/A9 levels predicted the change in EMB CD3 and Mac-1. Conclusions These results support an additional value for S100A8/A9 serum levels as a potential diagnostic biomarker and as a tool to monitor the course of the disease. We provide first evidence that S100A8/A9 is connected to the NOD2-NLRP3 pathway in these patients. Acknowledgement/Funding Novartis

Background The aetiology of dilated cardiomyopathy (DCM) is highly heterogeneous including genetic and/or acquired (infective, toxic, immune, endocrine, and nutritional) factors. The major part of acquired DCM in developed countries is caused by either viral or autoimmune myocarditis. It is believed that the activation of the T-lymphocyte cell system is the major pathomechanism underlying autoimmune myocarditis and inflammatory DCM (DCMi). However, in the hearts of a subset of patients, a significant number of CD20+ B-lymphocytes can be detected too. Limited information exists on the role of B-cell-dependent mechanisms in the progression of DCMi. Particularly CD20+ B-lymphocytes, which can be targeted by anti-CD20+ B-lymphocytes antibodies or inhibitors, might contribute to the pathogenesis of myocardial damage beyond antibody production. Case summary Here, we present a case series of six patients with subacute and chronic endomyocardial biopsy-proven CD20+ B-lymphocyte-associated DCMi, where symptomatic heart failure therapy, with or without combined immunosuppressive therapy with steroid-based treatment regime, was insufficient to improve cardiac function. Five patients improved clinically several weeks after a standard infusion protocol with rituximab, a chimeric monoclonal antibody against the pan-B-cell surface molecule CD20. Discussion Our case series shows that CD20+ B-lymphocyte persistence can play a pathophysiologic role in a subset of DCMi patients and highlights the potential of targeting CD20+ B cells in patients with prominent CD20+ B-lymphocyte persistence.

Myocarditis is often associated with parvovirus B19 (B19V) persistence, which can induce vascular damage. Based on the antiviral and anti‐inflammatory properties of telbivudine, we aimed to evaluate its efficacy to protect B19V‐infected endothelial cells in vitro and to treat chronic lymphocytic myocarditis patients with B19V transcriptional activity.

Right ventricular (RV) dysfunction predicts adverse outcome in peripartum cardiomyopathy (PPCM). We recently demonstrated beneficial effects associated with the prolactin release inhibitor bromocriptine at different doses when added to standard heart failure therapy in PPCM. Here, we evaluated for the first time the therapeutic potential of bromocriptine particularly in PPCM patients with RV involvement.

Prediction of follow-up shock is crucial to stratify patients with dilated cardiomyopathy (DCM) requiring implantable cardioverter defibrillator (ICD). The objective of the article is to assess the predictive value of endo-myocardial biopsy (EMB) towards ICD shock and follow-up mortality. A series of patients with DCM scheduled for ICD implantation underwent EMB to further determine the genesis of DCM. Presence of fibrosis and inflammation was documented and related to outcomes. A total of 240 patients were referred for ICD as primary (56%) and secondary (44%) prophylaxis. EMB showed myocardial fibrosis in 55.4%, inflammation in 55.7%, and viral genomic material in 60%. Median follow-up was 39 months (1–209). Appropriate and inappropriate shocks occurred in 29.2 and 20.4%. At logistic regression, determinants of appropriate shock were ICD indication for secondary prophylaxis (direct relationship: p = 0.009, OR 3.4, CI 1.3–8.8) and presence of inflammation at EMB (inverse relationship: p = 0.04, OR 0.4, CI 0.1–0.9). Moreover, the sole determinant of inappropriate shock was age at implant (inverse relationship: p = 0.003, OR = 0.9, CI 0.90–0.98). Overall mean estimated survival was 168 months and 5-year survival was 83%. Degree of improvement in LVEF% was the sole determinant of follow-up mortality (inverse relationship p = 0.02; HR = 0.9; CI 0.88–0.99). Present selection criteria for ICDs implant rely mainly on LVEF% that lacks sensitivity and specificity. EMB can identify the substrate of increased or reduced life-threatening arrhythmias. Presence of inflammation is a positive prognostic factor for reduced arrhythmogenic risk, independently by the ICD implantation indication.

BACKGROUND:Recent clinical trials have shown that pulmonary artery pressure-guided therapy via the CardioMEMS™ system reduces the risk of recurrent hospitalizations in chronic heart failure (HF) patients. The CardioMEMS™ pressure sensor is percutaneously implanted in a branch of the pulmonary artery and allows telemetric pressure monitoring via a receiver. According to the most recent ESC guidelines, this technology has currently a class IIb indication in patients with class III New York Heart Association symptoms and a previous hospitalization for congestive heart failure within the last year, regardless of ejection fraction. Aim of this guided-therapy is multifold, including an early prediction of upcoming decompensation, optimization of patients' therapy and thereby avoidance of hospital admissions. In addition, it can be used during acute decompensation events as a novel tool to direct intra-hospital therapeutic interventions such as inotropes infusion or left ventricular (LV) assist device monitoring, with the aim of achieving an optimal volume status.CASE PRESENTATION:We present a case series of three end-stage HF patients with reduced ejection fraction (HFrEF) who received a CardioMEMS™ device as an aid in their clinical management. The CardioMEMS™ system enabled a closer non-invasive hemodynamic monitoring of these patients and guided the extent of therapeutic interventions. Patients were free from device- or system-related complications. In addition, no pressure-sensor failure was observed. Two patients received a 24-h infusion of the calcium sensitizer levosimendan. One patient showed a refractory acute decompensation and underwent LV assist device (LVAD) implantation as a bridge to cardiac transplantation. Switching a patient with recurrent hospitalizations to the Angiotensin Receptor Neprilysin Inhibitor (ARNI, Sacubitril-Valsartan) on top of the optimal heart failure-therapy improved its subjective condition and hemodynamics, avoiding further hospitalization.CONCLUSIONS:Our case series underlines the potential impact of CardioMEMS™ derived data in the daily clinical management of end-stage HF patients. The new concept to combine CardioMEMS™ in the setting of an outpatient levosimendan program as well as a bridge to LVAD-implantation/heart transplantation looks promising but needs further investigations.

Enteroviral cardiomyopathy is a life-threatening disease, and detection of enterovirus (EV) RNA in the initial endomyocardial biopsy is associated with adverse prognosis and increased mortality. Some patients with EV infection may spontaneously eliminate the virus and recover, whereas those with virus persistence deteriorate and progress to heart failure. Interferon-beta (IFN-β) therapy eliminates the virus, resulting in increased survival of treated patients. CCR5 is expressed on antigen-presenting cells (both macrophages and dendritic cells) and immune effector cells (T-lymphocytes with memory/effector phenotype and natural killer cells). Its 32-bp deletion (CCR5del32) is the most frequent human coding sequence mutation. This study addresses the correlation of CCR5 polymorphism to the clinical course of EV infection and the necessity for IFN-β treatment.

Background. Human parvovirus B19 (B19V) infection and damage of circulating angiogenic cells (CAC) results in dysfunctional endogenous vascular repair (DEVR) with secondary end-organ damage. Trafficking of CAC is regulated by SDF-1 alpha and the respective receptor CXCR4. We thus tested the hypothesis of a deregulated CXCR4/SDF-1 alpha axis in symptomatic B19V-cardiomyopathy. Methods CAC were infected in vitro with B19V and transfected with B19V-components. Read-out were: CXCR4-expression and migratory capacity at increasing doses of SDF-1 alpha. In 31 patients with chronic B19V-cardiomyopathy compared to 20 controls read-outs were from blood: migratory capacity, CXCR4 expression on CAC, serum SDF-1 alpha; from cardiac biopsies: SDF-1 alpha mRNA, HIF-1 alpha mRNA, microvascular density, resident cardiac stem cells (CSC), transcardiac gradients of CAC. Results In vitro B19V-infected CAC showed up-regulation of surface CXCR4 with increased migratory capacity further enhanced by elevated SDF-1 alpha concentrations. Overexpression of the B19V capsid protein VP2 was associated with this effect. Chronic B19V-cardiomyopathy patients showed increased numbers of ischaemia mobilised CAC but DEVR as well as diminished numbers of CAC after transcardiac passage. Cardiac microvascular density and CSC were significantly reduced in B19V-cardiomyopathy. Conclusions. We thus conclude that B19V infection has a direct VP2-mediated negative impact on trafficking of CAC in the presence of impaired cardiac regeneration.

Human herpesvirus-6A and B (HHV-6A, HHV-6B) have recently defined endogenous genomes, resulting from integration into the germline: chromosomally-integrated CiHHV-6A/B. These affect approximately 1.0% of human populations, giving potential for virus gene expression in every cell. We previously showed that CiHHV-6A was more divergent than CiHHV-6B by examining four genes in 44 European CiHHV-6A/B cardiac/haematology patients. There was evidence for gene expression/reactivation, implying functional non-defective genomes. To further define the relationship between HHV-6A and CiHHV-6A we used next-generation sequencing to characterize genomes from three CiHHV-6A cardiac patients. Comparisons to known exogenous HHV-6A showed CiHHV-6A genomes formed a separate clade; including all 85 non-interrupted genes and necessary cis-acting signals for reactivation as infectious virus. Greater single nucleotide polymorphism (SNP) density was defined in 16 genes and the direct repeats (DR) terminal regions. Using these SNPs, deep sequencing analyses demonstrated superinfection with exogenous HHV-6A in two of the CiHHV-6A patients with recurrent cardiac disease. Characterisation of the integration sites in twelve patients identified the human chromosome 17p subtelomere as a prevalent site, which had specific repeat structures and phylogenetically related CiHHV-6A coding sequences indicating common ancestral origins. Overall CiHHV-6A genomes were similar, but distinct from known exogenous HHV-6A virus, and have the capacity to reactivate as emerging virus infections.

La miocarditis se define como una enfermedad inflamatoria del músculo cardiaco y es una causa importante de insuficiencia cardiaca aguda, muerte súbita y miocardiopatía dilatada. Los virus son la causa de la mayoría de los casos de miocarditis o miocardiopatía inflamatoria y pueden inducir una respuesta inmunitaria causante de inflamación pese a haberse eliminado el patógeno. Otros agentes etiológicos causantes de miocarditis son los fármacos, las sustancias tóxicas o los trastornos autoinmunitarios. En los últimos años, los avances de técnicas no invasivas como la resonancia magnética cardiaca han sido de gran utilidad para respaldar el diagnóstico de miocarditis, pero los procesos tóxicos, infecciosos e inflamatorios, infiltrantes o autoinmunitarios se producen en las células, y solamente la biopsia endomiocárdica permite establecer la naturaleza del agente etiológico. Además, después de la generalización de las técnicas inmunohistoquímicas y de detección del genoma viral, la biopsia endomiocárdica proporciona un diagnóstico etiológico definitivo que puede conducir a tratamientos específicos como los antivirales o los inmunosupresores. No se realiza con frecuencia para el diagnóstico de miocarditis por razones de seguridad, pero la biopsia endomiocárdica, tanto derecha como izquierda, tiene una tasa de complicaciones muy baja cuando la realiza un operador experto. En este documento se presenta una revisión actualizada de la miocarditis y la miocardiopatía inflamatoria haciendo especial referencia al papel de la biopsia endomiocárdica para establecer un tratamiento específico.

Ziel dieser Studie war es die „first-pass“-Perfusion des Myokards semiquantitativ bei Patienten mit Verdacht auf Myokarditis mit der MRT zu beurteilen.

To analyze the long-term outcome after immunosuppressive treatment of patients with virus-negative chronic myocarditis or inflammatory cardiomyopathy (CMi).

Introduction: Nucleotide binding oligomerization domain 2 (NOD2) is a cytoplasmatic pattern recognition receptor belonging to the NOD-like receptor family, which is part of the innate immune system. Hypothesis: Since NOD2 recognises ssRNA and Coxsackievirus B3 (CVB3) is a ssRNA virus, we hypothesised that NOD2 regulates cardiac inflammatory signaling in CVB3-induced myocarditis. Methods: Gene expression was analyzed on endomyocardial biopsies (EMBs) taken from ejection fraction- and age-matched CVB3+ (n=10) and CVB3- control (n=7) patients and on EMBs from CVB3+patients who spontaneously eliminated CVB3 (n=6). NOD2 -/- mice and wild-type (wt) C57BL/6 mice were i.p. infected with 5 x 105 p.f.u. of CVB3. Seven days after infection, mice were hemodynamically characterized, and left ventricles (LV) were isolated. Results: NOD2 mRNA expression was 3.7-fold (p<0.05) increased in CVB3+ vs CVB3- control patients. Interestingly, NOD2 and Nrlp3 mRNA expression significantly dropped in EMBs of CVB3+ patients who spontaneously eliminated CVB3. In addition, LV NOD2 mRNA expession was increased in CVB3 vs wt mice. NOD2-/- CVB3 mice showed an improved LV function compared to CVB3 wt mice. In parallel, infiltration of CD4-, CD8-, CD11b- and CD68-positive cells was less pronounced in CVB3-infected NOD2-/- mice compared to CVB3 wt mice. Concomitantly, LV mRNA levels for TNF-alpha, IL-1ß, IFN-gamma, IFN-ß, TLR4, and MyD88 were 3.9-fold, 2.9-fold, 5.3-fold, 8.0-fold, 1.4-fold and 2.0-fold reduced in CVB3 NOD2-/- vs CVB3 wt mice, respectively (p<0.05). LV viral copy number was lower in CVB3 NOD2-/- vs CVB3 wt mice. CVB3-infected NOD2-/- mice exhibited less pronounced cardiac fibrosis, as indicated by lower collagen I and III mRNA expression and a 2.7-fold (p<0.0005) lower collagen I/III protein ratio. NOD2 knockdown in HL-1 cardiomyocytes was associated with a decreased inflammatory response, a 1.4-fold (p<0.05) lower CVB3 copy number, and a 3.4-fold (p<0.005) reduced TLR4 protein expression and underlying signaling. Conclusions: NOD2 knock down improves LV function and attenuates pathophysiological key mechanisms in acute CVB3-induced myocarditis mice. Modulation of NOD2 might represent a promising therapeutic strategy to treat viral myocarditis.