A Novel Murine Model of Parvovirus Associated Dilated Cardiomyopathy Induced by Immunization with VP1-Unique Region of Parvovirus B19

Genetic Ablation of Ankrd1 Mitigates Cardiac Damage during Experimental Autoimmune Myocarditis in Mice

Myocarditis (MC) is an inflammatory disease of the myocardium that can cause sudden death in the acute phase, and dilated cardiomyopathy (DCM) with chronic heart failure as its major long-term outcome. However, the molecular mechanisms beyond the acute MC phase remain poorly understood. The ankyrin repeat domain 1 (ANKRD1) is a functionally pleiotropic stress/stretch-inducible protein, which can modulate cardiac stress response during various forms of pathological stimuli; however, its involvement in post-MC cardiac remodeling leading to DCM is not known. To address this, we induced experimental autoimmune myocarditis (EAM) in ANKRD1-deficient mice, and evaluated post-MC consequences at the DCM stage mice hearts. We demonstrated that ANKRD1 does not significantly modulate heart failure; nevertheless, the genetic ablation of Ankrd1 blunted the cardiac damage/remodeling and preserved heart function during post-MC DCM.

Transcriptional Active Parvovirus B19 Infection Predicts Adverse Long-Term Outcome in Patients with Non-Ischemic Cardiomyopathy

Parvovirus B19 (B19V) is the predominant cardiotropic virus currently found in endomyocardial biopsies (EMBs). However, direct evidence showing a causal relationship between B19V and progression of inflammatory cardiomyopathy are still missing. The aim of this study was to analyze the impact of transcriptionally active cardiotropic B19V infection determined by viral RNA expression upon long-term outcomes in a large cohort of adult patients with non-ischemic cardiomyopathy in a retrospective analysis from a prospective observational cohort. In total, the analyzed study group comprised 871 consecutive B19V-positive patients (mean age 50.0 ± 15.0 years) with non-ischemic cardiomyopathy who underwent EMB. B19V-positivity was ascertained by routine diagnosis of viral genomes in EMBs. Molecular analysis of EMB revealed positive B19V transcriptional activity in n = 165 patients (18.9%). Primary endpoint was all-cause mortality in the overall cohort. The patients were followed up to 60 months. On the Cox regression analysis, B19V transcriptional activity was predictive of a worse prognosis compared to those without actively replicating B19V (p = 0.01). Moreover, multivariable analysis revealed transcriptional active B19V combined with inflammation [hazard ratio 4.013, 95% confidence interval 1.515–10.629 (p = 0.005)] as the strongest predictor of impaired survival even after adjustment for age and baseline LVEF (p = 0.005) and independently of viral load. The study demonstrates for the first time the pathogenic clinical importance of B19V with transcriptional activity in a large cohort of patients. Transcriptionally active B19V infection is an unfavourable prognostic trigger of adverse outcome. Our findings are of high clinical relevance, indicating that advanced diagnostic differentiation of B19V positive patients is of high prognostic importance.

Viral Myocarditis-From Pathophysiology to Treatment

The diagnosis of acute and chronic myocarditis remains a challenge for clinicians. Characterization of this disease has been hampered by its diverse etiologies and heterogeneous clinical presentations. Most cases of myocarditis are caused by infectious agents. Despite successful research in the last few years, the pathophysiology of viral myocarditis and its sequelae leading to severe heart failure with a poor prognosis is not fully understood and represents a significant public health issue globally. Most likely, at a certain point, besides viral persistence, several etiological types merge into a common pathogenic autoimmune process leading to chronic inflammation and tissue remodeling, ultimately resulting in the clinical phenotype of dilated cardiomyopathy. Understanding the underlying molecular mechanisms is necessary to assess the prognosis of patients and is fundamental to appropriate specific and personalized therapeutic strategies. To reach this clinical prerequisite, there is the need for advanced diagnostic tools, including an endomyocardial biopsy and guidelines to optimize the management of this disease. The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) has currently led to the worst pandemic in a century and has awakened a special sensitivity throughout the world to viral infections. This work aims to summarize the pathophysiology of viral myocarditis, advanced diagnostic methods and the current state of treatment options.

Cardiovascular consequences of viral infections: from COVID to other viral diseases

Infection of the heart muscle with cardiotropic viruses is one of the major aetiologies of myocarditis and acute and chronic inflammatory cardiomyopathy (DCMi). However, viral myocarditis and subsequent dilated cardiomyopathy is still a challenging disease to diagnose and to treat and is therefore a significant public health issue globally. Advances in clinical examination and thorough molecular genetic analysis of intramyocardial viruses and their activation status have incrementally improved our understanding of molecular pathogenesis and pathophysiology of viral infections of the heart muscle. To date, several cardiotropic viruses have been implicated as causes of myocarditis and DCMi. These include, among others, classical cardiotropic enteroviruses (Coxsackieviruses B), the most commonly detected parvovirus B19, and human herpes virus 6. A newcomer is the respiratory virus that has triggered the worst pandemic in a century, SARS-CoV-2, whose involvement and impact in viral cardiovascular disease is under scrutiny. Despite extensive research into the pathomechanisms of viral infections of the cardiovascular system, our knowledge regarding their treatment and management is still incomplete. Accordingly, in this review, we aim to explore and summarize the current knowledge and available evidence on viral infections of the heart. We focus on diagnostics, clinical relevance and cardiovascular consequences, pathophysiology, and current and novel treatment strategies.

Effect of N‑terminal region of human parvovirus B19‑VP1 unique region on cardiac injury in naïve mice

A unique region of human parvovirus B19 virus-VP1 (B19V–VP1u) has been linked to a variety of cardiac disorders. However, the precise role of B19V–VP1u in inducing cardiac injury remains unknown. The present study investigated the effects of B19V–VP1u and different regions of B19V–VP1u, including B19V–VP1uA (residues 1–60), B19V–VP1uB (residues 61–129), B19V–VP1uC (residues 130–195) and B19V–VP1uD (residues 196–227), on inducing cardiac injury in naïve mice by zymography, immunoblotting, H&E staining and cytokine immunoassay. A significantly higher MMP-9/MMP-2 ratio and increased levels of inflammatory cytokines, including IL-6 and IL-1β, were detected in the left ventricles of the mice injected with B19V-non-structural protein 1 (B19V-NS1) and B19V–VP1u, accompanied by increased expression levels of phosphorylated (p-)ERK and p-P38. Significantly upregulated expression levels of atrial natriuretic peptide (ANP), heart-type fatty acid-binding protein (H-FABP) and creatine kinase isoenzyme-MB (CK-MB), which are well-known cardiac injury markers, as well as increased infiltration of lymphocytes, were detected in the left ventricles of the mice injected with B19V–VP1, B19V-NS1 and B19V–VP1u. Moreover, a significantly higher MMP-9/MMP-2 ratio and increased levels of IL-6 and IL-1β were observed in the left ventricles of the mice injected with B19V–VP1u, B19V–VP1u-A, B19V–VP1u-B and B19V–VP1u-C, accompanied by upregulated p-ERK and p-P38 expression. Notably, significantly lower levels of IL-6 and IL-1β were observed in the left ventricles of the mice injected with B19V–VP1uD. Furthermore, significantly increased ANP, H-FABP and CK-MB expression levels were detected in the left ventricles of the mice injected with B19V–VP1u, B19V–VP1u-A and B19V–VP1u-B, along with enhanced infiltration of lymphocytes. Significantly higher serum IL-1β, IL-6, TNF-α and IFN-γ levels were also detected in the mice injected with B19V–VP1u, B19V–VP1u-A and B19V–VP1u-B. To the best of our knowledge, the findings of the present study were the first to demonstrate that the N-terminal region (residues 1–129) of B19V–VP1u induces an increase in the levels of cardiac injury markers, thus providing evidence for understanding the possible functional regions within B19V–VP1u.

An overview of the immune mechanisms of viral myocarditis

Viral myocarditis has been identified as a major cause of dilated cardiomyopathy (DCM) that can lead to heart failure. Historically, Coxsackieviruses and adenoviruses have been commonly suspected in myocarditis/DCM patients in North America and Europe. However, this notion is changing as other viruses such as Parvovirus B19 and human herpesvirus-6 are increasingly reported as causes of myocarditis in the United States, with the most recent example being the severe acute respiratory syndrome coronavirus 2, causing the Coronavirus Disease-19. The mouse model of Coxsackievirus B3 (CVB3)-induced myocarditis, which may involve mediation of autoimmunity, is routinely used in the study of immune pathogenesis of viral infections as triggers of DCM. In this review, we discuss the immune mechanisms underlying the development of viral myocarditis with an emphasis on autoimmunity in the development of post-infectious myocarditis induced with CVB3.

Retrospective Study of Intercalated Disk Defects Associated with Dilated Cardiomyopathy, Atrial Thrombosis, and Heart Failure in BALB/c Mice Deficient in IL4 Receptor α

An increased incidence of dilated cardiomyopathy and atrial thrombosis was noted in a breeding colony of BALB/c mice deficient in IL4 receptor α. The condition affected mice of both sexes and of various ages, and extensive testing (microbiology, serology, histopathology) failed to ascertain the cause. Transmission electron microscopy of heart samples showed structural defects in the myocardial intercalated disks, characterized by unorganized and heavily convoluted arrangement with lower density and less prominent desmosomes and adherens junctions, widening of the intercellular space, myofibrillar lysis adjacent to intercalated disks, occasional sarcomere lysis with marked myofiber degeneration, vacuolation, accumulation of cell debris, and myelin figures. The intercalated disk contains cell adhesion molecules that form cell junctions, allowing contraction coupling of cardiomyocytes and the electrical and mechanical connection between cardiac fibers. Thus, defects at this level result in poor myocardial contraction, intracardiac blood stagnation, and consequently cardiac dilation with clinical signs of heart failure. The background strain or, potentially, the Cre-loxP-mediated recombination system used to create these mice may have contributed to the elevated incidence of cardiomyopathy and atrial thrombosis in this colony. Due to the backcrossing breeding scheme used, we cannot discount the emergence and colonywide dissemination of a spontaneous mutation that affects the intercalated disk. This report underscores the importance of carefully monitoring genetically modified mice colonies for unexpected phenotypes that may result from spontaneous or unintended mutations or enhanced strain background pathology.

The effects of human parvovirus VP1 unique region in a mouse model of allergic asthma

Evidence has indicated that viral infection increases the risk of developing asthma. Although the association of human parvovirus B19 (B19V) or human bocavirus (HBoV) with respiratory diseases has been reported, little is known about the influence of the B19V-VP1u and HBoV-VP1u proteins on the symptoms of asthma. Herein, we investigated the systemic influence of subcutaneously injected B19V-VP1u and HBoV-VP1u recombinant proteins in an OVA-sensitized asthmatic mouse model. A significantly higher Penh ratio and IgE level were detected in the serum, bronchoalveolar lavage fluid (BALF) and the supernatant of a lymphocyte culture from mice treated with HBoV-VP1u or B19V-VP1u than in a lymphocyte culture from OVA-sensitized mice. Significantly higher levels of serum and BALF IgE, total IgG, IgG1, OVA-specific IgE and OVA-specific IgG1 were detected in mice treated with HBoV-VP1u or B19V-VP1u than in OVA-sensitized mice. Conversely, a significantly lower IgG2a level was detected in mice from the HBoV-VP1u or B19V-VP1u groups than in mice from the OVA group. The mice treated with HBoV-VP1u or B19V-VP1u exhibited more significant lung inflammatory indices, including elevated serum and BALF IL-4, IL-5, IL-10 and IL-13 levels; BALF lymphocyte, neutrophil and eosinophil counts, MMP-9 and MMP-2 activity; and the amount of lymphocyte infiltration, relative to those in the control mice or in those sensitized with OVA. These findings demonstrate that the subcutaneous injection of HBoV-VP1u or B19V-VP1u proteins in OVA-sensitized mice result in elevated asthmatic indices and suggest that human parvoviruses may increase the risk of developing airway inflammation in a mouse model of asthma.

Selective activation of inflammation factors by human parvovirus B19 and human bocavirus VP1 unique region on H9c2 cardiomyocyte

Human parvovirus B19 (B19) and human bocavirus 1 (HBoV) are the only known pathogenic parvoviruses, and are responsible for a variety of diseases in human beings. Mounting evidence indicates a strong association between B19 infection and cardiac disorders including myocarditis, dilated cardiomyopathy and heart failure. However, very limited information about the role of HBoV in cardiac disorders is known. To elucidate the effects of B19 and HBoV on cardiac disorders, we expressed EGFP‑conjugate constructs of B19‑VP1 unique region (VP1u) and HBoV‑VP1u, along with the mutants EGFP‑B19‑VP1uD175A and EGFP‑HBoV‑VP1uV12A, in H9c2 cells by stable transfection. The protein expression levels of EGFP, EGFP‑B19‑VP1u, EGFP‑B19‑VP1uD175A, EGFP‑HBoV‑VP1u and EGFP‑HBoV‑VP1uV12A in H9c2 cells were observed under a fluorescence microscope and confirmed by western blotting. Secreted phospholipase A2 (sPLA2) activity was detected in B19‑VP1u and HBoV‑VP1u but not B19‑VP1uD175A and HBoV‑VP1uV12A recombinant proteins. Significantly higher expression levels of MCP2 and IP‑10 mRNA were detected in H9c2 cells that were transfected with pEGFP‑B19‑VP1u, compared with in those cells transfected with pEGFP‑HBoV‑VP1u, pEGFP‑B19‑VP1uD175A or pEGFP‑HBoV‑VP1uV12A. Significantly higher protein levels of IL‑1β and IL‑6 were detected in H9c2 cells transfected with pEGFP‑B19‑VP1u or pEGFP‑HBoV‑VP1u, compared with in those cells transfected with pEGFP‑B19‑VP1uD175A or pEGFP‑HBoV‑VP1uV12A. Notably, significantly higher expression of both TNF‑α and NF‑κB was observed only in H9c2 cells transfected with pEGFP‑B19‑VP1u, but not in those cells transfected with pEGFP‑HBoV‑VP1u, pEGFP‑B19‑VP1uD175A or pEGFP‑HBoV‑VP1uV12A. These findings, to our knowledge for the first time, reveal the difference between B19‑VP1u and HBoV‑VP1u in H9c2 cells and provide insight into the roles of B19‑VP1u and HBoV‑VP1u in the pathogenesis of cardiac inflammation.