ArticlePDF Available

Human Parvovirus B19 (B19V) Up-regulates CXCR4 Surface Expression of Circulating Angiogenic Cells: Implications for Cardiac Ischemia in B19V Cardiomyopathy

Authors:

Abstract and Figures

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-1α and the respective receptor CXCR4. We thus tested the hypothesis of a deregulated CXCR4/SDF-1α 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-1α. In 31 patients with chronic B19V-cardiomyopathy compared to 20 controls read-outs were from blood: migratory capacity, CXCR4 expression on CAC, serum SDF-1α; from cardiac biopsies: SDF-1α mRNA, HIF-1α 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-1α 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.
No caption available
… 
No caption available
… 
Content may be subject to copyright.
A preview of the PDF is not available
... Although the majority of clinical disorders are generally self-limiting and subclinical [1], in certain cases, the disease may turn chronic and clinically relevant. The latter may result from either direct virus-mediated injury, increased apoptosis [2], inadequacy of the specific anti-viral immune response [3] or dysregulated trafficking of cells involved in endothelial regeneration [4]. ...
... CAC play a key role in cardiovascular regeneration [9]. B19V directly induces apoptosis of CAC through the viral proteins NS1, VP1 [2], and the small 11kDa protein and impairs their trafficking [4]. Among CAC, the so-called early outgrowth endothelial progenitor cells (eo-EPC) have been shown to parallel disease progression in atherosclerosis [10]. ...
... This was confirmed by Single PCR (n = 4, Figure 2B), that showed BIRC3 levels to be less downregulated when ECFC were pretreated with elbivudine before B19V infection. Having shown that B19V infection affects trafficking of CAC [4], we subsequently analysed the effect of telbivudine on angiogenic genes with an RT2 Profiler PCR array analysis for angiogenic genes (n = 1). We saw very little changes in a few other genes, so that we postulate a posttranscriptional effect of B19V on CXCR4. ...
Article
Full-text available
Aims: Human parvovirus B19 (B19V) infection directly induces apoptosis and modulates CXCR4 expression of infected marrow-derived circulating angiogenic cells (CACs). This leads to dysfunctional endogenous vascular repair. Treatment for B19V-associated disease is restricted to symptomatic treatment. Telbivudine, a thymidine analogue, established in antiviral treatment for chronic hepatitis B, modulates pathways that might influence induction of apoptosis. Therefore, we tested the hypothesis of whether telbivudine influences B19V-induced apoptosis of CAC. Methods and Results: Pretreatment of two CAC-lines, early outgrowth endothelial progenitor cells (eo-EPC) and endothelial colony-forming cells (ECFC) with telbivudine before in vitro infection with B19V significantly reduced active caspase-3 protein expression (−39% and −40%, both p < 0.005). Expression of Baculoviral Inhibitor of apoptosis Repeat-Containing protein 3 (BIRC3) was significantly downregulated by in vitro B19V infection in ECFC measured by qRT-PCR. BIRC3 downregulation was abrogated with telbivudine pretreatment (p < 0.001). This was confirmed by single gene PCR (p = 0.017) and Western blot analysis. In contrast, the missing effect of B19V on angiogenic gene expression postulates a post-transcriptional modulation of CXCR4. Conclusions: We for the first time show a treatment approach to reduce B19V-induced apoptosis. Telbivudine reverses B19V-induced dysregulation of BIRC3, thus, intervening in the apoptosis pathway and protecting susceptible cells from cell death. This approach could lead to an effective B19V treatment to reduce B19V-related disease.
... Previous clinical studies suggested that B19V presence determined by viral genomes is an unspecific bystander and may have no prognostic value in myocarditis and DCMi [12]. However, primarily experimental data suggest a relevant effect of B19V on the development of myocarditis and DCMi [13,14]. ...
Article
Full-text available
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.
... Furthermore, impaired endothelial regeneration and microvascular density were linked to myocardial B19V infection. In vitro infection of circulating angiogenic cells demonstrates B19V-dependent cellular damage and dysfunctional endogenous vascular repair [100]. In agreement, chronic B19V infection was associated with an impaired endothelial regenerative capacity [101]. ...
Article
Full-text available
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.
... . Endothelial dysfunction is a consequence of impaired endothelial regeneration during cardiac B19V infection, leading to impaired coronary microcirculation and results in secondary cardiac myocyte damage63,65,66 . Besides direct cytopathic effects, B19V potentially induces autoimmunity 67 possibly triggered by phospholipase activity of VP1u domain68,69 . ...
Article
Full-text available
Infection of the heart muscle with cardiotropic viruses is one of the major etiologies of myocarditis and acute and chronic inflammatory cardiomyopathy (DCMi). However, viral myocarditis and subsequent dilated cardiomyopathy (DCM) 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.
... Viral gene and protein expression are controlled by a combination of alternative splicing and internal polyadenylation [10][11][12][13]. Based on its strong erythroid tropism and related acute disease association, it has been shown that B19V is infecting erythroid endothelial progenitor cells and causes endothelial dysfunction in myocardial tissue [14][15][16]. Moreover, the presence of B19V remains a single independent predictor for reduced cardiac capillary density in patients with cardiomyopathy. ...
Article
Full-text available
Human parvovirus B19 (B19V) is the predominant cardiotropic virus associated with dilated inflammatory cardiomyopathy (DCMi). Transcriptionally active cardiotropic B19V infection is clinically relevant and triggers adverse long-term mortality. During the study; we evaluated whether antiviral treatment with the nucleoside analogue telbivudine (LTD) is effective in suppressing transcriptional active B19V in endomyocardial biopsies (EMBs) of B19V positive patients and improving clinical outcomes. Seventeen B19V-positive patients (13 male; mean age 45.7 ± 13.9 years; mean left ventricular ejection fraction (LVEF) 37.7 ± 13.5%) with positive B19V DNA and transcriptional activity (B19V mRNA) in EMBs were treated with 600 mg/d LTD over a period of six months. Patients underwent EMBs before and after termination of the LTD treatment. B19V RNA copy numbers remained unchanged in 3/17 patients (non-responder) and declined or disappeared completely in the remaining 14/17 patients (responder) (p ≤ 0.0001). Notably; LVEF improvement was more significant in patients who reduced or lost B19V RNA (responder; p = 0.02) in contrast to non-responders (p = 0.7). In parallel; responder patients displayed statistically significant improvement in quality of life (QoL) questionnaires (p = 0.03) and dyspnea on exertion (p = 0.0006), reflecting an improvement in New York Heart Association (NYHA) Classification (p = 0.001). Our findings demonstrated for the first time that suppression of B19V transcriptional activity by LTD treatment improved hemodynamic and clinical outcome significantly. Thus; the present study substantiates the clinical relevance of detecting B19V transcriptional activity of the myocardium.
... 21 The same authors further demonstrated that B19V infection has a direct VP2-mediated negative impact on trafficking of circulating angiogenic cells in the presence of impaired cardiac regeneration. 22 In addition, although the virus does not infect the cardiomyocytes, it is discussed that myocarditis can arise from immunological cross-reaction to epitopes shared between the virus and the myocardium, 23 indicating the need for the development of not only antiviral but also immunomodulatory interventions in patients with B19V-associated myocarditis. ...
Article
Full-text available
Aims 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. Methods and results We evaluated the endothelial‐protective potential of telbivudine in human microvascular endothelial cells‐1, which were infected with B19V. Treatment with 10 ng/mL of telbivudine decreased the B19V‐induced endothelial cell apoptosis and endothelial‐to‐mesenchymal transition. Along with this finding, telbivudine reduced the expression of transforming growth factor‐β1 and of tenascin‐C. The endothelial‐protective properties of telbivudine were also found in tumour necrosis factor‐α‐stressed human microvascular endothelial cells‐1. In addition, oxidative stress in angiotensin II‐stressed and transforming growth factor‐β1‐stressed HL‐1 cardiomyocytes and fibroblasts, respectively, was reduced upon telbivudine treatment, illustrating that telbivudine exerts multimodal protective effects. Based on these in vitro findings, four patients severely suffering from an endomyocardial biopsy‐proven myocarditis associated with B19V transcriptional activity (VP1/VP2‐mRNA positive) were treated with telbivudine (600 mg/dL) for 6 months in a single‐patient‐use approach. Follow‐up biopsies 6 months after treatment showed that VP1/VP2‐mRNA levels and CD3 cells decreased in all patients and were associated with an improvement in ejection fraction and New York Heart Association class. These findings were paralleled by a drop in tenascin‐C expression as shown via matrix‐assisted laser desorption ionization–imaging mass spectrometry. Conclusions Telbivudine exerts endothelial‐protective effects in B19V‐infected endothelial cells and improves chronic myocarditis associated with B19V transcriptional activity. These findings will be further evaluated in the clinical exploratory trial: the PreTopic study.
Chapter
Full-text available
Myocarditis is frequently associated with viral infections, a scenario that can progress to cardiomyopathy and sudden cardiac death. Viral infections contribute to myocardial damage via direct infection of the myocytes, cardiac endothelial damage, and cardiac ischemia, and/or may act as triggers of an autoimmune process. The definitive diagnosis of myocarditis relies on the detection of immune cell infiltrates and viral DNA/RNA in the endomyocardial biopsy (EMB) specimen. So far, only expert-based recommendations exist for the treatment of viral myocarditis, which depends also on the detection of viral genome and its type. Immunomodulatory therapies and some antivirals, e.g., direct against herpes viruses can be considered based on the EMB results, although their efficacies have not been fully evaluated. In this chapter, several antivirals proposed for virus-associated myocarditis/cardiomyopathy are critically reappraised.
Article
Full-text available
Introduction. Mesenchymal stromal cells (MSC) have immunomodulatory features. The aim of this study was to investigate the migration and homing potential of endogenous circulating MSC in virus negative inflammatory cardiomyopathy (CMi). Methods. In 29 patients with or without CMi undergoing endomyocardial biopsies (EMB), transcardiac gradients (TCGs) of circulating MSC were measured by flow cytometry from blood simultaneously sampled from aorta and coronary sinus. The presence of MSC in EMB, cardiac inflammation, and SDF-1α mRNA expression were detected via immunohistochemistry and real-time PCR. Results. MSC defined as CD45−CD34−CD11b−CD73+CD90+ cells accounted for 0.010 [0.0025-0.048]%/peripheral mononuclear cell (PMNC) and as CD45−CD34−CD11b−CD73+CD105+ cells for 0.019 [0.0026-0.067]%/PMNC, both with similar counts in patients with or without cardiac inflammation. There was a 29.9% transcardiac reduction of circulating MSC in patients with CMi, correlating with the extent of cardiac inflammation (, multivariate analysis). A strong correlation was found between the TCG of circulating MSC and numbers of MSC (CD45−CD34−CD90+CD105+) in EMB (, ). SDF-1α was the strongest predictor for increased MSC in EMB (, multivariate analysis). Conclusions. Endogenous MSC continuously migrate to the heart in patients with CMi triggered by cardiac inflammation.
Article
Full-text available
B19V is a common pathogen in microvascular disease and cardiomyopathy with infection of endothelial cells. B19V replication, however, is almost restricted to erythroid progenitor cells (ErPC). Endothelial regeneration attributable to bone marrow-derived circulating angiogenic cells (CAC) is a prerequisite for organ function. Due to many similarities of ErPC and CAC, we hypothesized B19V as perpetrator for impaired endogenous endothelial regeneration. B19V DNA and mRNA were quantified from endomyocardial biopsies (EMB), and bone marrow and circulating progenitor cells by PCR. Highest B19V DNA concentrations were found in CD34(+)KDR(+)-cells from 17 patients with chronic B19V cardiomyopathy. B19V replication intermediates could be detected in nearly half of the patients. Furthermore, chronic B19V infection was associated with impaired endothelial regenerative capacity. B19V infection of CAC in vitro resulted in expression of transcripts encoding B19V proteins. The capsid protein VP1 was identified as novel inducer of apoptosis in addition to non-structural proteins. Inhibition studies identified "death receptor" signalling with activation of caspases-8 and -10 to be responsible for apoptosis induction. B19V causally impaired endothelial regeneration with spreading of B19V in CAC in an animal model in vivo. We thus conclude that B19V infection and damage of CAC result in dysfunctional endogenous vascular repair supporting a primary bone marrow disease with secondary end-organ damage. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Article
Full-text available
Protein Z (PZ) is a vitamin K-dependent coagulation factor without catalytic activity. Evidence points towards PZ as an independent risk factor for the occurrence of human peripheral arterial disease. However, the role of PZ in ischemia-driven angiogenesis and vascular healing processes has not been elucidated so far. Angiogenic potency of PZ was assessed in established in vitro assays using endothelial cells. PZ-deficient (PZ-/-) mice and their wild-type littermates (PZ+/+) were subjected to hindlimb ischemia. Furthermore, PZ-/- mice were exposed to PZ expressing adenovirus (AdV-PZ) or control adenovirus (AdV-GFP). In an additional set of animals, PZ-/- mice were exposed to AdV-PZ and AdV-GFP, each in combination with the CXCR4 antagonist AMD3100. In vitro, PZ stimulated migratory activity and capillary-like tube formation of endothelial cells comparable to SDF-1. PZ-/- mice exhibited diminished hypoxia-driven neovascularization and reperfusion in post-ischemic hindlimbs, which was restored by adenoviral gene transfer up to levels seen in PZ+/+ mice. The stimulatory impact of PZ on endothelial cells in vitro was abolished by siRNA targeting against PZ and PZ was not able to restore reduced migration after knock-down of CXCR4. The increased surface expression of CXCR4 on PZ-stimulated endothelial cells and the abrogated restoration of PZ-/- mice via AdV-PZ after concomitant treatment with the CXCR4 antagonist AMD3100 supports the idea that PZ mediates angiogenesis via a G-protein coupled pathway and involves the SDF-1/CXCR4 axis. This is underlined by the fact that addition of the G-protein inhibitor PTX to PZ-stimulated endothelial cells abolished the effect of PZ on capillary-like tube formation. The results of the current study reveal a role of PZ in ischemia-induced angiogenesis, which involves a G-protein coupled pathway and a raised surface expression of CXCR4. Our findings thereby extend the involvement of PZ from the coagulation cascade to a beneficial modulation of vascular homeostasis.
Article
Full-text available
C-X-C motif chemokine 10 (CXCL10) also known as interferon γ-induced protein 10 kDa (IP-10) or small-inducible cytokine B10 is a cytokine belonging to the CXC chemokine family. CXCL10 binds CXCR3 receptor to induce chemotaxis, apoptosis, cell growth and angiostasis. Alterations in CXCL10 expression levels have been associated with inflammatory diseases including infectious diseases, immune dysfunction and tumor development. CXCL10 is also recognized as a biomarker that predicts severity of various diseases. A review of the emerging role of CXCL10 in pathogenesis of infectious diseases revealed diverse roles of CXCL10 in disease initiation and progression. The potential utilization of CXCL10 as a therapeutic target for infectious diseases is discussed.
Article
Full-text available
Ultrasound-targeted microbubble destruction (UTMD) uses ultrasound energy to selectively deliver genes into the myocardium using plasmids conjugated to microbubbles. We hypothesized that repeated delivery of stem cell-mobilizing genes could boost the ability of this therapy to enhance cardiac repair and ventricular function after a myocardial infarction. Beginning 7 days after coronary artery ligation, stem cell factor (SCF) and stromal cell-derived factor (SDF)-1α genes were administered to adult rats using 1, 3, or 6 UTMD treatments (repeat 1, 3, and 6 groups) at 2-day intervals (control=6 treatments with empty plasmid). Cardiac function (echocardiography) and myocardial perfusion (myocardial contrast echocardiography) were assessed on Days -7, 0, and 24 relative to the first treatment. Histological and biochemical assessments were performed on Day 24. Multiple UTMD treatments were associated with an increased presence of myocardial SCF and SDF-1α proteins and their receptors (vs. control and Repeat 1). All UTMD recipients exhibited increased vascular densities and smaller infarct regions (vs. control), with the highest ventricular densities in response to multiple treatments. Myocardial perfusion and ventricular function at Day 24 also improved progressively (vs. control) with the number of UTMD treatments. Targeted ultrasound delivery of SCF and SDF-1α genes to the infarcted myocardium recruited progenitor cells and increased vascular density. Multiple UTMD treatments enhanced tissue repair, perfusion, and cardiac function. Repeated UTMD therapy may be applied to tailor the number of interventions required to optimize cardiac regeneration after an infarction.
Article
Use of the real-time polymerase chain reaction (PCR) to amplify cDNA products reverse transcribed from mRNA is on the way to becoming a routine tool in molecular biology to study low abundance gene expression. Real-time PCR is easy to perform, provides the necessary accuracy and produces reliable as well as rapid quantification results. But accurate quantification of nucleic acids requires a reproducible methodology and an adequate mathematical model for data analysis. This study enters into the particular topics of the relative quantification in real-time RT-PCR of a target gene transcript in comparison to a reference gene transcript. Therefore, a new mathematical model is presented. The relative expression ratio is calculated only from the real-time PCR efficiencies and the crossing point deviation of an unknown sample versus a control. This model needs no calibration curve. Control levels were included in the model to standardise each reaction run with respect to RNA integrity, sample loading and inter-PCR variations. High accuracy and reproducibility (<2.5% variation) were reached in LightCycler PCR using the established mathematical model.
Article
Stromal cell-derived factor-1 (SDF-1) is a CXC chemokine produced by stromal cells that acts as a chemoattractant for human CD34+ progenitor cells. We investigated the expression of CXCR4, the receptor for SDF-1, on CD34+ cells from different hematopoietic sites and developmental stages. CXCR4 was detected by flow cytometry on 37 % of fetal bone marrow (BM) [gestation weeks (gw) 14 – 23] and 40 % of adult BM CD34+ cells. Interestingly, in fetal liver CD34+ cells, CXCR4 was expressed at lower levels at later stages (9 %, gw 20 – 23) compared to early stages of development (39 %, gw 7.5 – 18), suggesting a development-related change in the migratory capacity of progenitors. CXCR4 was detected at similar levels on both phenotypically primitive and committed progenitors from fetal and adult sites. However, B cell lineage progenitor and precursor cells expressed CXCR4 at the highest density (80 % of BM CD34+/CD10+ pro-B cells are CXCR4+). CXCR4 was also expressed in the fetal thymus in early T cell precursors and found to be down-regulated during T cell maturation. Finally, we found that stem cell factor, alone or in combination with other cytokines, can up-modulate CXCR4 expression on CD34+ cells by three- to fourfold. In conclusion, our results suggest that CXCR4 may play an important role in the local and systemic trafficking of human CD34+ cells as well as in human B lymphopoiesis and that its expression can be modulated by cytokines.
Article
Diverse subsets of endothelial progenitor cells (EPCs) are used for the treatment of ischemic diseases in clinical trials, and circulating EPCs levels are considered as biomarkers for coronary and peripheral artery disease. However, despite significant steps forward in defining their potential for both therapeutic and diagnostic purposes, further progress has been mired by unresolved questions around the definition and the mechanism of action of EPCs. Diverse culturing methods and detection of various combinations of different surface antigens were used to enrich and identify EPCs. These attempts were particularly challenged by the close relationship and overlapping markers of the endothelial and hematopoietic lineages. This article will critically review the most commonly used protocols to define EPCs by culture assays or by fluorescence-activated cell sorter in the context of their therapeutic or diagnostic use. We also delineate new research avenues to move forward our knowledge on EPC biology.
Article
RETRACTION This article has been retracted: Circ Res . 2018;123:e00. DOI: 10.1161/RES.0000000000000248.
Article
Human parvovirus B19 (B19V) DNA is highly prevalent in endothelial cells lining up intramyocardial arterioles and postcapillary venules of patients with chronic myocarditis and cardiomyopathies. We addressed the question of a possible stimulation of B19V gene expression in endothelial cells by infection with adenoviruses. Adenovirus infection led to a strong augmentation of B19V structural and nonstructural proteins in individual endothelial cells infected with B19V or transfected with an infectious B19V genome. Transactivation was mostly mediated at the level of transcription and not due to adenovirus-mediated induction of second-strand synthesis from the single-stranded parvoviral genome. The main adenoviral functions required were E1A and E4orf6, which displayed synergistic effects. Furthermore, a limited B19V genome replication could be demonstrated in endothelial cells and adenovirus infection induced the appearance of putative dimeric replication intermediates. Thus the almost complete block in B19V gene expression seen in endothelial cells can be abrogated by infection with other viruses.