Ganciclovir and cidofovir treatment of cytomegalovirus-induced myocarditis in mice

The inflammatory spectrum of cardiomyopathies

Infiltration of the myocardium with various cell types, cytokines and chemokines plays a crucial role in the pathogenesis of cardiomyopathies including inflammatory cardiomyopathies and myocarditis. A more comprehensive understanding of the precise immune mechanisms involved in acute and chronic myocarditis is essential to develop novel therapeutic approaches. This review offers a comprehensive overview of the current knowledge of the immune landscape in cardiomyopathies based on etiology. It identifies gaps in our knowledge about cardiac inflammation and emphasizes the need for new translational approaches to improve our understanding thus enabling development of novel early detection methods and more effective treatments.

Myocardial Function in Fetuses with Congenital Cytomegalovirus Infection

INTRODUCTION

The objective of this study was to investigate myocardial deformation of left (LV) and right ventricle (RV) using 2-dimensional speckle-tracking echocardiography (2D-STE) in fetuses with and without congenital cytomegalovirus (CMV) infection.

METHODS

This was a prospective single-center study. Vertical transmission was defined by a positive CMV polymerase chain reaction (PCR) test on the amniotic fluid or on the neonate's urine. Fetuses were divided into group 1 and group 2 if CMV-PCR was positive or negative, respectively. LV and RV global longitudinal strain (GLS) values were obtained and adjusted for gestational age by calculating Z-scores. Univariate analysis was carried out to compare cardiac indices between group 1 and group 2.

RESULTS

Fetuses from group 1 (n = 11) had a significantly lower LV myocardial shortening than those from group 2 (n = 32). GLS was -20.7 ± 5.2% and -26.3 ± 4.1%, respectively (p = 0.001). Similarly, GLS Z-score was lower (0.02 ± 0.72) in group 1 than in group 2 (-0.80 ± 0.59) (p = 0.001). Similarly, RV GLS Z-score was significantly impaired in group 1 compared to group 2 (-0.44 ± 1.03 vs. -1.04 ± 0.71, p = 0.041).

CONCLUSION

Fetuses with congenital CMV showed subclinical biventricular myocardial dysfunction. Further studies are needed to confirm the potential role of 2D-STE in identifying fetuses with congenital CMV at risk of postnatal cardiovascular morbidities.

Myocarditis: causes, mechanisms, and evolving therapies

INTRODUCTION

Myocarditis is a severe lymphocyte-mediated inflammatory disorder of the heart, mostly caused by viruses and immune checkpoint inhibitors (ICIs). Recently, myocarditis as a rare adverse event of mRNA vaccines for SARS-CoV-2 has caused global attention. The clinical consequences of myocarditis can be very severe, but specific treatment options are lacking or not yet clinically proven.

AREAS COVERED

This paper offers a brief overview of the biology of viruses that frequently cause myocarditis, focusing on mechanisms important for viral entry and replication following host infection. Current and new potential therapeutic targets/strategies especially for viral myocarditis are reviewed systematically. In particular, the immune system in myocarditis is dissected with respect to infective viral and non-infective, ICI-induced myocarditis.

EXPERT OPINION

Vaccination is an excellent emerging preventative strategy for viral myocarditis, but most vaccines still require further development. Anti-viral treatments that inhibit viral replication need to be considered following viral infection in host myocardium, as lower viral load reduces inflammation severity. Understanding how the immune system continues to damage the heart even after viral clearance will define novel therapeutic targets/strategies. We propose that viral myocarditis can be best treated using a combination of antiviral agents and immunotherapies that control cytotoxic T cell activity.

Disruption of thymic central tolerance by infection with murine roseolovirus induces autoimmune gastritis

Infections with herpesviruses, including human roseoloviruses, have been proposed to cause autoimmune disease, but defining a causal relationship and mechanism has been difficult due to the ubiquitous nature of infection and development of autoimmunity long after acute infection. Murine roseolovirus (MRV) is highly related to human roseoloviruses. Herein we show that neonatal MRV infection induced autoimmune gastritis (AIG) in adult mice in the absence of ongoing infection. MRV-induced AIG was dependent on replication during the neonatal period and was CD4+ T cell and IL-17 dependent. Moreover, neonatal MRV infection was associated with development of a wide array of autoantibodies in adult mice. Finally, neonatal MRV infection reduced medullary thymic epithelial cell numbers, thymic dendritic cell numbers, and thymic expression of AIRE and tissue-restricted antigens, in addition to increasing thymocyte apoptosis at the stage of negative selection. These findings strongly suggest that infection with a roseolovirus early in life results in disruption of central tolerance and development of autoimmune disease.

Don't Go Breaking My Heart: MCMV as a Model for HCMV-Associated Cardiovascular Diseases

Human Cytomegalovirus (HCMV) is a widespread pathogen that causes lifelong latent infection and is associated with the exacerbation of chronic inflammatory diseases in seropositive individuals. Of particular impact, HCMV infection is known to worsen many cardiovascular diseases including myocarditis, atherosclerosis, hypertension, and transplant vasculopathy. Due to its similarity to HCMV, murine CMV (MCMV) is an appropriate model to understand HCMV-induced pathogenesis in the heart and vasculature. MCMV shares similar sequence homology and recapitulates much of the HCMV pathogenesis, including HCMV-induced cardiovascular diseases. This review provides insight into HCMV-associated cardiovascular diseases and the murine model of MCMV infection, which has been used to study the viral pathogenesis and mechanisms contributing to cardiovascular diseases. Our new functional studies using echocardiography demonstrate tachycardia and hypertrophy in the mouse, similar to HCMV-induced myocarditis in humans. For the first time, we show long term heart dysfunction and that MCMV reactivates from latency in the heart, which raises the intriguing idea that HCMV latency and frequent virus reactivation perturbs long term cardiovascular function.

Heart Dysfunction Following Long-Term Murine Cytomegalovirus Infection: Fibrosis, Hypertrophy, and Tachycardia

Human cytomegalovirus (HCMV) is associated with increased risk of chronic diseases of the heart and vasculature, including myocarditis, atherosclerosis, and transplant vasculopathy. To investigate CMV infection of the heart, murine cytomegalovirus (MCMV) was used to evaluate both acute and latent infection and the subsequent phenotypic and functional consequences of infection. Female BALB/c mice were intraperitoneally (i.p.) inoculated with 1 × 106 pfu of MCMV and evaluated at 14 and 50 days postinfection (dpi). At each time point, echocardiography was used to evaluate cardiac function and histology was conducted for phenotypic evaluation. MCMV replication in the heart was detected as early as 3 dpi and was no longer detectable at 14 dpi. Infected animals had significant cardiac pathology at 14 and 50 dpi when compared to uninfected controls. Histology revealed fibrosis of the heart as early as 14 dpi and the presence of white fibrous deposits on the surface of the heart. Functional evaluation showed significantly increased heart rate and muscle thickening in the latently infected animals when compared to the control animals. At 50 dpi, latent virus was measured by explant reactivation assay, demonstrating that MCMV establishes latency and is capable of reactivation from the heart, similar to other tissues such as spleen and salivary glands. Collectively, these studies illustrate that MCMV infection results in phenotypic alterations within the heart as early as 14 dpi, which progress to functional abnormalities during latency. These findings are similar to sinus tachycardia and hypertrophy of the heart muscle observed in cases of HCMV-induced acute myocarditis.

Caspase-8 restricts antiviral CD8 T cell hyperaccumulation

The magnitude of CD8 T cell responses against viruses is checked by the balance of proliferation and death. Caspase-8 (CASP8) has the potential to influence response characteristics through initiation of apoptosis, suppression of necroptosis, and modulation of cell death-independent signal transduction. Mice deficient in CASP8 and RIPK3 (Casp8 ^-/- Ripk3 ^-/- ) mount enhanced peak CD8 T cell levels against the natural mouse pathogen murine cytomegalovirus (MCMV) or the human pathogen herpes simplex virus-1 compared with littermate control RIPK3-deficient or WT C57BL/6 mice, suggesting an impact of CASP8 on the magnitude of antiviral CD8 T cell expansion and not on contraction. The higher peak response to MCMV in Casp8 ^-/- Ripk3 ^-/- mice resulted from accumulation of greater numbers of terminally differentiated KLRG1^hi effector CD8 T cell subsets. Antiviral Casp8 ^-/- Ripk3 ^-/- T cells exhibited enhanced proliferation when splenocytes were transferred into WT recipient mice. Thus, cell-autonomous CASP8 normally restricts CD8 T cell proliferation following T cell receptor activation in response to foreign antigen. Memory inflation is a hallmark quality of the T cell response to cytomegalovirus infection. Surprisingly, MCMV-specific memory inflation was not sustained long-term in Casp8 ^-/- Ripk3 ^-/- mice even though these mice retained immunity to secondary challenge. In addition, the accumulation of abnormal B220⁺CD3⁺ T cells in these viable CASP8-deficient mice was reduced by chronic MCMV infection. Combined, these data brings to light the cell death-independent role of CASP8 during CD8 T cell expansion in mice lacking the confounding impact of RIPK3-mediated necroptosis.

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.

Pharmacokinetics and tissue diffusion of ganciclovir in mice and rats

BACKGROUND

Congenital cytomegalovirus (CMV) infection is the leading infectious cause of birth defects, mental retardation and non-genetic sensorineural hearing loss. Murine models have been developed in order to understand the pathophysiological mechanisms underlying these lesions. These models are being proposed for the validation of therapeutic protocols for clinical use. The aim of this preclinical study was to assess the pharmacokinetics of the reference antiviral molecule, ganciclovir, in order to optimize these protocols and confirm the diffusion of the molecule to the appropriate target zones.

METHODS

Transplacental and intracochlear diffusion of ganciclovir was evaluated in mice and rats. Pharmacokinetics was assessed in adult mice and pups after 5 consecutive days of intraperitoneal injection of ganciclovir. The occurrence of hematological side effects of ganciclovir was evaluated in the different blood cell lineages.

RESULTS

In adult rats, the intracochlear diffusion of ganciclovir was shown to achieve the same concentration as in blood. In gestating mice, transplacental diffusion was observed, with a fetal-to-maternal blood ratio of 0.5. In newborn mice, the plasma concentration profile of ganciclovir showed a peak at 2 h followed by a gradual decrease. In adult mice, the concentration peaked at 1 h, but became undetectable by 2 h after injection. Counts of white blood cells, red blood cells and platelets decreased significantly in ganciclovir-treated newborn mice.

CONCLUSION

Our data provide evidence for the intracochlear diffusion of the molecule, which may be relevant for the treatment of sensorineural hearing loss in congenitally-infected children.

Macrophage activation associated with chronic murine cytomegalovirus infection results in more severe experimental choroidal neovascularization

The neovascular (wet) form of age-related macular degeneration (AMD) leads to vision loss due to choroidal neovascularization (CNV). Since macrophages are important in CNV development, and cytomegalovirus (CMV)-specific IgG serum titers in patients with wet AMD are elevated, we hypothesized that chronic CMV infection contributes to wet AMD, possibly by pro-angiogenic macrophage activation. This hypothesis was tested using an established mouse model of experimental CNV. At 6 days, 6 weeks, or 12 weeks after infection with murine CMV (MCMV), laser-induced CNV was performed, and CNV severity was determined 4 weeks later by analysis of choroidal flatmounts. Although all MCMV-infected mice exhibited more severe CNV when compared with control mice, the most severe CNV developed in mice with chronic infection, a time when MCMV-specific gene sequences could not be detected within choroidal tissues. Splenic macrophages collected from mice with chronic MCMV infection, however, expressed significantly greater levels of TNF-α, COX-2, MMP-9, and, most significantly, VEGF transcripts by quantitative RT-PCR assay when compared to splenic macrophages from control mice. Direct MCMV infection of monolayers of IC-21 mouse macrophages confirmed significant stimulation of VEGF mRNA and VEGF protein as determined by quantitative RT-PCR assay, ELISA, and immunostaining. Stimulation of VEGF production in vivo and in vitro was sensitive to the antiviral ganciclovir. These studies suggest that chronic CMV infection may serve as a heretofore unrecognized risk factor in the pathogenesis of wet AMD. One mechanism by which chronic CMV infection might promote increased CNV severity is via stimulation of macrophages to make pro-angiogenic factors (VEGF), an outcome that requires active virus replication.

Ganciclovir transiently attenuates murine cytomegalovirus-associated renal allograft inflammation

BACKGROUND

Prophylactic ganciclovir (GCV) is used in high-risk renal transplant patients to prevent acute cytomegalovirus (CMV) disease, but its impact on inflammation within the allograft itself remains undefined.

METHODS

To study the effect of GCV prophylaxis on allograft inflammation, murine CMV (MCMV)-infected allografts were analyzed in a murine donor positive/recipient negative allogeneic renal transplantation model by flow cytometry and immunofluorescent staining.

RESULTS

By flow cytometry, CD45+ leukocyte infiltrates were more abundant in MCMV-infected allografts at 14 days posttransplant compared with uninfected grafts (P<0.01) and decreased in the presence of GCV (P<0.05). CD11c+ dendritic cells, Gr-1+ myeloid cells, CD204+ macrophages, and CD49b+ natural killer cells were reduced in GCV-treated allografts compared with MCMV-infected grafts without GCV treatment (P<0.05). However, GCV failed to reduce these cell types to levels found in MCMV-uninfected allografts. By day 7 after cessation of GCV prophylaxis, dendritic cells, macrophages, and natural killer cells increased in number and became statistically indistinguishable from numbers of cells found in MCMV-infected allografts without GCV. GCV treatment did not affect the numbers of CD4+, CD8+, or CD19+/B220+ lymphocytes infiltrating the allografts. Infiltrates were confirmed histologically by immunofluorescent staining for CD3+ and CD11b+ cells.

CONCLUSIONS

In this model, MCMV-infected allografts developed significantly greater innate and adaptive leukocytic infiltrates compared with uninfected grafts. GCV attenuated the MCMV-associated innate leukocyte infiltrates in infected allografts but not the lymphocytic infiltrates. The attenuated innate response was limited to the period of GCV prophylaxis.

Herpes simplex virus-induced cardiomyopathy successfully treated with acyclovir

Inflammatory dilated cardiomyopathy (DCMi) represents an acquired form of dilated cardiomyopathy. Viral infection is the most common cause of DCMi. In contrast with other cardiotropic viruses, herpes simplex virus (HSV) is a very rare finding in endomyocardial biopsies of patients with dilated cardiomyopathy. We report a case of HSV-induced cardiomyopathy successfully treated with acyclovir.

Antiviral prevention of sepsis induced cytomegalovirus reactivation in immunocompetent mice

INTRODUCTION

Immunocompetent patients can reactivate latent cytomegalovirus (CMV) during critical illness and reactivation is associated with significantly worse outcomes. Prior to clinical trials in humans to prove causality, we sought to determine an optimal antiviral treatment strategy.

METHODS

Mice latently infected with murine CMV (MCMV) received a septic reactivation trigger and were randomized to receive one of four ganciclovir regimens or saline. Lungs were evaluated for viral transcriptional reactivation and fibrosis after each regimen. Influences of ganciclovir on early sepsis-induced pulmonary inflammation and T-cell activation were studied after sepsis induction.

RESULTS

All ganciclovir regimens reduced measurable MCMV transcriptional reactivation, and 10mg/day for 7 or 21 days was most effective. Lower dose (5mg/kg/day) or delayed therapy was associated with significant breakthrough reactivation. Higher doses of ganciclovir given early were associated with the lowest incidence of pulmonary fibrosis, and delay of therapy for 1 week was associated with significantly worse pulmonary fibrosis. Although bacterial sepsis induced activation of MCMV-specific pulmonary T-cells, this activation was not influenced by ganciclovir.

CONCLUSION

These results suggest that antiviral treatment trials in humans should use 10mg/kg/day ganciclovir administered as early as possible in at-risk patients to minimize reactivation events and associated pulmonary injury.

Antiviral activity of Arbidol against Coxsackie virus B5 in vitro and in vivo

We investigated the antiviral activity of Arbidol, an antiviral chemical compound, against Coxsackie virus B5 (CVB₅) in vitro and in vivo. Arbidol not only prevented the cytopathic effect (CPE) of CVB₅, as demonstrated in an MTT colorimetric assay, when added during or after viral infection, with a 50% inhibitory concentration (IC₅₀) from 2.66 to 6.62 μg/ml, but it also decreased the CVB₅-RNA level in infected host cells, as shown in semi-quantitative RT-PCR. BALB/c mice were used as an animal model to test the Arbidol activity in vivo. Orally administered Arbidol at 50 mg/kg body weight/day (once a day) significantly reduced mean virus yields in the lungs and heart as well as mortality after infection for 6 days. Our results demonstrate that in vitro and in vivo infection with CVB₅ can be effectively treated by Arbidol.

Lymphocytic Myocarditis After Lung Transplantation

This study reports the development of lymphocytic myocarditis in a bilateral lung allograft recipient. A 23-year-old woman developed congestive heart failure and severe left ventricular dysfunction 32 months after a bilateral lung allograft for cystic fibrosis. She had taken oral acyclovir for infectious mononucleosis that was diagnosed 11 months previously. Her viral load for Epstein-Barr virus (EBV) increased, and an echocardiogram revealed a left ventricular ejection fraction of 25% and endomyocardial biopsy revealed lymphocytic myocarditis. She received valacyclovir (1 g x 3 times daily) and made a full recovery 6 months later.

Cytomegalovirus Infection of the Heart Is Common in Patients with Fatal Myocarditis

BACKGROUND

Although enteroviruses and adenoviruses are considered to be the leading causes of the usually mild clinical myocarditis, little is known about the etiology of severe or fatal myocarditis.

METHODS

We collected all available clinical records and myocardial autopsy samples for patients who had myocarditis recorded as the underlying cause of death in Finland during the period of 1970-1998. Findings for all available patients (20 men and 20 women; median age, 49 years) with myocarditis that fulfilled the Dallas criteria and who had sufficient data were included in the study. Twelve subjects who had died accidentally served as control subjects. Polymerase chain reaction (PCR) and in situ hybridization assays were used for detection of viral genomes (adenovirus, cytomegalovirus, enterovirus, human herpesvirus 6, influenza A and B viruses, parvovirus B19, and rhinovirus) in heart samples.

RESULTS

Viral nucleic acids were found in the hearts of 17 patients (43%), including cytomegalovirus (15 patients), parvovirus B19 (4 patients), enterovirus (1 patient), and human herpesvirus 6 (1 patient). In 4 patients, cytomegalovirus DNA was found in addition to parvovirus B19 or enterovirus genomes. No adenoviruses, rhinoviruses, or influenza viruses were detected in this study of fatal myocarditis. In 67% of the patients for whom PCR was positive for cytomegalovirus, in situ hybridization revealed viral DNA in cardiomyocytes. Only 1 of these patients was immunocompromised. In the control group, only human herpesvirus 6 (1 subject) and parvovirus B19 (1 subject) DNA were detected.

CONCLUSIONS

In this population-based study, cytomegalovirus was found to be the most common specific finding in immunocompetent patients with fatal myocarditis. This may have important clinical implications for the treatment of severe acute myocarditis.

Clinical potential of the acyclic nucleoside phosphonates cidofovir, adefovir, and tenofovir in treatment of DNA virus and retrovirus infections

The acyclic nucleoside phosphonates HPMPC (cidofovir), PMEA (adefovir), and PMPA (tenofovir) have proved to be effective in vitro (cell culture systems) and in vivo (animal models and clinical studies) against a wide variety of DNA virus and retrovirus infections: cidofovir against herpesvirus (herpes simplex virus types 1 and 2 varicella-zoster virus, cytomegalovirus [CMV], Epstein-Barr virus, and human herpesviruses 6, 7, and 8), polyomavirus, papillomavirus, adenovirus, and poxvirus (variola virus, cowpox virus, vaccinia virus, molluscum contagiosum virus, and orf virus) infections; adefovir against herpesvirus, hepadnavirus (human hepatitis B virus), and retrovirus (human immunodeficiency virus types 1 [HIV-1] and 2 [HIV-2], simian immunodeficiency virus, and feline immunodeficiency virus) infections; and tenofovir against both hepadnavirus and retrovirus infections. Cidofovir (Vistide) has been officially approved for the treatment of CMV retinitis in AIDS patients, tenofovir disoproxil fumarate (Viread) has been approved for the treatment of HIV infections (i.e., AIDS), and adefovir dipivoxil (Hepsera) has been approved for the treatment of chronic hepatitis B. Nephrotoxicity is the dose-limiting side effect for cidofovir (Vistide) when used intravenously (5 mg/kg); no toxic side effects have been described for adefovir dipivoxil and tenofovir disoproxil fumarate, at the approved doses (Hepsera at 10 mg orally daily and Viread at 300 mg orally daily).

Cytokine expression in murine cytomegalovirus-induced myocarditis: modulation with interferon-alpha therapy

Cytomegalovirus-induced myocarditis is largely immune-mediated. BALB/c mice produced higher levels of IL-4 in the heart indicative of a Th2-like response. Although IL-6, IL-10, IL-18, and TNF-alpha were produced in the heart during acute infection, BALB/c mice lacked a substantial IL-2 and IFN-gamma response. Conversely, C57BL/6 mice produced significant levels of IFN-gamma in the heart with no significant levels of IL-4 or IL-6, suggestive of a dominant Th1-like response to virus infection. IFN-alpha/beta immunotherapy is known to suppress the development of MCMV-myocarditis. Cytokine secretion in IFN-stimulated MCMV-infected BALB/c myocytes was found to be IFN subtype-dependent with elevation of IL-6 and IL-18 levels. During the chronic phase of disease, IFNA6 DNA treatment in vivo increased IL-18 production in the heart. These results suggest that IFN subtype therapy may have immunomodulating effects in reducing disease severity in BALB/c mice via regulation of cytokine production in the heart.