Ameliorating effect of IFN-beta and anti-IFN-beta on coxsackievirus B3-induced myocarditis in mice

Crosstalk Between Innate Immunity and Autophagy in Viral Myocarditis Leading to Dilated Cardiomyopathy

Viral myocarditis, characterised by inflammation of the heart muscle, presents a significant challenge to global public health, particularly affecting younger individuals and often progressing to dilated cardiomyopathy (DCM), a leading cause of heart failure. Despite ongoing research efforts, viable treatments for this condition remain elusive. Recent studies have shed light on the complex interplay between the innate immune response and autophagy mechanisms, revealing their pivotal roles in the pathogenesis of viral myocarditis and subsequent DCM development. This review aims to delve into the recent advancements in understanding the molecular mechanisms and pathways that intersect innate immunity and autophagy in the context of viral myocarditis. Furthermore, it explores the potential therapeutic implications of these findings, offering insights into promising avenues for the management and treatment of this debilitating condition.

Mitochondria Dysfunction at the Heart of Viral Myocarditis: Mechanistic Insights and Therapeutic Implications

The myocardium/heart is the most mitochondria-rich tissue in the human body with mitochondria comprising approximately 30% of total cardiomyocyte volume. As the resident "powerhouse" of cells, mitochondria help to fuel the high energy demands of a continuously beating myocardium. It is no surprise that mitochondrial dysfunction underscores the pathogenesis of many cardiovascular ailments, including those of viral origin such as virus-induced myocarditis. Enteroviruses have been especially linked to injuries of the myocardium and its sequelae dilated cardiomyopathy for which no effective therapies currently exist. Intriguingly, recent mechanistic insights have demonstrated viral infections to directly damage mitochondria, impair the mitochondrial quality control processes of the cell, such as disrupting mitochondrial antiviral innate immune signaling, and promoting mitochondrial-dependent pathological inflammation of the infected myocardium. In this review, we briefly highlight recent insights on the virus-mitochondria crosstalk and discuss the therapeutic implications of targeting mitochondria to preserve heart function and ultimately combat viral myocarditis.

Promising Therapy for Heart Failure in Patients with Severe COVID-19: Calming the Cytokine Storm

The coronavirus disease 19 (COVID-19) pandemic poses a serious global threat to human health and the economy. Based on accumulating evidence, its continuous progression involves not only pulmonary injury but also damage to the cardiovascular system due to intertwined pathophysiological risks. As a point of convergence in the pathophysiologic process between COVID-19 and heart failure (HF), cytokine storm induces the progression of COVID-19 in patients presenting pre-existing or new onset myocardial damage and even HF. Cytokine storm, as a trigger of the progression of HF in patients with COVID-19, has become a novel focus to explore therapies for target populations. In this review, we briefly introduce the basis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and illuminate the mechanism and links among COVID-19, cytokine storm, and HF. Furthermore, we discuss drugs and therapeutic targets for patients with COVID-19 and HF.

Inhibition of Type III Interferon Expression in Intestinal Epithelial Cells-A Strategy Used by Coxsackie B Virus to Evade the Host's Innate Immune Response at the Primary Site of Infection?

Increasing evidence highlights the importance of the antiviral activities of the type III interferons (IFNλs; IL-28A, IL-28B, IL29, and IFNλ4) in the intestine. However, many viruses have developed strategies to counteract these defense mechanisms by preventing the production of IFNs. Here we use infection models, a clinical virus isolate, and several molecular biology techniques to demonstrate that both type I and III IFNs induce an antiviral state and attenuate Coxsackievirus group B (CVB) replication in human intestinal epithelial cells (IECs). While treatment of IECs with a viral mimic (poly (I:C)) induced a robust expression of both type I and III IFNs, no such up-regulation was observed after CVB infection. The blunted IFN response was paralleled by a reduction in the abundance of proteins involved in the induction of interferon gene transcription, including TIR-domain-containing adapter-inducing interferon-β (TRIF), mitochondrial antiviral-signaling protein (MAVS), and the global protein translation initiator eukaryotic translation initiation factor 4G (eIF4G). Taken together, this study highlights a potent anti-Coxsackieviral effect of both type I and III IFNs in cells located at the primary site of infection. Furthermore, we show for the first time that the production of type I and III IFNs in IECs is blocked by CVBs. These findings suggest that CVBs evade the host immune response in order to successfully infect the intestine.

Biphasic and cardiomyocyte-specific IFIT activity protects cardiomyocytes from enteroviral infection

Viral myocarditis is a serious disease, commonly caused by type B coxsackieviruses (CVB). Here we show that innate immune protection against CVB3 myocarditis requires the IFIT (IFN-induced with tetratricopeptide) locus, which acts in a biphasic manner. Using IFIT locus knockout (IFITKO) cardiomyocytes we show that, in the absence of the IFIT locus, viral replication is dramatically increased, indicating that constitutive IFIT expression suppresses CVB replication in this cell type. IFNβ pre-treatment strongly suppresses CVB3 replication in wild type (wt) cardiomyocytes, but not in IFITKO cardiomyocytes, indicating that other interferon-stimulated genes (ISGs) cannot compensate for the loss of IFITs in this cell type. Thus, in isolated wt cardiomyocytes, the anti-CVB3 activity of IFITs is biphasic, being required for protection both before and after T1IFN signaling. These in vitro findings are replicated in vivo. Using novel IFITKO mice we demonstrate accelerated CVB3 replication in pancreas, liver and heart in the hours following infection. This early increase in virus load in IFITKO animals accelerates the induction of other ISGs in several tissues, enhancing virus clearance from some tissues, indicating that–in contrast to cardiomyocytes–other ISGs can offset the loss of IFITs from those cell types. In contrast, CVB3 persists in IFITKO hearts, and myocarditis occurs. Thus, cardiomyocytes have a specific, biphasic, and near-absolute requirement for IFITs to control CVB infection.

Viruses can infect the heart, causing inflammation–termed myocarditis–which is a serious, and sometimes fatal, disease. One way to combat the infection is by stimulating our immune system, encouraging it to fight the virus. However, the treatment that is currently used “revs up” many different parts of our immune system, including some that play little or no role in clearing the virus, and this wide-ranging activation increases the risk of potentially-harmful side effects. We want to identify the parts of the immune system that fight virus infections of the heart, so that we can improve the treatment of viral myocarditis by selectively stimulating only those immune responses, thereby retaining the benefit of treatment (i.e., clearing the virus) while reducing its cost (i.e. lowering the risk of harmful side effects). In this paper, we demonstrate that a family of proteins called IFITs play a role in protecting many tissues against these infections, but are particularly important in heart muscle cells, in which they are indispensable. Thus, IFITs represent a possible target for the treatment of viral myocarditis.

Could interferon-gamma be a therapeutic target for treating heart failure?

The cytokine interferon-gamma (IFN-γ) is the only known member of the type II family of interferons, and as such, binds to its own distinct receptor. It is important in host defense against infection, as well as adaptive immune responses. While a wide array of cytokines are known to be involved in adverse remodeling of the heart and the progression to heart failure, the role of IFN-γ is unclear. Recent evidence from clinical studies, animal models of myocarditis and hypertension, as well as isolated cell studies, provide conflicting data as to whether IFN-γ is pathological or protective in the heart. Thus, it is important to highlight these discrepant findings so that areas of future investigation can be identified to more clearly determine the precise role of IFN-γ in the heart. Accordingly, this review will (1) discuss the source of IFN-γ in the diseased heart; (2) summarize the data from animal studies; (3) discuss the effects of IFN-γ on isolated cardiac fibroblasts and cardiomyocytes; (4) identify signaling mechanisms that may be invoked by IFN-γ in the heart; and (5) present the clinical evidence supporting a role for IFN-γ in heart failure.

c-FLIP-Short reduces type I interferon production and increases viremia with coxsackievirus B3

Cellular FLIP (c-FLIP) is an enzymatically inactive paralogue of caspase-8 and as such can block death receptor-induced apoptosis. However, independent of death receptors, c-FLIP-Long (c-FLIP_L) can heterodimerize with and activate caspase-8. This is critical for promoting the growth and survival of T lymphocytes as well as the regulation of the RIG-I helicase pathway for type I interferon production in response to viral infections. Truncated forms of FLIP also exist in mammalian cells (c-FLIP_S) and certain viruses (v-FLIP), which lack the C-terminal domain that activates caspase-8. Thus, the ratio of c-FLIP_L to these short forms of FLIP may greatly influence the outcome of an immune response. We examined this model in mice transgenically expressing c-FLIP_S in T cells during infection with Coxsackievirus B3 (CVB3). In contrast to our earlier findings of reduced myocarditis and mortality with CVB3 infection of c-FLIP_L-transgenic mice, c-FLIP_S-transgenic mice were highly sensitive to CVB3 infection as manifested by increased cardiac virus titers, myocarditis score, and mortality compared to wild-type C57BL/6 mice. This observation was paralleled by a reduction in serum levels of IL-10 and IFN-α in CVB3-infected c-FLIP_S mice. In vitro infection of c-FLIP_S T cells with CVB3 confirmed these results. Furthermore, molecular studies revealed that following infection of cells with CVB3, c-FLIP_L associates with mitochondrial antiviral signaling protein (MAVS), increases caspase-8 activity and type I IFN production, and reduces viral replication, whereas c-FLIP_S promotes the opposite phenotype.

Interferon beta-1b therapy in chronic viral dilated cardiomyopathy--is there a role for specific therapy?

BACKGROUND

Myocardial biopsy can be used for the detection of viral genome in dilated cardiomyopathy (DCM). Pilot studies have previously reported beneficial effects on clinical outcome and safety of an antiviral therapy using interferon beta-1b in chronic viral DCM.

METHODS AND RESULTS

Myocardial biopsies were taken from patients with DCM. Using polymerase chain reaction and Southern Blot analysis, viral genome could be detected in 49% of patients. In 42 patients with viral infection, off-label use with interferon beta-1b was initiated. A further 68 patients formed the control group. The outcome was evaluated after follow-up with echocardiography, exercise electrocardiogram, and New York Heart Association class. A total of 81 men and 29 women with a median left ventricular ejection fraction of 34% were included. The follow-up period was 36 months. In 33 (79%) patients with interferon beta-1b treatment, minor adverse reactions occurred, but no major adverse events were reported. No significant benefit for interferon beta-1b treatment on clinical outcome could be detected during follow-up.

CONCLUSIONS

Off-label use with interferon beta-1b in patients with viral DCM is feasible and safe under routine clinical practice. Concerning the herein evaluated clinical outcome parameters, promising results from pilot studies could not be confirmed. High prevalence of parvovirus B19 (92%) might influence the results.

Antiviral and myocyte protective effects of murine interferon-β and -α2in coxsackievirus B3-induced myocarditis and epicarditis in Balb/c mice

The present study tested the hypothesis that murine (m)IFN-β or mIFN-α2can eliminate cardiac viral load and protect cardiomyocytes from injury in animals infected with coxsackievirus B3 (CVB3). CVB3-inoculated male Balb/c mice exhibited signs of illness, including lethargy, progressive weight loss, and death (10% on day 3 and 100% on day 8). Cardiac viral load was high [4,277 ± 1,009 plaque-forming units and 25 ± 5 copies CVB3/hypoxanthine guanine phosphoribosyl transferase 1 mRNA] on day 4. The cardiac tissue exhibited severe inflammatory infiltration and myocyte damage with an average myocarditis integrated pathology score of 2.1 ± 0.2 on day 7. Most of the mice infected with CVB3 also developed epicarditis, and 55% had intraventricular thrombi present. Treatment with mIFN-β [2.5 to 10 million international units (MIU)/kg] dose-dependently improved the general health status in CVB3-inoculated mice, as evidenced by reduction in weight loss, prevention of death, elimination of cardiac viral load, protection of myocytes from injury, decrease in inflammatory cell infiltration, and attenuation of intraventricular thrombus formation. Treatment with 10 MIU/kg mIFN-α2resulted in a similar level of efficacy as that induced by 5 MIU/kg mIFN-β, with the exception that mIFN-α2did not reduce cardiac CVB3 mRNA. However, mIFN-α2, but not any dose group of mIFN-β, significantly attenuated CVB3-induced epicarditis. These data demonstrate antiviral effects for both mIFN-β and mIFN-α2, which lead to protection of the mice from CVB3-induced myocarditis. However, the potential mechanisms leading to a differential host response for the two isoforms of mIFN remain to be elucidated.

Coxsackievirus myocarditis: interplay between virus and host in the pathogenesis of heart disease

Coxsackievirus (CVB) infection is a significant cause of myocarditis and dilated cardiomyopathy (DCM). Heart disease may be caused by direct cytopathic effects of the virus, a pathologic immune response to persistent virus, or autoimmunity triggered by the viral infection. CVB interacts with its host at multiple stages during disease development. Signaling through viral receptors may alter the intracellular environment in addition to facilitating virus entry. Viral genetic determinants that encode cardiovirulence have been mapped and may change depending on the nutritional status of the host. Virus persistence is directly associated with pathology, and recent work demonstrates that CVB evolves into a slowly replicating form capable of establishing a low-grade infection in the heart. The innate immune response to CVB has taken on increasing importance because of its role in shaping the development of the adaptive immune response that is responsible for cardiac pathology. Studies of T cell responsiveness and the development of autoimmunity at the molecular level are beginning to clarify the mechanisms through which CVB infection causes inflammatory heart disease.

Myocardial biopsy based classification and treatment in patients with dilated cardiomyopathy

BACKGROUND

We investigated whether myocardial biopsy analysis for inflammation and viruses correlates with outcome in dilated cardiomyopathy.

METHODS

Myocardial biopsies of 82 patients were analyzed for HLAI, HLAII, CD54, CD2, CD68 and entero-/adenovirus. Ejection fraction was determined by left ventriculography. NYHA classification, electrocardiogram (ECG) and echocardiography were analyzed at first admission and for follow up. Patients were attributed to three groups: (A) no inflammation/no virus (B) inflammation/no virus (C) virus with/without inflammation. Patients not responding to conventional treatment of heart failure received interferon beta1b (group C) or prednisolone (group B). Median follow up was 7 months (group A), 11 months (group B) and 14.5 months (group C).

RESULTS

Thirty nine patients (48%) belonged to group A, 33 patients (40%) to group B, 10 patients (12%) to group C. Only enterovirus was detected. Ejection fraction at admission was worse for group B compared to group A (p=0.003). Groups A and B improved for echocardiography and NYHA (p< or =0.001). Group C improved for echocardiography only (p=0.031). Group B showed a better outcome for echocardiography (p=0.014) and NYHA (p=0.023) than group A.

CONCLUSIONS

Inflammatory cardiomyopathy shows the best outcome. Antiinflammatory or antiviral treatment may be an option in patients not responding to conventional therapy.

The interferon inducer ampligen [poly(I)-poly(C12U)] markedly protects mice against coxsackie B3 virus-induced myocarditis

Viral replication, as well as an immunopathological component, is assumed to be involved in coxsackie B virus-induced myocarditis. We evaluated the efficacy of the interferon inducer Ampligen on coxsackie B3 virus-induced myocarditis in C3H/HeNHsd mice. The efficacy of Ampligen was compared with that of the interferon inducer poly(inosinic acid)-poly(cytidylic acid) [poly(IC)], alpha interferon 2b (INTRON A), and pegylated alpha interferon 2b (PEG-INTRON-alpha-2b). Ampligen at 20 mg/kg of body weight/day was able to reduce the severity of virus-induced myocarditis, as assessed by morphometric analysis, by 98% (P = 3.0 x 10(-8)). When poly(IC) was administered at 15 mg/kg/day, it reduced the severity of virus-induced myocarditis by 93% (P = 5.6 x 10(-5)). Alpha interferon 2b (1 x 10(5) U/day) and pegylated alpha interferon 2b (5 x 10(5) U/day) were less effective and reduced the severity of virus-induced myocarditis by 66% (P = 0.0009) and 78% (P = 0.0002), respectively. The observed efficacies of Ampligen and poly(IC) were corroborated by the observation that the drugs also markedly reduced the virus titers in the heart, as detected by (i) quantitative real-time reverse transcription-PCR and (ii) titration for infectious virus content. Whereas the electrocardiograms for untreated mice with myocarditis were severely disturbed, the electrocardiographic parameters were normalized in Ampligen- and poly(IC)-treated mice. Even when start of treatment with Ampligen was delayed until day 2 postinfection, a time at which lesions had already appeared in untreated control animals, a marked protective effect on the development of viral myocarditis (as assessed at day 6 postinfection) was still noted.

Interferons in enteroviral heart disease: modulation of cytokine expression and antiviral activity

Interferon (IFN)-beta has a more than 120-fold higher antiviral activity than the closely related IFN-alpha in human myocardial fibroblasts infected with the cardiotropic enterovirus coxsackievirus B3 (CVB3). CVB3 replication induces interleukin (IL)-6 and IL-8 expression in myocardial fibroblasts, and suppresses the expression of monocyte chemoattractant protein-1 (MCP-1). We investigated whether the higher antiviral activity of IFN-beta compared to IFN-alpha was a result of a suppression of IL-8 expression by IFN-beta since previous studies had indicated that IL-8 stimulates enterovirus replication. Human myocardial fibroblasts were treated with either IFN-alpha, IFN-beta or IFN-gamma (0, 10, 100, or 1,000 IU/ml) and the concentrations of IL-6, IL-8 and MCP-1 were measured in culture supernatants by immunoassays. Both IFN-beta and IFN-gamma reduced IL-6 and IL-8 expression significantly. In addition, neutralization of IL-8 in culture supernatants of myocardial fibroblasts using a monoclonal antibody demonstrated a significant reduction of CVB3 titers. Antiproliferative effects of all three IFNs were very low (<30% with 1,000 IU/ml), indicating that the suppression IL-6 and IL-8 was not related to cytotoxicity. MCP-1 expression was increased only by high concentrations of IFN-gamma (1,000 IU/ml). By contrast, IFN-alpha had no significant effect on IL-6, IL-8 and MCP-1 expression. In conclusion, suppression of IL-8 expression is an "immuno-modulating" feature of IFN-beta in human myocardial fibroblasts, which is similar to the activity of IFN-gamma. This feature of IFN-beta contributes to its high antiviral activity against CVB3 and may be useful in the treatment of enteroviral heart disease.

Diabetogenic potential of human pathogens uncovered in experimentally permissive beta-cells

Pancreatic beta-cell antiviral defense plays a critical role in protection from coxsackievirus B4 (CVB4)-induced diabetes. In the present study, we tested the hypothesis that interferon (IFN)-induced antiviral defense determines beta-cell survival after infection by the human pathogen CVB3, cytomegalovirus (CMV), and lymphocytic choriomeningitis virus (LCMV). We demonstrated that mice harboring beta-cells that do not respond to IFN because of the expression of the suppressor of cytokine signaling-1 (SOCS-1) succumb to an acute form of type 1 diabetes after infection with CVB3. Interestingly, the tropism of the virus was altered in SOCS-1 transgenic (Tg) mice, and CVB3 was detected in islet cells of SOCS-1-Tg mice before beta-cell loss and the onset of diabetes. Furthermore, insulitis was increased in SOCS-1-Tg mice after infection with murine CMV, and a minority of the mice developed overt diabetes. However, infection with LCMV failed to cause beta-cell destruction in SOCS-1 Tg mice. These findings suggest that CVB3 can cause diabetes in a host lacking adequate beta-cell antiviral defense, and that incomplete target cell antiviral defense may enhance susceptibility to diabetes triggered by CMV. In conclusion, suppressed beta-cell antiviral defense reveals the diabetogenic potential of two pathogens previously linked to the onset of type 1 diabetes in humans.

The suppressor of cytokine signaling-1 (SOCS1) is a novel therapeutic target for enterovirus-induced cardiac injury

Enteroviral infections of the heart are among the most commonly identified causes of acute myocarditis in children and adults and have been implicated in dilated cardiomyopathy. Although there is considerable information regarding the cellular immune response in myocarditis, little is known about innate signaling mechanisms within the infected cardiac myocyte that contribute to the host defense against viral infection. Here we show the essential role of Janus kinase (JAK) signaling in cardiac myocyte antiviral defense and a negative role of an intrinsic JAK inhibitor, the suppressor of cytokine signaling (SOCS), in the early disease process. Cardiac myocyte-specific transgenic expression of SOCS1 inhibited enterovirus-induced signaling of JAK and the signal transducers and activators of transcription (STAT), with accompanying increases in viral replication, cardiomyopathy, and mortality in coxsackievirus-infected mice. Furthermore, the inhibition of SOCS in the cardiac myocyte through adeno-associated virus-mediated (AAV-mediated) expression of a dominant-negative SOCS1 increased the myocyte resistance to the acute cardiac injury caused by enteroviral infection. These results indicate that strategies directed at inhibition of SOCS in the heart and perhaps other organs can augment the host-cell antiviral system, thus preventing viral-mediated end-organ damage during the early stages of infection.

Cardioselective infection with coxsackievirus B3 requires intact type I interferon signaling: implications for mortality and early viral replication

BACKGROUND

Interferons (IFNs) play an important role in antiviral defense and have therapeutic potential in coxsackievirus heart disease. However, little is known about the relative contributions of type I and type II IFN signaling in coxsackievirus B3 (CVB3) infection or their role in the cardioselective nature of CVB3 infection.

METHODS AND RESULTS

Wild-type mice and mice deficient for either the type I or the type II IFN receptor (IFNR) were infected with CVB3. Infection of the type I IFNR-deficient mice with >10(3) plaque-forming units (pfu) of CVB3 resulted in 100% mortality within 2 to 4 days after infection. Death was rare in wild-type and type II IFNR-deficient mice after inoculation with as much as 10(8) pfu of CVB3. Surprisingly, the early mortality in the type I IFNR-deficient mice was not accompanied by higher virus titers in the heart. Unexpectedly, a dramatic increase of viral RNA in the liver was found to correlate with early mortality in type I IFNR-deficient mice.

CONCLUSIONS

Type I but not type II IFN signaling is essential for the prevention of early death due to CVB3 infection. Interestingly, neither type I or type II IFN signaling has a dramatic effect on early viral replication in the heart. However, lethal viral replication in the liver is controlled by type I IFNs. These results demonstrate that the IFN system is capable of modulating both viral pathogenicity and tissue tropism.

From myocarditis to cardiomyopathy: mechanisms of inflammation and cell death: learning from the past for the future

A progression from viral myocarditis to dilated cardiomyopathy has long been hypothesized, but the actual extent of this progression has been uncertain. However, a causal link between viral myocarditis and dilated cardiomyopathy has become more evident than before with the tremendous developments in the molecular analyses of autopsy and endomyocardial biopsy specimens, new techniques of viral gene amplification, and modern immunology. The persistence of viral RNA in the myocardium beyond 90 days after inoculation, confirmed by the method of polymerase chain reaction, has given us new insights into the pathogenesis of dilated cardiomyopathy. Moreover, new knowledge of T-cell-mediated immune responses in murine viral myocarditis has contributed a great deal to the understanding of the mechanisms of ongoing disease processes. Apoptotic cell death may provide the third concept to explain the pathogenesis of dilated cardiomyopathy, in addition to persistent viral RNA in the heart tissue and an immune system-mediated mechanism. Beneficial effects of alpha1-adrenergic blocking agents, carteolol, verapamil, and ACE inhibitors have been shown clinically and experimentally in the treatment of viral myocarditis and dilated cardiomyopathy. Antiviral agents should be more extensively investigated for clinical use. The rather discouraging results obtained to date with immunosuppressive agents in the treatment of viral myocarditis indicated the importance of sparing neutralizing antibody production, which may be controlled by B cells, and raised the possibility of promising developments in immunomodulating therapy.

Recombinant Interferons beta and gamma have a higher antiviral activity than interferon-alpha in coxsackievirus B3-infected carrier state cultures of human myocardial fibroblasts

We compared the antiviral activities of three recombinant human interferons (IFN-alph2a, IFN-beta, and IFN-gamma) in cultured human myocardial fibroblasts to select a candidate for trial in heart disease induced by cardiotropic enterovirus, e.g., coxsackievirus B3 (CVB3). Cells were exposed to CVB3, and after 7 days, when a persistent infection had developed, IFN was added. Virus yields were measured on alternate days for the next 7 or 16 days, and IFN activity was assessed as the percentage reduction in yield. IFN-gamma and IFN-beta were both highly active and reduced virus yields by 2 log (EC(99)) at concentrations of 23.4 IU/ml (SD = 8.6) and 10.1 IU/ml (SD = 3.2), respectively; with 250 IU/ml of either IFN, no infectious virus was formed. Unexpectedly, IFN-alpha2a (EC(99)> 1250 IU/ml) was at least 120 times less active than IFN-beta; after use for 8 days or more, the minor effects it produced were no longer related to the concentration applied. Despite the pharmacokinetic advantages of IFN-alpha2a, our data suggest that IFN-beta should in preference be evaluated in the clinic.

Theiler's virus infection of 129Sv mice that lack the interferon alpha/beta or interferon gamma receptors

The Daniels strain of Theiler's virus causes a persistent infection of the white matter of spinal cord of susceptible mice, with chronic inflammation and primary demyelination. Inbred 129Sv mice are resistant to this infection; they present with mild encephalomyelitis and clear the infection within a matter of days. A very different outcome was observed with inbred 129Sv mice whose receptors for interferon alpha/beta or interferon gamma had been inactivated by homologous recombination. The former presented severe encephalomyelitis with acute infection of neurons, particularly in brain and hippocampus, and extensive infection with necrosis of the choroid plexus. Most animals died of this acute disease. The latter, presented the same early encephalomyelitis as the control 129Sv mice. However, they remained persistently infected and developed a very severe late infection of the white matter with extensive primary demyelination. This late disease looked like an exacerbated form of the chronic demyelinating disease observed in susceptible inbred mice such as the SJL/J or FVB strains. Our results show that the two interferon systems play nonredundant roles in the resistance of the 129Sv mouse to the infection by Theiler's virus. They also lend support to the notion that the Ifg gene is involved in the resistance/susceptibility of inbred strains of mice to persistent infection by this picornavirus.

Myocardial enterovirus infection with left ventricular dysfunction: a benign disease compared with idiopathic dilated cardiomyopathy

OBJECTIVES

Endomyocardial biopsy samples from patients with idiopathic dilated cardiomyopathy were screened for the presence of enterovirus genome. Patients with enterovirus-positive samples were further studied with regard to disease course, histologic variables and response to interferon-alpha treatment.

BACKGROUND

Studies of patients with idiopathic dilated cardiomyopathy have reported widely divergent clinical outcomes, suggesting that there is no unique underlying pathogenetic mechanism.

METHODS

Five left ventricular endomyocardial biopsy samples were screened for the presence of the enterovirus genome by an established in situ hybridization technique in combination with a histologic, histomorphometric and immunohistologic workup. The course of the disease was then prospectively followed for up to 50 months. Virus-positive patients whose condition deteriorated were treated with interferon-alpha.

RESULTS

Of 77 patients, 20 (26%) had enterovirus-positive and 57 (74%) enterovirus-negative biopsy samples. During a mean follow-up period of 25.8 +/- 13.7 months, 1 patient in the enterovirus-positive group and 11 in the enterovirus-negative group died. Four patients in the enterovirus-negative group underwent heart transplantation (p < 0.05). The surviving 19 enterovirus-positive patients had a decrease in mean left ventricular end-diastolic diameter from 66 to 61 mm (p < 0.05) and a mean increase in left ventricular ejection fraction from 0.35 to 0.43 (p < 0.05). In contrast, enterovirus-negative patients had no significant change in end-diastolic diameter or left ventricular ejection fraction. Four patients in the enterovirus-positive group whose condition deteriorated were treated with a 6-month course of subcutaneous interferon-alpha (3 x 10(6) U every second day). This treatment induced hemodynamic improvement in all four patients and eliminated the persistent enteroviral infection in two.

CONCLUSIONS

Enterovirus-positive patients have a better heart transplantation-free survival rate and hemodynamic course, with fewer histologic changes, than do enterovirus-negative patients. In addition, enterovirus-positive patients respond favorably to interferon-alpha treatment. These observations indicate that myocardial enteroviral infection with associated left ventricular dysfunction is a distinct disease entity with a benign course.

Role of interferon in lethality and lymphoid atrophy induced by Coxsackievirus B3 infection in mice

To assess the importance of interferon (IFN) in the pathology of coxsackievirus B3 (CVB-3) infection, we evaluated both mortality rate and lymphoid involution in young adult BALB/C mice infected with lethal doses of the virus and treated either with anti-IFN antibody or with murine IFN-alpha/beta. Administration of antibody to IFN caused a profound worsening of the pathology and an increase in the mortality rate in infected animals. Treatment with murine IFN exerted a significant ameliorative effect on lethality when administered concomitantly with or soon after virus infection. The extent of this protection was correlated with the plasma levels of exogenous or endogenous IFN at 6 h postinfection, whereas no correlation with IFN titers was found later. The effects of IFN apparently were not directly mediated by antiviral effects, because at the times studied, no relation was found between IFN levels and virus titers, at least in the plasma of the infected animals. Lymphoid atrophy, assessed by measuring spleen weight, was only partially reversed by early IFN treatment. These data suggest that IFN production is critical during the early phases of infection, whereas it does not seem to play a significant protective role at later stages.

Induction of heterotypic virus resistance in adult inbred mice immunized with a variant of Coxsackievirus B3

Infection of adult male C3H/HeJ mice with a host range variant of Coxsackievirus B3 (CB3W-RD) induced resistance in these mice to an otherwise lethal dose of Coxsackievirus B1 (CB1). The protective effect induced by CB3W-RD was detectable as early as 1 day post-vaccination and was still present 10 weeks later. While untreated mice infected with CB1 died within 5 days because of massive hepatic necrosis, the liver was spared in mice immunized with CB3W-RD and then challenged with CB1. In general, CB1 titers in heart, liver, and pancreas of CB3W-RD-vaccinated animals were lower than that found in unvaccinated animals. Virus neutralizing antibody was not a mediator of this heterotypic, virus-induced protective effect. In addition, the outcome of CB1 infection could be modified if superinfection with CB3W-RD took place within 1-4 days following CB1 infection. In this regard, maximum therapeutic efficacy was observed when CB1 infected mice were superinfected 2 days after CB1 infection. CB1-infected mice that survived as a result of treatment with CB3W-RD exhibited liver regeneration but did develop myocardial necrosis.

Protective effect of recombinant alpha interferon on coxsackievirus B3 myocarditis in mice

The effects of recombinant human leukocyte interferon alpha-A/D on experimental myocarditis caused by coxsackievirus B3 were investigated. Four-week-old male C3H/He mice were inoculated intraperitoneally with 10(5.5) 50% tissue culture infective dose (TCD50) in 0.1 ml of coxsackievirus B3 (Nancy strain). Interferon alpha-A/D, 10(4) U/gm/day, was administered subcutaneously daily, starting 1 day before (group 1) or on the day of (group 2) infection. Animals were killed on day 7. The infectivity of myocardial virus was significantly lower in group 1 (0.7 +/- 0.1 log10TCD50/mg, p less than 0.005) and in group 2 (2.5 +/- 1.2 log10TCD50/mg, p less than 0.005) than in control mice (4.4 +/- 0.9 log10TCD50/mg). Results of histologic examination showed extensive myocardial necrosis and cellular infiltration in all mice in the untreated group, but significantly less severe necrosis and infiltration in the treated groups. Thus, interferon alpha-A/D, when given before and simultaneously with virus, effectively inhibited replication of myocardial virus and reduced the inflammatory response and myocardial damage in an experimental model of viral myocarditis.

Factors affecting the infection of the D variant of encephalomyocarditis virus in the B cells of C57BL/6J mice

The D variant of encephalomyocarditis virus is capable of infecting most inbred strains of mice. However, only certain strains are susceptible to the diabetogenic effect of this virus. In order to understand why some inbred strains do not become diabetic, the pathogenesis of infection was studied in diabetes-resistant C57BL/6J mice. It was the purpose of the investigation to ascertain whether specific host defense factors might play a crucial role in the mechanism of resistance. To determine whether perturbations of the immune response would alter the resistance of these animals, mice were treated with a high dose (1.15 mmol/kg body weight) of the T- and B-cell toxin cyclophosphamide prior to infection with the D variant. This treatment did not induce overt diabetes or glucose intolerance in the mice tested 7 days after infection. Based on this finding, it appeared likely that resistance to the D variant is conveyed by some factor other than cell-mediated immunity. A likely candidate to control this viral infection is the interferon system. To investigate this possibility, C57BL/6J mice were infected with the D variant and the concentrations of serum interferon titred at various intervals thereafter. In contrast to previous reports with diabetes susceptible mice, C57BL/6J mice were found to generate a substantial interferon response against this variant, with peak levels found in the serum at 24 h following infection. Additional studies were performed in which mice were treated with antibody to mouse interferon alpha/beta at the time of infection and again 3 days after infection with the D variant.(ABSTRACT TRUNCATED AT 250 WORDS)

Coxsackievirus B3 infection alters plasma membrane of neonatal skin fibroblasts

Replication of coxsackievirus B3 occurred for days in cultures of murine neonatal skin fibroblasts in the absence of cytopathology and resulted in alteration of the plasma membrane. Dual immunofluorescence studies showed that the lectin Ulex europaeus agglutinin I bound only to cells producing viral capsid antigens. Cultures of coxsackievirus B3-inoculated murine neonatal skin fibroblasts showed maximum binding of this lectin at 72 h postinoculation. These data show that in a nonlytic infection a picornavirus can alter the surface of an infected cell.

Cellular immune responses in mice challenged with an amyocarditic variant of Coxsackievirus B3

An amyocarditic variant of a temperature-sensitive (ts) mutant derived from the parent myocarditic variant Coxsackievirus B3 (CVB3m) was studied in a murine model of CVB3m-induced myocarditis to assess virus-induced antigens and their possible role in the disease process. Amyocarditic variant ts5R induced a heart tissue antigen(s), extractable by hypertonic KC1, which inhibited migration of peritoneal exudate cells from CVB3-inoculated myocarditic mice in an agarose droplet cell-migration-inhibition assay. The ts5R variant was amyocarditic at inoculum doses of 10(3) to 10(8) plaque-forming units per mouse, but in cyclophosphamide-immunosuppressed mice, ts5R induced myocarditis. Viable ts5R served as a vaccine and protected mice against CVB3m-induced myocarditis. Murine neonatal skin fibroblasts (MNSF) infected with either virus served as in vitro targets and were lysed by splenic cytotoxic T lymphocytes from mice inoculated with either virus variant. ts5R and CVB3m replicated to similar titers in murine neonatal skin fibroblasts (MNSF) at 24 hr postinoculation (pi), but differences in titers were found by 72 hr pi. Levels of natural killer cell activities in spleens of ts5R-inoculated mice were slightly lower than in spleens of CVB3m-inoculated mice at 7 days pi. The data suggest that viral induction of new antigens on target cells and viral induction of specific cytotoxic T lymphocytes that recognize these antigenic changes do not always result in induction of myocarditis.