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

Impairment of human neural crest cell migration by prolonged exposure to interferon-beta

Human cell-based toxicological assays have been used successfully to detect known toxicants, and to distinguish them from negative controls. However, there is at present little experience on how to deal with hits from screens of compounds with yet unknown hazard. As a case study to this issue, we characterized human interferon-beta (IFNβ) as potential developmental toxicant affecting neural crest cells (NCC). The protein was identified as a hit during a screen of clinically used drugs in the ‘migration inhibition of neural crest’ (MINC) assay. Concentration–response studies in the MINC combined with immunocytochemistry and mRNA quantification of cellular markers showed that IFNβ inhibited NCC migration at concentrations as low as 20 pM. The effective concentrations found here correspond to levels found in human plasma, and they were neither cytostatic nor cytotoxic nor did they did they affect the differentiation state and overall phenotype of NCC. Data from two other migration assays confirmed that picomolar concentration of IFNβ reduced the motility of NCC, while other interferons were less potent. The activation of JAK kinase by IFNβ, as suggested by bioinformatics analysis of the transcriptome changes, was confirmed by biochemical methods. The degree and duration of pathway activation correlated with the extent of migration inhibition, and pharmacological block of this signaling pathway before, or up to 6 h after exposure to the cytokine prevented the effects of IFNβ on migration. Thus, the reduction of vital functions of human NCC is a hitherto unknown potential hazard of endogenous or pharmacologically applied interferons.

Sex-Dependent Intestinal Replication of an Enteric Virus

Coxsackievirus is an enteric virus that initiates infection in the gastrointestinal tract before disseminating to peripheral tissues to cause disease, but intestinal factors that influence viral replication are understudied. Furthermore, a sex bias for severe sequelae from coxsackievirus infections has been observed in humans. While mouse models mimicking human pathogenesis have been well characterized, many of these experiments use intraperitoneal injection of coxsackievirus to infect mice, bypassing the intestine. In light of recent studies identifying intestinal factors, such as the microbiota, that alter enteric viral replication, we sought to investigate coxsackievirus replication within the intestine. Here, we orally infected mice with coxsackievirus B3 (CVB3) and found that CVB3 replication in the intestine is sex dependent. CVB3 replicated efficiently in the intestine of male mice but not female mice. Additionally, we found that the type I interferon response and sex hormones can alter both viral replication and lethality. Overall, these data suggest that sex and the immune response play a vital role in CVB3 replication in the intestine and should be considered in light of the sex bias observed in human disease.IMPORTANCE Sex bias in severe sequelae from enteric viral infections has been observed. Since viruses have evolved to achieve optimal levels of fitness in their environmental niches, it is imperative to study viruses at the site of initial replication. Here, we used an oral inoculation system for CVB3, which follows the natural route of infection in the gastrointestinal tract. We found that sex can influence the replication of CVB3 in the intestine. Additionally, the type I interferon response and sex hormones alter both CVB3 intestinal replication and lethality. Overall this work highlights the fact that sex should be considered in investigations of enteric viral replication and pathogenesis.

High Frequency of Detection by PCR of Viral Nucleic Acid in The Blood of Infants Presenting with Clinical Myocarditis

Specific viruses are associated with pediatric myocarditis, but the prevalence of viral DNAemia detected by blood polymerase chain reaction (PCR) is unknown. We evaluated the prevalence of known cardiotropic viruses (enterovirus, adenovirus, human herpesvirus 6, and parvovirus B19) in children with clinical myocarditis (n = 21). Results were compared to pediatric controls with similar viral PCR testing. The majority of positive PCR (89 %) was noted in children ≤12 months of age at diagnosis compared to older children. Infant myocarditis patients (8/10) had increased the prevalence of PCR positivity compared to infant pediatric controls (4/114) (p < 0.0001). Other than age, patient characteristics at diagnosis were similar between PCR-positive and PCR-negative patients. Both PCR-negative myocarditis infants had clinical recovery at follow-up. Of the PCR-positive myocarditis infants, 4 had clinical recovery, 2 developed chronic cardiomyopathy, 1 underwent heart transplant, and 1 died. Infants with clinical myocarditis have a high rate of blood viral positivity, which is higher compared to older children with myocarditis and healthy infant controls. Age-related differences in PCR positivity may be due to differences in host and/or virus characteristics. Our findings suggest that viral blood PCR may be a useful diagnostic tool and identify patients who would potentially benefit from virus-specific therapy.

Unc93b1 -Dependent Endosomal Toll-Like Receptor Signaling Regulates Inflammation and Mortality during Coxsackievirus B3 Infection

Coxsackievirus strain B serotype 3 (CVB3)-induced myocarditis is an important human disease that causes permanent tissue damage and can lead to death from acute infection or long-term morbidity caused by chronic inflammation. The timing and magnitude of immune activation following CVB3 infection can mediate a positive host outcome or increase tissue pathology. To better elucidate the role of endosomal Toll-like receptor (TLR) signaling in acute CVB3 infection, we studied mice with a loss-of-function mutation, known as Letr for 'loss of endosomal TLR response', in Unc93b1, which is a chaperone protein for TLR3, TLR7 and TLR9. Using Unc93b1(Letr/)(Letr) mice, we determined that Unc93b1-dependent TLR activation was essential for the survival of acute CVB3-induced myocarditis. We also determined that a lack of endosomal TLR signaling was associated with a higher viral load in target organs and that it increased inflammation, necrosis and fibrosis in cardiac tissue. Loss of Unc93b1 function was also associated with increased cardiac expression of Ifn-b and markers of tissue injury and fibrosis including Lcn2 and Serpina3n early after CVB3 infection. These observations establish a significant role for Unc93b1 in the regulation of the host inflammatory response to CVB3 infection and also reveal potential mediators of host tissue damage that merit further investigation in acute viral myocarditis.

Human enterovirus in the gastrocnemius of patients with peripheral arterial disease

Background

Peripheral arterial disease (PAD) is characterized by myofiber degeneration and loss of function in muscles of the lower limbs. Human enterovirus (HEV) infection has been implicated in the pathogenesis of a number of muscle diseases. However, its association with PAD has not been studied. In this study, we tested the hypothesis that infectious HEV is present in skeletal muscle of patients with PAD and is associated with severity of disease.

Methods and Results

Gastrocnemius biopsies from 37 patients with PAD and 14 controls were examined for the presence of HEV RNA, viral capsid protein, viral RNA copy number, and viral infectivity. HEV RNA was detected in 54% of the biopsies from patients with PAD but was not detected in muscle biopsies from control patients. This difference in prevalence among PAD and control patients was significant at P<0.001. Viral RNA copy numbers were increased significantly at the later stages of disease; Fontaine Stage IV (10^5.50 copies/mg muscle wet weight, at P<0.005) and Stage III (10^4.87 copies/mg, at P<0.010) compared to Stage II (10^2.50 copies/mg). Viral replication was confirmed by the presence of the negative‐strand of viral RNA in all specimens positive for HEV RNA. Cultures of HeLa and human skeletal muscle cells treated with muscle homogenates showed HEV replication and the presence of HEV capsid protein.

Conclusion

Our data identified infectious HEV in the gastrocnemius of PAD patients but not in controls. Viral copy number and prevalence of infection were higher in the later stages of disease. Our data point to the need for further studies to determine the contribution of HEV infection to the pathophysiology of PAD.

Pharmacological and biological antiviral therapeutics for cardiac coxsackievirus infections

Subtype B coxsackieviruses (CVB) represent the most commonly identified infectious agents associated with acute and chronic myocarditis, with CVB3 being the most common variant. Damage to the heart is induced both directly by virally mediated cell destruction and indirectly due to the immune and autoimmune processes reacting to virus infection. This review addresses antiviral therapeutics for cardiac coxsackievirus infections discovered over the last 25 years. One group represents pharmacologically active low molecular weight substances that inhibit virus uptake by binding to the virus capsid (e.g., pleconaril) or inactivate viral proteins (e.g., NO-metoprolol and ribavirin) or inhibit cellular proteins which are essential for viral replication (e.g., ubiquitination inhibitors). A second important group of substances are interferons. They have antiviral but also immunomodulating activities. The third and most recently discovered group includes biological and cellular therapeutics. Soluble receptor analogues (e.g., sCAR-Fc) bind to the virus capsid and block virus uptake. Small interfering RNAs, short hairpin RNAs and antisense oligonucleotides bind to and led to degradation of the viral RNA genome or cellular RNAs, thereby preventing their translation and viral replication. Most recently mesenchymal stem cell transplantation has been shown to possess antiviral activity in CVB3 infections. Taken together, a number of antiviral therapeutics has been developed for the treatment of myocardial CVB infection in recent years. In addition to low molecular weight inhibitors, biological therapeutics have become promising anti-viral agents.

Maturation-dependent responses of human neuronal cells to western equine encephalitis virus infection and type I interferons

Innate cell-autonomous antiviral responses are essential first lines of defense against central nervous system infections but may also contribute to neuropathogenesis. We investigated the relationships between innate immunity and neuronal differentiation using an in vitro culture system with human cell lines to analyze cellular responses to the neurotropic alphavirus western equine encephalitis virus. Human neuronal cells displayed a maturation-dependent reduction in virus-induced cytopathology that was independent of autocrine interferon alpha or beta activity. In addition, maturation was associated with enhanced responsiveness to exogenous stimuli, such that differentiated neurons required five- to ten-fold less type I interferon to suppress viral replication or virus-induced cytopathology compared to immature cells, although this enhanced responsiveness extended to only a subset of unique type I interferons. These results demonstrate that maturation-dependent changes in human neuronal cells may be key determinants in the innate immune response to infections with neurotropic alphaviruses.

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.

The role of enterovirus in chronic fatigue syndrome

Two and a half decades after coining of the term chronic fatigue syndrome (CFS), the diagnosis of this illness is still symptom based and the aetiology remains elusive. Enteroviruses are well known causes of acute respiratory and gastrointestinal infections, with tropism for the central nervous system, muscles, and heart. Initial reports of chronic enteroviral infections causing debilitating symptoms in patients with CFS were met with skeptism, and had been largely forgotten for the past decade. Observations from in vitro experiments and from animal models clearly established a state of chronic persistence through the formation of double stranded RNA, similar to findings reported in muscle biopsies of patients with CFS. Recent evidence not only confirmed the earlier studies, but also clarified the pathogenic role of viral RNA through antiviral treatment. This review summarises the available experimental and clinical evidence that supports the role of enterovirus in chronic fatigue syndrome.

Interferons and viruses: signaling for supremacy

Interferon (IFN)-alpha and IFN-beta are critical mediators of host defense against microbial challenges, directly interfering with viral infection and influencing both the innate and adaptive immune responses. IFNs exert their effects in target cells through the activation of a cell-surface receptor, leading to a cascade of signaling events that determine transcriptional and translation regulation. Understanding the circuitry associated with IFN-mediated signal transduction that leads to a specific biological outcome has been a major focus of our laboratory. Through the efforts of graduate students, postdoctoral fellows, a skilled research technologist, and important collaborations with investigators elsewhere, we have provided some insights into the complexity of the IFN system-and the elegance and simplicity of how protein-protein interactions define biological function.

Protective Role for Interferon-β in Coxsackievirus B3 Infection

Background— Coxsackievirus-induced myocarditis can be a serious cause of heart failure. In the absence of a specific antiviral therapy, modulating the host immune response may be protective. Interferons (IFNs)-α and -β perform a fundamental role in innate and adaptive antiviral responses, thereby presenting as candidate therapeutics for coxsackievirus infections.

Methods and Results— To examine the contribution of IFN-β in protection from coxsackievirus B3 (CVB3) infection, mice lacking the IFN-β gene were infected with 10 3 plaque-forming units of CVB3. In contrast to wild-type mice that exhibit an intact IFN-β response, we observed increased susceptibility to infection (70% mortality), a downregulation of IFN-stimulated gene targets (2′-5′ oligoadenylate synthetase, serine/threonine protein kinase, the GTPase Mx), and cardiomyocyte breakdown and disruption in the IFN-β −/− mice.

Conclusions— Viewed together, these results clearly demonstrate that IFN-β is important in mediating protection against CVB3-induced myocarditis.

Quantitative multiplex real-time PCR for the sensitive detection of interferon beta gene induction and viral suppression of interferon beta expression

Interferon-beta (IFN-beta) protein and activity can be detected by enzyme immunoassays and biological assays. However, precise quantification of low IFN-beta mRNA concentrations, which is advantageous for investigating IFN-beta gene expression in small tissue samples or during the early stage of a virus infection, remains a challenge. Therefore, we established a quantitative real-time PCR (qPCR) for IFN-beta and the housekeeping gene porphobilinogen deanimase (PBGD) in separated assays as well as in a multiplex procedure. Sensitivity for both the templates was less than 20 copies with an intra- and interassay variability of less than 5%. IFN-beta qPCR was utilized to optimize IFN-beta induction with dsRNA polyinosic-polycytidylic acid (poly I:C), delivered by a liposomal transfection agent for reproducible but low, non-cell-toxic IFN-beta concentrations. For studying coxsackievirus B3 (CVB3) interference with IFN-beta expression, CVB3 infected fibroblasts were induced with poly I:C. A significant reduction of IFN-beta mRNA but not PBGD mRNA was demonstrated 5 h after CVB3 infection, indicating a specific inhibition of IFN-beta expression by CVB3 on the mRNA level, in addition to previously reported effects on the translation/post-translation level. In conclusion, sensitive IFN-beta/PBGD multiplex qPCR proved to be a useful tool to study viral interaction with IFN-beta expression.

Direct interferon-gamma-mediated protection caused by a recombinant coxsackievirus B3

Coxsackievirus B3 (CVB3) is one of the most important causes of viral myocarditis. Cytokines are involved in the control of CVB3 replication and pathogenesis. Local expression of specific cytokines by recombinant CVB3 confers prevention of virus-caused myocarditis. Expression of IFN-gamma by CVB3(IFN-gamma) protected BALB/c and C57BL/6 mice when the lethal infection with the highly pathogenic CVB3H3 variant was given directly after or prior to CVB3(IFN-gamma) inoculation by decreasing the viral load and spread as well as tissue destruction. This direct effect was not restricted to the homologous virus. In vitro, cocultivation of CVB3(IFN-gamma)-infected cells induced a reduction of CVB3H3 replication and virus-induced cytopathogenicity.

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.

Synergistic antiviral activity of human interferon combinations in the hepatitis C virus replicon system

The use of type I interferon (IFN), in combination with ribvirin, to treat chronic hepatitis C virus (HCV) infection has many drawbacks that prevent widespread application, ultimately leading to a significant unmet clinical need. Potential improvements in IFN therapy through targeted delivery, molecular alteration, and combination with other agents are ongoing in an attempt to decrease adverse effects and increase efficacy. In this report, the HCV replicon cell culture system was used to assess potential synergistic antiviral effects of multiple IFN species when administered in combination. Quantitative analysis of HCV replicon RNA by TaqMan (PE Applied Biosystems, Foster City, CA) and qualitative analysis of HCV protein expression were used to measure the antiviral efficacy of individual and combination IFN treatments, and synergistic responses of IFN combinations were determined through statistical analysis of the TaqMan results. We found that when administered simultaneously, type I/II IFN combinations (IFN-alpha2b + IFN-gamma or IFN-beta + IFN-gamma) resulted in dramatic antiviral synergy, whereas a type I/I combination (IFN-alpha2b + IFN-beta) demonstrated a slightly antagonistic profile. The synergistic effect is likely due to differential cell surface receptors and signaling pathways employed by types I and II IFNs. Conversely, all type I IFN species bind the same receptor and signal through similar pathways, possibly accounting for the nearly additive response observed. In support of this hypothesis, IFN treatment resulted in differential induction of Stat1 phosphorylation at Tyr 701. In conclusion, simultaneous type I/II IFN combination treatment may allow an overall decreased effective IFN dose, which may reduce the side effect profiles that hinder current therapy.

Recombinant equine interferons: expression cloning and biological activity

Interferons (IFNs) are important mediators of the immune system. Their antiviral activity is an integral part of the innate immune defence, but all IFNs have immune regulatory functions also. Besides rec.eq.IFN-beta detailed descriptions on other rec.IFNs were lacking and none of the proteins was available. To compare the equine IFNs and allow detailed studies on proteins and bioactivity, we performed the expression cloning of rec.eq.IFN-alpha, -beta and -gamma. To achieve maximal expression, a bacterial expression system was chosen. Additionally, rec.eq.IFN-beta and -gamma were expressed in mouse B-cells. The antiviral activity was characterised using different cell lines and equine viruses. The results demonstrate a broad antiviral activity of rec.eq.IFN-alpha being active against all viruses tested, including the equine herpesviruses EHV-1 and -4, while rec.eq.IFN-beta was only active using primary horse cells. Protection depended on viruses, cell lines, infectious doses, amount and time of IFN action prior to infection. While rec.eq.IFN-gamma did not act antivirally, it was effective as an immune modulator of monocytes in vitro. The implications of our findings on clinical immunology and virology, including therapeutic applications of equine IFNs will be discussed.

Characterization of human myocardial fibroblasts immortalized by HPV16 E6--E7 genes

Human myocardial fibroblasts (HMF) have proved to be useful as a species specific cell culture system in various studies on myocarditis and cardiac remodelling. However, their use is limited, since they are hard to obtain and lifespan is short due to replicative senescence. To overcome these disadvantages, we transfected primary HMF with the E6 and E7 genes of the oncogenic human papillomavirus (HPV) 16. Successful transfection was demonstrated in 3 of 12 experiments by detection of E6-E7 gene transcription with nucleic acid sequence based amplification (NASBA). No significant change of phenotype was noted in the emerging cell lines (HMF(1226D), HMF(1321D), HMF(1226K)), but their in vitro lifespan was increased by 20 to 30 population doublings until cells entered crisis. A single subclone of HMF(1226K) had a transformed phenotype and continued to proliferate indefinitely. This subclone (HMF(1226K/I)) was considered to be immortalized and telomerase activity was detected. Despite the increased risk of mutations due to abrogation of p53 function, HMF(1226K/I) and the HMF lines with an increased lifespan retained the properties of primary HMF cells, as they expressed fibroblast markers (prolyl-4-hydroxylase, vimentin), cytokines (interleukin 1 alpha, 6, 8), and angiotensin II receptors and still were permissive for coxsackievirus B3 infection.

The function of type I interferons in antimicrobial immunity

Type I interferons (IFN-alpha and IFN-beta) were originally described as potent antiviral substances, which are produced upon infection of animal cells with viruses. Despite a large body of literature that has accumulated during the past 25 years, their regulatory function in the immune system is still much less appreciated. Recent studies have highlighted the production of type I IFNs, their function in the immune response to infectious agents and the target cells of these interferons. Type I IFNs clearly affect the release of proinflammatory cytokines or nitric oxide by dendritic cells and macrophages, the capacity of type II interferon (IFN-gamma) to activate phagocytes, the differentiation of T helper cells and the innate control of non-viral pathogens.

Transient induction of cytokine production in human myocardial fibroblasts by coxsackievirus B3

Cytokine expression in enterovirus infections of the heart may trigger inflammation and have detrimental effects on myocytes. However, the induction of cytokines in human myocardial cells by cardiotropic enteroviruses, for example, Coxsackievirus B3 (CVB3), was not yet demonstrated. Fibroblasts are the predominant cell type of the myocardial interstitium before inflammatory infiltration develops. Hence, we investigated, by enzyme immunoassays, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and nucleic acid sequence-based amplification (NASBA), whether CVB3 induces cytokine expression in cultured human myocardial fibroblasts. As early as 3 hours after infection, RT-qPCR demonstrated a 2-fold increase of interleukin (IL)-6 and IL-8 mRNA compared with basal transcription, resulting in a significant increase of IL-6 and IL-8 to a median level of 1500 pg/mL (range, 1246 to 1858) and 529 pg/mL (range, 428 to 601) in culture supernatants, respectively. IL-6 and IL-8 expression returned to basal levels within 3 and 5 days, respectively, despite a persistent (carrier-state) CVB3 infection. For comparison, IL-6 and IL-8 were induced in dermal fibroblasts later than 3 days after CVB3 infection. Although the low-level IL-1alpha transcription of myocardial fibroblasts was not significantly increased, IL-1alpha was released from cells to culture supernatants 5 days after infection. Furthermore, a suppression of interferon-beta transcription was demonstrated up to 24 hours after CVB3 infection of myocardial fibroblasts by highly sensitive NASBA. In conclusion, our results demonstrate a heart-specific pattern of a rapid and transient induction of proinflammatory cytokines after CVB3 infection, whereas the expression of protective interferon-beta was suppressed by CVB3.

Inducible Nitric Oxide Synthase Protection Against Coxsackievirus Pancreatitis

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.

Activation of the Jak-Stat pathway in cells that exhibit selective sensitivity to the antiviral effects of IFN-beta compared with IFN-alpha

We determined whether selective activation of components of the Jak-Stat pathway by different type I interferons (IFN) occurs in human myocardial fibroblasts that exhibit much higher sensitivity to the antiviral effects of IFN-beta than of IFN-alpha. Similar levels of activation of the Tyk2 kinase and the Stat3 transcription factor were induced in response to either IFN-beta or IFN-alpha treatment. However, activation of the Jak1 tyrosine kinase was detectable only in IFN-beta-treated but not IFN-alpha-treated cells. Consistent with this, tyrosine phosphorylation of Stat1 and Stat2 and formation of the IFN-stimulated gene factor 3 (ISGF3) complex occurred to a much higher degree in response to IFN-beta stimulation. These findings demonstrate that differential activation of distinct components of the Jak-Stat pathway by different type I IFN can occur. Furthermore, they strongly suggest that such selective activation accounts for the occurrence of differences in the antiviral properties of distinct type I IFN in certain cell types.

The role of inducible nitric oxide synthase in the host response to Coxsackievirus myocarditis

The host response to Coxsackievirus infection is complex, including T lymphocytes, B lymphocytes, natural killer cells, and macrophages. Although Coxsackievirus infection induces expression of inducible nitric oxide synthase (NOS2; EC 1.14.13.39) in macrophages, the precise role of NOS2 in the host response to Coxsackievirus myocarditis has been unclear. We show, by using mice homozygous for a disrupted NOS2 allele, that Coxsackievirus replicates to higher titers in NOS2(-/-) mice, that the host lacking NOS2 clears virus more slowly than the wild-type host, and that myocarditis is much more severe in infected NOS2(-/-) mice. These data show that NOS2 is crucial for the host response to Coxsackievirus in the mouse.

Antiviral activity of WIN 54954 in coxsackievirus B2 carrier state infected human myocardial fibroblasts

Persistent infections with a cardiotropic enterovirus, e.g. coxsackievirus B2 (CVB2), cause chronic myocarditis and eventually congestive heart failure. Therefore, the antiviral activity of WIN 54954, a capsid binding antiviral agent that inhibits enterovirus uncoating, was studied in persistently CVB2-infected cultures of human myocardial fibroblasts. Cultures displayed a typical carrier state infection with virus titers of 3.9 +/- 1.6 x 10(5) plaque forming units (PFU)/ml and 0.99% infected cells. WIN 54954 (0.025-1 microg/ml) application was started 7 days after infection of the cultures. Compared to the WIN 54954 concentration resulting in a 90% plaque number reduction (EC90 = 0.197 microg/ml) in acutely infected Vero cells, WIN 54954 reduced virus yields of myocardial fibroblast cultures more efficiently, e.g. more than 100 fold (99%) with 0.025 microg/ml after 4 days of application. Antiviral effects of WIN 54954 increased with application time and at 0.025 microg/ml Win 54954 completely inhibited infectious virus progeny after 16 days. Increasing the WIN 54954 concentration up to 1 microg/ml did not cause a greater inhibition of virus replication. In situ hybridization demonstrated that at 0.1 microg/ml WIN 54954 reduced the number of infected cells from 0.99 to 0.18%, although a complete eradication of CVB2-infected cells was not achieved at concentrations as high as 1 microg/ml. In conclusion, the results indicate that low concentrations of WIN 54954 are effective in treating persistent enterovirus infections of myocardial fibroblasts, although a complete eradication of the infection is not achieved with WIN 54954 as a single antiviral agent.

Inhibition of coxsackievirus B3 carrier state infection of cultured human myocardial fibroblasts by ribavirin and human natural interferon-alpha

As enterovirus infections of the heart cause myocarditis and eventually congestive heart failure, the antiviral activity of ribavirin was studied in coxsackie virus B3 (CVB3)-infected carrier cultures of human myocardial fibroblasts. Cultures were infected 7 days before application of ribavirin and effects were evaluated over a period of 16 days by plaque assays and in situ hybridization. Compared to the low antiviral activity in HeLa cells, ribavirin was highly active in reducing infectious virus yields in human myocardial fibroblasts, for example, to 2.0 x 10(3) pfu/ml with 25 microg/ml and to 1.3 x 10(2) pfu/ml with 50 microg/ml (4.3 x 10(4) pfu/ml in infected controls). Moreover, 100 microg ribavirin/ml completely suppressed infectious virus progeny in two of three cultures, and reduced the number of infected cells from 14.3 to 0.3% as determined by in situ hybridization, whereas up to 3200 microg ribavirin/ml did not result in a significant cytotoxic effect. Interaction with interferon-alpha (IFN-alpha) was additive to slightly synergistic in reducing the number of infected cells and virus yields. In conclusion, our results suggest a cell-specific high activity of ribavirin in human myocardial fibroblasts and indicate the importance of using organ-specific cells for testing antiviral agents in myocarditis. Furthermore, the usefulness of in situ hybridization for determining the long term effects of antivirals in carrier state cell cultures was demonstrated.