Mitigated viral myocarditis in A/J mice by the immunoproteasome inhibitor ONX 0914 depends on inhibition of systemic inflammatory responses in CoxsackievirusB3 infection

A preclinical model of troponin I-induced myocarditis (AM) revealed a prominent role of the immunoproteasome (ip), the main immune cell-resident proteasome isoform, in heart-directed autoimmunity. Viral infection of the heart is a known trigger of cardiac autoimmunity, with the ip enhancing systemic inflammatory responses after infection with a cardiotropic coxsackievirusB3 (CV). Here, we used ip-deficient A/J-LMP7-/- mice to investigate the role of ip-mediated effects on adaptive immunity in CV-triggered myocarditis and found no alteration of the inflammatory heart tissue damage or cardiac function in comparison to wild-type controls. Aiming to define the impact of the systemic inflammatory storm under the control of ip proteolysis during CV infection, we targeted the ip in A/J mice with the inhibitor ONX 0914 after the first cycle of infection, when systemic inflammation has set in, well before cardiac inflammation. During established acute myocarditis, the ONX 0914 treatment group had the same reduction in cardiac output as the controls, with inflammatory responses in heart tissue being unaffected by the compound. Based on these findings and with regard to the known anti-inflammatory role of ONX 0914 in CV infection, we conclude that the efficacy of ip inhibitors for CV-triggered myocarditis in A/J mice relies on their immunomodulatory effects on the systemic inflammatory reaction.

MicroRNA-30a Modulates Type I Interferon Responses to Facilitate Coxsackievirus B3 Replication Via Targeting Tripartite Motif Protein 25

Viral myocarditis is caused by a viral infection and characterized by the inflammation of the myocardium. Coxsackievirus B3 (CVB3) infection is one of the most common among the infections caused by this virus. The host's early innate immune response to CVB3 infection particularly depends on the functions of type I interferons (IFNs). In this study, we report that a host microRNA, miR-30a, was upregulated by CVB3 to facilitate its replication. We demonstrated that miR-30a was a potent negative regulator of IFN-I signaling by targeting tripartite motif protein 25 (TRIM25). In addition, we found that TRIM25 overexpression significantly suppressed CVB3 replication, whereas TRIM25 knockdown increased viral titer and VP1 protein expression. MiR-30a inhibits the expression of TRIM25 and TRIM25-mediated retinoic acid-inducible gene (RIG)-I ubiquitination to suppress IFN-β activation and production, thereby resulting in the enhancement of CVB3 replication. These results indicate the proviral role of miR-30a in modulating CVB3 infection for the first time. This not only provides a new strategy followed by CVB3 in order to modulate IFN-I-mediated antiviral immune responses by engaging host miR-30a but also improves our understanding of its pathogenesis.

An ERK-p38 subnetwork coordinates host cell apoptosis and necrosis during coxsackievirus B3 infection

The host response to a virus is determined by intracellular signaling pathways that are modified during infection. These pathways converge as networks and produce interdependent phenotypes, making it difficult to link virus-induced signals and responses at a systems level. Coxsackievirus B3 (CVB3) infection induces death of cardiomyocytes, causing tissue damage and virus dissemination, through incompletely characterized host cell signaling networks. We built a statistical model that quantitatively predicts cardiomyocyte responses from time-dependent measurements of phosphorylation events modified by CVB3. Model analysis revealed that CVB3-stimulated cytotoxicity involves tight coupling between the host ERK and p38 MAPK pathways, which are generally thought to control distinct cellular responses. The kinase ERK5 requires p38 kinase activity and inhibits apoptosis caused by CVB3 infection. By contrast, p38 indirectly promotes apoptosis via ERK1/2 inhibition but directly causes CVB3-induced necrosis. Thus, the cellular events governing pathogenesis are revealed when virus-host programs are monitored systematically and deconvolved mathematically.

Neuromyelitis optica preceded by hyperCKemia and a possible association with coxsackie virus group A10 infection

We report the case of a 48-year-old woman presenting with an elevated serum creatine kinase level (hyperCKemia) associated with an initial attack of neuromyelitis optica (NMO). The patient initially showed general fatigue with fever. Laboratory findings showed hyperCKemia and subsequently she developed a slight weakness of both lower limbs and reduced vision. Autoantibodies against aquaporin 4 were found in her serum, and a retrospective examination of viral titers indicated a possible coxsackie virus group A10 infection. The present case suggests that hyperCKemia-mediated disease onset is involved in some patients with NMO, and furthermore, it may be related to muscular destruction associated with viral infection.

[Expression of matrix metalloproteinase-9 in myocardium of mice with viral myocarditis]

OBJECTIVE

To investigate the dynamic changes of expression of matrix metalloproteinases-9 in myocardium of mice with viral myocarditis (VMC) and its significance in the pathogenesis of viral myocarditis.

METHODS

VMC model was prepared by an injection of CVB3 in BALB/C mice. The mice receiving an injection of culture solution without virus were used as the control group. Cardiac tissues were obtained 7, 14, 21 and 28 days after injection and made into paraffin sections. Myocardial histopathologic changes were observed by hematoxylin-eosin staining and Masson staining. The expression of MMP-9, type I collagen and type III collagen in cardiac tissues were quantified by SABC immunohistochemical method.

RESULTS

The expression of MMP-9 in the VMC model group was observed on the 7th day, reached a peak on the 14th day, and was significantly higher than that in the control group at all time points (P<0.05). Compared with the control group, the expression of type I collagen in the VMC model group was up-regulated on the 21st day and reached a peak on the 28th day (P<0.05). The expression of type III collagen in the VMC model group was significantly higher than that in the control group on the 28th day (P<0.05). The expression of MMP-9 was positively correlated with myocardial histopathologic scores (r=0.832, P<0.05) and negatively correlated with type I collagen expression (r=-0.791, P<0.05).

CONCLUSIONS

MMP-9 is over-expressed at the early stage in VMC mice, and participates in the pathological process of VMC through mediating the degradation metabolism of type I collagen. It may be an important factor that leads to myocardial collagen remodeling and myocardial fibrosis.

Melanoma differentiation-associated protein-5 (MDA-5) limits early viral replication but is not essential for the induction of type 1 interferons after Coxsackievirus infection

Coxsackievirus infections are associated with severe diseases such as myocarditis, meningitis and pancreatitis. To study the contribution of the intracellular viral sensor melanoma differentiation-associated protein-5 (MDA-5) in the host immune response to Coxsackievirus B3 (CVB3) we infected C57BL/6 and 129/SvJ mice lacking mda-5. Mice deficient in MDA-5 showed a dramatically increased susceptibility to CVB3 infection. The loss of MDA-5 allowed the virus to replicate faster, resulting in increased liver and pancreas damage and heightened mortality. MDA-5 was not absolutely required for the induction of type 1 interferons (IFNs), but essential for the production of maximal levels of systemic IFN-alpha early after infection. Taken together, our findings indicate that MDA-5 plays an important role in the host immune response to CVB3 by preventing early virus replication and limiting tissue pathology.

Glycerol-3-phosphate acyltransferase 1 is essential for the immune response to infection with coxsackievirus B3 in mice

Livers and hearts from mice deficient in glycerol-3-phosphate acyltransferase 1 (GPAT1; Gpat1(-/-)) have a decreased content of glycerolipid intermediates and triacylglycerol, an altered composition of liver phospholipids, and elevated markers of oxidative stress. Compared with control C57BL/6 mice, infection of Gpat1(-/-) mice with coxsackievirus B3 (CVB3) resulted in higher mortality, an approximately 50% increase in heart pathology, a significant increase in liver viral titers, and a 100-fold increase in heart viral titers. Moreover, heart mRNA levels for proinflammatory cytokines tumor necrosis factor-alpha, interleukin (IL)-6, and IL-1B were increased in the Gpat1(-/-) mice. Loss of Gpat1 also resulted in dysregulation of specific immune cells. Splenic dendritic cells from Gpat1(-/-) mice were fully capable of stimulating T cells from control mice; however, splenic T cells from Gpat1(-/-) mice were defective in their response to CVB3 antigen. Our data indicate that a lack of GPAT1 activity affects both innate and adaptive immune mechanisms. Innate mechanisms may be affected by altered membrane composition or host redox status, whereas the adaptive response may require GPAT1 activity itself.

Impact of myocardial inflammation on cytosolic and mitochondrial creatine kinase activity and expression

The disturbance of myocardial energy metabolism has been discussed as contributing to the progression of heart failure. Little however is known about the cardiac mitochondrial/cytosolic energy transfer in murine and human inflammatory heart disease. We examined the myocardial creatine kinase (CK) system, which connects mitochondrial ATP-producing and cytosolic ATP-consuming processes and is thus of central importance to the cellular energy homeostasis. The time course of expression and enzymatic activity of mitochondrial (mtCK) and cytosolic CK (cytCK) was investigated in Coxsackievirus B3 (CVB3)-infected SWR mice, which are susceptible to the development of chronic myocarditis. In addition, cytCK activity and isoform expression were analyzed in biopsies from patients with chronic inflammatory heart disease (n = 22). Cardiac CVB3 titer in CVB3-infected mice reached its maximum at 4 days post-infection (pi) and became undetectable at 28 days pi; cardiac inflammation cumulated 14 days pi but persisted through the 28-day survey. MtCK enzymatic activity was reduced by 40% without a concurrent decrease in mtCK protein during early and acute MC. Impaired mtCK activity was correlated with virus replication and increased level of interleukine 1beta (IL-1beta), tumor necrosis factor alpha (TNFalpha), and elevated catalase expression, a marker for intracellular oxidative stress. A reduction in cytCK activity of 48% was observed at day 14 pi and persisted to day 28 pi. This restriction was caused by a decrease in cytCK subunit expression but also by direct inhibition of specific cytCK activity. CytCK activity and expression were also reduced in myocardial biopsies from enterovirus genome-negative patients with inflammatory heart disease. The decrease in cytCK activity correlated with the number of infiltrating macrophages. Thus, viral infection and myocardial inflammation significantly influence the myocardial CK system via restriction of specific CK activity and down-regulation of cytCK protein. These changes may contribute to the progression of chronic inflammatory heart disease and malfunction of the heart.

TLR ligands act directly upon T cells to restore proliferation in the absence of protein kinase C-theta signaling and promote autoimmune myocarditis

The serine/threonine kinase, protein kinase C-theta (PKC-theta), plays a central role in the activation and differentiation of Th2 cells while being redundant in CD4+ and CD8+ antiviral responses. Recent evidence indicates that PKC-theta may however be required for some T cell-driven autoimmune responses. We have investigated the role of PKC-theta in the induction of autoimmune myocarditis induced by either Coxsackie B3 virus infection or immunization with alpha-myosin/CFA (experimental autoimmune myocarditis (EAM)). PKC-theta-deficient mice did not develop EAM as shown by impaired inflammatory cell infiltration into the heart, reduced CD4+ T cell IL-17 production, and the absence of a myosin-specific Ab response. Comparatively, PKC-theta was not essential for both early and late-phase Coxsackie virus-induced myocarditis. We sought to find alternate pathways of immune stimulation that might reconcile the differential requirements for PKC-theta in these two disease models. We found systemic administration of the TLR ligand CpG restored EAM in PKC-theta-deficient mice. CpG could act directly upon TLR9-expressing T cells to restore proliferation and up-regulation of Bcl-x(L), but exogenous IL-6 and TGF-beta was required for Th17 cell differentiation. Taken together, these results indicate that TLR-mediated activation of T cells can directly overcome the requirement for PKC-theta signaling and, combined with the dendritic cell-derived cytokine milieu, can promote the development of autoimmunity.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in coxsackievirus-induced myocarditis

BACKGROUND

Coxsackievirus B3 (CVB3) is the major causative agent of myocarditis in humans. In the mouse model, the inflammatory phase of myocarditis results in extensive damage to the heart and triggers profound extracellular matrix (ECM) remodeling, which may ultimately lead to dilated cardiomyopathy. Matrix metalloproteinases (MMPs) are regulators of the ECM and can degrade all the components in the matrix.

METHODS

Adolescent male mice were infected with cardiovirulent CVB3 and sacrificed at 3, 9, and 30 days post infection (pi). Transcription of MMP-2, MMP-9, and MMP-12 was assessed by reverse-transcriptase polymerase chain reaction (RT-PCR). Protein expression of these enzymes was examined using immunohistochemistry, and the activation status of MMP-2 and MMP-9 was assessed using gelatin zymography. Tissue inhibitors of metalloproteinases (TIMPs) were analyzed using immunoblotting assays. Myocarditic hearts were also stained with picrosirius red and viewed under polarizing light to examine the collagen network.

RESULTS

MMP-2, MMP-9, and MMP-12 transcription was increased at 9 days pi, as determined by RT-PCR. Immunohistochemistry confirmed an increase in translation of these MMP species, and zymographic analysis further showed elevated activation of MMP-2 and MMP-9 following CVB3 infection. TIMP-3 and TIMP-4 expression was down-regulated, while TIMP-1 and TIMP-2 remained constant throughout the infection. Mouse hearts stained with picrosirius red showed an increase in total amount of collagen during the acute phase of infection and disrupted fibrils at later timepoints.

CONCLUSION

After CVB3 infection, ECM remodeling is triggered, and this response may involve increased expression and activation of MMPs.

Structure and dynamics of coxsackievirus B4 2A proteinase, an enyzme involved in the etiology of heart disease

The 2A proteinases (2A(pro)) from the picornavirus family are multifunctional cysteine proteinases that perform essential roles during viral replication, involving viral polyprotein self-processing and shutting down host cell protein synthesis through cleavage of the eukaryotic initiation factor 4G (eIF4G) proteins. Coxsackievirus B4 (CVB4) 2A(pro) also cleaves heart muscle dystrophin, leading to cytoskeletal dysfunction and the symptoms of human acquired dilated cardiomyopathy. We have determined the solution structure of CVB4 2A(pro) (extending in an N-terminal direction to include the C-terminal eight residues of CVB4 VP1, which completes the VP1-2A(pro) substrate region). In terms of overall fold, it is similar to the crystal structure of the mature human rhinovirus serotype 2 (HRV2) 2A(pro), but the relatively low level (40%) of sequence identity leads to a substantially different surface. We show that differences in the cI-to-eI2 loop between HRV2 and CVB4 2A(pro) translate to differences in the mechanism of eIF4GI recognition. Additionally, the nuclear magnetic resonance relaxation properties of CVB4 2A(pro), particularly of residues G1 to S7, F64 to S67, and P107 to G111, reveal that the substrate region is exchanging in and out of a conformation in which it occupies the active site with association and dissociation rates in the range of 100 to 1,000 s(-1). This exchange influences the conformation of the active site and points to a mechanism for how self-processing can occur efficiently while product inhibition is avoided.

Common viral infection affects pentabrominated diphenyl ether (PBDE) distribution and metabolic and hormonal activities in mice

A murine model infection with the human coxsackievirus B3 (CB3) has been shown to change uptake and tissue distribution of several environmental pollutants, in some cases followed by an aggravated disease. In this study, the model was tested for polybrominated diphenyl ethers (PBDEs), which we know are absorbed from the gastro-intestinal tract and further distributed throughout the body. On day 0, female Balb/c mice were infected with CB3; on day 1 of the infection, they were dosed orally with approximately 200 microg/kgbody weight (bw) (ca. 0.52 microCi) of 14C-labelled 2,2',4,4',5-pentabromodiphenyl ether (14C-BDE-99); and on day 3 of the infection, they were sacrificed for studies of 14C-BDE-99 distribution. In comparison with control values, 14C-BDE-99 concentrations were altered in the liver (186%, p < 0.05), lungs (47%, p < 0.05) and pancreas (51%, p < 0.05), but no change was seen in the blood, brain, heart, spleen, thymus or kidneys. Moreover, on day 3, plasma thyroxine (T4) levels (33%, p < 0.001), as well as ethoxyresorufin-O-dealkylase (EROD) (17%, p < 0.001) and pentoxyresorufin O-dealkylase (PROD) (31%, p < 0.001) activities were much lower in infected compared to non-infected control mice. It is suggested that the change in tissue distribution of 14C-BDE-99 as a result of the infection may be caused by an infection-induced specific change in the hepatic enzyme activities affecting this PBDE congener. The mechanism for virally induced T4 changes remains, however, unclear. The presented infection-induced alteration in distribution, which is different from other environmental pollutants (e.g., dioxin, acrylamide and cadmium), may have consequences for PBDEs toxicity, especially in relation to microsomal enzyme and thyroid hormone activities.

RNase L and double-stranded RNA-dependent protein kinase exert complementary roles in islet cell defense during coxsackievirus infection

Coxsackievirus (CV) is an important human pathogen that has been linked to the development of autoimmunity. An intact pancreatic beta cell IFN response is critical for islet cell survival and protection from type 1 diabetes following CV infection. In this study, we show that IFNs trigger an antiviral state in beta cells by inducing the expression of proteins involved in intracellular antiviral defense. Specifically, we demonstrate that 2',5'-oligoadenylate synthetases (2-5AS), RNase L, and dsRNA-dependent protein kinase (PKR) are expressed by pancreatic islet cells and that IFNs (IFN-alpha and IFN-gamma) increase the expression of 2-5AS and PKR, but not RNase L. Moreover, our in vitro studies uncovered that these pathways play important roles in providing unique and complementary antiviral activities that critically regulate the outcome of CV infection. The 2-5AS/RNase L pathway was critical for IFN-alpha-mediated islet cell resistance from CV serotype B4 (CVB4) infection and replication, whereas an intact PKR pathway was required for efficient IFN-gamma-mediated repression of CVB4 infection and replication. Finally, we show that the 2-5AS/RNase L and the PKR pathways play important roles for host survival during a challenge with CVB4. In conclusion, this study has dissected the pathways used by distinct antiviral signals and linked their expression to defense against CVB4.

A critical role for inducible nitric oxide synthase in host survival following coxsackievirus B4 infection

Coxsackieviral infections have been linked etiologically to multiple diseases. The serotype CB4 is associated with acute pancreatitis and autoimmune type 1 diabetes. To delineate the mechanisms of host survival after an acute infection with CB4 (strain E2), we have investigated the role of nitric oxide (NO), generated by the inducible form of nitric oxide synthase (NOS2), in viral clearance and pancreatic beta-cell maintenance. Mice deficient in NOS2 (NOS2-/- mice) and their wild-type (wt) counterparts were injected with CB4, after which both groups developed severe pancreatitis, hepatitis, and hypoglycemia within 3 days. Within 4 to 7 days postinfection (p.i.), most of the NOS2-/- mice died and at a strikingly higher mortality rate than wt mice. Histological examination of pancreata from both infected NOS2-/- and infected wt mice revealed early and complete destruction of the pancreatic acinar tissue, but intact, insulin-stained islets. When examined up to 8 weeks p.i., neither surviving NOS2-/-mice nor surviving wt mice developed hyperglycemia. However, the clearance of infectious CB4 was different between the mice. The spleens of NOS2-/- survivors were cleared of infectious virus with kinetics similar to that of wt mice, but the livers, pancreata, kidneys, and hearts of the NOS2-/- groups cleared virus more slowly than those of the wt group. This delayed clearance was particularly prominent in the livers of infected NOS2-/- mice, which also showed prolonged histopathological features of viral hepatitis. Taken together, this outcome suggests that NOS2 (and NO) is not required for the prevention of pancreatic beta-cell depletion after CB4 infection. Instead the critical actions of NOS2 apparently occur early in the host immune response, allowing mice to survive and clear virus. Moreover, the data support the existence of an organ-specific dependency on NO for a rapid clearance of CB4.

Nutritionally induced oxidative stress: effect on viral disease

It has long been known that the nutritional status of the host can influence both susceptibility to infectious disease and the severity of the disease if contracted. In studies of coxsackievirus infection and selenium deficiency in mice, we found that mice fed a selenium-deficient diet developed myocarditis, but mice fed a diet adequate in selenium did not. Similarly, mice fed a diet deficient in vitamin E developed myocarditis, but mice fed a diet with adequate vitamin E did not. The epidemic of optic and peripheral neuropathy that occurred in Cuba in the early 1990s provides another example of how the nutritional status of the host may affect the impact of a virus. Patients who developed neuropathy had lower blood concentrations of riboflavin, vitamin E, selenium, alpha- and beta-carotenes, and the carotenoid lycopene, which suggests that the disease was associated with an impairment of protective antioxidant pathways. After supplementation of the population with these nutrients, the disease began to subside. The nutritional status of the host can have a profound influence on a virus, so that a normally avirulent virus becomes virulent because of changes in the viral genome. Our studies suggest that outbreaks of disease attributed to a nutritional deficiency may actually result from infection by a virus that has become pathogenic by replicating in a nutritionally deficient host.

Expression of inducible nitric oxide synthase in experimental viral myocarditis

Nitric oxide (NO) is an important bioactive molecule with regulatory, cytotoxic or cytoprotective properties. In virus-induced myocarditis, NO mediates host defense mechanisms against the infection or causes cardiac dysfunctions. NO is synthesized from L-arginine by the enzyme nitric oxide synthase (NOS). The expression of the inducible form of the nitric oxide synthase (iNOS) is regulated by cytokines, involved in the complex myocardial immune response to enterovirus infections. The present study was undertaken to characterize the role of iNOS and NO in the murine model of viral myocarditis induced by coxsackievirus B3 (CVB3). In response to CVB3 infection we investigated the time course of iNOS induction in correlation with cytokine mRNA expression (TNF-alpha, IL-1 alpha, IFN-gamma, TGF-beta) in the heart of NMRI mice by RT-PCR. Positive PCR signals for viral RNA were found in the acute and chronic stage of disease by seminested PCR, indicating the persistence of viral genome. We found distinct expression of iNOS at all time points (1, 2, 3, 4, 7, 14, 28, 56, 98 days post infection [p.i.]). Higher iNOS mRNA levels were identified between days 4 until 28 p.i. in comparison to day 56 and 98 p.i. using densitometric values. The mRNA of the inflammatory cytokines TNF-alpha, IL-1 alpha, IFN-gamma appeared at days 1, 4, and 7 p.i., peaked at day 7 p.i. and persisted until day 98 p.i. Similar like the iNOS mRNA pattern was the expression profile of TGF-beta. Using in situ hybridization and immunohistochemistry iNOS was localized in infiltrates, vascular endothelial cells, smooth muscle cells, myocytes and throughout the interstitial spaces between myocardial fibers in the heart sections of NMRI mice. Increased levels of NO were measured as total nitrate/nitrite concentration in the sera of mice from day 7 until day 28 p.i.

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.

Induction of myocardial nitric oxide synthase by Coxsackie B3 virus in mice

BACKGROUND

Inducible nitric oxide synthase (iNOS) expression is regulated by cytokines. This study investigated whether Coxsackie group B virus (CVB) myocarditis resulted in an environment suitable for induction of NOS in the murine heart.

MATERIALS AND METHODS

Myocardium was removed from mice infected with CVB3 and from controls. Histology, reverse transcriptase polymerase reaction (RT-PCR) for murine iNOS, NOS enzyme activity and immunohistochemistry were assessed.

RESULTS

Histology revealed severe myocarditis 7 days after infection with CVB3 but not in controls. RT-PCR using primers for murine iNOS detected iNOS mRNA in infected mice but not in controls. Calcium-independent NOS activity increased by day 5 after infection with a peak at day 7. Calcium-dependent NOS activity was present throughout, with a trend to lower levels during peak calcium-independent activity. Immunohistochemistry revealed iNOS to be localized to inflammatory cells rather than to myocytes.

CONCLUSION

This study demonstrates the development of calcium-independent NOS activity and de novo gene transcription for iNOS in the murine myocardium in response to CVB3 infection. The nitric oxide produced at such high output may act at times as part of the immune defence as an antiviral agent and may be toxic to host tissue.

The study of the diaphoresis and leucinaminopeptidasis activity in experimental enteroviroses

This paper studies, through histochemistry methods, the answer of some enzymes (Diaphoresis and Leuciaminopeptidasis) from intestinal wall structure to the viral aggression experimentally obtained. The most characteristic aspects occur at the intestinal mucous membrane level. The microbial aggression stimulates both macrophagous and immune processes, particularly those of humoral type. Thus, a cellular defence phagocyte and immune barrier with release of Ig and especially IgA is achieved subepithelial.

Histoenzymatic changes at splenic level in experimental enterovirosis

An experimental model was established to observe the lymphoplasmocytic and macrophage reaction at distance, in spleen, following the intraperitoneal administration of Coxsackie B3 virus. In the aftermath of the experimental viral aggression the thymo-dependent immune system did not seem altered, while the thymo-independent one was severely challenged. The immune reaction of the humoral type was accompanied by a stimulation of the macrophagous type-cells.

Nitric oxide and murine coxsackievirus B3 myocarditis: aggravation of myocarditis by inhibition of nitric oxide synthase

OBJECTIVES

This study sought to investigate the effects of nitric oxide inhibition in a murine model of coxsackievirus B3 myocarditis.

BACKGROUND

Little is known about the contribution of nitric oxide to the pathophysiology of myocarditis.

METHODS

Antiviral activity was tested in vitro using nitric oxide inhibition by treatment with activated macrophages of NG-nitro-L-arginine methyl ester. In the in vivo experiments, NG-nitro-L-arginine methyl ester and NG-nitro-D-arginine methyl ester (both at 100 micrograms/ml) were administered to C3H/He mice early (days 0 to 14) and late (days 14 to 35) after infection with coxsackievirus B3.

RESULTS

In the in vitro experiments with interferon-gamma- and lipopolysaccharide-induced activated murine macrophages, treatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, but not its inactive enantiomer NG-nitro-D-arginine methyl ester, restored coxsackievirus B3 titers. In the in vivo experiments in the early treatment group, myocardial virus titers were higher in NG-nitro-L-arginine methyl ester-treated than infected untreated animals, and both inflammatory cell infiltration and necrosis were more severe. In the late treatment group, more severe necrosis and more dense myocardial and perivascular fibrosis were observed in NG-nitro-L-arginine methyl ester-treated than in infected untreated animals. NG-Nitro-D-arginine methyl ester administration was ineffective.

CONCLUSIONS

Nitric oxide inhibition increases myocardial virus titers, resulting in the aggravation of cardiac pathology in the early stage of coxsackievirus B3 myocarditis. In the late stage, it induces more severe cardiomyopathic lesions. Nitric oxide plays a defensive role in the pathogenesis of coxsackievirus B3 myocarditis.

Expression of nitric oxide synthase in a murine model of viral myocarditis induced by coxsackievirus B3

Nitric oxide is known to participate in the immune and inflammatory processes. In this study, we investigated the production of nitric oxide (NO) in murine viral myocarditis induced by coxsackievirus B3. The expression of inducible NO synthase (iNOS) mRNA in the heart first appeared on day 4 after virus inoculation and it was detectable for one month by reverse transcriptase-polymerase chain reaction (RT-PCR) methods. iNOS activity which was determined by the conversion of L-[3H]arginine to L-[3H]citrulline was increased on day 4 and revealed its peak on day 8. Immunohistochemistry on day 7 showed increased iNOS staining mainly in infiltrating macrophages and polymorphonuclear leukocytes. Thus, NO is thought to be produced in the heart and play an important role in a murine model of coxsackievirus B3-induced viral myocarditis.

Coxsackievirus B4 alters pancreatic glutamate decarboxylase expression in mice soon after infection

The 64,000-M(r) (64K) islet autoantigen, which is considered to be a target protein of beta cell destruction in insulin-dependent diabetes mellitus (IDDM), has recently been identified as the enzyme glutamic acid decarboxylase (GAD). We reported a two- to three-fold increased expression of the antigen in islets of diabetes-susceptible mice following infection with a diabetogenic strain of Coxsackievirus B4 (CB4) at 72-h postinfection (p.i.), a time point of active virus replication in the islets. Most of the infected animals subsequently developed 64K autoantibodies and hyperglycemia. Since the infection increases 64K expression, we have analysed immunoreactive GAD expression with a panel of peptide antisera and two widely-used polyclonal antisera against GAD, and measured GAD activity in the brain, pancreas and islets of these mice. Two isoforms, GAD65 and GAD67, are detected in these tissues from non-infected mice. Both GADs are also present in the infected mice brain at 72 h p.i.; however, their islets contain about three-fold more GAD65, and essentially no detectable GAD67. GAD activity is significantly higher in the brain compared with whole pancreas or islets, and islet GAD activity is higher than pancreas GAD activity. The infection significantly reduces islet GAD activity, but not brain GAD activity. CB4-induced abnormalities in islet GAD expression may play a role in virus-induced diabetes.

[Diaphorase activity at the conjunctival level in an experimentally produced viral infection]

By Coxsackie virus type B3 subconjunctival administration it has been noticed the appearance of a antiviral defense mechanism, revealed by the presence in conjunctival chorion of lymphocytes, plasmocytes and active macrophages. It had also been studied by histochemical methods the responsive way at conjunctival level of NADH2-cytocrom-C-reductase (diaphorase) in experimentally obtained viral aggression. The injected virus has determined the stimulation of the activity of this enzyme at epithelial level, which play an important role in mucous conjunctival protection. The lymphocytes appearing in a great number presented an intense enzymatic reaction in chorion, which denotes a living synthetic and secretory metabolical activity.

[Ocular histoenzymatic research on an experimental viral attack]

We sought to investigate enzyme response appearing subsequent to sub-conjunctival administration of the Coxsackie B3 virus. This virus stimulates oxidising enzymes, diaphorase and leucin aminopeptidase, dihydrofolate reductase, and adenosinetriphosphatase. The most typical enzyme changes are been in the chorion of the conjunctival mucose and the corneal parenchyma there by showing that the virus, triggers local immune defence mechanisms. The appearance of highly active Langerhans cells around Bowman membrane and corneal tissue proves that the virus injected greatly stimulates the mobilisation of local immune mechanisms.

Coxsackie B-2 virus infection in rat beating heart cell culture

Beating rat heart cultures were prepared in vitro and infected with Coxsackie B-2 virus. The cells were evaluated in the post-infected period for changes in cardiac enzymes, alterations in beating frequency and cytotoxicity as measured by chromium 51 (51Cr) release. The cardiac enzymes, lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) were measured in infected and uninfected controls over a period of 120 h. Enzyme levels in the infected cells remained essentially the same for the first 42 h as compared to the controls. At this time, the LDH levels increased rapidly reaching 116 +/- 24.8 U/l while the controls remained at 46.9 +/- 9.7 U/l. Aspartate aminotransferase levels increased at a slower rate and obtained a level of 104 +/- 20.2 U/l compared to 66.6 +/- 13.2 U/l in the control. Visual evidence of cellular damage as measured by decreased beating frequencies and the appearance of cytopathic effect was first noted at 42 h post-infection. Complete loss of cardiac beats and maximal viral cytopathic effect occurred at 96 h post-infection. Cardiac cellular damage as measured by cytotoxicity assay was found to parallel those changes seen in cardiac enzymes. No significant changes in cytotoxicity were observed for the first 24 h; however, at 48 h increased release of 51Cr was noted and visual evidence of viral replication also was present. The cardiac enzyme changes noted in beating rat heart cells appear to be similar to those changes reported in patients with viral-induced myocardial disease.(ABSTRACT TRUNCATED AT 250 WORDS)

[Epidemic leg myalgia: a complication of influenza-like infections]

Following an influenza-like illness four patients developed severe pains in the calf muscles. All patients showed elevated levels of serum-creatinin-phosphokinase (CPK) and Coxsackie-B-virus-titers; with the exception of electromyographic abnormalities the other laboratory findings were normal. Because of the diagnosis, myalgia cruris epidemica, only symptomatic treatment was performed. Differential diagnostic and aetiological aspects are discussed.