Up-regulation of ectopic trypsins in the myocardium by influenza A virus infection triggers acute myocarditis

STAT1 regulates neutrophil gelatinase B-associated lipocalin induction in influenza-induced myocarditis

Influenza is a significant public health and economic threat around the world. Epidemiological studies have demonstrated a close association between influenza pandemics and cardiovascular mortality. Moreover, it has been shown that there is a decrease in cardiovascular mortality in high-risk patients following vaccination with the influenza vaccine. Here, we have investigated the role of anti-viral STAT1 signaling in influenza-induced myocarditis. Wild-type mice (C57BL/6) were infected with either influenza A/PR/8/34 or control, and cellular response and gene expression analysis from the heart samples were assessed 7 days later. The expression of interferon response genes STAT1, STAT2, Mx1, OASL2, ISG15, chemokines CCL2, CCL3, CXCL9 and CXCL10, and the frequency of neutrophils (CD45+CD11b+Ly6G+) and CD4+ T cells (CD45+CD4+) were all significantly increased in influenza-infected mice when compared to vehicle controls. These data suggest that influenza infection induces interferons, inflammatory chemokines, and cellular recruitment during influenza infection. We further investigated the role of STAT1 in influenza-induced myocarditis. The frequency of neutrophils and the levels of lipocalin 2 were significantly increased in STAT1-/- mice when compared to WT controls. Finally, we investigated the role of Lcn2 in viral-induced myocarditis. We found that in the absence of Lcn2, there was preserved cardiac function in Lcn2-/- mice when compared to WT controls. These data suggest that the absence of Lcn2 is cardioprotective during viral-induced myocarditis.

Association of respiratory infections and the impact of vaccinations on cardiovascular diseases

Influenza, pneumococcal, severe acute respiratory syndrome coronavirus 2, and respiratory syncytial virus infections are important causes of high morbidity and mortality in the elderly. Beyond the burden of infectious diseases, they are also associated with several non-infectious complications like cardiovascular events. A growing body of evidence in prospective studies and meta-analyses has shown the impact of influenza and pneumococcal vaccines on types of cardiovascular outcomes in the general population. Influenza vaccination showed a potential benefit for primary and secondary prevention of cardiovascular diseases across all ages. A reduced risk of cardiovascular events for individuals aged 65 years and older was associated with pneumococcal vaccination. Despite scientific evidence on the effectiveness, safety, and benefits of the vaccines and recommendations to vaccinate elderly patients and those with risk factors, vaccination rates remain sub-optimal in this population. Doubts about vaccine necessity or efficacy and concerns about possible adverse events in patients and physicians refer to delayed acceptance. Vaccination campaigns targeting increasing professional recommendations and public perceptions should be implemented in the coming years. The aim of this review paper is to summarize the effect of vaccination in the field of cardiovascular disease to achieve a higher vaccination rate in this patient population.

Aprotinin-Drug against Respiratory Diseases

Aprotinin (APR) was discovered in 1930. APR is an effective pan-protease inhibitor, a typical "magic shotgun". Until 2007, APR was widely used as an antithrombotic and anti-inflammatory drug in cardiac and noncardiac surgeries for reduction of bleeding and thus limiting the need for blood transfusion. The ability of APR to inhibit proteolytic activation of some viruses leads to its use as an antiviral drug for the prevention and treatment of acute respiratory virus infections. However, due to incompetent interpretation of several clinical trials followed by incredible controversy in the literature, the usage of APR was nearly stopped for a decade worldwide. In 2015-2020, after re-analysis of these clinical trials' data the restrictions in APR usage were lifted worldwide. This review discusses antiviral mechanisms of APR action and summarizes current knowledge and prospective regarding the use of APR treatment for diseases caused by RNA-containing viruses, including influenza and SARS-CoV-2 viruses, or as a part of combination antiviral treatment.

A Rare Case of Fulminant Myocarditis Caused by COVID-19 and Influenza B Co-infection

Coronavirus disease 2019 and influenza B can have similar presentations and are self-limited in most cases. They are rarely associated with fatal cardiovascular complications. Coronavirus and influenza B-induced myocarditis is a rare but reversible cause of cardiogenic shock. Early detection plus administration of antiviral agents and supportive care with mechanical circulatory support in the form of an intra-aortic balloon pump can be a lifesaving measure in myocarditis.

Transcriptomic profiling of cardiac tissues from SARS-CoV-2 patients identifies DNA damage

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known to present with pulmonary and extra-pulmonary organ complications. In comparison with the 2009 pandemic (pH1N1), SARS-CoV-2 infection is likely to lead to more severe disease, with multi-organ effects, including cardiovascular disease. SARS-CoV-2 has been associated with acute and long-term cardiovascular disease, but the molecular changes that govern this remain unknown. In this study, we investigated the host transcriptome landscape of cardiac tissues collected at rapid autopsy from seven SARS-CoV-2, two pH1N1, and six control patients using targeted spatial transcriptomics approaches. Although SARS-CoV-2 was not detected in cardiac tissue, host transcriptomics showed upregulation of genes associated with DNA damage and repair, heat shock, and M1-like macrophage infiltration in the cardiac tissues of COVID-19 patients. The DNA damage present in the SARS-CoV-2 patient samples, were further confirmed by γ-H2Ax immunohistochemistry. In comparison, pH1N1 showed upregulation of interferon-stimulated genes, in particular interferon and complement pathways, when compared with COVID-19 patients. These data demonstrate the emergence of distinct transcriptomic profiles in cardiac tissues of SARS-CoV-2 and pH1N1 influenza infection supporting the need for a greater understanding of the effects on extra-pulmonary organs, including the cardiovascular system of COVID-19 patients, to delineate the immunopathobiology of SARS-CoV-2 infection, and long term impact on health.

Influenza and cardiovascular disease pathophysiology: strings attached

A link between influenza infection and cardiovascular morbidity has been known for almost a century. This narrative review examined the cardiovascular complications associated with influenza and the potential mechanisms behind this relationship. The most common reported cardiovascular complications are cardiovascular death, myocardial infarction, and heart failure hospitalization. There are multiple proposed mechanisms driving the increased risk of cardiovascular complications. These mechanics involve influenza-specific effects such as direct cardiac infection and endothelial dysfunction leading to plaque destabilization and rupture, but also hypoxaemia and systemic inflammatory responses including increased metabolic demand, biomechanical stress, and hypercoagulability. The significance of the individual effects is unclear, and thus whether influenza directly or indirectly causes cardiovascular events is unknown. In conclusion, the risk of acute cardiovascular morbidity and mortality is elevated during influenza infection. The proposed underlying pathophysiological mechanisms support this association, but systemic responses to infection may drive this relationship.

Influenza vaccination is associated with a decreased risk of atrial fibrillation: A systematic review and meta-analysis

Background

Evidence from longitudinal studies has shown that influenza infection is linked to an increased risk of arrhythmia. Therefore, we aimed to assess the role of influenza vaccination in arrhythmia prevention.

Materials and methods

The PubMed, Embase, and Cochrane Library databases were searched to identify studies that investigated the potential effects of the influenza vaccine on arrhythmia risk published until October 25th, 2021. The study was registered with PROSPERO (CRD42022300815).

Results

One RCT with 2,532 patients and six observational studies with 3,167,445 patients were included. One RCT demonstrated a non-significant benefit of the influenza vaccine against arrhythmias [odds ratio (OR) = 0.43, 95% confidence interval (CI): 0.11–1.64; P = 0.20] in patients after myocardial infarction or those with high-risk stable coronary heart disease. A meta-analysis based on observational studies showed that vaccination was associated with a significantly lower risk of arrhythmia (OR: 0.82, 95% CI: 0.70–0.97; P = 0.02; I² = 76%). Additionally, subgroup analysis showed a decreased risk of atrial fibrillation (AF) (OR: 0.94, 95% CI: 0.90–0.98; P = 0.006; I² = 0%) and a non-significant but positive trend concerning ventricular arrhythmias (VAs) (OR: 0.68, 95% CI: 0.42–1.11; P = 0.12; I² = 85%) after influenza vaccination.

Conclusion

Based on the current evidence, influenza vaccination may be associated with a reduced risk of arrhythmia, especially AF. Influenza vaccination may be an effective tool for the prevention of arrhythmias. The effect of influenza vaccination on the risk of VAs and arrhythmias in patients at low risk for cardiovascular diseases should be further studied.

Systematic review registration

[https://www.crd.york.ac.uk/PROSPERO/], identifier [CRD42022300815].

Effects of atrial fibrillation on outcomes of influenza hospitalization

Background

There is little information available on AF and its association with outcomes in adult influenza hospitalizations.

Methods

The National Inpatient Sample was queried from years 2009–2018 to create a cohort of discharges containing an influenza diagnosis. AF was the primary exposure. Univariate and multivariate regression analysis was used to describe the association of AF with clinical and healthcare-resource outcomes. Finally, a doubly-robust analysis using average treatment effect on the treated (ATT) propensity score weighting was performed to verify the results of traditional regression analysis.

Results

After adjustment, the presence of AF during influenza hospitalization was associated with higher odds of in-hospital mortality (aOR 1.56, 95 % CI 1.49 – 1.65), acute respiratory failure (aOR 1.22, 95 % CI 1.19 – 1.25), acute respiratory failure with mechanical ventilation (aOR 1.37, 95 % CI 1.32 – 1.41), acute kidney injury (aOR 1.09, 95 % CI 1.06 – 1.12), acute kidney injury requiring dialysis (aOR 1.61, 95 % CI 1.46 – 1.78) and cardiogenic shock (aOR 1.90, 95 % CI 1.65 – 2.20, all p-values < 0.0001). These findings were validated in our propensity score analysis using ATT weights. The presence of AF was also associated with higher total charges and costs of hospitalization, as well as a significantly longer length of stay (all p-values < 0.0001).

Conclusion

AF is a cardiovascular comorbidity associated with worse clinical and healthcare resource outcomes in influenza requiring hospitalization. Its presence should be used to identify patients with influenza at risk of worse prognosis.

Fulminant myocarditis in adults: a narrative review

Fulminant myocarditis (FM) is an uncommon syndrome characterized by sudden and severe hemodynamic compromise secondary to acute myocardial inflammation, often presenting as profound cardiogenic shock, life-threatening ventricular arrhythmias and/or electrical storm. FM may be refractory to conventional therapies and require mechanical circulatory support (MCS). The immune system has been recognized as playing a pivotal role in the pathophysiology of myocarditis, leading to an increased focus on immunosuppressive treatment strategies. Recent data have highlighted not only the fact that FM has significantly worse outcomes than non-FM, but that prognosis and management strategies of FM are heavily dependent on histological subtype, placing greater emphasis on the role of endomyocardial biopsy in diagnosis. The impact of subtype on severity and prognosis will likewise influence how aggressively the myocarditis is managed, including whether MCS is warranted. Many patients with refractory cardiogenic shock secondary to FM end up requiring MCS, with venoarterial extracorporeal membrane oxygenation demonstrating favorable survival rates, particularly when initiated prior to the development of multiorgan failure. Among the challenges facing the field are the need to more precisely identify immunopathophysiological pathways in order to develop targeted therapies, and the need to better optimize the timing and management of MCS to minimize complications and maximize outcomes.

Myeloid Protease-Activated Receptor-2 Contributes to Influenza A Virus Pathology in Mice

Background

Innate immune responses to influenza A virus (IAV) infection are initiated in part by toll-like receptor 3 (TLR3). TLR3-dependent signaling induces an antiviral immune response and an NFκB-dependent inflammatory response. Protease-activated receptor 2 (PAR2) inhibits the antiviral response and enhances the inflammatory response. PAR2 deficiency protected mice during IAV infection. However, the PAR2 expressing cell-types contributing to IAV pathology in mice and the mechanism by which PAR2 contributes to IAV infection is unknown.

Methods

IAV infection was analyzed in global (Par2-/-), myeloid (Par2fl/fl;LysMCre+) and lung epithelial cell (EpC) Par2 deficient (Par2fl/fl;SPCCre+) mice and their respective controls (Par2+/+ and Par2fl/fl). In addition, the effect of PAR2 activation on polyinosinic-polycytidylic acid (poly I:C) activation of TLR3 was analyzed in bone marrow-derived macrophages (BMDM). Lastly, we determined the effect of PAR2 inhibition in wild-type (WT) mice.

Results

After IAV infection, Par2-/- and mice with myeloid Par2 deficiency exhibited increased survival compared to infected controls. The improved survival was associated with reduced proinflammatory mediators and reduced cellular infiltration in bronchoalveolar lavage fluid (BALF) of Par2-/- and Par2fl/fl;LysMCre+ 3 days post infection (dpi) compared to infected control mice. Interestingly, Par2fl/fl;SPCCre+ mice showed no survival benefit compared to Par2fl/fl. In vitro studies showed that Par2-/- BMDM produced less IL6 and IL12p40 than Par2+/+ BMDM after poly I:C stimulation. In addition, activation of PAR2 on Par2+/+ BMDM increased poly I:C induction of IL6 and IL12p40 compared to poly I:C stimulation alone. Importantly, PAR2 inhibition prior to IAV infection protect WT mice.

Conclusion

Global Par2 or myeloid cell but not lung EpC Par2 deficiency was associated with reduced BALF inflammatory markers and reduced IAV-induced mortality. Our study suggests that PAR2 may be a therapeutic target to reduce IAV pathology.

In Vivo Models to Study the Pathogenesis of Extra-Respiratory Complications of Influenza A Virus Infection

Animal models are an inimitable method to study the systemic pathogenesis of virus-induced disease. Extra-respiratory complications of influenza A virus infections are not extensively studied even though they are often associated with severe disease and mortality. Here we review and recommend mammalian animal models that can be used to study extra-respiratory complications of the central nervous system and cardiovascular system as well as involvement of the eye, placenta, fetus, lacteal gland, liver, pancreas, intestinal tract, and lymphoid tissues during influenza A virus infections.

A High-Fat Diet Increases Influenza A Virus-Associated Cardiovascular Damage

BACKGROUND

Influenza A virus (IAV) causes a wide range of extrarespiratory complications. However, the role of host factors in these complications of influenza virus infection remains to be defined.

METHODS

Here, we sought to use transcriptional profiling, virology, histology, and echocardiograms to investigate the role of a high-fat diet in IAV-associated cardiac damage.

RESULTS

Transcriptional profiling showed that, compared to their low-fat counterparts (LF mice), mice fed a high-fat diet (HF mice) had impairments in inflammatory signaling in the lung and heart after IAV infection. This was associated with increased viral titers in the heart, increased left ventricular mass, and thickening of the left ventricular wall in IAV-infected HF mice compared to both IAV-infected LF mice and uninfected HF mice. Retrospective analysis of clinical data revealed that cardiac complications were more common in patients with excess weight, an association which was significant in 2 out of 4 studies.

CONCLUSIONS

Together, these data provide the first evidence that a high-fat diet may be a risk factor for the development of IAV-associated cardiovascular damage and emphasizes the need for further clinical research in this area.

Human influenza A virus causes myocardial and cardiac-specific conduction system infections associated with early inflammation and premature death

AIMS

Human influenza A virus (hIAV) infection is associated with important cardiovascular complications, although cardiac infection pathophysiology is poorly understood. We aimed to study the ability of hIAV of different pathogenicity to infect the mouse heart, and establish the relationship between the infective capacity and the associated in vivo, cellular and molecular alterations.

METHODS AND RESULTS

We evaluated lung and heart viral titres in mice infected with either one of several hIAV strains inoculated intranasally. 3D reconstructions of infected cardiac tissue were used to identify viral proteins inside mouse cardiomyocytes, Purkinje cells, and cardiac vessels. Viral replication was measured in mouse cultured cardiomyocytes. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to confirm infection and study underlying molecular alterations associated with the in vivo electrophysiological phenotype. Pathogenic and attenuated hIAV strains infected and replicated in cardiomyocytes, Purkinje cells, and hiPSC-CMs. The infection was also present in cardiac endothelial cells. Remarkably, lung viral titres did not statistically correlate with viral titres in the mouse heart. The highly pathogenic human recombinant virus PAmut showed faster replication, higher level of inflammatory cytokines in cardiac tissue and higher viral titres in cardiac HL-1 mouse cells and hiPSC-CMs compared with PB2mut-attenuated virus. Correspondingly, cardiac conduction alterations were especially pronounced in PAmut-infected mice, associated with high mortality rates, compared with PB2mut-infected animals. Consistently, connexin43 and NaV1.5 expression decreased acutely in hiPSC-CMs infected with PAmut virus. YEM1L protease also decreased more rapidly and to lower levels in PAmut-infected hiPSC-CMs compared with PB2mut-infected cells, consistent with mitochondrial dysfunction. Human IAV infection did not increase myocardial fibrosis at 4-day post-infection, although PAmut-infected mice showed an early increase in mRNAs expression of lysyl oxidase.

CONCLUSION

Human IAV can infect the heart and cardiac-specific conduction system, which may contribute to cardiac complications and premature death.

Fecal host biomarkers predicting severity of Clostridioides difficile infection

Clostridioides difficile is a major cause of health care-associated diarrhea. Severity ranges from mild to life-threatening, but this variability remains poorly understood. Microbiologic diagnosis of C. difficile infection (CDI) is straightforward but offers little insight into the patient's prognosis or into pathophysiologic determinants of clinical trajectory. The aim of this study was to discover host-derived, CDI-specific fecal biomarkers involved in disease severity. Subjects without and with CDI diarrhea were recruited. CDI severity was based on Infectious Diseases Society of America/Society for Healthcare Epidemiology of America criteria. We developed a liquid chromatography tandem mass spectrometry approach to identify host-derived protein biomarkers from stool and applied it to diagnostic samples for cohort-wise comparison (CDI-negative vs. nonsevere CDI vs. severe CDI). Selected biomarkers were orthogonally confirmed and subsequently verified in a CDI mouse model. We identified a protein signature from stool, consisting of alpha-2-macroglobulin (A2MG), matrix metalloproteinase-7 (MMP-7), and alpha-1-antitrypsin (A1AT), that not only discriminates CDI-positive samples from non-CDI ones but also is potentially associated with disease severity. In the mouse model, this signature with the murine homologs of the corresponding proteins was also identified. A2MG, MMP-7, and A1AT serve as biomarkers in patients with CDI and define novel components of the host response that may determine disease severity.

Influenza Myocarditis: A Literature Review

Viral myocarditis is not uncommon but the role of the influenza virus in causing myocarditis is less studied. It is difficult to diagnose influenza myocarditis. Due to bacterial and viral co-infection during influenza outbreaks, it becomes more difficult to distinguish influenza myocarditis from other causes. Our article provides current information on influenza myocarditis. We did a literature search using appropriate terms and reviewed articles published by November 2020. Our study highlights the incidence of influenza myocarditis and the need to become aware of this condition, especially during epidemics and pandemics. Our study highlights that although influenza myocarditis is a rare condition, it can be fatal. There should be increased awareness about the condition. By the early diagnosis and treatment of influenza myocarditis, we can prevent fatal complications.

Immune Mechanisms in Cardiovascular Diseases Associated With Viral Infection

Influenza virus infection causes 3-5 million cases of severe illness and 250,000-500,000 deaths worldwide annually. Although pneumonia is the most common complication associated with influenza, there are several reports demonstrating increased risk for cardiovascular diseases. Several clinical case reports, as well as both prospective and retrospective studies, have shown that influenza can trigger cardiovascular events including myocardial infarction (MI), myocarditis, ventricular arrhythmia, and heart failure. A recent study has demonstrated that influenza-infected patients are at highest risk of having MI during the first seven days of diagnosis. Influenza virus infection induces a variety of pro-inflammatory cytokines and chemokines and recruitment of immune cells as part of the host immune response. Understanding the cellular and molecular mechanisms involved in influenza-associated cardiovascular diseases will help to improve treatment plans. This review discusses the direct and indirect effects of influenza virus infection on triggering cardiovascular events. Further, we discussed the similarities and differences in epidemiological and pathogenic mechanisms involved in cardiovascular events associated with coronavirus disease 2019 (COVID-19) compared to influenza infection.

Expression of ectopic trypsin in atherosclerotic plaques and the effects of aprotinin on plaque stability

BACKGROUND

Our previous research revealed that trypsin is abundantly expressed in atherosclerotic plaques and its distribution overlaps with that of matrix metalloproteinase-9 (MMP-9). This study was performed to explore the possible roles of trypsin in vulnerable atherosclerotic plaque formation.

METHODS AND RESULTS

Twenty-four rabbits were randomly assigned to a normal (control) group, an atherosclerosis (experimental) group and a trypsin inhibitor (aprotinin) group. In the 13th feeding week, the aprotinin group was treated with 5 mg/kg/day aprotinin via ear vein for 4 weeks. At the end of the 16th week, coronary arterial and aortic expression of trypsin, proteinase-activated receptor-2 (PAR-2), activated MMP-9, and pro-inflammatory cytokines were significantly greater in the experimental group than in the control group. Aprotinin decreased trypsin expression and activation in plaques, blocked PAR-2 and MMP-9 activation, and decreased cytokine expression; it also increased fibrous cap thickness, decreased the intima-media thickness and intimal/medial ratio, thus significantly ameliorating plaque vulnerability. Upregulated trypsin, MMP-9 and PAR-2 were also found in coronary intimal atherosclerotic plaques of patients undergoing coronary artery bypass grafting.

CONCLUSIONS

Ectopic trypsin was significantly upregulated in atherosclerotic plaques, which increased pro-inflammatory cytokine levels by activating PAR-2 and promoted plaque instability by activating proMMP-9, thereby promoting atherosclerosis and plaque vulnerability. In addition, the high trypsin expression in human coronary intimal atherosclerotic plaques suggests that targeting trypsin may be a new strategy for acute coronary syndrome prevention.

Role of host trypsin-type serine proteases and influenza virus-cytokine-trypsin cycle in influenza viral pathogenesis. Pathogenesis-based therapeutic options

Influenza A virus (IAV) is one of the most common infectious pathogen and associated with significant morbidity and mortality. Although processing the IAV hemagglutinin (HA) envelope glycoprotein precursor is a pre-requisite for viral membrane fusion activity, viral entry and transmission, HA-processing protease is not encoded in the IAV genome and thus the cellular trypsin-type serine HA-processing proteases determine viral infectious tropism and viral pathogenicity. The initial process of IAV infection of the airway is followed by marked upregulation of ectopic trypsin in various organs and endothelial cells through the induction of various proinflammatory cytokines, and this process has been termed the "influenza virus-cytokine-trypsin" cycle. In the advanced stage of IAV infection, the cytokine storm induces disorders of glucose and lipid metabolism and the "metabolic disorders-cytokine" cycle is then linked with the "influenza virus-cytokine-trypsin" cycle, to advance the pathogenic process into energy crisis and multiple organ failure. Application of protease inhibitors and treatment of metabolic disorders that break these cycles and their interconnection is therefore a promising therapeutic approach against influenza. This review discusses IAV pathogenicity on trypsin type serine HA-processing proteases, cytokines, metabolites and therapeutic options.

The Antiviral Potential of Host Protease Inhibitors

The replication of numerous pathogenic viruses depends on host proteases, which therefore emerged as potential antiviral drug targets. In some cases, e.g., for influenza viruses, their function during the viral propagation cycle is relatively well understood, where they cleave and activate viral surface glycoproteins. For other viruses, e.g., Ebola virus, the function of host proteases during replication is still not clear. Host proteases may also contribute to the pathogenicity of virus infection by activating proinflammatory cytokines. For some coronaviruses, human proteases can also serve in a nonproteolytical fashion simply as receptors for virus entry. However, blocking of such protein-protein contacts is challenging, because receptor surfaces are often flat and difficult to address with small molecules. In contrast, many proteases possess well-defined binding pockets. Therefore, they can be considered as well-druggable targets, especially, if they are extracellularly active. The number of their experimental crystal structures is steadily increasing, which is an important prerequisite for a rational structure-based inhibitor design using computational chemistry tools in combination with classical medicinal chemistry approaches. Moreover, host proteases can be considered as stable targets, and their inhibition should prevent rapid resistance developments, which is often observed when addressing viral proteins. Otherwise, the inhibition of host proteases can also affect normal physiological processes leading to a higher probability of side effects and a narrow therapeutic window. Therefore, they should be preferably used in combination therapies with additional antiviral drugs. This strategy should provide a stronger antiviral efficacy, allow to use lower drug doses, and minimize side effects. Despite numerous experimental findings on their antiviral activity, no small-molecule inhibitors of host proteases have been approved for the treatment of virus infections, so far.

Cardiogenic Shock: A Rare Complication of Influenza

We have presented a case of 41-year-old male who presented to the hospital with worsening shortness of breath, fatigue and flu-like symptoms. On admission to hospital, the patient was in severe cardiogenic shock secondary to acute perimyocarditis. He was admitted to the cardiac intensive care unit for close monitoring and aggressive hemodynamic support. Influenza B antigen was detected in nasopharyngeal aspirate and the patient was started on oseltamivir. The patient's cardiac function improved significantly in few days and he was discharged home in stable condition with normal ejection fraction.

Enterokinase Enhances Influenza A Virus Infection by Activating Trypsinogen in Human Cell Lines

Cleavage and activation of hemagglutinin (HA) by trypsin-like proteases in influenza A virus (IAV) are essential prerequisites for its successful infection and spread. In host cells, some transmembrane serine proteases such as TMPRSS2, TMPRSS4 and HAT, along with plasmin in the bloodstream, have been reported to cleave the HA precursor (HA₀) molecule into its active forms, HA₁ and HA₂. Some trypsinogens can also enhance IAV proliferation in some cell types (e.g., rat cardiomyoblasts). However, the precise activation mechanism for this process is unclear, because the expression level of the physiological activator of the trypsinogens, the TMPRSS15 enterokinase, is expected to be very low in such cells, with the exception of duodenal cells. Here, we show that at least two variant enterokinases are expressed in various human cell lines, including A549 lung-derived cells. The exogenous expression of these enterokinases was able to enhance the proliferation of IAV in 293T human kidney cells, but the proliferation was reduced by knocking down the endogenous enterokinase in A549 cells. The enterokinase was able to enhance HA processing in the cells, which activated trypsinogen in vitro and in the IAV-infected cells also. Therefore, we conclude that enterokinase plays a role in IAV infection and proliferation by activating trypsinogen to process viral HA in human cell lines.

Clarithromycin suppresses induction of monocyte chemoattractant protein-1 and matrix metalloproteinase-9 and improves pathological changes in the lungs and heart of mice infected with influenza A virus

The influenza A virus (IAV)-cytokine-trypsin/matrix metalloproteinase-9 (MMP-9) cycle is one of the important mechanisms of multiple organ failure in severe influenza. Clarithromycin, a macrolide antibiotic, has immune modulatory and anti-inflammatory effects. We analyzed the effects of clarithromycin on the induction of chemokines, cytokines, MMP-9, trypsin, vascular hyper-permeability and inflammatory aggravation in mice with IAV infection. IAV/Puerto Rico/8/34(H1N1) infection increased the levels of monocyte chemoattractant protein-1 (MCP-1) and cytokines in serum, and MMP-9 and trypsin in serum and/or the lungs and heart. Clarithromycin significantly suppressed the induction of serum MCP-1 and MMP-9 and vascular hyperpermeability in these organs in the early phase of infection, but did not suppress the induction of trypsin, IL-6 or IFN-γ. Histopathological examination showed that clarithromycin tended to reduce inflammatory cell accumulation in the lungs and heart. These results suggest that clarithromycin suppresses infection-related inflammation and reduces vascular hyperpermeability by suppressing the induction of MCP-1 and MMP-9.

A case of influenza type a myocarditis that presents with ST elevation MI, cardiogenic shock, acute renal failure, and rhabdomyolysis and with rapid recovery after treatment with oseltamivir and intra-aortic balloon pump support

We present a 59-year-old black male with history of type-1 diabetes and alcohol abuse. Patient became critically ill after a 5-day period of burning throat discomfort. On arrival patient was lethargic, in cardiogenic shock with a blood pressure of 81/47mmHg. Immediate diagnoses included diabetic ketoacidosis, acute renal failure, and possible septic shock. He was intubated, resuscitated with intravenous fluids, maintained on three inotropic agents, and given empiric wide spectrum antibiotics. An ECG showed a new ST elevation MI and an echocardiogram showed severe LV dysfunction. Cardiac catheterization showed clean coronaries. With appropriate treatment patient recovered 10days later.

IL-1β is a key cytokine that induces trypsin upregulation in the influenza virus-cytokine-trypsin cycle

Severe influenza is characterized by a cytokine storm, and the influenza virus-cytokine-trypsin cycle is one of the important mechanisms of viral multiplication and multiple organ failure. The aim of this study was to define the key cytokine(s) responsible for trypsin upregulation. Mice were infected with influenza virus strain A/Puerto Rico/8/34 (H1N1) or treated individually or with a combination of interleukin-1β, interleukin-6, and tumor necrosis factor α. The levels of these cytokines and trypsin in the lungs were monitored. The neutralizing effects of anti-IL-1β antibodies on cytokine and trypsin expression in human A549 cells and lung inflammation in the infected mice were examined. Infection induced interleukin-1β, interleukin-6, tumor necrosis factor α, and ectopic trypsin in mouse lungs in a dose- and time-dependent manner. Intraperitoneal administration of interleukin-1β combined with other cytokines tended to upregulate trypsin and cytokine expression in the lungs, but the combination without interleukin-1β did not induce trypsin. In contrast, incubation of A549 cells with interleukin-1β alone induced both cytokines and trypsin, and anti-interleukin-1β antibody treatment abrogated these effects. Administration of the antibody in the infected mice reduced lung inflammation area. These findings suggest that IL-1β plays a key role in trypsin upregulation and has a pathological role in multiple organ failure.

What Is the Arrhythmic Substrate in Viral Myocarditis? Insights from Clinical and Animal Studies

Sudden cardiac death (SCD) remains an unsolved problem in the twenty-first century. It is often due to rapid onset, ventricular arrhythmias caused by a number of different clinical conditions. A proportion of SCD patients have identifiable diseases such as cardiomyopathies, but for others, the causes are unknown. Viral myocarditis is becoming increasingly recognized as a contributor to unexplained mortality, and is thought to be a major cause of SCD in the first two decades of life. Myocardial inflammation, ion channel dysfunction, electrophysiological, and structural remodeling may play important roles in generating life-threatening arrhythmias. The aim of this review article is to examine the electrophysiology of action potential conduction and repolarization and the mechanisms by which their derangements lead to triggered and reentrant arrhythmogenesis. By synthesizing experimental evidence from pre-clinical and clinical studies, a framework of how host (inflammation), and viral (altered cellular signaling) factors can induce ion electrophysiological and structural remodeling is illustrated. Current pharmacological options are mainly supportive, which may be accompanied by mechanical circulatory support. Heart transplantation is the only curative option in the worst case scenario. Future strategies for the management of viral myocarditis are discussed.

MicroRNA Regulation of Human Genes Essential for Influenza A (H7N9) Replication

Influenza A viruses are important pathogens of humans and animals. While seasonal influenza viruses infect humans every year, occasionally animal-origin viruses emerge to cause pandemics with significantly higher morbidity and mortality rates. In March 2013, the public health authorities of China reported three cases of laboratory confirmed human infection with avian influenza A (H7N9) virus, and subsequently there have been many cases reported across South East Asia and recently in North America. Most patients experience severe respiratory illness, and morbidity with mortality rates near 40%. No vaccine is currently available and the use of antivirals is complicated due the frequent emergence of drug resistant strains. Thus, there is an imminent need to identify new drug targets for therapeutic intervention. In the current study, a high-throughput screening (HTS) assay was performed using microRNA (miRNA) inhibitors to identify new host miRNA targets that reduce influenza H7N9 replication in human respiratory (A549) cells. Validation studies lead to a top hit, hsa-miR-664a-3p, that had potent antiviral effects in reducing H7N9 replication (TCID50 titers) by two logs. In silico pathway analysis revealed that this microRNA targeted the LIF and NEK7 genes with effects on pro-inflammatory factors. In follow up studies using siRNAs, anti-viral properties were shown for LIF. Furthermore, inhibition of hsa-miR-664a-3p also reduced virus replication of pandemic influenza A strains H1N1 and H3N2.

Does the Influenza Vaccine Prevent Sequelae Such as Myocarditis from Developing?

Vaccination continues to be a valuable and simple procedure to guard patients from an illness that may prevent them from completing their normal everyday tasks, missing days of work, and even lead to unnecessary sequelae. The following case describes one of the many complications that are seen on a regular basis in any community hospital in different regions of the world. The objective of this publication is to remind the public and practitioner of the urgency to vaccinate each season; thereby, curbing the virus's ability to mutate and preventing unwanted consequences such as bacterial super infection or myocarditis.

Management of fulminant myocarditis: a diagnosis in search of its etiology but with therapeutic options

Fulminant myocarditis is a clinical syndrome with signs of acute heart failure, cardiogenic shock, or life-threating rhythm disturbances in the context of suspected myocarditis. It is not an etiological diagnosis, but may have different underlying causes and pathogenetic processes - viral, bacterial, toxic, and autoreactive. Clinical management of the disease entity at the acute stage involves hemodynamic monitoring in an intensive care unit or similar setting. Rapid routine work-up is mandatory with serial EKGs, echocardiography, cardiac MRI, heart catheterization with endomyocardial biopsy for histology, immunohistology, and molecular analysis for the underlying infection and pathogenesis. Heart failure therapy is warranted in all cases according to current guidelines. For fulminant autoreactive myocarditis, immunosuppressive treatment is beneficial; for viral myocarditis, IVIg can resolve the inflammation, reduce the viral load, and even eradicate the microbial agent. ECMO, IABP, ventricular assist devices, LifeVest, or ICD implantation can bridge to recovery or to heart transplantation.

Influenza virus pathogenicity regulated by host cellular proteases, cytokines and metabolites, and its therapeutic options

Influenza A virus (IAV) causes significant morbidity and mortality. The knowledge gained within the last decade on the pandemic IAV(H1N1)2009 improved our understanding not only of the viral pathogenicity but also the host cellular factors involved in the pathogenicity of multiorgan failure (MOF), such as cellular trypsin-type hemagglutinin (HA0) processing proteases for viral multiplication, cytokine storm, metabolic disorders and energy crisis. The HA processing proteases in the airway and organs for all IAV known to date have been identified. Recently, a new concept on the pathogenicity of MOF, the "influenza virus-cytokine-trypsin" cycle, has been proposed involving up-regulation of trypsin through pro-inflammatory cytokines, and potentiation of viral multiplication in various organs. Furthermore, the relationship between causative factors has been summarized as the "influenza virus-cytokine-trypsin" cycle interconnected with the "metabolic disorders-cytokine" cycle. These cycles provide new treatment concepts for ATP crisis and MOF. This review discusses IAV pathogenicity on cellular proteases, cytokines, metabolites and therapeutic options.

Influenza A virus infection of vascular endothelial cells induces GSK-3β-mediated β-catenin degradation in adherens junctions, with a resultant increase in membrane permeability

Multiorgan failure with vascular hyperpermeability is the final outcome in the progression of seasonal influenza virus pneumonia and influenza-associated encephalopathy, and it is also common in infection with highly pathogenic avian influenza virus. However, the precise molecular mechanism by which influenza virus infection causes vascular endothelial cell hyperpermeability remains poorly defined. We investigated the mechanisms of hyperpermeability of human umbilical vein endothelial cells infected with influenza A virus (IAV)/Puerto Rico/8/34 (PR8) (H1N1). The levels of β-catenin, a key regulatory component of the vascular endothelial-cadherin cell adhesion complex, were markedly decreased during infection for 28 h, with increments of vascular hyperpermeability measured by transendothelial electrical resistance. Lactacystin (at 2 μM), a proteasome inhibitor, inhibited the decrease in β-catenin levels. Since the N-terminal phosphorylation of β-catenin by glycogen synthase kinase (GSK)-3β is the initiation step of proteasome-dependent degradation, we examined the effects of GSK-3β suppression by RNA interference in endothelial cells. IAV-infection-induced β-catenin degradation was significantly inhibited in GSK-3β-knockdown cells, and transfection of cells with recombinant β-catenin significantly suppressed IAV-induced hyperpermeability. These findings suggest that IAV infection induces GSK-3β-mediated β-catenin degradation in the adherens junctional complexes and induces vascular hyperpermeability. The in vitro findings of β-catenin degradation and activation of GSK-3β after IAV infection were confirmed in lungs of mice infected with IAV PR8 during the course of infection from day 0 to day 6. These results suggest that GSK-3β-mediated β-catenin degradation in adherens junctions is one of the key mechanisms of vascular hyperpermeability in severe influenza.

Proinflammatory effects of interferon gamma in mouse adenovirus 1 myocarditis

Adenoviruses are frequent causes of pediatric myocarditis. Little is known about the pathogenesis of adenovirus myocarditis, and the species specificity of human adenoviruses has limited the development of animal models, which is a significant barrier to strategies for prevention or treatment. We have developed a mouse model of myocarditis following mouse adenovirus 1 (MAV-1) infection to study the pathogenic mechanisms of this important cause of pediatric myocarditis. Following intranasal infection of neonatal C57BL/6 mice, we detected viral replication and induction of interferon gamma (IFN-γ) in the hearts of infected mice. MAV-1 caused myocyte necrosis and induced substantial cellular inflammation that was composed predominantly of CD3(+) T lymphocytes. Depletion of IFN-γ during acute infection reduced cardiac inflammation in MAV-1-infected mice without affecting viral replication. We observed decreased contractility during acute infection of neonatal mice, and persistent viral infection in the heart was associated with cardiac remodeling and hypertrophy in adulthood. IFN-γ is a proinflammatory mediator during adenovirus-induced myocarditis, and persistent adenovirus infection may contribute to ongoing cardiac dysfunction.

IMPORTANCE

Studying the pathogenesis of myocarditis caused by different viruses is essential in order to characterize both virus-specific and generalized factors that contribute to disease. Very little is known about the pathogenesis of adenovirus myocarditis, which is a significant impediment to the development of treatment or prevention strategies. We used MAV-1 to establish a mouse model of human adenovirus myocarditis, providing the means to study host and pathogen factors contributing to adenovirus-induced cardiac disease during acute and persistent infection. The MAV-1 model will enable fundamental studies of viral myocarditis, including IFN-γ modulation as a therapeutic strategy.

Ectopic trypsin in the myocardium promotes dilated cardiomyopathy after influenza A virus infection

We have previously reported that ectopic trypsin in the myocardium triggers acute myocarditis after influenza A virus (IAV) infection. As myocarditis is a common precursor to dilated cardiomyopathy (DCM), the aim of the present study was to investigate the influence of trypsin on the progression of DCM after IAV infection. IAV-infected mice treated with saline or trypsin inhibitor were euthanized on days 0, 9, 20, 40 and 60 postinfection. Trypsin expression colocalized with myocardial inflammatory loci and IAV-induced myocarditis peaked on day 9 postinfection and alleviated by day 20 but persisted until day 60 postinfection, even though replication of IAV was not detected from day 20 postinfection. Similar time courses were observed for the activation of pro-matrix metalloproteinase (pro-MMP)-9 and expression of the proinflammatory cytokines IL-6, IL-1β, and TNF-α. Degradation of collagen type I, proliferation of ventricular interstitial collagen, and expression of collagen type I and III mRNA increased significantly during acute and chronic phases; collagen type III mRNA increased more significantly than collagen type I mRNA. Cardiac function progressively deteriorated with progressive left ventricular dilation. The trypsin inhibitor aprotinin suppressed pro-MMP-9 activation and cytokine release, alleviated myocardial inflammation, and restored collagen metabolism during acute and chronic phases of myocarditis. This effectively prevented ventricular dilation and improved cardiac function. These results suggest that ectopic trypsin in the myocardium promoted DCM through chronic activation of pro-MMP-9, persistent induction of cytokines, and mediation of collagen remodeling. Pharmacological inhibition of trypsin activity might be a promising approach for the prevention of viral cardiomyopathy.

Role of protease-activated receptors for the innate immune response of the heart

Protease-activated receptors (PARs) are a family of G-protein-coupled receptors with a unique activation mechanism via cleavage by the serine proteases of the coagulation cascade, immune cell-released proteases, and proteases from pathogens. Pathogens, such as viruses and bacteria, cause myocarditis and heart failure and PAR1 was shown to positively regulate the anti-viral innate immune response via interferon β during virus-induced myocarditis. In contrast, PAR2 negatively regulated the innate immune response and inhibited the interferon β expression. Thus, PARs play a central role for the innate immune response in the heart.

Diisopropylamine dichloroacetate, a novel pyruvate dehydrogenase kinase 4 inhibitor, as a potential therapeutic agent for metabolic disorders and multiorgan failure in severe influenza

Severe influenza is characterized by cytokine storm and multiorgan failure with metabolic energy disorders and vascular hyperpermeability. In the regulation of energy homeostasis, the pyruvate dehydrogenase (PDH) complex plays an important role by catalyzing oxidative decarboxylation of pyruvate, linking glycolysis to the tricarboxylic acid cycle and fatty acid synthesis, and thus its activity is linked to energy homeostasis. The present study tested the effects of diisopropylamine dichloroacetate (DADA), a new PDH kinase 4 (PDK4) inhibitor, in mice with severe influenza. Infection of mice with influenza A PR/8/34(H1N1) virus resulted in marked down-regulation of PDH activity and ATP level, with selective up-regulation of PDK4 in the skeletal muscles, heart, liver and lungs. Oral administration of DADA at 12-h intervals for 14 days starting immediately after infection significantly restored PDH activity and ATP level in various organs, and ameliorated disorders of glucose and lipid metabolism in the blood, together with marked improvement of survival and suppression of cytokine storm, trypsin up-regulation and viral replication. These results indicate that through PDK4 inhibition, DADA effectively suppresses the host metabolic disorder-cytokine cycle, which is closely linked to the influenza virus-cytokine-trypsin cycle, resulting in prevention of multiorgan failure in severe influenza.

Repetitive fulminant influenza myocarditis requiring the use of circulatory assist devices

A 52-year-old man was admitted to our hospital due to shortness of breath that developed one week after the diagnosis of influenza infection. He had a past history of myocarditis associated with influenza B infection 16 years before the current admission. The patient's left ventricular function showed diffuse hypokinesis with a left ventricular ejection fraction of 28%. Due to the progression of heart failure, the infusion of catecholamines and insertion of an intra-aortic balloon pump were required. The patient was discharged uneventfully on the 23rd hospital day. A significant increase in the serum antibody titer against influenza A virus subtype H3N2 led to a diagnosis of recurrent fulminant influenza myocarditis.

Coagulation, protease-activated receptors, and viral myocarditis

The coagulation protease cascade plays an essential role in hemostasis. In addition, a clot contributes to host defense by limiting the spread of pathogens. Coagulation proteases induce intracellular signaling by cleavage of cell surface receptors called protease-activated receptors (PARs). These receptors allow cells to sense changes in the extracellular environment, such as infection. Viruses activate the coagulation cascade by inducing tissue factor expression and by disrupting the endothelium. Virus infection of the heart can cause myocarditis, cardiac remodeling, and heart failure. A recent study using a mouse model have shown that tissue factor, thrombin, and PAR-1 signaling all positively regulate the innate immune during viral myocarditis. In contrast, PAR-2 signaling was found to inhibit interferon-β expression and the innate immune response. These observations suggest that anticoagulants may impair the innate immune response to viral infection and that inhibition of PAR-2 may be a new strategy to reduce viral myocarditis.

Productive infection of human skeletal muscle cells by pandemic and seasonal influenza A(H1N1) viruses

Besides the classical respiratory and systemic symptoms, unusual complications of influenza A infection in humans involve the skeletal muscles. Numerous cases of acute myopathy and/or rhabdomyolysis have been reported, particularly following the outbreak of pandemic influenza A(H1N1) in 2009. The pathogenesis of these influenza-associated myopathies (IAM) remains unkown, although the direct infection of muscle cells is suspected. Here, we studied the susceptibility of cultured human primary muscle cells to a 2009 pandemic and a 2008 seasonal influenza A(H1N1) isolate. Using cells from different donors, we found that differentiated muscle cells (i. e. myotubes) were highly susceptible to infection by both influenza A(H1N1) isolates, whereas undifferentiated cells (i. e. myoblasts) were partially resistant. The receptors for influenza viruses, α2-6 and α2-3 linked sialic acids, were detected on the surface of myotubes and myoblasts. Time line of viral nucleoprotein (NP) expression and nuclear export showed that the first steps of the viral replication cycle could take place in muscle cells. Infected myotubes and myoblasts exhibited budding virions and nuclear inclusions as observed by transmission electron microscopy and correlative light and electron microscopy. Myotubes, but not myoblasts, yielded infectious virus progeny that could further infect naive muscle cells after proteolytic treatment. Infection led to a cytopathic effect with the lysis of muscle cells, as characterized by the release of lactate dehydrogenase. The secretion of proinflammatory cytokines by muscle cells was not affected following infection. Our results are compatible with the hypothesis of a direct muscle infection causing rhabdomyolysis in IAM patients.

Coxsackievirus B3-induced calpain activation facilitates the progeny virus replication via a likely mechanism related with both autophagy enhancement and apoptosis inhibition in the early phase of infection: an in vitro study in H9c2 cells

Calpain is a family of neutral cysteine proteinase involved in many physiological and pathological processes including virus replication, autophagy and apoptosis. Previous study has indicated the involvement of calpain in pathogenesis of coxsackievirus B3 (CVB3)-induced myocarditis. Besides, many studies demonstrated that host cell autophagy and apoptosis mechanisms participate in virus life cycle. However, role of calpain in CVB3 replication via autophagy/apoptosis mechanisms has not been reported, which was discussed here in H9c2 cardiomyocytes. The data demonstrated that calpain was activated following CVB3 infection. Calpain inhibition decreased autophagy, indicating role of calpain in enhancing autophagy during CVB3 infection. Both calpain activity and autophagy were involved in facilitating CVB3 replication demonstrated by virus titer and CVB3 capsid protein VP1 expression alterations resulting from calpain inhibitor ALLN and autophagy inhibitor 3MA intervention. We also found that both calpain activity and autophagy suppressed caspase3 activity and host cell apoptosis 5-10h post-infection (p.i.). In summary, the present study shows that CVB3 infection of H9c2 cells hinders caspase3 activity provocation and cell apoptosis at least in the early phase of infection (5-10h p.i.) via calpain-induced autophagy enhancement, which might be a mechanism facilitating CVB3 replication in host cells.

Protease-activated receptor-2 regulates the innate immune response to viral infection in a coxsackievirus B3-induced myocarditis

OBJECTIVES

This study sought to evaluate the role of protease-activated receptor-2 (PAR2) in coxsackievirus B3 (CVB3)-induced myocarditis.

BACKGROUND

An infection with CVB3 leads to myocarditis. PAR2 modulates the innate immune response. Toll-like receptor-3 (TLR3) is crucial for the innate immune response by inducing the expression of the antiviral cytokine interferon-beta (IFNβ).

METHODS

To induce myocarditis, wild-type (wt) and PAR2 knockout (ko) mice were infected with 10(5) plaque-forming units CVB3. Mice underwent hemodynamic measurements with a 1.2-F microconductance catheter. Wt and PAR2ko hearts and cardiac cells were analyzed for viral replication and immune response with plaque assay, quantitative polymerase chain reaction, Western blot, and immunohistochemistry.

RESULTS

Compared with wt mice, PAR2ko mice and cardiomyocytes exhibited a reduced viral load and developed no myocarditis after infection with CVB3. Hearts and cardiac fibroblasts from PAR2ko mice expressed higher basal levels of IFNβ than wt mice did. Treatment with CVB3 and polyinosinic:polycytidylic acid led to higher IFNβ expression in PAR2ko than in wt fibroblasts and reduced virus replication in PAR2ko fibroblasts was abrogated by neutralizing IFNβ antibody. Overexpression of PAR2 reduced the basal IFNβ expression. Moreover, a direct interaction between PAR2 and Toll-like receptor 3 was observed. PAR2 expression in endomyocardial biopsies of patients with nonischemic cardiomyopathy was positively correlated with myocardial inflammation and negatively with IFNβ expression and left ventricular ejection fraction.

CONCLUSIONS

PAR2 negatively regulates the innate immune response to CVB3 infection and contributes to myocardial dysfunction. The antagonism of PAR2 is of therapeutic interest to strengthen the antiviral response after an infection with a cardiotropic virus.

Excessive cytokine response to rapid proliferation of highly pathogenic avian influenza viruses leads to fatal systemic capillary leakage in chickens

Highly pathogenic avian influenza viruses (HPAIVs) cause lethal infection in chickens. Severe cases of HPAIV infections have been also reported in mammals, including humans. In both mammals and birds, the relationship between host cytokine response to the infection with HPAIVs and lethal outcome has not been well understood. In the present study, the highly pathogenic avian influenza viruses A/turkey/Italy/4580/1999 (H7N1) (Ty/Italy) and A/chicken/Netherlands/2586/2003 (H7N7) (Ck/NL) and the low pathogenic avian influenza virus (LPAIV) A/chicken/Ibaraki/1/2005 (H5N2) (Ck/Ibaraki) were intranasally inoculated into chickens. Ty/Italy replicated more extensively than Ck/NL in systemic tissues of the chickens, especially in the brain, and induced excessive mRNA expression of inflammatory and antiviral cytokines (IFN-γ, IL-1β, IL-6, and IFN-α) in proportion to its proliferation. Using in situ hybridization, IL-6 mRNA was detected mainly in microglial nodules in the brain of the chickens infected with Ty/Italy. Capillary leakage assessed by Evans blue staining was observed in multiple organs, especially in the brains of the chickens infected with Ty/Italy, and was not observed in those infected with Ck/NL. In contrast, LPAIV caused only local infection in the chickens, with neither apparent cytokine expression nor capillary leakage in any tissue of the chickens. The present results indicate that an excessive cytokine response is induced by rapid and extensive proliferation of HPAIV and causes fatal multiple organ failure in chickens.

Blood lactate/ATP ratio, as an alarm index and real-time biomarker in critical illness

Objective

The acute physiology, age and chronic health evaluation (APACHE) II score and other related scores have been used for evaluation of illness severity in the intensive care unit (ICU), but there is still a need for real-time and sensitive prognostic biomarkers. Recently, alarmins from damaged tissues have been reported as alarm-signaling molecules. Although ATP is a member of the alarmins and its depletion in tissues closely correlates with multiple-organ failure, blood ATP level has not been evaluated in critical illness. To identify real-time prognostic biomarker of critical illness, we measured blood ATP levels and the lactate/ATP ratio (ATP-lactate energy risk score, A-LES) in critically ill patients.

Methods and Results

Blood samples were collected from 42 consecutive critically ill ICU patients and 155 healthy subjects. The prognostic values of blood ATP levels and A-LES were compared with APACHE II score. The mean ATP level (SD) in healthy subjects was 0.62 (0.19) mM with no significant age or gender differences. The median ATP level in severely ill patients at ICU admission was significantly low at 0.31 mM (interquartile range 0.25 to 0.44) than the level in moderately ill patient at 0.56 mM (0.38 to 0.70) (P<0.01). Assessment with ATP was further corrected by lactate and expressed as A-LES. The median A-LES was 2.7 (2.1 to 3.3) in patients with satisfactory outcome at discharge but was significantly higher in non-survivors at 38.9 (21.0 to 67.9) (P<0.01). Receiver operating characteristic analysis indicated that measurement of blood ATP and A-LES at ICU admission are as useful as APACHE II score for prediction of mortality.

Conclusion

Blood ATP levels and A-LES are sensitive prognostic biomarkers of mortality at ICU admission. In addition, A-LES provided further real-time evaluation score of illness severity during ICU stay particularly for critically ill patients with APACHE II scores of ≥20.0.

Myocarditis Associated with Influenza A H1N1pdm2009

Acute myocarditis is a well-known complication of influenza infection. The frequency of myocardial involvement in influenza infection varies widely, with the clinical severity ranging from asymptomatic to fulminant varieties. The worst cases can result in death due to impaired cardiac function, although such fulminant myocarditis associated with influenza infection is rare, as shown by previous papers. Following the 2009 influenza pandemic, we reported on the clinical features of a cohort of 15 patients in Japan with H1N1pdm2009 myocarditis. In our subsequent survey of the literature for case reports or series of patients with myocarditis associated with H1N1pdm2009, we identified 58 detailed cases. We discuss here the high prevalence of fulminant myocarditis (36/58, 62%) among patients reported to have myocarditis associated with H1N1pdm2009. Mechanical circulatory support was required in 17 of the patients with fulminant myocarditis, 13 of whom recovered. We stress the need for increased awareness of influenza-associated myocarditis; such knowledge will facilitate earlier diagnosis and treatment of this fatal complication during future influenza pandemics.

A national survey on myocarditis associated with influenza H1N1pdm2009 in the pandemic and postpandemic season in Japan

An influenza pandemic occurred in 2009. We performed a retrospective national questionnaire survey about H1N1pdm2009 myocarditis to compare influenza A H1N1pdm2009 myocarditis in the pandemic (2009/2010) and postpandemic seasons (2010/2011) by collecting data from 360 hospitals. The diagnosis of myocarditis was performed using the guidelines for Diagnosis and Treatment of Myocarditis published by the Japanese Circulation Society (JCS 2009). Twenty-nine patients with influenza A H1N1pdm2009 myocarditis were reported, with 25 from the 2009/2010 season and only 4 patients from the 2010/2011 season. Morbidity and mortality was 28 % (8/29) among all the myocarditis patients. Six patients with myocarditis were complicated by pneumonia. Myocarditis was proved by endomyocardial biopsy or autopsy in 9 patients, although histological findings showed mild myocarditis even in clinically defined fulminant myocarditis cases. Seventeen patients were diagnosed with fulminant H1N1pdm2009 myocarditis with fatal arrhythmias or varying degrees of cardiogenic shock. Fifteen fulminant myocarditis patients were seen in the 2009/2010 season and only 2 in the 2010/2011 season. Ventilators were used in 16 patients. Mechanical circulatory support with intraaortic balloon pumping or percutaneous cardiopulmonary support (IABP/PCPS) was emergently inserted in 13 patients. Of these, 9 patients were rescued with mechanical circulatory support, and 4 patients died. Four fulminant myocarditis patients treated without IABP/PCPS died. We described the clinical features of patients with myocarditis associated with influenza H1N1pdm2009 in the pandemic and postpandemic seasons and demonstrated the high prevalence of fulminant myocarditis (17/29, 59 %). The number of patients with myocarditis associated with influenza A virus seemed to increase in the pandemic season.

Effects of HMG-CoA reductase inhibitor on experimental autoimmune myocarditis

PURPOSE

Myocarditis is an acute inflammatory disease of the heart and is often a precursor of dilated cardiomyopathy. Experimental autoimmune myocarditis (EAM) has been used as a model for human myocarditis. The purpose of this study was to investigate the therapeutic role of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitor, rosuvastatin, on the development of EAM.

METHODS

Experimental autoimmune myocarditis was induced in BALB/c mice by immunization with murine cardiac α-myosin heavy chain (MyHc-α(614-629) [Ac-SLKLMATLFSTYASAD-OH]). High-dose (10 mg/kg/day) or low-dose (1 mg/kg/day) rosuvastatin or vehicle was administered orally by gastric gavage to mice with EAM from day 0 to day 21 after immunization. On day 21 after immunization, echocardiography was carried out and the severity of myocarditis was detected by histopathological evaluation. Levels of serum tumor necrosis factor (TNF)-α and interleukin (IL)-6 were measured by ELISA. Histopathology was performed using haematoxylin and eosin. With apoptosis examined by Tunel, the expression of active caspase-3 in myocardium was investigated by immunohistochemistry.

RESULTS

Rosuvastatin attenuated the histopathological severity of myocarditis. Cardiac function was improved in the two rosuvastatin-treated groups compared to the non-treated EAM group (LVFS: high-dose rosuvastatin group [group H], 0.38 ± 0.10%; low-dose rosuvastatin group [group L], 0.34 ± 0.06%; non-treated EAM group [group N], 0.29 ± 0.07%. LVEF: group H, 0.80 ± 0.09%; group L, 0.71 ± 0.07%; group N, 0.68 ± 0.07%). Furthermore, treatment with rosuvastatin decreased the expression levels of TNF-α (group H, 65.19 ± 7.06 pg/ml; group L, 108.20 ± 5.28 pg/ml; group N, 239.34 ± 11.65 pg/ml) and IL-6 (group H, 14.33 ± 2.15 pg/ml; group L, 19.67 ± 3.04 pg/ml; group N, 40.39 ± 7.17 pg/ml). The rates of expression of active Caspase-3 and myocardial apoptosis were positively correlated with the scores for myocardial pathology.

CONCLUSIONS

These results demonstrate that administration of rosuvastatin can ameliorate EAM progression, inhibit apoptosis of cardiomyocytes, and preserve cardiac output, and they also suggest rosuvastatin may be a promising novel therapeutic strategy for the clinical treatment of myocarditis.

New treatments for influenza

Influenza has a long history of causing morbidity and mortality in the human population through routine seasonal spread and global pandemics. The high mutation rate of the RNA genome of the influenza virus, combined with assortment of its multiple genomic segments, promote antigenic diversity and new subtypes, allowing the virus to evade vaccines and become resistant to antiviral drugs. There is thus a continuing need for new anti-influenza therapy using novel targets and creative strategies. In this review, we summarize prospective future therapeutic regimens based on recent molecular and genomic discoveries.

Oral clarithromycin enhances airway immunoglobulin A (IgA) immunity through induction of IgA class switching recombination and B-cell-activating factor of the tumor necrosis factor family molecule on mucosal dendritic cells in mice infected with influenza A virus

We previously reported that the macrolide antibiotic clarithromycin (CAM) enhanced the mucosal immune response in pediatric influenza, particularly in children treated with the antiviral neuraminidase inhibitor oseltamivir (OSV) with low production of mucosal antiviral secretory IgA (S-IgA). The aims of the present study were to confirm the effects of CAM on S-IgA immune responses, by using influenza A virus (IAV) H1N1-infected mice treated with or without OSV, and to determine the molecular mechanisms responsible for the induction of mucosal IgA class switching recombination in IAV-infected CAM-treated mice. The anti-IAV S-IgA responses and expression levels of IgA class switching recombination-associated molecules were examined in bronchus-lymphoid tissues and spleens of infected mice. We also assessed neutralization activities of S-IgA against IAV. Data show that CAM enhanced anti-IAV S-IgA induction in the airway of infected mice and restored the attenuated antiviral S-IgA levels in OSV-treated mice to the levels in the vehicle-treated mice. The expression levels of B-cell-activating factor of the tumor necrosis factor family (BAFF) molecule on mucosal dendritic cells as well as those of activation-induced cytidine deaminase and Iμ-Cα transcripts on B cells were enhanced by CAM, compared with the levels without CAM treatment, but CAM had no effect on the expression of the BAFF receptor on B cells. Enhancement by CAM of neutralization activities of airway S-IgA against IAV in vitro and reinfected mice was observed. This study identifies that CAM enhances S-IgA production and neutralizing activities through the induction of IgA class switching recombination and upregulation of BAFF molecules in mucosal dendritic cells in IAV-infected mice.

MicroRNA regulation of human protease genes essential for influenza virus replication

Influenza A virus causes seasonal epidemics and periodic pandemics threatening the health of millions of people each year. Vaccination is an effective strategy for reducing morbidity and mortality, and in the absence of drug resistance, the efficacy of chemoprophylaxis is comparable to that of vaccines. However, the rapid emergence of drug resistance has emphasized the need for new drug targets. Knowledge of the host cell components required for influenza replication has been an area targeted for disease intervention. In this study, the human protease genes required for influenza virus replication were determined and validated using RNA interference approaches. The genes validated as critical for influenza virus replication were ADAMTS7, CPE, DPP3, MST1, and PRSS12, and pathway analysis showed these genes were in global host cell pathways governing inflammation (NF-κB), cAMP/calcium signaling (CRE/CREB), and apoptosis. Analyses of host microRNAs predicted to govern expression of these genes showed that eight miRNAs regulated gene expression during virus replication. These findings identify unique host genes and microRNAs important for influenza replication providing potential new targets for disease intervention strategies.

Bezafibrate upregulates carnitine palmitoyltransferase II expression and promotes mitochondrial energy crisis dissipation in fibroblasts of patients with influenza-associated encephalopathy

Influenza-associated encephalopathy (IAE) is characterized by persistently high fever, febrile convulsions, severe brain edema and high mortality. We reported previously that a large proportion of patients with disabling or fatal IAE exhibit a thermolabile phenotype of compound variants for [1055T>G/F352C] and [1102G>A/V368I] of carnitine palmitoyltransferase II (CPT II) and mitochondrial energy crisis during high fever. In the present study, we studied the effect of bezafibrate, a hypolipidemic pan-agonist of peroxisome proliferator-activated receptor (PPAR), on CPT II expression and mitochondrial energy metabolism in fibroblasts of IAE patients and wild type (WT) fibroblasts from a healthy volunteer at 37°C and 41°C. Although heat stress markedly upregulated CPT II, CPT IA and PPAR-δ mRNA expression levels, CPT II activity, β-oxidation and ATP levels in WT and IAE fibroblasts at 41°C were paradoxically downregulated probably due to the thermal instability of the corresponding enzymes. Bezafibrate significantly enhanced the expression levels of the above mRNAs and cellular functions of these enzymes in fibroblasts at 37°C. Bezafibrate-induced increase in CPT II activity also tended to restore the downregulated ATP levels, though moderately, and improved mitochondrial membrane potential even at 41°C to the levels at 37°C in fibroblasts of IAE patients. L-carnitine, a substrate of CPT II, boosted the effects of bezafibrate on cellular ATP levels in WT and IAE fibroblasts, even in severe IAE fibroblasts with thermolabile compound variations of F352C+V368I at 37°C and 41°C. The results suggest the potential usefulness of bezafibrate for the treatment of IAE.