Genetic determinants of coxsackievirus B3 pathogenesis

Toll-Like Receptors: Are They Taking a Toll on the Heart in Viral Myocarditis?

Myocarditis is an inflammatory disease of the heart with viral infections being the most common aetiology. Its complex biology remains poorly understood and its clinical management is one of the most challenging in the field of cardiology. Toll-like receptors (TLRs), a family of evolutionarily conserved pattern recognition receptors, are increasingly known to be implicated in the pathophysiology of viral myocarditis. Their central role in innate and adaptive immune responses, and in the inflammatory reaction that ensues, indeed makes them prime candidates to profoundly affect every stage of the disease process. This review describes the pathogenesis and pathophysiology of viral myocarditis, and scrutinises the role of TLRs in every phase. We conclude with directions for future research in this field.

CCR5del32 genotype in human enteroviral cardiomyopathy leads to spontaneous virus clearance and improved outcome compared to wildtype CCR5

Background

Enteroviral cardiomyopathy is a life-threatening disease, and detection of enterovirus (EV) RNA in the initial endomyocardial biopsy is associated with adverse prognosis and increased mortality. Some patients with EV infection may spontaneously eliminate the virus and recover, whereas those with virus persistence deteriorate and progress to heart failure. Interferon-beta (IFN-β) therapy eliminates the virus, resulting in increased survival of treated patients. CCR5 is expressed on antigen-presenting cells (both macrophages and dendritic cells) and immune effector cells (T-lymphocytes with memory/effector phenotype and natural killer cells). Its 32-bp deletion (CCR5del32) is the most frequent human coding sequence mutation. This study addresses the correlation of CCR5 polymorphism to the clinical course of EV infection and the necessity for IFN-β treatment.

Methods

We examined 97 consecutive patients with chronic/inflammatory cardiomyopathy and biopsy-proven EV infection and reliable information on clinical outcomes by CCr5 genotyping. These data were evaluated in relation to virus persistence in follow-up biopsies and survival rates over a 15-year period.

Results

Genotyping revealed a strong correlation between the CCR5del32 genotype and spontaneous virus clearance with improved outcomes. All patients with CCR5del32 eliminated EV spontaneously and none of them died within the observed period. In the group of untreated CCR5 wildtype patients, 33% died (Kaplan–Meier log-rank p = 0.010). However, CCR5 wildtype individuals treated with IFN-β are more likely to survive than without therapy (Kaplan–Meier log-rank p = 0.004) in identical proportions to individuals with the CCR5del32 genotype.

Conclusions

These data suggest that CCR5 genotyping is a novel predictive genetic marker for the clinical course of human EV cardiomyopathies. Hereby clinicians can identify those EV positive individuals who will eliminate the virus spontaneously based on CCR5 phenotype and those patients with CCR5 wildtype genotype who would be eligible for immediate antiviral IFN-β treatment to minimize irreversible cardiac damage.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1610-8) contains supplementary material, which is available to authorized users.

Hsp70-1: upregulation via selective phosphorylation of heat shock factor 1 during coxsackieviral infection and promotion of viral replication via the AU-rich element

Coxsackievirus B3 (CVB3) is the primary pathogen of viral myocarditis. Upon infection, CVB3 exploits the host cellular machineries, such as chaperone proteins, to benefit its own infection cycles. Inducible heat shock 70-kDa proteins (Hsp70s) are chaperone proteins induced by various cellular stress conditions. The internal ribosomal entry site (IRES) within Hsp70 mRNA allows Hsp70 to be translated cap-independently during CVB3 infection when global cap-dependent translation is compromised. The Hsp70 protein family contains two major members, Hsp70-1 and Hsp70-2. This study showed that Hsp70-1, but not Hsp70-2, was upregulated during CVB3 infection both in vitro and in vivo. Then a novel mechanism of Hsp70-1 induction was revealed in which CaMKIIγ is activated by CVB3 replication and leads to phosphorylation of heat shock factor 1 (HSF1) specifically at Serine 230, which enhances Hsp70-1 transcription. Meanwhile, phosphorylation of Ser230 induces translocation of HSF1 from the cytoplasm to nucleus, thus blocking the ERK1/2-mediated phosphorylation of HSF1 at Ser307, a negative regulatory process of Hsp70 transcription, further contributing to Hsp70-1 upregulation. Finally, we demonstrated that Hsp70-1 upregulation, in turn, stabilizes CVB3 genome via the AU-rich element (ARE) harbored in the 3' untranslated region of CVB3 genomic RNA.

Coxsackievirus B3 replication and pathogenesis

ABSTRACT 

Viruses such as coxsackievirus B3 (CVB3) are entirely host cell-dependent parasites. Indeed, they must cleverly exploit various compartments of host cells to complete their life cycle, and consequently launch disease. Evolution has equipped this pico-rna-virus, CVB3, to use different strategies, including CVB3-induced direct damage to host cells followed by a host inflammatory response to CVB3 infection, and cell death to super-additively promote target organ tissue injury, and dysfunction. In this update, the patho-stratagems of CVB3 are explored from molecular, and systems-level approaches. In summarizing recent developments in this field, we focus particularly on mechanisms by which CVB3 can harness different host cell processes including kinases, host cell-killing and cell-eating machineries, matrix metalloproteinases and miRNAs to promote disease.

Galectin-9 administration ameliorates CVB3 induced myocarditis by promoting the proliferation of regulatory T cells and alternatively activated Th2 cells

In this study we explored the effects of galectin-9 on CVB3 induced myocarditis and its possible mechanisms involved. We demonstrated that galectin-9 expression was significantly up-regulated in the myocardium following CVB3 infection and was correlated with the severity of viral myocarditis. To explore whether galectin-9 may have therapeutic effect on the CVB3 induced myocarditis, galectin-9 was administered daily to mice following CVB3 infection. Significantly reduced CD4(+) T cells and remarkably increased regulatory T cells frequency in the heart tissue were found as compared to the non-treated mice. It was accompanied by a significant decreased level of Th1 cytokines as TNF-α and IFN-γ both in the myocardium and serum, and an increased level of Th2 cytokines such as IL-4 and IL-10. Galectin-9 was further found to promote the proliferation of regulatory T cells and elevated IL-4-secreting Th2 cells. It may represent as a novel therapeutic strategy in treating Th1-mediated inflammatory cardiac disease.

Functional alterations of cardiac proteasomes under physiological and pathological conditions

The cardiac proteasome is a complex, heterogeneous, and dynamic organelle. Its function is regulated by its molecular organization, post-translational modifications, and associated partner proteins. Pressure overload, ischaemic heart disease, or genetic mutations in contractile proteins can cause heart failure, during which misfolded protein levels are elevated. At the same time, numerous interconnected signal transduction pathways are activated that may modulate any of the three proteasomal regulatory mechanisms mentioned above, resulting in functional changes in cardiac proteasomes. Many lines of evidence support the important role of the ubiquitin-proteasome system (UPS) in the development of heart diseases. Many researchers have focused on the UPS, applying new drug discovery methods not only in the field of cancer research but also in cardiovascular fields such as cardiac hypertrophy and ischaemic heart diseases. More understanding of UPS in the pathophysiology of heart diseases will lead to new routes for therapy.

CXCL10 inhibits viral replication through recruitment of natural killer cells in coxsackievirus B3-induced myocarditis

Coxsackievirus (CV)B3 is the primary cause of viral myocarditis. We previously observed CXC chemokine ligand 10 (CXCL10) upregulation in the myocardium early in infection. However, the impact of CXCL10 in CVB3-induced myocarditis is unknown. Using isolated primary mouse cardiomyocytes we demonstrated for the first time that cardiomyocytes can express CXCL10 on interferon-gamma stimulation. To explore the role of CXCL10 in CVB3-induced myocarditis, both CXCL10 transgenic and knockout mice were used. Following CVB3 challenges, the viral titer in the hearts inversely correlated with the levels of CXCL10 at early phase of infection before visible immune infiltration. Furthermore, as compared with the control mice, the decreased virus titers in the CXCL10 transgenic mouse hearts led to less cardiac damage and better cardiac function and vice verse in the knockout mice. This antiviral ability of CXCL10 might be through recruitment of natural killer (NK) cells to the heart and increased interferon-gamma expression early in infection. At day 7 postinfection, with massive influx of mononuclear cells the expression of CXCL10 enhanced the infiltration of CXCR3(+) cells, CD4(+), and CD8(+) T cells, as well as the expression of associated inflammatory cytokines. However, the augmented accumulation of these immune cells and associated cytokines failed to alter the viral clearance and mice survival. These results suggest the protective role of CXCL10 during the early course of CVB3 infection, which is attributed to the recruitment of NK cells. Nonetheless, CXCL10-directed chemoattractant effect is not sufficient for host to clear the virus in the heart.

Proteasome inhibition attenuates coxsackievirus-induced myocardial damage in mice

Coxsackievirus B3 (CVB3) is one of the most prevalent pathogens of viral myocarditis, which may persist chronically and progress to dilated cardiomyopathy. We previously demonstrated a critical role of the ubiquitin-proteasome system (UPS) in the regulation of coxsackievirus replication in mouse cardiomyocytes. In the present study, we extend our interest to an in vivo animal model to examine the regulation and role of the UPS in CVB3-induced murine myocarditis. Male myocarditis-susceptible A/J mice at age 4-5 wk were randomized to four groups: sham infection + vehicle (n = 10), sham infection + proteasome inhibitor (n = 10), virus + vehicle (n = 20), and virus + proteasome inhibitor (n = 20). Proteasome inhibitor was administered subcutaneously once a day for 3 days. Mice were killed on day 9 after infection, and infected hearts were harvested for Western blot analysis, plaque assay, immunostaining, and histological examination. We showed that CVB3 infection led to an accumulation of ubiquitin conjugates at 9 days after infection. Protein levels of ubiquitin-activating enzyme E1A/E1B, ubiquitin-conjugating enzyme UBCH7, as well as deubiquitinating enzyme UCHL1 were markedly increased in CVB3-infected mice compared with sham infection. However, there was no significant alteration in proteasome activities at 9 days after infection. Immunohistochemical staining revealed that increased expression of E1A/E1B was mainly localized to virus-damaged cells. Finally, we showed that application of a proteasome inhibitor significantly reduced CVB3-induced myocardial damage. This observation reveals a novel mechanism of coxsackieviral pathogenesis, and suggests that the UPS may be an attractive therapeutic target against coxsackievirus-induced myocarditis.

Drug discovery using the regulation of gene expression

The expression of a disease-relevant protein is controlled by a transcriptional program specifically regulated at all stages of normal development and during the adult life. Thus, regulation of gene expression as an approach to drug discovery is conceptually appealing because it provides a rational basis for molecular strategies aimed at modulating gene expression in given cell types and/or at a given time. Indeed, numerous pharmacologic agents have been identified that can either restore or suppress disease-relevant protein expression. In this review, the author critically examines new strategies and methodologies that are being used and developed to identify and validate new therapeutic targets by taking advantage of our knowledge on mechanisms regulating their expression at the transcriptional and post-transcriptional levels. The author also examines the impact of genome-wide approaches and methods aimed at controlling epigenetic mechanisms of gene regulation and concludes by extrapolating on future trends.

A perspective on microarrays: current applications, pitfalls, and potential uses

With advances in robotics, computational capabilities, and the fabrication of high quality glass slides coinciding with increased genomic information being available on public databases, microarray technology is increasingly being used in laboratories around the world. In fact, fields as varied as: toxicology, evolutionary biology, drug development and production, disease characterization, diagnostics development, cellular physiology and stress responses, and forensics have benefiting from its use. However, for many researchers not familiar with microarrays, current articles and reviews often address neither the fundamental principles behind the technology nor the proper designing of experiments. Although, microarray technology is relatively simple, conceptually, its practice does require careful planning and detailed understanding of the limitations inherently present. Without these considerations, it can be exceedingly difficult to ascertain valuable information from microarray data. Therefore, this text aims to outline key features in microarray technology, paying particular attention to current applications as outlined in recent publications, experimental design, statistical methods, and potential uses. Furthermore, this review is not meant to be comprehensive, but rather substantive; highlighting important concepts and detailing steps necessary to conduct and interpret microarray experiments. Collectively, the information included in this text will highlight the versatility of microarray technology and provide a glimpse of what the future may hold.

Stress-activated protein kinases are involved in coxsackievirus B3 viral progeny release

Stress-activated protein kinases (SAPKs), consisting of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), are activated upon various environmental stimuli, including viral infections. Cellular survival and death signaling events following coxsackievirus B3 (CVB3) infection have been studied in relationship to viral replication, but the role of SAPKs has not been scrutinized. In this study, we found that the phosphorylation of JNK1/2 and p38 MAPK was increased during active replication of CVB3 and that their phosphorylation was independent of CVB3-induced caspase activation or production of reactive oxygen species. The roles of these kinases in CVB3 infection were further evaluated using specific inhibitors: SP600125 for JNK1/2 and SB203580 for p38 MAPK. JNK1/2 inhibitors reduced CVB3-induced phosphorylation of activating transcription factor 2, and the p38 MAPK inhibitor reduced CVB3-induced phosphorylation of heat shock protein 27. Although inhibition of these kinases by specific inhibitors did not affect CVB3 viral protein synthesis, inhibition of p38 MAPK but not of JNK1/2 resulted in significant reduction of viral progeny release, suppression of CVB3-induced cell death, and blockage of CVB3-induced caspase-3 activation in infected cells. We conclude that SAPK pathways play critical roles in the life cycle of CVB3, particularly in viral progeny release.

Pyrrolidine dithiocarbamate reduces coxsackievirus B3 replication through inhibition of the ubiquitin-proteasome pathway

Coxsackievirus B3 (CVB3) is one of the most common pathogens for viral myocarditis. The lack of effective therapeutics for CVB3-caused viral diseases underscores the importance of searching for antiviral compounds. Pyrrolidine dithiocarbamate (PDTC) is an antioxidant and is recently reported to inhibit ubiquitin-proteasome-mediated proteolysis. Previous studies have shown that PDTC inhibits replication of rhinovirus, influenza virus, and poliovirus. In the present study, we report that PDTC is a potent inhibitor of CVB3. Coxsackievirus-infected HeLa cells treated with PDTC showed a significant reduction of CVB3 viral RNA synthesis, viral protein VP1 expression, and viral progeny release. Similar to previous observation that divalent ions mediate the function of PDTC, we further report that serum-containing copper and zinc are required for its antiviral activity. CVB3 infection resulted in massive generation of reactive oxygen species (ROS). Although PDTC alleviated ROS generation, the antiviral activity was unlikely dependent on its antioxidant effect because the potent antioxidant, N-acetyl-L-cysteine, failed to inhibit CVB3 replication. Consistent with previous reports that PDTC inhibits ubiquitin-proteasome-mediated protein degradation, we found that PDTC treatment led to the accumulation of several short-lived proteins in infected cells. We further provide evidence that the inhibitory effect of PDTC on protein degradation was not due to inhibition of proteasome activity but likely modulation of ubiquitination. Together with our previous findings that proteasome inhibition reduces CVB3 replication (H. Luo, J. Zhang, C. Cheung, A. Suarez, B. M. McManus, and D. Yang, Am. J. Pathol. 163:381-385, 2003), results in this study suggest a strong antiviral effect of PDTC on coxsackievirus, likely through inhibition of the ubiquitin-proteasome pathway.