A Toolbox of Potential Immune-Related Therapies for Inflammatory Cardiomyopathy

Myocarditis is a multifactorial disorder, characterized by an inflammatory reaction in the myocardium, predominantly triggered by infectious agents, but also by antigen mimicry or autoimmunity in susceptible individuals. Unless spontaneously resolved, a chronic inflammatory course concludes with cardiac muscle dysfunction portrayed by ventricular dilatation, clinically termed inflammatory cardiomyopathy (Infl-CM). Treatment strategies aim to resolve chronic inflammation and preserve cardiac function. Beside standard heart failure treatments, which only play a supportive role in this condition, systemic immunosuppressants are used to diminish inflammatory cell function at the cost of noxious side effects. To date, the treatment protocols are expert-based without large clinical evidence. This review describes concept and contemporary strategies to alleviate myocardial inflammation and sheds light on potential inflammatory targets in an evidence-based order

The Quest for Antiinflammatory and Immunomodulatory Strategies in Heart Failure

Intensive research over the last 3 decades has unequivocally demonstrated the relevance of inflammation in heart failure (HF). Despite our current and ever increasing knowledge about inflammation, the clinical success of antiinflammatory and immunomodulatory therapies in HF is still limited. This review outlines the complexity and diversity of inflammation, its reciprocal interaction with HF, and addresses future perspectives, calling for immunomodulatory therapies that are specific for factors that activate the immune system without the risk of nonspecific immune suppression

Novel therapeutic strategies for inflammatory cardiomyopathy: from bench to bedside

Die entzündliche Kardiomyopathie ist eine heterogene Erkrankung. Die häufigste Ursache ist eine Virusinfektion, wobei Parvovirus B19 (B19V) der bedeutendste Erreger ist. In dieser Arbeit wurden potenzielle Therapie für die speziellen klinischen Verläufe und deren Phänotypen untersucht. In vitro konnte gezeigt werden, dass Telbivudin in B19V-infizierten/B19V-non-structural protein-1-stimulierten humanen mikrovaskulären Endothelzellen (HMEC-1) endothelial-protektiv wirkt. In einem klinischen Versuch wurden dann 4 Patienten, bei denen eine aktive Transkription des B19V nachgewiesen wurde, für 6 Monate mit Telbivudin behandelt. Alle Patienten verbesserten sich. Ein anderes klinisches Szenario stellt die schwere Entzündung des Myokards dar, welche gewöhnlich mit einer inaktiven/persistierenden Infektion des B19V verbunden ist. Eine Behandlung mit Immunsuppressiva ist hier umstritten, da eine Reaktivierung des Virus befürchtet wird. Um diesen Aspekt weiter zu untersuchen, würde eine Therapie mit Prednisolon in Kombination mit Azathioprin bei 51 B19V-positiven und 17 B19V-negativen Patienten angewandt. Beide Gruppen profitierten in ähnlichem Maße von der Kombinationstherapie, wobei sich die Virusmenge nicht signifikant veränderte. Bei B19V-negativen Patienten konnte über die Persistenz von CD20+ B-Lymphozyten in den EMBs die Untergruppe der „Steroide non-responder“ klassifiziert werden. Im weiteren Verlauf wurden 6 Patienten mit Rituximab, einem monoklonalen Antikörper, der spezifisch gegen CD20+ B-Lymphozyten gerichtet ist, behandelt. Hiervon zeigten 5 Patienten eine ausgezeichnete klinische Verbesserung. Ein Patient mit Myokarditis-induzierten kardiogenen Schock zeigt, dass die Entlastung des linken Ventrikels mittels eines Mikroaxialpumpensystems zu einer rapiden Abnahme der Entzündungszellen führt. Zusammenfassend liefert diese Arbeit Belege für die Wirksamkeit und die Notwendigkeit einer phänotypbasierten Behandlung bei der entzündlichen Kardiomyopathie.Inflammatory cardiomyopathy is a heterogenous disease. Viral etiologies are the most common, with parvovirus B19 (B19V) being the most prominent culprit. Currently, no specific treatment for inflammatory cardiomyopathy exists. In this study, tailored treatment strategies were investigated as potential therapies for specific clinical scenarios. The antiviral drug telbivudine was investigated in the setting of EMB-proven B19V-associated inflammatory cardiomyopathy. In cell culture, telbivudine exhibited endothelial-protective effects on B19V-infected/B19V-non-structural protein-1-stimulated human microvascular endothelial cells (HMEC-1). Clinically, four B19V-positive patients improved following six-month telbivudine regimen in a single-patient use approach. The results were translated to the “PreTOPIC” clinical study, for further evaluation in a randomized placebo-controlled setting. In a different clinical scenario, severe myocardial inflammation is usually associated with inactive/persistent B19V. Here, the use of immunosuppression is controversial, fearing viral flare-up. We investigated combined prednisolone/azathioprine therapy in 51 B19V-positive and 17 B19V negative patients in a single-center observational study. Both groups gained similar benefit, while viral loads did not significantly vary. Among virus-negative phenotypes, EMB-proven CD20+ B lymphocyte persistence characterized a subgroup of steroid non-responders. In this cohort, six patients were treated with rituximab, a monoclonal antibody selectively targeting CD20+ B lymphocytes. Five patients showed outstanding clinical improvement parallel to CD20+ B lymphocyte depletion. Lastly, in a single case of myocarditis-induced cardiogenic shock, mechanical left ventricular unloading via axial flow pump proved to exert disease-modifying effects. In conclusion, this thesis provides evidence for the efficacy and need for phenotype-based inflammatory cardiomyopathy treatment

Neutrophil and endothelial cell-mediated inflammation in abdominal sepsis

Sepsis is defined as a life-threatening condition caused by a dysregulated host response to infection. Neutrophils are themost abundant innate immune cells of the body and play a key role in septic pathogenesis. During sepsis activatedneutrophils release web-like traps decorated with various cellular proteins known as neutrophil extracellular traps(NET). The primary task of NET and NET-associated proteins are to kill pathogens; however, excessive accumulationof NET is known to cause tissue damage. Endothelial cells are important for regulating vascular permeability andbarrier functions; however, during sepsis endothelial cells get activated and contribute to tissue damage andorgan failure. The four original studies included in this thesis aimed to investigate new mechanisms involved information of NET, lung injury and pulmonary endothelial cell activation in abdominal sepsis. In study I, we havefound that c-Abl kinase regulate NET formation through ROS signaling pathway. Blocking of c-Abl kinase notonly inhibited NET formation but also reduced inflammation and tissue damage in sepsis. In study II, weinvestigated the role of actin-related protein 2/3 complex (Arp2/3 complex) and found that it regulates neutrophiltrap expulsion both in vivo and in vitro. Inhibition of Arp2/3 complex not only reduced the neutrophil infiltration inbronchoalveolar space, but also alleviated lung damage in abdominal sepsis. In study III, we investigated the roleof S100A9, a pro-inflammatory alarmin, in regulating inflammation and tissue damage in abdominal sepsis.Inhibition of S100A9 by a specific inhibitor, ABR-238901, decreased sepsis-induced neutrophil activation,cytokine formation as well as damage to the lung tissue. In study IV, we examined global transcriptomic changesin a subgroup of lung endothelial cells during sepsis. We found that sepsis caused transcriptomic changes ofgenes related to regulation of coagulation, vascular permeability as well as wound healing and lipid metabolic incapillary endothelial cells. In contrast, postcapillary venules were found to be more enriched with genes related tochemotaxis, cell-cell adhesion of integrins, chemokine biosynthesis, regulation of actin polymerization andneutrophil homeostasis after sepsis. Together, these results demonstrated that targeting c-Abl, Arp2/3 complex,S100A9 or endothelial functions could be useful targets to ameliorate neutrophil mediated tissue injury in sepsis

The Protective and Pathologic Roles of Toll-like Receptors in Arthritogenic Alphavirus Infection

Arthritogenic alphaviruses, including Chikungunya virus and Ross River virus (RRV), are mosquito-borne pathogens responsible for epidemics of debilitating polyarthritis in humans. The host inflammatory response plays an important role in the pathogenesis of arthritic alphaviruses, where some pathways, such as the complement cascade, exacerbate virus-induced disease, while type I IFN and other immune signaling pathways mediate protection from disease. Using a mouse model of alphavirus-induced arthritis/myositis, we demonstrated that toll-like receptor (TLR) signaling contributes to protection from and enhancement of alphavirus-induced disease. Myd88-dependent TLR7 signaling was critical for protection from severe RRV-induced morbidity and mortality. Additionally, TLR7 deficiency resulted in the production of low affinity, non-neutralizing RRV-specific antibodies that exacerbated virus-induced disease through systemic antibody- and complement-mediated mechanisms. Furthermore, TLR4 promoted RRV-induced morbidity and tissue damage in a complement-dependent manner, and complement-associated macrophage activation was dependent on TLR4 expression during RRV infection. Taken together, these studies establish the integral role that TLR pathways play in arthritic alphavirus pathogenesis and suggest that designing therapeutic strategies that target TLR signaling may aid in the treatment of RRV infection.Doctor of Philosoph

A crucial role for IL-21 in controlling CD4 T cell responses to respiratory viral infection

Respiratory syncytial virus (RSV) is a pneumovirus that infects almost all children by the age of three, and causes an intense pulmonary infiltrate termed bronchiolitis. The tissue damage caused by this immune response significantly reduces lung function such that hospitalisation and mechanical ventilation may be required. There is no licensed vaccine against RSV, partly because the exact immunological mechanism responsible for bronchiolitis remains unclear, though CD4 and CD8 T cells are known to be essential. Interleukin-21 (IL-21) is a recently identified member of the γc chain cytokine family, important in autoimmunity, cancer, and chronic viral infections. Produced mainly by CD4 T cells, IL-21 affects the responses of several cell types but is particularly important for enhancing activation and survival of CD8 T cells. As such, it was hypothesised that IL-21 could be targeted therapeutically to reduce anti-RSV CD8 T cell responses and reduce the incidence of bronchiolitis. This hypothesis was tested in three models of RSV disease. Here, it is shown that IL-21 is critical for control of CD4 T cell responses rather than CD8. IL-21 depletion increases T cell responses, including cell recruitment and cytokine production, thereby increasing disease. Conversely, it reduced regulatory T cell influx and antibody production. In contrast, IL-21 over-expression ablates the anti-viral T cell response and RSV disease without affecting regulatory T cells. Also, early chemokine production by infected epithelial cells is inhibited and that DC migration is affected, possibly reducing T cell activation and influx. Antibody 4 production is also reduced, and consequently lymphocyte memory development is blocked resulting in no protection against viral rechallenge. Therefore, IL-21 plays a crucial role in the development of anti-viral pulmonary immunity and should be considered as part of a therapy to alleviate primary RSV disease in conjunction with other factors to boost anti-viral memory.Open Acces

Investigate the regulatory effect of human IL-37 isoform a (IL-37a) on Toll-like receptor (TLR) response in vitro and in vivo

Background: Interleukin-37 is a newly discovered member of the IL-1 superfamily, consisting of 5 isoforms (IL-37a-e) due to different RNA splicing. Current studies are only focused on IL-37b isoform and demonstrate that IL-37b is an important immunosuppressive cytokine in TLR response in inflammatory diseases. However, the function and importance of other isoforms is still unknown. Here we investigate the function of IL-37 isoform a (IL-37a) which has a unique nuclear localisation sequence (NLS) and elastase cleavage sites in the protein N-terminal, while also containing the same receptor binding domain as IL-37b in the C-terminal. Hypothesis: As IL-37a carries the same receptor-binding domain as IL-37b, the two isoforms may share the same receptor and signalling via similar pathway in the regulation of TLR function. However, the unique N-terminal domains may confer IL-37a additional function in nuclear translocation and gene regulation. Aims: 1. To produce IL-37a and IL-37b recombinant proteins and transgenic mice. (Chapter 3). 2. To investigate the regulatory effect of IL-37a on TLR response in vitro and in a disease model (Chapter 4). 3. To explore the underlying molecular mechanism by which IL-37a and IL-37b differently affect TLR4 response in immune cells using transcriptomic analysis (Chapter 5)