Association study involving polymorphisms in IL-6, IL-1RA, and CTLA4 genes and rheumatic heart disease in New Zealand population of Māori and Pacific ancestry

The microbiome and rheumatic heart disease: current knowledge and future perspectives

Rheumatic heart disease (RHD) is a cardiovascular disease caused by an autoimmune response to group A Streptococcus (GAS) infection resulting in the damage of heart valves. RHD is the most commonly acquired heart disease among children and young adults with a global burden of over 40 million cases accounting for 306,000 deaths annually. Inflammation in the heart valves caused due to molecular mimicry between the GAS antigens and host cardiac proteins is facilitated by cytokines, cross-reactive antibodies and CD4⁺ T cells. The complex interaction between genetic and environmental factors linked with erratic events leads to the loss of immunological tolerance and autoimmunity in RHD. Despite extensive research on the etiopathogenesis of RHD, the precise mechanism underpinning the initiation of acute rheumatic fever (ARF) to the progression of RHD still remains elusive. Mounting evidences support the contribution of the human microbiome in the development of several immune-mediated diseases including rheumatoid arthritis, juvenile idiopathic arthritis, Kawasaki disease, inflammatory bowel disease and type 1 diabetes. The microbiome and their metabolites could play a crucial role in the integrity of the epithelial barrier, development of the immune system, inflammation and differentiation of T cell subsets. Consequently, microbiome dysbiosis might result in autoimmunity by molecular mimicry, epitope spreading and bystander activation. This review discusses various aspects of the interaction between the microbiome and the immune system in order to reveal causative links relating dysbiosis and autoimmune diseases with special emphasis on RHD.

Plausible Role of NLRP3 Inflammasome and Associated Cytokines in Pathogenesis of Rheumatic Heart Disease

Rheumatic heart disease (RHD) is a post-streptococcal sequela caused by Streptococcus pyogenes. The global burden of disease is high among people with low socio-economic status, with significant cases emerging every year despite global eradication efforts. The current treatment includes antibiotic therapies to target strep throat and rheumatic fever and valve replacement strategies as a corrective measure for chronic RHD patients. Valvular damage and valve calcification are considered to be the end-stage processes of the disease resulting from impairment of the endothelial arrangement due to immune infiltration. This immune infiltration is mediated by a cascade of events involving NLRP3 inflammasome activation. NLRP3 inflammasome is activated by wide range of stimuli including bacterial cell wall components like M proteins and leukocidal toxins like nicotinamide dehydrogenase (NADase) and streptolysin O (SLO) and these play a major role in sustaining the virulence of Streptococcus pyogenes and progression of RHD. In this review, we are discussing NLRP3 inflammasome and its plausible role in the pathogenesis of RHD by exploiting the host-pathogen interaction mainly focusing on the NLRP3 inflammasome-mediated cytokines IL-1β and IL-18. Different therapeutic approaches involving NLRP3 inflammasome inactivation, caspase-1 inhibition, and blockade of IL-1β and IL-18 are discussed in this review and may be promising for treating RHD patients.

Cytokine imbalance in acute rheumatic fever and rheumatic heart disease: Mechanisms and therapeutic implications

Acute Rheumatic Fever (ARF) and Rheumatic Heart Disease (RHD) are autoimmune sequelae of Group A Streptococcus infection with significant global disease burden. The pathogenesis of these diseases is poorly understood, and no immune modulating therapies are available to stop progression from ARF to RHD. Cytokines and chemokines are immune signaling molecules critical to the development of autoimmune diseases. An increasing number of studies point to a central role for pro-inflammatory cytokines and chemokines in ARF and RHD pathogenesis, in particular IL-6, IL-8/CXCL8, and TNFα, which are elevated in circulation in both ARF and RHD patients. Histological studies of RHD valve tissue implicates Th1 and Th17 associated pro-inflammatory cytokines, chemokine CXCL9, and the fibrosis-associated cytokine TGF-β in progressive cycles of inflammatory damage and fibrotic repair. Taken together, this suggests immune molecules contribute to both the acute inflammatory disease stage of ARF, as well as cardiac remodeling and valve dysfunction in RHD. Monoclonal antibody blockade of pro-inflammatory cytokines IL-6 and TNFα are approved therapies for many autoimmune diseases and the most successful immunomodulating therapies for rheumatoid arthritis. Current evidence suggests possible benefit for ARF patients from IL-6 and TNFα blockade, in particular to interrupt progression to RHD, and warrants immediate investigation.

Rheumatic Heart Valve Disease Pathophysiology and Underlying Mechanisms

Rheumatic heart valve disease (RHVD) is a post-infectious sequel of acute rheumatic fever resulting from an abnormal immune response to a streptococcal pharyngitis that triggers valvular damage. RHVD is the leading cause of cardiovascular death in children and young adults, mainly in women from low and middle-income countries. It is known that long-term inflammation and high degree of fibrosis leads to valve dysfunction due to anatomic disruption of the valve apparatus. However, since public and private investments in RHVD studies are practically inexistent the number of publications is scarce. This disease shows different natural history and clinical presentations as compared to other degenerative heart valve diseases. Although more than five decades passed after the pioneering studies on the pathogenesis of RHVD, it is still unclear how self-tolerance mechanisms fail in this disease, and how humoral and cellular inflammatory responses are interconnected. Despite that pathological mechanisms have been already proposed for RHVD, none of them are able to explain the preferential involvement of the mitral valve. This review focuses on pathophysiology and underlying mechanisms of RHVD.

Non-pharmacological Strategies Against Systemic Inflammation: Molecular Basis and Clinical Evidence

Systemic inflammation is a common denominator to a variety of cardiovascular (CV) and non-CV diseases and relative risk factors, including hypertension and its control, metabolic diseases, rheumatic disorders, and those affecting the gastrointestinal tract. Besides medications, a non-pharmacological approach encompassing lifestyle changes and other complementary measures is mentioned in several updated guidelines on the management of these conditions. We performed an updated narrative review on the mechanisms behind the systemic impact of inflammation and the role of non-pharmacological, complementary measures centered on lowering systemic phlogosis for preserving or restoring a good global health. The central role of genetics in shaping the immune response is discussed in conjunction with that of the microbiome, highlighting the interdependence and mutual influences between the human genome and microbial integrity, diversity, and functions. Several plausible strategies to modulate inflammation and restore balanced crosstalk between the human genome and the microbiome are then recapitulated, including dietary measures, active lifestyle, and other potential approaches to manipulate the resident microbial community. To date, evidence from high-quality human studies is sparse to allow the unconditioned inclusion of understudied, though plausible solutions against inflammation into public health strategies for global wellness. This gap claims further focused, well-designed research targeted at unravelling the mechanisms behind future personalized medicine.

Rheumatic heart disease: A review of the current status of global research activity

Rheumatic heart disease (RHD) is a serious and long-term consequence of acute rheumatic fever (ARF), an autoimmune sequela of a mucosal infection by Streptococcus pyogenes (Group A Streptococcus, Strep A). The pathogenesis of ARF and RHD is complex and not fully understood but involves host and bacterial factors, molecular mimicry, and aberrant host innate and adaptive immune responses that result in loss of self-tolerance and subsequent cross-reactivity with host tissues. RHD is entirely preventable yet claims an estimated 320 000 lives annually. The major burden of disease is carried by developing nations and Indigenous populations within developed nations, including Australia. This review will focus on the epidemiology, pathogenesis and treatment of ARF and RHD in Australia, where: streptococcal pyoderma, rather than streptococcal pharyngitis, and Group C and Group G Streptococcus, have been implicated as antecedents to ARF; the rates of RHD in remote Indigenous communities are persistently among the highest in the world; government register-based programs coordinate disease screening and delivery of prophylaxis with variable success; and researchers are making significant progress in the development of a broad-spectrum vaccine against Strep A.

Genetic variants in rheumatic fever and rheumatic heart disease

Genetic association studies in rheumatic heart disease (RHD) have the potential to contribute toward our understanding of the pathogenetic mechanism, and may shed light on controversies about RHD etiology. Furthermore, genetic association studies may uncover biomarkers that can be used to identify susceptible individuals, and contribute toward developing vaccine and novel therapeutic targets. Genetic predisposition to rheumatic fever and RHD has been hypothesized by findings from familial studies and observed associations between genes located in the human leukocyte antigens on chromosome 6p21.3 and elsewhere in the genome. We sought to summarize, from published Genetic association studies in RHD, evidence on genetic variants implicated in RHD susceptibility. Using HuGENet™ systematic review methods, we evaluated 66 studies reporting on 42 genes. Existing meta-analyses of candidate gene studies suggest that TGF-β1 [rs1800469], and IL-1β [rs2853550] single nucleotide polymorphisms (SNPs) contribute to susceptibility to RHD, whereas the TNF-α [rs1800629 and rs361525], TGF-β1 [rs1800470 and rs4803457], IL-6 [rs1800795], IL-10 [rs1800896] were not associated with RHD. However, candidate gene studies in RF/RHD are relatively small, thus lacking statistical power to identify reliable and reproducible findings, emphasizing the need for large-scale multicenter studies with different populations.

Risk Factors for Acute Rheumatic Fever: Literature Review and Protocol for a Case-Control Study in New Zealand

Acute rheumatic fever (ARF) and its sequela, rheumatic heart disease (RHD), have largely disappeared from high-income countries. However, in New Zealand (NZ), rates remain unacceptably high in indigenous Māori and Pacific populations. The goal of this study is to identify potentially modifiable risk factors for ARF to support effective disease prevention policies and programmes. A case-control design is used. Cases are those meeting the standard NZ case-definition for ARF, recruited within four weeks of hospitalisation for a first episode of ARF, aged less than 20 years, and residing in the North Island of NZ. This study aims to recruit at least 120 cases and 360 controls matched by age, ethnicity, gender, deprivation, district, and time period. For data collection, a comprehensive pre-tested questionnaire focussed on exposures during the four weeks prior to illness or interview will be used. Linked data include previous hospitalisations, dental records, and school characteristics. Specimen collection includes a throat swab (Group A Streptococcus), a nasal swab (Staphylococcus aureus), blood (vitamin D, ferritin, DNA for genetic testing, immune-profiling), and head hair (nicotine). A major strength of this study is its comprehensive focus covering organism, host and environmental factors. Having closely matched controls enables the examination of a wide range of specific environmental risk factors.

Health Challenges of the Pacific Region: Insights From History, Geography, Social Determinants, Genetics, and the Microbiome

The Pacific region, also referred to as Oceania, is a geographically widespread region populated by people of diverse cultures and ethnicities. Indigenous people in the region (Melanesians, Polynesians, Micronesians, Papuans, and Indigenous Australians) are over-represented on national, regional, and global scales for the burden of infectious and non-communicable diseases. Although social and environmental factors such as poverty, education, and access to health-care are assumed to be major drivers of this disease burden, there is also developing evidence that genetic and microbiotic factors should also be considered. To date, studies investigating genetic and/or microbiotic links with vulnerabilities to infectious and non-communicable diseases have mostly focused on populations in Europe, Asia, and USA, with uncertain associations for other populations such as indigenous communities in Oceania. Recent developments in personalized medicine have shown that identifying ethnicity-linked genetic vulnerabilities can be important for medical management. Although our understanding of the impacts of the gut microbiome on health is still in the early stages, it is likely that equivalent vulnerabilities will also be identified through the interaction between gut microbiome composition and function with pathogens and the host immune system. As rapid economic, dietary, and cultural changes occur throughout Oceania it becomes increasingly important that further research is conducted within indigenous populations to address the double burden of high rates of infectious diseases and rapidly rising non-communicable diseases so that comprehensive development goals can be planned. In this article, we review the current knowledge on the impact of nutrition, genetics, and the gut microbiome on infectious diseases in indigenous people of the Pacific region.

T cell subsets: an integral component in pathogenesis of rheumatic heart disease

Acute rheumatic fever (ARF) is a consequence of pharyngeal infection of group A streptococcal (GAS) infection. Carditis is the most common manifestation of ARF which occurs in 30-45% of the susceptible individuals. Overlooked ARF cases might further progress towards rheumatic heart disease (RHD) in susceptible individuals, which ultimately leads to permanent heart valve damage. Molecular mimicry between streptococcal antigens and human proteins is the most widely accepted theory to describe the pathogenesis of RHD. In the recent past, various subsets of T cells have been reported to play an imperative role in the pathogenesis of RHD. Alterations in various T cell subsets, viz. Th1, Th2, Th17, and Treg cells, and their signature cytokines influence the immune responses and are associated with pathogenesis of RHD. Association of other T cell subsets (Th3, Th9, Th22, and T_FH) is not defined in context of RHD. Several investigations have confirmed the up-regulation of adhesion molecules and thus infiltration of T cells into the heart tissues. T cells secrete both Th type 1 and type 2 cytokines and these auto-reactive T cells play a key role in progression of heart valve damage. In this review, we are going to discuss about the role of T cell subsets and their corresponding cytokines in the pathogenesis of RHD.

Heart failure in cancer: role of checkpoint inhibitors

The introduction of immune checkpoint inhibitors have greatly improved clinical outcomes in several cancer types, revolutionizing the management of a wide variety of tumors endowed with poor prognosis. Despite its success, high grade immune related adverse events were observed in patients treated with checkpoint inhibitors. While cardiotoxicity was largely underestimated in initial studies, numerous reports of fulminant myocarditis and fatal heart failure (HF) have been recently described. In this review we discuss possible mechanisms involved in cardiac toxicity triggered by inhibition of cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed cell death 1 (PD-1) pathway, the most prominent checkpoint inhibitors available in the clinic. Major cardiovascular events associated with checkpoint inhibitors adds another layer of complexity in cancer therapy and urges for an interdisciplinary approach between oncologists, cardiologists, and immunologist.

Cardio-metabolic disease genetic risk factors among Māori and Pacific Island people in Aotearoa New Zealand: current state of knowledge and future directions

CONTEXT

Cardio-metabolic conditions in Aotearoa New Zealand (NZ) Māori and non-indigenous Polynesian (Pacific) populations have been increasing in prevalence and severity, especially over the last two decades.

OBJECTIVES

To assess knowledge on genetic and non-genetic risk factors for cardio-metabolic disease in the Māori and Pacific populations residing in Aotearoa NZ by a semi-systematic review of the PubMed database. To outline possible future directions in genetic epidemiological research with Māori and Pacific communities.

RESULTS

There have been few studies to confirm that risk factors in other populations also associate with cardio-metabolic conditions in Māori and Pacific populations. Such data are important when interventions are considered. Genetic studies have been sporadic, with no genome-wide association studies done.

CONCLUSIONS

Biomedical research with Māori and Pacific communities is important to reduce the prevalence and impact of the cardio-metabolic diseases, as precision medicine is implemented in other Aotearoa NZ populations using overseas findings. Genuine engagement with Māori and Pacific communities is needed to ensure positive outcomes for genetic studies, from data collection through to analysis and dissemination. Important is building trust, understanding by researchers of fundamental cultural concepts and implementing protocols that minimise risks and maximise benefits. Approaches that utilise information such as genealogical information and whole genome sequencing technologies will provide new insights into cardio-metabolic conditions-and new interventions for affected individuals and families.

Susceptibility to chronic inflammation: an update

Chronic inflammation is defined by the persistence of inflammatory processes beyond their physiological function, resulting in tissue destruction. Chronic inflammation is implicated in the progression of many chronic diseases and plays a central role in chronic inflammatory and autoimmune disease. As such, this review aims to collate some of the latest research in relation to genetic and environmental susceptibilities to chronic inflammation. In the genetic section, we discuss some of the updates in cytokine research and current treatments that are being developed. We also discuss newly identified canonical and non-canonical genes associated with chronic inflammation. In the environmental section, we highlight some of the latest updates and evidence in relation to the role that infection, diet and stress play in promoting inflammation. The aim of this review is to provide an overview of the latest research to build on our current understanding of chronic inflammation. It highlights the complexity associated with chronic inflammation, as well as provides insights into potential new targets for therapies that could be used to treat chronic inflammation and consequently prevent disease progression.