Revisiting the pathogenesis of rheumatic fever and carditis

Multiscale structure and function of the aortic valve apparatus

Whereas studying the aortic valve in isolation has facilitated the development of life-saving procedures and technologies, the dynamic interplay of the aortic valve and its surrounding structures is vital to preserving their function across the wide range of conditions encountered in an active lifestyle. Our view is that these structures should be viewed as an integrated functional unit, here referred to as the aortic valve apparatus (AVA). The coupling of the aortic valve and root, left ventricular outflow tract, and blood circulation is crucial for AVA's functions: unidirectional flow out of the left ventricle, coronary perfusion, reservoir function, and support of left ventricular function. In this review, we explore the multiscale biological and physical phenomena that underlie the simultaneous fulfillment of these functions. A brief overview of the tools used to investigate the AVA, such as medical imaging modalities, experimental methods, and computational modeling, specifically fluid-structure interaction (FSI) simulations, is included. Some pathologies affecting the AVA are explored, and insights are provided on treatments and interventions that aim to maintain quality of life. The concepts explained in this article support the idea of AVA being an integrated functional unit and help identify unanswered research questions. Incorporating phenomena through the molecular, micro, meso, and whole tissue scales is crucial for understanding the sophisticated normal functions and diseases of the AVA.

Methods for Establishing a Rat Model of Rheumatic Heart Disease

Rheumatic heart disease (RHD) is responsible for nearly 250,000 deaths annually and poses a significant health threat in developing areas. The unclear pathogenesis of RHD makes the development of cost-effective treatments challenging, particularly as current surgical options are expensive and technologically demanding, exacerbating the economic and quality-of-life burdens for patients. Given the risks associated with direct human experimentation due to the uncertain pathogenesis, using a rat model infected with Group A Streptococcus (GAS) has become a crucial experimental strategy for RHD research. The development of an RHD rat model, refined over 23 years, now stands as a pivotal approach in studies aiming to understand the disease's pathogenesis. This review summarizes the evolution, characteristics, advantages, and limitations of the RHD rat model, offering insights into potential areas for improvement. It aims to provide researchers with a comprehensive understanding of the model, supporting the advancement of research methodologies and the discovery of innovative treatments for RHD.

An acute rheumatic fever immune signature comprising inflammatory markers, IgG3, and Streptococcus pyogenes-specific antibodies

Understanding the immune profile of acute rheumatic fever (ARF), a serious post-infectious sequelae of Streptococcal pyogenes (group A Streptococcus [GAS]), could inform disease pathogenesis and management. Circulating cytokines, immunoglobulins, and complement were analyzed in participants with first-episode ARF, swab-positive GAS pharyngitis and matched healthy controls. A striking elevation of total IgG3 was observed in ARF (90% > clinical reference range for normal). ARF was also associated with an inflammatory triad with significant correlations between interleukin-6, C-reactive protein, and complement C4 absent in controls. Quantification of GAS-specific antibody responses revealed that subclass polarization was remarkably consistent across the disease spectrum; conserved protein antigens polarized to IgG1, while M-protein responses polarized to IgG3 in all groups. However, the magnitude of responses was significantly higher in ARF. Taken together, these findings emphasize the association of exaggerated GAS antibody responses, IgG3, and inflammatory cytokines in ARF and suggest IgG3 testing could beneficially augment clinical diagnosis.

Development of Autoimmune Diseases Among Children With Pediatric Acute-Onset Neuropsychiatric Syndrome

Importance

Epidemiologic studies indicate a high rate of autoimmune conditions among patients with obsessive-complusive disorder and other psychiatric conditions. Furthering the understanding of the inflammatory diatheses of psychiatric conditions may open doors to new treatment paradigms for psychiatric disorders.

Objectives

To evaluate whether pediatric acute-onset neuropsychiatric syndrome (PANS) is associated with an inflammatory diathesis by assessing signs of immune activation and vasculopathy during a psychiatric symptom exacerbation (flare), estimating the risk of developing arthritis and other autoimmune diseases, and characterizing subtypes of arthritis.

Design, Setting, and Participants

This retrospective cohort study used longitudinal clinical data on 193 consecutive patients with PANS followed up within the Stanford Immune Behavioral Health Clinic from September 1, 2012, to December 31, 2021.

Main Outcomes and Measures

Medical records were reviewed, and a predefined set of immune markers that were measured during a flare and the features and imaging findings of arthritis and other autoimmune diseases were collected. Immune activation markers included (1) autoimmunity signs (antinuclear antibody, antihistone antibody, antithyroglobulin antibody, C1q binding assay, and complement levels [C3 and C4]); (2) immune dysregulation or inflammation signs (leukopenia, thrombocytosis, C-reactive protein, and erythrocyte sedimentation rate); and (3) vasculopathy signs (livedo reticularis, periungual redness and swelling, abnormally prominent onychodermal band, palatal petechiae, high von Willebrand factor antigen, and high d-dimer). Last, the cumulative risk of developing arthritis and autoimmune diseases was estimated using product limit (Kaplan-Meier) survival probability.

Results

The study included data from 193 children (112 boys [58.0%]) who had PANS at a mean (SD) age of 7.5 (3.5) years. They were followed up for a mean (SD) of 4.0 (2.1) years. Among those tested for immune activation markers, 54.2% (97 of 179) had nonspecific markers of autoimmunity, 12.0% (22 of 184) had nonspecific signs of immune dysregulation or inflammation, and 35.8% (69 of 193) had signs of vasculopathy. By 14 years of age, the estimated cumulative incidence of arthritis was 28.3% (95% CI, 20.8%-36.3%), and the estimated cumulative incidence of another autoimmune disease was 7.5% (95% CI, 4.0%-12.4%). Novel findings in the subgroup with arthritis include joint capsule thickening (55.0% [22 of 40]), distal interphalangeal joint tenderness (81.8% [45 of 55]), and spinous process tenderness (80.0% [44 of 55]). Among the 55 patients with arthritis, the most common subtypes of arthritis included enthesitis-related arthritis (37 [67.3%]), spondyloarthritis (27 [49.1%]), and psoriatic arthritis (10 [18.2%]).

Conclusions and Relevance

This study found that patients with PANS show signs of immune activation and vasculopathy during psychiatric symptom flares and have an increased risk of developing arthritis and other autoimmune diseases compared with the general pediatric population. The most common arthritis subtype was enthesitis-related arthritis. These findings suggest that PANS may be part of a multisystem inflammatory condition rather than an isolated psychiatric or neuroinflammatory disorder.

Application of Transthoracic Echocardiography for Cardiac Safety Evaluation in the Clinical Development Process of Vaccines Against Streptococcus pyogenes

Superficial infections with Streptococcus pyogenes (Strep A), pharyngitis and impetigo can induce acute rheumatic fever, an autoimmune sequela manifesting mostly with arthritis and rheumatic carditis. Valvular heart damage can persist or advance following repeated episodes of acute rheumatic fever, causing rheumatic heart disease. Acute rheumatic fever and rheumatic heart disease disproportionately affect children and young adults in developing countries and disadvantaged communities in developed countries. People living with rheumatic heart disease are at risk of experiencing potentially fatal complications such as heart failure, bacterial endocarditis or stroke. Transthoracic echocardiography plays a central role in diagnosing both rheumatic carditis and rheumatic heart disease. Despite the obvious medical need, no licensed Strep A vaccines are currently available, as their clinical development process faces several challenges, including concerns for cardiac safety. However, the development of Strep A vaccines has been recently relaunched by many vaccine developers. In this context, a reliable and consistent safety evaluation of Strep A vaccine candidates, including the use of transthoracic echocardiography for detecting cardiac adverse events, could greatly contribute to developing a safe and efficacious product in the near future. Here, we propose a framework for the consistent use of transthoracic echocardiography to proactively detect cardiac safety events in clinical trials of Strep A vaccine candidates.

Fatal Myocarditis following COVID-19 mRNA Immunization: A Case Report and Differential Diagnosis Review

Carditis in childhood is a rare disease with several etiologies. We report a case of infant death due to pericarditis and myocarditis after the mRNA vaccine against COVID-19 (COVIDmRNAV). A 7-year-old male child received the first dose of the COVIDmRNAV and presented with monoarthritis and a fever non-responsive to oral antibiotics. The laboratory investigation showed signs of infection (leukocytosis, high levels of c-reactive protein). His condition rapidly deteriorated, and the patient died. The autopsy identified pericardial fibrin deposits, hemorrhagic areas in the myocardium, and normal valves. A diffuse intermyocardial inflammatory infiltrate composed of T CD8+ lymphocytes and histiocytes was identified. An antistreptolysin O (ASO) dosage showed high titers. The presence of arthritis, elevated ASO, and carditis fulfills the criteria for rheumatic fever. However, valve disease and Aschoff's nodules, present in 90% of rheumatic carditis cases, were absent in this case. The temporal correlation with mRNA vaccination prompted its inclusion as one of the etiologies. In cases of myocardial damage related to COVID-19mRNAV, it appears to be related to the expression of exosomes and lipid nanoparticles, leading to a cytokine storm. The potential effects of the COVID-19mRNAV must be considered in the pathogenesis of this disease, whether as an etiology or a contributing factor to a previously initiated myocardial injury.

Exploring the presence of oral bacteria in non-oral sites of patients with cardiovascular diseases using whole metagenomic data

Cardiovascular diseases (CVDs) encompass various conditions affecting the heart and its blood vessels and are often linked with oral microbes. Our data analysis aimed to identify oral bacteria from other non-oral sites (i.e., gut, arterial plaque and cultured blood) that could be linked with CVDs. Taxonomic profiling identified bacteria to the species level and compared with the Human Oral Microbiome Database (HOMD). The oral bacteria in the gut, cultured blood and arterial plaque samples were catalogued, with their average frequency calculated for each sample. Additionally, data were filtered by comparison with the Human Microbiome Project (HMP) database. We identified 17,243 microbial species, of which 410 were present in the HOMD database and further denominated as "oral", and were found in at least one gut sample, but only 221 and 169 species were identified in the cultured blood and plaque samples, respectively. Of the 410 species, 153 were present solely in oral-associated environments after comparison with the HMP database, irrespective of their presence in other body sites. Our results suggest a potential connection between the presence of specific species of oral bacterial and occurrence of CVDs. Detecting these oral bacterial species in non-oral sites of patients with CVDs could help uncover the link between oral health and general health, including cardiovascular conditions via bacterial translocation.

The Immunomodulatory Role of Microbiota in Rheumatic Heart Disease: What Do We Know and What Can We Learn from Other Rheumatic Diseases?

Rheumatic heart disease (RHD) represents a serious cardiac sequela of acute rheumatic fever, occurring in 30-45% of patients. RHD is multifactorial, with a strong familial predisposition and known environmental risk factors that drive loss of immunological tolerance. The gut and oral microbiome have recently been implicated in the pathogenesis of RHD. Disruption of the delicate balance of the microbiome, or dysbiosis, is thought to lead to autoimmune responses through several different mechanisms including molecular mimicry, epitope spreading, and bystander activation. However, data on the microbiomes of RHD patients are scarce. Therefore, in this comprehensive review, we explore the various dimensions of the intricate relationship between the microbiome and the immune system in RHD and other rheumatic diseases to explore the potential effect of microbiota on RHD and opportunities for diagnosis and treatment.

SARS-CoV-2 and Its Bacterial Co- or Super-Infections Synergize to Trigger COVID-19 Autoimmune Cardiopathies

Autoimmune cardiopathies (AC) following COVID-19 and vaccination against SARS-CoV-2 occur at significant rates but are of unknown etiology. This study investigated the possible roles of viral and bacterial mimicry, as well as viral-bacterial co-infections, as possible inducers of COVID-19 AC using proteomic methods and enzyme-linked immunoadsorption assays. BLAST and LALIGN results of this study demonstrate that SARS-CoV-2 shares a significantly greater number of high quality similarities to some cardiac protein compared with other viruses; that bacteria such as Streptococci, Staphylococci and Enterococci also display very significant similarities to cardiac proteins but to a different set than SARS-CoV-2; that the importance of these similarities is largely validated by ELISA experiments demonstrating that polyclonal antibodies against SARS-CoV-2 and COVID-19-associated bacteria recognize cardiac proteins with high affinity; that to account for the range of cardiac proteins targeted by autoantibodies in COVID-19-associated autoimmune myocarditis, both viral and bacterial triggers are probably required; that the targets of the viral and bacterial antibodies are often molecularly complementary antigens such as actin and myosin, laminin and collagen, or creatine kinase and pyruvate kinase, that are known to bind to each other; and that the corresponding viral and bacterial antibodies recognizing these complementary antigens also bind to each other with high affinity as if they have an idiotype-anti-idiotype relationship. These results suggest that AC results from SARS-CoV-2 infections or vaccination complicated by bacterial infections. Vaccination against some of these bacterial infections, such as Streptococci and Haemophilus, may therefore decrease AC risk, as may the appropriate and timely use of antibiotics among COVID-19 patients and careful screening of vaccinees for signs of infection such as fever, diarrhea, infected wounds, gum disease, etc.

The Use of Artificial Intelligence Guidance for Rheumatic Heart Disease Screening by Novices

INTRODUCTION

A novel technology utilizing artificial intelligence (AI) to provide real-time image-acquisition guidance, enabling novices to obtain diagnostic echocardiographic images, holds promise to expand the reach of echo screening for rheumatic heart disease (RHD). We evaluated the ability of nonexperts to obtain diagnostic-quality images in patients with RHD using AI guidance with color Doppler.

METHODS

Novice providers without prior ultrasound experience underwent a 1-day training curriculum to complete a 7-view screening protocol using AI guidance in Kampala, Uganda. All trainees then scanned 8 to 10 volunteer patients using AI guidance, half RHD and half normal. The same patients were scanned by 2 expert sonographers without the use of AI guidance. Images were evaluated by expert blinded cardiologists to assess (1) diagnostic quality to determine presence/absence of RHD and (2) valvular function and (3) to assign an American College of Emergency Physicians score of 1 to 5 for each view.

RESULTS

Thirty-six novice participants scanned a total of 50 patients, resulting in a total of 462 echocardiogram studies, 362 obtained by nonexperts using AI guidance and 100 obtained by expert sonographers without AI guidance. Novice images enabled diagnostic interpretation in >90% of studies for presence/absence of RHD, abnormal MV morphology, and mitral regurgitation (vs 99% by experts, P ≤ .001). Images were less diagnostic for aortic valve disease (79% for aortic regurgitation, 50% for aortic stenosis, vs 99% and 91% by experts, P < .001). The American College of Emergency Physicians scores of nonexpert images were highest in the parasternal long-axis images (mean, 3.45; 81% ≥ 3) compared with lower scores for apical 4-chamber (mean, 3.20; 74% ≥ 3) and apical 5-chamber images (mean, 2.43; 38% ≥ 3).

CONCLUSIONS

Artificial intelligence guidance with color Doppler is feasible to enable RHD screening by nonexperts, performing significantly better for assessment of the mitral than aortic valve. Further refinement is needed to optimize acquisition of color Doppler apical views.

Altered gut microbiome profile in patients with knee osteoarthritis

Introduction

Osteoarthritis (OA) is a kind of chronic, degenerative disorder with unknown causes. In this study, we aimed to improve our understanding of the gut microbiota profile in patients with knee OA.

Methods

16S rDNA gene sequencing was performed to detect the gut microbiota in fecal samples collected from the patients with OA (n = 32) and normal control (NC, n = 57). Then the metagenomic sequencing was used to identify the genes or functions linked with gut microbial changes at the species level in the fecal samples from patients with OA and NC groups.

Results

The Proteobacteria was identified as dominant bacteria in OA group. We identified 81 genera resulted significantly different in abundance between OA and NC. The abundance of Agathobacter, Ruminococcus, Roseburia, Subdoligranulum, and Lactobacillus showed significant decrease in the OA compared to the NC. The abundance of genera Prevotella_7, Clostridium, Flavonifractor and Klebsiella were increasing in the OA group, and the families Lactobacillaceae, Christensenellaceae, Clostridiaceae_1 and Acidaminococcaceae were increasing in the NC. The metagenomic sequencing showed that the abundance of Bacteroides stercoris, Bacteroides vulgatus and Bacteroides uniformis at the species level were significantly decreasing in the OA, and the abundance of Escherichia coli, Klebsiella pneumoniae, Shigella flexneri and Streptococcus salivarius were significantly increased in OA.

Discussion

The results of our study interpret a comprehensive profile of the gut microbiota in patients with knee OA and offer the evidence that the cartilage-gut-microbiome axis could play a crucial role in underlying the mechanisms and pathogenesis of OA.

Case report: Autopericardial aortic valve replacement and mitral homograft implantation in a patient with ankylosing spondylitis

INTRODUCTION AND IMPORTANCE

Bekhterev's disease, or ankylosing spondylitis (AS), is a chronic inflammatory rheumatic disease closely related to the human leukocyte antigen (HLA)-B27. Cardiac damage in AS occurs in 2-10 % of patients more commonly as aortic insufficiency, aortitis, mitral valve fibrosis, or cardiac conduction abnormalities.

CASE PRESENTATION

In this article we present a clinical case of a 52-year-old female patient with Bekhterev's disease, who underwent aortic valve reconstruction with autopericardium and mitral homograft implantation in mitral position.

CLINICAL DISCUSSION

The use of homografts and reconstructive surgeries using autologous materials allow not only avoiding lifelong intake of anticoagulants, but also maintaining hemodynamic profile comparable to that of native valves.

CONCLUSION

This clinical case shows that treatment of patients with rheumatic diseases is a complex treatment problem that requires a personalized approach.

IgG2 rules: N-acetyl-β-D-glucosamine-specific IgG2 and Th17/Th1 cooperation may promote the pathogenesis of acute rheumatic heart disease and be a biomarker of the autoimmune sequelae of Streptococcus pyogenes

Antecedent group A streptococcal pharyngitis is a well-established cause of acute rheumatic fever (ARF) where rheumatic valvular heart disease (RHD) and Sydenham chorea (SC) are major manifestations. In ARF, crossreactive antibodies and T cells respond to streptococcal antigens, group A carbohydrate, N-acetyl-β-D-glucosamine (GlcNAc), and M protein, respectively, and through molecular mimicry target heart and brain tissues. In this translational human study, we further address our hypothesis regarding specific pathogenic humoral and cellular immune mechanisms leading to streptococcal sequelae in a small pilot study. The aims of the study were to (1) better understand specific mechanisms of pathogenesis in ARF, (2) identify a potential early biomarker of ARF, (3) determine immunoglobulin G (IgG) subclasses directed against GlcNAc, the immunodominant epitope of the group A carbohydrate, by reaction of ARF serum IgG with GlcNAc, M protein, and human neuronal cells (SK-N-SH), and (4) determine IgG subclasses deposited on heart tissues from RHD. In 10 pediatric patients with RHD and 6 pediatric patients with SC, the serum IgG2 subclass reacted significantly with GlcNAc, and distinguished ARF from 7 pediatric patients with uncomplicated pharyngitis. Three pediatric patients who demonstrated only polymigrating arthritis, a major manifestation of ARF and part of the Jones criteria for diagnosis, lacked the elevated IgG2 subclass GlcNAc-specific reactivity. In SC, the GlcNAc-specific IgG2 subclass in cerebrospinal fluid (CSF) selectively targeted human neuronal cells as well as GlcNAc in the ELISA. In rheumatic carditis, the IgG2 subclass preferentially and strongly deposited in valve tissues (n = 4) despite elevated concentrations of IgG1 and IgG3 in RHD sera as detected by ELISA to group A streptococcal M protein. Although our human study of ARF includes a very small limited sample set, our novel research findings suggest a strong IgG2 autoantibody response against GlcNAc in RHD and SC, which targeted heart valves and neuronal cells. Cardiac IgG2 deposition was identified with an associated IL-17A/IFN-γ cooperative signature in RHD tissue which displayed both IgG2 deposition and cellular infiltrates demonstrating these cytokines simultaneously. GlcNAc-specific IgG2 may be an important autoantibody in initial stages of the pathogenesis of group A streptococcal sequelae, and future studies will determine if it can serve as a biomarker for risk of RHD and SC or early diagnosis of ARF.

T Cell Receptor Sequences Amplified during Severe COVID-19 and Multisystem Inflammatory Syndrome in Children Mimic SARS-CoV-2, Its Bacterial Co-Infections and Host Autoantigens

Published hypervariable region V-beta T cell receptor (TCR) sequences were collected from people with severe COVID-19 characterized by having various autoimmune complications, including blood coagulopathies and cardiac autoimmunity, as well as from patients diagnosed with the Kawasaki disease (KD)-like multisystem inflammatory syndrome in children (MIS-C). These were compared with comparable published v-beta TCR sequences from people diagnosed with KD and from healthy individuals. Since TCR V-beta sequences are supposed to be complementary to antigens that induce clonal expansion, it was surprising that only a quarter of the TCR sequences derived from severe COVID-19 and MIS-C patients mimicked SARS-CoV-2 proteins. Thirty percent of the KD-derived TCR mimicked coronaviruses other than SARS-CoV-2. In contrast, only three percent of the TCR sequences from healthy individuals and those diagnosed with autoimmune myocarditis displayed similarities to any coronavirus. In each disease, significant increases were found in the amount of TCRs from healthy individuals mimicking specific bacterial co-infections (especially Enterococcus faecium, Staphylococcal and Streptococcal antigens) and host autoantigens targeted by autoimmune diseases (especially myosin, collagen, phospholipid-associated proteins, and blood coagulation proteins). Theoretical explanations for these surprising observations and implications to unravel the causes of autoimmune diseases are explored.

The oral microbiome in the pathophysiology of cardiovascular disease

Despite advances in our understanding of the pathophysiology of many cardiovascular diseases (CVDs) and expansion of available therapies, the global burden of CVD-associated morbidity and mortality remains unacceptably high. Important gaps remain in our understanding of the mechanisms of CVD and determinants of disease progression. In the past decade, much research has been conducted on the human microbiome and its potential role in modulating CVD. With the advent of high-throughput technologies and multiomics analyses, the complex and dynamic relationship between the microbiota, their 'theatre of activity' and the host is gradually being elucidated. The relationship between the gut microbiome and CVD is well established. Much less is known about the role of disruption (dysbiosis) of the oral microbiome; however, interest in the field is growing, as is the body of literature from basic science and animal and human investigations. In this Review, we examine the link between the oral microbiome and CVD, specifically coronary artery disease, stroke, peripheral artery disease, heart failure, infective endocarditis and rheumatic heart disease. We discuss the various mechanisms by which oral dysbiosis contributes to CVD pathogenesis and potential strategies for prevention and treatment.

Rheumatic Heart Disease: JACC Focus Seminar 2/4

It is a sad reality that although eminently preventable, and despite possessing such knowledge for >70 years, rheumatic heart disease (RHD) remains the most common cause of cardiovascular morbidity and early mortality in young people worldwide. A disease of the poor, RHD is one of the most neglected diseases. Several challenges are unique to the acute rheumatic fever/RHD continuum and contribute to its persistence, including its sequestration among the poorest, its protracted natural history, the erratic availability of penicillin, and the lack of a concerted effort in endemic regions. However, there is cause for optimism following a resurgence in scientific interest over the last 15 years. This review presents the latest advancements in epidemiology, diagnosis, and management. It also discusses pressing research questions on disease pathophysiology, the barriers to implementation of effective management strategies, and pragmatic policy solutions required for translation of current knowledge into meaningful action.

New insight into the role of lipid metabolism-related proteins in rheumatic heart valve disease

PURPOSE

The aim of this study was to determine the expression of lipid metabolism-related proteins in rheumatic heart valve disease (RHVD).

METHODS

This retrospective study involved a total of 20 cases of moderate or severe rheumatic mitral valve stenosis and 4 cases of mitral regurgitation due to secondary causes from September 2018 to September 2021. The patients enrolled included 12 males and 12 females who underwent surgical excision of the mitral valve at the cardiac surgery department of Hainan General Hospital. The samples of mitral valve were collected during surgery treatment as the study group, and mitral valves collected from patients with ischemic heart disease were allocated into the control group. Hematoxylin-eosin (HE), oil red staining and immunohistochemical (IHC) staining were conducted to compare the expression of lipid metabolism-related proteins (ATP-binding cassette transporter A1 and acyl-coenzyme A: cholesterol acyltransferase-1), and real-time polymerase chain reaction (RT-PCR) was applied to compare the mRNA levels of ABCA1, ACAT1, and the inflammatory cytokines TNF-α, IL-10, and MCP-1.

RESULTS

In general, the rheumatic mitral valve showed leaflet thickening along with border adhesions and visible yellow fats. Oil red O staining also revealed the abovementioned results as well as fat cells. Both ABCA1 and ACAT1 were expressed in the rheumatic mitral valve via IHC, whereas only ACAT1 showed a faint level of expression in the ischemic mitral valve with no expression of ABCA1. In addition, compared with the ischemic mitral valve, RT-PCT showed increased mRNA expression levels of ABCA1, ACAT1, and the inflammatory cytokines TNF-α, IL-10, and MCP-1 (P < 0.05). After dividing the RMs into two groups for RT-PCR, we found that the higher the expression of ABCA1 and ACAT1 was, the lower the relative expression of inflammatory factors.

CONCLUSION

This study showed that adipose tissue, adipose cells, and lipid transport-related proteins were expressed strongly in the rheumatic mitral valve, suggesting that adipose tissue formation might be one of the important pathways in the pathology of rheumatic heart disease. In addition, adipose tissue and adipocytes were also involved in the inflammatory process. These data provide new insight into pathological mechanisms in rheumatic heart disease.

Characterization of an experimental model to determine streptococcal M protein–induced autoimmune cardiac and neurobehavioral abnormalities

Group A streptococcal (GAS) infection is associated with a spectrum of autoimmune diseases including acute rheumatic fever/rheumatic heart disease (ARF/RHD) and neurobehavioral abnormalities. Antibodies against GAS M proteins cross‐react with host tissue proteins in the heart and brain leading to the symptomatology observed in ARF/RHD. As throat carriage of Streptococcus dysgalactiae subspecies equisimilis (SDSE) has been reported to be relatively high in some ARF/RHD endemic regions compared with GAS, and both SDSE and GAS express coiled‐coil surface protein called M protein, we hypothesized that streptococci other than GAS can also associated with ARF/RHD and neurobehavioral abnormalities. Neurobehavioral assessments and electrocardiography were performed on Lewis rats before and after exposure to recombinant GAS and SDSE M proteins. Histological assessments were performed to confirm inflammatory changes in cardiac and neuronal tissues. ELISA and Western blot analysis were performed to determine the cross‐reactivity of antibodies with host connective, cardiac and neuronal tissue proteins. Lewis rats injected with M proteins either from GAS or SDSE developed significant cardiac functional and neurobehavioral abnormalities in comparison to control rats injected with phosphate‐buffered saline. Antibodies against GAS and SDSE M proteins cross‐reacted with cardiac, connective and neuronal proteins. Serum from rats injected with streptococcal antigens showed higher immunoglobulin G binding to the striatum and cortex of the brain. Cardiac and neurobehavioral abnormalities observed in our experimental model were comparable to the cardinal symptoms observed in patients with ARF/RHD. Here for the first time, we demonstrate in an experimental model that M proteins from different streptococcal species could initiate and drive the autoimmune‐mediated cardiac tissue damage and neurobehavioral abnormalities.

Gut dysbiosis in rheumatic diseases: A systematic review and meta-analysis of 92 observational studies

Background

Emerging evidence suggests that dysbiosis in gut microbiota may contribute to the occurrence or development of several rheumatic diseases. Since gut microbiota dysbiosis is potentially modifiable, it has been postulated to be a promising preventive or therapeutic target for rheumatic diseases. However, the current understanding on the potential associations between gut microbiota and rheumatic diseases is still inadequate. Therefore, we aimed to synthesise the accumulating evidence for the relation of gut microbiota to rheumatic diseases.

Methods

The PubMed, Embase and Cochrane Library were searched from inception to March 11, 2022 to include observational studies evaluating the associations between gut microbiota and rheumatic diseases. Standardised mean difference (SMD) of α-diversity indices between rheumatic diseases and controls were estimated using random-effects model. β-diversity indices and relative abundance of gut microbes were summarised qualitatively.

Findings

Of the included 92 studies (11,998 participants), 68 provided data for α-diversity. Taken together as a whole, decreases in α-diversity indices were consistently found in rheumatic diseases (observed species: SMD = −0.36, [95%CI = −0.63, −0.09]; Chao1: SMD = −0.57, [95%CI = −0.88, −0.26]; Shannon index: SMD = −0.33, [95%CI = −0.48, −0.17]; Simpson index: SMD = −0.32, [95%CI = −0.49, −0.14]). However, when specific rheumatic diseases were examined, decreases were only observed in rheumatoid arthritis (observed species: SMD = −0.51, [95%CI = −0.78, −0.24]; Shannon index: SMD = −0.31, [95%CI = −0.49, −0.13]; Simpson index: SMD = −0.31, [95%CI = −0.54, −0.08]), systemic lupus erythematosus (Chao1: SMD = −1.60, [95%CI = −2.54, −0.66]; Shannon index: SMD = −0.63, [95%CI = −1.08, −0.18]), gout (Simpson index: SMD = −0.64, [95%CI = −1.07, −0.22]) and fibromyalgia (Simpson index: SMD = −0.28, [95%CI = −0.44, −0.11]), whereas an increase was observed in systemic sclerosis (Shannon index: SMD = 1.25, [95%CI = 0.09, 2.41]). Differences with statistical significance in β-diversity were consistently reported in ankylosing spondylitis and IgG4-related diseases. Although little evidence of disease specificity of gut microbes was found, shared alterations of the depletion of anti-inflammatory butyrate-producing microbe (i.e., Faecalibacterium) and the enrichment of pro-inflammatory microbe (i.e., Streptococcus) were observed in rheumatoid arthritis, Sjögren's syndrome and systemic lupus erythematosus.

Interpretation

Gut microbiota dysbiosis was associated with rheumatic diseases, principally with potentially non-specific, shared alterations of microbes.

Funding

National Natural Science Foundation of China (81930071, 81902265, 82072502 and U21A20352).

Comparative analysis of the gut microbiota composition between knee osteoarthritis and Kashin-Beck disease in Northwest China

Background

Osteoarthritis (OA) and Kashin-Beck disease (KBD) both are two severe osteochondral disorders. In this study, we aimed to compare the gut microbiota structure between OA and KBD patients.

Methods

Fecal samples collected from OA and KBD patients were used to characterize the gut microbiota using 16S rDNA gene sequencing. To identify whether gut microbial changes at the species level are associated with the genes or functions of the gut bacteria between OA and KBD groups, metagenomic sequencing of fecal samples from OA and KBD subjects was performed.

Results

The OA group was characterized by elevated Epsilonbacteraeota and Firmicutes levels. A total of 52 genera were identified to be significantly differentially abundant between the two groups. The genera Raoultella, Citrobacter, Flavonifractor, g__Lachnospiraceae_UCG-004, and Burkholderia-Caballeronia-Paraburkholderia were more abundant in the OA group. The KBD group was characterized by higher Prevotella_9, Lactobacillus, Coprococcus_2, Senegalimassilia, and Holdemanella. The metagenomic sequencing showed that the Subdoligranulum_sp._APC924/74, Streptococcus_parasanguinis, and Streptococcus_salivarius were significantly increased in abundance in the OA group compared to those in the KBD group, and the species Prevotella_copri, Prevotella_sp._CAG:386, and Prevotella_stercorea were significantly decreased in abundance in the OA group compared to those in the KBD group by using metagenomic sequencing.

Conclusion

Our study provides a comprehensive landscape of the gut microbiota between OA and KBD patients and provides clues for better understanding the mechanisms underlying the pathogenesis of OA and KBD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02819-5.

From Streptococcal Pharyngitis/Tonsillitis to Myocarditis: A Systematic Review

(1) Background: Myocarditis following group A streptococcal pharyngitis and tonsillitis is a relatively rare medical condition. The aim of this systematic review was to identify specific ECG changes, laboratory parameters and signs, and symptoms associated with this disease. (2) Methods: A systematic literature review was performed in concordance with the current PRISMA guidelines, including the databases PubMed/MEDLINE, Web of Science, CDSR, CENTRAL, CCAs, EBM Reviews, and LILACS. Articles were included if they covered myocarditis after streptococcal pharyngitis/tonsillitis in humans. Exclusion criteria were rheumatic, autoimmune, or toxic myocarditis. (3) Results: Patients that developed myocarditis after group A streptococcal throat infection frequently presented with chest pain, elevated cardiac markers, and ST-segment elevations, making it a condition that shows more similarities to acute coronary syndrome than viral myocarditis. (4) Conclusions: Myocarditis after streptococcal pharyngitis and/or tonsillitis is a rather infrequently described disease; however, it is necessary to consider this condition when investigating streptococcal sore throat because it can be associated with severe adverse events for the individual patient.

CRESSP: a comprehensive pipeline for prediction of immunopathogenic SARS-CoV-2 epitopes using structural properties of proteins

The development of autoimmune diseases following SARS-CoV-2 infection, including multisystem inflammatory syndrome, has been reported, and several mechanisms have been suggested, including molecular mimicry. We developed a scalable, comparative immunoinformatics pipeline called cross-reactive-epitope-search-using-structural-properties-of-proteins (CRESSP) to identify cross-reactive epitopes between a collection of SARS-CoV-2 proteomes and the human proteome using the structural properties of the proteins. Overall, by searching 4 911 245 proteins from 196 352 SARS-CoV-2 genomes, we identified 133 and 648 human proteins harboring potential cross-reactive B-cell and CD8+ T-cell epitopes, respectively. To demonstrate the robustness of our pipeline, we predicted the cross-reactive epitopes of coronavirus spike proteins, which were recognized by known cross-neutralizing antibodies. Using single-cell expression data, we identified PARP14 as a potential target of intermolecular epitope spreading between the virus and human proteins. Finally, we developed a web application (https://ahs2202.github.io/3M/) to interactively visualize our results. We also made our pipeline available as an open-source CRESSP package (https://pypi.org/project/cressp/), which can analyze any two proteomes of interest to identify potentially cross-reactive epitopes between the proteomes. Overall, our immunoinformatic resources provide a foundation for the investigation of molecular mimicry in the pathogenesis of autoimmune and chronic inflammatory diseases following COVID-19.

Prothymosin Alpha: A Novel Contributor to Estradiol Receptor Alpha-Mediated CD8+ T-Cell Pathogenic Responses and Recognition of Type 1 Collagen in Rheumatic Heart Valve Disease

BACKGROUND

Rheumatic heart valve disease (RHVD) is a leading cause of cardiovascular death in low- and middle-income countries and affects predominantly women. The underlying mechanisms of chronic valvular damage remain unexplored and regulators of sex predisposition are unknown.

METHODS

Proteomics analysis of human heart valves (nondiseased aortic valves, nondiseased mitral valves [NDMVs], valves from patients with rheumatic aortic valve disease, and valves from patients with rheumatic mitral valve disease; n=30) followed by system biology analysis identified ProTα (prothymosin alpha) as a protein associated with RHVD. Histology, multiparameter flow cytometry, and enzyme-linked immunosorbent assay confirmed the expression of ProTα. In vitro experiments using peripheral mononuclear cells and valvular interstitial cells were performed using multiparameter flow cytometry and quantitative polymerase chain reaction. In silico analysis of the RHVD and Streptococcuspyogenes proteomes were used to identify mimic epitopes.

RESULTS

A comparison of NDMV and nondiseased aortic valve proteomes established the baseline differences between nondiseased aortic and mitral valves. Thirteen unique proteins were enriched in NDMVs. Comparison of NDMVs versus valves from patients with rheumatic mitral valve disease and nondiseased aortic valves versus valves from patients with rheumatic aortic valve disease identified 213 proteins enriched in rheumatic valves. The expression of the 13 NDMV-enriched proteins was evaluated across the 213 proteins enriched in diseased valves, resulting in the discovery of ProTα common to valves from patients with rheumatic mitral valve disease and valves from patients with rheumatic aortic valve disease. ProTα plasma levels were significantly higher in patients with RHVD than in healthy individuals. Immunoreactive ProTα colocalized with CD8⁺ T cells in RHVD. Expression of ProTα and estrogen receptor alpha correlated strongly in circulating CD8⁺ T cells from patients with RHVD. Recombinant ProTα induced expression of the lytic proteins perforin and granzyme B by CD8⁺ T cells as well as higher estrogen receptor alpha expression. In addition, recombinant ProTα increased human leukocyte antigen class I levels in valvular interstitial cells. Treatment of CD8⁺ T cells with specific estrogen receptor alpha antagonist reduced the cytotoxic potential promoted by ProTα. In silico analysis of RHVD and Spyogenes proteomes revealed molecular mimicry between human type 1 collagen epitope and bacterial collagen-like protein, which induced CD8⁺ T-cell activation in vitro.

CONCLUSIONS

ProTα-dependent CD8⁺ T-cell cytotoxicity was associated with estrogen receptor alpha activity, implicating ProTα as a potential regulator of sex predisposition in RHVD. ProTα facilitated recognition of type 1 collagen mimic epitopes by CD8⁺ T cells, suggesting mechanisms provoking autoimmunity.

Paediatric mitral valve disease - from presentation to management

Mitral valve diseases are relatively rare in the paediatric population; however, they can cause considerable mortality and morbidity worldwide. Acquired causes are a major contributor to cardiovascular disease burden in the paediatric population. Diseases can be detected before birth, at birth, or when the child is older and presents with symptoms of advanced heart failure. Definitive management consists of surgical intervention, with mitral valve replacement being the gold standard.Conclusion: Repair has been gaining popularity; however, its outcomes require further study. Percutaneous mitral balloon valvuloplasty is an emerging technique which holds promise as a bridge to surgical treatment. The effect of these interventions on quality of life must be emphasised and requires further study. What is Known: • The epidemiology of mitral valve disease in the paediatric population - predominant causes include rheumatic disease and congenital defects.  • Mitral valve repair and replacement are the standard treatment methods for paediatric mitral valve disease.  What is New: • Emergence of percutaneous mitral valve interventions and their potential as bridge-to-surgery or definitive treatment in high-risk surgical candidates.  • Recent evidence comparing mitral valve repair and replacement in the paediatric population demonstrates increasing popularity of repair techniques.

OUP accepted manuscript

Background

Group A Streptococcus (GAS) causes superficial pharyngitis and skin infections as well as serious autoimmune sequelae such as acute rheumatic fever (ARF) and subsequent rheumatic heart disease. ARF pathogenesis remains poorly understood. Immune priming by repeated GAS infections is thought to trigger ARF, and there is growing evidence for the role of skin infections in this process.

Methods

We utilized our recently developed 8-plex immunoassay, comprising antigens used in clinical serology for diagnosis of ARF (SLO, DNase B, SpnA), and 5 conserved putative GAS vaccine antigens (Spy0843, SCPA, SpyCEP, SpyAD, Group A carbohydrate), to characterize antibody responses in sera from New Zealand children with a range of clinically diagnosed GAS disease: ARF (n = 79), GAS-positive pharyngitis (n = 94), GAS-positive skin infection (n = 51), and matched healthy controls (n = 90).

Results

The magnitude and breadth of antibodies in ARF was very high, giving rise to a distinct serological profile. An average of 6.5 antigen-specific reactivities per individual was observed in ARF, compared to 4.2 in skin infections and 3.3 in pharyngitis.

Conclusions

ARF patients have a unique serological profile, which may be the result of repeated precursor pharyngitis and skin infections that progressively boost antibody breadth and magnitude.

Mapping Autoantibodies in Children With Acute Rheumatic Fever

Background

Acute rheumatic fever (ARF) is a serious sequela of Group A Streptococcus (GAS) infection associated with significant global mortality. Pathogenesis remains poorly understood, with the current prevailing hypothesis based on molecular mimicry and the notion that antibodies generated in response to GAS infection cross-react with cardiac proteins such as myosin. Contemporary investigations of the broader autoantibody response in ARF are needed to both inform pathogenesis models and identify new biomarkers for the disease.

Methods

This study has utilised a multi-platform approach to profile circulating autoantibodies in ARF. Sera from patients with ARF, matched healthy controls and patients with uncomplicated GAS pharyngitis were initially analysed for autoreactivity using high content protein arrays (Protoarray, 9000 autoantigens), and further explored using a second protein array platform (HuProt Array, 16,000 autoantigens) and 2-D gel electrophoresis of heart tissue combined with mass spectrometry. Selected autoantigens were orthogonally validated using conventional immunoassays with sera from an ARF case-control study (n=79 cases and n=89 matched healthy controls) and a related study of GAS pharyngitis (n=39) conducted in New Zealand.

Results

Global analysis of the protein array data showed an increase in total autoantigen reactivity in ARF patients compared with controls, as well as marked heterogeneity in the autoantibody profiles between ARF patients. Autoantigens previously implicated in ARF pathogenesis, such as myosin and collagens were detected, as were novel candidates. Disease pathway analysis revealed several autoantigens within pathways linked to arthritic and myocardial disease. Orthogonal validation of three novel autoantigens (PTPN2, DMD and ANXA6) showed significant elevation of serum antibodies in ARF (p < 0.05), and further highlighted heterogeneity with patients reactive to different combinations of the three antigens.

Conclusions

The broad yet heterogenous elevation of autoantibodies observed suggests epitope spreading, and an expansion of the autoantibody repertoire, likely plays a key role in ARF pathogenesis and disease progression. Multiple autoantigens may be needed as diagnostic biomarkers to capture this heterogeneity.

Proteomics Analysis Reveals Diverse Molecular Characteristics between Endocardial and Aortic-Valvular Endothelium

The variations in the protein profile of aortic-valvular (AVE) and endocardial endothelial (EE) cells are currently unknown. The current study's objective is to identify differentially expressed proteins and associated pathways in both the endothelial cells. We used endothelial cells isolated from the porcine (Sus scrofa) aortic valve and endocardium for the profiling of proteins. Label-free proteomics was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Our proteomics analysis revealed that 29 proteins were highly expressed, and 25 proteins were less expressed in the valve than the endocardial endothelium. The cell surface markers, such as CD63, ICAM1, PECAM1, PROCR, and TFRC, were highly expressed in EE. In contrast, CD44 was highly expressed in AVE. The pathway analysis showed that metabolic process-related proteins and extracellular matrix-related proteins were enriched in valves. Differential enrichment of signaling pathways was observed in the endocardium. The hemostasis function-related proteins were increased in both endothelial cells. The proteins and pathways enriched in aortic-valvular and endocardial endothelial cells revealed the distinct phenotype of these two closely related cells.

Antibody responses to collagen peptides and streptococcal collagen-like 1 proteins in acute rheumatic fever patients

Acute rheumatic fever (ARF) is a serious post-infectious immune sequelae of Group A streptococcus (GAS). Pathogenesis remains poorly understood, including the events associated with collagen autoantibody generation. GAS express streptococcal collagen-like proteins (Scl) that contain a collagenous domain resembling human collagen. Here, the relationship between antibody reactivity to GAS Scl proteins and human collagen in ARF was investigated. Serum IgG specific for a representative Scl protein (Scl1.1) together with collagen-I and collagen-IV mimetic peptides were quantified in ARF patients (n = 36) and healthy matched controls (n = 36). Reactivity to Scl1.1 was significantly elevated in ARF compared to controls (P < 0.0001) and this was mapped to the collagen-like region of the protein, rather than the N-terminal non-collagenous region. Reactivity to collagen-1 and collagen-IV peptides was also significantly elevated in ARF cases (P < 0.001). However, there was no correlation between Scl1.1 and collagen peptide antibody binding, and hierarchical clustering of ARF cases by IgG reactivity showed two distinct clusters, with Scl1.1 antigens in one and collagen peptides in the other, demonstrating that collagen autoantibodies are not immunologically related to those targeting Scl1.1. Thus, anti-collagen antibodies in ARF appear to be generated as part of the autoreactivity process, independent of any mimicry with GAS collagen-like proteins.

Left Ventricular Remodeling Following Balloon Mitral Valvuloplasty in Rheumatic Mitral Stenosis: Magnetic Resonance Imaging Study

Background: Rheumatic heart disease affects primarily cardiac valves, it could involve the myocardium either primarily or secondary to heart valve affection. The influence of balloon mitral valvuloplasty (BMV) on left ventricular function has not been sufficiently studied. Aim: To determine the influence of balloon mitral valvuloplasty (BMV) on both global and regional left ventricular (LV) function. Methods: Thirty patients with isolated rheumatic mitral stenosis (MS) were studied. All patients had cardiac magnetic resonance imaging (CMR) before, 6 months and 1 year after successful BMV. LV volumes, ejection fraction (EF), regional and global LV deformation, and LV late gadolinium enhancement were evaluated. Results: At baseline, patients had median EF of 57 (range: 45-69) %, LVEDVI of 74 (44-111) ml/m2 and LVESVI of 31 (14-57) ml/m2 with absence of late gadolinium enhancement in all myocardial segments. Six months following BMV, there was a significant increase in LV peak systolic global longitudinal strain (GLS) (-16.4 vs. -13.8, p < 0.001) and global circumferential strain (GCS) (-17.8 vs. -15.6, p = 0.002). At 1 year, there was a trend towards decrease in LVESVI (29 ml/m2, p = 0.079) with a significant increase in LV EF (62%, p < 0.001). A further significant increase, compared to 6 months follow up studies, was noticed in GLS (-17.9 vs. -16.4, p = 0.008) and GCS (-19.4 vs. -17.8 p = 0.03). Conclusions: Successful BMV is associated with improvement in global and regional LV systolic strain which continues for up to 1 year after the procedure.

Management of rheumatic aortic valve disease using the Ozaki procedure with autologous pericardium: a case report

Background

Rheumatic valve disease (RVD) is the most common cause of cardiovascular death in low-middle income nations. Surgical aortic valve (AV) interventions for RVD, especially in children, have proven problematic with graft failure, relapse, and poor compliance with anticoagulation. A novel technique involving neocuspidization of the aortic annulus using autologous pericardium to construct new AV leaflets (the Ozaki procedure) has shown promising outcomes in children with congenital AV disease; however, there are no previous recorded cases using this technique in children with RVD.

Case summary

We present the case of a 15-year-old male presenting with exertional angina and dyspnoea with a background of previous rheumatic fever. Echocardiography had shown a regurgitant tricuspid AV, left ventricular dilatation with mitral valve leaflet tethering. The patient underwent the Ozaki procedure for his AV regurgitation and was discharged following an uneventful post-operative recovery. The patient had full resolution of symptoms following the procedure and remains well 3 years following his operation.

Discussion

This case highlights that good outcomes with the Ozaki procedure in RVD are possible 3-years post-operatively and should prompt future studies to evaluate the procedure as a surgical option for paediatric patients in this clinical context. Additionally, the Ozaki procedure may also provide a cost-effective surgical technique requiring minimal additional operative resources and reduced follow-up demand, which would be critical in low-resource clinical settings where RVD is prevalent.

In Search of the Holy Grail: A Specific Diagnostic Test for Rheumatic Fever

Current diagnosis of Acute Rheumatic Fever and Rheumatic Heart Disease (ARF/RHD) relies on a battery of clinical observations aided by technologically advanced diagnostic tools and non-specific laboratory tests. The laboratory-based assays fall into two categories: those that (1) detect "evidence of preceding streptococcal infections" (ASOT, anti-DNAse B, isolation of the Group A Streptococcus from a throat swab) and (2) those that detect an ongoing inflammatory process (ESR and CRP). These laboratory tests are positive during any streptococcal infection and are non-specific for the diagnosis of ARF/RHD. Over the last few decades, we have accumulated considerable knowledge about streptococcal biology and the immunopathological mechanisms that contribute to the development, progression and exacerbation of ARF/RHD. Although our knowledge is incomplete and many more years will be devoted to understanding the exact molecular and cellular mechanisms involved in the spectrum of clinical manifestations of ARF/RHD, in this commentary we contend that there is sufficient understanding of the disease process that using currently available technologies it is possible to identify pathogen associated peptides and develop a specific test for ARF/RHD. It is our view that with collaboration and sharing of well-characterised serial blood samples from patients with ARF/RHD from different regions, antibody array technology and/or T-cell tetramers could be used to identify streptococcal peptides specific to ARF/RHD. The availability of an appropriate animal model for this uniquely human disease can further facilitate the determination as to whether these peptides are pathognomonic. Identification of such peptides will also facilitate testing of potential anti-streptococcal vaccines for safety and avoid potential candidates that may pre-dispose potential vaccine recipients to adverse outcomes. Such peptides can also be readily incorporated into a universally affordable point of care device for both primary and tertiary care.

Requirements for a Robust Animal Model to Investigate the Disease Mechanism of Autoimmune Complications Associated With ARF/RHD

The pathogenesis of Acute Rheumatic Fever/Rheumatic Heart Disease (ARF/RHD) and associated neurobehavioral complications including Sydenham's chorea (SC) is complex. Disease complications triggered by Group A streptococcal (GAS) infection are confined to human and determining the early events leading to pathology requires a robust animal model that reflects the hallmark features of the disease. However, modeling these conditions in a laboratory animal, of a uniquely human disease is challenging. Animal models including cattle, sheep, pig, dog, cat, guinea pigs rats and mice have been used extensively to dissect molecular mechanisms of the autoimmune inflammatory responses in ARF/RHD. Despite the characteristic limitations of some animal models, several rodent models have significantly contributed to better understanding of the fundamental mechanisms underpinning features of ARF/RHD. In the Lewis rat autoimmune valvulitis model the development of myocarditis and valvulitis with the infiltration of mononuclear cells along with generation of antibodies that cross-react with cardiac tissue proteins following exposure to GAS antigens were found to be similar to ARF/RHD. We have recently shown that Lewis rats injected with recombinant GAS antigens simultaneously developed cardiac and neurobehavioral changes. Since ARF/RHD is multifactorial in origin, an animal model which exhibit the characteristics of several of the cardinal diagnostic criteria observed in ARF/RHD, would be advantageous to determine the early immune responses to facilitate biomarker discovery as well as provide a suitable model to evaluate treatment options, safety and efficacy of vaccine candidates. This review focuses on some of the common small animals and their advantages and limitations.

Microbiota in Gut, Oral Cavity, and Mitral Valves Are Associated With Rheumatic Heart Disease

Rheumatic heart disease refers to the long-term damage of heart valves and results from an autoimmune response to group A Streptococcus infection. This study aimed to analyze the microbiota composition of patients with rheumatic heart disease and explore potential function of microbiota in this disease. First, we revealed significant alterations of microbiota in feces, subgingival plaques, and saliva of the patients compared to control subjects using 16S rRNA gene sequencing. Significantly different microbial diversity was observed in all three types of samples between the patients and control subjects. In the gut, the patients possessed higher levels of genera including Bifidobacterium and Eubacterium, and lower levels of genera including Lachnospira, Bacteroides, and Faecalibacterium. Coprococcus was identified as a super-generalist in fecal samples of the patients. Significant alterations were also observed in microbiota of subgingival plaques and saliva of the patients compared to control subjects. Second, we analyzed microbiota in mitral valves of the patients and identified microbes that could potentially transmit from the gut or oral cavity to heart valves, including Streptococcus. Third, we further analyzed the data using random forest model and demonstrated that microbiota in the gut, subgingival plaque or saliva could distinguish the patients from control subjects. Finally, we identified gut/oral microbes that significantly correlated with clinical indices of rheumatic heart disease. In conclusion, patients with rheumatic heart disease manifested important alterations in microbiota that might distinguish the patients from control subjects and correlated with severity of this disease.

Rheumatic Fever and Rheumatic Heart Disease in the United States

During the 1920s, acute rheumatic fever (ARF) was the leading cause of mortality in children in the United States. By the 1980s, many felt ARF had all but disappeared from the US. However, although ARF and rheumatic heart disease (RHD) rates remain low in the US today, disease burden is unequal and tracks along other disparities of cardiovascular health. It is estimated that 1% to 3% of patients with untreated group A streptococcus (GAS) infection, most typically GAS pharyngitis, will develop ARF, and of these, up to 60% of cases will result in chronic RHD. This article reviews the epidemiology, pathogenesis, diagnosis, and management of ARF/RHD to increase awareness of ARF/RHD for clinicians based in the US. [Pediatr Ann. 2021;50(3):e98-e104.].

Histopathological Characterization of Mitral Valvular Lesions from Patients with Rheumatic Heart Disease

BACKGROUND

The underlying mechanisms by which rheumatic heart disease (RHD) lead to severe valve dysfunction are not completely understood.

OBJECTIVE

The present study evaluated the histopathological changes in mitral valves (MV) seeking an association between the pattern of predominant valvular dysfunction and histopathological findings.

METHODS

In 40 patients who underwent MV replacement due to RHD, and in 20 controls that underwent heart transplant, histological aspects of the excised MV were analyzed. Clinical and echocardiographic data were also collected. Histological analyses were performed using hematoxylin-eosin staining. Inflammation, fibrosis, neoangiogenesis, calcification and adipose metaplasia were determined. A p value<0.05 was considered to be statistically significant.

RESULTS

The mean age of RHD patients was 53±13 years, 36 (90%) were female, whereas the mean age of controls was 50±12 years, similar to the cases, with the majority of males (70%). The rheumatic valve endocardium presented greater thickness than the controls (1.3±0.5 mm versus 0.90±0.4 mm, p=0.003, respectively), and a more intense inflammatory infiltrate in the endocardium (78% versus 36%; p=0.004), with predominance of mononuclear cells. Moderate to marked fibrosis occurred more frequently in rheumatic valves than in control valves (100% vs. 29%; p<0.001). Calcification occurred in 35% of rheumatic valves, especially among stenotic valves, which was associated with the mitral valve area (p=0.003).

CONCLUSIONS

Despite intense degree of fibrosis, the inflammatory process remains active in the rheumatic mitral valve, even at late disease with valve dysfunction. Calcification predominated in stenotic valves and in patients with right ventricular dysfunction.

Update on Post-Streptococcal Reactive Arthritis: Narrative Review of a Forgotten Disease

PURPOSE OF THE REVIEW

This topical review attempts to build the concepts of PSRA as an independent entity and discuss prevalent diagnostic criteria. It utilizes a search strategy to collate all clinical features of PSRA reported from across the world and also discusses laboratory and treatment options in brief.

RECENT FINDINGS

There are several immune-mediated diseases described after acute streptococcal infections. Post-streptococcal reactive arthritis (PSRA) is a sterile, self-limiting arthritis that occur as an immune sequelae to streptococcal infection. Though PSRA resembles the arthritis of acute rheumatic fever superficially, it is a separate entity in its own right. It is different from classical reactive arthritis too. It was being recognized worldwide and more frequently in the recent past, possibly due to heightened awareness amongst clinicians. However, research on this enigmatic immune phenomenon is limited. Most acceptable hypotheses suggest molecular mimicry sensitizing the immune system towards synovial peptides such as keratin, vimentin and laminin, leading to arthritis in a genetically predisposed individual. There is still much to be learnt from this unique disease about the vagaries of the immune system.

Collagen Binding Proteins of Gram-Positive Pathogens

Collagens are the primary structural components of mammalian extracellular matrices. In addition, collagens regulate tissue development, regeneration and host defense through interaction with specific cellular receptors. Their unique triple helix structure, which requires a glycine residue every third amino acid, is the defining structural feature of collagens. There are 28 genetically distinct collagens in humans. In addition, several other unrelated human proteins contain a collagen domain. Gram-positive bacteria of the genera Staphylococcus, Streptococcus, Enterococcus, and Bacillus express cell surface proteins that bind to collagen. These proteins of Gram-positive pathogens are modular proteins that can be classified into different structural families. This review will focus on the different structural families of collagen binding proteins of Gram-positive pathogen. We will describe how these proteins interact with the triple helix in collagens and other host proteins containing a collagenous domain and discuss how these interactions can contribute to the pathogenic processes.

The Limitations of the Rheumatogenic Concept for Group A Streptococcus: Systematic Review and Genetic Analysis

BACKGROUND

The concept that a minority of group A streptococcus (GAS) emm types are more "rheumatogenic" than others has been widely disseminated. We aimed to provide a comprehensive list of acute rheumatic fever-associated GAS isolates and assess the presence of associated rheumatogenic motifs.

METHODS

Articles reporting GAS emm-type or emm-type-specific antibody responses associated with rheumatic fever were identified from 1 January 1944 to 31 July 2018. The revised Jones criteria were used to define rheumatic fever with a maximum period of 4 weeks between disease onset and microbiological characterization. A database of 175 representative M-protein sequences was used to analyze the protein diversity of rheumatic fever-associated strains in a phylogenetic tree and to identify the presence of 10 previously recognized rheumatogenic motifs.

RESULTS

We included 411 cases of rheumatic fever, for which microbiological characterization identified 73 different emm types associated with the disease. The classic rheumatogenic emm types represented only 12.3% of the 73 emm types and were responsible for 31.6% of the 411 clinical cases. Rheumatic fever-associated emm types were disseminated throughout the phylogeny, suggesting they belong to various genetic backgrounds. Rheumatic fever-associated motifs were present in only 15.1% of the rheumatic fever-associated emm types and only 24.8% of clinical cases.

CONCLUSIONS

The concept of rheumatogenicity should be extended to include strains other than those classically described. Our results highlight significant knowledge gaps in the understanding of rheumatic fever pathogenesis and suggest that a GAS vaccine candidate should offer broad coverage against a variety of GAS genetic variants in order to protect against this serious sequela.

Experimental Rodent Models of Cardiovascular Diseases

Cardiovascular diseases, as the most common non-communicable disease in the world, cause a high mortality rate today and bring a serious medical burden to countries worldwide, especially in low- and middle-income countries. Experimental rodent models are widely used for cardiovascular diseases researches due to the effective simulation of human cardiovascular diseases, strong reproductive ability, and easy detection. Herein, we will summarize the pathological manifestations of common cardiovascular diseases and illustrate the establishment of corresponding experimental rodent models in detail.

Angiotensin Converting Enzyme Inhibitors (ACEIs) Decrease the Progression of Cardiac Fibrosis in Rheumatic Heart Disease Through the Inhibition of IL-33/sST2

Rheumatic heart disease (RHD) is common in developing countries and poses a big medical challenge and burden. The pathogenesis of RHD is influenced by the triad of host, agent, and environment. Autoantigens generated from Group A Streptococcus (GAS) infection are captured by the resident dendritic cells (DCs) in the heart's valvular endothelium. DCs differentiate into antigen presenting cells (APC) in the valve interstices. APC induces activation of autoreactive T cells, which triggers inflammation and tissue fibrosis. Cardiac fibrosis is promoted through the activation of Mitogen activated protein kinases (MAPKs) and its downstream signaling, including its interaction with transforming growth factor-β (TGF-β) and Smad proteins. TGF-β-induced phosphorylation of Smad2 complexes with Smad3 and Smad4, and translocates into the nucleus. Angiotensin II enhances the migration, maturation, and presentation of DC. In RHD, Angiotensin II induces fibrosis via the stimulation of TGF-β, which further increases the binding of IL-33 to sST2 but not ST2L, resulting in the upregulation of Angiotensin II and progression of cardiac fibrosis. This cascade of inflammation and valvular fibrosis causes calcification and stiffening of the heart valves in RHD. Angiotensin converting enzyme inhibitors (ACEIs) inhibit Angiotensin II production, which in turn decreases TGF-β expression and the onset of overt inflammatory response. This condition leads to a reduction in the sST2 as the decoy receptor to "steal" IL-33, and IL-33 binds to ST2L and results in cardioprotection against cardiac fibrosis in the pathogenesis of RHD.

Mechanistic implications of altered protein expression in rheumatic heart disease

Rheumatic heart disease (RHD) is a major cause of cardiovascular morbidity and mortality in low- and middle-income countries, where living conditions promote spread of group A β-haemolytic streptococcus. Autoimmune reactions due to molecular mimicry of bacterial epitopes by host proteins cause acute rheumatic fever (ARF) and subsequent disease progression to RHD. Despite knowledge of the factors that predispose to ARF and RHD, determinants of the progression to valvular damage and the molecular events involved remain incompletely characterised. This review focuses on altered protein expression in heart valves, myocardial tissue and plasma of patients with RHD and pathogenic consequences on RHD. Proteins mainly involved in structural organization of the valve matrix, blood homeostasis and immune response were altered due to RHD pathogenesis. Study of secreted forms of these proteins may aid the development of non-invasive biomarkers for early diagnosis and monitoring outcomes in RHD. Valve replacement surgery, the single evidence-based strategy to improve outcomes in severe RHD, is costly, largely unavailable in low- and middle-income countries (LMIC) and requires specialised facilities. When diagnosed early, penicillin prophylaxis may be used to delay progression to severe valvular damage. Echocardiography and cardiovascular magnetic resonance and the standard imaging tools recommended to confirm early diagnosis remain largely unavailable and inaccessible in most LMIC and both require expensive equipment and highly skilled persons for manipulation as well as interpretation of results. Changes in protein expression in heart valves and myocardium are associated with progressive valvular deformation in RHD. Understanding these protein changes should shed more light on the mechanisms of pathogenicity, while secreted forms of these proteins may provide leads towards a biomarker for non-invasive early detection of RHD.

Elevated antistreptolysin O titer is closely related to cardiac mitral insufficiency in untreated patients with Takayasu arteritis

Background

The etiology of Takayasu arteritis (TA) is unknown; however, a possible relationship between streptococcal infection and TA has been proposed. This study aimed to identify the clinical features and cardiac valvular involvement in untreated TA patients with an elevated antistreptolysin O (ASO) titer.

Methods

In this retrospective study, the clinical characteristics and features of valvular involvement were compared in TA patients with or without an elevated ASO titer.

Results

Of the 74 untreated TA patients, 13 patients were found have elevated ASO titers (17.6%). Mitral insufficiency was the most common in patients with elevated ASO (69.2%, 9/13), followed by aortic valve insufficiency (46.2%, 5/13) and tricuspid insufficiency (46.2%, 5/13), which were no significantly different than that in normal ASO group. The proportions of moderate to severe mitral (30.8% vs 1.6%, p = 0.000) and tricuspid valve (15.4% vs 1.64%, p = 0.023) insufficiency in the ASO positive group were significantly higher than those in the ASO negative group. The odds of mitral regurgitation in patients with elevated ASO titers were 3.9 times higher than those in the group with normal ASO titers (p = 0.053, OR = 3.929, 95% confidence interval [CI]: 0.983–15.694). Furthermore, the risk of moderate to severe mitral insufficiency in patients with elevated ASO titers was 41.6 times higher than that in patients with normal ASO titers (p = 0.002, OR = 41.600, 95% CI: 3.867–447.559).

Conclusions

An increase in ASO titer is related to valvular involvement in TA and is closely linked to mitral insufficiency.

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.

Case Report: Concurrent Rheumatic Fever and Acute Post-Streptococcal Glomerulonephritis in a High-Burden Setting

We report a case of acute rheumatic fever with severe pancarditis occurring simultaneously with probable acute post-streptococcal glomerulonephritis in a previously well, Australian Aboriginal, 29-year-old male. These autoimmune streptococcal sequelae are usually considered pathogenetically distinct, and concurrence has not previously been reported from this high-burden setting. We hypothesize that a single type of infecting group A Streptococcus (Strep A) triggered both autoimmune sequelae. Salient features included mitral and aortic regurgitation that worsened during the acute illness, painful pericarditis, and high troponin; severe acute kidney injury with oliguria, hematuria, and macroalbuminuria; reduced complement (C3); and elevated streptococcal serology. The case highlights important diagnostic and management challenges. It also illustrates the serious morbidity impact of the complications of Strep A.