HLA class II associations with rheumatic heart disease are more evident and consistent among clinically homogeneous patients

Risk Factors for Acute Rheumatic Disease: Exploring Factors at Individual and Collective Levels

Acute rheumatic fever (ARF) is a complex disease with several clinical manifestations. Its most significant long-term complication is valvular heart damage, commonly referred to as chronic rheumatic heart disease. The risk of ARF varies globally, with over 80% of cases occurring in low- and middle-income countries, highlighting the role of socioeconomic factors. A comprehensive understanding of the risk factors associated with ARF and its clinical, genetic, and sociodemographic mediators can help clinicians identify high-risk individuals, develop effective management strategies, enhance target screening and active case-finding initiatives, and ultimately improve patient outcomes. This review aimed to provide an overview of ARF and its global burden, focusing on the established and potential risk factors associated with its development.

Precision Medicine in Congenital Heart Disease, Rheumatic Heart Disease, and Kawasaki Disease of Children: An Overview of Literature

Congenital heart disease and common acquired heart diseases like Kawasaki disease and rheumatic heart disease are prevalent cardiovascular conditions in children worldwide. Despite the availability of treatment options, they continue to be significant contributors to morbidity and mortality. Advancements in early diagnosis, improvements in treatment approaches, and overcoming resistance to available treatments are crucial to reduce morbidity. Researchers have turned to precision medicine to tackle these challenges. We aimed to analyze the existing literature concerning the utilization of precision medicine in congenital heart disease, rheumatic heart disease, and Kawasaki disease. The emphasis is placed on comprehending the key themes explored in these studies and evaluating the present state of their clinical integration. The central theme of most studies revolves around the examination of genetic factors. Despite promising research outcomes, limitations in these studies indicate that the clinical implementation of precision medicine in these conditions remains a distant prospect, necessitating additional exploration and attention to confounding factors.

HLA-II-Dependent Neuroimmune Changes in Group A Streptococcal Necrotizing Fasciitis

Streptococcus pyogenes (Group A Streptococcus, GAS) bacteria cause a spectrum of human diseases ranging from self-limiting pharyngitis and mild, uncomplicated skin infections (impetigo, erysipelas, and cellulitis) to highly morbid and rapidly invasive, life-threatening infections such as streptococcal toxic shock syndrome and necrotizing fasciitis (NF). HLA class II allelic polymorphisms are linked with differential outcomes and severity of GAS infections. The dysregulated immune response and peripheral cytokine storm elicited due to invasive GAS infections increase the risk for toxic shock and multiple organ failure in genetically susceptible individuals. We hypothesized that, while the host immune mediators regulate the immune responses against peripheral GAS infections, these interactions may simultaneously trigger neuropathology and, in some cases, induce persistent alterations in the glial phenotypes. Here, we studied the consequences of peripheral GAS skin infection on the brain in an HLA-II transgenic mouse model of GAS NF with and without treatment with an antibiotic, clindamycin (CLN). Mice expressing the human HLA-II DR3 (DR3) or the HLA-II DR4 (DR4) allele were divided into three groups: (i) uninfected controls, (ii) subcutaneously infected with a clinical GAS strain isolated from a patient with GAS NF, and (iii) GAS-infected with CLN treatment (10 mg/kg/5 days, intraperitoneal). The groups were monitored for 15 days post-infection. Skin GAS burden and lesion area, splenic and hippocampal mRNA levels of inflammatory markers, and immunohistochemical changes in hippocampal GFAP and Iba-1 immunoreactivity were assessed. Skin GAS burden and hippocampal mRNA levels of the inflammatory markers S100A8/A9, IL-1β, IL-33, inflammasome-related caspase-1 (Casp1), and NLRP6 were elevated in infected DR3 but not DR4 mice. The levels of these markers were significantly reduced following CLN treatment in DR3 mice. Although GAS was not detectable in the brain, astrocyte (GFAP) and microglia (Iba-1) activation were evident from increased GFAP and Iba-1 mRNA levels in DR3 and DR4 mice. However, CLN treatment significantly reduced GFAP mRNA levels in DR3 mice, not DR4 mice. Our data suggest a skin-brain axis during GAS NF, demonstrating that peripherally induced pathological conditions regulate neuroimmune changes and gliotic events in the brain.

Association of HLA class II DR/DQ alleles in children and adolescents with rheumatic heart disease from a tertiary care centre in North India

INTRODUCTION

Rheumatic fever and RHD constitutes an important public health problem in India. The relatively low attack rate of RF, the high concordance rate for RF in monozygotic twins (19%) compared to dizygotic twins (2.5%), and the high familial incidence of RF suggest the involvement of host genetic factors in susceptibility to RF with consequential progression to RHD.

OBJECTIVE

To study the association of HLA CLASS II DR/DQ alleles in children and adolescents with RHD from a tertiary care center in North India.

METHODS

30 RHD patients and 30 age and sex-matched controls were included in our study and blood samples for HLA typing were processed through LAB Type™ reverse SSO DNA typing method. The assignment of the HLA typing was based on a comparison with already published HLA gene sequences.

RESULTS

The mean age of RHD patients and matched control groups were 12.97 ± 2.95 and 11.93 ± 3.23, respectively. In the cases and control group, males accounted for 63.3% and 50% of the patients respectively. A significant difference was found between the cases and controls for HLA DR∗ 15 (p-value 0.002), HLA DR∗ B4 (p-value 0.045), HLA DR∗ B5 (p-value 0.017), and HLA DQB1∗ 02 (p-value 0.005).

CONCLUSION

Our study suggests that HLA class II haplotypes may provide insight into the molecular mechanism of RHD and be a useful tool in predicting the clinical outcome in RF patients, thereby affording new means of intervention or vaccine design. Larger studies are needed to address this in our population.

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.

The Genetic Control of the Rheumatic Heart: Closing the Genotype-Phenotype Gap

Rheumatic heart disease (RHD) is a heritable inflammatory condition characterized by carditis, arthritis, and systemic disease. Although remaining neglected, the last 3 years has seen some promising advances in RHD research. Whilst it is clear that RHD can be triggered by recurrent group A streptococcal infections, the mechanisms driving clinical progression are still poorly understood. This review summarizes our current understanding of the genetics implicated in this process and the genetic determinants that predispose some people to RHD. The evidence demonstrating the importance of individual cell types and cellular states in delineating causal genetic variants is discussed, highlighting phenotype/genotype correlations where possible. Genetic fine mapping and functional studies in extreme phenotypes, together with large-scale omics studies including genomics, transcriptomics, epigenomics, and metabolomics, are expected to provide new information not only on RHD but also on the mechanisms of other autoimmune diseases and facilitate future clinical translation.

The number and activity of CD3+TCR Vα7.2+CD161+ cells are increased in children with acute rheumatic fever

BACKGROUND

Acute rheumatic fever (ARF) is an autoimmune disease caused by group A β-hemolytic streptococci (GAS) and may develop into rheumatic heart disease (RHD). The pathogenesis of ARF and RHD involves molecular mimicry and antibody-mediated mechanisms. T cell involvement is described in various stages of the disease. Mucosal associated invariant T (MAIT) cells are enriched at the mucosa and are present in the blood and may be activated by GAS.

METHODS

In this study, we investigated the quantity and activity of CD3⁺TCRVα7.2⁺CD161⁺ cells in the active and recovered ARF patients and healthy controls. Twenty newly diagnosed, 20 recovered-ARF children, and 20 healthy controls were enrolled in the study. Peripheral blood (PB) mononuclear cells were isolated by Ficoll-Paque density gradient. CD4⁺, CD4^- subsets of CD3⁺CD161⁺TCRVα7.2⁺ cells and IFN-γ and TNF-α production were quantified by Flow cytometry.

RESULTS

Acute and recovered ARF patients had significantly elevated the number of CD3⁺TCRVα7.2⁺CD161⁺ cells in their PB. Both CD4⁺ and CD4^- subsets were increased. Moreover, total CD3⁺TCRVα7.2⁺CD161⁺ cell numbers were significantly higher in the recovered patients' PB compared with active ARF patients. In addition, CD3⁺TCRVα7.2⁺CD161⁺ cells in both acute and recovered patients produced significantly more IFN-γ and TNF-α. Non-MAIT total CD3⁺ T cell, CD4⁺ and CD4^- T cell subsets were also increased in active and recovered ARF patients and they also produced more IFN-γ and TNF-α.

CONCLUSION

Our data reveal that CD3⁺TCRVα7.2⁺CD161⁺ cells are elevated and actively producing IFN-γ and TNF-α in acute and recovered ARF patients and may contribute to ARF pathology.

Association of HLA-DRB1 Alleles with Rheumatic Fever and Rheumatic Heart Disease: A Meta-analysis

BACKGROUND

Rheumatic fever (RF) and its sequel rheumatic heart disease (RHD) is an autoimmune disease caused by an abnormal host immune response to group A streptococcus (GAS) infection. The HLA class II molecules are entailed in immune-mediated infectious, inflammatory, and autoimmune diseases including RHD. However, HLA class II genes are reported to be associated with RF/RHD across different populations with a very little consistency.

OBJECTIVE

The aim of the study is to investigate the association between HLA class II genes and RF/RHD by meta-analysis.

METHODS

A comprehensive literature search was conducted to identify all relevant case-control studies published before December 31, 2019. The data were extracted using standardized form and pooled odds ratio (OR) with 95% confidence interval (CI) are calculated to assess the strength of the association between HLA class II genes and RF/RHD.

RESULTS

Thirteen studies for HLA-DRB1 alleles (1065 patients and 1691 controls) and eight studies for HLA-DQB1 alleles (644 patients and 1088 controls) were finally included. The meta-analysis showed a significantly higher frequency of HLA-DRB1*07 allele (OR = 1.68, P < .0001) in RF/RHD patients when compared to controls, while the frequency of HLA-DRB1*15 allele (OR = 0.60, P = .03) was significantly lower in RF/RHD patients than in controls. However, there were no significant differences in the frequency of HLA-DQB1 alleles between RF/RHD patients and controls.

CONCLUSIONS

The results of the meta-analysis suggest that the differential presentation of autoimmune peptides by HLA-DRB1*07 (susceptible) and HLA-DRB1*15 (protective) alleles with different affinities may play a crucial role in the pathogenesis of RF/RHD.

Group A Streptococcus Adsorbed Vaccine: Repeated Intramuscular Dose Toxicity Test in Minipigs

Streptococcus pyogenes infection continues to be a worldwide public health problem causing various diseases in humans and plays an important role in the pathogenesis of rheumatic fever and rheumatic heart disease. We developed a vaccine candidate to prevent S. pyogenes infections, identified as StreptInCor, that presented promising results in mouse models. A certified and independent laboratory conducted two repeated intramuscular dose toxicity tests (28 days, four weekly injections). The first test, composed of four experimental groups treated with 0 (vehicle), 50, 100 or 200 µg/500 µL StreptInCor, did not show significant alterations in clinical, hematological, biochemical or anatomopathological parameters related to the administration of StreptInCor. In addition to the parameters mentioned above, we evaluated the cardiac function and valves of animals by echocardiography before and after administration of 200 µg/500 µL StreptInCor versus placebo. We did not observe any changes related to StreptInCor administration, including changes in cardiac function and valves in animals, after receiving the highest dose of this vaccine candidate. The results obtained in the two repeated intramuscular dose toxicity tests showed that this vaccine formulation did not induce harmful effects to the tissues and organs studied, indicating that the candidate vaccine is well tolerated in minipigs.

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.

Update on rheumatic heart disease

PURPOSE OF REVIEW

The purpose is to provide a broad overview of the current state of knowledge of pathogenesis, diagnosis, and management of rheumatic heart disease (RHD).

RECENT FINDINGS

Studies on pathogenesis of RHD have focused on autoimmunity because of molecular mimicry between the streptococcal M antigen α-helical coiled-coil structure and sarcomeric proteins such as myosin and tropomyosin. More recently, nonsarcomeric autoantigens, endothelial injury and the innate immune system have been proposed to play key roles in the pathogenesis of RHD. In the 2015 revised Jones Criteria, the importance of echocardiography and subclinical carditis in the diagnosis of acute rheumatic fever is highlighted. Experimental studies with targeted anti-inflammatory therapeutics have been largely unsuccessful and the only established treatment is still lifelong antibiotics. Efforts to improve patient selection and outcomes with percutaneous mitral balloon valvuloplasty are ongoing. With regard to surgical management, several groups have demonstrated excellent operative and midterm outcomes from valve repair as opposed to valve replacement.

SUMMARY

There are still many unanswered questions regarding RHD pathogenesis. The only accepted medical treatment is still long-term antibiotic therapy, whereas advances in mitral repair techniques have led to successful durable repairs being performed in high-volume, expert centers.

Association of IL-1β +3953 C and HLA-DRB1*15 with Coronary Artery and Rheumatic Heart Diseases in South India

Among the various candidate genes predisposing for cardiovascular diseases, HLA-DRB1* and IL-1β +3953C/T alleles have been implicated repeatedly. To test these in South India, we carried out a case control study of 323 Coronary Artery Disease (CAD) patients, 56 Rheumatic Heart Disease (RHD) patients and 254 endemic controls. The polymorphisms were studied by PCR - SSP and ARMS-PCR methods and results analyzed for various clinical and demographic parameters. In CAD, HLA-DRB1*14 allele showed significant predisposition (OR: 2.19; 95% CI: 1.04-4.58; p value=0.023), particularly in male patients (OR: 4.07; 95% CI: 1.20-13.81; p value=0.01) and further in males with Triple Vessel Disease (OR: 5.49; 95% CI: 1.45-20.60; p value=0.007). On the other hand, HLA-DRB1*15 predisposed for RHD (OR: 3.56; 95% CI: 1.87-6.78; p value=0.001) in both the genders. Population stratification showed this higher risk association in Vanniyar caste (OR: 5.00; 95% CI: 1.27-19.59; p value=0.022). Among the IL1-β +3953C/T polymorphism, the ancestral allele 'C' showed a significant high risk association with CAD (OR: 1.83; 95% CI: 1.24-2.70; p value=0.001), particularly in Mudaliar (OR: 6.07; 95% CI: 1.77-20.74; p value=0.003; AF=0.7) and Vanniyar castes (OR: 3.67; 95% CI: 0.92-14.57; p value=0.05; AF=0.660). Two different cardiac ailments studied, RHD & CAD thus showed varied associations in this South Indian cohorts. RHD having an infectious aetiology shared a HLA-DRB1*15 high risk association, while HLA-DRB1*14 and IL-1β +3953C predisposed for CAD, an inflammatory disorder, reiterating the diverse genetic predisposition of the two cardiac ailments studied.

Acute rheumatic fever and rheumatic heart disease

Acute rheumatic fever (ARF) is the result of an autoimmune response to pharyngitis caused by infection with group A Streptococcus. The long-term damage to cardiac valves caused by ARF, which can result from a single severe episode or from multiple recurrent episodes of the illness, is known as rheumatic heart disease (RHD) and is a notable cause of morbidity and mortality in resource-poor settings around the world. Although our understanding of disease pathogenesis has advanced in recent years, this has not led to dramatic improvements in diagnostic approaches, which are still reliant on clinical features using the Jones Criteria, or treatment practices. Indeed, penicillin has been the mainstay of treatment for decades and there is no other treatment that has been proven to alter the likelihood or the severity of RHD after an episode of ARF. Recent advances - including the use of echocardiographic diagnosis in those with ARF and in screening for early detection of RHD, progress in developing group A streptococcal vaccines and an increased focus on the lived experience of those with RHD and the need to improve quality of life - give cause for optimism that progress will be made in coming years against this neglected disease that affects populations around the world, but is a particular issue for those living in poverty.

Post-infectious group A streptococcal autoimmune syndromes and the heart

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges.

Left atrial asynchrony and mechanical function in patients with mitral stenosis before and immediately after percutaneous balloon mitral valvuloplasty: a real time three-dimensional echocardiography study

OBJECTIVE

This study evaluated the feasibility of assessing left atrium (LA) function and asynchrony in patients with rheumatic mitral stenosis (MS) before and immediately after percutaneous balloon mitral valvuloplasty (PBMV) by real time three-dimensional echocardiography (RT3DE).

METHODS

Thirty patients with rheumatic MS who underwent PBMV and 30 controls were enrolled. RT3DE was used to measure LA volume and function, the standard deviation of time to the minimal systolic volume divided into 16 segments, 12 segments, or 6 segments (Tmsv 16-SD, Tmsv 12-SD, Tmsv 6-SD), and the maximum differences (Tmsv 16-Dif, 12-Dif, 6-Dif) in RT3DE derived values in MS patients before and 2 days after PBMV were obtained and compared with those of normal controls. The associations between the LA asynchrony and heart volume, function, mitral valve area (MVA), maximum mitral valve gradient (MVGmax ), mean mitral valve gradient (MVGmean), and mean LA pressure (MLAP) were investigated.

RESULTS

Left atrium asynchrony indexes were significantly larger, and LA function parameters were significantly lower in the MS group than in the controls (P < 0.05 for all). Of all the LA asynchrony indexes, LA Tmsv16-SD was most significantly correlated with the LA volume and function parameters, MVGmax , MVGmean , and MLAP (P < 0.05 for all). LA asynchrony indexes and LA volume significantly deceased, and LA function significantly increased post-PBMV (P < 0.05).

CONCLUSION

Real time three-dimensional echocardiography is a reliable and reproducible method to quantify LA function and asynchrony. RT3DE revealed a significant, early improvement in LA function and asynchrony in MS patients after PBMV.

Rheumatic heart disease in Uganda: the association between MHC class II HLA DR alleles and disease: a case control study

BACKGROUND

Rheumatic heart disease (RHD), the only long term consequence of acute rheumatic fever, remains a leading cause of morbidity and mortality among young adults in Uganda. An inherited susceptibility to acute rheumatic fever centers around the major histocompatibility class II human leucocyte antigens. However, there is paucity of data from sub-Saharan Africa. This study compares the frequency of HLA class II DR alleles between RHD cases and normal controls in Uganda.

METHODS

One hundred ninety-nine participants including 96 established RHD cases aged 5-60 years and 103 age and sex matched normal controls were recruited for participation. DNA was manually extracted from buffy coat samples and HLA analysis was performed. HLA-DR allelic frequency comparison between cases and controls were estimated using conditional logistic regression with 95% confidence intervals. P -values were corrected for multiple hypothesis testing.

RESULTS

199 participants (103 female, 51.8%) completed the study. The mean (SD) age in years for cases and controls were 29.6 (10.2) and 29(18), respectively. After conditional logistic regression and multiple hypothesis testing, HLA-DR1was associated with a decreased risk of RHD (OR = 0.42, CI 0.21-085, P = 0.01, Corrected P value (PC) = 0.09,) while HLA-DR11 was associated with increased risk of RHD (OR = 3.31, CI 1.57-6.97, P = <0.001, Pc < 0.001). No other significant associations were found.

CONCLUSION

In this first study of HLA genetic susceptibility to RHD in Uganda, HLA- DR1 was more common in normal controls while HLA- DR11 was more common among RHD cases suggesting a disease susceptibility association. In future studies, high resolution HLA analysis and genome wide studies should be carried out to confirm this pattern.

The HLA Class II Associations with Rheumatic Heart Disease in South Indian Patients: A Preliminary Study

INTRODUCTION

Rheumatic heart disease (RHD) occurs in 30-45% of the patients with rheumatic fever (RF) and it leads to chronic valvular lesions. The human leukocyte antigen (HLA) might confer a susceptibility to RHD. The aim of the present study was to determine the prevalent HLA class II DR/DQ allelic types which were associated with rheumatic heart disease (RHD) in a small group of south Indian patients and to compare them with those in the control subjects.

METHODS

A total of 23 patients who were diagnosed with RHD and 6 control samples were included in this study. A low resolution HLA Class II DR/DQ typing was performed on the blood samples by the PCR-SSP method.

RESULTS AND CONCLUSION

The DRB3*01:01:02:01 allele showed a positive association with RHD, whereas the DQB1 loci alleles did not show any significant association.

Cutting edge issues in rheumatic fever

Although the incidence of acute rheumatic fever and rheumatic heart disease has decreased significantly in regions of the world where antibiotics are easily accessible, there remains a high incidence in developing nations as well as in certain regions where there is a high incidence of genetic susceptibility. These diseases are a function of poverty, low socioeconomic status, and barriers to healthcare access, and it is in the developing world that a comprehensive prevention program is most critically needed. Development of group A streptococcal vaccines has been under investigation since the 1960s and 50 years later, we still have no vaccine. Factors that contribute to this lack of success include a potential risk for developing vaccine-induced rheumatic heart disease, as well as difficulties in covering the many serological subtypes of M protein, a virulence factor found on the surface of the bacterium. Yet, development of a successful vaccine program for prevention of group A streptococcal infection still offers the best chance for eradication of rheumatic fever in the twenty-first century. Other useful approaches include continuation of primary and secondary prevention with antibiotics and implementation of health care policies that provide patients with easy access to antibiotics. Improved living conditions and better hygiene are also critical to the prevention of the spread of group A streptococcus, especially in impoverished regions of the world. The purpose of this article is to discuss current and recent developments in the diagnosis, pathogenesis, and management of rheumatic fever and rheumatic heart disease.

Genes, autoimmunity and pathogenesis of rheumatic heart disease

Pathogenesis of rheumatic heart disease (RHD) remains incompletely understood. Several genes associated with RHD have been described; most of these are involved with immune responses. Single nucleotide polymorphisms in a number of genes affect patients with RHD compared to controls. Molecular mimicry between streptococcal antigens and human proteins, including cardiac myosin epitopes, vimentin and other intracellular proteins is central to the pathogenesis of RHD. Autoreactive T cells migrate from the peripheral blood to the heart and proliferate in the valves in response to stimulation with specific cytokines. The types of cells involved in the inflammation as well as different cytokine profiles in these patients are being investigated. High TNF alpha, interferon gamma, and low IL4 are found in the rheumatic valve suggesting an imbalance between Th1 and Th2 cytokines and probably contributing to the progressive and permanent valve damage. Animal model of ARF in the Lewis rat may further contribute towards understanding the ARF.

HLA class I and class II HLA DRB profiles in Egyptian children with rheumatic valvular disease

Poststreptococcal sequelae, especially acute rheumatic fever/rheumatic heart disease continues to occur in significant proportions in many parts of the world, especially in less developed countries. An important factor in the study of rheumatic heart disease is the human genetic susceptibility to the disease. The aim of the present study was to detect the most prevalent HLA class I and class II types associated with risk of rheumatic heart disease in Egyptian children. Our study was performed on 100 patients with rheumatic valvular heart diseases and 71 control subjects. Patients were recruited from the Heart Institute, Embaba, Egypt. HLA typing for HLA class I was performed by serotyping and HLDR allele genotyping was performed using INNO-LiPA kits. In the study of HLA class I, there was a statistically significant increase in the B5 allele (P = 0.03; odds ratio, 3.46 [1.12-10.72]) in patients compared to controls, while B49 and B52 alleles (P = 0.004 and P = 0.02) were found in controls only. There was a statistically significant increase in HLA DR* 04-02, 3.46 (1.12-10.72) and HLA DR *10-0101 5.75 (1.27-25.98) in patients. Meanwhile HLA DR*1309120 was found only in controls (P = 0.02). Our study provides further information on the genetic predisposition for rheumatic valvular disease and the protective genotypes in rheumatic heart disease. Further insight into the molecular mechanisms of the disease will be a useful tool for predicting clinical outcome in those patients and, thus, potentially offer new means and approaches to treatment and prophylaxis, including a potential vaccine.

Molecular mimicry in the autoimmune pathogenesis of rheumatic heart disease

Molecular mimicry is a hallmark of the pathogenesis of rheumatic fever where the streptococcal group A carbohydrate epitope, N-acetyl glucosamine, and the a-helical coiled-coil streptococcal M protein structurally mimic cardiac myosin in the human disease, rheumatic carditis, and in animal models immunized with streptococcal M protein and cardiac myosin. Recent studies have unraveled the potential pathogenic mechanisms by which the immune response against the group A streptococcus attacks the rheumatic valve leading to chronic rheumatic heart disease. Both B- and T-cell responses are involved in the process, and evidence for the hypotheses of molecular mimicry and epitope spreading are reviewed.

HLA class II DR and DQ genotypes and haplotypes associated with rheumatic fever among a clinically homogeneous patient population of Latvian children

The HLA system is being paid more and more attention because it is very significant in polymorphous immunological reactions. Several studies have suggested that genetic susceptibility to rheumatic fever (RF) and rheumatic heart disease (RHD) is linked to HLA class II alleles. We hypothesized that HLA class II associations within RHD may be more consistent if analysed amongst patients with a relatively homogeneous clinical outcome. A total of 70 RF patients under the age of 18 years were surveyed and analysed in Latvia. HLA genotyping of DQA1, DQB1 and DRB1 was performed using PCR with amplification with sequence-specific primers. We also used results from a previous study of DQB1 and DRB1 genotyping. In the RF patients, HLA class II DQA1*0401 was found more frequently compared to DQA1*0102. In the RF homogeneous patient groups, DQA1*0402 has the highest odds ratio. This is also the case in the multivalvular lesion (MVL) group, together with DQA1*0501 and DQA1*0301. In the chorea minor patients, DQA1*0201 was often found. Significant HLA DQA1 protective genotypes were not detected, although DQA1 genotypes *0103/*0201 and *0301/*0501 were found significantly and frequently. In the distribution of HLA DRB1/DQA1 genotypes, *07/*0201 and *01/*0501 were frequently detected; these also occurred significantly often in the MVL group. The genotype *07/*0201 was frequently found in Sydenhamn's chorea patients that had also acquired RHD, but DRB1*04/DQA1*0401 was often apparent in RF patients without RHD. In the distribution of HLA DQA1/DQB1 genotypes, both in RF patients and in the homogeneous patient groups, the least frequent were *0102/*0602-8. The genotype DQA1*0501 with the DQB1 risk allele *0301 was often found in the MVL group. The genotype *0301/*0401-2 was frequently found in the RF and Sydenhamn's chorea patient groups. The haplotype *07-*0201-*0302 was frequently found in RF and homogeneous patient groups, including the MVL group. In addition, haplotypes *04-*0401-*0301 and *04-*0301-*0401-2 were frequent amongst patients with Sydenhamn's chorea. The protective alleles DQA1*0102 and DQB1*0602-8 in the haplotype DRB1*15 were less frequently found in RF patients. The results of the present study support our hypothesis and indicate that certain HLA class II haplotypes are associated with risk for or protection against RHD and that these associations are more evident in patients in clinically homogeneous groups.

Rheumatic fever: from innate to acquired immune response

Rheumatic fever (RF) is triggered by S. pyogenes and affects 3-4% of untreated susceptible children. The immune response against streptococcal antigens can lead cross-recognition of heart tissue proteins resulting in rheumatic heart disease (RHD). HLA class II alleles have been associated with the development of RF/RHD. Tumor necrosis factor (TNF)-alpha is also located in the same chromosomal region of HLA genes and has been investigated in RHD patients from Mexico, Turkey, and Brazil. Associations with the TNFA-308 allele were found and probably are related to the development of valvular lesions. A deficient mannose-binding lectin (MBL) allele was found in Brazilian patients. MBL is a protein important for the first line of host defense against the bacteria. The association with diverse genes probably indicates a role of certain molecules in both the innate and adaptive immune response. Antigen-presenting cells bearing the HLA-DR7 molecule from RHD patients preferentially recognized a heart-tissue protein cross-reactive M5 (81-96) peptide. The same peptide was also recognized by heart tissue T cell clones. Cardiac myosin peptides were recognized by high numbers of intralesional T cell clones. The cytokine pattern of infiltrating mononuclear cells in both myocardium and valvular tissue showed a predominance of proinflammatory cytokines (TNF-alpha and IFN-gamma) and scarce production of regulatory cytokines, such as IL-4, in the valve tissue. IL-10, a predominant regulatory cytokine, was also secreted by large numbers of cells in both valve and myocardium tissue. Data here indicate the complexity of immune reactions leading to autoimmune lesions in RF/RHD.

Rheumatic fever and rheumatic heart disease: genetics and pathogenesis

Molecular mimicry between streptococcal and human proteins is considered as the triggering factor leading to autoimmunity in rheumatic fever (RF) and rheumatic heart disease (RHD). Here, we present a review of the genetic susceptibility markers involved in the development of RF/RHD and the major immunopathological events underlying the pathogenesis of RF and RHD. Several human leucocyte antigen (HLA) class II alleles are associated with the disease. Among these alleles, HLA-DR7 is predominantly observed in different ethnicities and is associated with the development of valvular lesions in RHD patients. Cardiac myosin is one of the major autoantigens involved in rheumatic heart lesions and several peptides from the LMM (light meromyosin) region were recognized by peripheral and intralesional T-cell clones from RF and RHD patients. The production of TNF-alpha and IFN-gamma from heart-infiltrating mononuclear cells suggests that Th-1 type cytokines are the mediators of RHD heart lesions while the presence of few interleukin-4 producing cells in the valve tissue contributes to the maintenance and progression of the valvular lesions.

Susceptibility to severe Streptococcal sepsis: use of a large set of isogenic mouse lines to study genetic and environmental factors

Variation in responses to pathogens is influenced by exposure history, environment and the host's genetic status. We recently demonstrated that human leukocyte antigen class II allelic differences are a major determinant of the severity of invasive group A streptococcal (GAS) sepsis in humans. While in-depth controlled molecular studies on populations of genetically well-characterized humans are not feasible, it is now possible to exploit genetically diverse panels of recombinant inbred BXD mice to define genetic and environmental risk factors. Our goal in this study was to standardize the model and identify genetic and nongenetic covariates influencing invasive infection outcomes. Despite having common ancestors, the various BXD strains (n strains=33, n individuals=445) showed marked differences in survival. Mice from all strains developed bacteremia but exhibited considerable differences in disease severity, bacterial dissemination and mortality rates. Bacteremia and survival showed the expected negative correlation. Among nongenetic factors, age -- but not sex or weight -- was a significant predictor of survival (P=0.0005). To minimize nongenetic variability, we limited further analyses to mice aged 40-120 days and calculated a corrected relative survival index that reflects the number of days an animal survived post-infection normalized to all significant covariates. Genetic background (strain) was the most significant factor determining susceptibility (P< or =0.0001), thus underscoring the strong effect of host genetic variation in determining susceptibility to severe GAS sepsis. This model offers powerful unbiased forward genetics to map specific quantitative trait loci and networks of pathways modulating the severity of GAS sepsis.

Comparative in silico analysis of two vaccine candidates for group A streptococcus predicts that they both may have similar safety profiles

BACKGROUND

Concerns of immune cross-reactivity, between epitopes of the group A streptococcal (GAS) M-proteins and host proteins have hindered the progress of an effective GAS vaccine. An ideal M-protein based subunit vaccine should not elicit heart tissue cross-reactive antibody responses and should not activate M-protein specific CD4+ T-cells. In the current study we used a bioinformatic and immunoinformatic approach to assess the safety of J8 and J14, chimeric vaccine constructs containing a GAS derived M-protein epitope embedded in flanking GCN4 region. We demonstrate that at the primary amino acid level J8 and J14 show very little homology to human proteins. ProPred, RANKPEP and HLABIND algorithms failed to predict significant binding between the M-protein specific regions of J8 and J14 and class II binding alleles. A single peptide was predicted to bind to HLA class I allele B_2705. This data was supported by cellular proliferation assays demonstrating few peripheral blood mononuclear cells (PBMCs) from donors respond to J8 and J14. Reassuringly, there was no correlation between proliferation to these peptides, and proliferation to host proteins. This data suggests that J8 and J14 are unlikely to induce cross-reactive immune responses, and will be safe for use in humans.

HLA Transgenic Mice Provide Evidence for a Direct and Dominant Role of HLA Class II Variation in Modulating the Severity of Streptococcal Sepsis

Our epidemiologic studies on invasive Group A Streptococci (GAS) infections identified specific HLA class II haplotypes/alleles conferring high-risk or protection from streptococcal toxic shock syndrome with a strong protection conferred by the DRB1*15/DQB1*06 haplotype. We used HLA-transgenic mice to provide an in vitro and in vivo validation for the direct role of HLA class II allelic variation in streptococcal toxic shock syndrome. When splenocytes from mice expressing the protective HLA-DQB1*06 (DQ6) allele were stimulated with a mixture of streptococcal superantigens (SAgs), secreted by the prevalent M1T1 strain, both proliferative and cytokine responses were significantly lower than those of splenocytes from mice expressing the neutral DRB1*0402/DQB1*0302 (DR4/DQ8) alleles (p < 0.001). In crisscross experiments, the presentation of SAgs to pure T cells from either the DQ6 or the DR4/DQ8 mice resulted in significantly different levels of response depending on the HLA type expressed on the APCs. Presentation by HLA-DQ6 APCs elicited significantly lower responses than the presentation by HLA-DR4/DQ8 APCs. Our in vitro data were supported by in vivo findings, as the DQ6 mice showed significantly longer survival post-i.v. infection with live M1T1 GAS (p < 0.001) and lower inflammatory cytokine responses as compared with the DR4/DQ8 mice (p < 0.01). The data presented here provide evidence for a direct role of HLA class II molecules in modulating responses to GAS SAgs and underscore the dominant role of HLA class II allelic variation in potentiating the severity of GAS systemic infections.

Genetic susceptibility to rheumatic heart disease and streptococcal pharyngitis: association with HLA-DR alleles

Acute rheumatic fever (ARF) is a systemic inflammatory disease that develops as a consequence of an exaggerated immune response to group A beta-haemolytic streptococci, which causes pharyngitis. Major manifestations of ARF include carditis, arthritis and chorea. Several investigators have attempted to establish a relation between ARF and human leucocyte antigens (HLA). Heterogeneity in various studies has been found, although associations with certain antigens were reported. The aim of this study was to analyse whether HLA-DR alleles play a role in the resistance or susceptibility to streptococci-related disorders including rheumatic heart disease (RHD) as a sequela of ARF and recurrent streptococcal pharyngitis in Turkish patients. The study included 102 patients with RHD, 71 persons with recurrent streptococcal pharyngitis and 130 healthy controls. HLA-DR alleles were typed by using polymerase chain reaction (PCR)-sequence-specific primers. Positive association with HLA-DRB1*07 allele was found for RHD when compared with healthy controls [29.4% vs 13.1%; P < 0.01, P-corrected: P < 0.01, odds ratio (OR) 2.78, 95% confidence interval (CI) 1.43-5.26] and also for recurrent streptococcal pharyngitis (26.8% vs 13.1%; P < 0.05, P-corrected: P < 0.05, OR 2.44, 95% CI 1.17-3.56). The frequency of HLA-DRB1*11 allele was decreased in patients with RHD (23.5% vs 42.3%; P < 0.01, P-corrected: P < 0.01, OR 0.42, 95% CI 0.24-0.75). Data suggest that HLA-DRB1*07 allele may be a genetic factor in increasing the susceptibility to develop RHD and recurrent streptococcal pharyngitis. HLA-DRB1*11 allele seems to be a protective factor against RHD.

Rheumatic fever: how S. pyogenes-primed peripheral T cells trigger heart valve lesions

The pathogenesis of rheumatic fever (RF) is related to autoimmune humoral and cellular responses against human tissues triggered by Streptococcus pyogenes. CD4(+) T cells are the ultimate effectors of chronic heart lesions in rheumatic heart disease (RHD). Heart-infiltrating CD4(+) T cell clones are able to recognize heart tissue and streptococcal antigens by molecular mimicry. The streptococcal M5(81-103) region, an immunodominant region, was recognized by both intralesional and peripheral T cell clones (62% and 38%, respectively). Peripheral T lymphocytes from Brazilian patients with severe RHD preferentially recognized the M5(81-96) peptide, in the context of HLA-DR7(+) and DR53(+) molecules. HLA-DR7 seems to be related to the development of multiple valvular lesions in RHD patients from different countries. In addition, the fact that peripheral and intralesional T cells recognized the M5(81-103) region points to this region as one of the streptococcal triggers of autoimmune reactions in RHD. T cell repertoire analysis from peripheral and intralesional T cell lines derived from RHD patients showed several oligoclonal expansions of BV families. Major expansions were found in the heart lesions, suggesting that such T cell populations preferentially migrate from the periphery to the heart. Some cross-reactive intralesional T cell clones displayed the same T cell receptor (TCR) BVBJ and CDR3 sequences, showing a degenerate pattern of antigen recognition. Heart tissue-infiltrating cells from myocardium and valvular tissue produced TNF-alpha, IFN-gamma, IL-10, and IL-4, whereas few cells from valvular tissue produced IL-4, showing that the lack of regulation in the valves could be responsible for the permanent and progressive valvular lesions.

B-cell antigen D8/17 is a marker of rheumatic fever susceptibility in Aboriginal Australians and can be tested in remote settings

OBJECTIVE

To test the B-cell antigen D8/17 as a marker of past rheumatic fever (RF) in a predominantly Aboriginal Australian population, and to evaluate technical modifications to allow its use in remote settings.

DESIGN AND SETTING

Cross-sectional survey in a remote Aboriginal community, a regional tertiary referral hospital and a tertiary paediatric centre in Melbourne.

PARTICIPANTS

106 people, including three with acute RF, 38 with a history of past RF, 20 relatives of these people, and 45 healthy controls.

MAIN OUTCOME MEASURE

D8/17 expression in B cells.

RESULTS

Blood was collected from each participant and the expression of D8/17 and CD19 in each sample was analysed by flow cytometry. The mean proportion of D8/17-positive B cells was 39.3% (SD, 11.8) in patients with previous RF, 22.5% (SD, 5.2) in first-degree relatives, 11.6% (SD, 7.2) in controls, and 83.7% (SD, 10.1) in patients with acute RF (analysis of variance test between means, P = 0.001). A cut-off of 22.1% of D8/17-positive B cells to indicate past RF yielded the highest percentage of correct results (95.4%). Delayed staining of whole blood (mean, 0.55 days; SD, 0.2) gave equivalent results to immediate staining, but the D8/17 assay on peripheral blood mononuclear cells was unreliable.

CONCLUSIONS

The B-cell antigen D8/17 accurately identifies Australians with a past history of RF, and the assay is feasible in remote settings with access to facilities capable of performing D8/17 staining within half a day of sample collection.

The role of HLA molecules in susceptibility to chronic rheumatic heart disease

Only a small fraction of the streptococcal pharyngitis progress to rheumatic carditis, which implies that environmental, host and microbial factors interact to cause an aberrant immune response against the antigens of the microorganism that cross-react with cardiac tissues. Although there are numerous studies and a general consensus on the relation between human leucocyte antigen (HLA) class II antigens and rheumatic heart disease (RHD), the details and the culprit antigens are still controversial. The study was undertaken to examine 100 patients with chronic RHD and 100 controls for HLA class I and class II antigens for differences in prevalence. All samples were typed at the HLA-DRB1/3/4/5 and DQB1 loci by the sequence-specific primer (PCR-SSP) method at low resolution. For HLA class I antigens, HLA-B13 frequency was marginally increased in patients with RHD compared to controls without reaching statistical significance. For class II antigens, RHD patients had higher frequencies for HLA-DRB1*01 (RHD 24%, controls 10%), DRB1*04 (RHD 35%, controls 26%), DRB1*07 (RHD 18%, controls 11%) and HLA-DQB1*02 (RHD 32%, controls 17%) without reaching statistical significance, and significantly lower frequencies for DRB1*13 (Pc < 0.003, OR: 5.69), DRB5* (Pc < 0.003, OR: 33) and DRB3* (Pc = 0.03, OR: 2.66) compared to controls. It was concluded that host, microbial and environmental factors collude to create acute rheumatic fever (RF) and chronic rheumatic valve disease. The HLA-DRB1*13, DRB5* and DRB3* were protective against the development of rheumatic valve damage.

T cell mimicry and epitope specificity of cross-reactive T cell clones from rheumatic heart disease

Mimicry between streptococcal M protein and cardiac myosin is important in the pathogenesis of rheumatic heart disease. M protein-specific human T cell clones derived from rheumatic carditis were cross-reactive with human cardiac myosin, and laminin, a valve protein. Among the 11 CD4(+) and CD8(+) cross-reactive T cell clones, at least 6 different reactivity patterns were distinguished, suggesting different degrees of cross-reactivity and a very diverse T cell repertoire. The latter was confirmed by a heterogeneous Vbeta gene and CDR3 usage. HLA restriction and Th1 cytokine production in response to rM6 protein were preserved when the T cell clones were stimulated by human cardiac myosin or other alpha-helical proteins, such as tropomyosin and laminin. The cross-reactive human T cell clones proliferated to B2 and B3A, dominant peptide epitopes in the B repeat region of streptococcal M protein. In human cardiac myosin, epitopes were demonstrated in the S2 and light meromyosin regions. In our study, T cell mimicry was defined as recognition of structurally related Ags involved in disease and recognized by the same T cell. Mimicry in our study was related to alpha-helical coiled coil proteins which have a repetitive seven-aa residue periodicity that maintains alpha-helical structure and thus creates a high number of degenerate possibilities for recognition by T cells. The study of human T cell clones from rheumatic heart disease revealed potential sites of T cell mimicry between streptococcal M protein and human cardiac myosin and represents some of the most well-defined T cell mimicry in human autoimmune disease.

Prospects for a group A streptococcal vaccine: rationale, feasibility, and obstacles--report of a National Institute of Allergy and Infectious Diseases workshop

Infections due to group A streptococci (GAS) represent a public health problem of major proportions in both developing and developed countries. Currently available methods of prevention are either inadequate or ineffective, as attested to by the morbidity and mortality associated with this ubiquitous pathogen worldwide. Advances in molecular biology have shed new light on the pathogenesis of GAS infections and have identified a number of virulence factors as potential vaccine targets. Therefore, the National Institute of Allergy and Infectious Diseases convened an expert workshop in March 2004 to review the available data and to explore the microbiologic, immunologic, epidemiologic, and economic issues involved in development and implementation of a safe and effective GAS vaccine. Participants included scientists and clinicians involved in GAS research, as well as representatives of United States federal agencies (Centers for Disease Control and Prevention, Food and Drug Administration, Department of Defense, and National Institute of Allergy and Infectious Diseases), the World Health Organization, and the pharmaceutical industry. This report summarizes the deliberations of the workshop.

Acute rheumatic fever

Acute rheumatic fever (ARF) and its chronic sequela, rheumatic heart disease (RHD), have become rare in most affluent populations, but remain unchecked in developing countries and in some poor, mainly indigenous populations in wealthy countries. More than a century of research, mainly in North America and Europe, has improved our understanding of ARF and RHD. However, whether traditional views need to be updated in view of the epidemiological shift of the past 50 years is still to be established, and improved data from developing countries are needed. Doctors who work in populations with a high incidence of ARF are adapting existing diagnostic guidelines to increase their sensitivity. Group A streptococcal vaccines are still years away from being available and, even if the obstacles of serotype coverage and safety can be overcome, their cost could make them inaccessible to the populations that need them most. New approaches to primary prevention are needed given the limitations of primary prophylaxis as a population-based strategy. The most effective approach for control of ARF and RHD is secondary prophylaxis, which is best delivered as part of a coordinated control programme.