Repeat exposure to group A streptococcal M protein exacerbates cardiac damage in a rat model of rheumatic heart disease

Research opportunities for the primordial prevention of rheumatic fever and rheumatic heart disease-streptococcal vaccine development: a national heart, lung and blood institute workshop report

Streptococcus pyogenes, also known as group A streptococcus (StrepA), is a bacterium that causes a range of human diseases, including pharyngitis, impetigo, invasive infections, and post-infection immune sequelae such as rheumatic fever and rheumatic heart disease. StrepA infections cause some of the highest burden of disease and death in mostly young populations in low-resource settings. Despite decades of effort, there is still no licensed StrepA vaccine, which if developed, could be a cost-effective way to reduce the incidence of disease. Several challenges, including technical and regulatory hurdles, safety concerns and a lack of investment have hindered StrepA vaccine development. Barriers to developing a StrepA vaccine must be overcome in the future by prioritising key areas of research including greater understanding of StrepA immunobiology and autoimmunity risk, better animal models that mimic human disease, expanding the StrepA vaccine pipeline and supporting vaccine clinical trials. The development of a StrepA vaccine is a complex and challenging process that requires significant resources and investment. Given the global burden of StrepA infections and the potential for a vaccine to save lives and livelihoods, StrepA vaccine development is an area of research that deserves considerable support. This report summarises the findings of the Primordial Prevention Working Group-VAX, which was convened in November 2021 by the National Heart, Lung, and Blood Institute. The focus of this report is to identify research gaps within the current StrepA vaccine landscape and find opportunities and develop priorities to promote the rapid and successful advancement of StrepA vaccines.

Immune tolerance breakdown in inborn errors of immunity: Paving the way to novel therapeutic approaches

Up to 25% of the patients with inborn errors of immunity (IEI) also exhibit immunodysregulatory features. The association of immune dysregulation and immunodeficiency may be explained by different mechanisms. The understanding of mechanisms underlying immune dysregulation in IEI has paved the way for the development of targeted treatments. In this review article, we will summarize the mechanisms of immune tolerance breakdown and the targeted therapeutic approaches to immune dysregulation in IEI.

Streptococcus pyogenes vaccine candidates do not induce autoimmune responses in a rheumatic heart disease model

We have developed a candidate vaccine to protect against multiple strains of Streptococcus pyogenes infections. The candidate vaccine contains two synthetic peptides derived from S. pyogenes proteins: the M-protein epitope, p*17 and the IL-8 degrading S. pyogenes Cell-Envelope Proteinase (SpyCEP) epitope, K4S2. In this study we utilise a rat autoimmune valvulitis model that displays both the cardiac and neurobehavioural pathology associated with post-streptococcal sequelae, to assess if the vaccine candidate antigens induce autoimmune complications and inflammatory pathology. Each antigen was conjugated to carrier protein diphtheria toxoid (DT) and independently assessed for potential to induce autoimmune pathology in female Lewis rats. Rats were administered three subcutaneous doses, and one intranasal dose over a four-week study with a two-week recovery period. A positive control group received recombinant S. pyogenes M5 (rM5) protein, and the negative control group received PBS. Rats that received rM5 developed significant cardiac and neurological pathologies. There was no evidence of these pathologies in the PBS control group, or the rats administered either P*17-DT or K4S2-DT. This study provides further preclinical evidence of the safety of the vaccine candidates p*17 and K4S2 and their appropriateness as candidates in human clinical trials.

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.

Recent Advances in the Rheumatic Fever and Rheumatic Heart Disease Continuum

Nearly a century after rheumatic fever (RF) and rheumatic heart disease (RHD) was eradicated from the developed world, the disease remains endemic in many low- and middle-income countries (LMICs), with grim health and socioeconomic impacts. The neglect of RHD which persisted for a semi-centennial was further driven by competing infectious diseases, particularly the human immunodeficiency virus (HIV) pandemic. However, over the last two-decades, slowly at first but with building momentum, there has been a resurgence of interest in RF/RHD. In this narrative review, we present the advances that have been made in the RF/RHD continuum over the past two decades since the re-awakening of interest, with a more concise focus on the last decade’s achievements. Such primary advances include understanding the genetic predisposition to RHD, group A Streptococcus (GAS) vaccine development, and improved diagnostic strategies for GAS pharyngitis. Echocardiographic screening for RHD has been a major advance which has unearthed the prevailing high burden of RHD and the recent demonstration of benefit of secondary antibiotic prophylaxis on halting progression of latent RHD is a major step forward. Multiple befitting advances in tertiary management of RHD have also been realized. Finally, we summarize the research gaps and provide illumination on profitable future directions towards global eradication of RHD.

IL-33/ST2 Axis Plays a Protective Effect in Streptococcus pyogenes Infection through Strengthening of the Innate Immunity

Group A Streptococcus (GAS) causes invasive human diseases with the cytokine storm. Interleukin-33 (IL-33)/suppression of tumorigenicity 2 (ST2) axis is known to drive TH2 response, while its effect on GAS infection is unclear. We used an air pouch model to examine the effect of the IL-33/ST2 axis on GAS-induced necrotizing fasciitis. GAS infection induced IL-33 expression in wild-type (WT) C57BL/6 mice, whereas the IL-33- and ST2-knockout mice had higher mortality rates, more severe skin lesions and higher bacterial loads in the air pouches than those of WT mice after infection. Surveys of infiltrating cells in the air pouch of GAS-infected mice at the early stage found that the number and cell viability of infiltrating cells in both gene knockout mice were lower than those of WT mice. The predominant effector cells in GAS-infected air pouches were neutrophils. Absence of the IL-33/ST2 axis enhanced the expression of inflammatory cytokines, but not TH1 or TH2 cytokines, in the air pouch after infection. Using in vitro assays, we found that the IL-33/ST2 axis not only enhanced neutrophil migration but also strengthened the bactericidal activity of both sera and neutrophils. These results suggest that the IL-33/ST2 axis provided the protective effect on GAS infection through enhancing the innate immunity.

Group A streptococcal antigen exposed rat model to investigate neurobehavioral and cardiac complications associated with post-streptococcal autoimmune sequelae

Background

The neuropsychiatric disorders due to post-streptococcal autoimmune complications such as Sydenham's chorea (SC) are associated with acute rheumatic fever and rheumatic heart disease (ARF/RHD). An animal model that exhibits characteristics of both cardiac and neurobehavioral defects in ARF/RHD would be an important adjunct for future studies. Since age, gender, strain differences, and genotypes impact on the development of autoimmunity, we investigated the behavior of male and female Wistar and Lewis rat strains in two age cohorts (<6 weeks and >12 weeks) under normal husbandry conditions and following exposure to group A streptococcus (GAS).

Methods

Standard behavioral assessments were performed to determine the impairments in fine motor control (food manipulation test), gait and balance (beam walking test), and obsessive-compulsive behavior (grooming and marble burying tests). Furthermore, electrocardiography, histology, and behavioral assessments were performed on male and female Lewis rats injected with GAS antigens.

Results

For control Lewis rats there were no significant age and gender dependent differences in marble burying, food manipulation, beam walking and grooming behaviors. In contrast significant age-dependent differences were observed in Wistar rats in all the behavioral tests except for food manipulation. Therefore, Lewis rats were selected for further experiments to determine the effect of GAS. After exposure to GAS, Lewis rats demonstrated neurobehavioral abnormalities and cardiac pathology akin to SC and ARF/RHD, respectively.

Conclusion

We have characterised a new model that provides longitudinal stability of age-dependent behavior, to simultaneously investigate both neurobehavioral and cardiac abnormalities associated with post-streptococcal complications.

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.

Rheumatic Heart Valve Disease Pathophysiology and Underlying Mechanisms

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

Coexistence of acute poststreptococcal glomerulonephritis and acute rheumatic fever in a Japanese girl with primary Sjögren's syndrome

Although acute poststreptococcal glomerulonephritis (APSGN) and acute rheumatic fever (ARF) are well-known complications of group A streptococcus infection, concomitant occurrence of both diseases is rare. We report an 11-year-old Japanese girl with primary Sjögren's syndrome complicated by acute renal failure about 2 weeks after the onset of pharyngitis. Although histopathological findings of the kidney were not confirmative, APSGN was suggested by the spontaneous recovery of her renal function, typical latent period with high levels of antistreptolysin O and low serum levels of C3 but not of C4. In addition, cardiac hypomotility and regurgitation of the 4 valves progressed in the convalescent phase of APSGN, which was accompanied by elevation of serum C-reactive protein and plasma brain natriuretic peptide (BNP) levels. Myocarditis was suggested by delayed gadolinium-enhancement of cardiac walls on cardiac magnetic resonance imaging. She was diagnosed with APSGN and ARF and was treated with a combination of short course prednisolone and prophylactic penicillin G. There is no relapse of renal or cardiac symptoms during 6 years follow-up. Unexpected elevation of plasma BNP in a convalescent stage of APSGN suggests the development of ARF. Underlying Sjögren's syndrome (SS) may modify the histopathological findings and make it difficult to differentiate APSGN from CTD-associated nephritis such as lupus nephritis (LN) even by renal biopsy.

Anti-streptococcal antibody and T-cell interactions with vascular endothelial cells initiate the development of rheumatic carditis

The role of group A streptococcal and Streptococcus dysgalactiae subspecies equisimilis M-protein specific Abs and T-cells in endothelial cell activation was investigated using cultured rat aortic endothelial cells, and in a rat model of autoimmune valvulitis. Heat inactivated serum and mononuclear cells from streptococcal M-protein immunized rats independently induced upregulation of the endothelial cell adhesion molecules, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 in cultured cells. We also observed T-cell migration across endothelial cell monolayers incubated with serum from M-protein-immunized rats. Furthermore, we observed VCAM-1 and ICAM-1 expression in the myocardium of rats injected with M-protein compared to control animals. These observations support the contention that initial interactions between streptococcal M-protein specific Abs and/or T-cells with the heart endothelium lead to endothelial cell activation followed by transmigration of M-protein specific T-cells into heart tissue leading to an inflammatory process that leads to carditis in rheumatic fever and rheumatic heart disease.

Scolopendra subspinipes mutilans L. Koch Ameliorates Rheumatic Heart Disease by Affecting Relative Percentages of CD4+CD25+FoxP3 Treg and CD4+IL17 T Cells

(Scolopendra subspinipes mutilans L. Koch. (SSLK) helps reduce the risk of coronary heart disease (CHD) but its effects on rheumatic heart disease (RHD) patients remain unclear. 80 RHD patients were recruited and randomly assigned into SG (to receive SSLK treatment) and CG (to receive placebo) groups, and the intervention lasted for 3 months. The following cardiac indexes were measured, including mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), blood lactate, fatigue, shortness of breath, palpitation, and chest pain. ELISA kits were used to analyze creatine kinase isoenzyme (CK-MB), serum troponin T (cTnT), CRP, IL-1β, IL-6, and TNF-α, malondialdehyde (MDA), and superoxide dismutase (SOD). Relative percentages of CD4⁺CD25⁺FoxP3 regulatory (Treg) and CD4⁺IL-17 T cells were measured using flow cytometry. After 3-month therapy, SSLK intervention improved MAP, HR, CVP, fatigue, palpitation, and shortness breath of CHD patients, reduced the levels of blood lactate, CK-MB, cTnT, CRP, IL-1β, IL-6, TNF-α, MDA, and increased SOD level (p < 0.05). Meanwhile, SSLK treatment increased the percentages of CD4⁺CD25⁺FoxP3 Treg cells and reduced relative percentages of CD4⁺IL-17 T cells in a dose-dependent way (p < 0.05). Relative percentage of CD4⁺CD25⁺FoxP3 Treg cells had negative relationship while CD4⁺IL17 T cells had positive relationship with CK-MB, cTnT, CRP, and TNF-a (p < 0.01). SSLK ameliorated RHD by affecting the balance of CD4⁺CD25⁺FoxP3 Treg and CD4⁺IL17 T cells.

Molecular Mimicry, Autoimmunity, and Infection: The Cross-Reactive Antigens of Group A Streptococci and their Sequelae

The group A streptococci are associated with a group of diseases affecting the heart, brain, and joints that are collectively referred to as acute rheumatic fever. The streptococcal immune-mediated sequelae, including acute rheumatic fever, are due to antibody and cellular immune responses that target antigens in the heart and brain as well as the group A streptococcal cross-reactive antigens as reviewed in this article. The pathogenesis of acute rheumatic fever, rheumatic heart disease, Sydenham chorea, and other autoimmune sequelae is related to autoantibodies that are characteristic of autoimmune diseases and result from the immune responses against group A streptococcal infection by the host. The sharing of host and streptococcal epitopes leads to molecular mimicry between the streptococcal and host antigens that are recognized by the autoantibodies during the host response. This article elaborates on the discoveries that led to a better understanding of the pathogenesis of disease and provides an overview of the history and the most current thought about the immune responses against the host and streptococcal cross-reactive antigens in group A streptococcal sequelae.

Group A streptococcal M-protein specific antibodies and T-cells drive the pathology observed in the rat autoimmune valvulitis model

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) are autoimmune mediated diseases triggered by group A streptococcal (GAS) infections. Molecular mimicry between GAS M-proteins and host tissue proteins has been proposed as the mechanism that initiates autoreactive immune responses in ARF/RHD. However, the individual role of antibodies and T-cells specific for GAS M-proteins in the pathogenesis of autoimmune carditis remains under-explored. The current study investigated the role of antibodies and T-cells in the development of carditis in the Lewis rat autoimmune valvultis (RAV) model by transferring serum and/or splenic T-cells from rats previously injected with GAS recombinant M5 protein. Here we report that serum antibodies alone and serum plus in vitro expanded rM5-specific T-cells from hyperimmune rats were capable of transferring carditis to naïve syngeneic animals. Moreover, the rats that received combined serum and T-cells developed more severe carditis. Recipient rats developed mitral valvulitis and myocarditis and showed prolongation of P-R intervals in electrocardiography. GAS M5 protein-specific IgG reactivity and T-cell recall response were also demonstrated in recipient rats indicating long-term persistence of antibodies and T-cells following transfer. The results suggest that both anti-GAS M5 antibodies and T-cells have differential propensity to induce autoimmune mediated carditis in syngeneic rats following transfer. The results highlight that antibodies and effector T-cells generated by GAS M protein injection can also independently home into cardiac tissue to cross-react with tissue proteins causing autoimmune mediated immunopathology.

Rheumatic heart disease in the modern era: recent developments and current challenges

Rheumatic heart disease (RHD) remains a major cause of preventable death and disability in children and young adults. Despite significant advances in medical technology and increased understanding of disease mechanisms, RHD continues to be a serious public health problem throughout the world, especially in low- and middle-income countries. Echocardiographic screening has played a key role in improving the accuracy of diagnosing RHD and has highlighted the disease burden. Most affected patients present with severe valve disease and limited access to life-saving cardiac surgery or percutaneous valve intervention, contributing to increased mortality and other complications. Although understanding of disease pathogenesis has advanced in recent years, key questions remain to be addressed. Preventing or providing early treatment for streptococcal infections is the most important step in reducing the burden of this disease.

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.

Focus on Cardiologic Findings in 30 Children With PANS/PANDAS: An Italian Single-Center Observational Study

Objective: Cardiac involvement in PANS has not been clarified relying on the scientific literature available until today. It is known that streptococcal infections play a role in the etiology of a great number of diseases including Sydenham chorea and rheumatic fever, among others. Based on the suspected pathogenesis of PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections) reported in the medical literature, we decided to investigate the cardiologic involvement in children with a recent PANS/PANDAS diagnosis. Methods: The study population satisfies PANS (1) and PANDAS (2) criteria of diagnoses. Cardiologic assessment was performed through clinical examination, electrocardiography, and echocardiography. Results: In the selected pediatric population, a significant number of children presented mitral valve involvement, systolic murmurs and electrocardiographic abnormalities. High ASLOT levels did not seem to be associated to a cardiac involvement. Conclusions: Often PANS is difficult to diagnose because it is little known by physicians and most of the cardiologic findings described in this study are common among the healthy pediatric population. Also, ASLOT levels seems not to be predictive of cardiac involvement. Furthermore, the existence of PANDAS as a clinical entity is associated with a group of anti-neuronal autoantibodies found in Sydenham chorea is still controversial. We recommend a complete cardiologic evaluation in those children who meet the PANS/PANDAS diagnostic criteria.

Psoriasis patients demonstrate HLA-Cw*06:02 allele dosage-dependent T cell proliferation when treated with hair follicle-derived keratin 17 protein

It is broadly accepted that psoriasis is an immune-mediated disease with a heritable component, but it is not clear what causes inflammation in the skin. Previous research suggests that fragments of the keratin 17 (K17) protein, which are constitutively expressed in hair follicles, could act as autoantigens. In this study, we synthesized the K17 protein from mRNA derived from hair follicles and tested whether it elicited T cell responses depending on the patient genotype at the major susceptibility locus HLA-Cw*06:02. We treated peripheral blood-derived cells with the K17 protein and its short fragments to assess the T cell proliferation response using flow cytometry. Our analyses show a significantly stronger increase in cell proliferation among patients but not in healthy controls. We then examined whether the variation in T cell proliferation correlated with the patient HLA-Cw*06:02 risk genotype. Considering the affected status and patient genotype as two independent predictors, we fitted a linear model and showed that the HLA-Cw*06:02 allele dosage strongly predicted the T cell response. Our study findings suggest that the K17 protein likely acts as an autoantigen in psoriasis and that patients’ risk genotype is strongly correlated with the magnitude of the response to this putative autoantigen.

Immunization of BALB/c mice with pigeon IgY induces the production of anti-IgG autoantibodies

The breakdown of immunological tolerance due to the activation of autoreactive B and T cells triggers physiopathological processes. An example of such conditions is the production of IgG autoantibodies specific for the Fc portion of IgG (anti-Fcγ IgG). Previous reports have shown that patients with pigeon-related hypersensitivity pneumonitis exhibit an increase in the serum levels of anti-Fcγ IgG. There is no in vivo model for the study of this condition and the immunological mechanisms of tolerance breakdown associated with sensitization by pigeon antigens are still unknown. In this work, we show that the repeated immunization of BALB/c mice with pigeon IgY during 16-weeks induces the production of anti-Fcγ IgG and keeps their high levels for seven weeks. The late appearance of anti-Fcγ IgG autoantibodies in the plasma is similar to what has been reported in other experimental autoimmune models. With the occurrence of anti-Fcγ IgG, there is a reduction in the proportion of Foxp3 + cells (regulatory T cells, Tregs) within the population of splenic CD4 + CD25 + T cells. Thus, our data showed that the immunization of BALB/c mice with IgY promotes the production of anti-Fcγ IgG along with a decrease in Tregs in the spleen. We propose that immunization of mice with pigeon antigens, like IgY can provide a model to study the immunological mechanisms involved in the development of pigeon-related hypersensitivity pneumonitis.

Immunization with a streptococcal multiple-epitope recombinant protein protects mice against invasive group A streptococcal infection

Streptococcus pyogenes (group A Streptococcus; GAS) causes clinical diseases, including pharyngitis, scarlet fever, impetigo, necrotizing fasciitis and streptococcal toxic shock syndrome. A number of group A streptococcus vaccine candidates have been developed, but only one 26-valent recombinant M protein vaccine has entered clinical trials. Differing from the design of a 26-valent recombinant M protein vaccine, we provide here a vaccination using the polyvalence epitope recombinant FSBM protein (rFSBM), which contains four different epitopes, including the fibronectin-binding repeats domain of streptococcal fibronectin binding protein Sfb1, the C-terminal immunogenic segment of streptolysin S, the C3-binding motif of streptococcal pyrogenic exotoxin B, and the C-terminal conserved segment of M protein. Vaccination with the rFSBM protein successfully prevented mortality and skin lesions caused by several emm strains of GAS infection. Anti-FSBM antibodies collected from the rFSBM-immunized mice were able to opsonize at least six emm strains and can neutralize the hemolytic activity of streptolysin S. Furthermore, the internalization of GAS into nonphagocytic cells is also reduced by anti-FSBM serum. These findings suggest that rFSBM can be applied as a vaccine candidate to prevent different emm strains of GAS infection.