Natkunam Ketheesan

Mass vaccination with attenuated infectious laryngotracheitis virus (ILTV) via drinking water is commonly used in commercial chicken farms, although the effectiveness of oral (OR) vaccination is lower than eye drop (ED). The gene expression of a select set of immune markers associated with inflammatory responses (TLR4, TLR7, TLR2-2, IL6, CCL4, CCR5, IFNγ, IL2, IL17C), immune synapse (CD80), T helper cell polarisation (IL4) and effector cell receptors (CD4, CD8α and CD14), following OR and ED primary vaccination and revaccination using the same or alternate route [ED/ED (primary/revaccination), OR/OR, ED/OR and OR/ED] with ILTV SA2 strain in chickens were evaluated. Both ED and OR primary vaccinations were associated with increased gene expression of inflammation-associated markers in the conjunctiva and trachea, with a statistical interaction between application route and profile of immune responses. Revaccination via the alternative route elicited upregulation of more immune markers in the conjunctiva and trachea compared to other methods, while most immune markers were downregulated in the ED/ED group, and close to baseline in the OR/OR group. In conclusion, the immune responses in the conjunctiva and trachea following the ED and OR primary vaccination with ILTV vaccine were tissue-specific, showing increased gene expression of markers related to the inflammatory response. Revaccination using the alternative route elicited upregulation of markers associated with inflammatory responses CCR5 and TLR7 in the conjunctiva and/or trachea. Challenge studies are necessary to confirm the role of these immune responses in protecting vaccinated birds from ILTV.

Acute Rheumatic Fever and Rheumatic Heart Disease (ARF/RHD) affect over 45 million people globally. ARF/RHD are autoimmune complications following group A streptococcal infections. Current diagnosis of ARF requires thorough medical examination, echocardiography and laboratory tests that are unavailable in most primary care settings where patients with ARF typically first present. This pilot study was conducted to determine whether machine learning-based predictive models could be used to stratify host tissue protein reactive antibodies associated with ARF, that could be incorporated into a lateral flow point-of-care (POC) platform for ARF screening. We investigated serum antibody levels against four host tissue proteins (cardiac myosin, laminin, keratin, and tropomyosin) known to increase in ARF. Serum samples were obtained from: (i) a rat autoimmune valvulitis model (RAV) of RHD (30 streptococcal M protein-injected rats versus 30 controls); and (ii) human samples (25 newly diagnosed ARF patients versus 50 healthy controls). Four machine learning algorithms (logistic regression, decision tree, random forest, and AdaBoost) predicted ARF status using antibody levels detected by enzyme-linked immunosorbent assay (ELISA). Rats injected with streptococcal M protein developed cardiac pathology and demonstrated three-fold higher optical density values for all four host tissue protein reactive antibodies compared to controls. ARF patients showed significantly elevated antibody levels against all host tissue proteins tested (p < 0.01). Random forest achieved optimal performance for rat data (sensitivity 100%, specificity 92.5%, AUROC = 0.97), while AdaBoost excelled for human samples using binary biomarkers (sensitivity 85.0%, specificity 82.8%, AUROC = 0.87). We demonstrate the screening potential of known host tissue protein reactive antibodies and propose lateral flow assay POC technology as a possible advancement toward improved early screening for ARF in resource-constrained environments.

Acute rheumatic fever is an autoimmune inflammatory reaction to Streptococcus pyogenes infections, leading to progressive heart valve damage and rheumatic heart disease (RHD)

A rapid and cost‐effective arm of the drug discovery and development process is finding new uses for existing drugs. Initially used as antibacterial agents, sulphonylureas were repurposed for the treatment of type 2 diabetes due to their hypoglycemic side effects. Their primary mechanism of action is mediated by binding to sulphonylurea receptors (SUR), which are atypical adenosine triphosphate binding cassette transporters in pancreatic beta cells. This interaction inhibits ATP‐sensitive potassium channels to promote insulin release. Off‐target actions of sulphonylureas identified in recent studies have demonstrated a range of anti‐inflammatory properties mediated by modulation of the nucleotide‐binding oligomerization domain‐like receptor pyrin domain‐containing protein 3 inflammasomes. Inflammasomes are cytosolic protein complexes that assemble in response to infection or stress‐associated stimuli, activating inflammatory responses, and are the primary source of pro‐inflammatory cytokines. Sulphonylureas and their derivatives have been shown to inhibit various stages of inflammasome activation, leading to the reduction of pro‐inflammatory mediators, including IL‐1β and IL‐18. Recent evidence demonstrates that these agents reduced inflammatory responses, disease severity, and progression in various preclinical autoimmune and inflammatory models. In this narrative review, we consider the complexity of autoimmune conditions and the limited treatment options, and highlight the potential value of repurposing sulphonylureas and their derivatives as adjunct therapeutics for autoimmune conditions.

Aim: Acute rheumatic fever (ARF) and Rheumatic heart disease (RHD) are autoimmune sequalae, that develops in a proportion of individuals exposed to group A streptococcal infection. The autoimmune pathology of ARF/RHD is multifactorial. Both host and pathogen‐associated factors including genetic predisposition, inflammatory responses, tissue cross‐reactive antibodies and T‐cells contribute to disease development and progression. Hitherto, the role of inflammatory responses in ARF/RHD has never been demonstrated in animal models. In this study for the first time, using the Rat Autoimmune valvulitis model of RHD, we demonstrate the requirement for inflammatory responses in promoting cardiac damage in ARF/RHD.Methods: To determine the role of inflammatory responses we used Bordetella pertussis toxin (BPTx) as an adjuvant to enhance the inflammatory responses initiated by GAS M protein.Results: Lewis rats injected with GAS rM5 emulsified in Complete Freund's Adjuvant (CFA) and co‐adjuvant BPTx, had enhanced valvulitis and inflammatory changes as shown by; (a) elevated levels of circulating inflammatory cytokines; (b) functional changes characterized by a prolonged P‐R interval in electrocardiography, (c) enhanced cross‐reactive antibody production against cardiac and connective tissue proteins; and (d) increased infiltration of IFN‐γ+ and IL‐17A+ secreting leukocytes into myocardium and valvular tissues.Conclusion: These studies have established that in addition to exposure to GAS M protein, BPTx accelerate the inflammatory and autoimmune processes leading to cardiac damage. These observations substantiate the hypothesis that, in susceptible individuals robust inflammatory responses facilitate the progression of ARF/RHD.

Acute rheumatic fever (ARF) is an autoimmune disease triggered by antibodies and T cells targeting the group A Streptococcus (GAS, Strep A) bacterium, often leading to rheumatic heart disease (RHD) and Sydenham’s chorea. Long-term monthly penicillin injections are recognized as a cornerstone of public health programs to prevent Strep A reinfection and progression of ARF. However, compliance is poor, and better tools are required to slow disease progression. Preclinical evidence suggests that this can be achieved. Using a rat model that replicates post-streptococcal autoimmune complications, we explored the potential of low-dose interleukin-2 (LD-IL-2) as an immunotherapeutic intervention for ARF/RHD. In this model, injections of recombinant M protein from Strep A type 5 (rM5) to Lewis rats induce cardiac tissue inflammation, conduction abnormalities, and cross-reactive antibodies against cardiac and brain proteins central to disease pathogenesis. In animals injected with rM5 and treated with LD-IL-2, no cardiac functional or histological changes was observed. LD-IL-2 therapy effectively reduced the production of cross-reactive antibodies raised against host proteins and significantly increased regulatory T cells in the mediastinal lymph nodes. These novel findings suggest that LD-IL-2 will be an effective immunotherapeutic agent for treating ARF and has the potential to replace the standard monthly penicillin injections. IMPORTANCE: Post-streptococcal autoimmune syndromes, including acute rheumatic fever, rheumatic heart disease, and Sydenham’s chorea, represent a significant yet often under-recognized health and economic burden. This is especially true in low-income countries and among Indigenous populations in high-income nations, where the disease burden is most severe. These conditions arise from an autoimmune response to group A Streptococcus infections, leading to long-term health complications, disability, and premature death. Despite their widespread impact, no vaccine is currently available to prevent reinfections, and no specific therapy exists to treat the resulting autoimmune process. This study uses a rat model of rheumatic heart disease to evaluate the potential of low-dose interleukin 2 therapy in improving clinical outcomes and reducing the incidence of autoimmune diseases triggered by streptococcal infections.

Sydenham chorea (SC) is the neurological manifestation associated with acute rheumatic fever (ARF). ARF and rheumatic heart disease (RHD) are autoimmune complications triggered by a group A streptococcal (GAS) infection. In ARF/RHD and SC, tissue cross‐reactive antibodies and T‐cells generated against GAS antigens have been implicated in the pathogenesis. In SC, antibodies against GAS antigens are known to cross‐react with neuronal proteins causing neurological manifestations including choreiform movements and neuropsychiatric symptoms such as irritability, attention deficit, and obsessive‐compulsive disorder. Previous studies in a rat autoimmune valvulitis (RAV) model of RHD, have shown that injection of streptococcal M protein could cause both cardiac and neurological symptoms. In this study it was shown that adoptive transfer of serum with anti‐GAS M antibodies to naive rats caused carditis but failed to demonstrate neurobehavioral symptoms. However, when the blood–brain barrier (BBB) was disrupted using lipopolysaccharide, all animals that received anti‐GAS M protein antibodies, developed neurobehavioral defects in addition to carditis. This highlights that impaired BBB integrity is essential for the development of neurobehavioral symptoms. The use of the RAV model and the disruption of BBB required for the development of neurobehavioral changes provides a platform to further investigate the mechanisms that lead to antibodies binding to basal ganglia structures that cause SC.

Acute rheumatic fever (ARF) is an autoimmune disease triggered by antibodies and T-cells targeting the Group A streptococcal (GAS, Strep A) bacterium, often leading to rheumatic heart disease (RHD). Long-term antibiotic therapy is recognized as a cornerstone of public health programs to prevent reinfection and progression of ARF. However, better tools to slow disease progression, and mitigate its lifelong consequences are required. Evidence obtained in a preclinical model suggests that this can be achieved. Using the rat autoimmune valvulitis model, we explored the potential of low-dose interleukin 2 (LD-IL-2) as an immunotherapeutic intervention. In this model injection of recombinant Strep A M5 protein (rM5) to Lewis rats induce autoimmune complications, cardiac tissue inflammation and conduction abnormalities. In animals injected with rM5 and treated with LD-IL-2, no cardiac functional or histological changes were observed. LD-IL-2 therapy effectively reduced the production of cross-reactive antibodies against cardiac tissue and induced a significant increase in classical regulatory T-cells (Treg) and CD8 ⁺ Tregs in the mediastinal (heart-draining) lymph nodes. These novel findings suggest LD-IL-2 will be an effective immunotherapeutic agent for treating ARF/RHD.

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) are autoimmune conditions triggered by Group A Streptococcus skin or throat infections. If ARF/RHD is undetected, misdiagnosed or antibiotic treatment is not provided early, patients may develop cardiac failure, leading to premature death. Although it is an easily preventable disease, ARF/RHD remains the most significant cause of heart disease-associated deaths in people under 25 years old, both in low- and middle-income countries and among First Nations in high-income countries. Up to 30% of the patients with ARF/RHD present with a neurobehavioral condition – Sydenham’s chorea (SC). The clinical course of SC is mostly self-limiting and is characterized by the onset of involuntary choreiform movements and neuropsychiatric features such as obsessive-compulsive disorder, tics, depression and anxiety, psychosis, and attention-deficit hyperactivity disorder. While the precise mechanism as to why only a proportion of patients with ARF/RHD develop SC remains unknown, an impaired blood–brain barrier is considered to play a central role in its development. The most well-characterized neurobehavioral outcome is stroke which may occur in isolation or as part of systemic thromboembolism. Both infective endocarditis and mitral valve disease with or without aortic valve disease increase the embolic and ischemic stroke risk. ARF/RHD is known to significantly impact the quality of life with neuropsychiatric consequences. Another neurobehavioral syndrome which occurs in the absence of ARF/RHD is “pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections” (PANDAS). PANDAS has been categorized as a subset of pediatric acute-onset neuropsychiatric syndromes. However, establishing a diagnosis of PANDAS has been challenging. In this review, we discuss the current status of our understanding regarding the different manifestations of poststreptococcal neurobehavioral changes. Particular attention is given to ARF/RHD-associated SC, and we highlight the areas for further research to understand the association between poststreptococcal sequelae and neurobehavioral abnormalities.

Post-streptococcal glomerulonephritis (PSGN) is primarily associated with preceding Group A streptococcal skin or throat infections, now mainly observed in economically disadvantaged communities. This condition significantly predisposes individuals to later-life chronic kidney disease and concurrent renal complications, with the elderly experiencing increased severity and less favourable outcomes. Streptococcal pyrogenic exotoxin B and nephritis associated plasmin receptor are identified nephritogenic antigens (nephritogens). Pathogenesis of PSGN is multifactorial. It can involve the formation of antigen-antibody immune complexes, causing inflammatory damage to renal glomeruli. Deposition of circulating immune complexes or in situ formation of immune complexes in glomeruli, or both, results in glomerulonephritis. Additionally, molecular mimicry is hypothesised as a mechanism, wherein cross-reactivity between anti-streptococcal antibodies and glomerular intrinsic matrix proteins leads to glomerulonephritis. Besides, as observed in clinical studies, streptococcal inhibitor of complement, a streptococcal-secreted protein, can also be associated with PSGN. However, the interplay between these streptococcal antigens in the pathogenesis of PSGN necessitates further investigation. Despite the clinical significance of PSGN, the lack of credible animal models poses challenges in understanding the association between streptococcal antigens and the disease process. This review outlines the postulated mechanisms implicated in the development of PSGN with possible therapeutic approaches.