Mapping Autoantibodies in Children With Acute Rheumatic Fever.

Background: Acute rheumatic fever (ARF) is a serious sequela of Group A Streptococcus (GAS) infection associated with significant global mortality. Pathogenesis remains poorly understood, with the current prevailing hypothesis based on molecular mimicry and the notion that antibodies generated in response to GAS infection cross-react with cardiac proteins such as myosin. Contemporary investigations of the broader autoantibody response in ARF are needed to both inform pathogenesis models and identify new biomarkers for the disease. Methods: This study has utilised a multi-platform approach to profile circulating autoantibodies in ARF. Sera from patients with ARF, matched healthy controls and patients with uncomplicated GAS pharyngitis were initially analysed for autoreactivity using high content protein arrays (Protoarray, 9000 autoantigens), and further explored using a second protein array platform (HuProt Array, 16,000 autoantigens) and 2-D gel electrophoresis of heart tissue combined with mass spectrometry. Selected autoantigens were orthogonally validated using conventional immunoassays with sera from an ARF case-control study (n=79 cases and n=89 matched healthy controls) and a related study of GAS pharyngitis (n=39) conducted in New Zealand. Results: Global analysis of the protein array data showed an increase in total autoantigen reactivity in ARF patients compared with controls, as well as marked heterogeneity in the autoantibody profiles between ARF patients. Autoantigens previously implicated in ARF pathogenesis, such as myosin and collagens were detected, as were novel candidates. Disease pathway analysis revealed several autoantigens within pathways linked to arthritic and myocardial disease. Orthogonal validation of three novel autoantigens (PTPN2, DMD and ANXA6) showed significant elevation of serum antibodies in ARF (p < 0.05), and further highlighted heterogeneity with patients reactive to different combinations of the three antigens. Conclusions: The broad yet heterogenous elevation of autoantibodies observed suggests epitope spreading, and an expansion of the autoantibody repertoire, likely plays a key role in ARF pathogenesis and disease progression. Multiple autoantigens may be needed as diagnostic biomarkers to capture this heterogeneity.

Modulation of colonic inflammation in Mdr1a(-/-) mice by green tea polyphenols and their effects on the colon transcriptome and proteome.

Animal models are an important tool to understand the complex pathogenesis of inflammatory bowel diseases (IBDs). This study tested the anti-inflammatory potential of a green tea extract rich in polyphenols (GrTP) in the colon of the multidrug resistance targeted mutation (Mdr1a(-/-)) mouse model of IBD. Insights into mechanisms responsible for this reduction in inflammation were gained using transcriptome and proteome analyses. Mice were randomly assigned to an AIN-76A (control) or GrTP-enriched diet. At 21 or 24 weeks of age, a colonic histological injury score was determined for each mouse, colon mRNA transcript levels were assessed using microarrays, and colon protein expression was measured using two-dimensional gel electrophoresis and liquid chromatography-mass spectrometry protein identification. Mean colonic histological injury score of GrTP-fed Mdr1a(-/-) mice was significantly lower compared to those fed the control diet. Microarray and proteomics analyses showed reduced abundance of transcripts and proteins associated with immune and inflammatory response and fibrinogenesis pathways, and increased abundance of those associated with xenobiotic metabolism pathways in response to GrTP, suggesting that its anti-inflammatory activity is mediated by multiple molecular pathways. Peroxisome proliferator-activated receptor-α and signal transducer and activator of transcription 1 appear to be two key molecules which regulate these effects. These results support the view that dietary intake of polyphenols derived from green tea can ameliorate intestinal inflammation in the colon of a mouse model of IBD, and are in agreement with studies suggesting that consumption of green tea may reduce IBD symptoms and therefore play a part in an overall IBD treatment regimen.