Understanding how perturbations in microbial mimicry promotes breakdown in tolerance to insulin

了解微生物拟态的扰动如何促进胰岛素耐受性的崩溃

• 批准号: 2888070
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2888070
• 关键词: Understanding; how; perturbations; microbial; mimicry

BackgroundType 1 diabetes (T1D) is an autoimmune disease, resulting from T-cell mediated destruction of insulin-producing pancreatic islet cells. Polymorphisms of human leukocyte antigen (HLA) class II molecules are major genetic risk factors for T1D. Recently, a host-microbiome interaction, explaining HLA class II susceptibility, has been characterised1. This paper identified cross-reactive T cells that recognised microbial-mimics of insulin bound to the T1D-predisposing class II molecule DQ8. The T1D-protective HLA-DQ6 molecule strongly bound microbial mimics of insulin, consistent with a role for cross-reactive regulatory T cells (Treg) in lowering disease risk. While the T1D-predisposing HLA-DQ8 molecule bound these peptides more weakly, favouring escape of cross-reactive effector T cells (Teff) from the thymus and increased anti-insulin autoimmunity. The majority of microbial-mimics belonged to the transketolase (TKT) superfamily. TKT is an enzyme involved in processing dietary fibre and is upregulated during infant weaning2. This transition, from milk to solid food, induces rapid expansion of gut microbiota, and is a critical period for developing tolerance3. As the first autoantibodies to insulin appear most often post-weaning, at 9-18 months of age, this suggests a primary cause of autoimmune diabetes.We hypothesise that aberrant expression of microbial-TKT disrupts immune homeostasis, favouring activation of cross-reactive Teffs, to trigger autoimmunity against insulin. These perturbations are likely to be driven by dysbiotic microbial taxa, expressing inappropriate amounts of TKT. Research DesignThrough the GPPAD consortium4,5, longitudinal stool and blood samples have been collected from 670 children, with a high risk of T1D based on their genetic risk score (GRS)6. Longitudinal changes in autoantibody levels, blood metabolomes, and gut microbiome will be monitored and stratified by T1D-GRS, presence of T1D-autoantibodies, and clinical status.In our lab, from the DMech-biome project, saliva and stool samples (at 8 weeks and 8 months of age) from 445 infants have been collected. As these participants have not been selected based on T1D-GRS, they can act as a population control cohort. Interactions between the microbiome composition, HLA-haplotypes, and other genetic risk loci will be analysed. Longitudinal comparisons of metagenomic analysis will allow insights into changes in gut microbiome composition across weaning and early life. This analysis could infer changes in microbial-TKT expression, and identify potential dysbiotic microbial taxa that may promote activation of cross-reactive Teff.Development of HLA tetramers will assess the presence of cross-reactive T cells recognising both insulin and microbial-TKT peptides. Assessment of different HLA class II tetramers in combination with microbial context-molecules, coupled with fluorescent-activated cell sorting, will allow insight into how different HLA-haplotypes favour production of cross-reactive Teffs. This could assess whether tolerogenic microbial context-molecules could promote Treg production despite presentation through predisposing HLA molecules.ImpactThis project aims to assess whether development of a dysbiotic, proinflammatory microbiome in early life can increase risk of developing T1D, through inappropriate expression and presentation of microbial-TKT. Through longitudinal assessment, changes within microbiota taxa and expression of microbial-TKT can be compared to development of T1D autoantibodies and clinical status. The identification of microbial strains, important for conferring tolerance through activation of cross-reactive Treg could inform development of preventative microbiome-targeted therapies.References1. Garcia, A. R. et al MedXiv 2022 4. Ziegler, A. G. et al BMJ Open 20192. Vatanen, T. et al Nature 2018 5. Ziegler, A. G. et al BMJ Open 20213. al Nabhani, Z. et al Immunity 2019 6. Redondo

背景 1 型糖尿病 (T1D) 是一种自身免疫性疾病，由 T 细胞介导的产生胰岛素的胰岛细胞破坏所致。人类白细胞抗原 (HLA) II 类分子的多态性是 T1D 的主要遗传危险因素。最近，宿主-微生物组相互作用，解释了 HLA II 类易感性，已得到表征1。本文鉴定了交叉反应性 T 细胞，其识别与 T1D 易感性 II 类分子 DQ8 结合的胰岛素微生物模拟物。 T1D 保护性 HLA-DQ6 分子与胰岛素的微生物模拟物强烈结合，这与交叉反应性调节性 T 细胞 (Treg) 在降低疾病风险中的作用一致。而 T1D 易感性 HLA-DQ8 分子与这些肽的结合更弱，有利于交叉反应效应 T 细胞 (Teff) 从胸腺逃逸，并增强抗胰岛素自身免疫。大多数微生物模拟物属于转酮酶（TKT）超家族。 TKT 是一种参与膳食纤维加工的酶，在婴儿断奶期间会上调2。从牛奶到固体食物的这种转变会引起肠道微生物群的快速扩张，并且是产生耐受性的关键时期3。由于第一个胰岛素自身抗体最常出现在断奶后，即 9-18 个月大时，这表明自身免疫性糖尿病的主要原因。我们假设微生物 TKT 的异常表达会破坏免疫稳态，有利于交叉反应 Teffs 的激活，触发针对胰岛素的自身免疫。这些扰动可能是由失调的微生物类群驱动的，表达了不适当的 TKT 量。研究设计通过 GPPAD 联盟4,5，从 670 名儿童中收集了纵向粪便和血液样本，根据他们的遗传风险评分 (GRS)6，这些儿童患有 T1D 风险较高。自身抗体水平、血液代谢组和肠道微生物组的纵向变化将通过 T1D-GRS、T1D 自身抗体的存在和临床状态进行监测和分层。在我们的实验室中，来自 DMech-biome 项目的唾液和粪便样本（在 8已收集了 445 名婴儿（周龄和 8 个月大）的样本。由于这些参与者不是根据 T1D-GRS 选择的，因此他们可以作为人口控制队列。将分析微生物组组成、HLA 单倍型和其他遗传风险位点之间的相互作用。宏基因组分析的纵向比较将有助于深入了解断奶期和生命早期肠道微生物组组成的变化。该分析可以推断微生物 TKT 表达的变化，并识别可能促进交叉反应 Teff 激活的潜在失调微生物类群。HLA 四聚体的开发将评估识别胰岛素和微生物 TKT 肽的交叉反应 T 细胞的存在。对不同的 HLA II 类四聚体与微生物背景分子的结合进行评估，再加上荧光激活细胞分选，将有助于深入了解不同的 HLA 单倍型如何有利于交叉反应 Teff 的产生。这可以评估耐受性微生物环境分子是否可以促进 Treg 的产生，尽管通过易感 HLA 分子呈现。影响该项目旨在评估生命早期发育不良、促炎性微生物组是否会通过微生物的不适当表达和呈现而增加患 T1D 的风险。 -TKT。通过纵向评估，微生物群内的变化和微生物 TKT 的表达可以与 T1D 自身抗体的发展和临床状态进行比较。微生物菌株的鉴定对于通过交叉反应性 Treg 的激活赋予耐受性非常重要，可以为预防性微生物组靶向疗法的开发提供信息。 Garcia, A. R. 等人 MedXiv 2022 4. Ziegler, A. G. 等人 BMJ Open 20192. Vatanen, T. 等人 Nature 2018 5. Ziegler, A. G. 等人 BMJ Open 20213. al Nabhani, Z. 等人 Immunity 2019 6. Redondo