"肠道菌群-胆汁酸"轴驱动RORγt依赖的Th17/Treg失衡参与母体免疫激活小鼠ASD发生的作用和机制研究

母体免疫激活（MIA）小鼠ASD的发生由肠道菌群介导的Th17/IL-17a升高所致，尚不清楚介导Th17/IL-17a升高的关键肠道细菌。研究发现，肠道菌群抗原肽以MHCII依赖性方式调节RORγt+Th17细胞分化，并通过与人抗原的交叉反应参与自身免疫性疾病的发生，菌群胆汁酸代谢物调控了RORγt+Treg的发育和IgA响应，维持了Th17/Treg细胞平衡。申请人前期NSFC发现，ASD患儿肠道IgA升高，且与肠道菌群抗原肽及抗原基因丰度异常，胆汁酸及代谢菌丰度升高等相关。我们推测，“肠道菌群-胆汁酸”轴可能介导Th17/IL-17a增加。本项目将通过IgA-seq/IgG-seq技术鉴定ASD潜在有害细菌，利用HLA多肽组学技术验证ASD肠道菌群表位肽，结合MIA小鼠大脑皮层/肠组织T细胞的单细胞RNA测序研究肠道菌群-胆汁酸轴驱动Th17/Treg失衡并参与ASD发生的机制。

Gut microbiota-mediated Th17 cell increase and IL-17a increase may cause ASD behavior in maternal immune-activated (MIA) mice, it is unclear which intestinal bacteria and by which pathways mediate Th17 cell differentiation and IL-17a increase. Previous studies have found that gut microbiota-derived antigen peptides regulate RORγt + TH17 cell differentiation in a MHCII-dependent manner, and participate in the occurrence of autoimmune diseases by cross-reacting with human antigens; Bile acid metabolites of gut microbiota were also found to regulate RORγt + Treg development and IgA response, and maintain Th17 / Treg cell balance. Our previous NSFC results show that the gut IgA level of children with ASD is significantly increased, and it is related to the gut microbiota epitope / pathogen gene diversity, Increased bile acid and metabolite bacterial abundance were also positively correlated with increased gut IgA levels; Based on this, we speculate that the gut microbiota-bile acid axis drives RORγt-dependent Th17 / Treg imbalances to participate in the occurrence of ASD-like behavior in maternal immune-activated mice. This project will use IgA-seq / IgG-seq method to detect the composition of gut bacteria with serum IgG or gut IgA responses, identify potentially harmful bacteria related to ASD, use HLA peptidomics to verify the epitope peptides derived from the gut bacteria associated with ASD; Finally, the classic MIA mouse model combined with single-cell RNA sequencing technology were used to study the possible molecular mechanism of gut microbiota-bile acid axis driving Th17 / Treg imbalance and participating in ASD.