Differential immune responses and microbiota profiles in children with autism spectrum disorders and co-morbid gastrointestinal symptoms.

OBJECTIVES: Many studies have reported the increased presence of gastrointestinal (GI) symptoms in children with autism spectrum disorders (ASD). Altered microbiome profiles, pro-inflammatory responses and impaired intestinal permeability have been observed in children with ASD and co-morbid GI symptoms, yet few studies have compared these findings to ASD children without GI issues or similarly aged typical developing children. The aim of this study was to determine whether there are biological signatures in terms of immune dysfunction and microbiota composition in children with ASD with GI symptoms. METHODS: Children were enrolled in one of four groups: ASD and GI symptoms of irregular bowel habits (ASD(GI)), children with ASD but without current or previous GI symptoms (ASD(NoGI)), typically developing children with GI symptoms (TD(GI)) and typically developing children without current or previous GI symptoms (TD(NoGI)). Peripheral blood mononuclear cells (PBMC) were isolated from the blood, stimulated and assessed for cytokine production, while stool samples were analyzed for microbial composition. RESULTS: Following Toll-Like receptor (TLR)-4 stimulation, the ASD(GI) group produced increased levels of mucosa-relevant cytokines including IL-5, IL-15 and IL-17 compared to ASD(NoGI). The production of the regulatory cytokine TGFβ1 was decreased in the ASD(GI) group compared with both the ASD(NoGI) and TD(NoGI) groups. Analysis of the microbiome at the family level revealed differences in microbiome composition between ASD and TD children with GI symptoms; furthermore, a predictive metagenome functional content analysis revealed that pathways were differentially represented between ASD and TD subjects, independently of the presence of GI symptoms. The ASD(GI) also showed an over-representation of the gene encoding zonulin, a molecule regulating gut permeability, compared to the other groups. CONCLUSIONS: Overall our findings suggest that children with ASD who experience GI symptoms have an imbalance in their immune response, possibly influenced by or influencing metagenomic changes, and may have a propensity to impaired gut barrier function which may contribute to their symptoms and clinical outcome.