Autism spectrum disorder (ASD) is a developmental disorder that is characterized by deficits in social communication and restricted, repetitive, and stereotyped behaviors. In addition to neurobehavioral symptoms, children with ASD often have gastrointestinal symptoms (e.g. constipation, diarrhea, gas, abdominal pain, reflux). Several studies have proposed the role of gut microbiota and metabolic disorders in gastrointestinal symptoms and neurodevelopmental dysfunction in ASD patients; these results offer promising avenues for novel treatments of this disorder. Interventions targeting the gut microbiota - such as fecal microbiota transplant (FMT), microbiota transplant therapy (MTT), probiotics, prebiotics, synbiotics, antibiotics, antifungals, and diet - promise to improve gut health and can potentially improve neurological symptoms. The modulation of the gut microbiota using MTT in ASD has shown beneficial and long-term effects on GI symptoms and core symptoms of autism. Also, the modulation of the gut microbiota to resemble that of typically developing individuals seems to be the most promising intervention. As most of the studies carried out with MTT are open-label studies, more extensive double-blinded randomized control trials are needed to confirm the efficacy of MTT as a therapeutic option for ASD. This review examines the current clinical research evidence for the use of interventions that target the microbiome - such as antibiotics, antifungals, probiotics/prebiotics, synbiotics, and MTT - and their effectiveness in changing the gut microbiota and improving gastrointestinal and neurobehavioral symptoms in ASD.

Autism spectrum disorder (ASD) affects more than 1% of children, and there is no viable pharmacotherapeutic agent to treat the core symptoms of ASD. Studies have shown that children with ASD show changes in their levels of immune response molecules. Our previous studies have shown that ASD is more common in children with folate receptor autoantibodies. We also found that children with ASD have abnormal gut immune function, which was characterized by a significant increase in the content of immunoglobulin A and an increase in gut-microbiota-associated epitope diversity. These studies suggest that the immune mechanism plays an important role in the occurrence of ASD. The present study aims to systematically assess gene mutations in immune mediators in patients with ASD. We collected genetic samples from 72 children with ASD (2−12 years old) and 107 healthy controls without ASD (20−78 years old). We used our previously-designed immune gene panel, which can capture cytokine and receptor genes, the coding regions of MHC genes, and genes of innate immunity. Target region sequencing (500×) and bioinformatics analytical methods were used to identify variants in immune response genes associated with patients with ASD. A total of 4 rare variants were found to be associated with ASD, including HLA-B: p.A93G, HLA-DQB1: p.S229N, LILRB2: p.R322H, and LILRB2: c.956-4C>T. These variants were present in 44.44% (32/72) of the ASD patients and were detected in 3.74% (4/107) of the healthy controls. We expect these genetic variants will serve as new targets for the clinical genetic assessment of ASD, and our findings suggest that immune abnormalities in children with ASD may have a genetic basis.