Gut-immune reactivity underlies sex differences in the maternal immune activation preclinical model of autism

The gut microbiome plays a vital role in health and disease, including neurodevelopmental disorders like autism spectrum disorder (ASD). ASD affects 4:1 males-to-females, and sex differences are apparent in gut microbiota composition among ASD individuals and in animal models of this condition, such as the maternal immune activation (MIA) mouse model. However, few studies have included sex as a biological variable when assessing the role of gut microbiota in mediating ASD symptoms. Using the MIA model of ASD, we assessed whether gut microbiota contributes to the sex differences in the presentation of ASD-like behaviors. Gut microbiota transplantation from MIA or vehicle/control male and female mice into healthy, otherwise unmanipulated, 4-week-old C57Bl/6 mice was performed for 6 treatments over 12 days. Colonization with male, but not female, MIA microbiota was sufficient to reduce sociability, increase repetitive burying behavior, decrease microbiota diversity and increase neuroinflammation with more pronounced deficits in male recipients. Colonization with both male and female donor microbiota altered juvenile ultrasonic vocalizations and anxiety-like behavior in recipients of both sexes, and there was an accompanied change in the gut microbiota and serum cytokine IL-4 and IL-7 levels of all recipients of MIA gut microbiota. In addition to the increases in gut microbes associated with pathological states, the female donor microbiota profile also had increases in gut microbes with known neural protective effects (e.g., Lactobacillus and Rikenella). These results suggest that gut reactivity to environmental insults, such as in the MIA model, plays a pivotal role in shaping the sex disparity observed in ASD development. Significance StatementIncreasing evidence suggests a role for the gut microbiota in autism spectrum disorder (ASD). ASD development has largely been associated with genetic mutations; however, with a 4-fold greater risk among males than females, the sex of a child is a predictor equivalent to familial ASD incidence. Using a preclinical mouse model of ASD, maternal immune activation (MIA), we show that gut microbiota transfer from MIA males into unaffected control males was most effective in reproducing ASD-like symptoms and led to distinct gut microbiota composition and greater inflammation in recipients. These findings suggest that how the gut responds to environmental insults differs between sexes, and this variance contributes to the greater risk ASD development among males than females.