Alterations to gut microbiota in mice lacking C5aR1 in Alzheimer’s mouse model do not account for protective effects in disease progression.

The complement (C’) system contributes to enhanced inflammation and cognitive decline in Alzheimer’s disease (AD). Previous studies demonstrated that genetic ablation of downstream receptor C5aR1 provides protection from cognitive decline in AD animal models. C’ activation and associated cell‐signaling may influence the composition of the gut microbiome, modulating systemic inflammation, and ultimately inducing behavioral and cognitive changes. The objective of this study was to determine if deletion of C5aR1 (C5aR1KO) alters the fecal microbiome in the Arctic (Arc) model of AD which could contribute to the previously observed protection from cognitive decline (Hernandez et al., 2017).