Gut microbiota depletion from early adolescence alters adult immunological and neurobehavioral responses in a mouse model of multiple sclerosis.

Emerging evidence indicates that gut microbiota interacts with immune and nervous systems in the host and plays a critical role in the pathogenesis of multiple sclerosis (MS) and many psychiatric disorders such as depression and anxiety. The aim of this study was to explore the influence of gut bacterial depletion from early adolescence on adult immunological and neurobehavioral responses in mice with experimental-autoimmune-encephalomyelitis (EAE). We used an animal model of gut microbiota depletion induced by antibiotics from weaning to adulthood to assess clinical signs, cognitive function and depression-and anxiety-related symptoms in non-EAE and EAE-induced mice. We measured levels of interferon (IFN)-γ, interleukin (IL)-17A and IL-10 in serum, and BDNF, IL-1β and tumor necrosis factor (TNF)-α) in the hippocampus. Antibiotic-treated mice displayed a significant delay in the onset of clinical symptoms of EAE. However, a higher severity of EAE was found between days 19-22 post-immunization in antibiotics-treated mice, while a reduction in the clinical signs of MS was observed at days 24-25 post-immunization. Antibiotic administration decreased IFN-γ and IL-17A levels and increased IL-10 in serum of EAE-induced mice. Antibiotic treatment significantly decreased hippocampal BDNF and enhanced learning and memory impairments in EAE-induced mice. However, no significant changes were found in non-EAE mice. Non-EAE and EAE mice treated with antibiotics exhibited increased anxiety-related behaviors, whereas depression-related symptoms and increased hippocampal TNF-α and IL-1β were only observed in EAE-induced mice treated with antibiotics. This study supports the view that depletion of gut microbiota by antibiotics from weaning profoundly impacts adult immunological and neurobehavioral responses.