Gut bacteria from multiple sclerosis patients modulate human T cells and exacerbate symptoms in mouse models | PNAS

The gut microbiota regulates T cell functions throughout the body. We
hypothesized that intestinal bacteria impact the pathogenesis of
multiple sclerosis (MS), an autoimmune disorder of the CNS and thus
analyzed the microbiomes of 71 MS patients not undergoing treatment and
71 healthy controls. Although no major shifts in microbial community
structure were found, we identified specific bacterial taxa that were
significantly associated with MS. Akkermansia muciniphila and Acinetobacter calcoaceticus,
both increased in MS patients, induced proinflammatory responses in
human peripheral blood mononuclear cells and in monocolonized mice. In
contrast, Parabacteroides distasonis, which was reduced in MS patients, stimulated antiinflammatory IL-10–expressing human CD4⁺CD25⁺ T cells and IL-10⁺FoxP3⁺
Tregs in mice. Finally, microbiota transplants from MS patients into
germ-free mice resulted in more severe symptoms of experimental
autoimmune encephalomyelitis and reduced proportions of IL-10⁺
Tregs compared with mice “humanized” with microbiota from healthy
controls. This study identifies specific human gut bacteria that
regulate adaptive autoimmune responses, suggesting therapeutic targeting
of the microbiota as a treatment for MS.