With an estimated number of more than 2 million people worldwide, Multiple Sclerosis (MS) is the most prevalent chronic inflammatory disease of the central nervous system (CNS) affecting primarily young females. Like almost all autoimmune diseases MS manifests itself as a consequence of several environmental trigger factors meeting a genetic predisposition. Recently, Ocrelizumab a humanized anti-CD20 monoclonal antibody that depletes B cells primarily through antibody-dependent cellular activity has been licensed for the  treatment of relapsing-remitting and primary progressive MS due to its high efficacy. However, the molecular reasons for the ability of Ocrelizumab to slow progression as well as the long-term risks of B-cell-depletion remain uncertain. Recent studies show an increasing  evidence that an altered microbiome composition might influence the progression of MS – however there has been no study elucidating the effects of MS treatment on this observed dysbiosis to date.