Characterisation of the Lung Microbiome in Multiple Sclerosis

Sammanfattning

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system in which autoreactive immune cells cause demyelination and neuronal damage. Cigarette smoking is a well-established environmental risk factor for developing MS, pointing to the lung as a possible site where disease-relevant immune responses may be initiated. Animal model studies have further shown that the lung microbiome can modulate central nervous system autoimmunity, but not in the context of MS. Alterations of the lung microbiome have also been reported in rheumatoid arthritis and sarcoidosis patients, raising the question of whether similar changes occur in other autoimmune diseases like MS. To investigate this, the V4 region of the bacterial 16S ribosomal RNA gene was sequenced from bronchoalveolar lavage fluid obtained from MS patients and healthy individuals. Although within-sample diversity was comparable between groups, community composition differed significantly based on abundance-weighted measures. Differential abundance analyses identified depletion of several genera in MS, most consistently Veillonella, as part of a broader loss of oral-associated commensal genera. This depletion pattern partially overlaps with alterations reported in the lungs of rheumatoid arthritis patients and with gut microbiome findings in MS. These findings characterise the lower-airway microbiome in MS and suggest that the lung microbiome may be relevant to immune processes associated with central nervous system autoimmunity.