The microbiome in primary Sjögren’s syndrome: the oral, gut and vaginal microbiome of primary Sjögren’s syndrome patients

Primary Sjögren’s syndrome (pSS) is a systemic inflammatory autoimmune disease affecting 1 in 1000 persons in the general population. pSS is characterized by lymphocyte infiltration in the lacrimal and salivary glands causing symptoms of dry eyes and dry mouth. pSS can manifest systemically in the joints, skin, peripheral nervous system, kidneys and lungs. Despite advancement in knowledge of the genetic background of pSS, the etiology of pSS remains largely unknown. Recent studies suggest that the human microbiome is involved in the development of inflammatory autoimmune diseases. However, the relationship between the human microbiome and pSS was only scarcely studied before this thesis. The aim of this thesis was to assess whether pSS is associated with a disease-specific microbiota composition in the oral cavity, the gut and the vagina. The microbiota composition of oral, fecal and vaginal samples from pSS patients was studied in comparison with that of healthy controls, population controls and disease controls using 16S rRNA gene sequencing. pSS patients showed an altered oral microbiome compared to healthy controls, which was mainly explained by reduced salivary secretion in these patients. pSS and systemic lupus erythematosus (SLE) patients shared similar alterations in the gut microbiota composition, distinguishing pSS/SLE patients from general population controls. The vaginal microbiome of women with pSS-associated vaginal dryness did not differ from controls. Our results provide evidence for a connection between the oral and gut microbiome and pSS. Future research is needed to elucidate the disease-specificity of microbiota-pSS associations and the cause and effect relationship