Faculty Bibliography

RATIONALE/BACKGROUND:Obstructive Sleep Apnea (OSA) is associated with recurrent obstruction, sub-epithelial edema, and airway inflammation. The resultant inflammation may influence or be influenced by the nasal microbiome. OBJECTIVES/OBJECTIVE:To evaluate whether the composition of the nasal microbiota is associated with obstructive sleep apnea and inflammatory biomarkers. METHODS:Two large cohorts were utilized: 1) a discovery cohort of 472 subjects from the WTCSNORE cohort; and 2) a validation cohort of 93 subjects from the Zaragoza Sleep cohort. Sleep apnea was diagnosed using home sleep tests. Nasal lavages were obtained from cohort subjects to measure: 1) microbiome composition (based on 16S rRNA gene sequencing); 2) biomarkers for inflammation (inflammatory cells, IL-8, and IL-6). Longitudinal 3 months samples were obtained in the validation cohort including post-CPAP treatment when indicated. RESULTS:In both cohorts, we identified that: 1) severity of OSA correlated with differences in microbiome diversity and composition; 2) the nasal microbiome of subjects with severe OSA were enriched with Streptococcus, Prevotella, and Veillonella; 3) the nasal microbiome differences were associated with inflammatory biomarkers. Network analysis identified clusters of co-occurring microbes that defined communities. Several common oral commensals (e.g., Streptococcus, Rothia, Veillonella, and Fusobacterium) correlated with apnea-hypopnea index. Three months of treatment with CPAP did not change the composition of the nasal microbiota. CONCLUSIONS:We demonstrate that the presence of an altered microbiome in severe OSA is associated with inflammatory markers. Further experimental approaches to explore causal links are needed.

Background/Purpose: The microbiome serves a number of important functions, including modulation of the immune system and protection from pathogenic microorganisms1. Many autoimmune diseases have been associated with intestinal microbial dysbiosis1. Recent studies have also demonstrated that microbiota can affect the lifetime, bioavailability and efficacy of drugs2. Conversely, even drugs designed to specifically target human cells have been associated with changes in microbial composition3. To date, most research has focused on bacterial microorganisms and little is known about the role that fungal microorganisms (the mycobiome) play, including their interactions with bacteria. In this study, we characterized the ecological effects of biologic therapies on the intestinal mycobiome.
Method(s): Fecal samples were collected from SpA patients pre- and post-treatment with either tumor necrosis factor inhibitors (TNFi; n=15) or secukinumab (n=14), an anti-IL-17A monoclonal antibody (IL-17i). Subjects treated with TNFi were naive to biologic therapy, whereas those treated with secukinumab previously failed or had incomplete response to TNFi. Samples underwent DNA extraction, amplification, and gene sequencing of the ITS1 region conserved in fungi. In parallel, gene sequencing of the 16S rRNA gene region conserved in bacteria was also performed. Sequences were analyzed with R and Quantitative Insights into Microbial Ecology (QIIME).
Result(s): ITS fungal data reveled that, on average, subjects treated with TNFi and IL-17i did not have major differences in overall microbial alpha or beta diversity pre- and post-treatment. However, there were dramatic shifts in the relative abundance of specific taxa, such as Candida albicans, which were more prominent in the IL-17i cohort compared to the TNFi cohort (p=0.04). The IL-17i cohort also demonstrated similar changes in certain 16S bacterial taxa, including Clostridia (p=0.02) and Clostridiales (p=0.02).
Conclusion(s): We characterized, for the first time, the effects of two biologic therapies on human intestinal fungal and bacterial microbiota composition. Treatment with biologics, particularly IL-17i, leads to a gut microbial dysbiosis characterized by significant changes in abundance of C. albicans and Clostridia in a subgroup of SpA patients. This is in line with the known increased risk of candidiasis seen with IL-17i, and may at least partially explain the potential link between IL-17 blockade, intestinal dysbiosis, and the subclinical and clinical gut inflammation observed in some patients treated with these molecules. Further studies to understand the downstream effects of these perturbations may allow for the development of precision medicine approaches in PsA and SpA