Faculty Bibliography

BACKGROUND: Perturbation of commensal intestinal microbiota has been associated with several autoimmune diseases. Mice deficient in interleukin-1 receptor antagonist (Il1rn -/- mice) spontaneously develop autoimmune arthritis and are susceptible to other autoimmune diseases such as psoriasis, diabetes, and encephalomyelitis; however, the mechanisms of increased susceptibility to these autoimmune phenotypes are poorly understood. We investigated the role of interleukin-1 receptor antagonist (IL-1Ra) in regulation of commensal intestinal microbiota, and assessed the involvement of microbiota subsets and innate and adaptive mucosal immune responses that underlie the development of spontaneous arthritis in Il1rn -/- mice. RESULTS: Using high-throughput 16S rRNA gene sequencing, we show that IL-1Ra critically maintains the diversity and regulates the composition of intestinal microbiota in mice. IL-1Ra deficiency reduced the intestinal microbial diversity and richness, and caused specific taxonomic alterations characterized by overrepresented Helicobacter and underrepresented Ruminococcus and Prevotella. Notably, the aberrant intestinal microbiota in IL1rn -/- mice specifically potentiated IL-17 production by intestinal lamina propria (LP) lymphocytes and skewed the LP T cell balance in favor of T helper 17 (Th17) cells, an effect transferable to WT mice by fecal microbiota. Importantly, LP Th17 cell expansion and the development of spontaneous autoimmune arthritis in IL1rn -/- mice were attenuated under germ-free condition. Selective antibiotic treatment revealed that tobramycin-induced alterations of commensal intestinal microbiota, i.e., reduced Helicobacter, Flexispira, Clostridium, and Dehalobacterium, suppressed arthritis in IL1rn -/- mice. The arthritis phenotype in IL1rn -/- mice was previously shown to depend on Toll-like receptor 4 (TLR4). Using the ablation of both IL-1Ra and TLR4, we here show that the aberrations in the IL1rn -/- microbiota are partly TLR4-dependent. We further identify a role for TLR4 activation in the intestinal lamina propria production of IL-17 and cytokines involved in Th17 differentiation preceding the onset of arthritis. CONCLUSIONS: These findings identify a critical role for IL1Ra in maintaining the natural diversity and composition of intestinal microbiota, and suggest a role for TLR4 in mucosal Th17 cell induction associated with the development of autoimmune disease in mice.

Optimal management of patients with both psoriasis and psoriatic arthritis (PsA) necessitates collaboration among dermatologists and rheumatologists. In this manuscript, we discuss challenges and opportunities for dual care models for patients with psoriasis and PsA and the results of a survey of combined clinics based in North America.

BACKGROUND: Oral vancomycin remains the mainstay of therapy for severe infections produced by Clostridium difficile, the most prevalent cause of healthcare-associated infectious diarrhoea in developed countries. However, its short- and long-term effects on the human intestinal microbiota remain largely unknown. METHODS: We utilized high-throughput sequencing to analyse the effects of vancomycin on the faecal human microbiota up to 22 weeks post-antibiotic cessation. The clinical relevance of the observed microbiota perturbations was studied in mice. RESULTS: During vancomycin therapy, most intestinal microbiota genera and operational taxonomic units (OTUs) were depleted in all analysed subjects, including all baseline OTUs from the phylum Bacteroidetes. This was accompanied by a vast expansion of genera associated with infections, including Klebsiella and Escherichia/Shigella. Following antibiotic cessation, marked differences in microbiota resilience were observed among subjects. While some individuals recovered a microbiota close to baseline composition, in others, up to 89% of abundant OTUs could no longer be detected. The clinical relevance of the observed microbiota changes was further demonstrated in mice, which developed analogous microbiota alterations. During vancomycin treatment, mice were highly susceptible to intestinal colonization by an antibiotic-resistant pathogen and, upon antibiotic cessation, a less-resilient microbiota allowed higher levels of pathogen colonization. CONCLUSIONS: Oral vancomycin induces drastic and consistent changes in the human intestinal microbiota. Upon vancomycin cessation, the microbiota recovery rate varied considerably among subjects, which could influence, as validated in mice, the level of susceptibility to pathogen intestinal colonization. Our results demonstrate the negative long-term effects of vancomycin, which should be considered as a fundamental aspect of the cost-benefit equation for antibiotic prescription.

BACKGROUND: Airway abnormalities and lung tissue citrullination are found in both rheumatoid arthritis (RA) patients and individuals at-risk for disease development. This suggests the possibility that the lung could be a site of autoimmunity generation in RA, perhaps in response to microbiota changes. We therefore sought to test whether the RA lung microbiome contains distinct taxonomic features associated with local and/or systemic autoimmunity. METHODS: 16S rRNA gene high-throughput sequencing was utilized to compare the bacterial community composition of bronchoalveolar lavage fluid (BAL) in patients with early, disease-modifying anti-rheumatic drugs (DMARD)-naive RA, patients with lung sarcoidosis, and healthy control subjects. Samples were further assessed for the presence and levels of anti-citrullinated peptide antibodies (including fine specificities) in both BAL and serum. RESULTS: The BAL microbiota of RA patients was significantly less diverse and abundant when compared to healthy controls, but similar to sarcoidosis patients. This distal airway dysbiosis was attributed to the reduced presence of several genus (i.e., Actynomyces and Burkhordelia) as well as reported periodontopathic taxa, including Treponema, Prevotella, and Porphyromonas. While multiple clades correlated with local and systemic levels of autoantibodies, the genus Pseudonocardia and various related OTUs were the only taxa overrepresented in RA BAL and correlated with higher disease activity and erosions. CONCLUSIONS: Distal airway dysbiosis is present in untreated early RA and similar to that detected in sarcoidosis lung inflammation. This community perturbation, which correlates with local and systemic autoimmune/inflammatory changes, may potentially drive initiation of RA in a proportion of cases.

Background/Purpose: High-throughput sequencing of intestinal microbiota recently revealed that the composition of intestinal microbiota is perturbed in patients with new onset untreated rheumatoid arthritis (RA). In mice, both germ-free condition and administration of oral antibiotics before the onset of arthritis modulate T cell differentiation and attenuate the disease. However, it is not known whether and how modulation of intestinal microbiota after the onset of arthritis may influence the disease. Here, we investigated the involvement of commensal intestinal microbiota in the progression of established arthritis in both T cell-dependent and - independent mouse models. Methods: Mice with established collagen-induced arthritis (CIA) as the most widely-used T cell-dependent model of RA, as well as mice with K/BxN serum-transfer arthritis as a T cell-independent model were treated orally with a cocktail of metronidazole, neomycin, ampicillin (1 g/l each) and vancomycin (0.5 g/l) for one week to partially eliminate intestinal microbiota. Arthritis was assessed macroscopically and by histologic analysis. Differentiation of Th1, Th17 and regulatory T (Treg) cells and production of their prototypic cytokines in intestinal lamina propria and joint-draining lymph nodes were assessed by flow cytometry and Luminex array. Development of anti-collagen type II antibodies was assessed in serum of CIA mice using ELISA. Intestinal and synovial expression of cytokines and serum amyloid A (SAA) isotypes was measured by qPCR. Results: Elimination of intestinal microbiota in mice with ongoing CIA specifically suppressed intestinal Th17 cell differentiation without affecting Th1 and Treg cells. Accordingly, production of interleukin-17 (IL-17), but not interferon gamma, IL-4 and IL-10, by lamina propria lymphocytes was significantly diminished in antibiotic-treated mice. Furthermore, intestinal expression of SAA isoforms and IL-22, known to promote lamina propria Th17 cell differentiation, was suppressed in antibiotic-treated CIA mice. Importantly, elimination of intestinal microbiota resulted in suppressed Th17 cell differentiation and IL-17 production in joint-draining lymph nodes and reduced the severity of established CIA. In contrast, antibiotic treatment did not influence disease severity in the T cellindependent K/BxN serum-transfer arthritis. Intriguingly, the abundance of intestinal Th17 cells strongly correlated with the severity of arthritis in the CIA mice. However, elimination of intestinal microbiota after disease onset did not affect the development of anti-collagen type II autoantibodies. Conclusion : These observations suggest that modulation of commensal intestinal microbiota during established arthritis specifically suppress Th17 differentiation and dampen T cell-mediated arthritic processes. While our study does not advocate the use of antibiotics as a treatment for RA, it supports the notion that inflammatory signals provided by the gut microbiota continue to promote arthritis after its onset. Understanding the exact mechanisms linking the intestinal T cell response with arthritis may help identifying novel therapeutic strategies for RA