Faculty Bibliography

RA is a complex multifactorial chronic disease that transitions through several stages. Multiple studies now support that there is a prolonged phase in early RA development during which there is serum elevation of RA-related autoantibodies including RF and ACPAs in the absence of clinically evident synovitis. This suggests that RA pathogenesis might originate in an extra-articular location, which we hypothesize is a mucosal site. In discussing this hypothesis, we will present herein the current understanding of mucosal immunology, including a discussion about the generation of autoimmune responses at these surfaces. We will also examine how other factors such as genes, microbes and other environmental toxins (including tobacco smoke) could influence the triggering of autoimmunity at mucosal sites and eventually systemic organ disease. We will also propose a research agenda to improve our understanding of the role of mucosal inflammation in the development of RA.

Background and objectives Airway abnormalities and increased lung tissue citrullination is found in both RA patients and individuals at at-risk for the development of disease. Recent data suggest that the gut (Prevotella copri) and oral (Porphyromonas gingivalis) microbiome might potentially contribute to the priming of an aberrant systemic immune response characteristic of RA. Our objective was to study whether the RA lung microbiome contains distinct taxonomic features associated with local and/or systemic autoimmunity. Materials and methods Bronchoalveolar lavage (BAL) samples from 20 subjects with RA, 10 with sarcoidosis (DC) and 24 healthy controls (HC) were obtained by research bronchoscopy. 16S rDNA sequencing was performed to define microbiota composition. Autoantibodies, including anti-CCP, RF and ACPAs were also measured in sera of RA subjects. Statistical analysis was performed using wilcoxon test and Spearman correlation. Results The16S sequencing data showed similar alpha/beta diversity between RA and DC groups, but significantly different from HC. Taxonomic comparison between groups was performed using LEfSe, which revealed several significant differences (LDA score>2). Multiple taxa, including Rhanella and Rhodanobacter were present only in the RA and DC groups, but completely absent from HC (p < 0.001). While RA BAL samples were enriched with Sphingobacteria, sarcoidosis BAL was enriched with Bacteroidia, Rhizobiales, Nitrospirales, and Campylobacter. Raoultella and Barnesiella correlated with CCP2 levels in BAL (rho = 0.49 and 0.47; p-value = 0.026 and 0.032). Serum levels of CCP-IgA had a negative correlation with Massilia and Tannerella (rho = -0.63 and 0.53; p-value 0.003 and 0.016), and a positive correlation with Vagococcus and Lactobacillus (rho= 0.59 and 0.54; p-value 0.006 and 0.014). Unclas-Lactobacillales also had a positive correlation with serum levels of RF-IgA (rho = 0.71; p-value <0.001). Serum levels of anti-CCP2 antibodies had a positive correlation with Porphyromonas, Rahnella and Chryseobacterium (rho =0.46, 0.46 and 0.45; p-value = 0.03, 0.03 and 0.04). Conclusions Despite the relatively small number of samples analysed, several taxonomic differences were noted between groups. Correlations between relative abundance of specific taxa in RA BAL with serum autoantibodies (ie, anti-CCP) support an association between the lung microbiome and the host immune phenotype in RA. Further evaluation of functional aspects of this microbiome may provide further insights into its possible contribution to RA

Programmed death-1 (PD-1) is an inhibitory co-receptor that is highly expressed in T lymphocytes that has been shown to downregulate inflammatory responses in several inflammatory diseases including systemic lupus erythematosus and rheumatoid arthritis. Yet, the role of PD-1 in psoriatic arthritis (PsA) has not been studied. In order to fill this gap, we measured the expression levels of PD-1 in peripheral T cells from patients with active disease. Twenty patients and fifteen age-matched healthy control subjects were recruited. The percentage of CD3(+)PD-1(+) T cells was measured by flow cytometry. Despite normal concentration of peripheral T cells, the expression levels of PD-1 were significantly higher in patients compared to healthy controls. Interestingly, among the patients, the expression levels inversely correlated with disease activity measured by disease activity scores (DAS28). PD-1 expression levels strongly correlated with the number of tender and swollen joints, but not with C-reactive protein (CRP) levels or psoriasis area and severity index (PASI). Functionally, in vitro ligation of PD-1 receptor in PsA T cells inhibited interleukin-2 (IL-2) secretion, Akt phosphorylation, and Rap1 activation. These findings suggest that PD-1 might serve as a biomarker for disease activity in PsA and highlight the need for additional studies in order to establish the role of PD-1 in PsA pathogenesis.

Background: Rheumatoid arthritis (RA) is a complex, autoimmune disease in which several genetic and environmental factors play a role. Recent data suggest that the gut and oral microbiome might potentially contribute to an aberrant systemic immune response characteristic of RA. Among recently studied microbiota, both P. gingivalis in the oral cavity1 and P. copri2 in the gut have been implicated. Imaging abnormalities seen in RA patients and also in at-risk individuals for the development of disease3 along with the presence of autoantibodies in the airways4 implicates the lung as yet another site of autoimmunity generation in RA. Objectives: To test whether the RA lung microbiome contains distinct taxonomic features that associate with local and/or systemic autoimmunity Methods: Bronchoalveolar lavage (BAL) samples from 20 subjects with RA and 10 with sarcoidosis were obtained by research bronchoscopy. 16S rDNA sequencing was performed to define microbiota composition. Levels of arginine/citrulline were measured in BAL fluid using GC-MS for all samples. Autoantibodies, including anti-CCP, RF and ACPAs were also measured in RA subjects in BAL and serum. Statistical analysis was performed using wilcoxon test and Spearman correlation. Results: There were no differences in demographic or clinical characteristics (including smoking status) between the groups. 16S sequencing data show similar alpha and beta diversity based on UniFrac between groups. Taxonomic comparison between RA and sarcoidosis was performed using LEfSe, which revealed several significant differences (LDA score>2). While RA BAL samples were enriched with Sphingobacteria, sarcoidosis BAL was enriched with Bacteroidia, Rhizobiales, Nitrospirales, and Campylobacter. GC-MS showed similar levels of arginine and citrulline in BAL for the sarcoidosis and RA groups. Raoultella and Barnesiella correlated with CCP2 levels in BAL (rho=0.49 and 0.47; p-value=0.026 and 0.032 respectively). Serum levels of CCP-IgA had a negative correlation with Massilia and Tannerella (rho= -0.63 and 0.53; p-value 0.003 and 0.016, respectively), and a positive correlation with Vagococcus and Lactobacillus (rho=0.59 and 0.54; p-value 0.006 and 0.014, respectively). Unclas-Lactobacillales also had a positive correlation with serum levels of RF-IgA (rho=0.71; p-value <0.001). Serum levels of anti-CCP2 antibodies had a negative correlation with Escherichia and Bdellovibrio (rho=-0.47 and 0.45, p-value=0.03 and 0.04 respectively), and a positive correlation with Porphyromonas, Rahnella and Chryseobacterium (rho=0.46, 0.46 and 0.45; p-value=0.03, 0.03 and 0.04 respectively). Conclusions: Despite the relatively small number of samples analyzed, several taxonomic differences were noted between RA and Sarcoidosis. Correlations between relative abundance of specific taxa in BAL with serum autoantibodies (i.e., anti-CCP) support an association between the lung microbiome and the host immune phenotype in RA. Further evaluation of functional aspects of this microbiome may provide further insights into its possible contribution to RA

Humans and other mammals are not (and have never been) alone. From the moment we are born, millions of microorganisms populate our bodies and coexist with us rather peacefully for the rest of our lives. This massive anitgenic load derived from microorganisms (and their genomes) define the human microbiome. Micro-organisms living in or on us have evolved to extract the energy they require to survive, and in exchange they support the physiological, nutritional, metabolic and immune functions that have contributed to our evolutionary success. Although currently categorized as autoimmune disorders and regarded as complex genetic disease, the ultimate cause of rheumatoid arthritis (RA), psoriatic arthirits (PsA), and related conditions remain elusive. It seems that interplay between predisposing genetic factors and environmental triggers is required for disease manifestations. New insights from DNA sequence- based analyses of gut and skin microbial communities and a renewed interest in mucosal immunology suggest that the microbiome represents an important environmental factor that can modulate inflammation and autoimmune disease manifestations. Multiple animal models and novel human studies suggest a possible role for a disruption in the microbiome composition (dysbiosis) in the pathogenesis of inflammatory arthritis, presumably through activation of proinflammatory T-cells via antigenic molecules and/or bacterial-derived metabolites