Axial spondyloarthritis patients have altered mucosal IgA response to oral and fecal microbiota

Axial spondyloarthritis (axSpA) is an inflammatory arthritis involving the spine and the sacroiliac joint with extra-articular manifestations in the eye, gut, and skin. The intestinal microbiota has been implicated as a central environmental component in the pathogenesis of various types of spondyloarthritis including axSpA. Additionally, alterations in the oral microbiota have been shown in various rheumatological conditions, such as rheumatoid arthritis (RA). Therefore, the aim of this study was to investigate whether axSpA patients have an altered immunoglobulin A (IgA) response in the gut and oral microbial communities. We performed 16S rRNA gene (16S) sequencing on IgA positive (IgA⁺) and IgA negative (IgA^-) fractions (IgA-SEQ) from feces (n=17 axSpA; n=14 healthy) and saliva (n=14 axSpA; n=12 healthy), as well as on IgA-unsorted fecal and salivary samples. PICRUSt2 was used to predict microbial metabolic potential in axSpA patients and healthy controls (HCs). IgA-SEQ analyses revealed enrichment of several microbes in the fecal (Akkermansia, Ruminococcaceae, Lachnospira) and salivary (Prevotellaceae, Actinobacillus) microbiome in axSpA patients as compared with HCs. Fecal microbiome from axSpA patients showed a tendency towards increased alpha diversity in IgA⁺ fraction and decreased diversity in IgA^- fraction in comparison with HCs, while the salivary microbiome exhibits a significant decrease in alpha diversity in both IgA⁺ and IgA^- fractions. Increased IgA coating of Clostridiales Family XIII in feces correlated with disease severity. Inferred metagenomic analysis suggests perturbation of metabolites and metabolic pathways for inflammation (oxidative stress, amino acid degradation) and metabolism (propanoate and butanoate) in axSpA patients. Analyses of fecal and salivary microbes from axSpA patients reveal distinct populations of immunoreactive microbes compared to HCs using the IgA-SEQ approach. These bacteria were not identified by comparing their relative abundance alone. Predictive metagenomic analysis revealed perturbation of metabolites/metabolic pathways in axSpA patients. Future studies on these immunoreactive microbes may lead to better understanding of the functional role of IgA in maintaining microbial structure and human health.

Network-Based Differences in the Vaginal and Bladder Microbial Communities Between Women With and Without Urgency Urinary Incontinence

Background

Little is known about the relationship of proximal urogenital microbiomes in the bladder and the vagina and how this contributes to bladder health. In this study, we use a microbial ecology and network framework to understand the dynamics of interactions/co-occurrences of bacteria in the bladder and vagina in women with and without urgency urinary incontinence (UUI).

Methods

We collected vaginal swabs and catheterized urine specimens from 20 women with UUI (cases) and 30 women without UUI (controls). We sequenced the V4 region of the bacterial 16S rRNA gene and evaluated using alpha and beta diversity metrics. We used microbial network analysis to detect interactions in the microbiome and the betweenness centrality measure to identify central bacteria in the microbial network. Bacteria exhibiting maximum betweenness centrality are considered central to the microbe-wide networks and likely maintain the overall microbial network structure.

Results

There were no significant differences in the vaginal or bladder microbiomes between cases and controls using alpha and beta diversity. Silhouette metric analysis identified two distinct microbiome clusters in both the bladder and vagina. One cluster was dominated by Lactobacillus genus while the other was more diverse. Network-based analyses demonstrated that vaginal and bladder microbial networks were different between cases and controls. In the vagina, there were similar numbers of genera and subgroup clusters in each network for cases and controls. However, cases tend to have more unique bacterial co-occurrences. While Bacteroides and Lactobacillus were the central bacteria with the highest betweenness centrality in controls, Aerococcus had the highest centrality in cases and correlated with bacteria commonly associated with bacterial vaginosis. In the bladder, cases have less than half as many network clusters compared to controls. Lactobacillus was the central bacteria in both groups but associated with several known uropathogens in cases. The number of shared bacterial genera between the bladder and the vagina differed between cases and controls, with cases having larger overlap (43%) compared to controls (29%).

Conclusion

Our study shows overlaps in microbial communities of bladder and vagina, with higher overlap in cases. We also identified differences in the bacteria that are central to the overall community structure.

Preliminary Report on Interleukin-22, GM-CSF, and IL-17F in the Pathogenesis of Acute Anterior Uveitis

Purpose:Anterior uveitis is the most common anatomic subset of uveitis. We developed a novel multi-parametric flow cytometry panel to identify immune dysregulation signatures in HLA B27-associated acute anterior uveitis (AAU) and axial spondyloarthritis (AxSpA).Methods: We used fluorescence activated cell sorting to characterize T cell cytokine expression in stimulated T cell subsets from patients with AAU (n = 4) compared to healthy controls (n = 14) or subjects with AxSpA (n = 6).Results: Positive findings among subjects with AAU included a statistically significant increase in stimulated granulocyte-macrophage colony stimulating factor (GM-CSF), IL-17, and IL-22 synthesized by CD8 cells, a trend for stimulated ILC (innate lymphoid cells)-3 cells to synthesize more IL-22 (p = .07), and stimulated MAIT (mucosa associated innate lymphoid cells)-like cells that express the T cell receptor V alpha 7.2 to express IL-17A, IL-17F, and IL-22 in a greater percentage of cells relative to controls. IL-17F, GM- CSF, and IL-22 represent potentially novel targets in AAU.Conclusion: Our report is arguably the first to implicate IL-17F or ILC-3 and MAIT cells in the pathogenesis of AAU.Abbreviations AAU: acute anterior uveitis; AxSpA: axial spondyloarthritis; BASDAI: Bath ankylosing spondylitis disease activity index; CCR: chemokine receptor; DMSO: dimethylsulfoxide; EULAR:European League Against Rheumatism; FACS: fluorescence activated cell sorter; FBS: fetal bovine serum; FSC: orward light scatter; GM-CSF: granulocyte-macrophage colony stimulating factor; HC: healthy control; ILC: innate lymphoid cell; KIR: killer immunoglobulin receptor; MAIT: mucosal associated immune T cell; ND: not detected; NK: natural killer cell; OHSU-Oregon Health & Science University; PBMC: peripheral blood mononuclear cell; SSC: side light scatter; TCR: T cell receptor.

Expression of Cytokines in Porcine Iris, Retina and Choroidal Tissues Stimulated by Microbe-associated Molecular Patterns

PURPOSE

The innate immune system is strongly implicated in the pathogenesis of uveitis. This study was designed to clarify the responses of the innate immune system in uveal tissues.

MATERIALS AND METHODS

We utilized quantitative, real-time RT-PCR to measure mRNA of innate immune system receptors from porcine iris, choroid, and retina tissues. We used RT-PCR for cytokines to evaluate the responses of these tissues to specific ligands or extracts of whole bacteria that activate the innate immune system. We used ELISA for IL-6 on selected choroidal supernatants to confirm that the mRNA measurement correlated with protein levels.

RESULTS

In each of the studied tissues, we detected the expression of important receptors belonging to the innate immune system including dectin-1, TLR4, TLR8, and NOD2. Relative mRNA expression was generally lower in the retina compared to iris or choroid. All three tissues demonstrated upregulation of cytokine mRNA in response to a range of ligands that activate the innate immune system. The measurement of IL-6 protein was consistent with results based on mRNA. Notably, the expression of mRNA for IL-23 was more pronounced than IL-12 in all three tissues after stimulation with various innate immune system ligands.

CONCLUSIONS

These data provide evidence of a potent innate immune response intrinsic to uveal tissues. Specific innate immune system ligands as well as bacterial extracts enhanced the production of several inflammatory cytokines. Furthermore, the observation of higher upregulation of IL-23 mRNA, compared to IL-12 in response to innate immune stimuli, suggested that a local TH17 response might be more robust than a local TH1 response in uveal tissues. Our results expand the understanding as to how the innate immune system may contribute to uveitis.

Alpha-Glucosidase Inhibitors Alter Gut Microbiota and Ameliorate Collagen-Induced Arthritis

Acarose is an anti-diabetic drug and exhibits anti-arthritic effects. We hypothesized that acarbose influences the gut microbiota to affect the course of arthritis and tested this hypothesis in a collagen-induced arthritis (CIA) murine model. Acarbose in drinking water was administered via gastric gavage started prior to or at the time of CIA induction. Gut microbiota were evaluated with 16S rRNA gene sequencing from fecal pellets collected prior to arthritis induction, during onset of arthritis, and after treatment. Immune response was evaluated by measuring changes in T helper-17 (Th17) and T regulatory (Treg) cells in the spleen and intestine, as well as serum cytokine levels. Before induction of CIA, acarbose significantly reduced the incidence of arthritis and attenuated clinical severity of arthritis. The frequency of Th17 cells was significantly decreased in the intestinal lamina propria in acarbose treated mice. Mice that were treated with acarbose showed significantly increased CD4+CD25+Foxp3+ Treg cells with elevation of Helios and CCR6. A remarkable alteration in microbial community was observed in acarbose treated mice. Bacterial diversity and richness in mice with arthritis were significantly lower than those in acarbose treated groups. The frequency of Firmicutes was significantly reduced after arthritis onset but was restored after treatment with acarbose. The frequency of Lactobacillus, Anaeroplasma, Adlercreutzia, RF39 and Corynebacterium was significantly higher in control groups than in acarbose treated, while Oscillospira, Desulfovibrio and Ruminococcus enriched in acarbose treated group. Miglitol, another α-glucosidase inhibitor showed a similar but less potent anti-arthritic effect to that of acarbose. These data demonstrate that acarbose alleviated CIA through regulation of Th17/Treg cells in the intestinal mucosal immunity, which may have resulted from the impact of acarbose on gut microbial community. Inexpensive antidiabetic drugs with an excellent safety profile are potentially useful for managing rheumatoid arthritis.

Novel Inter-omic Analysis Reveals Relationships Between Diverse Gut Microbiota and Host Immune Dysregulation in HLA-B27-Induced Experimental Spondyloarthritis

OBJECTIVE

To define inflammation-related host-microbe interactions in experimental spondyloarthritis (SpA) using novel inter-omic approaches.

METHODS

The relative frequency of gut microbes was determined by 16S ribosomal RNA (rRNA) gene sequencing, and gene expression using RNA-Seq of host tissue. HLA-B27/human β₂ -microglobulin-transgenic (HLA-B27-transgenic) and wild-type rats from dark agouti, Lewis, and Fischer backgrounds were used. Inter-omic analyses using Cytoscape were employed to identify relevant relationships. PICRUSt was used to predict microbial functions based on known metagenomic profiles.

RESULTS

Inter-omic analysis revealed several gut microbes that were strongly associated with dysregulated cytokines driving inflammatory response pathways, such as interleukin-17 (IL-17), IL-23, IL-17, IL-1, interferon-γ (IFNγ), and tumor necrosis factor (TNF). Many microbes were uniquely associated with inflammation in Lewis or Fischer rats, and one was relevant on both backgrounds. Several microbes that were strongly correlated with immune dysregulation were not differentially abundant in HLA-B27-transgenic compared to wild-type controls. A multi-omic network analysis revealed non-overlapping clusters of microbes in Lewis and Fischer rats that were strongly linked to overlapping dysregulated immune/inflammatory genes. Prevotella, Clostridiales, and Blautia were important in Lewis rats, while Akkermansia muciniphila and members of the Lachnospiraceae family dominated in Fischer rats. Inflammation-associated metabolic pathway perturbation (e.g., butanoate, propanoate, lipopolysaccharide, and steroid biosynthesis) was also predicted from both backgrounds.

CONCLUSION

Inter-omic and network analysis of gut microbes and the host immune response in experimental SpA provides an unprecedented view of organisms strongly linked to dysregulated IL-23, IL-17, IL-1, IFNγ, and TNF. Functional similarities between these organisms may explain why animals of different genetic backgrounds exhibit common patterns of immune dysregulation, possibly through perturbation of similar metabolic pathways. These results highlight the power of linking analyses of gut microbiota with the host immune response to gain insights into the role of dysbiotic microbes in SpA beyond taxonomic profiling.

The microbiome and HLA-B27-associated acute anterior uveitis

Acute anterior uveitis (AAU) and the spondyloarthritis (SpA) subtypes ankylosing spondylitis, reactive arthritis and psoriatic arthritis are among the inflammatory diseases affected by the biology of the intestinal microbiome. In this Review, the relationship between AAU, SpA and the microbiome is discussed, with a focus on the major SpA risk gene HLA-B*27 and how it is associated with both intestinal tolerance and the loss of ocular immune privilege that can accompany AAU. We provide four potential mechanisms to account for how dysbiosis, barrier function and immune response contribute to the development of ocular inflammation and the pathogenesis of AAU. Finally, potential therapeutic avenues to target the microbiota for the clinical management of AAU and SpA are outlined.

HLA Alleles Associated With Risk of Ankylosing Spondylitis and Rheumatoid Arthritis Influence the Gut Microbiome

OBJECTIVE

HLA alleles affect susceptibility to more than 100 diseases, but the mechanisms that account for these genotype-disease associations are largely unknown. HLA alleles strongly influence predisposition to ankylosing spondylitis (AS) and rheumatoid arthritis (RA). Both AS and RA patients have discrete intestinal and fecal microbiome signatures. Whether these changes are the cause or consequence of the diseases themselves is unclear. To distinguish these possibilities, we examined the effect of HLA-B27 and HLA-DRB1 RA risk alleles on the composition of the intestinal microbiome in healthy individuals.

METHODS

Five hundred sixty-eight stool and biopsy samples from 6 intestinal sites were collected from 107 healthy unrelated subjects, and stool samples were collected from 696 twin pairs from the TwinsUK cohort. Microbiome profiling was performed using sequencing of the 16S ribosomal RNA bacterial marker gene. All subjects were genotyped using the Illumina CoreExome SNP microarray, and HLA genotypes were imputed from these data.

RESULTS

Associations were observed between the overall microbial composition and both the HLA-B27 genotype and the HLA-DRB1 RA risk allele (P = 0.0002 and P = 0.00001, respectively). These associations were replicated using the stool samples from the TwinsUK cohort (P = 0.023 and P = 0.033, respectively).

CONCLUSION

This study shows that the changes in intestinal microbiome composition seen in AS and RA are at least partially due to effects of HLA-B27 and HLA-DRB1 on the gut microbiome. These findings support the hypothesis that HLA alleles operate to cause or increase the risk of these diseases through interaction with the intestinal microbiome and suggest that therapies targeting the microbiome may be effective in preventing or treating these diseases.

Disruption of Intestinal Homeostasis and Intestinal Microbiota During Experimental Autoimmune Uveitis

Purpose

We determine the changes in intestinal microbiota and/or disruptions in intestinal homeostasis during uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in B10.RIII mice with coadministration of interphotoreceptor retinoid-binding protein peptide (IRBP) and killed mycobacterial antigen (MTB) as an adjuvant. Using 16S rRNA gene sequencing, we looked at intestinal microbial differences during the course of uveitis, as well as intestinal morphologic changes, changes in intestinal permeability by FITC-dextran leakage, antimicrobial peptide expression in the gastrointstinal tract, and T lymphocyte prevalence before and at peak intraocular inflammation.

Results

We demonstrate that increased intestinal permeability and antimicrobial peptide expression in the intestinal tract coincide in timing with increased effector T cells in the mesenteric lymph nodes, during the early stages of uveitis, before peak inflammation. Morphologic changes in the intestine were most prominent during this phase, but also occurred with adjuvant MTB alone, whereas increased intestinal permeability was found only in IRBP-immunized mice that develop uveitis. We also demonstrate that the intestinal microbiota were altered during the course of uveitis, and that some of these changes are specific to uveitic animals, whereas others are influenced by adjuvant MTB alone. Intestinal permeability peaked at 2 weeks, coincident with an increase in intestinal bacterial strain differences, peak lipocalin production, and peak uveitis.

Conclusions

An intestinal dysbiosis accompanies a disruption in intestinal homeostasis in autoimmune uveitis, although adjuvant MTB alone promotes intestinal disruption as well. This may indicate a novel axis for future therapeutic targeting experimentally or clinically.

Fecal transplants in spondyloarthritis and uveitis: ready for a clinical trial?

PURPOSE OF REVIEW

The intestinal microbiome is thought to play a role in the pathogenesis of inflammatory bowel disease (IBD). There are many shared clinical manifestations between IBD and spondyloarthritis (SpA), of which the most common are peripheral arthritis and uveitis. Clinical overlap along with similar genetics between these diseases suggests a possible shared pathogenetic mechanism, which might center on the intestinal microbiota. In this review, we discuss the available evidence that SpA is a microbiome-driven disease and indicate how SpA-associated uveitis could be tied to gut dysbiosis. We conclude by discussing different treatment paradigms targeting the intestinal microbiome for SpA.

RECENT FINDINGS

Recent studies support the growing evidence of the intestinal microbiome as a crucial player in SpA disease pathogenesis. There is emerging evidence that the gut microbiome may play a causative role in uveitis.

SUMMARY

The field is beginning to discover a new level of understanding how the intestinal microbiome is involved in SpA. Treatment methods to alter intestinal microbiota to treat SpA-related diseases are still in its infancy.

Spondyloarthritis, Acute Anterior Uveitis, and Fungi: Updating the Catterall-King Hypothesis

Spondyloarthritis is a common type of arthritis which affects mostly adults. It consists of idiopathic chronic inflammation of the spine, joints, eyes, skin, gut, and prostate. Inflammation is often asymptomatic, especially in the gut and prostate. The HLA-B*27 allele group, which presents intracellular peptides to CD8+ T cells, is by far the strongest risk factor for spondyloarthritis. The precise mechanisms and antigens remain unknown. In 1959, Catterall and King advanced a novel hypothesis explaining the etiology of spondyloarthritis: an as-yet-unrecognized sexually acquired microbe would be causing all spondyloarthritis types, including acute anterior uveitis. Recent studies suggest an unrecognized sexually acquired fungal infection may be involved in prostate cancer and perhaps multiple sclerosis. This warrants reanalyzing the Catterall-King hypothesis based on the current literature. In the last decade, many links between spondyloarthritis and fungal infections have been found. Antibodies against the fungal cell wall component mannan are elevated in spondyloarthritis. Functional polymorphisms in genes regulating the innate immune response against fungi have been associated with spondyloarthritis (CARD9 and IL23R). Psoriasis and inflammatory bowel disease, two common comorbidities of spondyloarthritis, are both strongly associated with fungi. Evidence reviewed here lends credence to the Catterall-King hypothesis and implicates a common fungal etiology in prostate cancer, benign prostatic hyperplasia, multiple sclerosis, psoriasis, inflammatory bowel disease, and spondyloarthritis. However, the evidence available at this time is insufficient to definitely confirm this hypothesis. Future studies investigating the microbiome in relation to these conditions should screen specimens for fungi in addition to bacteria. Future clinical studies of spondyloarthritis should consider antifungals which are effective in psoriasis and multiple sclerosis, such as dimethyl fumarate and nystatin.

Effects of HLA-B27 on Gut Microbiota in Experimental Spondyloarthritis Implicate an Ecological Model of Dysbiosis

OBJECTIVE

To investigate whether HLA-B27-mediated experimental spondyloarthritis (SpA) is associated with a common gut microbial signature, in order to identify potential drivers of pathogenesis.

METHODS

The effects of HLA-B27 on 3 genetic backgrounds, dark agouti (DA), Lewis, and Fischer, were compared, using wild-type littermates and HLA-B7-transgenic Lewis rats as controls. Cecum and colon tissue specimens or contents were collected from the rats at 2, 3-4, and 6-8 months of age, and histologic analysis was performed to assess inflammation, RNA sequencing was used to determine gene expression differences, and 16S ribosomal RNA gene sequencing was used to determine microbiota differences.

RESULTS

Both HLA-B27-transgenic Lewis rats and HLA-B27-transgenic Fischer rats developed gut inflammation, while DA rats were resistant to the effects of HLA-B27, and HLA-B7-transgenic rats were not affected. Immune dysregulation was similar in affected Lewis and Fischer rats and was dominated by activation of interleukin-23 (IL-23)/IL-17, interferon, tumor necrosis factor, and IL-1 cytokines and pathways in the colon and cecum, while DA rats exhibited low-level cytokine dysregulation without inflammation. Gut microbial changes in HLA-B27-transgenic rats were strikingly divergent on the 3 different host genetic backgrounds, including different patterns of dysbiosis in HLA-B27-transgenic Lewis and HLA-B27-transgenic Fischer rat strains, with some overlap. Interestingly, DA rats lacked segmented filamentous bacteria that promote CD4+ Th17 cell development, which may explain their resistance to disease.

CONCLUSION

The effects of HLA-B27 on gut microbiota and dysbiosis in SpA are highly dependent on the host genetic background and/or environment, despite convergence of dysregulated immune pathways. These results implicate an ecological model of dysbiosis, with the effects of multiple microbes contributing to the aberrant immune response, rather than a single or small number of microbes driving pathogenesis.

Intestinal Metabolites Are Profoundly Altered in the Context of HLA-B27 Expression and Functionally Modulate Disease in a Rat Model of Spondyloarthritis

OBJECTIVE

HLA-B27-associated spondyloarthritides are associated with an altered intestinal microbiota and bowel inflammation. We undertook this study to identify HLA-B27-dependent changes in both host and microbial metabolites in the HLA-B27/β2 -microglobulin (β2 m)-transgenic rat and to determine whether microbiota-derived metabolites could impact disease in this major model of spondyloarthritis.

METHODS

Cecal contents were collected from Fischer 344 33-3 HLA-B27/β2 m-transgenic rats and wild-type controls at 6 weeks (before disease) and 16 weeks (with active bowel inflammation). Metabolomic profiling was performed by high-throughput gas and liquid chromatography-based mass spectrometry. HLA-B27/β2 m-transgenic rats were treated with the microbial metabolites propionate or butyrate in drinking water for 10 weeks, and disease activity was subsequently assessed.

RESULTS

Our screen identified 582 metabolites, of which more than half were significantly altered by HLA-B27 expression at 16 weeks. Both microbial and host metabolites were altered, with multiple pathways affected, including those for amino acid, carbohydrate, xenobiotic, and medium-chain fatty acid metabolism. Differences were even observed at 6 weeks, with up-regulation of histidine, tyrosine, spermidine, N-acetylmuramate, and glycerate in HLA-B27/β2 m-transgenic rats. Administration of the short-chain fatty acid propionate significantly attenuated HLA-B27-associated inflammatory disease, although this was not associated with increased FoxP3+ T cell induction or with altered expression of the immunomodulatory cytokines interleukin-10 (IL-10) or IL-33 or of the tight junction protein zonula occludens 1. HLA-B27 expression was also associated with altered host expression of messenger RNA for the microbial metabolite receptors free fatty acid receptor 2 (FFAR2), FFAR3, and niacin receptor 1.

CONCLUSION

HLA-B27 expression profoundly impacts the intestinal metabolome, with changes evident in rats even at age 6 weeks. Critically, we demonstrate that a microbial metabolite, propionate, attenuates development of HLA-B27-associated inflammatory disease. These and other microbiota-derived bioactive mediators may provide novel treatment modalities in HLA-B27-associated spondyloarthritides.

Estrogen protection against EAE modulates the microbiota and mucosal-associated regulatory cells

Sex hormones promote immunoregulatory effects on multiple sclerosis. In the current study we evaluated the composition of the gut microbiota and the mucosal-associated regulatory cells in estrogen or sham treated female mice before and after autoimmune encephalomyelitis (EAE) induction. Treatment with pregnancy levels of estrogen induces changes in the composition and diversity of gut microbiota. Additionally, estrogen prevents EAE-associated changes in the gut microbiota and might promote the enrichment of bacteria that are associated with immune regulation. Our results point to a possible cross-talk between the sex hormones and the gut microbiota, which could promote neuroprotection.

Gut Microbial Alterations Associated With Protection From Autoimmune Uveitis

Purpose

To investigate the contribution of the gut microbiota to the pathogenesis of uveitis.

Methods

Experimental autoimmune uveitis (EAU) in B10.RIII mice was induced using interphotoreceptor binding protein peptide. Mice were treated with oral or intraperitoneal (IP) antibiotics. Effector (Teff) and regulatory (Treg) T lymphocytes were identified using flow cytometry; 16S rRNA gene sequencing and qPCR were performed on gastrointestinal (GI) contents.

Results

Broad-spectrum (four antibiotics given simultaneously) oral, but not IP, antibiotics reduced mean uveitis clinical scores significantly compared with water-treated animals (0.5 vs. 3.0, P < 0.0001 for oral; 3.4 vs. 3.4, P > 0.99 for IP). Both oral metronidazole (P = 0.02) and vancomycin (P < 0.0001) alone decreased inflammation, whereas neomycin (P = 0.7) and ampicillin (P = 0.4) did not change mean uveitis scores. Oral broad-spectrum antibiotics increased Tregs in the GI lamina propria of EAU animals at 1 week, and in extraintestinal lymphoid tissues later, whereas Teff and inflammatory cytokines were reduced. 16S sequencing of GI contents revealed altered microbiota in immunized mice compared with nonimmunized mice, and microbial diversity clustering in EAU mice treated with uveitis-protective antibiotics. Experimental autoimmune uveitis mice also demonstrated gut microbial diversity clustering associated with clinical score severity.

Conclusions

Oral antibiotics modulate the severity of inducible EAU by increasing Tregs in the gut and extraintestinal tissues, as well as decreasing effector T cells and cytokines. 16S sequencing suggests that there may be protective and, conversely, potentially uveitogenic, gut microbiota. These findings may lead to a better understanding of how uveitis can be treated or prevented by modulating the gut microbiome.

Does the Urinary Microbiome Play a Role in Urgency Urinary Incontinence and Its Severity?

OBJECTIVES

Traditionally, the urinary tract has been thought to be sterile in the absence of a clinically identifiable infection. However, recent evidence suggests that the urinary tract harbors a variety of bacterial species, known collectively as the urinary microbiome, even when clinical cultures are negative. Whether these bacteria promote urinary health or contribute to urinary tract disease remains unknown. Emerging evidence indicates that a shift in the urinary microbiome may play an important role in urgency urinary incontinence (UUI). The goal of this prospective pilot study was to determine how the urinary microbiome is different between women with and without UUI. We also sought to identify if characteristics of the urinary microbiome are associated with UUI severity.

METHODS

We collected urine from clinically well-characterized women with UUI (n = 10) and normal bladder function (n = 10) using a transurethral catheter to avoid bacterial contamination from external tissue. To characterize the resident microbial community, we amplified the bacterial 16S rRNA gene by PCR and performed sequencing using Illumina MiSeq. Sequences were processed using the workflow package QIIME. We identified bacteria that had differential relative abundance between UUI and controls using DESeq2 to fit generalized linear models based on the negative binomial distribution. We also identified relationships between the diversity of the urinary microbiome and severity of UUI symptoms with Pearson's correlation coefficient.

RESULTS

We successfully extracted and sequenced bacterial DNA from 95% of the urine samples and identified that there is a polymicrobial community in the female bladder in both healthy controls and women with UUI. We found the relative abundance of 14 bacteria significantly differed between control and UUI samples. Furthermore, we established that an increase in UUI symptom severity is associated with a decrease in microbial diversity in women with UUI.

CONCLUSIONS

Our study provides further characterization of the urinary microbiome in both healthy controls and extensively phenotyped women with UUI. Our results also suggest that the urinary microbiome may play an important role in the pathophysiology of UUI and that the loss of microbial diversity may be associated with clinical severity.

Does the Microbiome Cause B27-related Acute Anterior Uveitis?

The microbiome is strongly implicated in a broad spectrum of immune-mediated diseases. Data support the concept that HLA molecules shape the microbiome. We provide hypotheses to reconcile how HLA-B27 might affect the microbiome and in turn predispose to acute anterior uveitis. These theories include bacterial translocation, antigenic mimicry, and dysbiosis leading to alterations in regulatory and effector T-cell subsets. Received 31 October 2015; revised 7 January 2016; accepted 8 January 2016; published online 22 March 2016.

Aqueous cell differentiation in anterior uveitis using Fourier-domain optical coherence tomography

PURPOSE

The differential diagnosis of a patient presenting with anterior uveitis is broad and can present a diagnostic challenge. In this study, we evaluate the characteristic findings of inflammatory cells on optical coherence tomography (OCT) both in vitro and in vivo.

METHODS

Blood from two healthy volunteers was prepared using standardized methods for cell sorting with a flow cytometer (FASCAria). Neutrophils, lymphocytes, monocytes, and red blood cells were placed in suspension and scanned with a 26-kHz Fourier-domain OCT system (RTVue) with 5-μm axial resolution. Custom software algorithms were used to identify cells based on their reflectance distribution. These algorithms were then applied to OCT images obtained from uveitis patients with active anterior chamber inflammation.

RESULTS

On OCT images the cells appeared as hyperreflective spots. In vitro, cell reflectance was statistically significantly different between all of the cell types (neutrophils, monocytes, lymphocytes, and red blood cells, P < 0.001, Mann-Whitney test). In vivo, the relationship between underlying disease and cell type imaged on OCT was highly statistically significant, with human leukocyte antigen (HLA)-B27-associated uveitis patients having a predominantly polymorphonuclear pattern on OCT and sarcoidosis and inflammatory bowel disease patients having a predominantly mononuclear pattern on OCT (P < 0.001, Fisher's exact test).

CONCLUSIONS

These in vitro and in vivo data demonstrate the potential of OCT to evaluate cells in the anterior chamber of patients noninvasively. Optical coherence tomography may be a useful adjunct to guide the diagnosis and treatment of ocular inflammatory conditions.

The role of the gut and microbes in the pathogenesis of spondyloarthritis

The intestinal microbiota is firmly implicated not only in the pathogenesis of inflammatory bowel disease (IBD) but increasingly also in the development of inflammation at extraintestinal tissue sites. Significant clinical, genetic, immunological, and microbiological overlap exists between IBD and spondyloarthritis (SpA), which indicates that pathophysiological mechanisms are shared between these diseases and may center on the intestinal microbiota. Recently, culture-independent techniques have enabled the microbiota in health and disease to be described in increasing detail. Moreover, functional studies have identified myriad host effector and regulatory pathways that shape or are shaped by this microbial community. We consider the complex relationship between SpA pathogenesis and gut microbes, with a discussion of how manipulation of the gut microbiota itself may be a promising future target for SpA therapy.

HLA-B27 and human β2-microglobulin affect the gut microbiota of transgenic rats

The HLA-B27 gene is a major risk factor for clinical diseases including ankylosing spondylitis, acute anterior uveitis, reactive arthritis, and psoriatic arthritis, but its mechanism of risk enhancement is not completely understood. The gut microbiome has recently been shown to influence several HLA-linked diseases. However, the role of HLA-B27 in shaping the gut microbiome has not been previously investigated. In this study, we characterize the differences in the gut microbiota mediated by the presence of the HLA-B27 gene. We identified differences in the cecal microbiota of Lewis rats transgenic for HLA-B27 and human β2-microglobulin (hβ2m), compared with wild-type Lewis rats, using biome representational in situ karyotyping (BRISK) and 16S rRNA gene sequencing. 16S sequencing revealed significant differences between transgenic animals and wild type animals by principal coordinates analysis. Further analysis of the data set revealed an increase in Prevotella spp. and a decrease in Rikenellaceae relative abundance in the transgenic animals compared to the wild type animals. By BRISK analysis, species-specific differences included an increase in Bacteroides vulgatus abundance in HLA-B27/hβ2m and hβ2m compared to wild type rats. The finding that HLA-B27 is associated with altered cecal microbiota has not been shown before and can potentially provide a better understanding of the clinical diseases associated with this gene.

Does the microbiome play a causal role in spondyloarthritis?

The purpose of this study is to review the potential causal role of the microbiome in the pathogenesis of spondyloarthritis. The method used for the study is literature review. The microbiome plays a major role in educating the immune response. The microbiome is strongly implicated in inflammatory bowel disease which has clinical and genetic overlap with spondyloarthritis. The microbiome also plays a causal role in bowel and joint disease in HLA B27/human beta 2 microglobulin transgenic rats. The mechanism(s) by which HLA B27 could influence the microbiome is unknown but theories include an immune response gene selectivity, an effect on dendritic cell function, or a mucosal immunodeficiency. Bacteria are strongly implicated in the pathogenesis of spondyloarthritis. Studies to understand how HLA B27 affects bacterial ecosystems should be encouraged.

Chronic ethanol consumption modulates growth factor release, mucosal cytokine production, and microRNA expression in nonhuman primates

BACKGROUND

Chronic alcohol consumption has been associated with enhanced susceptibility to both systemic and mucosal infections. However, the exact mechanisms underlying this enhanced susceptibility remain incompletely understood.

METHODS

Using a nonhuman primate model of ethanol (EtOH) self-administration, we examined the impact of chronic alcohol exposure on immune homeostasis, cytokine, and growth factor production in peripheral blood, lung, and intestinal mucosa following 12 months of chronic EtOH exposure.

RESULTS

EtOH exposure inhibited activation-induced production of growth factors hepatocyte growth factor (HGF), granulocyte colony-stimulating factor (G-CSF), and vascular-endothelial growth factor (VEGF) by peripheral blood mononuclear cells (PBMC). Moreover, EtOH significantly reduced the frequency of colonic Th1 and Th17 cells in a dose-dependent manner. In contrast, we did not observe differences in lymphocyte frequency or soluble factor production in the lung of EtOH-consuming animals. To uncover mechanisms underlying reduced growth factor and Th1/Th17 cytokine production, we compared expression levels of microRNAs in PBMC and intestinal mucosa. Our analysis revealed EtOH-dependent up-regulation of distinct microRNAs in affected tissues (miR-181a and miR-221 in PBMC; miR-155 in colon). Moreover, we were able to detect reduced expression of the transcription factors STAT3 and ARNT, which regulate expression of VEGF, G-CSF, and HGF and contain targets for these microRNAs. To confirm and extend these observations, PBMC were transfected with either mimics or antagomirs of miR-181 and miR-221, and protein levels of the transcription factors and growth factors were determined. Transfection of microRNA mimics led to a reduction in both STAT3/ARNT as well as VEGF/HGF/G-CSF levels. The opposite outcome was observed when microRNA antagomirs were transfected.

CONCLUSIONS

Chronic EtOH consumption significantly disrupts both peripheral and mucosal immune homeostasis, and this dysregulation may be mediated by changes in microRNA expression.

Moderate alcohol consumption enhances vaccine-induced responses in rhesus macaques

We have recently shown that chronic alcohol consumption in a rhesus macaque model of ethanol self-administration significantly modulates the serum cytokine profile. In this study, we extended these observations by investigating the impact of chronic ethanol exposure on the immune response to Modified Vaccinia Ankara (MVA). All animals were vaccinated with MVA before ethanol exposure to ethanol and then again after 7 months of 22 h/day of "open-access" drinking of 4% (w/v) ethanol. Our results indicate that animals whose blood ethanol concentration (BEC) chronically exceeded 80 mg/dl had lower CD4 and CD8 T cell proliferation as well as IgG responses following MVA booster than control animals. In contrast, relatively moderate drinkers whose BEC remained below 80 mg/ml exhibited more robust MVA-specific IgG and CD8 T cell responses than controls. To begin to uncover mechanisms underlying the differences in MVA-specific responses between the three groups, we analyzed plasma cytokine levels and microRNA expression in peripheral blood mononuclear cells following MVA booster. Our findings suggest that moderate ethanol consumption results in higher levels of antiviral cytokines and an expression profile of microRNAs linked to CD8 T cell differentiation. In summary, moderate alcohol consumption enhances recall vaccine responses, whereas chronic alcohol intoxication suppresses this response.

T cell responses against structural proteins develop rapidly during acute simian varicella virus infection and are maintained during viral latency (P6133)

Varicella zoster virus (VZV) is the etiological agent of varicella and herpes zoster. Clinical observations suggest that successful control of VZV during both primary infection and reactivation is mediated by cellular rather than humoral immunity. Numerous studies have characterized T cell responses directed against select VZV open reading frames (ORF), but a comprehensive analysis of the T cell response to the entire VZV genome has not yet been conducted. We have shown that intrabronchial inoculation of young rhesus macaques with simian varicella virus (SVV), a homolog of VZV, recapitulates the hallmarks of acute and latent VZV infection in humans. In this study, we characterized the specificity of T cell responses during acute and latent SVV infection. We identified several SVV ORFs targeted by T cell responses in majority of animals examined during both acute and latent infection. We show that structural proteins are targeted by both CD4 and CD8 T cells, and immediate early/early viral proteins are primarily targeted by CD8 T cells. Also, while both CD4 and CD8 T cell responses are detected during acute SVV infection, latent infection elicits primarily CD8 T cell responses. These results suggest that CD4 T cell immunity may wane faster than CD8 T cell immunity. Given the close genome relatedness of SVV and VZV, our studies highlight immunogenic ORFs to be further investigated as potential components of second-generation VZV vaccines designed to boost T cell immunity.

Age-dependent changes in innate immune phenotype and function in rhesus macaques (Macaca mulatta)

Aged individuals are more susceptible to infections due to a general decline in immune function broadly referred to as immune senescence. While age-related changes in the adaptive immune system are well documented, aging of the innate immune system remains less well understood, particularly in nonhuman primates. A more robust understanding of age-related changes in innate immune function would provide mechanistic insight into the increased susceptibility of the elderly to infection. Rhesus macaques have proved a critical translational model for aging research, and present a unique opportunity to dissect age-dependent modulation of the innate immune system. We examined age-related changes in: (i) innate immune cell frequencies; (ii) expression of pattern recognition receptors (PRRs) and innate signaling molecules; (iii) cytokine responses of monocytes and dendritic cells (DC) following stimulation with PRR agonists; and (iv) plasma cytokine levels in this model. We found marked changes in both the phenotype and function of innate immune cells. This included an age-associated increased frequency of myeloid DC (mDC). Moreover, we found toll-like receptor (TLR) agonists lipopolysaccharide (TLR4), fibroblast stimulating ligand-1 (TLR2/6), and ODN2006 (TLR7/9) induced reduced cytokine responses in aged mDC. Interestingly, with the exception of the monocyte-derived TNFα response to LPS, which increased with age, TNFα, IL-6, and IFNα responses declined with age. We also found that TLR4, TLR5, and innate negative regulator, sterile alpha and TIR motif containing protein (SARM), were all expressed at lower levels in young animals. By contrast, absent in melanoma 2 and retinoic acid-inducible gene I expression was lowest in aged animals. Together, these observations indicate that several parameters of innate immunity are significantly modulated by age and contribute to differential immune function in aged macaques.

An innately dangerous balancing act: intestinal homeostasis, inflammation, and colitis-associated cancer

Inflammatory bowel disease (IBD) is characterized by dysregulated immune responses to the intestinal microbiota, and by chronic intestinal inflammation. Several recent studies demonstrate the importance of innate microbial recognition by immune and nonimmune cells in the gut. Paradoxically, either diminished or exacerbated innate immune signaling may trigger the breakdown of intestinal homeostasis, leading to IBD and colitis-associated cancer (CAC). This dichotomy may reflect divergent functional roles for immune sensing in intestinal epithelial cells and leukocytes, which may vary with distinct disease mechanisms.

OX40 is required for regulatory T cell-mediated control of colitis

The immune response in the gastrointestinal tract is a tightly controlled balance between effector and regulatory cell responses. Here, we have investigated the role of OX40 in influencing the balance between conventional T cells and Foxp3+ regulatory T (T reg) cells. Under steady-state conditions, OX40 was required by T reg cells for their accumulation in the colon, but not peripheral lymphoid organs. Strikingly, under inflammatory conditions OX40 played an essential role in T reg cell-mediated suppression of colitis. OX40(-/-) T reg cells showed reduced accumulation in the colon and peripheral lymphoid organs, resulting in their inability to keep pace with the effector response. In the absence of OX40 signaling, T reg cells underwent enhanced activation-induced cell death, indicating that OX40 delivers an important survival signal to T reg cells after activation. As OX40 also promoted the colitogenic Th1 response, its expression on T reg cells may be required for effective competition with OX40-dependent effector responses. These results newly identify a key role for OX40 in the homeostasis of intestinal Foxp3+ T reg cells and in suppression of colitis. These fi ndings should be taken into account when considering OX40 blockade for treatment of IBD.