Racial and ethnic differences in diagnosis age and blood biomarkers in a pediatric inflammatory bowel disease cohort.

OBJECTIVE: Prompt diagnosis of pediatric-onset inflammatory bowel disease (IBD) is crucial for preventing a complicated disease course; however, it is not well understood how social determinants of health might affect pediatric IBD diagnosis. This study examined differences in diagnosis age, biomarkers of disease severity, and anthropometrics with sociodemographic factors in a pediatric IBD cohort. METHODS: Pediatric IBD patients (n = 114) and their parents/caregivers were enrolled from the Children's of Alabama Pediatric IBD Clinic in Birmingham, Alabama. Primary analyses examined associations of child race and ethnicity, parental income, parental education, single-parent household status, insurance type, and distance to a tertiary pediatric gastroenterology referral center with diagnosis age. Secondary analyses examined differences in biomarker levels, height, and body mass index at the time of diagnosis. RESULTS: Racial and ethnic minority children were diagnosed at an older age compared to Non-Hispanic White children (14.4 ± 0.40 vs. 11.7 ± 0.38 years; p < 0.001), and this trend was robust to adjustment with other sociodemographic variables. Parental attainment of a college education attenuated the link between minority race and ethnicity and the likelihood of older age at diagnosis, while other sociodemographic variables had no moderating effect. Racial and ethnic minority children were 5.7 times more likely to have clinically elevated erythrocyte sedimentation rate at diagnosis compared to Non-Hispanic White children (p = .024). CONCLUSIONS: These results suggest that child race and ethnicity may exert a primary effect on the age at diagnosis with pediatric-onset IBD. This study highlights the need for further research on racial and ethnic disparities to promote health equity in pediatric-onset IBD.

ICOS ligand and IL-10 synergize to promote host-microbiota mutualism.

Genome-wide association studies have identified ICOSLG, which encodes the inducible costimulator ligand (ICOSLG or ICOSL) as a susceptibility locus for inflammatory bowel disease. ICOSL has been implicated in the enhancement of pattern recognition receptor signaling in dendritic cells, induction of IL-10 production by CD4 T cells, and the generation of high-affinity antibodies to specific antigens-all of which can potentially explain its involvement in gastrointestinal inflammation. Here, we show that murine ICOSL deficiency results in significant enrichment of IL-10-producing CD4 T cells particularly in the proximal large intestine. Transient depletion of IL-10-producing cells from adult ICOSL-deficient mice induced severe colonic inflammation that was prevented when mice were first treated with metronidazole. ICOSL-deficient mice displayed reduced IgA and IgG antibodies in the colon mucus and impaired serum antibody recognition of microbial antigens, including flagellins derived from mucus-associated bacteria of the Lachnospiraceae family. Confirming the synergy between ICOSL and IL-10, ICOSL deficiency coupled with CD4-specific deletion of the Il10 gene resulted in juvenile onset colitis that was impeded when pups were fostered by ICOSL-sufficient dams. In this setting, we found that both maternally acquired and host-derived antibodies contribute to the life anti-commensal antibody repertoire that mediates this protection in early life. Collectively, our findings reveal a partnership between ICOSL-dependent anti-commensal antibodies and IL-10 in adaptive immune regulation of the microbiota in the large intestine. Furthermore, we identify ICOSL deficiency as an effective platform for exploring the functions of anti-commensal antibodies in host-microbiota mutualism.

Hedgehog blockade remodels the gut microbiota and the intestinal effector CD8+ T cells in a mouse model of mammary carcinoma.

Given the gut microbiome's rise as a potential frontier in cancer pathogenesis and therapy, leveraging microbial analyses in the study of breast tumor progression and treatment could unveil novel interactions between commensal bacteria and disease outcomes. In breast cancer, the Hedgehog (Hh) signaling pathway is a potential target for treatment due to its aberrant activation leading to poorer prognoses and drug resistance. There are limited studies that have investigated the influences of orally administered cancer therapeutics, such as Vismodegib (a pharmacological, clinically used Hh inhibitor) on the gut microbiota. Using a 4T1 mammary carcinoma mouse model and 16 S rRNA sequencing, we longitudinally mapped alterations in immunomodulating gut microbes during mammary tumor development. Next, we identified changes in the abundance of commensal microbiota in response to Vismodegib treatment of 4T1 mammary tumor-bearing mice. In addition to remodeling gut microbiota, Vismodegib treatment elicited an increase in proliferative CD8+ T cells in the colonic immune network, without any remarkable gastrointestinal-associated side effects. To our knowledge, this is the first study to assess longitudinal changes in the gut microbiome during mammary tumor development and progression. Our study also pioneers an investigation of the dynamic effects of an orally delivered Hh inhibitor on the gut microbiome and the gut-associated immune-regulatory adaptive effector CD8+ T cells. These findings inform future comprehensive studies on the consortium of altered microbes that can impact potential systemic immunomodulatory roles of Vismodegib.

Early life stress in mice alters gut microbiota independent of maternal microbiota inheritance.

Exposure to early life stress (ELS) is associated with a greater risk of chronic disease development including depression and cardiovascular disease. Altered gut microbiota has been linked to both depression and cardiovascular disease in mice and humans. Rodent models of early life neglect are used to characterize the mechanistic links between early life stress (ELS) and the risk of disease later in life. However, little is understood about ELS exposure and the gut microbiota in the young mice and the influence of the maternal inheritance of the gut microbiota. We used a mouse model of ELS, maternal separation with early weaning (MSEW), and normally reared mice to determine whether the neonate microbiota is altered, and if so, are the differences attributable to changes in dam microbiota that are then transmitted to their offspring. Individual amplicon sequence variants (ASVs) displayed differential abundance in the microbiota of MSEW compared with normally reared pups at postnatal day (PD) 28. Additionally, ELS exposure reduced the alpha diversity and altered microbial community composition at PD28. The composition, levels of alpha diversity, and abundance of individual ASVs in the microbiota of dams were similar from MSEW or normally reared cohorts. Thus, the observed shifts in the abundance of individual bacterial ASVs in the neonates and young pups are likely driven by endogenous effects of MSEW in the offspring host and are not due to inherited differences from the dam. This knowledge suggests that exposure to ELS has a direct effect on microbial factors on the risk of chronic disease development.

Cutting Edge: ICOS-Deficient Regulatory T Cells Display Normal Induction of Il10 but Readily Downregulate Expression of Foxp3.

The ICOS pathway has been implicated in the development and functions of regulatory T (Treg) cells, including those producing IL-10. Treg cell-derived IL-10 is indispensable for the establishment and maintenance of intestinal immune homeostasis. We examined the possible involvement of the ICOS pathway in the accumulation of murine colonic Foxp3- and/or IL-10-expressing cells. We show that ICOS deficiency does not impair induction of IL-10 by intestinal CD4 T cells but, instead, triggers substantial reductions in gut-resident and peripherally derived Foxp3+ Treg cells. ICOS deficiency is associated with reduced demethylation of Foxp3 CNS2 and enhanced loss of Foxp3. This instability significantly limits the ability of ICOS-deficient Treg cells to reverse ongoing inflammation. Collectively, our results identify a novel role for ICOS costimulation in imprinting the functional stability of Foxp3 that is required for the retention of full Treg cell function in the periphery.

T Cell-Derived IL-10 Impairs Host Resistance to Mycobacterium tuberculosis Infection.

Tuberculosis (TB), caused by Mycobacterium tuberculosis infection, is a leading cause of mortality and morbidity, causing ∼1.5 million deaths annually. CD4+ T cells and several cytokines, such as the Th1 cytokine IFN-γ, are critical in the control of this infection. Conversely, the immunosuppressive cytokine IL-10 has been shown to dampen Th1 cell responses to M. tuberculosis infection impairing bacterial clearance. However, the critical cellular source of IL-10 during M. tuberculosis infection is still unknown. Using IL-10 reporter mice, we show in this article that during the first 14 d of M. tuberculosis infection, the predominant cells expressing IL-10 in the lung were Ly6C+ monocytes. However, after day 21 postinfection, IL-10-expressing T cells were also highly represented. Notably, mice deficient in T cell-derived IL-10, but not mice deficient in monocyte-derived IL-10, showed a significant reduction in lung bacterial loads during chronic M. tuberculosis infection compared with fully IL-10-competent mice, indicating a major role for T cell-derived IL-10 in TB susceptibility. IL-10-expressing cells were detected among both CD4+ and CD8+ T cells, expressed high levels of CD44 and Tbet, and were able to coproduce IFN-γ and IL-10 upon ex vivo stimulation. Furthermore, during M. tuberculosis infection, Il10 expression in CD4+ T cells was partially regulated by both IL-27 and type I IFN signaling. Together, our data reveal that, despite the multiple immune sources of IL-10 during M. tuberculosis infection, activated effector T cells are the major source accounting for IL-10-induced TB susceptibility.

Intestinal effector T cells in health and disease.

Crohn's disease and ulcerative colitis are the two major forms of chronic relapsing inflammatory disorders of the human intestines collectively referred to as inflammatory bowel disease (IBD). Though a complex set of autoinflammatory disorders that can be precipitated by diverse genetic and environmental factors, a feature that appears common to IBD pathogenesis is a dysregulated effector T cell response to the commensal microbiota. Due to the heightened effector T cell activity in IBD, developmental and functional pathways that give rise to these cells are potential targets for therapeutic intervention. In this review, we highlight recent advances in our understanding of effector T cell biology in the context of intestinal immune regulation and speculate on their potential clinical significance.

Late developmental plasticity in the T helper 17 lineage.

Development of T helper (Th) 17 cells requires transforming growth factor (TGF)-beta and interleukin (IL)-6 and is independent of the Th1 pathway. Although T cells that produce interferon (IFN)-gamma are a recognized feature of Th17 cell responses, mice deficient for STAT4 and T-bet-two prototypical Th1 transcription factors-are protected from autoimmunity associated with Th17 pathogenesis. To examine the fate and pathogenic potential of Th17 cells and origin of IFN-gamma-producing T cells that emerge during Th17 immunity, we developed IL-17F reporter mice that identify cells committed to expression of IL-17F and IL-17A. Th17 cells required TGF-beta for sustained expression of IL-17F and IL-17A. In the absence of TGF-beta, both IL-23 and IL-12 acted to suppress IL-17 and enhance IFN-gamma production in a STAT4- and T-bet-dependent manner, albeit with distinct efficiencies. These results support a model of late Th17 developmental plasticity with implications for autoimmunity and host defense.

Reciprocal interactions of the intestinal microbiota and immune system.

The emergence of the adaptive immune system in vertebrates set the stage for evolution of an advanced symbiotic relationship with the intestinal microbiota. The defining features of specificity and memory that characterize adaptive immunity have afforded vertebrates the mechanisms for efficiently tailoring immune responses to diverse types of microbes, whether to promote mutualism or host defence. These same attributes can put the host at risk of immune-mediated diseases that are increasingly linked to the intestinal microbiota. Understanding how the adaptive immune system copes with the remarkable number and diversity of microbes that colonize the digestive tract, and how the system integrates with more primitive innate immune mechanisms to maintain immune homeostasis, holds considerable promise for new approaches to modulate immune networks to treat and prevent disease.

Th17 cells give rise to Th1 cells that are required for the pathogenesis of colitis.

Th17 cells reactive to the enteric microbiota are central to the pathogenesis of certain types of inflammatory bowel disease. However, Th17 cells display substantial developmental plasticity, such that some progeny of Th17 cell precursors retain a predominantly IL-17A(+) phenotype, whereas others extinguish IL-17 expression and acquire expression of IFN-γ, giving rise to "Th1-like" cells. It remains unclear what role these subsets play in inflammatory bowel disease. Using a Th17 transfer model of colitis, we found that IFN-γ-deficient Th17 cells retained an IL-17A(+) phenotype and were unable to induce colitis in recipients. Development of disease required the transition of a subset of Th17 precursors to Th1-like cells and was contingent on the expression of both Stat4 and T-bet, but not the IL-12 or IFN-γ receptors. Moreover, Th17 cells could provide "help" for the development of pathogenic Th1 cells from naïve precursors. These results indicate that Th17 cells are potent mediators of colitis pathogenesis by dual mechanisms: by directly transitioning to Th1-like cells and by supporting the development of classic Th1 cells.

Colonization potential to reconstitute a microbe community in patients detected early after fecal microbe transplant for recurrent C. difficile.

BACKGROUND: Fecal microbiota transplants (FMT) are an effective treatment for patients with gut microbe dysbiosis suffering from recurrent C. difficile infections. To further understand how FMT reconstitutes the patient's gut commensal microbiota, we have analyzed the colonization potential of the donor, recipient and recipient post transplant fecal samples using transplantation in gnotobiotic mice. RESULTS: A total of nine samples from three human donors, recipient's pre and post FMT were transplanted into gnotobiotic mice. Microbiome analysis of three donor fecal samples revealed the presence of a high relative abundance of commensal microbes from the family Bacteriodaceae and Lachnospiraceae that were almost absent in the three recipient pre FMT fecal samples (<0.01%). The microbe composition in gnotobiotic mice transplanted with the donor fecal samples was similar to the human samples. The recipient samples contained Enterobacteriaceae, Lactobacillaceae, Enterococcaceae in relative abundance of 43, 11, 8%, respectively. However, gnotobiotic mice transplanted with the recipient fecal samples had an average relative abundance of unclassified Clostridiales of 55%, approximately 7000 times the abundance in the recipient fecal samples prior to transplant. Microbiome analysis of fecal samples from the three patients early (2-4 weeks) after FMT revealed a microbe composition with the relative abundance of both Bacteriodaceae and Lachnospiraceae that was approximately 7% of that of the donor. In contrast, gnotobioitc mice transplanted with the fecal samples obtained from the three at early times post FMT revealed increases in the relative abundance of Bacteriodaceae and Lachnospiraceae microbe compositions to levels similar to the donor fecal samples. Furthermore, the unclassified Clostridiales in the recipient samples post FMT was reduced to an average of 10%. CONCLUSION: We have used transplantation into gnotobiotic mice to evaluate the colonization potential of microbiota in FMT patients early after transplant. The commensal microbes present at early times post FMT out competed non-commensal microbes (e.g. such as unclassified Clostridiales) for niche space. The selective advantage of these commensal microbes to occupy niches in the gastrointestinal tract helps to explain the success of FMT to reconstitute the gut microbe community of patients with recurrent C. difficile infections.

IL-22-producing neutrophils contribute to antimicrobial defense and restitution of colonic epithelial integrity during colitis.

IL-22 plays an important role in mucosal epithelial cell homeostasis. Using a dextran sodium sulfate-induced mouse model of acute colitis, we observed an IL-23-dependent up-regulation of IL-22 in the middle and distal colon at the onset of epithelial cell damage. This heightened IL-22 correlated with an influx of innate immune cells, suggesting an important role in colonic epithelial protection. Freshly isolated colon-infiltrating neutrophils produced IL-22 contingent upon IL-23 signaling, and IL-22 production was augmented by TNF-α. Importantly, the depletion of neutrophils resulted in diminished IL-22 levels in the colon, and the transfer of IL-22-competent neutrophils to Il22a-deficient mice protected the colonic epithelium from dextran sodium sulfate-induced damage. In addition, IL-22-producing neutrophils targeted colonic epithelial cells to up-regulate the antimicrobial peptides, RegIIIß and S100A8. This study establishes a role for neutrophils in providing IL-22-dependent mucosal epithelial support that contributes to the resolution of colitis.

Early Life Stress in Mice Leads to Impaired Colonic Corticosterone Production and Prolonged Inflammation Following Induction of Colitis.

BACKGROUND: Early life stress (ELS) is an environmental trigger believed to promote increased risk of IBD. Our goal was to identify mechanisms whereby ELS in mice affects susceptibility to and/or severity of gut inflammation. METHODS: We utilized 2 published animal models of ELS. In the first model, newborn mice were separated from the dam daily for 4 to 8 hours starting on postnatal day 2 and then weaned early on postnatal day 17. Control mice were left undisturbed with the dams until weaning on postnatal day 21. In the second model, dams were fed dexamethasone or vehicle ad libitum in drinking water on postpartum days 1 to 14. Plasma and colonic corticosterone were measured in juvenile and adult mice. Colitis was induced in 4-week-old mice via intraperitoneal injection of interleukin (IL)-10 receptor blocking antibody every 5 days for 15 days. Five or 15 days later, colitis scores and transcripts for Tnf, glucocorticoid receptors, and steroidogenic enzymes were measured. RESULTS: Mice exposed to ELS displayed reduced plasma and colonic corticosterone. Control animals showed improvements in indices of inflammation following cessation of interleukin-10 receptor blockade, whereas ELS-exposed animals maintained high levels of Tnf and histological signs of colitis. In colitic animals, prior exposure to ELS was associated with significantly lower expression of genes associated with corticosterone synthesis and responsiveness. Finally, TNF stimulation of colonic crypt cells from ELS mice led to increased inhibition of corticosterone synthesis. CONCLUSIONS: Our study identifies impaired local glucocorticoid production and responsiveness as a potential mechanism whereby ELS predisposes to chronic colitis in susceptible hosts.

Using 2 distinct animal models, this study shows that in mice, early life stress leads to reduced colonic corticosterone and that induction of colitis after stress removal results in reduced transcription of glucocorticoid synthesis genes, increased Tnf, and enhanced chronicity of intestinal inflammation.

Lineage-specific effects of 1,25-dihydroxyvitamin D(3) on the development of effector CD4 T cells.

Vitamin D deficiency is implicated in autoimmune disease. We therefore evaluated the effects of 1α,25-dihydroxyvitamin D(3) (1,25-D(3)), the active form of vitamin D, on the development of T helper 1 (Th1), Th17, and Th9 cells, which are implicated in the pathogenesis of different types of autoimmunity. 1,25-D(3) compromised the development of Th17 and Th9 cells, including IL-22-expressing cells while simultaneously increasing the frequency of IL-10-competent cells. Relative to Th17 and Th9 cells, the effects of 1,25-D(3) on Th1 cells were modest, reflecting the significantly reduced levels of the receptor for vitamin D in this lineage. The use of cells deficient in IL-10 or antibodies that block IL-10 signaling abolished the inhibitory effect of 1,25-D(3) on Th9 cells but had no effect on inhibition of Th17 cell frequencies. Thus, the induction of IL-10 in cultures of Th9 cells is an important mechanism by which 1,25-D(3) compromises Th9 development but does not explain inhibition of Th17 cells. A survey of select representatives of the Th17 transcriptome revealed that the levels of mRNA that encode RORγt, IL-17A, IL-17F, IL-23R, and IL-22, were reduced by 1,25-D(3), whereas IL-21 and aryl hydrocarbon receptor mRNA remained unchanged. These data suggest that vitamin D deficiency may promote autoimmunity by favoring the inordinate production of Th17 and Th9 cells at the expense of regulatory IL-10-producing T cells.

Diversity in the contribution of interleukin-10 to T-cell-mediated immune regulation.

Recent progress in our understanding of mechanisms by which the immunosuppressive cytokine interleukin-10 (IL-10) participates in an ever-increasing diversity of T-cell lineages to maintain immune homeostasis has broadened the framework for defining regulatory and effector T cells and has blurred the lines between them. In this review, we highlight established and emerging roles for IL-10 produced by distinct CD4(+) T-cell lineages that underlie its non-redundant role in curbing immune responses to the intestinal microbiota at steady state and its role to limit T-cell-driven inflammation in responses to pathogens.

Mucus, commensals, and the immune system.

The immune system in the large intestine is separated from commensal microbes and comparatively rare enteric pathogens by a monolayer of diverse epithelial cells overlaid with a compact and adherent inner mucus layer and a looser outer mucus layer. Microorganisms, collectively referred to as the mucus-associated (MA) microbiota, physically inhabit this mucus barrier, resulting in a dynamic and incessant dialog to maintain both spatial segregation and immune tolerance. Recent major findings reveal novel features of the crosstalk between the immune system and mucus-associated bacteria in health and disease, as well as disease-related peripheral immune signatures indicative of host responses to these organisms. In this brief review, we integrate these novel observations into our overall understanding of host-microbiota mutualism at the colonic mucosal border and speculate on the significance of this emerging knowledge for our understanding of the prevention, development, and progression of chronic intestinal inflammation.

Hydroxyproline stimulates inflammation and reprograms macrophage signaling in a rat kidney stone model.

Meals rich in oxalate are associated with calcium oxalate (CaOx) kidney stone disease. Hydroxy-L-proline (HLP) is an oxalate precursor found in milk and collagen-containing foods. HLP has been shown to induce CaOx crystal formation in rodents. The purpose of this study was to evaluate the effect of HLP induced oxalate levels on inflammation and renal leukocytes during crystal formation. Male Sprague-Dawley rats (6-8 weeks old) were fed a control diet containing no oxalate for 3 days before being randomized to continue the control diet or 5% HLP for up to 28 days. Blood, 24 h urine, and kidneys were collected on Days 0, 7, 14, or 28. Urinary oxalate levels, crystal deposition, and renal macrophage markers were evaluated using ion chromatography-mass spectrometry, immunohistochemistry, and qRT-PCR. Renal leukocytes were assessed using flow cytometry and RNA-sequencing. HLP feeding increased urinary oxalate levels and renal crystal formation in animals within 7 days. HLP also increased renal macrophage populations on Days 14 and 28. Transcriptome analysis revealed that renal macrophages from animals fed HLP for 7 days were involved in inflammatory response and disease, stress response to LPS, oxidative stress, and immune cell trafficking. Renal macrophages isolated on Day 14 were involved in cell-mediated immunological pathways, ion homeostasis, and inflammatory response. Collectively, these findings suggest that HLP-mediated oxalate levels induce markers of inflammation, leukocyte populations, and reprograms signaling pathways in macrophages in a time-dependent manner. Additional studies investigating the significance of oxalate on renal macrophages could aid in our understanding of kidney stone formation.

Pirfenidone increases IL-10 and improves acute pancreatitis in multiple clinically relevant murine models.

Despite decades of research, there is no specific therapy for acute pancreatitis (AP). In the current study, we have evaluated the efficacy of pirfenidone, an antiinflammatory and antifibrotic agent that is approved by the FDA for treatment of idiopathic pulmonary fibrosis (IPF), in ameliorating local and systemic injury in AP. Our results suggest that treatment with pirfenidone in therapeutic settings (e.g., after initiation of injury), even when administered at the peak of injury, reduces severity of local and systemic injury and inflammation in multiple models of AP. In vitro evaluation suggests that pirfenidone decreases cytokine release from acini and macrophages and disrupts acinar-macrophage crosstalk. Therapeutic pirfenidone treatment increases IL-10 secretion from macrophages preceding changes in histology and modulates the immune phenotype of inflammatory cells with decreased levels of inflammatory cytokines. Antibody-mediated IL-10 depletion, use of IL-10-KO mice, and macrophage depletion experiments confirmed the role of IL-10 and macrophages in its mechanism of action, as pirfenidone was unable to reduce severity of AP in these scenarios. Since pirfenidone is FDA approved for IPF, a trial evaluating the efficacy of pirfenidone in patients with moderate to severe AP can be initiated expeditiously.

CD4+ T cell activation and concomitant mTOR metabolic inhibition can ablate microbiota-specific memory cells and prevent colitis.

Microbiota-reactive CD4+ T memory (TM) cells are generated during intestinal infections and inflammation, and can revert to pathogenic CD4+ T effector (TE) cells, resulting in chronicity of inflammatory bowel disease (IBD). Unlike TE cells, TM cells have a low rate of metabolism unless they are activated by reencountering cognate antigen. Here, we show that the combination of cell activation and metabolic checkpoint inhibition (CAMCI), by targeting key metabolic regulators mTORC and AMPK, resulted in cell death and anergy, but enhanced the induction of the regulatory subset. Parenteral application of this treatment with a synthetic peptide containing multiple flagellin T cell epitopes (MEP1) and metabolic inhibition successfully prevented the development of CD4+ T cell-driven colitis. Microbiota-specific CD4+ T cells, especially the pathogenic TE subsets, were decreased 10-fold in the intestinal lamina propria. Furthermore, using the CAMCI strategy, we were able to prevent antigen-specific TM cell formation upon initial antigen encounter, and ablate existing TM cells upon reactivation in mice, leading to an altered transcriptome in the remaining CD4+ T cells after ablation. Microbiota flagellin-specific CD4+ T cells from patients with Crohn's disease were ablated in a similar manner after CAMCI in vitro, with half of the antigen-specific T cells undergoing cell death. These results indicate that parenteral activation of microbiota-specific CD4+ T cells with concomitant metabolic inhibition is an effective way to ablate pathogenic CD4+ TM cells and to induce T regulatory (Treg) cells that provide antigen-specific and bystander suppression, supporting a potential immunotherapy to prevent or ameliorate IBD.