Intestinal CD4 Research Articles

GPR120 Inhibits Colitis Through Regulation of CD4+ T Cell Interleukin 10 Production

G protein-coupled receptor (GPR) 120 has been implicated in regulating metabolic syndromes with anti-inflammatory function. However, the role of GPR120 in intestinal inflammation is unknown. Here, we investigated whether and how GPR120 regulates CD4+ T cell function to inhibit colitis development. Dextran sodium sulfate (DSS)-induced colitis model, Citrobacter rodentium infection model, and CD4+ T cell adoptive transfer model were used to analyze the role of GPR120 in regulating colitis development. The effect of GPR120 on CD4+ T cell functions was analyzed by RNA sequencing, flow cytometry, and Seahorse metabolic assays. Mice were administered GPR120 agonist for investigating the potential of GPR120 agonist in preventing and treating colitis. Deficiency of GPR120 in CD4+ T cells resulted in more severe colitis in mice upon dextran sodium sulfate insult and enteric infection. Transfer of GPR120-deficient CD4+CD45Rbhi T cells induced more severe colitis in Rag-/- mice with lower intestinal interleukin (IL) 10+CD4+ Tcells. Treatment with the GPR120 agonist CpdA promoted CD4+ T cell production of IL10 by up-regulating Blimp1 and enhancing glycolysis, which was regulated by mTOR. GPR120 agonist-treated wild-type, but not IL10-deficient and Blimp1-deficient, T helper 1 cells induced less severe colitis. Furthermore, oral administration of GPR120 agonist protected mice from intestinal inflammation in both prevention and treatment schemes. Gpr120 expression was positively correlated with Il10 expression in the human colonic mucosa, including patients with inflammatory bowel diseases. Our findings show the role of GPR120 in regulating intestinal CD4+ T cell production of IL10 to inhibit colitis development, which identifies GPR120 as a potential therapeutic target for treating inflammatory bowel diseases.

Mapping the spatial distribution of T cells in repertoire dimension

T cells mediate adaptive immunity in diverse anatomic compartments through recognition of specific antigens via unique T cell receptor (TCR) structures. However, little is known about the spatial distribution of an organism’s TCR repertoire. Here, using high-throughput TCR sequencing (TCRseq), we investigated the TCR repertoires of sixteen tissues in healthy C57B/L6 mice. We found that TCR repertoires generally classified into three categories (lymph nodes, non-lymph node tissues and small intestine) based on sequence similarity. Clonal distribution and diversity analyses showed that small intestine compartment had a more skewed repertoire as compared to lymph nodes and non-lymph node tissues. However, analysis of TRBV and TRBJ gene usage across tissue compartments, as well as comparison of CDR3 length distributions, showed no significant tissue-dependent differences. Interestingly, analysis of clonotype sharing between mice showed that although non-redundant public clonotypes were found more easily in lymph nodes, small intestinal CD4 + T cells harbored more abundant public clonotypes. These findings under healthy physiological conditions offer an important reference dataset, which may contribute to our ability to better manipulate T cell responses against infection and vaccination.

Environmental enteric dysfunction induces regulatory T cells that inhibit local CD4+ T cell responses and impair oral vaccine efficacy

Environmental enteric dysfunction (EED) is a gastrointestinal inflammatory disease caused by malnutrition and chronic infection. EED is associated with stunting in children and reduced efficacy of oral vaccines. To study the mechanisms of oral vaccine failure during EED, we developed a microbiota- and diet-dependent mouse EED model. Analysis of E.coli-labile toxin vaccine-specific CD4+ Tcells in these mice revealed impaired CD4+ Tcell responses in the small intestine and but not the lymph nodes. EED mice exhibited increased frequencies of small intestine-resident RORγT+FOXP3+ regulatory T (Treg) cells. Targeted deletion of RORγT from Treg cells restored small intestinal vaccine-specific CD4 Tcell responses and vaccine-mediated protection upon challenge. However, ablation of RORγT+FOXP3+ Treg cells made mice more susceptible to EED-induced stunting. Our findings provide insight into the poor efficacy of oral vaccines in EED and highlight how RORγT+FOXP3+ Treg cells can regulate intestinal immunity while leaving systemic responses intact.

Mesenteric lymph node priming licenses intestinal CD103+ CD8 tissue-resident memory T cell development

Abstract CD8 tissue-resident memory T (TRM) cells provide front-line protective immunity at barrier tissues; however, mechanisms regulating their development are not completely understood. Priming dictates the migration of effector CD8 T cells to the tissue, while factors in the tissue induce in situ TRM cell differentiation. Whether priming also regulates in situ differentiation of CD8 TRM cells has not been addressed. Here, we demonstrate that T cell priming in the mesenteric lymph nodes (MLN) was the principal determinant of CD103+ CD8 TRM cell differentiation in the intestine. In contrast, CD8 T cells primed in the spleen were inefficient at differentiating into intestinal CD103+ TRM cells. Moreover, both CD103− and CD103+ naïve T cells were highly efficient in differentiating into CD103+ TRM cells in the intestine after priming in the MLN, suggesting preconditioning of naïve T cells by TGF-b during homeostasis had little impact on intestinal CD103+ TRM cell differentiation. We further demonstrate that MLN priming initiated CD103+ CD8 TRM cell signature gene expression and licensed rapid CD103+ CD8 TRM precursor cell differentiation in response to factors in the tissue by providing retinoic acid signaling to CD8 T cells. Thus, MLN priming is specialized to license intestinal CD103+ CD8 TRM cell development.

Src‐phosphorylation at the α1‐Na/K‐ATPase is Associated with Microbiota Community Changes in Diet‐Induced NASH in the Murine

Background Obesity is a rising epidemic, leading to the increased prevalence of NAFLD/NASH (Non-alcoholic Fatty Liver Disease/Non-alcoholic steatohepatitis) that affects 25% of the US population. Gut microbiota has been implicated in NASH for its metabolic and inflammatory alterations, while the inhibition of Src phosphorylation (Src-p) signaling at the α1-Na/K-ATPase has been shown to attenuate established NASH. This study aimed to determine the effects of Src-p inhibition on gut microbiota communities and its association with NASH progression. Methods DNA from the terminal ileum microbiota habitat was obtained from rodents with diet induced NASH and amplified by PCR to develop DNA bacterial phylogenic sequence analysis of wild type and treated animals at 12, 24 and 48 weeks. For animals at 24 weeks, Src-p inhibition was correlated with liver morphological changes, intestinal CD4+/CD8+ ratio, and liver macrophage CD14+ expression. Differences among groups were evaluated by ANOVA/t-test and Principal Component Analysis (PCA). Results Microbiota communities varied significantly at all time points (12, 24 and 48 weeks, p<0.01, PCA), with an increase of Verrucomicrobia and a decrease of Bacteroidetes and Firmicutes in the HFD vs. NMC group. Microbiota communities regressed to their wild type state at 24 weeks through Src-p inhibition (p<0.05). This Src-p inhibited microbiota phenotype was associated with a decrease in liver inflammation and senescence, as well as associated with lower ileum CD4+ & CD8+ T cell levels and higher liver CD14+ expression (p<0.05). Conclusions Intestinal microbiota changes in NASH are significantly associated with Src-phosphorylation at the α1-Na/K-ATPase. Src-p inhibition returned microbiota communities to their wild type, concomitantly observed with amelioration of liver inflammation, cellular senescence, and both adaptive and innate immune responses in the gut and liver.

High salt diet promotes immune cell egress from the small intestine to specific peripheral sites

Immune cell trafficking is essential to fundamental physiological and pathophysiological processes. High salt diet (HSD) heightens immune responses, especially T cell responses. Models of salt-sensitive hypertension show an increased presence of immune cells in the kidney, aortic vasculature, and brain. However, it is not clear if HSD is promoting the expansion of immune cells through intrusion of non-resident cells, expansion of resident cells, or a combination of both. As the small intestine is largely responsible for first-pass absorption of nutrients and fluids, we hypothesized that HSD promotes aberrant small intestinal T cell egress to peripheral sites. To investigate T cell trafficking, we utilized the CAG::KikGreen (KikGR) mice, which ubiquitously express kikume green-red photoconvertible protein from the coral Favia favus, which upon exposure to blue light induces a permanent structural photoconversion from KikGreen to KikRed (KikRd). This model allows identification of cells, by flow cytometry, that migrated from photoconverted tissues to tissues that were not exposed to blue light, indicating trafficking. 8-12-week old male littermate KikGR mice were placed on normal salt diet (0.4% NaCl chow/normal drinking water; NSD) or high salt diet (4.0% NaCl chow/1% NaCl drinking water) for 5 weeks. Three days prior to tissue collection, the small intestine is externalized, exposed to 405nm blue light, replaced into peritoneal cavity, and mice are allowed to recover. Kidneys, small intestinal (SI) lamina propria, colonic lamina propria, spleen, peripheral blood mononuclear cells (PBMCs), renal lymph nodes (rLN), mesenteric lymph nodes (mLN), caudal/iliac lymph nodes (cLN), and subcutaneous inguinal lymph nodes (siLN) were isolated to examine systemic egress of KikRd+ CD4+ TCR+ T cells from the small intestine. Data representative of 2-3 independent experiments were analyzed by Student's T or two-tailed Mann-Whitney U test. Peripheral lymphoid structures that are involved in draining the gut, namely the mLN and cLN show 135% and 574% increases in the frequency of KikRd+ CD4+ T cells in mice on HSD, respectively, (mLN: NSD: 5.391.14 vs HSD: 12.641.93, % of CD4+, p=0.02, n=4-7/group; cLN: NSD: 9.390.71 vs HSD: 63.3510.29, % of CD4+, p=0.009, n=4-6/group). Interestingly, we also found a 159% increase in the frequency of KikRd+CD4+ T cells in the colonic lamina propria of mice on HSD (NSD: 6.920.74 vs HSD: 17.943.42, % of CD4+, p=0.02, n=4-7/group). No differences were found in the frequencies of KikRd+ CD4+ TCR+ T cells in the spleen (p=0.85, n=4-8/group), in circulating PBMCs (p=0.08, n=5-6/group), in siLN (p=0.16, n=5-8/group), kidneys (p=0.16, n=5-8/group) or rLN (n=2/group). This study suggests that SI CD4+ T cells have a migratory bias from the intestine to specific tissue sites induced by HSD. Specifically, HSD promotes small intestinal CD4+ T cell egress or recruitment to the mLN, cLN, and colonic lamina propria over other peripheral sites. Furthermore, as the cLN is adjacent, drains, and provides efferent lymphatic flow to the abdominal aorta, these data suggest potential migration or recruitment of SI CD4+ T cells to seed the aortic vasculature during HSD.

Enhanced Intestinal TGF-β/SMAD-Dependent Signaling in Simian Immunodeficiency Virus Infected Rhesus Macaques.

Transforming growth factor-β signaling (TGF-β) maintains a balanced physiological function including cell growth, differentiation, and proliferation and regulation of immune system by modulating either SMAD2/3 and SMAD7 (SMAD-dependent) or SMAD-independent signaling pathways under normal conditions. Increased production of TGF-β promotes immunosuppression in Human Immunodeficiency Virus (HIV)/Simian Immunodeficiency Virus (SIV) infection. However, the cellular source and downstream events of increased TGF-β production that attributes to its pathological manifestations remain unknown. Here, we have shown increased production of TGF-β in a majority of intestinal CD3−CD20−CD68+ cells from acute and chronically SIV infected rhesus macaques, which negatively correlated with the frequency of jejunum CD4+ T cells. No significant changes in intestinal TGF-β receptor II expression were observed but increased production of the pSMAD2/3 protein and SMAD3 gene expression in jejunum tissues that were accompanied by a downregulation of SMAD7 protein and gene expression. Enhanced TGF-β production by intestinal CD3−CD20−CD68+ cells and increased TGF-β/SMAD-dependent signaling might be due to a disruption of a negative feedback loop mediated by SMAD7. This suggests that SIV infection impacts the SMAD-dependent signaling pathway of TGF-β and provides a potential framework for further study to understand the role of viral factor(s) in modulating TGF-β production and downregulating SMAD7 expression in SIV. Regulation of mucosal TGF-β expression by therapeutic TGF-β blockers may help to create effective antiviral mucosal immune responses.

Intestinal CD8+ T cell responses are abundantly induced early in human development but show impaired cytotoxic effector capacities

Gastrointestinal viral infections are a major global cause of disease and mortality in infants. Cytotoxic CD8+ T cells are critical to achieve viral control. However, studies investigating the development of CD8+ T cell immunity in human tissues early in life are lacking. Here, we investigated the maturation of the CD8+ T cell compartment in human fetal, infant and adult intestinal tissues. CD8+ T cells exhibiting a memory phenotype were already detected in fetal intestines and increased after birth. Infant intestines preferentially harbored effector CCR7−CD45RA−CD127−KLRG1+/− CD8+ T cells compared to tissue-resident memory CD69+CD103+CD8+ T cells detected in adults. Functional cytotoxic capacity, including cytokine and granzyme B production of infant intestinal effector CD8+ T cells was, however, markedly reduced compared to adult intestinal CD8+ T cells. This was in line with the high expression of the inhibitory molecule PD-1 by infant intestinal effector CD8+ T cells. Taken together, we demonstrate that intestinal CD8+ T cell responses are induced early in human development, however exhibit a reduced functionality. The impaired CD8+ T cell functionality early in life contributes to tolerance during foreign antigen exposure after birth, however functions as an immune correlate for the increased susceptibility to gastrointestinal viral infections in infancy.

Immunological Impact of Intestinal T Cells on Metabolic Diseases.

Emerging evidence accumulated over the past several years has uncovered intestinal CD4+ T cells as an essential mediator in modulating intestinal immunity in health and diseases. It has also been increasingly recognized that dietary and microbiota-derived factors play key roles in shaping the intestinal CD4+ T-cell compartment. This review aims to discuss the current understanding on how the intestinal T cell immune responses are disturbed by obesity and metabolic stress. In addition, we review how these changes influence systemic metabolic homeostasis and the T-cell-mediated crosstalk between gut and liver or brain in the progression of obesity and its related diseases. Lastly, we highlight the potential roles of some drugs that target intestinal T cells as a therapeutic treatment for metabolic diseases. A better understanding of the interaction among metabolites, bacterial signals, and T cell immune responses in the gut and their roles in systemic inflammation in metabolic tissues should shed new light on the development of effective treatment of obesity and related disorders.

GPR120 MAINTAINS INTESTINAL HOMEOSTASIS THROUGH REGULATION OF CD4+ T CELL IL-10 PRODUCTION

Abstract Irregular CD4+ effector T cell responses play an essential role in the intestinal inflammation, while IL-10 produced by effector T cells limits their pathogenesis to maintain the intestinal homeostasis. Dietary free fatty acids are actively involved in regulating immune responses, and mammalian G protein-coupled receptor (GPR) 120, a receptor for long-chain fatty acids, has been implicated in metabolic syndrome. However, the effect of GPR120 on intestinal homeostasis is still unknown. Here, we showed that deficiency of GPR120 resulted in more severe colitis in mice induced by dextran sodium sulfate (DSS) and Citrobacter Rodentium. Interestingly, CD4+ T cells expressed a high level of GPR120, and mice specifically lacking GPR120 in CD4+ T cells were more susceptible to DSS-induced colitis. Besides, GPR120-deficient CD45Rbhi CD4+ cells are more colitogenic in Rag-/- mice, in which IL-17 and IFNg producing CD4+ T cells were increased but IL-10 production by CD4+ T cells was reduced. Furthermore, CpdA, the GPR120 agonist, promoted CD4+ T effector cell production of IL-10 through upregulating Blimp1 and inducing glycolysis, which were regulated by mTOR pathway. Besides, docosahexaenoic acid, a dietary long-chain fatty acid, also upregulated the IL-10 production in CD4+ T cells. Additionally, GPR120 agonist-treated Th1 effector cells induced less severe colitis, whereas this protection was absent in Blimp1-deficient Th1 cells. Importantly, oral administration of CpdA protected mice against intestinal inflammation. Thus, our findings demonstrate the roles of dietary fatty acids receptor GPR120 in regulating intestinal CD4+ T cell production of IL-10 and intestinal homeostasis.

Human intestinal tissue-resident memory T cells comprise transcriptionally and functionally distinct subsets

SummaryTissue-resident memory T (TRM) cells provide key adaptive immune responses in infection, cancer, and autoimmunity. However, transcriptional heterogeneity of human intestinal TRM cells remains undefined. Here, we investigate transcriptional and functional heterogeneity of human TRM cells through study of donor-derived TRM cells from intestinal transplant recipients. Single-cell transcriptional profiling identifies two transcriptional states of CD8+ TRM cells, delineated by ITGAE and ITGB2 expression. We define a transcriptional signature discriminating these populations, including differential expression of cytotoxicity- and residency-associated genes. Flow cytometry of recipient-derived cells infiltrating the graft, and lymphocytes from healthy gut, confirm these CD8+ TRM phenotypes. CD8+ CD69+CD103+ TRM cells produce interleukin-2 (IL-2) and demonstrate greater polyfunctional cytokine production, whereas β2-integrin+CD69+CD103− TRM cells have higher granzyme expression. Analysis of intestinal CD4+ T cells identifies several parallels, including a β2-integrin+ population. Together, these results describe the transcriptional, phenotypic, and functional heterogeneity of human intestinal CD4+ and CD8+ TRM cells.

Helicobacter hepaticus is required for immune targeting of bacterial heat shock protein 60 and fatal colitis in mice

ABSTRACT Gut microbiota and the immune system are in constant exchange shaping both host immunity and microbial communities. Here, improper immune regulation can cause inflammatory bowel disease (IBD) and colitis. Antibody therapies blocking signaling through the CD40–CD40L axis showed promising results as these molecules are deregulated in certain IBD patients. To better understand the mechanism, we used transgenic DC-LMP1/CD40 animals with a constitutive CD40-signal in CD11c+ cells, causing a lack of intestinal CD103+ dendritic cells (DCs) and failure to induce regulatory T (iTreg) cells. These mice rapidly develop spontaneous fatal colitis, accompanied by dysbiosis and increased inflammatory IL-17+IFN-γ+ Th17/Th1 and IFN-γ + Th1 cells. In the present study, we analyzed the impact of the microbiota on disease development and detected elevated IgA- and IgG-levels in sera from DC-LMP1/CD40 animals. Their serum antibodies specifically bound intestinal bacteria, and by proteome analysis, we identified a 60 kDa chaperonin GroEL (Hsp60) from Helicobacter hepaticus (Hh) as the main specific antigen targeted in the absence of iTregs. When re-derived to a different Hh-free specific-pathogen-free (SPF) microbiota, mice showed few signs of disease, normal microbiota, and no fatality. Upon recolonization of mice with Hh, the disease developed rapidly. Thus, the present work identifies GroEL/Hsp60 as a major Hh-antigen and its role in disease onset, progression, and outcome in this colitis model. Our results highlight the importance of CD103+ DC- and iTreg-mediated immune tolerance to specific pathobionts to maintain healthy intestinal balance.

Intestinal microbial communities and Holdemanella isolated from HIV+/− men who have sex with men increase frequencies of lamina propria CCR5+ CD4+ T cells

ABSTRACT Men who have sex with men (MSM), regardless of HIV infection status, have an intestinal microbiome that is compositionally distinct from men who have sex with women (MSW) and women. We recently showed HIV-negative MSM have elevated levels of intestinal CD4+ T cells expressing CCR5, a critical co-receptor for HIV. Whether elevated expression of CCR5 is driven by the altered gut microbiome composition in MSM has not been explored. Here we used in vitro stimulation of gut Lamina Propria Mononuclear Cells (LPMCs) with whole intact microbial cells isolated from stool to demonstrate that fecal bacterial communities (FBCs) from HIV-positive/negative MSM induced higher frequencies of CCR5+ CD4+ T cells compared to FBCs from HIV-negative MSW and women. To identify potential microbial drivers, we related the frequency of CCR5+ CD4+ T cells to the abundance of individual microbial taxa in rectal biopsy of HIV-positive/negative MSM and controls, and Holdemanella biformis was strongly associated with increased frequency of CCR5+ CD4+ T cells. We used in vitro stimulation of gut LPMCs with the type strain of H. biformis, a second strain of H. biformis and an isolate of the closely related Holdemanella porci , cultured from either a HIV-positive or a HIV-negative MSM stool. H. porci elevated the frequency of both CCR5+ CD4+ T cells and the ratio of TNF-α/IL-10 Genomic comparisons of the 3 Holdemanella isolates revealed unique cell wall and capsular components, which may be responsible for their differences in immunogenicity. These findings describe a novel mechanism potentially linking intestinal dysbiosis in MSM to HIV transmission and mucosal pathogenesis.

Lactobacillus rhamnosus GG Orchestrates an Antitumor Immune Response.

Background & AimsIn colorectal cancer, approximately 95% of patients are refractory to immunotherapy because of low antitumor immune responses. Therefore, there is an exigent need to develop treatments that increase antitumor immune responses and decrease tumor burden to enhance immunotherapy.MethodsThe gut microbiome has been described as a master modulator of immune responses. We administered the human commensal, Lactobacillus rhamnosus GG (LGG), to mice and characterized the changes in the gut immune landscape. Because the presence of lactobacilli in the gut microbiome has been linked with decreased tumor burden and antitumor immune responses, we also supplemented a genetic and a chemical model of murine intestinal cancer with LGG. For clinical relevance, we therapeutically administered LGG after tumors had formed. We also tested for the requirement of CD8 T cells in LGG-mediated modulation of gut tumor burden.ResultsWe detected increased colonic CD8 T-cell responses specifically in LGG-supplemented mice. The CD8 T-cell induction was dependent on dendritic cell activation mediated via Toll-like receptor-2, thereby describing a novel mechanism in which a member of the human microbiome induces an intestinal CD8 T-cell response. We also show that LGG decreased tumor burden in the murine gut cancer models by a CD8 T-cell–dependent manner.ConclusionsThese data support the potential use of LGG to augment antitumor immune responses in colorectal cancer patients and ultimately for increasing the breadth and efficacy of immunotherapy.

The Effect of Probiotics, Prebiotics, and Synbiotics on CD4 Counts in HIV-Infected Patients: A Systematic Review and Meta-Analysis.

Background Probiotics as a potential adjuvant therapy may improve the restoration of the intestinal CD4+ T-cell population in HIV-infected patients, whereas findings from clinical trials are inconsistent. This systematic review and meta-analysis of randomized controlled trials (RCTs) was performed to quantify the effects of probiotic, prebiotic, and synbiotic supplementation on CD4 counts in HIV-infected patients. Methods We searched PubMed, Embase, Web of Science, Scopus, and the Cochrane Central Register of Controlled Trials for relevant articles published up to March 20, 2020. Two authors independently performed the study selection, data extraction, and risk of bias assessment. Data were pooled by using the random effects model, and weighted mean difference (WMD) was considered the summary effect size. Publication bias was evaluated by a funnel plot and Egger's test. Results The search strategy identified 1712 citations. After screening, a total of 16 RCTs with 19 trials were included in the meta-analysis. Pooling of the extracted data indicated no significant difference between the probiotics/prebiotics/synbiotics and placebo groups on CD4 counts (WMD = 3.86, 95% confidence interval (CI) -24.72 to 32.45, P = 0.791). In subgroup analysis, a significant increase in CD4 counts was found in the study with high risk of bias (WMD = 188, 95% CI 108.74 to 227.26, P ≤ 0.001). Egger's test showed no evidence of significant publication bias (P = 0.936). Conclusions In summary, the evidence for the efficacy of probiotics, prebiotics, and synbiotics in improving HIV-infected patients' CD4 counts as presented in currently published RCTs is insufficient. Therefore, further comprehensive studies are needed to reveal the exact effect of probiotics, prebiotics, and synbiotics on CD4+ cell counts.

T Cell Receptor Is Required for Differentiation, but Not Maintenance, of Intestinal CD4+ Intraepithelial Lymphocytes

The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous Tcell population with cytotoxic and regulatory properties, which can be acquired at the epithelial layer. However, the role of Tcell receptor (TCR) in this process remains unclear. Single-cell transcriptomic analyses revealed distinct clonal expansions between cell states, with CD4+CD8αα+ IELs being one of the least diverse populations. Conditional deletion of TCR on differentiating CD4+ Tcells or of major histocompatibility complex (MHC) class II on intestinal epithelial cells prevented CD4+CD8αα+ IEL differentiation. However, TCR ablation on differentiated CD4+CD8αα+ IELs or long-term cognate antigen withdraw did not affect their maintenance. TCR re-engagement of antigen-specific CD4+CD8αα+ IELs by Listeria monocytogenes did not alter their state but correlated with reduced bacterial invasion. Thus, local antigen recognition is an essential signal for differentiation of CD4+ Tcells at the epithelium, yet differentiated IELs are able to preserve an effector program in the absence of TCR signaling.

Type I IFNs and CD8 T cells increase intestinal barrier permeability after chronic viral infection.

Intestinal barrier leakage constitutes a potential therapeutic target for many inflammatory diseases and represents a disease progression marker during chronic viral infections. However, the causes of altered gut barrier remain mostly unknown. Using murine infection with lymphocytic choriomeningitis virus, we demonstrate that, in contrast to an acute viral strain, a persistent viral isolate leads to long-term viral replication in hematopoietic and mesenchymal cells, but not epithelial cells (IECs), in the intestine. Viral persistence drove sustained intestinal epithelial barrier leakage, which was characterized by increased paracellular flux of small molecules and was associated with enhanced colitis susceptibility. Type I IFN signaling caused tight junction dysregulation in IECs, promoted gut microbiome shifts and enhanced intestinal CD8 T cell responses. Notably, both type I IFN receptor blockade and CD8 T cell depletion prevented infection-induced barrier leakage. Our study demonstrates that infection with a virus that persistently replicates in the intestinal mucosa increases epithelial barrier permeability and reveals type I IFNs and CD8 T cells as causative factors of intestinal leakage during chronic infections.

Dietary Glucose Consumption Promotes RALDH Activity in Small Intestinal CD103+CD11b+ Dendritic Cells

Retinal dehydrogenase (RALDH) enzymatic activities catalyze the conversion of vitamin A to its metabolite Retinoic acid (RA) in intestinal dendritic cells (DCs) and promote immunological tolerance. However, precise understanding of the exogenous factors that act as initial trigger of RALDH activity in these cells is still evolving. By using germ-free (GF) mice raised on an antigen free (AF) elemental diet, we find that certain components in diet are critically required to establish optimal RALDH expression and activity, most prominently in small intestinal CD103+CD11b+ DCs (siLP-DCs) right from the beginning of their lives. Surprisingly, systematic screens using modified diets devoid of individual dietary components indicate that proteins, starch and minerals are dispensable for this activity. On the other hand, in depth comparison between subtle differences in dietary composition among different dietary regimes reveal that adequate glucose concentration in diet is a critical determinant for establishing RALDH activity specifically in siLP-DCs. Consequently, pre-treatment of siLP-DCs, and not mesenteric lymph node derived MLNDCs with glucose, results in significant enhancement in the in vitro generation of induced Regulatory T (iTreg) cells. Our findings reveal previously underappreciated role of dietary glucose concentration in establishing regulatory properties in intestinal DCs, thereby extending a potential therapeutic module against intestinal inflammation.

Alcohol Use Is Associated With Intestinal Dysbiosis and Dysfunctional CD8+ T-Cell Phenotypes in Persons With Human Immunodeficiency Virus.

Inflammation persists among persons with human immunodeficiency virus (PWH) despite effective antiretroviral therapy and may contribute to T-cell dysfunction. Alcohol use is prevalent among PWH and promotes intestinal leak, dysbiosis, and a proinflammatory milieu. Whether alcohol use is associated with T-cell late differentiation remains to be investigated. Data and samples from PWH (N = 359 of 365) enrolled in the New Orleans Alcohol Use in HIV Study were used. Alcohol use was assessed by self-report (Alcohol Use Disorders Identification Test; lifetime alcohol exposure; 30-day Alcohol Timeline Followback) and phosphatidylethanol (PEth) quantitation. In a subset of participants, fecal bacterial content was assessed by ribosomal 16S marker gene deep sequencing and quantitative polymerase chain reaction. Intestinal leak was assessed by fecal-to-plasma α-1-antitrypsin (A1AT) enzyme-linked immunosorbent assay ratio. Peripheral T-cell populations were quantified by flow cytometry. Alcohol Use Disorder Identification Test scores were positively associated with activated-senescent, exhausted, and terminal effector memory CD45RA+CD8+ but not CD4+ T cells (cells/μL) after confounder adjustment (P < .050). Phosphatidylethanol was positively associated with A1AT (P < .050). The PEth and activated-senescent CD8+ were associated with bacterial β-diversity (P < .050) and positively associated with the relative abundance of coabundant Prevotellaceae members (q < .100). Alcohol use among PWH is associated with CD8+ T-cell late differentiation, intestinal leak, and dysbiosis. Alcohol-associated dysbiosis is implicated in CD8+ T-cell senescence.

Exposures to uranium and arsenic alter intraepithelial and innate immune cells in the small intestine of male and female mice

Human exposures to environmental metals, including uranium (U) and arsenic (As) are a global public health concern. Chronic exposures to U and As are linked to many adverse health effects including, immune suppression and autoimmunity. The gastrointestinal (GI) tract is home to many immune cells vital in the maintenance of systemic immune health. However, very little is known about the immunotoxicity of U and As at this site. The present study examined the burden of U and As exposure in the GI tract as well as the resultant immunotoxicity to intraepithelial lymphocytes (IELs) and innate immune cells of the small intestine following chronic drinking water exposures of male and female mice to U (in the form of uranyl acetate, UA) and As (in the form of sodium arsenite, As3+). Exposure to U or As3+ resulted in high levels of U or As in the GI tract of male and female mice, respectively. A reduction of small intestinal CD4+ IELs (TCRαβ+, CD8αα+) was found following As3+ exposure, whereas U produced widespread suppression of CD4− IEL subsets (TCRαβ+ and TCRγδ+). Evaluation of innate immune cell subsets in the small intestinal lamina propria revealed a decrease in mature macrophages, along with a corresponding increase in immature/proinflammatory macrophages following As3+ exposures. These data show that exposures to two prevalent environmental contaminants, U and As produce significant immunotoxicity in the GI tract. Collectively, these findings provide a critical framework for understanding the underlying immune health issues reported in human populations chronically exposed to environmental metals.