Serine metabolism is crucial for cGAS-STING signaling and viral defense control in the gut

Inflammatory bowel diseases are characterized by the chronic relapsing inflammation of the gastrointestinal tract. While the molecular causality between endoplasmic reticulum (ER) stress and intestinal inflammation is widely accepted, the metabolic consequences of chronic ER stress on the pathophysiology of IBD remain unclear. By using in vitro, in vivo models, and patient datasets, we identified a distinct polarization of the mitochondrial one-carbon metabolism and a fine-tuning of the amino acid uptake in intestinal epithelial cells tailored to support GSH and NADPH metabolism upon ER stress. This metabolic phenotype strongly correlates with IBD severity and therapy response. Mechanistically, we uncover that both chronic ER stress and serine limitation disrupt cGAS-STING signaling, impairing the epithelial response against viral and bacterial infection and fueling experimental enteritis. Consequently, the antioxidant treatment restores STING function and virus control. Collectively, our data highlight the importance of serine metabolism to allow proper cGAS-STING signaling and innate immune responses upon gut inflammation.

Intestinal IL-22RA1 signaling regulates intrinsic and systemic lipid and glucose metabolism to alleviate obesity-associated disorders

IL-22 is critical for ameliorating obesity-induced metabolic disorders. However, it is unknown where IL-22 acts to mediate these outcomes. Here we examine the importance of tissue-specific IL-22RA1 signaling in mediating long-term high fat diet (HFD) driven metabolic disorders. To do so, we generated intestinal epithelium-, liver-, and white adipose tissue (WAT)-specific Il22ra1 knockout and littermate control mice. Intestinal epithelium- and liver-specific IL-22RA1 signaling upregulated systemic glucose metabolism. Intestinal IL-22RA1 signaling also mediated liver and WAT metabolism in a microbiota-dependent manner. We identified an association between Oscillibacter and elevated WAT inflammation, likely induced by Mmp12 expressing macrophages. Mechanistically, transcription of intestinal lipid metabolism genes is regulated by IL-22 and potentially IL-22-induced IL-18. Lastly, we show that Paneth cell-specific IL-22RA1 signaling, in part, mediates systemic glucose metabolism after HFD. Overall, these results elucidate a key role of intestinal epithelium-specific IL-22RA1 signaling in regulating intestinal metabolism and alleviating systemic obesity-associated disorders.

IL-17-driven induction of Paneth cell antimicrobial functions protects the host from microbiota dysbiosis and inflammation in the ileum

Interleukin (IL)-17 protects epithelial barriers by inducing the secretion of antimicrobial peptides. However, the effect of IL-17 on Paneth cells (PCs), the major producers of antimicrobial peptides in the small intestine, is unclear. Here, we show that the targeted ablation of the IL-17 receptor (IL-17R) in PCs disrupts their antimicrobial functions and decreases the frequency of ileal PCs. These changes become more pronounced after colonization with IL-17 inducing segmented filamentous bacteria. Mice with PCs that lack IL-17R show an increased inflammatory transcriptional profile in the ileum along with the severity of experimentally induced ileitis. These changes are associated with a decrease in the diversity of gut microbiota that induces a severe ileum pathology upon transfer to genetically susceptible mice, which can be prevented by the systemic administration of IL-17a/f in microbiota recipients. In an exploratory analysis of a small cohort of pediatric patients with Crohn's disease, we have found that a portion of these patients exhibits a low number of lysozyme-expressing ileal PCs and a high ileitis severity score, resembling the phenotype of mice with IL-17R-deficient PCs. Our study identifies IL-17R-dependent signaling in PCs as an important mechanism that maintains ileal homeostasis through the prevention of dysbiosis.

IL-17RA-signaling in Lgr5+ intestinal stem cells induces expression of transcription factor ATOH1 to promote secretory cell lineage commitment

The Th17 cell-lineage-defining cytokine IL-17A contributes to host defense and inflammatory disease by coordinating multicellular immune responses. The IL-17 receptor (IL-17RA) is expressed by diverse intestinal cell types, and therapies targeting IL-17A induce adverse intestinal events, suggesting additional tissue-specific functions. Here, we used multiple conditional deletion models to identify a role for IL-17A in secretory epithelial cell differentiation in the gut. Paneth, tuft, goblet, and enteroendocrine cell numbers were dependent on IL-17A-mediated induction of the transcription factor ATOH1 in Lgr5+ intestinal epithelial stem cells. Although dispensable at steady state, IL-17RA signaling in ATOH1+ cells was required to regenerate secretory cells following injury. Finally, IL-17A stimulation of human-derived intestinal organoids that were locked into a cystic immature state induced ATOH1 expression and rescued secretory cell differentiation. Our data suggest that the cross talk between immune cells and stem cells regulates secretory cell lineage commitment and the integrity of the mucosa.

Epithelial X-Box Binding Protein 1 Coordinates Tumor Protein p53-Driven DNA Damage Responses and Suppression of Intestinal Carcinogenesis

BACKGROUND & AIMS

Throughout life, the intestinal epithelium undergoes constant self-renewal from intestinal stem cells. Together with genotoxic stressors and failing DNA repair, this self-renewal causes susceptibility toward malignant transformation. X-box binding protein 1 (XBP1) is a stress sensor involved in the unfolded protein response (UPR). We hypothesized that XBP1 acts as a signaling hub to regulate epithelial DNA damage responses.

METHODS

Data from The Cancer Genome Atlas were analyzed for association of XBP1 with colorectal cancer (CRC) survival and molecular interactions between XBP1 and p53 pathway activity. The role of XBP1 in orchestrating p53-driven DNA damage response was tested in vitro in mouse models of chronic intestinal epithelial cell (IEC) DNA damage (Xbp1/H2bfl/fl, Xbp1ΔIEC, H2bΔIEC, H2b/Xbp1ΔIEC) and via orthotopic tumor organoid transplantation. Transcriptome analysis of intestinal organoids was performed to identify molecular targets of Xbp1-mediated DNA damage response.

RESULTS

In The Cancer Genome Atlas data set of CRC, low XBP1 expression was significantly associated with poor overall survival and reduced p53 pathway activity. In vivo, H2b/Xbp1ΔIEC mice developed spontaneous intestinal carcinomas. Orthotopic tumor organoid transplantation revealed a metastatic potential of H2b/Xbp1ΔIEC-derived tumors. RNA sequencing of intestinal organoids (H2b/Xbp1fl/fl, H2bΔIEC, H2b/Xbp1ΔIEC, and H2b/p53ΔIEC) identified a transcriptional program downstream of p53, in which XBP1 directs DNA-damage-inducible transcript 4-like (Ddit4l) expression. DDIT4L inhibits mechanistic target of rapamycin-mediated phosphorylation of 4E-binding protein 1. Pharmacologic mechanistic target of rapamycin inhibition suppressed epithelial hyperproliferation via 4E-binding protein 1.

CONCLUSIONS

Our data suggest a crucial role for XBP1 in coordinating epithelial DNA damage responses and stem cell function via a p53-DDIT4L-dependent feedback mechanism.

Paneth Cell Alertness to Pathogens Maintained by Vitamin D Receptors

BACKGROUND AND AIMS

Vitamin D exerts a regulatory role over mucosal immunity via the vitamin D receptor (VDR). Although Paneth cells and their products are known to regulate the commensal and pathogenic microbiota, the role that VDRs in Paneth cells play in these responses is unknown.

METHODS

We identified the decreased intestinal VDR significantly correlated with reduction of an inflammatory bowel disease risk gene ATG16L1 and Paneth cell lysozymes in patients with Crohn's disease. We generated Paneth cell-specific VDR knockout (VDR^ΔPC) mice to investigate the molecular mechanisms.

RESULTS

Lysozymes in the Paneth cells were significantly decreased in the VDR^ΔPC mice. Isolated VDR^ΔPC Paneth cells exhibited weakened inhibition of pathogenic bacterial growth and displayed reduced autophagic responses. VDR^ΔPC mice had significantly higher inflammation after Salmonella infections. VDR^ΔPC mice also showed high susceptibility to small intestinal injury induced by indomethacin, a nonsteroidal anti-inflammatory drug. Co-housing of VDR^ΔPC and VDR^lox mice made the VDR^ΔPC less vulnerable to dextran sulfate sodium colitis, suggesting the transmission of protective bacterial from the VDR^lox mice. Thus, a lack of VDR in Paneth cells leads to impaired antibacterial activities and consequently increased inflammatory responses. Genetically and environmentally regulated VDRs in the Paneth cells may set the threshold for the development of chronic inflammation, as observed in inflammatory bowel diseases.

CONCLUSIONS

We provide new insights into the tissue-specific functions of VDRs in maintaining Paneth cell alertness to pathogens in intestinal disorders. Targeting the VDR affects multiple downstream events within Paneth cells that inhibit intestinal inflammation and establish host defense against enteropathogens.

Cdk5rap3 is essential for intestinal Paneth cell development and maintenance

Intestinal Paneth cells are professional exocrine cells that play crucial roles in maintenance of homeostatic microbiome, modulation of mucosal immunity, and support for stem cell self-renewal. Dysfunction of these cells may lead to the pathogenesis of human diseases such as inflammatory bowel disease (IBD). Cdk5 activator binding protein Cdk5rap3 (also known as C53 and LZAP) was originally identified as a binding protein of Cdk5 activator p35. Although previous studies have indicated its involvement in a wide range of signaling pathways, the physiological function of Cdk5rap3 remains largely undefined. In this study, we found that Cdk5rap3 deficiency resulted in very early embryonic lethality, indicating its indispensable role in embryogenesis. To further investigate its function in the adult tissues and organs, we generated intestinal epithelial cell (IEC)-specific knockout mouse model to examine its role in intestinal development and tissue homeostasis. IEC-specific deletion of Cdk5rap3 led to nearly complete loss of Paneth cells and increased susceptibility to experimentally induced colitis. Interestingly, Cdk5rap3 deficiency resulted in downregulation of key transcription factors Gfi1 and Sox9, indicating its crucial role in Paneth cell fate specification. Furthermore, Cdk5rap3 is highly expressed in mature Paneth cells. Paneth cell-specific knockout of Cdk5rap3 caused partial loss of Paneth cells, while inducible acute deletion of Cdk5rap3 resulted in disassembly of the rough endoplasmic reticulum (RER) and abnormal zymogen granules in the mature Paneth cells, as well as loss of Paneth cells. Together, our results provide definitive evidence for the essential role of Cdk5rap3 in Paneth cell development and maintenance.

Activating Transcription Factor 6 Mediates Inflammatory Signals in Intestinal Epithelial Cells Upon Endoplasmic Reticulum Stress

BACKGROUND & AIMS

Excess and unresolved endoplasmic reticulum (ER) stress in intestinal epithelial cells (IECs) promotes intestinal inflammation. Activating transcription factor 6 (ATF6) is one of the signaling mediators of ER stress. We studied the pathways that regulate ATF6 and its role for inflammation in IECs.

METHODS

We performed an RNA interference screen, using 23,349 unique small interfering RNAs targeting 7783 genes and a luciferase reporter controlled by an ATF6-dependent ERSE (ER stress-response element) promoter, to identify proteins that activate or inhibit the ATF6 signaling pathway in HEK293 cells. To validate the screening results, intestinal epithelial cell lines (Caco-2 cells) were transfected with small interfering RNAs or with a plasmid overexpressing a constitutively active form of ATF6. Caco-2 cells with a CRISPR-mediated disruption of autophagy related 16 like 1 gene (ATG16L1) were used to study the effect of ATF6 on ER stress in autophagy-deficient cells. We also studied intestinal organoids derived from mice that overexpress constitutively active ATF6, from mice with deletion of the autophagy related 16 like 1 or X-Box binding protein 1 gene in IECs (Atg16l1^ΔIEC or Xbp1^ΔIEC, which both develop spontaneous ileitis), from patients with Crohn's disease (CD) and healthy individuals (controls). Cells and organoids were incubated with tunicamycin to induce ER stress and/or chemical inhibitors of newly identified activator proteins of ATF6 signaling, and analyzed by real-time polymerase chain reaction and immunoblots. Atg16l1^ΔIEC and control (Atg16l1^fl/fl) mice were given intraperitoneal injections of tunicamycin and were treated with chemical inhibitors of ATF6 activating proteins.

RESULTS

We identified and validated 15 suppressors and 7 activators of the ATF6 signaling pathway; activators included the regulatory subunit of casein kinase 2 (CSNK2B) and acyl-CoA synthetase long chain family member 1 (ACSL1). Knockdown or chemical inhibition of CSNK2B and ACSL1 in Caco-2 cells reduced activity of the ATF6-dependent ERSE reporter gene, diminished transcription of the ATF6 target genes HSP90B1 and HSPA5 and reduced NF-κB reporter gene activation on tunicamycin stimulation. Atg16l1^ΔIEC and or Xbp1^ΔIEC organoids showed increased expression of ATF6 and its target genes. Inhibitors of ACSL1 or CSNK2B prevented activation of ATF6 and reduced CXCL1 and tumor necrosis factor (TNF) expression in these organoids on induction of ER stress with tunicamycin. Injection of mice with inhibitors of ACSL1 or CSNK2B significantly reduced tunicamycin-mediated intestinal inflammation and IEC death and expression of CXCL1 and TNF in Atg16l1^ΔIEC mice. Purified ileal IECs from patients with CD had higher levels of ATF6, CSNK2B, and HSPA5 messenger RNAs than controls; early-passage organoids from patients with active CD show increased levels of activated ATF6 protein, incubation of these organoids with inhibitors of ACSL1 or CSNK2B reduced transcription of ATF6 target genes, including TNF.

CONCLUSIONS

Ileal IECs from patients with CD have higher levels of activated ATF6, which is regulated by CSNK2B and HSPA5. ATF6 increases expression of TNF and other inflammatory cytokines in response to ER stress in these cells and in organoids from Atg16l1^ΔIEC and Xbp1^ΔIEC mice. Strategies to inhibit the ATF6 signaling pathway might be developed for treatment of inflammatory bowel diseases.

Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects

BACKGROUND

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a negative immune regulator. Heterozygous CTLA4 germline mutations can cause a complex immune dysregulation syndrome in human subjects.

OBJECTIVE

We sought to characterize the penetrance, clinical features, and best treatment options in 133 CTLA4 mutation carriers.

METHODS

Genetics, clinical features, laboratory values, and outcomes of treatment options were assessed in a worldwide cohort of CTLA4 mutation carriers.

RESULTS

We identified 133 subjects from 54 unrelated families carrying 45 different heterozygous CTLA4 mutations, including 28 previously undescribed mutations. Ninety mutation carriers were considered affected, suggesting a clinical penetrance of at least 67%; median age of onset was 11 years, and the mortality rate within affected mutation carriers was 16% (n = 15). Main clinical manifestations included hypogammaglobulinemia (84%), lymphoproliferation (73%), autoimmune cytopenia (62%), and respiratory (68%), gastrointestinal (59%), or neurological features (29%). Eight affected mutation carriers had lymphoma, and 3 had gastric cancer. An EBV association was found in 6 patients with malignancies. CTLA4 mutations were associated with lymphopenia and decreased T-, B-, and natural killer (NK) cell counts. Successful targeted therapies included application of CTLA-4 fusion proteins, mechanistic target of rapamycin inhibitors, and hematopoietic stem cell transplantation. EBV reactivation occurred in 2 affected mutation carriers after immunosuppression.

CONCLUSIONS

Affected mutation carriers with CTLA-4 insufficiency can present in any medical specialty. Family members should be counseled because disease manifestation can occur as late as 50 years of age. EBV- and cytomegalovirus-associated complications must be closely monitored. Treatment interventions should be coordinated in clinical trials.

Intestinal epithelial cell endoplasmic reticulum stress promotes MULT1 up-regulation and NKG2D-mediated inflammation

Hosomi et al. show that intestinal epithelial cell–specific deletion of X-box–binding protein 1, an unfolded protein response–related transcription factor, results in CHOP-dependent increased expression of specific natural killer group 2 member D (NKG2D) ligands. This activates NKG2D-expressing intraepithelial group 1 ILCs and promotes small intestinal inflammation.

Endoplasmic reticulum (ER) stress is commonly observed in intestinal epithelial cells (IECs) and can, if excessive, cause spontaneous intestinal inflammation as shown by mice with IEC-specific deletion of X-box–binding protein 1 (Xbp1), an unfolded protein response–related transcription factor. In this study, Xbp1 deletion in the epithelium (Xbp1^ΔIEC) is shown to cause increased expression of natural killer group 2 member D (NKG2D) ligand (NKG2DL) mouse UL16-binding protein (ULBP)–like transcript 1 and its human orthologue cytomegalovirus ULBP via ER stress–related transcription factor C/EBP homology protein. Increased NKG2DL expression on mouse IECs is associated with increased numbers of intraepithelial NKG2D-expressing group 1 innate lymphoid cells (ILCs; NK cells or ILC1). Blockade of NKG2D suppresses cytolysis against ER-stressed epithelial cells in vitro and spontaneous enteritis in vivo. Pharmacological depletion of NK1.1⁺ cells also significantly improved enteritis, whereas enteritis was not ameliorated in Recombinase activating gene 1^−/−;Xbp1^ΔIEC mice. These experiments reveal innate immune sensing of ER stress in IECs as an important mechanism of intestinal inflammation.

The Impact of Person Centered Planning on the Content and Organization of Individual Supports

Person Centered Planning (PCP) is an approach to designing support that is guided by the individual with disabilities (or his/her advocates) that receives support, builds from personal strengths and vision, and results in practical action plans. While PCP procedures have been advocated strongly and adopted widely, there is little empirical documentation of the impact of the approach on the quality of resulting plans or the perceived impact of support on the lives of people with disabilities. The present study provides an analysis of the impact that the use of PCP had with ten transition-age students receiving special education services. Interviews with eight educators and ten students/parents indicated that PCP training was associated with (a) increased use of PCP procedures, (b) increased number of written goals supported outside the school-time, (c) increased number of non-paid individuals scheduled to provide support, and (d) higher satisfaction with the planning process by educators and students/parents.

Abstract LB-078: The role of CEACAM1 in neutrophil extracellular Trap mediated cancer metastasis

We have previously identified that Neutrophil Extracellular Traps (NETs) are an important contributing factor to the metastatic process. However, the underlying molecular mechanisms by which NETs facilitate metastasis remain unclear. Using mass spectrometry, amongst 583 distinct proteins, we identified CEACAM1 (CC1) in isolated human NETs and we sought to determine whether CC1 has a role in NET-mediated cancer metastasis. The presence of CC1 on NETs was confirmed by immunofluorescence. In vitro static adhesion of human colon cancer HT29 cells to isolated purified human NETs was reduced by 50% using a function blocking antibody against human CC1, but not isotype control, an effect equal to NET degradation with DNAse. Adhesion of murine colon cancer MC38-CC1L cells to C57BL/6 mouse neutrophils stimulated to produce NETs with phorbol myristate acetate (PMA) was increased 3-fold compared to untreated neutrophils, an effect that was completely attenuated with DNAse. PMA stimulation of neutrophils isolated from Ceacam1−/− knockout (KO) mice did not increase adhesion to MC38-CC1L cells. Using a parallel plate flow chamber, a physiologically relevant adhesion model under the shear conditions encountered in liver sinusoids, we flowed Lewis lung carcinoma (C10) cancer cells over neutrophils isolated from C57BL/6 or Ceacam1−/− KO mice. PMA-induced NET formation in C57BL/6 mouse neutrophils increased cancer cell adhesion 5-fold, an effect again completely attenuated by DNAse or use of neutrophils from Ceacam1−/− KO mice. Using a transwell chamber, MC38-CC1L cancer cells exposed to NET-stimulated Ceacam1−/− KO neutrophils had a 50% decrease in migration, compared to those exposed to NETs from C57BL/6 neutrophils. In order to delineate the role of CC1 in NET-related in vivo adhesion of cancer cells to liver sinusoids, we performed a series of neutrophil depletion and re-infusion experiments. C57BL/6 mice, depleted of neutrophils with anti-GR1 24 hrs prior, were re-infused with neutrophils isolated from C57BL/6 or Ceacam1−/− KO mice. This was followed by injection of MC38-CFSE labelled cells and hepatic intravital microscopy was used to quantify in vivo cancer cell adhesion and migration. PMA-stimulated C57BL/6 neutrophils prior to re-infusion was associated with a two-fold increase in adhesion compared to PMA-stimulated Ceacam1−/− KO neutrophils, an effect that was completely attenuated using DNAse.

Our data support the notion that CEACAM1 is, at least in part, responsible for the increased cancer cell migration mediated by Neutrophil Extracellular Traps. We have thereby identified NET-associated CEACAM1 as a putative therapeutic target to prevent the metastatic progression of cancer cells.

Citation Format: Phil Vourtzoumis, Rashmi Seth, Roni Rayes, Sara Najmeh, Jonathan Cools-Lartigue, Betty Giannias, France Bourdeau, Nicole Beauchemin, Simon Rousseau, Richard Blumberg, Jonathan D. Spicer, Lorrenzo Edwin Ferri. The role of CEACAM1 in neutrophil extracellular Trap mediated cancer metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-078.

Transplacental passage of IgG anti-IgE/IgE immune complexes (HYP7P.306)

Maternal IgG mediates the transplacental passage of several antigens; however, it is unclear if maternal IgE may be transferred across the placenta as IgG anti-IgE/IgE immune complexes. In this study, we determined maternal and cord blood serum concentrations of IgG anti-IgE/IgE immune complexes in a cohort of allergic and non-allergic mother/infant dyads. We found a strong correlation (r = 0.88) between maternal and cord serum concentrations, which is strongly suggestive of placental transmission. Subclass analysis demonstrated the majority of IgG anti-IgE/IgE immune complexes in maternal sera were of the IgG1 and IgG4 subclasses, while those in cord blood were of the IgG1 subclass. Levels of IgG1 anti-IgE/IgE immune complexes were significantly higher in allergic vs. non-allergic pregnant women. To investigate the role of FcRn in the transplacental passage of IgG anti-IgE/IgE immune complexes, we used MDCK cells stably transfected with hFcRn. IgG, IgG anti-IgE, and IgG anti-IgE/IgE immune complexes bound to hFcRn-expressing MDCK cells in a pH-dependent manner whereas IgE alone did not. The addition of an FcRn blocking antibody effectively inhibited the binding of IgG anti-IgE/IgE immune complexes. Ongoing experiments are being conducted using the MDCK cells to demonstrate FcRn-mediated transcytosis. The ability of maternal IgG anti-IgE/IgE immune complexes to bind fetal myeloid dendritic cells and regulate FcεRI-dependent pro-inflammatory responses is being investigated.

The microbiome regulates the homeostasis of host invariant natural killer T (iNKT) cells (MUC4P.830)

Symbiotic bacteria intimately participate in host physiological processes and impact host health and disease, although details at the molecular level largely remain unknown. We discovered that symbiotic Bacteroides species produce sphingolipids to modify the host antigen environment of the invariant natural killer T (iNKT) cells, a key immune modulator recognizing CD1d-restricted lipids. Using gnotobiotic technology and analytical tools, we found that bacterial glycosphingolipids, specifically one molecular fraction called GSL-Bf717, block iNKT cell activation and inhibit cell proliferation in early life. As a result, the total colonic iNKT cell number is restricted in adulthood and the host is protected when challenged by iNKT cell-mediated oxazolone colitis. These results suggest that intestinal bacterial sphingolipids are critical for establishing colonic iNKT cell homeostasis and host tolerance to environmental challenges. In addition, we find that the regulation depends on exposure to these symbiotic molecules in a critical early-life window, which, if missed, has irreversible impacts on host. This study contributes to our understanding of the essential role microbes play in host health and disease with precious molecular details that are largely lacking. The unique inhibitive power of GSL-Bf717 can be harnessed to provide therapeutic interventions in human autoimmune and allergic disorders where iNKT cell activation is detrimental.

Toll-like receptor 4-mediated endoplasmic reticulum stress in intestinal crypts induces necrotizing enterocolitis

The cellular cues that regulate the apoptosis of intestinal stem cells (ISCs) remain incompletely understood, yet may play a role in diseases characterized by ISC loss including necrotizing enterocolitis (NEC). Toll-like receptor-4 (TLR4) was recently found to be expressed on ISCs, where its activation leads to ISC apoptosis through mechanisms that remain incompletely explained. We now hypothesize that TLR4 induces endoplasmic reticulum (ER) stress within ISCs, leading to their apoptosis in NEC pathogenesis, and that high ER stress within the premature intestine predisposes to NEC development. Using transgenic mice and cultured enteroids, we now demonstrate that TLR4 induces ER stress within Lgr5 (leucine-rich repeat-containing G-protein-coupled receptor 5)-positive ISCs, resulting in crypt apoptosis. TLR4 signaling within crypts was required, because crypt ER stress and apoptosis occurred in TLR4(ΔIEC-OVER) mice expressing TLR4 only within intestinal crypts and epithelium, but not TLR4(ΔIEC) mice lacking intestinal TLR4. TLR4-mediated ER stress and apoptosis of ISCs required PERK (protein kinase-related PKR-like ER kinase), CHOP (C/EBP homologous protein), and MyD88 (myeloid differentiation primary response gene 88), but not ATF6 (activating transcription factor 6) or XBP1 (X-box-binding protein 1). Human and mouse NEC showed high crypt ER stress and apoptosis, whereas genetic inhibition of PERK or CHOP attenuated ER stress, crypt apoptosis, and NEC severity. Strikingly, using intragastric delivery into fetal mouse intestine, prevention of ER stress reduced TLR4-mediated ISC apoptosis and mucosal disruption. These findings identify a novel link between TLR4-induced ER stress and ISC apoptosis in NEC pathogenesis and suggest that increased ER stress within the premature bowel predisposes to NEC development.

Microbiota, disease, and back to health: a metastable journey

Alterations in the composition of the commensal microbiota have been observed in many complex diseases. Understanding the basis for these changes, how they relate to disease risk or activity, and the mechanisms by which the symbiotic state of colonization resistance and host homeostasis is restored is critical for future therapies aimed at manipulating the microbiota.

FcRn-mediated transport of IgG can either enhance or neutralize chlamydial infection (49.17)

IgG is the dominant antibody in the female and male reproductive tracts (RT). Furthermore, the neonatal Fc receptor (FcRn) is expressed by epithelial cells in both these tissues. The acidic environment (pH 4.5-6.5) in the RT is optimal for FcRn uptake of IgG by epithelial cells, which suggests that IgG could either enhance or protect against infection by pathogens such as Chlamydia, depending on antibody specificity. We show that IgG is indeed internalized by reproductive tract epithelial cells in an FcRn and pH-dependent manner. Furthermore, IgG specific for the chlamydial major outer membrane protein (MOMP), expressed predominantly on the extracellular elementary body (EB) actually enhanced infection, whilst IgG specific for an antigen expressed during intracellular chlamydial replication (IncA) partially neutralized infection. Both enhancement (IgG-MOMP) and protection (IgG-IncA) were abrogated by knockdown of FcRn expression. Chlamydiae inhibit lysosomal activity to promote infection and the presence of intracellular IncA-IgG enhanced lysosomal activity in infected cells. IgA is also found in RT secretions as is the IgA transport molecule the polyimmunoglobulin receptor (PIgR). Unlike IgG, IgA-MOMP and IgA-IncA both neutralized chlamydial infection in a PIgR-dependent manner. Thus for antibody-mediated protection against Chlamydia, IgG specific for intracellular chlamydial antigens, together with IgA specific for both stages of the replicative cycle may be optimal.

Colitis-associated glycome for local memory CD4+ T cell expansion (49.5)

Immune responses are modified by a diverse and abundant repertoire of carbohydrate structures on cell surface, which is known as the “glycome”. We herein report a colitis-associated glycome<CAG>that is created on the colonic, but not systemic, memory CD4+T cells under intestinal inflammatory conditions. Through gene screening approaches, we found that CAG represents an immature core-1 O-glycan that is created through the decreased expression of an enzyme, core-2 β1,6-N-acetylglucosaminyltransferase<C2GnT>1 that is responsible for the production of core-2 O-glycan branch through an addition of GlcNAc to a core-1 O-glycan. Indeed, restoration of C2GnT1 expressions using T-cell-specific C2GnT transgenic mice abolished the inflammation-induced development of CAG on colonic CD4+T cells. Functionally, the CAG promoted the proliferation of memory CD4+T cells, resulting in the exacerbation of colitis. Mechanistically, CAG induced the “super rafts” formation on memory CD4+T cells, which provide a place for initiating the signaling machinery for T cell activation. Indeed, the CAG contributed for sustaining the activation of protein kinase C θ, a key signaling molecule for T cell activation. These findings suggest that a specific glycome, which is created on memory CD4+T cells under intestinal inflammatory conditions, leads to further exacerbation of diseases by promoting memory T cell expansion.

Sensing of low-dose soluble antigen via Immunoglobulin E (106.1)

Dendritic cells (DCs) are the most potent antigen presenting cells and continuously encounter exogenous antigens at low dose. We show here that DCs use IgE-mediated antigen uptake to efficiently sense soluble antigen at a dose range that otherwise escapes immune detection. IgE-mediated antigen sampling via Fc-epsilon-RI simultaneously shuttles into the direct MHC class II-restricted presentation and the cross-presentation pathway resulting in the activation of Th2-type CD4+ T cells as well as cytotoxic CD8+ T cells (CTLs). Fc-epsilon-RI stabilizes at the cell surface of DCs after monovalent ligation with IgE. Antigen-mediated crosslinking of the receptor induces internalization into endo/lysosomal compartments. Absence of IL-12 production during IgE-mediated antigen uptake and presentation is critical for shifting the CD4 response towards Th2, but does not affect the generation of CTLs. Presence of IL-12 during IgE-mediated presentation redirects the immune response towards Th1 by suppressing the production of IL-4 and IL-13. Neither basophils nor mast cells can induce primary T cell responses after antigen sampling via IgE. These results establish a uniquely sensitive pathway for the detection of soluble exogenous antigen by DCs with high relevance for IgE-mediated immune responses in humans.

Modification of VRC01 for enhancing half-life and ADCC activity (155.39)

Several studies have demonstrated that increased binding of IgG to hFcRn extended the half-life of antibody in serum. In addition, the Fc region of IgG binds to FcγRIIIa, mediating ADCC. Modification for hFcRn and FcγRIIIa may negatively affect their functions respective to the other. Here, to increase the potency and duration of VRC01, a broadly neutralizing antibody to HIV gp120, we have combined hFcRn-binding enhancing mutations (QL, LS, A, AAA and YTE) with ADCC enhancing mutations (DE and DLE) to improve in vivo activity. We demonstrated that all of the mutants have Ag binding affinities similar to VRC01 wild type (WT), indicating that the neutralizing activities are likely maintained with these mutants. All mutants except mutant group A have increased binding to hFcRn at both pH6.0 and pH7.4 compared to VRC01 WT. Using a transcytosis assay, we showed that DE-QL and DE-LS mutants had increased transport across epithelial cells compared to others in the DE mutant groups. ADCC enhancing mutations recovered the loss of ADCC acitivities and FcγRIIIa binding affinity associated with hFcRn-binding enhancing mutations. Unlike other mutations tested, a single LS mutant has FcγRIIIa binding and ADCC activity similar to VRC01 WT. The combined DE-LS and DLE-LS mutants showed increased functional activity in transcytosis and ADCC assays. Taken together, the DE-LS or DLE-LS mutants were able to enhance both half-life and effector functions in vitro.

IAP inhibitors enhance co-stimulation to promote tumor immunity

The inhibitor of apoptosis proteins (IAPs) have recently been shown to modulate nuclear factor κB (NF-κB) signaling downstream of tumor necrosis factor (TNF) family receptors, positioning them as essential survival factors in several cancer cell lines, as indicated by the cytotoxic activity of several novel small molecule IAP antagonists. In addition to roles in cancer, increasing evidence suggests that IAPs have an important function in immunity; however, the impact of IAP antagonists on antitumor immune responses is unknown. In this study, we examine the consequences of IAP antagonism on T cell function in vitro and in the context of a tumor vaccine in vivo. We find that IAP antagonists can augment human and mouse T cell responses to physiologically relevant stimuli. The activity of IAP antagonists depends on the activation of NF-κB2 signaling, a mechanism paralleling that responsible for the cytotoxic activity in cancer cells. We further show that IAP antagonists can augment both prophylactic and therapeutic antitumor vaccines in vivo. These findings indicate an important role for the IAPs in regulating T cell-dependent responses and suggest that targeting IAPs using small molecule antagonists may be a strategy for developing novel immunomodulating therapies against cancer.

Expression of nonclassical class I molecules by intestinal epithelial cells

It is well recognized that the nature of the immune response is different in the intestinal tract than in peripheral lymphoid organs. The immunologic tone of the gut-associated lymphoid tissue is one of suppression rather than active immunity, distinguishing pathogens from normal flora. Failure to control mucosal immune responses may lead to inflammatory diseases such as Crohn's disease (CD) and ulcerative colitis (UC) and celiac disease. It has been suggested that this normally immunosuppressed state may relate to unique antigen-presenting cells and unique T-cell populations. The intestinal epithelial cell (IEC) has been proposed to act as a nonprofessional antigen-presenting cell (APC). Previous studies have suggested that antigens presented by IECs result in the activation a CD8(+) regulatory T-cell subset in a nonclassical MHC I molecule restricted manner. We therefore analyzed the expression of nonclassical MHC I molecules by normal IECs and compared this to those expressed by inflammatory bowel disease (IBD) IECs. Normal surface IEC from the colon and, to a much lesser extent, the small bowel express nonclassical MHC I molecules on their surface. In contrast, mRNA is expressed in all intestinal epithelial cells. Surface IEC express CD1d, MICA/B, and HLA-E protein. In contrast, crypt IECs express less or no nonclassical MHC I molecules but do express mRNA for these molecules. Furthermore, the regulation of expression of distinct nonclassical class I molecules is different depending on the molecule analyzed. Interestingly, IECs derived from patients with UC fail to express any nonclassical MHC I molecules (protein and HLA-E mRNA). IECs from CD patients express HLA-E and MICA/B comparable to that seen in normal controls but fail to express CD1d. Thus, in UC there may be a failure to activate any nonclassical MHC I molecule restricted regulatory T cells that may result in unopposed active inflammatory responses. In CD only the CD1d-regulated T cells would be affected.

CD28-dependent Rac1 activation is the molecular target of azathioprine in primary human CD4+ T lymphocytes

Azathioprine and its metabolite 6-mercaptopurine (6-MP) are immunosuppressive drugs that are used in organ transplantation and autoimmune and chronic inflammatory diseases such as Crohn disease. However, their molecular mechanism of action is unknown. In the present study, we have identified a unique and unexpected role for azathioprine and its metabolites in the control of T cell apoptosis by modulation of Rac1 activation upon CD28 costimulation. We found that azathioprine and its metabolites induced apoptosis of T cells from patients with Crohn disease and control patients. Apoptosis induction required costimulation with CD28 and was mediated by specific blockade of Rac1 activation through binding of azathioprine-generated 6-thioguanine triphosphate (6-Thio-GTP) to Rac1 instead of GTP. The activation of Rac1 target genes such as mitogen-activated protein kinase kinase (MEK), NF-kappaB, and bcl-x(L) was suppressed by azathioprine, leading to a mitochondrial pathway of apoptosis. Azathioprine thus converts a costimulatory signal into an apoptotic signal by modulating Rac1 activity. These findings explain the immunosuppressive effects of azathioprine and suggest that 6-Thio-GTP derivates may be useful as potent immunosuppressive agents in autoimmune diseases and organ transplantation.

Treatment of T cell-dependent experimental colitis in SCID mice by local administration of an adenovirus expressing IL-18 antisense mRNA

Recent studies have shown that IL-18, a pleiotropic cytokine that augments IFN-gamma production, is produced by intestinal epithelial cells and lamina propria cells from patients with Crohn's disease. In this study, we show that IL-18 is strongly expressed by intestinal epithelial cells in a murine model of Crohn's disease induced by transfer of CD62L+ CD4+ T cells into SCID mice. To specifically down-regulate IL-18 expression in this model, we constructed an E1/E3-deleted adenovirus expressing IL-18 antisense mRNA, denoted Ad-asIL-18, and demonstrated the capacity of such a vector to down-regulate IL-18 expression in colon-derived DLD-1 cells and RAW264.7 macrophages. Local administration of the Ad-asIL-18 vector to SCID mice with established colitis led to transduction of epithelial cells and caused a significant suppression of colitis activity, as assessed by a newly developed endoscopic analysis system for colitis. Furthermore, treatment with Ad-asIL-18 induced a significant suppression of histologic colitis activity and caused suppression of mucosal IFN-gamma production, whereas IFN-gamma production by spleen T cells was unaffected. Taken together, these data indicate an important role for IL-18 in the effector phase of a T cell-dependent murine model of colitis and suggest that strategies targeting IL-18 expression may be used for the treatment of patients with Crohn's disease.

A signalling accessory molecule revealed by a new anti-fibroblastoid L cell monoclonal antibody

Fibroblastoid mouse L-cells are widely used in immunological models because when transfected with class II-coding genes they become efficient antigen presenting cells. Little is known, however, about the cell surface markers borne by L-cells and their putative involvement/Interference with the experimental models studied. Rats were immunized against DAP.3 cells (subclone of L-cells) and monoclonal antibodies (mAbs) were prepared. One of them, 4D4, was studied in detail. It recognizes an epitope which is neither cell lineage- nor strain- nor species-restricted since, in addition to DAP.3 cells, it binds, as determined by flow cytometry and immunohistochemistry, to various cells such as CD8+ T cells from thymus, spleen, lymph node or intestinal epithelium, mouse peritoneal B cells and various tissues such as renal, pulmonary or intestinal epithelia. 4D4 mAb immunoprecipitates an undescribed 68 kDa protein. Functionally, this mAb inhibits the IL-2 secretion of a T cell clone in response to its peptide presented by appropriate class II-transfected L-cells and induces a negative selection of double positive CD4+CD8+ thymocytes. Since the 4D4 ligand is found on cells which are submitted to selection (T cells) and on cells which mediate selection (epithelial and antigen presenting cells), we conclude that 4D4 mAb defines a cell surface antigen involved, as an accessory molecule, in a cell selection process.

Expression of amyloid precursor protein (beta-APP) in the neonatal brain following hypoxic ischaemic injury

Perinatal hypoxic ischaemic brain injury (HII) is a major cause of neonatal mortality and long-term neurological morbidity. An understanding of the molecular events which follow HII may lead to novel treatments to improve the final outcome for affected infants. The beta-amyloid precursor protein (beta-APP) is a widely expressed transmembrane protein whose proposed functions include stabilization of neuronal calcium fluxes, inhibition of the clotting cascade and cell-cell or cell-matrix adhesion. Normally present at low levels in neurons its expression is induced as part of the acute response of the adult brain to HII. This study aimed to determine whether beta-APP is also part of the acute adaptive response of the infant brain to HII. Immunohistochemistry and Western blotting were used to assess cerebral beta-APP expression in 14-day-old rat pups subjected to unilateral HII, and in 10 term human infants, who died between 12 h and 16 months after severe perinatal HII. In the rat pups beta-APP expression was increased by 2 h post-injury, peaked, fourfold above control levels, at 24 h and gradually declined over the following 4 days. Expression was induced bilaterally, but was greater on the side of injury. In the human infants, increased, predominantly neuronal expression of beta-APP, was detectable immunohistochemically within 24 h of injury and was greatest in those infants dying within 3 days. Expression was particularly strong in the areas showing histological evidence of injury, but was also seen in apparently undamaged areas. We conclude that beta-APP induction is part of the the acute adaptive response of the neonatal brain to HII.

Group B streptococcal infection: when does vertical transmission take place?

Expression of CD45 isoforms was used to estimate when group B streptococci had infected a child born with low Apgar scores who subsequently died. The measure suggested that infection was present more than 24 hours before delivery, thus distinguishing perinatal infection as the primary event which preceded intrapartum asphyxia in this case.

Defects in signal transduction caused by a T cell receptor beta chain substitution

An antigen-specific T-T hybridoma was mutagenized with ethylmethane sulfonate and negatively selected by anti-Ly-6 antibody-induced growth inhibition. One of the mutants generated, M4/8, had lost surface expression of a T cell receptor (TcR) V beta 8 epitope detected on the surface of the parental cell line. However, the mutant cell line did express high levels of TcR heterodimer as detected with a pan-specific anti-TcR antibody. CD3 epsilon, Ly-6 and Thy-1 were expressed at levels similar to the wild-type parental cell line. Analysis of the surface TcR/CD3 complexes by immunoprecipitation and two-dimension gel electrophoresis confirmed that the major discernable difference between the wild-type and mutant TcR/CD3 complexes resided in the TcR beta chain. The parental cell line had the potential to express two TcR heterodimers, V alpha V beta 1 and V alpha V beta 8, as determined by Northern blot analysis. Co-modulation experiments suggested that both types of receptors were expressed. However, the V alpha V beta 8 receptor was the predominant form. In contrast, the mutant M4/8 cell line did not synthesize V beta 8 mRNA and, thus, only the V alpha V beta 1 TcR was synthesized. Despite the normal surface expression of TcR/CD3 complex, the M4/8 mutant cell line did not produce interleukin 2 (IL 2) in response to antigen or soluble anti-CD3 epsilon monoclonal antibody (mAb). Furthermore, it responded poorly to concanavalin A, phytohemagglutinin and anti-Ly-6 mAb. Cross-linking of the stimulatory antibodies partially restored the IL 2 response to anti-CD3 epsilon or anti-Ly-6 to wild-type levels. Phorbol ester and ionomycin stimulated a full IL 2 response in the M4/8 cell line, demonstrating that the defect in the decreased signaling in the mutant did not result from a defect in the IL 2 gene program. In conclusion, these data suggested that the pairing of alpha/beta heterodimer not only determined antigen/MHC specificity but also the signaling efficiency of the TcR/CD3 complex.

T-cell antigen receptor (TCR)-alpha/beta heterodimer formation is a prerequisite for association of CD3-zeta 2 into functionally competent TCR.CD3 complexes

In order to study the relationship between assembly, surface expression, and signal transduction of the alpha/beta T-cell antigen receptor-CD3 complex (TCR.CD3), a series of T-cell mutants with a partial block in assembly of the complex was generated. By chemical mutagenesis, we produced somatic cell variants of the human T-leukemia cell line, HPB-ALL, which expressed low amounts of TCR.CD3 complexes on their surface. RNA and protein analyses demonstrated that most variants synthesized normal amounts of the individual members of the complex, i.e. TCR-alpha, TCR-beta, CD3-gamma, -delta, -epsilon, and -zeta. In these variants, less than 10% of the TCR.CD3 complexes inside the cell contained the CD3-zeta 2 homodimer due to an intrinsic deficiency in the formation of the TCR-alpha/beta heterodimer. The low level of assembly of CD3-zeta 2 into the TCR.CD3 complex and an additional decrease in the rate of export of the TCR.CD3 complex from the endoplasmic reticulum explained the low level of expression of alpha/beta receptors on the surface of these mutants. Only cells with the complete set of subunits of the TCR.CD3 complex on their surface were capable of transducing CD3-mediated signals. The results presented in this paper indicate that TCR-alpha/beta heterodimer formation is an obligatory requirement for assemblage of CD3-zeta 2 into a functionally competent TCR.CD3 complex.

Cost-benefit analysis of early return to work after uncomplicated acute myocardial infarction

The economic consequences of an Occupational Work Evaluation designed to identify low risk patients recovering from uncomplicated acute myocardial infarction (AMI) and hasten their return to work was evaluated in a randomized trial. Two hundred one employed, clinically low risk men recovering from AMI were randomized to undergo an intervention (intervention group, 99 patients) consisting of an Occupational Work Evaluation or to receive usual care (usual care group, 102 patients). The time to return to work was reduced from 75 days in usual care patients to 51 days in intervention patients (p less than 0.002). Significant differences were found between groups for medical costs and occupational income during follow-up. Total medical costs per patient were lower in the intervention patients than in the usual care patients in the 6 months after AMI ($2,970 vs $3,472). Occupational income per patient was higher in intervention patients than in the usual care group in the 6 months after AMI ($9,655 vs $7,553). The per capita benefit accounting for medical costs and occupational income was $6,685 for intervention patients and $4,081 for usual care patients. Projected to the greater than 300,000 low risk, employed survivors of AMI annually in this country, the savings generated by the Occupational Work Evaluation could yield an annual economic benefit greater than 800 million dollars.

Functional characterization of T lymphocytes propagated from human lung carcinomas

Tissue fragments from biopsies of six patients with malignant tumors of the lung were cultured in interleukin 2 (IL-2). Cultures of proliferating lymphocytes were isolated from all cases. Tumor cell lines (small cell carcinoma and adenocarcinoma) were established in parallel cultures from two of these patients. Lymphocytes that proliferated in vitro were virtually all mature T lymphocytes (greater than 95% T3+, T11+). The T8+ subset accounted for an average of 70% while T4+ cells averaged 20% of the cells in culture. HNK-1 antigen was presented on 23% of cells. Seventy-four percent of cells expressed Ia (HLA-DR) antigens. B cells did not proliferate under these conditions. In all cases the cells lysed K562 targets and were active in lectin-mediated cytolysis against human lymphoblasts. All cultures produced lymphokines (IL-2 and IFN-gamma) when stimulated with PHA. Lymphocytes grown from a tissue specimen with adenocarcinoma were capable of killing autologous tumor cells in vitro. Specific cytotoxicity has been maintained by these cultured lymphocytes for greater than 6 months. IL-2 activated peripheral blood cells in this case showed little specific cytotoxicity for autologous tumor cells. Lymphocytes from another specimen of adenocarcinoma also lysed this tumor, but cells from the other four specimens did not. Lymphocytes propagated from the specimen of small cell undifferentiated cancer did not lyse autologous tumor cells. These data show that primary lung tumors contain activated T cells which will respond to IL-2 in vitro. These tumor-infiltrating lymphocytes have demonstrable function, which can include cytolytic activity against autologous lung tumor.

Ocular Loa Loa with cryoprobe extraction of subconjunctival worm

A healthy 27-year-old West African man presented to the emergency room at the Massachusetts Eye and Ear Infirmary complaining of a moving foreign body sensation in his right eye. He had experienced recurrent episodes of subconjunctival Loa Loa, a parasite endemic in Africa. A cryoprobe was successfully used for extraction of a large adult worm. Strategies for the removal of subconjunctival worms are presented. The systemic and ocular manifestations of Loa Loa are reviewed and a discussion of complications of medical management follows.

Synthesis of R-plasmid-coded beta-lactamase in minicells and in an in vitro system

beta-Lactamase encoded by a small, nontransferring R-plasmid, NTP1, conferring ampicillin resistance to its host bacteria, was purified. NTP1 plasmid-coded beta-lactamase was found to be periplasmically located in the host Escherichia coli cell, to have a molecular weight of about 25,000, and to show a relatively low activity against oxacillin and methicillin compared with benzylpenicillin. These characteristics indicate that NTP1 plasmid-coded beta-lactamase is very similar or identical to the "TEM-type" beta-lactamase, which is the most common beta-lactamase coded by R-plasmids in enteric bacteria. In minicells containing NTP1 plasmids, at least six plasmid-specific proteins were synthesized, and beta-lactamase was synthesized in a greater amount than other plasmid-coded proteins. In a cell-free transcription-translation coupled system from E. coli, NTP1 plasmid deoxyribonucleic acid directed the synthesis of several species of plasmid-specific proteins, including active beta-lactamase. The in vitro system also showed preferential synthesis of beta-lactamase, as was observed in minicells containing NTP1 plasmids.