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Introduction: NF-κB proteins are transcription factors that modulate various functions of the immune system. NF-κB2 (or p100/p52) has particularly important roles in B cell development and function. Primary immunodeficiency due to mutations in the NFKB2 gene, encoding NF-κB2, range from combined immunodeficiency with susceptibility to viral or opportunistic infections to primarily antibody deficiency. Methods: A comprehensive chart review of our patient was performed. Results: Our patient, currently a 19-year-old male, presented with multiple autoimmune cytopenia resistant to treatment and generalized granulomatous lymphadenopathy. Whole exome sequencing identified a novel pathogenic variant in NFKB2 (c.1700C>T; p.A567V) that is the cause of our patient’s presentation. Conclusion: We present a novel pathogenic variant in NFKB2 with an unusual presentation. Statement of novelty: Here, we report a novel mutation in NFKB2 and the clinical presentation of the affected patient, which helps in further understanding the NF-κB2 pathway and its associated disease.

Background: Since the onset of the COVID-19 pandemic, a main challenge for clinicians and public health decision-makers has revolved around risk stratification in vulnerable populations, in particular individuals with inborn errors of immunity (IEI). However, available reports of the clinical course of COVID-19 in patients with IEI show wide variability, from a complete lack of symptoms to severe and complicated disease. Objective: To present the clinical features and outcomes of SARS-CoV-2 infection in adult patients with IEI. Methods: We performed a retrospective chart review documenting patient characteristics and clinical course of SARS-CoV-2 infection between December 2021 and July 2022. Results: Ten adult patients with IEI followed in our center were diagnosed with COVID-19, as determined by RT-PCR or rapid antigen testing. IEI in this cohort included those with humoral and combined immunodeficiencies, as well as phagocytic defects. An underlying lung comorbidity was identified in 3 patients. Symptoms were mostly mild and self-limiting, and no severe outcomes, complications, or mortality were noted in this study. Conclusions: We suggest that patients affected by a wide range of both humoral and combined IEI may demonstrate resilience, while highlighting the possible protective effects of vaccination and immunoglobulin replacement in this population. Statement of Novelty: We report on the mild COVID-19 clinical course of 10 adults with IEI.

Severe combined immunodeficiency is caused by critical genetic defects affecting the immune system. Early diagnosis and intervention are essential for preventing life-threatening infections, end-organ damage, and complications. Newborn screening for severe combined immunodeficiency is currently rolled out across many provinces and territories across Canada. The SickKids Newborn Screening Centre in Toronto, Ontario, is a quaternary referral centre that has evaluated SCID newborn screen-positive infants since the program’s introduction in 2013. Here, we provide updated algorithms for clinical investigation and follow-up of infants with an initial positive screen.

Background: Cytotoxic T lymphocyte-associated antigen-4 (CTLA4) haploinsufficiency is characterized by a variety of phenotypes, ranging from autoimmune disorders, enteropathy, fatal combined immunodeficiency, as well as lymphoproliferation and malignancy. Aim: To broaden the genotypic spectrum and clinical presentations of patients with CTLA4 variants. Methods: We evaluated a female patient with autoimmunity and lymphopenia. Immune workup and whole exome sequencing (WES) were performed. Results: The proband presented at 11 years of age with hypothyroidism and later developed Evans syndrome, alopecia, eczema, and lymphocytic interstitial pneumonia. Immune evaluation revealed T, B, and NK lymphopenia with normal humoral immunity. Following a negative genetic panel for autoimmune lymphoproliferative syndrome (ALPS), WES analysis identified a novel heterozygous intronic variant predicted in-silico to cause skipping of exon 2 of the CTLA4 gene. Conclusion: A novel heterozygous mutation in CTLA4 caused variable presentations of immune dysregulation, one of the hallmarks of CTLA4 haploinsufficiency. Statement of Novelty: We herein report a novel mutation in CTLA4 resulting in various features of autoimmunity.

Patients with inborn errors of the alternative NF-κB pathway have low thymic AIRE expression, leading to the development of auto-Abs neutralizing type I IFNs, and severe viral diseases.

BACKGROUND STAT1 gain-of-function (GOF) is an immune dysregulatory disorder with poorly studied genotype-phenotype correlation, impeding prognostication and early intervention. Given previous mechanistic studies, as well as anecdotal clinical reports, we sought to systematically determine whether DNA-binding domain (DBD) mutations in STAT1 result in a different phenotype than mutations in other gene domains. METHODS Negative prognostic features previously identified by the International STAT1 GOF Study Group (invasive infections, intracranial aneurysms, and malignancy), as well as other clinical features and mortality, were compared within a cohort of 30 patients with STAT1 GOF diagnosed at our center, consisting of 9 patients with DBD mutations and 21 patients with non-DBD mutations. We subsequently re-analyzed mortality data from a large, previously-published 274-patient cohort by the International STAT1 GOF Study Group. RESULTS While no differences were noted with respect to malignancy or symptomatic aneurysms, invasive /opportunistic infections were substantially more common among DBD patients, as were sinopulmonary infections, bronchiectasis, enteropathy, endocrinopathies, lymphoproliferative manifestations, and recurrent fevers/HLH. DBD patients also had a lower probability of survival and younger age of mortality compared with non-DBD patients. Our re-evaluation of the published data from the International STAT1 GOF Study Group revealed a similar finding of earlier mortality among patients harboring DBD mutations. CONCLUSION We report that STAT1 GOF patients with DBD mutations may be regarded as a unique subgroup, impacted more by early-onset profound combined immunodeficiency and with earlier mortality. These findings may impact clinical decision making with respect to early intervention, and in particular hematopoietic stem cell transplant considerations, in such patients.

Genetic aberrations in the NFκB pathway lead to primary immunodeficiencies with various degrees of severity. We previously demonstrated that complete ablation of the RelB transcription factor, a key component of the alternative pathway, results in an early manifested combined immunodeficiency requiring stem cell transplantation.To study the molecular basis of a progressive severe autoimmunity and immunodeficiency in three patients.Whole exome sequencing was performed to identify the genetic defect. Molecular and cellular techniques were utilized to assess the variant impact on NFκB signaling, canonical and alternative pathway crosstalk, as well as the resultant effects on immune function.Patients presented with multiple autoimmune progressive severe manifestations encompassing the liver, gut, lung, and skin, becoming debilitating in the second decade of life. This was accompanied by a deterioration of the immune system, demonstrating an age-related decline in naïve T cells and responses to mitogens, accompanied by a gradual loss of all circulating CD19Incomplete loss of RelB provided a unique opportunity to gain insights into NFκB's pathway interactions as well as the pathogenesis of autoimmunity. The P364L RelB mutation leads to gradual decline in immune function with progression of severe debilitating autoimmunity.

Objective: The objectives of this study are to present a case series of immunodeficient children who underwent a transcervical thymic biopsy and to describe the transcervical approach to the thymus gland. Design: Case series. Setting: Pediatric otolaryngology practice in an academic setting. Patients: Consecutive sample of immunodeficient children (≤18 years old) who underwent thymic biopsies from 1996 to 2019 for the purpose of confirming or excluding profound T cell immunodeficiency. Intervention: Diagnostic transcervical thymic biopsy. Results: A total of 14 patients with atypical combined immunodeficiency underwent the procedure during the study period, with minimal post-operative complication. The thymus was found to be abnormal histologically in 9 children and normal in another 5 patients. In all cases, thymus morphology helped define the extent of the immunodeficiency, resulting in either supporting a decision to perform a bone marrow transplant (8 patients) or avoid this high risk procedure (3 patients). Conclusion: Thymus biopsy is helpful in the characterization of childhood immunodeficiency and provides critical information that affects the medical management. The transcervical approach to the thymus is feasible in children and can be accomplished with minimal morbidity. Statement of novelty: Biopsies of the thymus have assisted in the characterization of new entities of primary immunodeficiency.

This protocol is excerpted from recent clinical trials used to study the pharmacokinetics, safety, and tolerability of subcutaneously administered immunoglobulin (SCIG) in subjects with primary immunodeficiency. The primary objective is to determine the weekly dose of SCIG product that produces a steady-state area under the concentration-time curve of total immunoglobulin G level that is non-inferior to that of regularly administered intravenous immunoglobulin (IVIG). We include details of the target population, eligibility criteria, treatment phases, key assessments and procedures, and study analyses. Given that IVIG may be problematic in patients with poor venous access or those who develop systemic adverse effects, among others, the development of SCIG for use in the home setting provides an alternative treatment technique for adults and children with primary immunodeficiency.Statement of novelty: This protocol describes the main topics found in prospective clinical studies evaluating the safety and pharmacokinetics of SCIG in subjects with primary immunodeficiency.

Introduction: The evaluation of lymphocyte proliferation responses is a critical component of the clinical work up for patients with suspected immunodeficiencies. Those with severe combined immunodeficiency (SCID) have consistently low to absent responses (stimulation index, SI) to the mitogen phytohemagglutinin (PHA). However, patients with combined immunodeficiency (CID) have more varied proliferative responses, and are open to a wide range of interpretations. Aims: To establish lymphocyte proliferation response reference ranges for patients with T cell defects, especially those with CID as well as healthy controls. Methods: Data was collected retrospectively from charts of patients with a diagnosis of SCID (n = 39), CID (n = 52), or from healthy controls (n = 440). Reference percentiles were calculated using the 95% of the distribution of the test results. Results: The reference ranges for the control group ranged from 134 to 2220.5, whereas those with CID were distributed between 0.81 and 169.1. Patients with typical SCID had profound low proliferative responses, with SI Conclusion: Our results highlight the variability of lymphocyte proliferation responses to PHA in patients with CID as well as healthy controls. These reference ranges will assist with the critical interpretation of assay results, particularly when values fall on the extreme end of the range. Statement of novelty: We provide reference ranges for lymphocyte proliferation responses to PHA from patients with CID and healthy controls.

Background Genetic faults in several components of the nuclear factor-κB pathway cause immunodeficiency. Most defects lead to combined immunodeficiency with a range of severity. Heterozygous mutations in NFKB1 were associated with common variable immunodeficiency, however, homozygous mutations have not been described. Objective We studied the molecular basis of combined immunodeficiency in a patient who presented with failure to thrive, persistent EBV viremia and hepatitis, pneumocystis jirovecii pneumonitis, and generalized lymphadenopathy. Methods Whole genome and exome sequencing followed by Sanger confirmation were performed to identify the genetic defect. Molecular and cellular techniques were used to assess the variant impact on the nuclear factor-κB pathway and lymphocyte function. Results Genetic analysis revealed a novel homozygous mutation in NFKB1, c.2878G>A, p.Gly960Arg (G960R). This affected p105 phosphorylation and p50 formation on antigen and cytokine stimulation, as well as attenuating nuclear signal transmission. As a result, both T- and B-cell maturation and function were perturbed. The number of memory CD4+ T cells were reduced, while CD8+ T cells consisted predominately of expanded differentiated populations. The function of T cells were diminished as shown by reduced responses to mitogens as well as diminished cytokine secretion. B-cell maturation was also affected, with decreased IgD+CD27+ memory B cells while transitional B cells were increased, likely contributing to the reduced ability to produce specific antibodies. Conclusion Homozygous G960R mutation in NFKB1 leads to a severe clinical presentation of combined immunodeficiency. This was associated with blockade of nuclear factor-κB pathway signaling, resulting in aberrations in T- and B-cell maturation and function.

Purine nucleoside phosphorylase (PNP) is a key enzyme required for the degradation of purine nucleosides into uric acid or their salvage into nucleic acids. Patients who are deficient in PNP suffer from progressive T cell immunodeficiency, with increased susceptibility to infections, autoimmunity, and neurologic abnormalities. In the absence of successful treatment to restore immune function, these patients rarely survive to adulthood. Hematopoietic stem cell transplantation is the only known cure for PNP deficiency. Use of an HLA-matched donor is preferable as the outcome with alternative donors have been variable; however, this option is rarely available. Gene therapy represents a therapeutic option that bypasses the need for a donor, and thus associated complications. Although first generation γ-retroviral vectors have been successful in some immunodeficiencies, in others, evidence of insertional mutagenesis prompted a halt in their use. More recently, the introduction of safer lentiviral vectors holds promise in offering a viable option to treat immunodeficiency. Here, we present a clinical trial protocol utilizing self-inactivating lentiviral vectors to treat PNP deficiency. Patients will be evaluated up to 3 years post-transplantation to determine the safety of lentiviral-treated stem cell infusion, as well as the extent of immune reconstitution. Statement of novelty: This protocol describes the novel treatment of PNP deficiency using lentiviral-based gene therapy.

Background Antibiotic-associated disruption of the gut microbiota is a known risk factor for Crohn's disease. This chronic inflammatory disorder results from aberrant host immune responses to subsets of the gut microbiota, and is characterized by intense neutrophil recruitment to the lamina propria, surface and crypt epithelium. Importantly, adherent-invasive Escherichia coli (AIEC) is abundant in ileal biopsies, highlighting a possible etiological role. In this study, we investigated the impact of antibiotics and AIEC challenge on murine intestinal dysbiosis and neutrophil extracellular trap activation, which is a critical component of the neutrophil antimicrobial repertoire. Methods Male C57BL/6 mice were administered vancomycin and gentamicin (once daily, 3 days), and subsequently challenged with AIEC strain LF82 (once daily, 2 days). Perturbation of the gut microbiota was monitored using a combination of molecular and phylogenetic analyses. The impact of commensal and dysbiotic gut bacterial communities on neutrophil extracellular trap mobilization and intestinal redox balance was also quantified. Results Exposure of neutrophils to murine commensal gut microbial communities activated neutrophil extracellular trap formation. The capacity of neutrophils to cast these web-like structures was exacerbated following antibiotic and AIEC-associated intestinal dysbiosis, highlighting the possible overgrowth of immune-activating intestinal pathobionts. Intestinal dysbiosis was associated with an elevated capacity of the cultivated gut bacteria to produce reactive oxygen species in vitro, and increased colonic oxidative stress in vivo. Conclusions Together, these data provide new insights into the detrimental effects of antibiotics on the gut microbiota, with clinically relevant implications for intestinal dysbiosis on neutrophil function and intestinal redox balance.

The intestinal microbiota plays a key role in shaping the host immune system. Perturbation of gut microbial composition, termed dysbiosis, is associated with an increased susceptibility to intestinal pathogens and is a hallmark of a number of inflammatory, metabolic, and infectious diseases. The prospect of mining the commensal gut microbiota for bacterial strains that can impact immune function represents an attractive strategy to counteract dysbiosis and resulting disease. In this study, we show that selective enrichment of commensal gut lactobacilli protects against the murine pathogen Citrobacter rodentium, a well-characterized model of enteropathogenic and enterohemorrhagic Escherichia coli infection. The lactobacilli-enriched bacterial culture prevented the expansion of Gammaproteobacteria and Actinobacteria and was associated with improved indexes of epithelial barrier function (dextran flux), transmissible crypt hyperplasia, and tissue inflammatory cytokine levels. Moreover, cultivation of gut bacteria from Citrobacter rodentium-infected mice reveals the differential capacity of bacterial subsets to mobilize neutrophil oxidative burst and initiate the formation of weblike neutrophil extracellular traps. Our findings highlight the beneficial effects of a lactobacilli -enriched commensal gut microenvironment and, in the context of an intestinal barrier breach, the ability of neutrophils to immobilize both commensal and pathogenic bacteria.

Background and Aim Oral mucosal pathologies are frequent in inflammatory bowel disease (IBD). Since host–microbiome interactions are implicated in the pathogenesis of IBD, in this study the potential for changes affecting the oral microbiome was evaluated using two complementary mouse models of colitis: either chemically (dextran sulfate sodium) or with Citrobacter rodentium infection. Methods After sacrifice, the tongue, buccal mucosa, saliva, colon, and stool samples were collected for analyses. Denaturing gradient gel electrophoresis was performed to assess bacterial 16S rRNA gene profiles. Relative changes were determined using quantitative polymerase chain reaction analysis for the phyla Bacteroidetes, Firmicutes, Spirochetes, and Actinobacteria, classes Gammaproteobacteria and Betaproteobacteria, and the genera Bacillus and Lactobacillus. These groups represent over 99% of the oral microbiota of healthy C57BL/6 mice. Results Both models of colitis changed the oral microbiome, with the buccal microbiome being the most resistant to alterations in composition (maximum 1.8% change, vs tongue maximum 2.5% change, and saliva which demonstrated up to 7.2% total changes in microbiota composition). Changes in the oral microbiota were greater after dextran sulfate sodium challenge, compared with C. rodentium-induced colitis. Using cluster analysis, tongue and buccal mucosal microbiota composition changed ∼ 5%, saliva ∼ 35%, while stool changed ∼ 10%. Conclusion These findings indicate that dysbiosis observed in murine models of colitis is associated with changes in the composition of bacteria present in the oral cavity and in saliva. Such changes in the oral microbiota could be relevant to the etiology and management of oral mucosal pathologies observed in IBD patients.

Background Adherent-invasive Escherichia coli (AIEC) colonization has been strongly implicated in the pathogenesis of Crohn's disease. Environmental triggers such as vitamin D deficiency have emerged as key factors in the pathogenesis of inflammatory bowel diseases. The aim of this study was to investigate the effects of 1,25(OH)2D3 on AIEC infection-induced changes in vivo and in vitro. Methods Barrier function was assessed in polarized epithelial Caco-2-bbe cells grown in medium with or without vitamin D and challenged with AIEC strain LF82. Weaned C57BL/6 mice were fed either a vitamin D-sufficient or -deficient diet for 5 weeks and then infected with AIEC, in the absence and presence of low-dose dextran sodium sulphate. Disease severity was assessed by histological analysis and in vivo intestinal permeability assay. Presence of invasive bacteria was assessed by transmission electron microscopy. Results Caco-2-bbe cells incubated with 1,25(OH)2D3 were protected against AIEC-induced disruption of transepithelial electrical resistance and tight-junction protein redistribution. Vitamin D-deficient C57BL/6 mice given a course of 2% dextran sodium sulphate exhibited pronounced epithelial barrier dysfunction, were more susceptible to AIEC colonization, and showed exacerbated colonic injury. Transmission electron microscopy of colonic tissue from infected mice demonstrated invasion of AIEC and fecal microbiome analysis revealed shifts in microbial communities. Conclusions These data show that vitamin D is able to mitigate the deleterious effects of AIEC on the intestinal mucosa, by maintaining intestinal epithelial barrier homeostasis and preserving tight-junction architecture. This study highlights the association between vitamin D status, dysbiosis, and Crohn's disease.

Background Combined immunodeficiency (CID) is a T-cell defect frequently presenting with recurrent infections, as well as associated immune dysregulation manifesting as autoimmunity or allergic inflammation. Objective We sought to identify the genetic aberration in 4 related patients with CID, early-onset asthma, eczema, and food allergies, as well as autoimmunity. Methods We performed whole-exome sequencing, followed by Sanger confirmation, assessment of the genetic variant effect on cell signaling, and evaluation of the resultant immune function. Results A heterozygous novel c.C88T 1-bp substitution resulting in amino acid change R30W in caspase activation and recruitment domain family member 11 (CARD11) was identified by using whole-exome sequencing and segregated perfectly to family members with severe atopy only but was not found in healthy subjects. We demonstrate that the R30W mutation results in loss of function while also exerting a dominant negative effect on wild-type CARD11. The CARD11 defect altered the classical nuclear factor κB pathway, resulting in poor in vitro T-cell responses to mitogens and antigens caused by reduced secretion of IFN-γ and IL-2. Conclusion Unlike patients with biallelic mutations in CARD11 causing severe CID, the R30W defect results in a less profound yet prominent susceptibility to infections, as well as multiorgan atopy and autoimmunity.

BACKGROUND Vitamin D, an important modulator of the immune system, has been shown to protect mucosal barrier homeostasis. This study investigates the effects of vitamin D deficiency on infection-induced changes in intestinal epithelial barrier function in vitro and on Citrobacter rodentium-induced colitis in mice. METHODS Polarized epithelial Caco2-bbe cells were grown in medium with or without vitamin D and challenged with enterohemorrhagic Escherichia coli O157:H7. Barrier function and tight junction protein expression were assessed. Weaned C57BL/6 mice were fed either a vitamin D-sufficient or vitamin D-deficient diet and then infected with C. rodentium. Disease severity was assessed by histological analysis, intestinal permeability assay, measurement of inflammatory cytokine levels, and microbiome analysis. RESULTS 1,25(OH)2D3 altered E. coli O157:H7-induced reductions in transepithelial electrical resistance (P < .01), decreased permeability (P < .05), and preserved barrier integrity. Vitamin D-deficient mice challenged with C. rodentium demonstrated increased colonic hyperplasia and epithelial barrier dysfunction (P < .0001 and P < .05, respectively). Vitamin D deficiency resulted in an altered composition of the fecal microbiome both in the absence and presence of C. rodentium infection. CONCLUSIONS This study demonstrates that vitamin D is an important mediator of intestinal epithelial defenses against infectious agents. Vitamin D deficiency predisposes to more-severe intestinal injury in an infectious model of colitis.

Neutrophil extracellular traps (NETs) are an essential component of the antimicrobial repertoire and represent an effective means by which neutrophils capture, contain, and kill microorganisms. However, the uncontrolled or excessive liberation of NETs also damages surrounding cells and can contribute to disease pathophysiology. Alterations in the gut microbiota, as well as the presence of local and systemic markers of inflammation, are strongly associated with the manifestation of a spectrum of intestinal disorders, including chronic inflammatory bowel disease. Although probiotics exert beneficial effects on gut homeostasis, their direct effect on neutrophils, which are abundant in the setting of intestinal inflammation, remains unclear. In this study, we investigated the effects of nonpathogenic, enteropathogenic, and probiotic bacteria on the dynamics of NET formation. Using murine bone marrow–derived neutrophils and the neutrophil-differentiated human myeloid cell line d.HL-60, we demonstrate for the first time, to our knowledge, that probiotic Lactobacillus rhamnosus strain GG inhibits both PMA- and Staphylococcus aureus–induced formation of NETs. Moreover, probiotic L. rhamnosus strain GG had potent antioxidative activity: dampening reactive oxygen species production and phagocytic capacity of the neutrophils while protecting against cell cytotoxicity. Within the milieu of the gut, this represents a novel mechanism by which probiotics can locally dampen innate immune responses and confer desensitization toward luminal Ags.

Roifman syndrome is an association of humoral immunodeficiency, growth retardation, spondyloepiphyseal dysplasia, developmental delay, retinal dystrophy, and unique dysmorphism. Compound heterozygote mutations in the RNU4ATAC gene, an essential component of the minor spliceosome, were found to be the culprit for this disorder. Here we report a novel mutation in the RNU4ATAC gene, involving position 116. This mutation redefines the Sm protein binding site of this gene.Statement of novelty: We report here a patient with a novel mutation in the Sm protein-binding site that redefined its boundaries to include position 116.

Background and purpose: Acemetacin is a non-steroidal anti-inflammatory drug which is rapidly bioconverted to indomethacin, but produces significantly less gastric damage than indomethacin. This study was performed to investigate several possible mechanisms that could account for the gastrointestinal tolerability of acemetacin. Experimental approach: The gastric and intestinal damaging effects of acemetacin and indomethacin were examined in the rat. Effects of the drugs on blood levels of leukotriene B4 and thromboxane B2, on leukocyte-endothelial adherence in postcapillary mesenteric venules, and on gastric expression of tumour necrosis factor-a (TNF-a) were determined. The two drugs were also compared for gastric toxicity in rats pretreated with inhibitors of COX-2 and NOS. Key results: Acemetacin induced significantly less gastric and intestinal damage than indomethacin, despite markedly suppressing COX activity. Indomethacin, but not acemetacin, significantly increased leukocyte adherence within mesenteric venules, and gastric expression of TNF-a. Pretreatment with L-nitro-arginine methyl ester or lumiracoxib increased the severity of indomethacin-induced gastric damage, but this was not the case with acemetacin. Conclusions and implications: The increased gastric and intestinal tolerability of acemetacin may be related to the lack of induction of leukocyte–endothelial adherence. This may be attributable to the reduced ability of acemetacin to elevate leukotriene-B4 synthesis and TNF-a expression, compared to indomethacin, despite the fact that acemetacin is rapidly

Annexin 1 is an anti-inflammatory protein that plays a key role in innate immunity by modulating the activation of several types of cells, including neutrophils. Here we have developed a cleavage assay using tagged annexin 1 and observed marked activity in the membrane fraction of activated neutrophils. A combination of inhibitors, transfected cells, and proteomic analyses allowed us to identify proteinase 3 as the main enzyme responsible for this cleavage in the N terminus region of the protein, at least in the context of neutrophil activation. Because annexin 1 is an important endogenous anti-inflammatory mediator, blocking its cleavage by proteinase 3 would augment its homeostatic pro-resolving actions and could represent an opportunity for innovative anti-inflammatory drug discovery.

Oral mucosal pathologies are frequent in inflammatory bowel disease (IBD). Since host-microbiome interactions are implicated in the pathogenesis of IBD, in this study the potential for changes affecting the oral microbiome was evaluated using two complementary mouse models of colitis: either chemically (dextran sulfate sodium) or with Citrobacter rodentium infection.After sacrifice, the tongue, buccal mucosa, saliva, colon, and stool samples were collected for analyses. Denaturing gradient gel electrophoresis was performed to assess bacterial 16S rRNA gene profiles. Relative changes were determined using quantitative polymerase chain reaction analysis for the phyla Bacteroidetes, Firmicutes, Spirochetes, and Actinobacteria, classes Gammaproteobacteria and Betaproteobacteria, and the genera Bacillus and Lactobacillus. These groups represent over 99% of the oral microbiota of healthy C57BL/6 mice.Both models of colitis changed the oral microbiome, with the buccal microbiome being the most resistant to alterations in composition (maximum 1.8% change, vs tongue maximum 2.5% change, and saliva which demonstrated up to 7.2% total changes in microbiota composition). Changes in the oral microbiota were greater after dextran sulfate sodium challenge, compared with C. rodentium-induced colitis. Using cluster analysis, tongue and buccal mucosal microbiota composition changed ∼ 5%, saliva ∼ 35%, while stool changed ∼ 10%.These findings indicate that dysbiosis observed in murine models of colitis is associated with changes in the composition of bacteria present in the oral cavity and in saliva. Such changes in the oral microbiota could be relevant to the etiology and management of oral mucosal pathologies observed in IBD patients.

Antibiotic (Abx) therapy alters gut microbial composition and is associated with an increased risk of pathogen infection. However, little is known about the ability of Abx to foster the growth of pathobionts - commensal microbes that, as a result of select environmental stresses, become pathogenic. Here, we measured the ability of Abx-disturbed gut microflora to induce neutrophil extracellular traps (NET), protease-rich ‘footprints’ left by neutrophils to capture and kill microbes. C57BL/6 mice were administered vancomycin (40 mg/kg/d) and gentamicin (3 mg/kg/d) once daily for 3d. Fecal pellets were collected prior to Abx and for 16d thereafter, and incubated in either Tryptic Soy (TS), deMan-Rogosa-Sharpe (MRS) or Luria-Bertani (LB) broth (37°C, 16 h) to enrich either all microbes, Lactobacilli, or Escherichia coli, respectively. The capacity to induce NET from bone marrow-derived neutrophils (BMDN) was quantified by measurement of extracellular DNA and visualized by fluorescence microscopy. Microbial co...

Neutrophils are some of the first leukocytes to respond to inflammatory stimuli. Once recruited, these cells are equipped with an assortment of proteolytic enzymes and antimicrobial factors that disarm and degrade pathogens. Neutrophils employ a highly novel mechanism to contain and trap bacteria in the local inflammatory microenvironment, termed neutrophil extracellular traps (NETs). During NET formation, neutrophils eject weblike structures of chromatin, which captures and immobilizes invading pathogens. In this chapter, we describe protocols to isolate bone marrow-derived neutrophils from mice. We further describe in vitro methods to spectrophotometrically quantify, immunolabel, and visualize NET structures.

Mucus is known to contribute significantly to the prevention and repair of mucosal damage throughout the gastrointestinal tract. Although not normally expressed in the stomach, mucin-2 (MUC-2, encoded by the MUC2 gene) is expressed in certain disease states. The aim of this study was to determine in a mouse model whether the absence of Muc-2 would result in impaired susceptibility to and healing of gastric mucosal injury. Acute gastric damage was induced in mice deficient in Muc-2 and in wild-type controls, through oral administration of indomethacin. Chronic gastric ulcers were induced by serosal application of acetic acid. The extent of injury and the extent of healing of the damage over time were examined in both models. Indomethacin administration caused similar levels of gastric damage in Muc-2–deficient and wild-type mice, but the erosions healed more slowly in the former. Acetic acid–induced gastric ulcers were initially similar in size in Muc-2–deficient and wild-type mice of both sexes, but ulcer healing was significantly impaired in male Muc-2–deficient mice. Induction of cyclooxygenase-2 in the stomach, in response to indomethacin- or acetic acid–induced ulceration, was significantly reduced in male Muc-2–deficient mice. This phenomenon, and the sex specificity, was also apparent in bone marrow–derived macrophages stimulated with endotoxin. These results demonstrate a marked impairment of gastric mucosal repair in male Muc-2–deficient mice that may be related to an insufficient induction of cyclooxygenase-2, an enzyme known to contribute to mucosal repair.

Background & Aims Proton pump inhibitors (PPIs) and nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used classes of drugs, with the former frequently coprescribed to reduce gastroduodenal injury caused by the latter. However, suppression of gastric acid secretion by PPIs is unlikely to provide any protection against the damage caused by NSAIDs in the more distal small intestine. Methods Rats were treated with antisecretory doses of omeprazole or lanzoprazole for 9 days, with concomitant treatment with anti-inflammatory doses of naproxen or celecoxib on the final 4 days. Small intestinal damage was blindly scored, and changes in hematocrit were measured. Changes in small intestinal microflora were evaluated by denaturing gradient gel electrophoresis and reverse-transcription polymerase chain reaction. Results Both PPIs significantly exacerbated naproxen- and celecoxib-induced intestinal ulceration and bleeding in the rat. Omeprazole treatment did not result in mucosal injury or inflammation; however, there were marked shifts in numbers and types of enteric bacteria, including a significant reduction (∼80%) of jejunal Actinobacteria and Bifidobacteria spp. Restoration of small intestinal Actinobacteria numbers through administration of selected ( Bifidobacteria enriched) commensal bacteria during treatment with omeprazole and naproxen prevented intestinal ulceration/bleeding. Colonization of germ-free mice with jejunal bacteria from PPI-treated rats increased the severity of NSAID-induced intestinal injury, as compared with mice colonized with bacteria from vehicle-treated rats. Conclusions PPIs exacerbate NSAID-induced intestinal damage at least in part because of significant shifts in enteric microbial populations. Prevention or reversal of this dysbiosis may be a viable option for reducing the incidence and severity of NSAID enteropathy.

NSAIDs are among the most widely used medications, but the side effects of these drugs frequently include gastrointestinal (GI) ulceration and bleeding. COX-2 inhibitors were designed that were claimed to be devoid of ulcer-promoting effects; however, this promise has been unfulfilled, and there are concerns about the cardiovascular safety of COX-2 inhibitors. Several novel approaches to developing GI-sparing NSAIDs have been used, with promising preclinical and clinical results. Selective inhibition of terminal PG synthases, and NSAIDs modified to slowly release gastroprotective gaseous mediators (ie, nitric oxide or hydrogen sulfide) may offer renewed hope for developing anti-inflammatory therapies with greatly reduced GI toxicity.

real-time reverse transcription-polymerase chain reaction . To clarify the role of HMGB1 in healing of gastric ulcer, the mice were intraperitoneally administered mouse recombinant HMGB1 (rHMGB1), anti-HMGB1 neutralizing antibodies or nonspecific chicken IgY after the induction of ulcer.Results: At day 4 after ulcer induction, mean ulcer sizes did not differ among the 4 groups. Endothelial cells and inflammatory cells such as macrophages in the ulcerous region showed immunoreactivity for TLR2 and TLR4 and RAGE proteins. By day 9, the ulcer size in RAGE KO mice and TLR4 KO mice was 40% smaller than that in wild-type mice, while there was no difference in ulcer sizes between wild-type mice and TLR2 KO mice. Deficiency of RAGE and TLR4 markedly inhibited the increase in expression of TNF-αmRNA in ulcerous tissue. Administration of rHMGB1 delayed the healing of gastric ulcer (ulcer index: 1.39 ± 0.30 mm2 in the vehicle-treated mice and 4.52 ± 0.35 mm2 in rHMGB1-treated mice), accompanied by increase in expression of TNF-α mRNA and MPO activities in ulcerous tissue, while administration of anti-HMGB1 antibody enhanced ulcer healing by day 9 (ulcer index: 2.90 ± 0.86 mm2 in non-specific IgY-treated mice, 1.46 ± 0.80 mm2 in neutralizing antibody for HMGB1-treated mice). Conclusion: These results suggest that HMGB1 is a critical factor that delays healing of gastric ulcer not via TLR2 but via TLR4 and RAGE.

Background & Aims Hydrogen sulfide (H 2 S) is an endogenous gaseous mediator of mucosal defense with antiinflammatory effects that promote ulcer healing. The effects of H 2 S during the pathogenesis of colitis have not been established. We analyzed the contribution of H 2 S to inflammation and ulceration of the colon in a rat model of colitis. Methods Colitis was induced by intracolonic administration of trinitrobenzene sulfonic acid. The ability of the colon to synthesize H 2 S was studied over the course of the resolution of the colitis. Expression of 2 enzymes involved in the synthesis of H 2 S and the effects of inhibitors of these enzymes were examined. We also examined the effects of H 2 S donors on the resolution of colitis. Results The capacity for the colon to produce H 2 S increased markedly over the first days after induction of colitis and then declined toward control levels as the colitis was resolved. Inhibition of colonic H 2 S synthesis markedly exacerbated the colitis, resulting in significant mortality. Inhibition of H 2 S synthesis in healthy rats resulted in inflammation and mucosal injury in the small intestine and colon along with down-regulation of cyclooxygenase-2 messenger RNA expression and prostaglandin synthesis. Intracolonic administration of H 2 S donors significantly reduced the severity of colitis and reduced colonic expression of messenger RNA for the proinflammatory cytokine tumor necrosis factor α. Conclusions In rats, H 2 S modulates physiological inflammation and contributes to the resolution of colitis.