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Background Patients with Crohn’s disease (CD) are at risk of complications. Performance characteristics of a decision support tool assessing the risk of CD complications were evaluated. Methods CDPATH (formerly called the Personalized Risk and Outcome Prediction Tool [PROSPECT]) was calibrated and validated in 2 cohorts. Tool prediction of disease characteristics was assessed using Cox regression and Harrell’s C-statistic. Results All associations of CD complications and CDPATH components were significant except perianal location. There was a significant association between individualized risk assessment scores and CD complications in both cohorts. Conclusion CDPATH is validated as a clinical decision support tool for assessing the risk of CD complications.

Introduction: Advancing new therapies from discovery to development usually requires proof-of-concept in animal models to justify the costs of continuing the program. While animal models are useful for understanding the mechanism of action (MOA) of a target, limitations of many published colitis models restrict their value to predict clinical efficacy.Areas covered: The authors focused their literature search on published studies of chronic animal models used to evaluate the pre-clinical efficacy of therapeutic molecules subsequently evaluated in clinical trials for UC. The UC therapies evaluated were anti-α4β7, anti-IL13, anti-IL12p40, and anti-IL23p19. The models of chronic colitis evaluating these molecules were: mdra1a-/-, chronic dextran sulfate sodium (DSS), chronic 2,4,6-trinitrobenzene sulfonic acid (TNBS), and the T cell transfer model.Expert opinion: While some models provide insight into target MOA in UC, none is consistently superior in predicting efficacy. Evaluation of multiple models, with varying mechanisms of colitis induction, is needed to understand potential drug efficacy. Additional models of greater complexity, reflecting the disease chronicity/heterogeneity seen in humans, are needed. Although helpful in prioritizing targets, animal models alone will likely not improve outcomes of UC clinical trials. Transformational changes to clinical efficacy will likely only occur when precision medicine approaches are employed.

The host receptor for severe acute respiratory syndrome coronavirus 2, angiotensin-converting enzyme 2 (ACE2), is highly expressed in small bowel (SB). Our aim was to identify factors influencing intestinal ACE2 expression in Crohn's disease (CD), ulcerative colitis (UC), and non-inflammatory bowel disease (IBD) controls.Using bulk RNA sequencing or microarray transcriptomics from tissue samples (4 SB and 2 colonic cohorts; n = 495; n = 387 UC; n = 94 non-IBD), we analyzed the relationship between ACE2 with demographics and disease activity and prognosis. We examined the outcome of anti-tumor necrosis factor and anti-interleukin-12/interleukin-23 treatment on SB and colonic ACE2 expression in 3 clinical trials. Univariate and multivariate regression models were fitted.ACE2 levels were consistently reduced in SB CD and elevated in colonic UC compared with non-IBD controls. Elevated SB ACE2 was also associated with demographic features (age and elevated body mass index) associated with poor coronavirus disease 2019 outcomes. Within CD, SB ACE2 was reduced in patients subsequently developing complicated disease. Within UC, colonic ACE2 was elevated in active disease and in patients subsequently requiring anti-tumor necrosis factor rescue therapy. SB and colonic ACE2 expression in active CD and UC were restored by anti-cytokine therapy, most notably in responders.Reduced SB but elevated colonic ACE2 levels in IBD are associated with inflammation and severe disease, but normalized after anti-cytokine therapy, suggesting compartmentalization of ACE2-related biology in SB and colonic inflammation. The restoration of ACE2 expression with anti-cytokine therapy might be important in the context of severe acute respiratory syndrome coronavirus 2 infection and potentially explain reports of reduced morbidity from coronavirus disease 2019 in IBD patients treated with anti-cytokines.

The etiology of inflammatory bowel disease (IBD) is not fully understood but is likely influenced by numerous factors such as genetic predisposition, environmental factors, like the microbiota, and social behaviors, including smoking and diet. In addition to anti-tumor necrosis factor therapy, we now have integrin inhibitors that target lymphocyte trafficking to the gastrointestinal tract (vedolizumab and natalizumab); however, unmet medical needs remain. Although several immunologic pathways have been implicated in the pathogenesis of IBD, targeting these with drug therapy has produced mixed results. Recent drug failures, particularly anti-interleukin-17 (anti-IL17) in Crohn’s disease and anti-IL13 in ulcerative colitis, highlight our fundamental lack of understanding of the impact of pathogenic heterogeneity in the treatment of IBD. In addition to a “failure of mechanism,” other reasons for drug failure may include issues with the drug itself—for example, insufficient activity, or lack of targeting, inadequate trial design or dosing, or potentially our inability to characterize patients who may be more (or less) responsive to a specific therapy. This review summarizes some of the successes and failures and evaluates therapies currently under investigation for IBD.

Background and Aims Heterogeneity in Crohn’s disease [CD] provides a challenge for the development of effective therapies. Our goal was to define a unique molecular signature for severe, refractory CD to enable precision therapy approaches to disease treatment and to facilitate earlier intervention in complicated disease. Methods We analysed clinical metadata, genetics, and transcriptomics from uninvolved ileal tissue from CD patients who underwent a single small bowel resection. We determined transcriptional risk scores, cellular signatures, and mechanistic pathways that define patient subsets in refractory CD. Results Within refractory CD, we found three CD patient subgroups [CD1, CD2, and CD3]. Compared with CD1, CD3 was enriched for subjects with increased disease recurrence after first surgery [OR = 6.78, p = 0.04], enhanced occurrence of second surgery [OR = 5.07, p = 0.016], and presence of perianal CD [OR = 3.61, p = 0.036]. The proportion of patients with recurrence-free survival was smaller in CD3 than in CD1 (p = 0.02, median survival time [months] in CD1 = 10 and CD3 = 6). Overlaying differential gene expression between CD1 and CD3 on CD subgroup-associated genetic polymorphisms identified 174 genes representing both genetic and biological differences between the CD subgroups. Pathway analyses using this unique gene signature indicated eukaryotic initiation factor 2 [eIF2] and cyclic adenosine monophosphate [cAMP] signalling to be dominant pathways associated with CD3. Furthermore, the severe, refractory subset, CD3, was associated with a higher transcriptional risk score and enriched with eosinophil and natural killer T [NKT] cell gene signatures. Conclusion We characterized a subset of severe, refractory CD patients who may need more aggressive treatment after first resection and who are likely to benefit from targeted therapy based on their genotype and tissue gene expression signature.

Background And Aims The host receptor for severe acute respiratory syndrome coronavirus 2, angiotensin-converting enzyme 2 (ACE2), is highly expressed in small bowel (SB). Our aim was to identify factors influencing intestinal ACE2 expression in Crohn's disease (CD), ulcerative colitis (UC), and non–inflammatory bowel disease (IBD) controls. Methods Using bulk RNA sequencing or microarray transcriptomics from tissue samples (4 SB and 2 colonic cohorts; n = 495; n = 387 UC; n = 94 non-IBD), we analyzed the relationship between ACE2 with demographics and disease activity and prognosis. We examined the outcome of anti–tumor necrosis factor and anti–interleukin-12/interleukin-23 treatment on SB and colonic ACE2 expression in 3 clinical trials. Univariate and multivariate regression models were fitted. Results ACE2 levels were consistently reduced in SB CD and elevated in colonic UC compared with non-IBD controls. Elevated SB ACE2 was also associated with demographic features (age and elevated body mass index) associated with poor coronavirus disease 2019 outcomes. Within CD, SB ACE2 was reduced in patients subsequently developing complicated disease. Within UC, colonic ACE2 was elevated in active disease and in patients subsequently requiring anti–tumor necrosis factor rescue therapy. SB and colonic ACE2 expression in active CD and UC were restored by anti-cytokine therapy, most notably in responders. Conclusions Reduced SB but elevated colonic ACE2 levels in IBD are associated with inflammation and severe disease, but normalized after anti-cytokine therapy, suggesting compartmentalization of ACE2-related biology in SB and colonic inflammation. The restoration of ACE2 expression with anti-cytokine therapy might be important in the context of severe acute respiratory syndrome coronavirus 2 infection and potentially explain reports of reduced morbidity from coronavirus disease 2019 in IBD patients treated with anti-cytokines.

OBJECTIVES: Flow cytometry (FC) aids in characterization of cellular and molecular factors involved in pathologic immune responses. Although FC has potential to facilitate early drug development in inflammatory bowel disease, interlaboratory variability limits its use in multicenter trials. Standardization of methods may address this limitation. We compared variability in FC-aided quantitation of T-cell responses across international laboratories using three analytical strategies. METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from three healthy donors, stimulated with phorbol 12-myristate 13-acetate and ionomycin at a central laboratory, fixed, frozen, and shipped to seven international laboratories. Permeabilization and staining was performed in triplicate at each laboratory using a common protocol and centrally provided reagents. Gating was performed using local gating with a local strategy (LGLS), local gating with a central strategy (LGCS), and central gating (CG). Median cell percentages were calculated across triplicates and donors, and reported for each condition and strategy. The coefficient of variation (CV) was calculated across laboratories. Between-strategy comparisons were made using a two-way analysis of variance adjusting for donor. RESULTS: Mean interlaboratory CV ranged from 1.8 to 102.1% depending on cell population and gating strategy (LGLS, 4.4-102.1%; LGCS, 10.9-65.6%; CG, 1.8-20.9%). Mean interlaboratory CV differed significantly across strategies and was consistently lower with CG. CONCLUSIONS: Central gating was the only strategy with mean CVs consistently lower than 25%, which is a proposed standard for pharmacodynamic and exploratory biomarker assays

Lymphocyte recruitment maintains intestinal immune homeostasis but also contributes to inflammation. The orphan chemoattractant receptor GPR15 mediates regulatory T cell homing and immunosuppression in the mouse colon. We show that GPR15 is also expressed by mouse TH17 and TH1 effector cells, and is required for colitis in a model that depends on their trafficking to the colon. In humans GPR15 is expressed by effector cells including pathogenic TH2 cells in ulcerative colitis, but is not expressed by regulatory T (Treg) cells. The TH2 transcriptional activator GATA-3 and the Treg–associated transcriptional repressor FOXP3 robustly bind human, but not mouse, GPR15 enhancer sequences, correlating with expression. Our results highlight species differences in GPR15 regulation, and suggest it as a potential therapeutic target for colitis.

Background & Aims Variants in the tumor necrosis factor superfamily member 15 gene ( TNFSF15 , also called TL1A ) have been associated with risk for inflammatory bowel disease (IBD). TL1A affects expression of multiple cytokines to promote mucosal inflammation. Little is known about the TL1A-response pathways that regulate cytokine expression. We investigated T-cell gene expression patterns to determine the mechanisms by which TL1A regulates cytokine production, and whether these associate with outcomes of patients with Crohn's disease (CD). Methods Peripheral T cells isolated from normal donors were cultured with TL1A. We performed gene expression profile analysis by RNA sequencing of subsets of interferon gamma (IFNG)-producing and non-producing cells purified by flow cytometry. Unsupervised hierarchical clustering analysis was used to identify gene expression differences between these subsets. Ribonuclease T2 gene ( RNASET2 ) expression and methylation were assessed by quantitative trait loci analyses. Clinical characteristics of patients (complications, resistance to therapy, and recurrence time) were associated with single nucleotide polymorphisms in RNASET2 . We performed motif screening to identify polymorphisms that disrupt transcription factor binding sites. Levels of RNASET2 were knocked down with small interfering RNA in CD4 + T cells and the effect on protein expression was determined by proteomic analysis and cytokine production. Cell aggregation was measured by flow cytometry. Results We identified 764 genes with at least a 2-fold difference in TL1A-mediated expression between IFNG-secreting and non-secreting T cells ( P −5 ). Many of these genes were located near IBD susceptibility variants. RNASET2 was the only IBD risk-associated gene with >5-fold down-regulation in the IFNG-secreting subset. RNASET2 disease risk variants were associated with decreased expression in peripheral and mucosal tissues and DNA hypermethylation in CD patients requiring surgical intervention. RNASET2 disease risk variants were associated in CD patients with more complicated disease or resistance to therapy, defined in part by failed response to treatment, increased length of intestinal resection, shorter time to repeat surgery, and high Rutgeerts score (>2) in postoperative endoscopy. The RNASET2 variant rs2149092 was predicted to disrupt a consensus binding site for the transcription factor ETS within an enhancer region. Expression of RNASET2 correlated with expression of ETS. RNASET2 knockdown in T cells increased expression of IFNG and intercellular adhesion molecule 1 (ICAM1) and induced T-cell aggregation. A blocking antibody against (ILFA1), disrupting the lymphocyte function-associated antigen 1−intercellular adhesion molecule 1 interaction, reduced T-cell production of IFNG. Conclusions We identified decreased expression of RNASET2 as a component of TL1A-mediated increase in production of IFNG and as a potential biomarker for patients with severe CD. Further study of the role of RNASET2 in regulating mucosal inflammation may lead to development of novel therapeutic targets.

Interleukin-31 (IL-31) is a recently discovered cytokine expressed in many human tissues, and predominantly by activated CD4(+) T cells. IL-31 signals through a heterodimeric receptor consisting of IL-31 receptor alpha (IL-31RA) and oncostatin M receptor beta (OSMR). Earlier studies have shown involvement of IL-31 and its receptor components IL-31RA and OSMR in atopic dermatitis, pruritus and Th2-weighted inflammation at the mRNA level. The aim of this study was to investigate IL-31 protein expression in skin of such conditions. Immunohistochemical staining for IL-31, IL-31RA and OSMR was performed in formalin-fixed paraffin-embedded biopsy specimens. IL-31 expression was increased in the inflammatory infiltrates from skin biopsies taken from subjects with atopic dermatitis, compared with controls (p ≤ 0.05). IL-31, IL-31RA and OSMR protein immunoreactivity was not increased in biopsies from subjects with other Th2-weighted and pruritic skin diseases. Our results confirm, at the protein level, the relationship between IL-31 expression and atopic dermatitis. Our results do not support a general relationship between expression of IL-31/IL-31R and pruritic or Th2-mediated diseases.

Background: Interleukin-31 (IL-31), a novel cytokine, is upregulated in atopic dermatitis skin lesions in humans and skin lesions in the NC/Nga mice, a murine model for atopic dermatitis. Objective: Here, we investigated the effect of a monoclonal IL-31 antibody on scratching behaviour, weight gain and dermatitis in NC/Nga mice. Methods: Mice were divided into three groups, n = 10 in each group. Mice were given monoclonal IL-31 rat-anti-mouse antibody 10 mg/kg or albumin intraperitoneally every fifth day for seven weeks. In addition, the mice in one group were not exposed to any form of intervention. The dermatitis score was clinically assessed twice a week. The scratching behaviour was automatically detected and objectively evaluated. Results: Intervention with IL-31 antibody 10 mg/kg intraperitoneally every fifth day in NC/Nga mice from age 7 weeks reduced the scratching behaviour, but did not have any impact on weight gain or dermatitis. Conclusion: IL-31 antibody reduces scratching behaviour in an atopic dermatitis-like murine model during the onset of clinical skin manifestations. Our findings suggest IL-31 antibody as a new potential therapeutic approach for pruritus in atopic dermatitis and other pruritic diseases.

Summary Background Increased levels of serum IgE are associated with greater asthma prevalence and disease severity. IgE depletion using an anti-IgE monoclonal antibody has met with success in the treatment of moderate-to-severe and severe persistent allergic asthma. Objective To test whether B cell-targeted therapy is a more effective treatment for airway hyperresponsiveness (AHR) in a murine model compared with IgE-depletion. Methods We delivered soluble mTACI-Ig, a receptor for the B cell survival factors BLyS (B Lymphocyte Stimulator) and APRIL (A PRoliferation-Inducing Ligand), or anti-IgE to allergen-sensitized mice before airway challenge with allergen. Results mTACI-Ig treatment reduced circulating mature B cell levels in the blood, while anti-IgE treatment had no effect on B cell counts. Both mTACI-Ig and anti-IgE decreased the levels of total and allergen-specific IgE in the serum. Histopathologic analysis of lungs showed a reduction in disease severity scores for both treatment groups, but results were more pronounced in mTACI-Ig-treated mice. Neutrophil and eosinophil numbers in the bronchoalveolar lavage (BAL) were significantly reduced following mTACI-Ig treatment, but not after anti-IgE delivery. BLyS and APRIL blockade also resulted in a significant decrease in IL-4 and eotaxin mRNA and IL-4 and KC protein levels in total lung homogenates and BAL fluid, respectively. Finally, mTACI-Ig treatment was more effective than anti-IgE treatment in reducing AHR to inhaled antigen. Conclusions Our data demonstrate that delivery of mTACI-Ig is a more effective treatment than anti-IgE mAb in a murine model of AHR.

There are many types of colitis models in animals that researchers use to elucidate the mechanism of action of human inflammatory bowel disease (IBD). These models are also used to test novel therapeutics and therapeutic treatment regimens. Here, we will review the characteristics of the mdr1a -/- model of spontaneous colitis that we believe make this model an important part of the IBD researcher's toolbox. We will also share new data that will reinforce the fact that this model is relevant in the study of IBD. Mdr1a -/- mice lack the murine multiple drug resistance gene for P-glycoprotein 170 that is normally expressed in multiple tissues including intestinal epithelial cells. These mice spontaneously develop a form of colitis at around 12 wk of age. The fact that the complexity of this model mirrors the complexity of disease in humans, as well as recent literature that links MDR1 polymorphisms in humans to Crohn's Disease and Ulcerative Colitis, makes this an appropriate animal model to study.

Discrimination between beneficial commensal organisms and potentially harmful pathogens is a central component of the essential role that gut immune cells play in maintaining the balance between immune activation and tolerance. Antigen presenting cells (APC) are the key to this process, and the type of APC, including epithelial cells, B cells, macrophages, and dendritic cells (DC), in the gut is varied. The purpose of this review is to focus on the vast amount of data that has recently been generated on gastrointestinal dendritic cells in the context of their potential function and contribution to mucosal immunity, tolerance, and disease.

T cell-derived cytokines are important in the development of an effective immune response, but when dysregulated they can promote disease. Here we identify a four-helix bundle cytokine we have called interleukin 31 (IL-31), which is preferentially produced by T helper type 2 cells. IL-31 signals through a receptor composed of IL-31 receptor A and oncostatin M receptor. Expression of IL-31 receptor A and oncostatin M receptor mRNA was induced in activated monocytes, whereas epithelial cells expressed both mRNAs constitutively. Transgenic mice overexpressing IL-31 developed severe pruritus, alopecia and skin lesions. Furthermore, IL-31 receptor expression was increased in diseased tissues derived from an animal model of airway hypersensitivity. These data indicate that IL-31 may be involved in promoting the dermatitis and epithelial responses that characterize allergic and non-allergic diseases.

Repetitive stimulation of naïve T cells by immature splenic dendritic cells (DC) can result in the differentiation of T-cell lines with regulatory properties. In the present study we identified a population of DC in the mucosae that exhibit the plasmacytoid phenotype, secrete interferon-alpha (IFN-alpha) following stimulation with oligodeoxynucleotides containing certain cytosine-phosphate-guanosine (CpG) motifs and can differentiate naïve T cells into cells that exhibit regulatory properties. Although these DC appear to be present in both spleen and mesenteric lymph nodes (MLN), only CpG-matured DC from the MLN (but not the spleen) were able to differentiate naïve T cells into T regulatory 1-like cells with regulatory properties. The activity of these DC failed to sustain robust T-cell proliferation and thereby enhanced the suppressive efficacy of CD4+ CD25+ T regulatory cells. These DC are the major CD8alpha+ DC population in the Peyer's patches (PP). Given their significant presence in mucosal tissue, we propose that these DC may provide a mechanistic basis for the homeostatic regulation in the gut by eliciting regulatory cell suppressor function and poorly supporting T helper cell proliferation at a site of high antigenic stimulation like the intestine.

CD4+CD25+ regulatory T cells (Tregs) are critical for peripheral tolerance and prevention of autoimmunity. In vitro coculture studies have revealed that increased costimulation breaks Treg-mediated suppression in response to anti-CD3 or antigen. However, it was unclear whether loss of suppression arose from inactivation of Tregs or whether increased stimulation caused Th cells to escape suppression. We have investigated conditions that allow or override Treg-mediated suppression using DO11.10 TCR-transgenic T cells and chicken ovalbumin peptide 323-339-pulsed antigen-presenting cells. Treg suppression of Th proliferation is broken with potent stimulation, using activated spleen cells and high antigen dose, but is intact at low antigen dose. Costimulation with CD80 and CD86 expressed on activated dendritic cells was essential for Th cell escape from suppression at a high antigen dose. Potently stimulated Tregs were functional since they reduced levels of IL-2, IFN-gamma, IL-4 and Th CD25 expression in cocultures. Furthermore, Tregs responding to high antigen dose and activated splenocytes retained the ability to suppress proliferation, but only of Th cells responding to a sub-optimal dose of independent antigen. Together, our results demonstrate that under conditions of strong antigen-specific stimulation, Tregs remain functional, but Th cells escape Treg-mediated suppression.

We immunized mice with antigenic peptide P815E, which is presented by H-2Kd and recognized by tumor-specific CTL raised against P815 tumor cells. This peptide is encoded by the ubiquitously expressed gene MsrA and carries a mutated residue conferring tumor specificity. Unexpectedly, we observed a severe toxicity occurring in the early hours after the third injection, resulting in the death of most mice within 24 h. The toxic syndrome was reminiscent of TNF-induced shock, and the sera of ill mice contained high levels of TNF. Toxicity was prevented by injection of neutralizing anti-TNF Abs, confirming the involvement of TNF. Depletion of CD8+ T cells could also prevent toxicity, and ex vivo experiments confirmed that CD8+ lymphocytes were the major cellular source of TNF in immunized mice. Tetramer analysis of the lymphocytes of immunized mice indicated a massive expansion of P815E-specific T cells, up to >60% of circulating CD8+ lymphocytes. A similar toxicity was observed after massive expansion of specific CD8+ T cells following immunization with another P815 peptide, which is encoded by gene P1A and was injected in a form covalently linked to an immunostimulatory peptide derived from IL-1. We conclude that the toxicity is caused by specific CD8+ lymphocytes, which are extensively amplified by peptide immunization in a QS21-based adjuvant and produce toxic levels of TNF upon further stimulation with the peptide. Our results suggest that immunotherapy trials involving new peptides should be pursued with caution and should include a careful monitoring of the T cell response.

Antigens encoded by MAGE genes are of particular interest for cancer immunotherapy because of their tumoral specificity and because they are shared by many tumors. Antigenic peptide MEVDPIGHLY, which is encoded by MAGE-3 and is known to be presented by human leukocyte antigen (HLA)-B44, is currently being used in therapeutic vaccination trials. We report here that a cytolytic T lymphocyte (CTL) clone, which is restricted by HLA-B*1801, recognizes the same peptide and, importantly, lyzes HLA-B18 tumor cells expressing MAGE-3. These results imply that the use of peptide MEVDPIGHLY can now be extended to HLA-B18 patients. We also provide evidence that, under limiting amounts of protein MAGE-3, HLA B*1801 and B*4403 compete for binding to the peptide.

The mechanisms controlling the balance between tolerance and active immunity in mucosal tissues are critical, but not well understood. Specifically, the normal healthy gut exhibits tolerance both to beneficial antigens derived from food and to innocuous antigens derived from commensal flora, but will mount active and protective immune responses against detrimental and damaging antigens from invading gut pathogens. When such immune control mechanisms go awry, the consequences can be devastating. Loss of tolerance to food antigens can manifest as food allergies, such as coeliac disease, that may afflict about 1 in every 300 persons in several countries in the Western World. Likewise, loss of tolerance to commensal flora may manifest as inflammatory bowel disease.

We have analyzed the hierarchy of epitope-specific T cell populations during a primary and a secondary CD8 T cell response. MHC-peptide tetramers were used to track the in vivo kinetics of expansion of T cell populations specific for two Kd-restricted epitopes simultaneously presented by a murine tumor cell following primary or recall immunizations. Individual syngeneic mice generated remarkably different primary CTL responses, as reflected by up to 60-fold differences in the relative contribution of each peptide-specific T cell population to the overall response. In these primary immunizations, the CTL dominance was not dictated by the respective abundance of the presented epitopes. In sharp contrast, the secondary response was systematically associated with a selective expansion of the same epitope-specific population both in vitro and in vivo. In vitro experiments indicated that the extent of expansion of each epitope-specific memory population is modulated by the epitope density. We conclude that, at least for this set of epitopes, the CTL hierarchy is not controlled by the same parameters in a primary vs a secondary response.

A number of human tumor antigens have been characterized recently using cytolytic T lymphocytes (CTL) as screening tools. Some of them are encoded by MAGE-type genes, which are silent in normal tissues except in male germ cells, but are activated in a variety of tumors. These tumor-specific shared antigens appear to be promising targets for cancer immunotherapy. However, the choice of these antigens as targets has been questioned because of the lack of direct evidence that in vivo responses against such antigens can lead to tumor rejection. The antigen encoded by the mouse gene P1A represents the only available animal model system for MAGE-type tumor antigens. We show here that mice immunized by injection of L1210 leukemia cells expressing P1A and B7-1 (L1210.P1A.B7-1) are efficiently protected against a challenge with a lethal dose of mastocytoma P815 tumor cells, which express P1A. Mice immunized with L1210 cells expressing B7-1 but not P1A were not protected. Furthermore, we observed that P1A-transgenic mice, which are tolerant to P1A, were not protected after immunization with L1210.P1A.B7-1. These results demonstrate that the immune response to P1A is the major component of the tumor rejection response observed in normal mice, and support the use of tumor-specific shared antigens as targets for the immunotherapy of human cancer.

Recent work has suggested that important B- and T-cell epitopes on the circumsporozoite protein (CSP) of Plasmodium vivax lie external to the major repeat regions of the protein. We have studied two naturally exposed human populations (Caucasian and Papua New Guineans) and determined the antibody response to yeast-derived recombinant CSPs, overlapping synthetic peptides spanning amino acids 76 348 of the Belem P. vivax CSP and overlapping peptides representing the variant repeats of the VK247 strain of P. vivax. We have demonstrated that the P. vivax CSP-specific antibody response is directed towards areas within the repeat region as well as areas external to this; but the dominant epitopes recognized by the two populations studied, were distinct. One epitope, lying external to the repeats and recognized by both populations, partially overlaps an area of the protein referred to as region II-plus. Sera from malaria-exposed Papua New Guineans and Thais contained antibodies to this epitope (V22, single letter amino acid sequence TCGVGVRVRRRVNAANKKPE) which were capable of recognizing sporozoites, as determined by quantitative inhibition IFA. Seventeen percent of PNG sera had antibodies to this peptide compared with 33% who had antibodies to the central repeats of the protein. Immunization of mice with recombinant CSP did not induce antibodies to V22. However, immunization with overlapping peptide epitopes representing this region (V21 or V22) induced specific antibodies but only two sera recognized both V21 and V22 and, by inference, the overlapping peptide sequence (TCGVGVRVRR). Antibodies in these two sera could bind recombinant CSP in ELISA; however, in contrast, nine sera which recognized either V21 or V22 alone did not bind CSP. Only one of two sera containing antibodies recognizing CSP stained P. vivax sporozoites. This serum also recognized an epitope dependent upon two amino acids aminoterminal to V22. These data suggest that the fine specificity of antibodies is a critical determinant for binding to both recCSP and sporozoites.

Successful therapeutics for inflammatory bowel disease (IBD) must be able to reverse effectively the complex processes involved in the manifestation of inflammatory pathology in intact tissues. Although studies of human tissue samples are important to confirm the biological rationale for developing a particular therapeutic, in vivo rodent models of IBD provide a biological 'flask' in which therapeutics can be tested in a more representative setting. Moreover, gene targeting and transgenic technologies in rodents have exponentially increased the repertoire of available IBD models and provided insight into possible contributions that certain genes may have in the pathogenesis of disease. These models have been key in generating the current arsenal of biological therapeutics that are available, or are presently under investigation, for the treatment of IBD patients.

Members of the CD28 family play important roles in regulating T cell functions and share a common gene structure profile. We have identified VSTM3 as a protein whose gene structure matches that of the other CD28 family members. This protein (also known as TIGIT and WUCAM) has been previously shown to affect immune responses and is expressed on NK cells, activated and memory T cells, and regulatory T cells. The nectin-family proteins CD155 and CD112 serve as counter-structures for VSTM3 and CD155 and CD112 also bind to the activating receptor CD226 on T cells and NK cells. Hence, this group of interacting proteins forms a network of molecules similar to the well-characterized CD28-CTLA4-CD80-CD86 network. In the same way that soluble CTLA4 can be used to block T cell responses, we show that soluble Vstm3 attenuates T cell responses in vitro and in vivo. Moreover, animals deficient in Vstm3 are more sensitive to autoimmune challenges indicating that this new member of the CD28 family is an important regulator of T cell responses.

IL-31 signals through the heterodimeric receptor IL-31RA and oncostatin M receptor (OSMR), and has been linked with the development of atopic dermatitis, a Th2 cytokine-associated disease in humans. However, recent studies of IL-31RA knockout (KO) mice have suggested that IL-31 signaling may be required to negatively regulate Th2 type responses rather than exacerbate them. Because those studies were performed on genetically modified mice, we examined whether neutralizing IL-31 with a specific mAb would give similar results to IL-31RA KO mice in two Th2 cytokine-associated immune models. We report no difference in lymphocyte Th2-type cytokine production after Ag immunization between IL-31RA KO mice, mice treated with the IL-31 mAb, or control animals. Second, we tested whether the absence of the IL-31RA subunit in IL-31RA KO mice may allow for increased pairing of the OSMR subunit with another cytokine receptor, gp130, resulting in overrepresentation of the heterodimeric receptor for OSM and increased responsiveness to OSM protein. We found that intranasal OSM challenge of IL-31RA KO mice resulted in increased IL-6 and vascular endothelial growth factor production in the lung compared with wild-type littermate control animals. Moreover, PBS-challenged IL-31RA KO mice already had increased levels of vascular endothelial growth factor, which were further increased by OSM challenge. These data imply that IL-31RA–deficient mice produce increased levels of OSM-inducible cytokines during airway sensitization and challenge, which may be the driving force behind the apparent exacerbation of Th2-type inflammatory responses previously observed in these mice.

Background IL-31 is a newly discovered T-cell cytokine that, when overexpressed in mice, results in pruritus and skin dermatitis resembling human atopic dermatitis (AD). Objective We sought to investigate the expression of IL-31 and IL-31 receptor A (IL-31RA) in skin biopsy specimens and peripheral blood cells from patients with AD and healthy individuals. Methods Expression of IL-31 and IL-31RA was evaluated in skin biopsy specimens from patients with AD and healthy individuals by means of immunohistochemistry and RT-PCR. IL-31 protein production by skin-homing cutaneous lymphocyte antigen (CLA)–positive T cells was also assessed. Results IL-31RA protein was expressed by keratinocytes and infiltrating macrophages in skin biopsy specimens from patients with AD. Comparisons between skin from patients with AD and healthy skin showed IL-31RA expression at higher levels on epidermal keratinocytes in AD samples. Infiltrating cells, more numerous in skin from patients with AD compared with that of healthy individuals, expressed IL31 mRNA. Histomorphometric analysis of these cells indicated they were of the lymphocytic lineage, with the majority of cells staining positive for CLA and CD3. IL31 mRNA and protein expression is largely restricted to CD45RO + (memory) CLA + T cells in peripheral blood of patients with AD and healthy volunteers. Moreover, circulating CLA + T cells from patients with AD, but not from patients with psoriasis, are capable of producing higher levels of IL-31 compared with CLA + T cells from healthy individuals. However, the average levels of IL-31 were not significantly different between patients with AD and healthy individuals. Conclusion We provide evidence that IL-31 expression is associated with CLA + T cells and might contribute to the development of AD-induced skin inflammation and pruritus.

There are many types of colitis models in animals that researchers use to elucidate the mechanism of action of human inflammatory bowel disease (IBD). These models are also used to test novel therapeutics and therapeutic treatment regimens. Here, we will review the characteristics of the mdr1a -/- model of spontaneous colitis that we believe make this model an important part of the IBD researcher's toolbox. We will also share new data that will reinforce the fact that this model is relevant in the study of IBD. Mdr1a -/- mice lack the murine multiple drug resistance gene for P-glycoprotein 170 that is normally expressed in multiple tissues including intestinal epithelial cells. These mice spontaneously develop a form of colitis at around 12 wk of age. The fact that the complexity of this model mirrors the complexity of disease in humans, as well as recent literature that links MDR1 polymorphisms in humans to Crohn's Disease and Ulcerative Colitis, makes this an appropriate animal model to study.

Despite the apparent positive recognition of antigen by mucosal T cells after ingesting food, the default functional response in the gut is tolerance. Although dendritic cells (DCs) are classically defined as potent stimulatory antigen-presenting cells, we have previously shown that tolerance is enhanced in vivo in the presence of elevated numbers of DCs. In order to more closely investigate the mechanistic basis of tolerance induction, we have focused our subsequent studies on identifying features peculiar to mucosal dendritic cells and the functional involvement of mucosal DCs in driving the early T cell response to fed antigen. These studies have revealed a population of DCs in the mucosae that exhibit the plasmacytoid phenotype and secrete IFN-alpha following stimulation with CpG, and can drive differentiation of naive T cells into cells that exhibit regulatory properties. The activity of these DCs also failed to sustain robust T cell proliferation and, rather, functioned to enhance the suppressive efficacy of CD4(+)CD25(+) T regulatory cells. Given their significant presence in mucosal tissue, these DCs likely provide a mechanistic basis for the homeostatic regulation prominent in the gut, presumably by eliciting regulatory cell suppressor function and poorly supporting T helper cell proliferation. These studies further underscore the critical role for intestinal DCs in promoting tolerogenic antigen presentation at a site of high antigenic stimulation.

The mucosal immune system is uniquely equipped to discriminate between potentially invasive pathogens and innocuous food proteins. While the mechanisms responsible for induction of mucosal immunity vs tolerance are not yet fully delineated, recent studies have highlighted mucosal dendritic cells (DC) as being important in determining the fate of orally administered Ag. To further investigate the DC:T cell signals involved in regulating the homeostatic balance between mucosal immunity and tolerance, we have examined the expression and function of the TNFR family member receptor activator of NF-κB (RANK) and its cognate ligand, RANKL, in vitro and in vivo. Our data show that although DC isolated from mucosal lymphoid tissues expressed similar levels of surface RANK compared with DC isolated from peripheral lymphoid tissues, DC from the distinct anatomical sites displayed differential responsiveness to RANK engagement with soluble RANKL. Whereas splenic DC responded to RANKL stimulation with elevated IL-12 p40 mRNA expression, Peyer’s patch DC instead preferentially displayed increased IL-10 mRNA expression. Our data also show that the in vivo functional capacity of mucosal DC can be modulated by RANKL. Treatment with RANKL in vivo at the time of oral administration of soluble OVA enhanced the induction of tolerance in two different mouse models. These studies underscore the functional differences between mucosal and peripheral DC and highlight a novel role for RANK/RANKL interactions during the induction of mucosal immune responses.

Murine mastocytoma P815 induces CTL responses against at least four distinct Ags (AB, C, D, and E). Recent studies have shown that the main component of the CTL response against the P815 tumor is targeted against Ags P815AB and P815E. The gene P1A has been well characterized. It encodes the P815AB Ag in the form of a nonameric peptide containing two epitopes, P815A and P815B, which are recognized by different CTLs. Here, we report the identification of the P815E Ag. Using a cDNA library derived from tumor P815, we identified the gene coding for P815E. We also characterized the antigenic peptide that anti-P815E CTLs recognize on the MHC class I molecule H-2Kd. The P815E Ag results from a mutation within an ubiquitously expressed gene encoding methionine sulfoxide reductase, an enzyme that is believed to be important in the protection of proteins against the by-products of aerobic metabolism. Surprisingly, immunizing mice i.p. with syngeneic tumor cells (L1210) that were constructed to express B7-1 and P815E did not induce resistance against live P815, even though a strong anti-P815E CTL response was observed with splenocytes from immunized animals.

Summary Prior to any exposure to malaria, most adults have T cells specific for malaria parasites and various malaria proteins. The protein for which this has been shown more than any other is the circumsporozoite protein (CSP) of Plasmo-dium falciparum. These T cells can be present in high frequency and appear to have arisen through exposure to other (non-malaria) organisms. Although T cells are thought to provide protection against sporozoites, these T cells specific for cross-reactive organisms are clearly unable to protect against malaria, and may be preferentially expanded following exposure to malaria sporozoites. Thus, cross-reactive organisms have the potential to skew the repertoire of sporozoite-induced T cells and affect the induction of protective immunity. This is analogous to the concept of ‘original antigenic sin’ whereby prior exposure to one strain of influenza virus was shown to be able to divert the antibody response to a second challenging strain to focus on the shared (cross-reactive) epitopes.

IL-21 plays a role in many autoimmune and inflammatory diseases, including psoriasis and inflammatory bowel disease (IBD). To investigate IL-21 antagonism in disease, we evaluated a neutralizing anti-mouse IL-21 mAb in a CD4+CD25- T cell transfer SCID mouse model of psoriasis and colitis. Mice treated prophylactically with IL-21 mAb had significant reductions in colitis and psoriatic-like skin symptoms compared to mice treated with PBS or isotype control mAb. IL-21 mAb-treated mice had 5-7-fold lower average lesional skin scores, 6-7-fold lower average clinical colitis scores and significant reductions in histological indices of colitis compared to controls. Mice treated with IL-21 mAb also had significantly lower serum IL-6, RANTES, TNF-α, and MIP-1β levels compared to controls, further supporting an anti-inflammatory role for IL-21 mAb. In a delayed dosing study, mice treated with IL-21 mAb starting 12 days after T cell transfer had significant reductions in colitis, with 3.5-4-fold lower average colitis scores than control-treated mice. Dose-related reductions in lesional skin scores were also observed. Efficacy of IL-21 mAb was equivalent to or better than an anti-mouse IL-12/23p40 active control mAb. These results demonstrate that IL-21 mAb reduces psoriasis-like disease and colitis in a murine model and suggest that an anti-human IL-21 mAb may have clinical utility in treatment of psoriasis and IBD.