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Abstract Background DEVELOP is a multi-center, global, prospective, observational, longitudinal registry of long-term safety of infliximab (and other treatments) in paediatric patients (pts) with inflammatory bowel disease (IBD) <18 years (yrs) at diagnosis. Over the course of follow-up, many pts required changes in therapy. Ustekinumab (UST) is approved for treatment of Crohn’s disease (CD) in adults and is currently being evaluated for safety/efficacy in paediatric pts. This report focuses on assessment of safety of UST in paediatric pts with CD from DEVELOP. Methods Data included paediatric pts treated with UST from 31 May 2007 through 30 June 2022; data are collected every 6 months. The analyzed population included: all paediatric pts (all pts), pts weighing <40kg (<40kg group), and pts weighing ≥40kg (≥40kg group). Assessments included medical and treatment history, UST exposure, adverse events (AEs), serious AEs (SAEs), CD-related SAEs leading to hospitalization, IBD surgeries, serious and opportunistic infections, malignancies, and deaths. Results A total of 150 pts received UST (49.3% females); 31 in the <40kg group and 119 in the ≥40kg group (Table 1). Most treated pts (92.0%) were 12-17yrs. The majority (91%) of pts were initially dosed with UST every 8 weeks (q8w); at the last known dose, 64% received UST q8w and 22% q4w. Mean (SD) age of initial UST exposure was 15yrs (2.19). Prior IBD surgery was reported in 65.3% pts. The majority of pts (98%) had prior biologic therapy and 72% received ≥2 biologics prior to UST. Overall, 37/150 (24.7%) of pts discontinued UST during follow-up, with a mean (SD) time to discontinuation of 16.7 (17.00) months; 84/150 (56.0%) were exposed to UST for ≥24 months. Rates (events/100 pt-yrs) of AEs were higher in the ≥40kg group (177.62) than in the <40kg group (101.27). Rates of SAEs were slightly lower among the ≥40kg group (25.42) vs <40kg (32.67). There were no SAEs related to infusion or injection site reactions. Rates of serious infections and CD-related hospitalizations were low and similar between groups, and rates of IBD-related surgeries were similar between groups (Figure 1). One malignancy (malignant carcinoid tumor) was reported in a female (18yrs) in the ≥40kg group with a history of prior therapy with vedolizumab, methotrexate, and 6-MP. No deaths or opportunistic infections were reported. Conclusion The safety profile observed for this off-label use of UST in paediatric CD pts in DEVELOP was similar to that of the treated adult population, despite most paediatric pts having prior biologic exposure. No new safety signals are identified in this paediatric population.

Abstract Background Perianal fistulas and abscesses occur commonly as complications of pediatric Crohn’s disease (CD). A validated imaging assessment tool for quantification of perianal disease severity and activity is needed to evaluate treatment response. We aimed to identify magnetic resonance imaging (MRI)-based measures of perianal fistulizing disease activity and study design features appropriate for pediatric patients. Methods Seventy-nine statements relevant to MRI-based assessment of pediatric perianal fistulizing CD activity and clinical trial design were generated from literature review and expert opinion. Statement appropriateness was rated by a panel (N = 15) of gastroenterologists, radiologists, and surgeons using modified RAND/University of California Los Angeles appropriateness methodology. Results The modified Van Assche Index (mVAI) and the Magnetic Resonance Novel Index for Fistula Imaging in CD (MAGNIFI-CD) were considered appropriate instruments for use in pediatric perianal fistulizing disease clinical trials. Although there was concern regarding the use of intravascular contrast material in pediatric patients, its use in clinical trials was considered appropriate. A clinically evident fistula tract and radiologic disease defined as at least 1 fistula or abscess on pelvic MRI were considered appropriate trial inclusion criteria. A coprimary clinical and radiologic end point and inclusion of a patient-reported outcome were also considered appropriate. Conclusion Outcomes of treatment of perianal fistulizing disease in children must include MRI. Existing multi-item measures, specifically the mVAI and MAGNIFI-CD, can be adapted and used for children. Further research to assess the operating properties of the indices when used in a pediatric patient population is ongoing.

Abstract DRB1*0401 has been associated with predisposition to rheumatoid arthritis while DRB1*0402 is associated with resistance. We have generated transgenic mice lacking endogenous H2-A and E molecules (AEo) but expressing DRB1*0401 or DRB1*0402 molecules. All transgenic mice expressed functional DR molecules which could positively and negatively select various Vβ T cell repertoire profile. Transgenic mice were studied in vivo for induction of arthritis following immunization with type II collagen. DRB1*0401 mice are susceptible to collagen-induced arthritis while DRB1*0402 mice are resistant. Presence of DR4 leads to arthritis predominantly in female mice. CIA susceptible AEo.DQ8 mice have been shown to develop arthritis without a gender bias. However, AEo mice expressing DRB1*0401.DQ8 develop arthritis in female mice with a ratio of 3F:1M, similar to that in humans. DRB1*0402 mice did not show any defect in humoral response though they demonstrated a lower cellular response to CII and an increased activation-induced cell death compared to susceptible mice. In vitro T cell response with superantigen staphylococcal enterotoxin B and Concovalin A showed that DRB1*0402 mice are not defective in generating T cell response. The resistant mice showed an increased cell death in thymus suggesting deletion of autoreactive T cells at thymic level might be one reason for protection. The data suggest that DRB1 polymorphism lead to selection of TCR in thymus thus controlling the selection of autoreactive T cells available in periphery. Thus these transgenic mice may be useful to study the reasons for gender-bias observed in human patients develop therapeutic strategies.

Abstract We have generated transgenic (tg) mice expressing HLA-DQ8αβ (DQA1*0301/DQB*0302) or HLA-DQ6αβ (DQA1*0103/DQB1*0601) molecules lacking endogenous murine class II expression (Aβ0) to investigate the ability of these HLA class II to present type II collagen (CII) and induce collagen-induced arthritis. The DQ8αβ tg mice responded strongly to CII, developing severe arthritis, while DQ6αβ tg mice were nonresponsive to CII. The addition of the mixed haplotype DQ8α6β molecule did not significantly influence CII reactivity. To examine the interaction of DQ6αβ and DQ8αβ molecules in vivo, we generated double tg DQ6αβ/8αβ (Aβ0) mice expressing both the α- and β-chains of DQ6 and DQ8 molecules by mating DQ6αβ (Aβ0) and DQ8αβ (Aβ0) tg mice. CII-immunized DQ6αβ/8αβ tg mice developed severe experimental polychondritis, exhibiting both polyarthritis and auricular chondritis. The clinical, serologic, and histologic manifestations of experimental polychondritis are similar to those symptoms in human relapsing polychondritis. The susceptibility of DQ6αβ/8αβ tg mice compared with resistance in the parental strains suggests that expression of both the DQ6αβ and DQ8αβ tgs, unique to the DQ6αβ8αβ tg strain, is important in susceptibility to experimental polychondritis. The DQ6αβ/8αβ tg mice provide a model to investigate putative autoantigens and the mechanisms of pathogenesis involved in relapsing polychondritis as well as the influence of the expression of multiple HLA class II molecules on the disease process.

Abstract A series of 101 peptides each 20 amino acids in length (10-residue overlap) spanning the helical portion of the mature α-chain of human type II collagen (CII) was synthesized. DBA/1 (H-2q) mice were immunized with individual peptides, and draining lymph node cells were challenged in vitro. Strong responses were measured to three peptides: peptide I (residues 74-93), peptide 14 (residues 254-273), and peptide 81 (residues 924-943). B10.Q (H-2q) mice were responsive to peptides I and 81 but not to peptide 14. B10.RIII (H-2r) mice, which are resistant to arthritis induction following immunization with human CII, were unresponsive to peptides I, 14, and 81. Using single amino acid truncated peptides, we determined minimal immunostimulatory lengths for peptides I and 81. Residues critical to antigenicity were identified by introducing alanine and glycine substitutions into minimal length immunostimulatory peptides. The determinants within peptides I and 81 are 100% homologous to mouse CII and are autoantigens. Peptide 81 has homology to viral proteins. Peptide 14 is 90% homologous to mouse CII and has homology to heat shock proteins.

Abstract Human type II collagen (HuCII) may be one of the autoantigens involved in human rheumatoid arthritis (RA). By using over-lapping peptides, we have previously described an immunodominant region (HuCII.250-270) on HuCII. In the present study, this 21-mer HuCII.250-270 peptide was used as tolerogen, and its effect on both early and effector phase of collagen-induced arthritis (CIA) was examined. Upon immunization with HuCII-derived peptide 250-270, HuCII.250-270-tolerized mice showed diminished T cell proliferation that was mediated by Th1 cytokine, IL-2. More interestingly, oral tolerance with HuCII.250-270 peptide diminishes primarily a Th1 type of immune response. Arthritis severity was reduced markedly in mice orally tolerized with HuCII.250-270 peptide both at early and effector phases. Suppression of CIA at the effector phase by oral administration of HuCII peptide suggests a potential immunotherapeutic use of collagen II peptide in the treatment of human RA.

Abstract B10.Ek alpha transgenic mice were mated with H2-E B10.Q and SWR mice. F1 and F1 x parental strain backcross progeny were tested for arthritis and autoimmune reactivity to mouse type II collagen (MII) after immunization with bovine, chick, deer, or human type II collagen. The results were correlated with the H-2 haplotype (b/q vs q/q) and the TCR V beta profile of peripheral blood T cells in each mouse. Hybrid progeny expressed TCR profiles different from either parent because of the TCR V beta genomic deletions of SWR mice (V beta a), the wild-type TCR allele of C57Bl/10 (B10) mice (V beta b), and the intrathymic negative selection processes resulting from cell surface expression of Ek alpha-A q beta or Eb beta-Ek alpha, together with the integrated retroviral genes Mtv-9 originating in B10 mice and Mtv-7 (Mls-1a) from SWR mice. (B10.Ek alpha x SWR)F1 mice developed higher IgG anti-MII Ab titers, but much milder arthritis than (B10.E x B10.Q)F1 mice. Expression of Ek alpha did not change the level of IgG anti-MII Ab nor the degree of susceptibility to collagen-induced arthritis (CIA) in the H-2q/q and H-2b/q progeny of (B10.Ek alpha x B10.Q)F1 x B10.Q matings, indicating that the Mtv-9-reactive, TCR V beta 5+, and V beta 11+ T cells are not critical to CIA. Among bovine type II collagen-immunized (B10.Ek alpha x SWR)F1 x SWR backcross mice: 1) arthritis severity is associated with the presence of V beta b (p < or = 0.01) and expression of Ek alpha (p < or = 0.05), but not with the MHC haplotype (b/q vs q/q); 2) regression analysis showed a significant association (R = 0.99) between IgG anti-MII Ab titers and the level of Mtv-7-reactive V beta 6+ T cells that was detectable in the IgG1, but not the IgG2a subclass. The data prompt the speculation that Mtv-7-reactive V beta 6+ (or V beta 7+) T cells in (B10.EK alpha x SWR)F1 x SWR mice express Th2-type properties, and thus contribute to the combination of mild arthritis but high anti-MII Ab titers that characterize mice of SWR heritage.

Abstract Type II collagen from six mammalian species was investigated for the capacity to induce an immune response and collagen-induced arthritis (CIA) in C57/B10 congenic mouse strains. H-2q haplotype mice were susceptible to chick, bovine, deer, rat, and human type II collagen, but were resistant to arthritis induced by porcine type II collagen. H-2r haplotype mice only developed CIA in response to bovine, deer, and porcine collagen. High antibody responses in the absence of disease, directed against a specific type II collagen, were observed in many independent haplotypes. The cross-reactive capacity of different antisera to the various collagen species was studied. The data support the existence of two arthritogenic and multiple nonarthritogenic epitopes on the type II collagen molecule.

Background:Research on the utilization and effectiveness of antitumor necrosis factor (TNF) biologics in children with very early onset inflammatory bowel disease (VEOIBD) is urgently needed. Here we describe anti‐TNF use and durability in a multicenter cohort.Methods:We performed a retrospective cohort study of patients diagnosed with VEOIBD (<6 years) between 2008 and 2013 at 25 North American centers. We performed chart abstraction at diagnosis and 1, 3, and 5 years after diagnosis. We examined the rate of initiation and durability of infliximab and adalimumab and evaluated associations between treatment durability and the following covariates with multivariate Cox proportional hazard regression: age at diagnosis, sex, disease duration, disease classification, and presence of combined immunomodulatory treatment versus monotherapy.Results:Of 294 children with VEOIBD, 120 initiated treatment with anti‐TNF therapy and 101 had follow‐up data recorded [50% Crohn disease (CD), 31% ulcerative colitis (UC), and 19% IBD unclassified (IBD‐U)]. The cumulative probability of anti‐TNF treatment was 15% at 1 year, 30% at 3 years, and 45% at 5 years from diagnosis; 56 (55%) were treated between 0 and 6 years old. Anti‐TNF durability was 90% at 1 year, 75% at 3 years, and 55% at 5 years. The most common reason for discontinuation of anti‐TNF were loss of response in 24 (57%) children. Children with UC/IBD‐U had lower durability than those with CD (hazard ratio [HR] 0.17; 95% confidence interval [CI], 0.06–0.51; P = 0.001).Conclusions:Utilization and durability of anti‐TNF in VEOIBD is relatively high and comparable with older children. Having Crohn disease (compared with UC/IBD‐U) is associated with greater durability.

Abstract Background and Aims Ileal strictures are the major indication for resective surgery in Crohn’s disease [CD]. We aimed to define ileal gene programmes present at diagnosis and linked with future stricturing behaviour during 5-year follow-up, and to identify potential small molecules to reverse these gene signatures. Methods Antimicrobial serologies and pre-treatment ileal gene expression were assessed in a representative subset of 249 CD patients within the RISK multicentre paediatric CD inception cohort study, including 113 that are unique to this report. These data were used to define genes associated with stricturing behaviour and for model testing to predict stricturing behaviour. A bioinformatics approach to define small molecules which may reverse the stricturing gene signature was applied. Results A total of 19 of the 249 patients developed isolated B2 stricturing behaviour during follow-up, while 218 remained B1 inflammatory. Using deeper RNA sequencing than in our previous report, we have now defined an inflammatory gene signature including an oncostatin M co-expression signature, tightly associated with extra-cellular matrix [ECM] gene expression, in those who developed stricturing complications. We further computationally prioritise small molecules targeting macrophage and fibroblast activation and angiogenesis which may reverse the stricturing gene signature. A model containing ASCA and CBir1 serologies and a refined eight ECM gene set was significantly associated with stricturing development by Year 5 after diagnosis {AUC (area under the curve) (95th CI [confidence interval]) = 0.82 [0.7–0.94)}. Conclusions An ileal gene programme for macrophage and fibroblast activation is linked to stricturing complications in treatment of naïve pediatric CD, and may inform novel small molecule therapeutic approaches.