Optimization of Human Mesenchymal Stem Cells for Rheumatoid Arthritis: Implications for Improved Therapeutic Outcomes.

OBJECTIVE: Seropositive rheumatoid arthritis (RA) is a chronic autoimmune disease that is rarely "cured." Human mesenchymal stem cells (hMSCs) are known to reduce inflammation and restore immune homeostasis. However, methods for predicting therapeutic hMSC potency have not been established. The goal of these studies was to use and refine an ex vivo functional assay that determines potency of hMSCs and can then be validated in clinical trials as a potency measure of hMSCs used therapeutically to treat RA. METHODS: Allogeneic hMSCs were cytokine-stimulated, and a conditioned medium (CM) was harvested. The CM was tested for the potential to attenuate RA CD4+ T cell proliferation using suppression assays. Indoleamine 2, 3-dioxygenase (IDO) mRNA, and protein were quantified in hMSCs as a measure to compare hMSCs across (prior) studies. RESULTS: To mimic a proinflammatory environment that resembles that in RA, interleukin-1(IL1ß), tumor necrosis factor α (TNFα), and interferon γ (IFNγ) (alone or in combination) were used to precondition hMSCs. Treating hMSCs with a combination of these cytokines generated a CM "secretome" that suppressed T cell proliferation between 70 and 83%. Forty-eight hours of cytokine preconditioning hMSCs was required to maximize this effect. T cell suppression positively correlated with increases in hMSC cellular IDO mRNA and protein. CONCLUSION: By standardizing assays to measure hMSC effects, their potency on T cell suppression can be quantified. These studies demonstrate that hMSCs can be compared functionally to identify optimal preparation(s) for therapeutic use in RA and that the potency of hMSC-dependent T cell suppression may differ between hMSC donors. Clinical studies are warranted to validate the hypothesis that ex vivo potency in suppressing T cells will positively correlate with a reduction in RA disease activity and increase in immunological quiescence.

CDCP1 on Dendritic Cells Contributes to the Development of a Model of Kawasaki Disease.

The etiology and pathology of Kawasaki disease (KD) remain elusive. Cub domain-containing protein 1 (CDCP1), a cell-surface protein that confers poor prognosis of patients with certain solid tumors, was recently identified as one of the most significantly upregulated genes in SARS-CoV-2-infected children who developed systemic vasculitis, a hallmark of KD. However, a potential role of CDCP1 in KD has not previously been explored. In this study, we found that CDCP1 knockout (KO) mice exhibited attenuated coronary and aortic vasculitis and decreased serum Candida albicans water-soluble fraction (CAWS)-specific IgM/IgG2a and IL-6 concentrations compared with wild-type mice in an established model of KD induced by CAWS administration. CDCP1 expression was not detectable in cardiomyocytes, cardio fibroblasts, or coronary endothelium, but constitutive expression of CDCP1 was observed on dendritic cells (DCs) and was upregulated by CAWS stimulation. CAWS-induced IL-6 production was significantly reduced in CDCP1 KO DCs, in association with impaired Syk-MAPK signaling pathway activation. These novel findings suggest that CDCP1 might regulate KD development by modulating IL-6 production from DCs via the Syk-MAPK signaling pathway.

CD6 is a target for cancer immunotherapy.

Limitations of checkpoint inhibitor cancer immunotherapy include induction of autoimmune syndromes and resistance of many cancers. Since CD318, a novel CD6 ligand, is associated with the aggressiveness and metastatic potential of human cancers, we tested the effect of an anti-CD6 monoclonal antibody, UMCD6, on killing of cancer cells by human lymphocytes. UMCD6 augmented killing of breast, lung, and prostate cancer cells through direct effects on both CD8+ T cells and NK cells, increasing cancer cell death and lowering cancer cell survival in vitro more robustly than monoclonal antibody checkpoint inhibitors that interrupt the programmed cell death 1 (PD-1)/PD-1 ligand 1 (PD-L1) axis. UMCD6 also augmented in vivo killing by human peripheral blood lymphocytes of a human breast cancer line xenotransplanted into immunodeficient mice. Mechanistically, UMCD6 upregulated the expression of the activating receptor NKG2D and downregulated expression of the inhibitory receptor NKG2A on both NK cells and CD8+ T cells, with concurrent increases in perforin and granzyme B production. The combined capability of an anti-CD6 monoclonal antibody to control autoimmunity through effects on CD4+ lymphocyte differentiation while enhancing killing of cancer cells through distinct effects on CD8+ and NK cells opens a potential new approach to cancer immunotherapy that would suppress rather than instigate autoimmunity.

CD318 is a ligand for CD6.

It has been proposed that CD6, an important regulator of T cells, functions by interacting with its currently identified ligand, CD166, but studies performed during the treatment of autoimmune conditions suggest that the CD6-CD166 interaction might not account for important functions of CD6 in autoimmune diseases. The antigen recognized by mAb 3A11 has been proposed as a new CD6 ligand distinct from CD166, yet the identity of it is hitherto unknown. We have identified this CD6 ligand as CD318, a cell surface protein previously found to be present on various epithelial cells and many tumor cells. We found that, like CD6 knockout (KO) mice, CD318 KO mice are also protected in experimental autoimmune encephalomyelitis. In humans, we found that CD318 is highly expressed in synovial tissues and participates in CD6-dependent adhesion of T cells to synovial fibroblasts. In addition, soluble CD318 is chemoattractive to T cells and levels of soluble CD318 are selectively and significantly elevated in the synovial fluid from patients with rheumatoid arthritis and juvenile inflammatory arthritis. These results establish CD318 as a ligand of CD6 and a potential target for the diagnosis and treatment of autoimmune diseases such as multiple sclerosis and inflammatory arthritis.

Development of a Novel Renal Activity Index of Lupus Nephritis in Children and Young Adults.

OBJECTIVE: Noninvasive estimation of the degree of inflammation seen on kidney biopsy with lupus nephritis (LN) remains difficult. The objective of this study was to develop a Renal Activity Index for Lupus (RAIL) that, based solely on laboratory measures, accurately reflects histologic LN activity. METHODS: We assayed traditional LN laboratory tests and 16 urine biomarkers (UBMs) in children (n = 47) at the time of kidney biopsy. Histologic LN activity was measured by the National Institutes of Health activity index (NIH-AI) and the tubulointerstitial activity index (TIAI). High LN-activity status (versus moderate/low) was defined as NIH-AI scores >10 (versus ≤10) or TIAI scores >5 (versus ≤5). RAIL algorithms that predicted LN-activity status for both NIH-AI and TIAI were derived by stepwise multivariate logistic regression, considering traditional biomarkers and UBMs as candidate components. The accuracy of the RAIL for discriminating by LN-activity status was determined. RESULTS: The differential excretion of 6 UBMs (neutrophil gelatinase-associated lipocalin, monocyte chemotactic protein 1, ceruloplasmin, adiponectin, hemopexin, and kidney injury molecule 1) standardized by urine creatinine was considered in the RAIL. These UBMs predicted LN-activity (NIH-AI) status with >92% accuracy and LN-activity (TIAI) status with >80% accuracy. RAIL accuracy was minimally influenced by concomitant LN damage. Accuracies between 71% and 85% were achieved without standardization of the UBMs. The strength of these UBMs to reflect LN-activity status was confirmed by principal component and linear discriminant analyses. CONCLUSION: The RAIL is a robust and highly accurate noninvasive measure of LN activity. The measurement properties of the RAIL, which reflect the degree of inflammatory changes as seen on kidney biopsy, will require independent validation.

Tocilizumab in pediatric rheumatology: the clinical experience.

During the last two decades, clinical use of novel biological therapy has led to increased mechanistic understanding of complex rheumatological diseases. Conversely, basic and translational studies have led to development of new and varied therapeutic agents. These new medications which "target" specific steps in one or more immune pathways have the potential to control disease symptoms, improve quality of life and long-term prognosis, and perhaps in some, restore immunological tolerance. Use of these agents in clinical trials, combined with post-marketing surveillance, has revealed both the benefits and the undesirable side-effects of biological disease-modifying anti-rheumatic drugs (DMARDs). In this review we focus on the use of tocilizumab, a monoclonal antibody directed against the IL6 receptor (IL6R), which potently inhibits IL-6/IL6R signaling.

Anti-glomerular basement membrane antibody disease treated with rituximab: A case-based review.

OBJECTIVES: To report the successful use of rituximab in a patient with anti- glomerular basement membrane (GBM) antibody disease and to review the literature regarding rituximab use in anti-GBM mediated disease. METHODS: We report a case of anti-GBM antibody disease with both anti-GBM antibodies and anti-myeloperoxidase (MPO) specific p-ANCA, who developed thrombotic thrombocytopenic purpura (TTP) on high dose prednisone, plasmapheresis, and cyclophosphamide therapy. The patient was then treated with rituximab. We analyzed the clinical features of five additional patients of anti-GBM disease treated with rituximab identified through a systematic literature review. RESULTS: Our patient was 68-year-old female who presented with acute renal failure. Renal biopsy showed crescentic glomerulonephritis with linear deposits of IgG antibody along the glomerular basement membrane. Treatment was initiated with high dose prednisone, plasmapheresis and oral cyclophosphamide, with subsequent development of leukopenia and TTP and discontinuance of cyclophosphamide. Treatment with rituximab was initiated with clinical improvement of her hematological parameters but not her renal function. Among the five previously reported cases of anti-GBM disease treated with rituximab, three received brief course of IV cyclophosphamide prior to use of rituximab. Except one patient, all recovered renal function and remained dialysis independent. The anti-GBM antibody level remained undetected in all patients. CONCLUSIONS: Combination of prednisone, plasmapheresis, and rituximab can be an effective therapy in patients with an anti-GBM antibody disease complicated with TTP.

Do adult disease severity subclassifications predict use of cyclophosphamide in children with ANCA-associated vasculitis? An analysis of ARChiVe study treatment decisions.

OBJECTIVE: To determine whether adult disease severity subclassification systems for antineutrophil cytoplasmic antibody-associated vasculitis (AAV) are concordant with the decision to treat pediatric patients with cyclophosphamide (CYC). METHODS: We applied the European Vasculitis Study (EUVAS) and Wegener's Granulomatosis Etanercept Trial (WGET) disease severity subclassification systems to pediatric patients with AAV in A Registry for Childhood Vasculitis (ARChiVe). Modifications were made to the EUVAS and WGET systems to enable their application to this cohort of children. Treatment was categorized into 2 groups, "cyclophosphamide" and "no cyclophosphamide." Pearson's chi-square and Kendall's rank correlation coefficient statistical analyses were used to determine the relationship between disease severity subgroup and treatment at the time of diagnosis. RESULTS: In total, 125 children with AAV were studied. Severity subgroup was associated with treatment group in both the EUVAS (chi-square 45.14, p < 0.001, Kendall's tau-b 0.601, p < 0.001) and WGET (chi-square 59.33, p < 0.001, Kendall's tau-b 0.689, p < 0.001) systems; however, 7 children classified by both systems as having less severe disease received CYC, and 6 children classified as having severe disease by both systems did not receive CYC. CONCLUSION: In this pediatric AAV cohort, the EUVAS and WGET adult severity subclassification systems had strong correlation with physician choice of treatment. However, a proportion of patients received treatment that was not concordant with their assigned severity subclass.

Increased sensitivity of the European medicines agency algorithm for classification of childhood granulomatosis with polyangiitis.

OBJECTIVE: Granulomatosis with polyangiitis (Wegener's; GPA) and other antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are rare in childhood and are sometimes difficult to discriminate. We compared use of adult-derived classification schemes for GPA against validated pediatric criteria in the ARChiVe (A Registry for Childhood Vasculitis e-entry) cohort, a Childhood Arthritis and Rheumatology Research Alliance initiative. METHODS: Time-of-diagnosis data for children with physician (MD) diagnosis of AAV and unclassified vasculitis (UCV) from 33 US/Canadian centers were analyzed. The European Medicines Agency (EMA) classification algorithm and European League Against Rheumatism/Paediatric Rheumatology International Trials Organisation/Paediatric Rheumatology European Society (EULAR/PRINTO/PRES) and American College of Rheumatology (ACR) criteria for GPA were applied to all patients. Sensitivity and specificity were calculated (MD-diagnosis as reference). RESULTS: MD-diagnoses for 155 children were 100 GPA, 25 microscopic polyangiitis (MPA), 6 ANCA-positive pauciimmune glomerulonephritis, 3 Churg-Strauss syndrome, and 21 UCV. Of these, 114 had GPA as defined by EMA, 98 by EULAR/PRINTO/PRES, and 87 by ACR. Fourteen patients were identified as GPA by EULAR/PRINTO/PRES but not by ACR; 3 were identified as GPA by ACR but not EULAR/PRINTO/PRES. Using the EMA algorithm, 135 (87%) children were classifiable. The sensitivity of the EMA algorithm, the EULAR/PRINTO/PRES, and ACR criteria for classifying GPA was 90%, 77%, and 69%, respectively, with specificities of 56%, 62%, and 67%. The relatively poor sensitivity of the 2 criteria related to their inability to discriminate patients with MPA. CONCLUSION: EULAR/PRINTO/PRES was more sensitive than ACR criteria in classifying pediatric GPA. Neither classification system has criteria for MPA; therefore usefulness in discriminating patients in ARChiVe was limited. Even when using the most sensitive EMA algorithm, many children remained unclassified.

Mesenchymal stem cells: mechanisms of inflammation.

In adults, human mesenchymal stem cells (hMSCs) are found in vivo at low frequency and are defined by their capacity to differentiate into bone, cartilage, and adipose tissue, depending on the stimuli and culture conditions under which they are expanded. Although MSCs were initially hypothesized to be the panacea for regenerating tissues, MSCs appear to be more important in therapeutics to regulate the immune response invoked in settings such as tissue injury, transplantation, and autoimmunity. MSCs have been used therapeutically in clinical trials and subsequently in practice to treat graft-versus-host disease following bone marrow transplantation. Reports of successful immune modulation suggest efficacy in a wide range of autoimmune conditions, such as demyelinating neurological disease (multiple sclerosis), systemic lupus erythematosus, and Crohn's disease, among others. This review provides background information about hMSCs and also describes their putative mechanisms of action in inflammation. We provide a summary of ongoing clinical trials to allow (a) full comprehension of the range of diseases in which hMSC therapy may be beneficial and (b) identification of gaps in our knowledge about the mechanisms of action of therapeutic MSCs in disease.

Classification, presentation, and initial treatment of Wegener's granulomatosis in childhood.

OBJECTIVE: To compare the criteria for Wegener's granulomatosis (WG) of the American College of Rheumatology (ACR) with those of the European League Against Rheumatism/Pediatric Rheumatology European Society (EULAR/PRES) in a cohort of children with WG and other antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs), and to describe the interval to diagnosis, presenting features, and initial treatment for WG. METHODS: Eligible patients had been diagnosed by site rheumatologists (termed the "MD diagnosis") since 2004. This diagnosis was used as a reference standard for sensitivity and specificity testing of the 2 WG classification criteria. Descriptive analyses were confined to ACR-classified WG patients. RESULTS: MD diagnoses of 117 patients (82 of whom were female) were WG (n = 76), microscopic polyangiitis (n = 17), ANCA-positive pauci-immune glomerulonephritis (n = 5), Churg-Strauss syndrome (n = 2), and unclassified vasculitis (n = 17). The sensitivities of the ACR and EULAR/PRES classification criteria for WG among the spectrum of AAVs were 68.4% and 73.6%, respectively, and the specificities were 68.3% and 73.2%, respectively. Two more children were identified as having WG by the EULAR/PRES criteria than by the ACR criteria. For the 65 ACR-classified WG patients, the median age at diagnosis was 14.2 years (range 4-17 years), and the median interval from symptom onset to diagnosis was 2.7 months (range 0-49 months). The most frequent presenting features by organ system were constitutional (89.2%), pulmonary (80.0%), ear, nose, and throat (80.0%), and renal (75.4%). Fifty-four patients (83.1%) commenced treatment with the combination of corticosteroids and cyclophosphamide, with widely varying regimens; the remainder received methotrexate alone (n = 1), corticosteroids alone (n = 4), or a combination (n = 6). CONCLUSION: The EULAR/PRES criteria minimally improved diagnostic sensitivity and specificity for WG among a narrow spectrum of children with AAVs. Diagnostic delays may result from poor characterization of childhood WG. Initial therapy varied considerably among participating centers.

Neutrophil gelatinase-associated lipocalin is a predictor of the course of global and renal childhood-onset systemic lupus erythematosus disease activity.

OBJECTIVE: To determine whether neutrophil gelatinase-associated lipocalin (NGAL) can predict worsening of global and renal disease activity in childhood-onset systemic lupus erythematosus (SLE). METHODS: One hundred eleven patients with childhood-onset SLE were enrolled in a longitudinal, prospective study with quarterly study visits and had at least 3 study visits. At each visit, global disease activity was measured using 3 external standards: the numerically converted British Isles Lupus Assessment Group (BILAG) index, the SLE Disease Activity Index 2000 update score, and the physician's assessment of global disease activity. Renal and extrarenal disease activity were measured by the respective domain scores. The disease course over time was categorized at the most recent visit (persistently active, persistently inactive, improved, or worsening). Plasma and urinary NGAL levels were measured by enzyme-linked immunosorbent assay, and urinary NGAL levels were standardized to the urinary creatinine concentration. The longitudinal changes in NGAL levels were compared with the changes in SLE disease activity using mixed-effect models. RESULTS: Significant increases in standardized urinary NGAL levels of up to 104% were detected up to 3 months before worsening of lupus nephritis (as measured by all 3 external standards). Plasma NGAL levels increased significantly by as much as 26% up to 3 months before worsening of global SLE disease activity as measured by all 3 external standards. Plasma NGAL levels increased significantly by 26% as early as 3 months prior to worsening of lupus nephritis as measured by the BILAG renal score. CONCLUSION: Serial measurement of urinary and plasma NGAL levels may be valuable in predicting impending worsening of global and renal childhood-onset SLE disease activity.

Neutrophil gelatinase-associated lipocalin as a biomarker of disease activity in pediatric lupus nephritis.

We hypothesized that neutrophil gelatinase-associated lipocalin (NGAL) is an early predictive biomarker of disease activity in lupus nephritis. NGAL in serial plasma (PNGAL) and urine (UNGAL) samples was measured by enzyme-linked immunosorbent assay (ELISA) in 85 participants with pediatric systemic lupus erythematosus (pSLE), healthy children (n = 50), and children with juvenile idiopathic arthritis (JIA) (n = 30). Disease activity was measured by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Plasma and urinary NGAL were significantly increased in subjects with pSLE compared with those with JIA or with healthy controls (all p < 0.03), and unrelated to subjects' age, weight, or height. Plasma and urinary NGAL were stable in pSLE subjects with unchanged disease activity. The pSLE subjects with worsening global or renal disease activity had a mean +/- standard error (SE) increase of UNGAL (in ng/ml) of 11.5 +/- 6.4 or 36.6 +/- 12.1 (p < 0.01), corresponding to a 156% or 380% increase, respectively. PNGAL increased with worsening disease but to a much lesser degree than UNGAL [global disease activity (mean +/- SE): 7.3 +/- 6.2 or 21%; renal disease activity: 20.2 +/- 6.0 or 51%; both p = not significant]. In conclusion, NGAL in urine but not in plasma represents a novel biomarker for renal disease activity in pSLE.

CD166 expression, characterization, and localization in salivary epithelium: implications for function during sialoadenitis.

CD166 is an Ig superfamily molecule that binds homotypically to itself and heterotypically to CD6. Interactions between CD6 and CD166 are important during immune development and in alloreactivity. CD166 is expressed at increased levels in selected cancers and in rheumatoid arthritis synovium. Knowledge that CD166 was expressed in normal human salivary epithelium led to these studies of CD166 and CD6 in diseased mouse salivary glands, that resemble pathology seen in the human disease, Sjögren's syndrome. We showed that in mouse salivary epithelium CD166 was expressed but that expression of CD166 did not necessarily predict its function. Recombinant soluble CD6-Ig bound to CD6 ligands (CD6L) on transformed and freshly isolated salivary epithelial cells. Cross-blocking studies showed that binding of CD6-Ig to salivary epithelium was in part dependent on CD166, but that CD6-Ig binding may also involve additional CD6L. Binding of CD6-Ig was sensitive to trypsin digestion but resistant to digestion by collagenase and sialidase. Anti-CD166 ab precipitated CD166 from salivary epithelium pre- and post-treatment with the pro-inflammatory cytokine IFN-gamma. In contrast CD6-Ig only precipitated CD166 from IFN-gamma treated cells. More extensive colocalization between CD166 and the actin cytoskeleton was observed in sialoadenitis epithelium compared to control. We conclude that during sialoadenitis, CD166 undergoes a gain of function, resulting in closer association with the actin cytoskeleton and increased capacity to bind CD6. We suggest that altered CD166 function may contribute to the pro-inflammatory milieu during sialoadenitis seen in Sjögren's syndrome.

Expression and characterization of a novel CD6 ligand in cells derived from joint and epithelial tissues.

CD6 is a T cell surface glycoprotein that plays an important role in interactions of thymocytes with thymic epithelial cells and in mature T cell interactions with selected nonprofessional tissue APCs. We describe a novel CD6 ligand (CD6L) 3A11 Ag that is distinct from the known CD6L (CD166). The 3A11 protein is expressed on cells derived from human thymus, skin, synovium, and cartilage, and its expression is enhanced by IFN-gamma. mAbs directed against the 3A11 Ag and CD166 exhibit distinct patterns of binding to a panel of cell lines. Confocal microscopy shows that both CD166 and the 3A11 Ag are expressed at the cell surface, and that these proteins colocalize. The 3A11 Ag has a molecular mass of 130 kDa and is immunoprecipitated using either mAb 3A11 or soluble CD6-Ig fusion protein. mAbs directed against individual CD6L were less potent than was soluble CD6-Ig fusion protein in reducing adhesion of T cells to adherent 3A11-positive epithelial cells in vitro, suggesting that these Abs recognize epitopes on the 3A11 Ag and CD166 that are distinct from CD6 binding sites. Finally, transfection of epithelial cells with CD166-specific small interfering RNAs significantly decreased CD166 expression without alteration in 3A11 Ag levels, and thus confirmed that these two CD6L are distinct. Taken together, our data identifies a novel 130-kDa CD6L that may mediate interactions of synovial and epithelial cells with T lymphocytes.

Remittive agents in pediatric rheumatology.

PURPOSE OF REVIEW: Children with rheumatic diseases frequently require therapy with disease-modifying antirheumatic drugs and/or biologic agents. Therapies that have been prospectively tested in adults are often used in children before full evaluation of their safety and efficacy. Published experience that may report "off-label" usage can be helpful in decision making, although such reports do not reduce the need for prospective clinical trials in children. The purpose of this review is to summarize the recent published evidence regarding efficacy (and safety, when available) of standard and novel agents used in pediatric rheumatic disease. RECENT FINDINGS: Etanercept, one of three currently available tumor necrosis factor-alpha inhibitors has a juvenile idiopathic arthritis indication. Novel "off-label" uses in children for interleukin-1 receptor agonist (Anakinra), antiinterleukin-6 receptor antibody (MRA), and rituximab (anti-CD20 monoclonal antibody) are discussed. SUMMARY: This review summarizes the published evidence that supports the use of selected disease-modifying antirheumatic drugs and novel biologic agents in children with rheumatic diseases.