Integrating circulating T follicular memory cells and autoantibody repertoires for characterization of autoimmune disorders.

Introduction: Autoimmune diseases are heterogeneous and often lack specific or sensitive diagnostic tests. Increased percentages of CD4+CXCR5+PD1+ circulating T follicular helper (cTfh) cells and skewed distributions of cTfh subtypes have been associated with autoimmunity. However, cTfh cell percentages can normalize with immunomodulatory treatment despite persistent disease activity, indicating the need for identifying additional cellular and/or serologic features correlating with autoimmunity. Methods: The cohort included 50 controls and 56 patients with autoimmune cytopenias, gastrointestinal, pulmonary, and/or neurologic autoimmune disease. Flow cytometry was used to measure CD4+CXCR5+ T cell subsets expressing the chemokine receptors CXCR3 and/or CCR6: CXCR3+CCR6- Type 1, CXCR3-CCR6- Type 2, CXCR3+CCR6+ Type 1/17, and CXCR3- CCR6+ Type 17 T cells. IgG and IgA autoantibodies were quantified using a microarray featuring 1616 full-length, conformationally intact protein antigens. The 97.5th percentile in the control cohort defined normal limits for T cell subset percentages and total number (burden) of autoantibodies. Results: This study focused on CD4+CXCR5+ T cells because CXCR5 upregulation occurs after cognate T-B cell interactions characteristic of autoimmune diseases. We refer to these cells as circulating T follicular memory (cTfm) cells to acknowledge the dynamic nature of antigen-experienced CXCR5+ T cells, which encompass progenitors of cTfh or Tfh cells as well as early effector memory T cells that have not yet lost CXCR5. Compared to controls, 57.1% of patients had increased CXCR5+CXCR3+CCR6+ cTfm1/17 and 25% had increased CXCR5+CXCR3-CCR6+ cTfm17 cell percentages. Patients had significantly more diverse IgG and IgA autoantibodies than controls and 44.6% had an increased burden of autoantibodies of either isotype. Unsupervised autoantibody clustering identified three clusters of patients with IgG autoantibody profiles distinct from those of controls, enriched for patients with active autoimmunity and monogenic diseases. An increased percentage of cTfm17 cells was most closely associated with an increased burden of high-titer IgG and IgA autoantibodies. A composite measure integrating increased cTfm1/17, cTfm17, and high-titer IgG and/or IgA autoantibodies had 91.1% sensitivity and 90.9% specificity for identifying patients with autoimmunity. Percentages of cTfm1/17 and cTfm17 percentages and numbers of high-titer autoantibodies in patients receiving immunomodulatory treatment did not differ from those in untreated patients, thus suggesting that measurements of cTfm can complement measurements of other cellular markers affected by treatment. Conclusions: This study highlights two new approaches for assessing autoimmunity: measuring CD4+CXCR5+ cTfm subsets as well as total burden of autoantibodies. Our findings suggest that these approaches are particularly relevant to patients with rare autoimmune disorders for whom target antigens and prognosis are often unknown.

A homozygous stop-gain variant in ARHGAP42 is associated with childhood interstitial lung disease, systemic hypertension, and immunological findings.

ARHGAP42 encodes Rho GTPase activating protein 42 that belongs to a member of the GTPase Regulator Associated with Focal Adhesion Kinase (GRAF) family. ARHGAP42 is involved in blood pressure control by regulating vascular tone. Despite these findings, disorders of human variants in the coding part of ARHGAP42 have not been reported. Here, we describe an 8-year-old girl with childhood interstitial lung disease (chILD), systemic hypertension, and immunological findings who carries a homozygous stop-gain variant (c.469G>T, p.(Glu157Ter)) in the ARHGAP42 gene. The family history is notable for both parents with hypertension. Histopathological examination of the proband lung biopsy showed increased mural smooth muscle in small airways and alveolar septa, and concentric medial hypertrophy in pulmonary arteries. ARHGAP42 stop-gain variant in the proband leads to exon 5 skipping, and reduced ARHGAP42 levels, which was associated with enhanced RhoA and Cdc42 expression. This is the first report linking a homozygous stop-gain variant in ARHGAP42 with a chILD disorder, systemic hypertension, and immunological findings in human patient. Evidence of smooth muscle hypertrophy on lung biopsy and an increase in RhoA/ROCK signaling in patient cells suggests the potential mechanistic link between ARHGAP42 deficiency and the development of chILD disorder.

Acetaminophen Inhibits the Neutrophil Oxidative Burst: Implications for Diagnostic Testing.

BACKGROUND: Chronic granulomatous disease is a primary immunodeficiency characterized by recurrent bacterial and fungal infections, granuloma formation, and inflammatory disease. Impaired neutrophil oxidative function is an essential diagnostic criterion. In vitro exposure of neutrophils to acetaminophen, a commonly used over-the-counter medication, has been associated with reduced neutrophil oxidative function. The clinical implications of acetaminophen intake for dihydrorhodamine (DHR) testing remain unknown. OBJECTIVE: To evaluate the effect of in vivo administration of therapeutic doses of acetaminophen on DHR diagnostic testing. METHODS: We performed DHR testing in 15 healthy adults before and after administering a single dose of acetaminophen. We retrospectively reviewed 195 DHR test results from hospitalized patients who had received acetaminophen, nonsteroidal anti-inflammatory drug, or corticosteroid before testing. RESULTS: DHR testing result was abnormal in 100% (n = 15) of healthy adults 2 hours after acetaminophen intake. We identified 195 instances of DHR testing less than or equal to 72 hours after acetaminophen ingestion in hospitalized patients who did not have chronic granulomatous disease. DHR results were abnormal in 43 of 195 cases (22.1%). Frequency of false-positive testing was increased in patients who received acetaminophen within 24 hours of testing, and in patients who received more than 1 dose of acetaminophen. Nonsteroidal anti-inflammatory drug and corticosteroid intakes were not associated with abnormal DHR result. CONCLUSIONS: Patients treated with acetaminophen have decreased neutrophil oxidative burst as measured by DHR testing. To avoid falsely abnormal testing for chronic granulomatous disease, patients should be advised to avoid acetaminophen for at least 24 hours before DHR testing.

An emerging role for endothelial barrier support therapy for congenital disorders of glycosylation.

Congenital disorders of glycosylation (CDGs) are clinically heterogeneous disorders defined by a decreased ability to modify biomolecules with oligosaccharides. Critical disruptions in protein recognition, interaction, binding, and anchoring lead to broad physiological effects. Patients present with endocrinopathy, immunodeficiency, hepatopathy, coagulopathy, and neurodevelopmental impairment. Patients may experience mortality/morbidity associated with shock physiology that is frequently culture negative and poorly responsive to standard care. Oedema, pleural and pericardial effusions, ascites, proteinuria, and protein-losing enteropathy are observed with an exaggerated inflammatory response. The negative serum protein steady state results from several mechanisms including reduced hepatic synthesis and secretion, increased consumption, and extravasation. Disruption of the glycocalyx, a layer of glycosylated proteins that lines the endothelium preventing thrombosis and extravasation, is a suspected cause of endothelial dysfunction in CDG patients. We performed a retrospective review of CDG patients admitted to our institution with acute illness over the past 2 years. Longitudinal clinical and laboratory data collected during the sick and well states were assessed for biomarkers of inflammation and efficacy of interventions. Six patients representing 4 CDG subtypes and 14 hospitalisations were identified. Acute D-dimer elevation, proteinuria, decreased serum total protein levels, coagulation proteins, and albumin were observed with acute illness. Infusion of fresh frozen plasma, and in some cases protein C concentrate, was associated with clinical and biomarker improvement. This was notable with intra-patient comparison of treated vs untreated courses. Use of endothelial barrier support therapy may reduce endothelial permeability by restoring both regulatory serum protein homeostasis and supporting the glycocalyx and is likely a critical component of care for this population.

Long-Term Outcome of Peanut Oral Immunotherapy Facilitated Initially by Omalizumab.

BACKGROUND: We successfully used omalizumab to facilitate peanut oral immunotherapy (OIT) in children with reactivity to ≤50mg peanut protein and with high peanut IgE (median, 229 kU/L). OBJECTIVE: We report on long-term OIT outcomes in these patients, including dosing changes, adverse events, peanut immunoglobulin changes, and quality of life (QoL). METHODS: Patients were followed for up to 72 months (67 months of maintenance). Outcomes were collected on peanut dose amount, form, and frequency, as well as adverse events, (QoL), and laboratory studies. RESULTS: Of 13 patients initially enrolled, 7 patients (54%) continued on peanut OIT through month 72; 6 (46%) discontinued therapy because of adverse reactions. Maintenance peanut protein dose varied between 500 and 3500mg. Most patients consumed different peanut-containing products. All patients experienced at least 1 adverse event, and 1 patient developed eosinophilic esophagitis. Peanut-IgE, Arah1-IgE and Arah2-IgE, peanut-SPT, peanut-IgE:IgE ratio, and Arah2-IgE:Arah2-IgG4 ratio decreased on OIT. Peanut-IgG4, Arah1-IgG4, and Arah2-IgG4 initially increased on OIT and then decreased, though not falling to baseline levels. In patients who stopped OIT, there was a trend for reversal of these biomarker changes. Higher peanut-IgE and Arah2-IgE at study month 12 were associated with discontinuation. Patient and parent QoL improved from baseline, even in patients who discontinued OIT. CONCLUSIONS: Although adjunctive omalizumab allowed for faster and successful desensitization in patients with high peanut-IgE, almost half of patients discontinued OIT within 72 months because of reactions. Patients who stopped therapy had higher month 12 peanut-IgE and Arah2-IgE. It is possible that these patients might benefit from longer omalizumab administration.

Acquired Cold-Induced Urticaria in Pediatric Patients: A 22-Year Experience in a Tertiary Care Center (1996-2017).

BACKGROUND: Acquired cold-induced urticaria (ACU) has not been well evaluated in pediatrics. OBJECTIVE: To further evaluate the presentation of ACU in children and associated risk of anaphylaxis. METHODS: A retrospective chart review was performed in children 18 years or younger diagnosed with ACU at Boston Children's Hospital (US, Northeast) from 1996 to 2017. RESULTS: A total of 415 patients with ACU were identified, aged 4 months to 18.3 years at the time of diagnosis, with similar male:female distribution. Most patients had a history of atopic disease (78.3%), and 25.8% had other urticaria. Around two-third of patients experienced only localized cold-induced symptoms (grade 1), whereas 14.0% had diffuse cutaneous symptoms (grade 2) as the most severe reaction, and 18.6% experienced anaphylaxis (grade 3). Swimming triggered 77.6% of grade 3 reactions, whereas the rest were secondary to ingestion of cold food or beverages, or cold air or cold water exposure. Seven percent of subjects had more than 1 episode of anaphylaxis. Cold stimulation test (CST) was performed in 61.7% of patients, and the result was positive in 69.9% of those tested. Positive CST result was significantly associated with increased risk of anaphylaxis. There was a 11.7% rate of anaphylaxis among patients with negative CST result. Disease resolution at any point in the study period was documented in 8.9% of patients and was associated with a negative history of anaphylaxis. CONCLUSIONS: In the largest study to date on ACU, grade 3 reactions occurred in about a fifth of patients. Positive CST result was associated with a higher risk for anaphylaxis from ACU. Epinephrine prescription and patient/family counseling about risk factors for grade 3 reactions are recommended.

The Heterogeneity of Oral Immunotherapy Clinical Trials: Implications and Future Directions.

Food allergy is a potentially life-threatening disease which affects up to 8% of children and 2-3% of adults. Increasing food allergy prevalence poses a major public health concern. Induction of desensitization to food allergens through oral immunotherapy (OIT) is an expanding area of study encompassing peanut, egg, milk, and other food allergens. OIT consists of administering incremental doses of food allergen to food-allergic patients, to induce a state of desensitization. Safety, tolerability, and efficacy all remain ongoing concerns. Clinical trials for oral immunotherapy have encompassed many variations, including differences in dosage sizes and frequency, duration of build-up, type of allergen used, patient characteristics, and adjuvant therapies. Consequently, studies have also shown variation in rates of adverse effects, and successful desensitization. Here, we provide an overview of the key studies and discuss the implications of this heterogeneity. While desensitization is successful in the majority of patients, only a minority appear to develop sustained unresponsiveness even after years of therapy. Much larger and longitudinal studies using more homogenous protocols are needed in order to evaluate the clinical applicability of OIT, its long-term effectiveness, and effect on quality of life. The role of adjunctive therapies, including omalizumab and probiotics, requires further evaluation.

Leucine-rich repeat containing 8A (LRRC8A) is essential for T lymphocyte development and function.

Lrrc8a is a ubiquitously expressed gene that encodes a leucine-rich repeat (LRR)-containing protein detected at higher levels on the surface of thymocytes than on other immune cells. We generated Lrrc8a(-/-) mice to investigate the role of LRRC8A in lymphocyte development and function. Lrrc8a(-/-) mice had increased prenatal and postnatal mortality, growth retardation, and multiple tissue abnormalities. Lrrc8a(-/-) mice displayed a modest block in B cell development but intact intrinsic B cell function. In contrast, both Lrrc8a(-/-) mice and Lrrc8a(-/-)→Rag2(-/-) bone marrow chimeras exhibited a severe cell-intrinsic block in early thymic development, with decreased proliferation and increased apoptosis of thymocytes, and impaired peripheral T cell function. Thymic epithelial cells expressed an LRRC8A ligand that was critical for double-negative to double-positive thymocyte differentiation and survival in vitro. LRRC8A constitutively associated with the GRB2-GAB2 complex and lymphocyte-specific protein tyrosine kinase (LCK) in thymocytes. LRRC8A ligation activated AKT via the LCK-ZAP-70-GAB2-PI3K pathway, and AKT phosphorylation was markedly reduced in the thymus of Lrrc8a(-/-) mice. These findings reveal an essential role for LRRC8A in T cell development, survival, and function.

Disruption of MHC class II-restricted antigen presentation by vaccinia virus.

Vaccinia virus (VV), currently used in humans as a live vaccine for smallpox, can interfere with host immunity via several discrete mechanisms. In this study, the effect of VV on MHC class II-mediated Ag presentation was investigated. Following VV infection, the ability of professional and nonprofessional APC to present Ag and peptides to CD4+ T cells was impaired. Viral inhibition of class II Ag presentation could be detected within 1 h, with diminished T cell responses dependent upon the duration of APC infection and virus titer. Exposure of APC to replication-deficient virus also diminished class II Ag presentation. Virus infection of APC perturbed Ag presentation by newly synthesized and recycling class II molecules, with disruptions in both exogenous and cytoplasmic Ag presentation. Virus-driven expression of an endogenous Ag, failed to restore T cell responsiveness specific for this Ag in the context of MHC class II molecules. Yet, both class II protein steady-state and cell surface expression were not altered by VV. Biochemical and functional analysis revealed that VV infection directly interfered with ligand binding to class II molecules. Together, these observations suggest that disruption of MHC class II-mediated Ag presentation may be one of multiple strategies VV has evolved to escape host immune surveillance.

Enhanced production of IL-10 by dendritic cells deficient in CIITA.

Dendritic cells (DC) are professional APCs that play a critical role in regulating immunity. In DC, maturation-induced changes in MHC class II expression and Ag presentation require transcriptional regulation by CIITA. To study the role of CIITA in DC, we evaluated key cell functions in DC from CIITA-deficient (CIITA(-/-)) mice. The ability to take up Ag, measured by fluid phase endocytosis, was comparable between CIITA(-/-) and control DC. Although CIITA(-/-) DC lack MHC class II, they maintained normal expression of costimulatory molecules CD80, CD86, and CD40. In contrast, CIITA(-/-) DC activated with LPS or CpG expressed increased IL-10 levels, but normal levels of TNF-alpha and IL-12 relative to control. Enhanced IL-10 was due to greater IL-10 mRNA in CIITA(-/-) DC. Abeta(-/-) DC, which lack MHC class II but express CIITA normally, had exhibited no difference in IL-10 compared with control. When CIITA was cotransfected with an IL-10 promoter-reporter into a mouse monocyte cell line, RAW 264.7, IL-10 promoter activity was decreased. In addition, reintroducing CIITA into CIITA(-/-) DC reduced production of IL-10. In all, these data suggest that CIITA negatively regulates expression of IL-10, and that CIITA may direct DC function in ways that extend beyond control of MHC class II.

Cathepsin E: a novel target for regulation by class II transactivator.

The aspartic proteinase cathepsin E (CatE) has been implicated in Ag processing. In this study we report that CatE expression is negatively regulated by the MHC class II transactivator (CIITA). CIITA-deficient murine and human B cells expressed greater CatE than wild-type B cells, whereas overexpression of CIITA in a human gastric carcinoma cell line, AGS, resulted in decreased CatE mRNA and protein. AGS cells expressing CIITA also exhibited decreased processing of OVA Ag. Inhibition of CatE expression is specific to the type III CIITA isoform and maps to the acidic and proline/serine/threonine-rich (PST) protein domains of CIITA. We found that CatE expression is inducible by PU.1 and p300, and that this induction can be reversed by CIITA. These findings demonstrate a novel phenomenon: regulation of CatE Ag processing by CIITA in an isoform-dependent manner.