Regulatory T Cell-Derived TGF-ß1 Controls Multiple Checkpoints Governing Allergy and Autoimmunity.

The mechanisms by which regulatory T (Treg) cells differentially control allergic and autoimmune responses remain unclear. We show that Treg cells in food allergy (FA) had decreased expression of transforming growth factor beta 1 (TGF-ß1) because of interleukin-4 (IL-4)- and signal transducer and activator of transciription-6 (STAT6)-dependent inhibition of Tgfb1 transcription. These changes were modeled by Treg cell-specific Tgfb1 monoallelic inactivation, which induced allergic dysregulation by impairing microbiota-dependent retinoic acid receptor-related orphan receptor gamma t (ROR-γt)+ Treg cell differentiation. This dysregulation was rescued by treatment with Clostridiales species, which upregulated Tgfb1 expression in Treg cells. Biallelic deficiency precipitated fatal autoimmunity with intense autoantibody production and dysregulated T follicular helper and B cell responses. These results identify a privileged role of Treg cell-derived TGF-ß1 in regulating allergy and autoimmunity at distinct checkpoints in a Tgfb1 gene dose- and microbiota-dependent manner.

Regulatory T cell reprogramming toward a Th2-cell-like lineage impairs oral tolerance and promotes food allergy.

Oral immunotherapy has had limited success in establishing tolerance in food allergy, reflecting failure to elicit an effective regulatory T (Treg) cell response. We show that disease-susceptible (Il4ra(F709)) mice with enhanced interleukin-4 receptor (IL-4R) signaling exhibited STAT6-dependent impaired generation and function of mucosal allergen-specific Treg cells. This failure was associated with the acquisition by Treg cells of a T helper 2 (Th2)-cell-like phenotype, also found in peripheral-blood allergen-specific Treg cells of food-allergic children. Selective augmentation of IL-4R signaling in Treg cells induced their reprogramming into Th2-like cells and disease susceptibility, whereas Treg-cell-lineage-specific deletion of Il4 and Il13 was protective. IL-4R signaling impaired the capacity of Treg cells to suppress mast cell activation and expansion, which in turn drove Th2 cell reprogramming of Treg cells. Interruption of Th2 cell reprogramming of Treg cells might thus provide candidate therapeutic strategies in food allergy.

The microbial origins of food allergy.

Food allergy (FA) is a significant public health issue, propelled by its rapidly increasing prevalence. Its sharp rise into prominence has focused attention on causative environmental factors and their interplay with the immune system in disease pathogenesis. In that regard, there is now substantial evidence that alterations in the gut microbiome early in life imprint the host gut mucosal immunity and may play a critical role in precipitating FA. These changes may impact key steps in the development of the infant gut microbiome, including its shaping by maternal factors and upon the introduction of solid food (the weaning reaction). These early-life changes may have long-range effects on host immunity that manifest later in time as disease pathology. Experimental studies have shown that resetting the host intestinal immune responses by treatment with either a healthy fecal microbiota transplantation or defined commensal bacterial taxa can prevent or treat FA. The mechanisms by which these interventions suppress FA include restoration of gut immune regulatory checkpoints, notably the retinoic orphan receptor gamma T+ regulatory T cells, the epithelial barrier, and healthy immunoglobulin A responses to the gut commensals. These findings inform human studies currently in progress that evaluate the role of microbial therapies in FA.

AR101 Oral Immunotherapy for Peanut Allergy.

BACKGROUND: Peanut allergy, for which there are no approved treatment options, affects patients who are at risk for unpredictable and occasionally life-threatening allergic reactions. METHODS: In a phase 3 trial, we screened participants 4 to 55 years of age with peanut allergy for allergic dose-limiting symptoms at a challenge dose of 100 mg or less of peanut protein (approximately one third of a peanut kernel) in a double-blind, placebo-controlled food challenge. Participants with an allergic response were randomly assigned, in a 3:1 ratio, to receive AR101 (a peanut-derived investigational biologic oral immunotherapy drug) or placebo in an escalating-dose program. Participants who completed the regimen (i.e., received 300 mg per day of the maintenance regimen for approximately 24 weeks) underwent a double-blind, placebo-controlled food challenge at trial exit. The primary efficacy end point was the proportion of participants 4 to 17 years of age who could ingest a challenge dose of 600 mg or more, without dose-limiting symptoms. RESULTS: Of the 551 participants who received AR101 or placebo, 496 were 4 to 17 years of age; of these, 250 of 372 participants (67.2%) who received active treatment, as compared with 5 of 124 participants (4.0%) who received placebo, were able to ingest a dose of 600 mg or more of peanut protein, without dose-limiting symptoms, at the exit food challenge (difference, 63.2 percentage points; 95% confidence interval, 53.0 to 73.3; P<0.001). During the exit food challenge, the maximum severity of symptoms was moderate in 25% of the participants in the active-drug group and 59% of those in the placebo group and severe in 5% and 11%, respectively. Adverse events during the intervention period affected more than 95% of the participants 4 to 17 years of age. A total of 34.7% of the participants in the active-drug group had mild events, as compared with 50.0% of those in the placebo group; 59.7% and 44.4% of the participants, respectively, had events that were graded as moderate, and 4.3% and 0.8%, respectively, had events that were graded as severe. Efficacy was not shown in the participants 18 years of age or older. CONCLUSIONS: In this phase 3 trial of oral immunotherapy in children and adolescents who were highly allergic to peanut, treatment with AR101 resulted in higher doses of peanut protein that could be ingested without dose-limiting symptoms and in lower symptom severity during peanut exposure at the exit food challenge than placebo. (Funded by Aimmune Therapeutics; PALISADE ClinicalTrials.gov number, NCT02635776 .).

Untargeted metabolomic profiling identifies disease-specific signatures in food allergy and asthma.

BACKGROUND: Food allergy (FA) affects an increasing proportion of children for reasons that remain obscure. Novel disease biomarkers and curative treatment options are strongly needed. OBJECTIVE: We sought to apply untargeted metabolomic profiling to identify pathogenic mechanisms and candidate disease biomarkers in patients with FA. METHODS: Mass spectrometry-based untargeted metabolomic profiling was performed on serum samples of children with either FA alone, asthma alone, or both FA and asthma, as well as healthy pediatric control subjects. RESULTS: In this pilot study patients with FA exhibited a disease-specific metabolomic signature compared with both control subjects and asthmatic patients. In particular, FA was uniquely associated with a marked decrease in sphingolipid levels, as well as levels of a number of other lipid metabolites, in the face of normal frequencies of circulating natural killer T cells. Specific comparison of patients with FA and asthmatic patients revealed differences in the microbiota-sensitive aromatic amino acid and secondary bile acid metabolism. Children with both FA and asthma exhibited a metabolomic profile that aligned with that of FA alone but not asthma. Among children with FA, the history of severe systemic reactions and the presence of multiple FAs were associated with changes in levels of tryptophan metabolites, eicosanoids, plasmalogens, and fatty acids. CONCLUSIONS: Children with FA have a disease-specific metabolomic profile that is informative of disease mechanisms and severity and that dominates in the presence of asthma. Lower levels of sphingolipids and ceramides and other metabolomic alterations observed in children with FA might reflect the interplay between an altered microbiota and immune cell subsets in the gut.

Defective TLR9-driven STAT3 activation in B cells of patients with CVID.

B cell activation by Toll-like receptor 9 (TLR9) ligands is dependent on STAT3 and is important for optimal antibody responses to microbial antigens. B cells from patients with common variable immune deficiency (CVID) have impaired proliferation and differentiation in response to the TLR9 ligand CpG, despite normal levels of TLR9 expression. We demonstrate that CpG-driven STAT3 phosphorylation, but not activation of NFκB and p38, is selectively impaired in B cells from CVID patients. These results suggest that defective STAT3 activation contributes to the defective TLR9 and antibody response of B cells in CVID.

A twenty-two-year experience with Hymenoptera venom immunotherapy in a US pediatric tertiary care center 1996-2018.

BACKGROUND: The rate of systemic reactions (SRs) to venom immunotherapy (VIT) in children has not been well evaluated. OBJECTIVE: To evaluate the rate of SRs to VIT in pediatric patients age 5 to 18 years who were treated with a standard protocol. METHODS: A retrospective chart review was conducted to identify patients who received VIT at Boston Children's Hospital from 1996 through 2018. Information on venom testing, severity of reaction to insect field sting, and SRs to VIT were retrieved. RESULTS: A total of 78 patients were included. Most had moderate to severe reactions to insect sting before VIT. The rate of SRs was 0.2% of injection visits, occurring in 9% of patients. The SRs from VIT were mild (mostly grade 1 and some grade 2), and no grades 3, 4, or 5 reactions were seen. Male sex was a significant risk factor for moderate to severe reactions to insect sting. Positive testing to vespinae was seen in 98.7% of patients, and none had exclusive sensitivity to honeybee. The severity of the initial, pre-VIT insect sting reactions in our patients did not correlate with the occurrence of SRs from VIT. Twenty-seven percent of the patients were subsequently stung while on VIT. Only 1 patient (5%) had a mild SR, while all others had only local or no reaction at all. CONCLUSION: In the largest US study evaluating the safety of VIT in children, SRs to VIT were mild, and none required epinephrine. Male sex was significantly associated with higher risk of moderate to severe reactions to insect sting. Larger multicenter studies are needed to further evaluate the rate of SRs to VIT in pediatric patients.

Omalizumab facilitates rapid oral desensitization for peanut allergy.

BACKGROUND: Peanut oral immunotherapy is a promising approach to peanut allergy, but reactions are frequent, and some patients cannot be desensitized. The anti-IgE medication omalizumab (Xolair; Genentech, South San Francisco, Calif) might allow more rapid peanut updosing and decrease reactions. OBJECTIVE: We sought to evaluate whether omalizumab facilitated rapid peanut desensitization in highly allergic patients. METHODS: Thirty-seven subjects were randomized to omalizumab (n = 29) or placebo (n = 8). After 12 weeks of treatment, subjects underwent a rapid 1-day desensitization of up to 250 mg of peanut protein, followed by weekly increases up to 2000 mg. Omalizumab was then discontinued, and subjects continued on 2000 mg of peanut protein. Subjects underwent an open challenge to 4000 mg of peanut protein 12 weeks after stopping study drug. If tolerated, subjects continued on 4000 mg of peanut protein daily. RESULTS: The median peanut dose tolerated on the initial desensitization day was 250 mg for omalizumab-treated subjects versus 22.5 mg for placebo-treated subject. Subsequently, 23 (79%) of 29 subjects randomized to omalizumab tolerated 2000 mg of peanut protein 6 weeks after stopping omalizumab versus 1 (12%) of 8 receiving placebo (P < .01). Twenty-three subjects receiving omalizumab versus 1 subject receiving placebo passed the 4000-mg food challenge. Overall reaction rates were not significantly lower in omalizumab-treated versus placebo-treated subjects (odds ratio, 0.57; P = .15), although omalizumab-treated subjects were exposed to much higher peanut doses. CONCLUSION: Omalizumab allows subjects with peanut allergy to be rapidly desensitized over as little as 8 weeks of peanut oral immunotherapy. In the majority of subjects, this desensitization is sustained after omalizumab is discontinued. Additional studies will help clarify which patients would benefit most from this approach.

The role of the gut microbiota in food allergy.

PURPOSE OF REVIEW: The rise in the prevalence of food allergy over the past decades has focused attention of factors that may impact disease development, most notably the gut microbiota. The gut microbial communities play a crucial role in promoting oral tolerance. Their alteration by such factors as Cesarean section delivery, diet and antibiotics may influence disease development. This review highlights recent progress in our understanding of the role of the gut microbiota in the development of food allergy. RECENT FINDINGS: Food allergy is associated with alterations in the gut microbiota or dysbiosis early in life that may be predictive of disease persistence versus tolerance acquisition. Evidence for the benefits of adjunct therapy with probiotics for the prevention of food allergies and for potentiating oral immunotherapy remains circumstantial, with further studies needed to validate its use. Studies in murine models of food allergy suggest that microbial therapy with protolerogenic bacteria such as certain Clostridial species holds promise in future applications for prevention or therapy of food allergy. SUMMARY: Progress in understanding the role of dysbiosis in food allergy and the factors that promote its development, such as antibiotic therapy, diet, modes of infant delivery, and environmental exposures, offer windows of opportunity for both preventive and therapeutic interventions to stem the rising tide of the food allergy epidemic.

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.

TNF receptor superfamily member 13b (TNFRSF13B) hemizygosity reveals transmembrane activator and CAML interactor haploinsufficiency at later stages of B-cell development.

BACKGROUND: Heterozygous C104R or A181E TNF receptor superfamily member 13b (TNFRSF13B) mutations impair removal of autoreactive B cells, weaken B-cell activation, and convey to patients with common variable immune deficiency (CVID) an increased risk for autoimmunity. How mutant transmembrane activator and CAML interactor (TACI) influences wild-type TACI function is unclear; different models suggest either a dominant negative effect or haploinsufficiency. OBJECTIVE: We investigated potential TACI haploinsufficiency by analyzing patients with antibody-deficient Smith-Magenis syndrome (SMS) who possess only 1 TNFRSF13B allele and antibody-deficient patients carrying one c.204insA TNFRSF13B null mutation. METHODS: We tested the reactivity of antibodies isolated from single B cells from patients with SMS and patients with a c.204insA TNFRSF13B mutation and compared them with counterparts from patients with CVID with heterozygous C104R or A181E TNFRSF13B missense mutations. We also assessed whether loss of a TNFRSF13B allele induced haploinsufficiency in naive and memory B cells and recapitulated abnormal immunologic features typical of patients with CVID with heterozygous TNFRSF13B missense mutations. RESULTS: We found that loss of a TNFRSF13B allele does not affect TACI expression, activation responses, or establishment of central B-cell tolerance in naive B cells. Additionally, patients with SMS and those with a c.204insA TNFRSF13B mutation display normal regulatory T-cell function and peripheral B-cell tolerance. The lack of a TNFRSF13B allele did result in decreased TACI expression on memory B cells, resulting in impaired activation and antibody secretion. CONCLUSION: TNFRSF13B hemizygosity does not recapitulate autoimmune features of CVID-associated C104R and A181E TNFRSF13B mutations, which likely encode dominant negative products, but instead reveals selective TACI haploinsufficiency at later stages of B-cell development.

Oral immunotherapy induces IgG antibodies that act through FcγRIIb to suppress IgE-mediated hypersensitivity.

BACKGROUND: Food-induced anaphylaxis is triggered by specific IgE antibodies. Paradoxically, some subjects with significant IgE levels can ingest allergenic foods without incident. Similarly, subjects completing oral immunotherapy (OIT) tolerate food challenges despite persistent high-titer food-specific IgE. OBJECTIVE: We sought to test whether IgG antibodies induced by food immunotherapy prevent food-induced anaphylaxis and whether this occurs through the inhibitory receptor FcγRIIb. METHODS: Food allergy-susceptible Il4raF709 mice were enterally sensitized to ovalbumin (OVA). Similarly sensitized IgE-deficient (IgE(-/-)) Il4raF709 mice, which can ingest OVA without anaphylaxis, were subjected to a high-dose enteral OVA desensitization protocol (OIT). Sera from both groups were tested for the ability to activate or inhibit bone marrow mast cells (BMMCs) exposed to allergen or to passively transfer allergy to naive hosts. In parallel experiments sera obtained from patients with peanut allergy before and after undergoing OIT were interrogated for their ability to enhance or suppress peanut-induced activation in an indirect assay by using basophils from nonallergic donors. RESULTS: Il4raF709 mice exhibited strong OVA-specific IgE responses. Their sera efficiently sensitized BMMCs for activation by antigen challenge. Sera from Il4raF709/IgE(-/-) mice subjected to OVA OIT suppressed BMMC responses. This inhibition was IgG mediated and FcγRIIb dependent. Similarly, pre-OIT but not post-OIT sera from patients efficiently sensitized basophils for peanut-induced activation. IgG antibodies in post-OIT sera suppressed basophil activation by pre-OIT sera. This inhibition was blocked by antibodies against FcγRII. CONCLUSION: Food-specific IgG antibodies, such as those induced during OIT, inhibit IgE-mediated reactions. Strategies that favor IgG responses might prove useful in the management of food allergy.

A pilot study of omalizumab to facilitate rapid oral desensitization in high-risk peanut-allergic patients.

BACKGROUND: Peanut allergy is a major public health problem that affects 1% of the population and has no effective therapy. OBJECTIVE: To examine the safety and efficacy of oral desensitization in peanut-allergic children in combination with a brief course of anti-IgE mAb (omalizumab [Xolair]). METHODS: We performed oral peanut desensitization in peanut-allergic children at high risk for developing significant peanut-induced allergic reactions. Omalizumab was administered before and during oral peanut desensitization. RESULTS: We enrolled 13 children (median age, 10 years), with a median peanut-specific IgE level of 229 kU(A)/L and a median total serum IgE level of 621 kU/L, who failed an initial double-blind placebo-controlled food challenge at peanut flour doses of 100 mg or less. After pretreatment with omalizumab, all 13 subjects tolerated the initial 11 desensitization doses given on the first day, including the maximum dose of 500 mg peanut flour (cumulative dose, 992 mg, equivalent to >2 peanuts), requiring minimal or no rescue therapy. Twelve subjects then reached the maximum maintenance dose of 4000 mg peanut flour per day in a median time of 8 weeks, at which point omalizumab was discontinued. All 12 subjects continued on 4000 mg peanut flour per day and subsequently tolerated a challenge with 8000 mg peanut flour (equivalent to about 20 peanuts), or 160 to 400 times the dose tolerated before desensitization. During the study, 6 of the 13 subjects experienced mild or no allergic reactions, 5 subjects had grade 2 reactions, and 2 subjects had grade 3 reactions, all of which responded rapidly to treatment. CONCLUSIONS: Among children with high-risk peanut allergy, treatment with omalizumab may facilitate rapid oral desensitization and qualitatively improve the desensitization process.

TACI is mutant in common variable immunodeficiency and IgA deficiency.

The tumor necrosis factor receptor family member TACI (transmembrane activator and calcium-modulator and cyclophilin ligand interactor) mediates isotype switching in B cells. We found that 4 of 19 unrelated individuals with common variable immunodeficiency (CVID) and 1 of 16 individuals with IgA deficiency (IgAD) had a missense mutation in one allele of TNFRSF13B (encoding TACI). One of the four individuals with CVID had a single nucleotide insertion in the other TNFRSF13B allele. None of these mutations were present in 50 healthy subjects. TNFRSF13B mutations cosegregated with the phenotype of CVID or IgAD in family members of four index individuals that we studied. B cells from individuals with TACI mutations expressed TACI but did not produce IgG and IgA in response to the TACI ligand APRIL, probably reflecting impaired isotype switching. These results suggest that TACI mutations can result in CVID and IgAD.

The role of anti-IgA antibodies in causing adverse reactions to gamma globulin infusion in immunodeficient patients: a comprehensive review of the literature.

Anaphylactic reactions to immunoglobulin infusions in immunodeficient patients with undetectable IgA have been attributed in several reports to IgG or IgE anti-IgA antibodies. However, other reports have not supported an association between such antibodies and the development of severe reactions. We have reviewed the articles reporting reactions to immunoglobulin products in IgA-deficient patients, as well as those describing the presence of such antibodies in the absence of reactions to infusions. A variety of factors might influence the association of adverse reactions with anti-IgA antibodies, including the serum concentration and isotype (IgG or IgE) of the anti-IgA antibody, its specificity (class or subclass specific), the method of measurement, and the IgA content of the gamma globulin infusion and its route of administration. The role of anti-IgA antibodies in causing anaphylaxis in IgA-deficient patients receiving gamma globulin therapy is still controversial. Larger (multicenter) studies are needed to further evaluate this association.

The use of adjunctive therapies during oral immunotherapy: A focus on biologics.

Oral immunotherapy (OIT), thus far, is the most evaluated therapeutic approach for food allergy. However, OIT is not known to lead to a cure, and it carries a risk for allergic reactions. Adjunct therapies to OIT are currently being investigated to evaluate their effect on safety and outcome. Of these therapies, omalizumab is the most evaluated biologic. There is mounting evidence that omalizumab is effective in inducing rapid desensitization of OIT in both single-food and multiallergen OIT, while diminishing the rate of adverse reactions. Evaluation of other adjunct biologics, such as dupilumab and bacterial therapy, is underway.