Gastrointestinal Eosinophil Responses in a Longitudinal, Randomized Trial of Peanut Oral Immunotherapy.

BACKGROUND & AIMS: Gastrointestinal side effects are common during oral immunotherapy (OIT) and eosinophilic esophagitis (EoE) is a potential complication. We aimed to characterize eosinophilic gastrointestinal responses to peanut OIT, in which peanut protein is given orally, with incremental increases in dose over time. METHODS: Twenty adults with IgE-mediated peanut allergy were randomly assigned to groups given peanut OIT (n = 15) or placebo (n = 5); 1 additional subject withdrew before randomization. Serial gastrointestinal biopsies were collected at baseline (n = 21, 0 weeks), following dose escalation (n = 10, 52 weeks), and during the maintenance phase (n = 11, 104 weeks). Endoscopic findings were characterized using the EoE endoscopic reference score. Biopsies were assessed for eosinophils per high-power field (eos/hpf) and other pathology features using EoE histologic scoring system scores. We performed immunohistochemical analyses of eosinophil peroxidase deposition, quantified using automated image analysis. RESULTS: At baseline, no subjects reported current gastrointestinal symptoms. However, 3 of the 21 subjects (14%) had esophageal peak eosinophil counts ≥15 eos/hpf and all subjects had dilated intercellular spaces (DIS). OIT induced or exacerbated esophageal eosinophilia (EE) at 52 weeks in most subjects (peak eosinophil counts >5 eos/hpf in 6 of 7 patients [86%]; peak eosinophil counts ≥15 eos/hpf in 4 of 7 patients [57%]). One subject met clinicopathologic criteria for EoE and withdrew; no significant changes in esophageal peak eosinophil counts were observed in the placebo group. EE in the OIT group corresponded with significant increases in EoE histologic scoring system scores and deposition of eosinophil peroxidase. In 4 of 6 participants (67%), OIT-induced EE and gastrointestinal eosinophilia resolved by the end of the maintenance phase. Gastrointestinal symptoms were not clearly associated with EE or gastrointestinal eosinophilia. CONCLUSIONS: In this pilot study, we found that peanut OIT-induced EE and gastrointestinal eosinophilia are usually transient and are not always associated with gastrointestinal symptoms. Clinicaltrials.gov no: NCT02103270.

Corrigendum: Analysis of a Large Standardized Food Challenge Data Set to Determine Predictors of Positive Outcome Across Multiple Allergens.

[This corrects the article DOI: 10.3389/fimmu.2018.02689.].

Origins and clonal convergence of gastrointestinal IgE+ B cells in human peanut allergy.

B cells in human food allergy have been studied predominantly in the blood. Little is known about IgE+ B cells or plasma cells in tissues exposed to dietary antigens. We characterized IgE+ clones in blood, stomach, duodenum, and esophagus of 19 peanut-allergic patients, using high-throughput DNA sequencing. IgE+ cells in allergic patients are enriched in stomach and duodenum, and have a plasma cell phenotype. Clonally related IgE+ and non-IgE-expressing cell frequencies in tissues suggest local isotype switching, including transitions between IgA and IgE isotypes. Highly similar antibody sequences specific for peanut allergen Ara h 2 are shared between patients, indicating that common immunoglobulin genetic rearrangements may contribute to pathogenesis. These data define the gastrointestinal tract as a reservoir of IgE+ B lineage cells in food allergy.

Global metabolic profiling to model biological processes of aging in twins.

Aging is intimately linked to system-wide metabolic changes that can be captured in blood. Understanding biological processes of aging in humans could help maintain a healthy aging trajectory and promote longevity. We performed untargeted plasma metabolomics quantifying 770 metabolites on a cross-sectional cohort of 268 healthy individuals including 125 twin pairs covering human lifespan (from 6 months to 82 years). Unsupervised clustering of metabolic profiles revealed 6 main aging trajectories throughout life that were associated with key metabolic pathways such as progestin steroids, xanthine metabolism, and long-chain fatty acids. A random forest (RF) model was successful to predict age in adult subjects (≥16 years) using 52 metabolites (R2  = .97). Another RF model selected 54 metabolites to classify pediatric and adult participants (out-of-bag error = 8.58%). These RF models in combination with correlation network analysis were used to explore biological processes of healthy aging. The models highlighted established metabolites, like steroids, amino acids, and free fatty acids as well as novel metabolites and pathways. Finally, we show that metabolic profiles of twins become more dissimilar with age which provides insights into nongenetic age-related variability in metabolic profiles in response to environmental exposure.

Baseline Gastrointestinal Eosinophilia Is Common in Oral Immunotherapy Subjects With IgE-Mediated Peanut Allergy.

Rationale: Oral immunotherapy (OIT) is an emerging treatment for food allergy. While desensitization is achieved in most subjects, many experience gastrointestinal symptoms and few develop eosinophilic gastrointestinal disease. It is unclear whether these subjects have subclinical gastrointestinal eosinophilia (GE) at baseline. We aimed to evaluate the presence of GE in subjects with food allergy before peanut OIT. Methods: We performed baseline esophagogastroduodenoscopies on 21 adults before undergoing peanut OIT. Subjects completed a detailed gastrointestinal symptom questionnaire. Endoscopic findings were assessed using the Eosinophilic Esophagitis (EoE) Endoscopic Reference Score (EREFS) and biopsies were obtained from the esophagus, gastric antrum, and duodenum. Esophageal biopsies were evaluated using the EoE Histologic Scoring System. Immunohistochemical staining for eosinophil peroxidase (EPX) was also performed. Hematoxylin and eosin and EPX stains of each biopsy were assessed for eosinophil density and EPX/mm2 was quantified using automated image analysis. Results: All subjects were asymptomatic. Pre-existing esophageal eosinophilia (>5 eosinophils per high-power field [eos/hpf]) was present in five participants (24%), three (14%) of whom had >15 eos/hpf associated with mild endoscopic findings (edema, linear furrowing, or rings; median EREFS = 0, IQR 0-0.25). Some subjects also demonstrated basal cell hyperplasia, dilated intercellular spaces, and lamina propria fibrosis. Increased eosinophils were noted in the gastric antrum (>12 eos/hpf) or duodenum (>26 eos/hpf) in 9 subjects (43%). EPX/mm2 correlated strongly with eosinophil counts (r = 0.71, p < 0.0001). Conclusions: Pre-existing GE is common in adults with IgE-mediated peanut allergy. Eosinophilic inflammation (EI) in these subjects may be accompanied by mild endoscopic and histologic findings. Longitudinal data collection during OIT is ongoing.

Analysis of a Large Standardized Food Challenge Data Set to Determine Predictors of Positive Outcome Across Multiple Allergens.

Background: Double-blind placebo-controlled food challenges (DBPCFCs) remain the gold standard for the diagnosis of food allergy; however, challenges require significant time and resources and place the patient at an increased risk for severe allergic adverse events. There have been continued efforts to identify alternative diagnostic methods to replace or minimize the need for oral food challenges (OFCs) in the diagnosis of food allergy. Methods: Data was extracted for all IRB-approved, Stanford-initiated clinical protocols involving standardized screening OFCs to a cumulative dose of 500 mg protein to any of 11 food allergens in participants with elevated skin prick test (SPT) and/or specific IgE (sIgE) values to the challenged food across 7 sites. Baseline population characteristics, biomarkers, and challenge outcomes were analyzed to develop diagnostic criteria predictive of positive OFCs across multiple allergens in our multi-allergic cohorts. Results: A total of 1247 OFCs completed by 427 participants were analyzed in this cohort. Eighty-five percent of all OFCs had positive challenges. A history of atopic dermatitis and multiple food allergies were significantly associated with a higher risk of positive OFCs. The majority of food-specific SPT, sIgE, and sIgE/total IgE (tIgE) thresholds calculated from cumulative tolerated dose (CTD)-dependent receiver operator curves (ROC) had high discrimination of OFC outcome (area under the curves > 0.75). Participants with values above the thresholds were more likely to have positive challenges. Conclusions: This is the first study, to our knowledge, to not only adjust for tolerated allergen dose in predicting OFC outcome, but to also use this method to establish biomarker thresholds. The presented findings suggest that readily obtainable biomarker values and patient demographics may be of use in the prediction of OFC outcome and food allergy. In the subset of patients with SPT or sIgE values above the thresholds, values appear highly predictive of a positive OFC and true food allergy. While these values are relatively high, they may serve as an appropriate substitute for food challenges in clinical and research settings.

Anti-IgE treatment with oral immunotherapy in multifood allergic participants: a double-blind, randomised, controlled trial.

BACKGROUND: Despite progress in single food oral immunotherapy, there is little evidence concerning the safety and efficacy of treating individuals with multiple food (multifood) allergies. We did a pilot study testing whether anti-IgE (omalizumab) combined with multifood oral immunotherapy benefited multifood allergic patients. METHODS: We did a blinded, phase 2 clinical trial at Stanford University. We enrolled participants, aged 4-15 years, with multifood allergies validated by double-blind, placebo-controlled food challenges to their offending foods. Inclusion criteria included a positive skin prick test of 6 mm or more (wheal diameter, above the negative control), a food-specific serum IgE concentration of more than 4 kU/L for each food, or both, and a positive double-blind, placebo-controlled food challenge at 500 mg or less of food protein. Exclusion criteria included eosinophilic oesophagitis and severe asthma. Participants were randomised (3:1) with a block size of four, to receive multifood oral immunotherapy to two to five foods, together with omalizumab (n=36) or placebo (n=12). 12 individuals who fulfilled the same inclusion and exclusion criteria were included as controls. These individuals were not randomised and received neither omalizumab nor oral immunotherapy. Omalizumab or placebo was administered subcutaneously for 16 weeks, with oral immunotherapy starting at week 8, and was stopped 20 weeks before the exit double-blind, placebo-controlled food challenge at week 36. The primary endpoint was the proportion of participants who passed double-blind, placebo-controlled food challenges to at least two of their offending foods. This completed trial is registered with ClinicalTrials.gov, number NCT02643862. FINDINGS: Between March 25, 2015, and Aug 18, 2016, 165 participants were assessed for eligibility, of whom 84 did not meet the inclusion criteria and 21 declined to participate. We enrolled and randomised 48 eligible participants and the remaining 12 patients were included as nonrandomised, untreated controls. At week 36, a significantly greater proportion of the omalizumab-treated (30 [83%] of 36) versus placebo (four [33%] of 12) participants passed double-blind, placebo-controlled food challenges to 2 g protein for two or more of their offending foods (odds ratio 10·0, 95% CI 1·8-58·3, p=0·0044). All participants completed the study. There were no serious or severe (grade 3 or worse) adverse events. Participants in the omalizumab group had a significantly lower median per-participant percentage of oral immunotherapy doses associated with any adverse events (27% vs 68%; p=0·0082). The most common adverse events in both groups were gastrointestinal events. INTERPRETATION: In multifood allergic patients, omalizumab improves the efficacy of multifood oral immunotherapy and enables safe and rapid desensitisation. FUNDING: US National Institutes of Health (NIH).

Association of Clinical Reactivity with Sensitization to Allergen Components in Multifood-Allergic Children.

BACKGROUND: Thirty percent of children with food allergies have multiple simultaneous allergies; however, the features of these multiple allergies are not well characterized serologically or clinically. OBJECTIVE: We comprehensively evaluated 60 multifood-allergic patients by measuring serum IgE to key allergen components, evaluating clinical histories and medication use, performing skin tests, and conducting double-blind, placebo-controlled food challenges (DBPCFCs). METHODS: Sixty participants with multiple food allergies were characterized by clinical history, DBPCFCs, total IgE, specific IgE, and component-resolved diagnostics (IgE and IgG4) data. The food allergens tested were almond, egg, milk, sesame, peanut, pecan, walnut, hazelnut, cashew, pistachio, soy, and wheat. RESULTS: Our data demonstrate that of the reactions observed during a graded DBPCFC, gastrointestinal reactions occurred more often in boys than in girls, as well as in individuals with high levels of IgE to 2S albumins from cashew, walnut, and hazelnut. Certain food allergies often occurred concomitantly in individuals (ie, cashew/pistachio and walnut/pecan/hazelnut). IgE testing to components further corroborated serological relationships between and among these clustered food allergies. CONCLUSIONS: Associations of certain food allergies were shown by DBPCFC outcomes as well as by correlations in IgE reactivity to structurally related food allergen components. Each of these criteria independently demonstrated a significant association between allergies to cashew and pistachio, as well as among allergies to walnut, pecan, and hazelnut.

Observational long-term follow-up study of rapid food oral immunotherapy with omalizumab.

BACKGROUND: A number of clinical studies focused on treating a single food allergy through oral immunotherapy (OIT) with adjunctive omalizumab treatment have been published. We previously demonstrated safety and tolerability of a rapid OIT protocol using omalizumab in a phase 1 study to achieve desensitization to multiple (up to 5) food allergens in parallel, rapidly (7-36 weeks; median = 18 weeks). In the current long-term, observational study, we followed 34 food allergic participants for over 5 years, who had originally undergone the phase 1 rapid OIT protocol. METHODS: After reaching the maintenance dose of 2 g protein for each of their respective food allergens as a part of the phase 1 study, the long-term maintenance dose was reduced for some participants based on a pragmatic team-based decision. Participants were followed up to 62 months through standard oral food challenges (OFCs), skin prick tests, and blood tests. RESULTS: Each participant passed the 2 g OFC to each of their offending food allergens (up to 5 food allergens in total) at the end of the long-term follow-up (LTFU) study. CONCLUSION: Our data demonstrate the feasibility of long-term maintenance dosing of a food allergen without compromising the desensitized status conferred through rapid-OIT. Trial registration Registry: Clinicaltrials.gov. Registration numbers: NCT01510626 (original study), NCT03234764 (LTFU study). Date of registration: November 29, 2011 (original study); July 26, 2017 (LTFU study, retrospectively registered).

Feasibility of sustained response through long-term dosing in food allergy immunotherapy.

BACKGROUND: Clinical trials using oral immunotherapy (OIT) for the treatment of food allergies have shown promising results. We previously demonstrated the feasibility of desensitization for up to 5 food allergens simultaneously through OIT. In this observational study, we report the findings of long-term follow-up (LTFU) of the participants treated through a single site OIT phase 1 trial. METHODS: The participants (n = 46) were followed up to 72 months since the time they reached 2 g maintenance dose per food in the initial phase 1 trial. During the long-term maintenance dosing, participants continued or reduced the initial maintenance dose of food allergen protein to high (median 2 g protein) vs. low (median 300 mg protein). Participant follow-up included clinical monitoring, standardized OFCs, and in some cases, skin prick tests and measurement of allergen-specific IgE and IgG4. RESULTS: Irrespective of the high vs. low long-term maintenance dose during LTFU, all participants were able to ingest 2 g protein of each food allergen protein during OFCs performed at the end of our LTFU. CONCLUSION: Our LTFU cohort of food OIT participants from a single site, phase 1 OIT study, supports the feasibility of sustained desensitization through long-term maintenance dosing. Trial registration Registry: Clinicaltrial.gov. Registration numbers: NCT01490177 (original study); NCT03234764 (LTFU study). Date of registration: November 29, 2011 (original study); July 26, 2017 (LTFU study, registered).

Deciphering the black box of food allergy mechanisms.

OBJECTIVE: To review our current understanding of immunotherapy, the immune mechanisms underlying food allergy, and the methodological advances that are furthering our understanding of the role of immune cells and other molecules in mediating food allergies. DATA SOURCES: Literature searches were performed using the following combination of terms: allergy, immunotherapy, food, and mechanisms. Data from randomized clinical studies using state-of-the-art mechanistic tools were prioritized. STUDY SELECTIONS: Articles were selected based on their relevance to food allergy. RESULTS: Current standard of care for food allergies is avoidance of allergenic foods and the use of epinephrine in case of severe reaction during unintentional ingestion. During the last few decades, great strides have been made in understanding the cellular and molecular mechanisms underlying food allergy, and this information is spearheading the development of exciting new treatments. CONCLUSION: Immunotherapy protocols are effective in desensitizing individuals to specific allergens; however, recurrence of allergic sensitization is common after discontinuation of therapy. Interestingly, in a subset of individuals, immunotherapy is protective against allergens even after discontinuation of immunotherapy. Whether this protection is permanent is currently unknown because of inadequate long-term follow-up data. Research on understanding the underlying mechanisms may assist in modifying protocols to improve outcome and enable sustained unresponsiveness, rather than a temporary relief against food allergies. The cellular changes brought about by immunotherapy are still a black box, but major strides in our understanding are being made at an exciting pace.

Diagnosis of Food Allergy.

The prevalence of food allergies has been on the increase over the last 2 decades. Diagnosing food allergies can be complicated, as there are multiple types that have distinct clinical and immunologic features. Food allergies are broadly classified into immunoglobulin E (IgE)-mediated, non-IgE-mediated, or mixed food allergic reactions. This review focuses on the clinical manifestations of the different categories of food allergies and the different tests available to guide the clinician toward an accurate diagnosis.