Successful immunotherapy induces previously unidentified allergen-specific CD4+ T-cell subsets

Abstract

Allergen immunotherapy can desensitize even subjects with potentially lethal allergies, but the changes induced in T cells that underpin successful immunotherapy remain poorly understood. In a cohort of peanut-allergic participants, we used allergen-specific T-cell sorting and single-cell gene expression to trace the transcriptional "roadmap" of individual CD4+ T cells throughout immunotherapy. We found that successful immunotherapy induces allergen-specific CD4+ T cells to expand and shift toward an "anergic" Th2 T-cell phenotype largely absent in both pretreatment participants and healthy controls. These findings show that sustained success, even after immunotherapy is withdrawn, is associated with the induction, expansion, and maintenance of immunotherapy-specific memory and naive T-cell phenotypes as early as 3 mo into immunotherapy. These results suggest an approach for immune monitoring participants undergoing immunotherapy to predict the success of future treatment and could have implications for immunotherapy targets in other diseases like cancer, autoimmune disease, and transplantation.is a process in which small amounts of allergen are given over time to the allergic individual until they can safely tolerate high amounts of allergen with no signs of clinical symptoms (1-9). In the regimen of oral IT for peanut-allergic patients (identified by an allergic reaction during a standardized blinded food challenge to peanut), small amounts of peanut flour protein are ingested and escalated to a servings-worth of peanut protein (4 g of peanut protein) over a period of 2-3 y (6-7). Most patients require continuous frequent (e.g., daily) exposure to such therapy for beneficial clinical outcomes. Mechanistic studies of oral IT to food allergens, although limited to date, show that plasma markers such as IgE and IgG4 immunoglobulins, skin test markers, component testing, and basophil activation tests are only weakly predictive of long-term clinical success (10-16). T cells are critical upstream regulators of allergic sensitization that are required to help B cells to synthesize IgE/IgG4 immunoglobulins, which then can activate or inhibit basophils and mast cells (10-17). Moreover, successful IT is associated with the development of regulatory T cells (Tregs) that are thought to dampen allergic reactivity to offending allergens (7). We therefore focused on finding T-cell markers of immune tolerance that could be detected early in the peripheral blood during IT. CD4+ T cells can be relatively long-lived (compared with plasma proteins and basophils) and changes detected early in populations of T cells could perhaps predict longer-lasting successful IT. For example, in one of the first studies in peanut allergen IT to withdraw therapy for more than 10 wk, we previously showed that despite negative skin tests to peanut, and high IgG4/low specific IgE levels to peanut, and decreased basophil reactivity to the allergen, some patients who withdrew from therapy for 3-6 mo were still reactive upon rechallenge with peanut (7...

Food allergy: immune mechanisms, diagnosis and immunotherapy

“…The mechanisms by which mast cell and basophil responsiveness to degranulation are decreased early during immunotherapy are under investigation 76 . Other changes to the immune system observed after immunotherapy include increased numbers of anergic antigen-specific T cells 77 , apoptotic antigen-specific T cells 78–81 and FOXP3 + T reg cells 80,82 , as well as increased levels of TGFβ1 (REFS 77,83). For example, over the course of OIT, antigen-specific CD4 + T cells were found to transition from allergic and regulatory phenotypes to anergic and non-allergic phenotypes, in association with decreased allergic symptoms and the development of sustained unresponsiveness 77 .…”

Molecular and cellular mechanisms of food allergy and food tolerance

“…Moreover, sustained nonresponsiveness to peanut, even after a 3-month period of withdrawal from peanut, was associated with induction and maintenance of naïve and memory peanut-specific T cells that were detectable even 3 months after therapy. 172 The failure to maintain tolerance to the offending allergen may be due to the induction of Tregs that are short lived or epigenetically modified. In our cohort of subjects who completed 24 months of peanut OIT (20/23 subjects), we have shown that 7/20 subjects were still “immune tolerant” after a 3 month period of withdrawal, and 3/7 remained “immune tolerant” after an additional 3 month withdrawal period (totaling 6 months of withdrawal from therapy).…”

Pathogenic CD4 + T cells in patients with asthma

“…159 A major strength is that it allows the assessment of approximately 100 gene transcripts within a single cell by selecting specific genes for study or else many thousands of transcripts by using genome-wide analyses with single-cell RNAsequencing. 160 Other single-cell platforms now enable functional assays of a single cell in vitro .…”