Epicutaneous allergen immunotherapy induces a profound and selective modulation in skin dendritic cell subsets

Evaluation of peanut tolerance in sensitized mice through intradermal allergen delivery with adjuvants

Peanut allergy is a significant worldwide health issue and requires innovative approaches to provide safer and more effective treatments. This study explores the potential of intradermal immunotherapy using peanut formulations combined with adjuvants. Six groups of BALB/c mice previously sensitized to peanut received intradermal treatments every other week for three months comprising of: Group 1 (G1) = Peanut extract (PE) + epinephrine (EPN); G2 = PE + EPN + topical Aldara® pretreatment; G3 = PE + EPN + topical imiquimod (IMQ) micellar gel pretreatment; G4 = PE + EPN + monophosphoryl lipid A (MPLA) + IMQ; G5 = PE + EPN + IMQ; G6 = Peanut powder + EPN + hyaluronic acid (HA). Clinical scores of peanut allergy, serological levels of peanut-specific IgE (Pe-IgE), IgG1, IgG2a, and histamine were compared before and after treatment, alongside studies on IMQ permeation and the pharmacokinetics of major peanut allergen ara h 2. Clinical scores improved significantly in all groups except G2 (trend towards improvement without statistical significance). Pe-IgE level decreased in G1, G2, and G3, while Pe-IgG1 increased in G1, G3, and G4. G3 alone showed a significant rise in Pe-IgG2a. No group was statistically superior to G1 after adjusting for differences in cumulative allergen doses received and initial IgE levels. Ex vivo experiments revealed that IMQ micellar gel in G3 enhanced skin permeation compared to Aldara®. Additionally, ara h 2 absorption was significantly reduced in naive mice treated with PE and HA. Baseline treatment of PE and EPN effectively reduced markers of peanut allergy. However, addition of TLR-agonist adjuvants or HA did not yield statistically significant improvements compared to baseline (G1).

Epicutaneous immunotherapy: A review of safety and efficacy

Epcutaneous immunotherapy (EPIT) is a novel, non-oral route of allergen immunotherapy, utilizing the skin and its robust density of epidermal Langerhans cells (LC) for antigen presentation. This space is non-vascularized and impermeable, which limits allergen exposure into the bloodstream but preserves antigen presentation to regional lymph nodes to generate gut-homing regulatory T cells. The EPIT patch utilizes natural water loss from the skin to absorb electrosprayed allergen through condensation. EPIT represents an alternative, non-oral route of immunotherapy for food allergy, with good efficacy and strong safety profiles across multiple phase 2 and 3 studies for milk and peanut. Efficacy appears the best in very young children (1-3 years old), which has been shown to continue to enhance with extended treatment duration up to 36 months. Efficacy in slightly older children ages 4-11 years of age is less clear, but appears to be better in children ages 4-7 years of age. In clinical trials of milk and peanut EPIT, most subjects experienced adverse effects, mainly mild-to-moderate skin reactions localized around the patch placement site, which improve with continued duration of wear. Rates of treatment-related anaphylaxis have been very low across all studies and ages, ranging from 1.6% to 4%, and were lowest in the infant and toddler population. While further studies of safety (1- to 3-year-olds) and efficacy (4- to 7-year-olds) are ongoing, EPIT is a potentially valuable addition to the current landscape of food allergy therapies, in particular for infants and toddlers where families may be seeking a non-oral route of treatment.

T follicular helper cells in food allergy

T follicular helper (Tfh) cells help direct the production of antibodies by B cells. In addition to promoting antibody responses to vaccination and infection, Tfh cells have been found to mediate antibody production to food antigens. Work over the past decade has delineated the specific phenotypes of Tfh cells that induce antibodies to food while also clarifying the divergent Tfh cell requirement for different food-specific antibody isotypes. Furthermore, Tfh and antibody responses to food can occur at multiple barrier sites - namely, skin, airway, and gut. Depending on the context of food antigen exposure, the immune response to food at these sites can be protective, as in the case of tolerance or immunotherapy, or pathogenic, as in the case of allergy. This review will highlight recent advances in our understanding of how Tfh cells promote antibodies to food as well as future avenues for continued discovery.

Dendritic cells in food allergy, treatment, and tolerance

Food allergy is a growing problem with limited treatment options. It is important to understand the mechanisms of food tolerance and allergy to promote the development of directed therapies. Dendritic cells (DCs) are specialized antigen-presenting cells (APCs) that prime adaptive immune responses, such as those involved in the development of oral tolerance and food allergies. The DC subsets in the gut and skin are defined by their surface markers and function. The default response to an ingested innocuous antigen is oral tolerance, which requires either gut DCs or a subset of newly identified RORγt+ APCs to induce the development of gut peripheral regulatory T cells. However, DCs in the skin, gut, and lung can also promote allergic sensitization when they are activated under certain inflammatory conditions, such as with alarmin release or gut dysbiosis. DCs also play a role in the responses to the various modalities of food immunotherapy. Langerhans cells in the skin appear to be necessary for the response to epicutaneous immunotherapy. It will be important to determine which real-world stimuli activate the DCs that prime allergic sensitization and discover methods to selectively initiate a tolerogenic program in APCs.

Recent advances in epicutaneous immunotherapy and potential applications in food allergy

Given the potent immunological properties of the skin, epicutaneous immunotherapy (EPIT) emerges as a promising treatment approach for inducing immune tolerance, particularly for food allergies. Targeting the highly immunocompetent, non-vascularized epidermis allows for the application of microgram amounts of allergen while significantly reducing the risk of allergen passage into the bloodstream, thus limiting systemic allergen exposure and distribution. This makes EPIT highly suitable for the treatment of potentially life-threatening allergies such as food allergies. Multiple approaches to EPIT are currently under investigation for the treatment of food allergy, and these include the use of allergen-coated microneedles, application of allergen on the skin pretreated by tape stripping, abrasion or laser-mediated microperforation, or the application of allergen on the intact skin using an occlusive epicutaneous system. To date, the most clinically advanced approach to EPIT is the Viaskin technology platform. Viaskin is an occlusive epicutaneous system (patch) containing dried native allergen extracts, without adjuvants, which relies on frequent application for the progressive passage of small amounts of allergen to the epidermis through occlusion of the intact skin. Numerous preclinical studies of Viaskin have demonstrated that this particular approach to EPIT can induce potent and long-lasting T-regulatory cells with broad homing capabilities, which can exert their suppressive effects in multiple organs and ameliorate immune responses from different routes of allergen exposure. Clinical trials of the Viaskin patch have studied the efficacy and safety for the treatment of life-threatening allergies in younger patients, at an age when allergic diseases start to occur. Moreover, this treatment approach is designed to provide a non-invasive therapy with no restrictions on daily activities. Taken together, the preclinical and clinical data on the use of EPIT support the continued investigation of this therapeutic approach to provide improved treatment options for patients with allergic disorders in the near future.

Innovative delivery systems for epicutaneous immunotherapy

Allergen-specific immunotherapy (AIT) describes the establishment of peripheral tolerance through repeated allergen exposure, which qualifies as the only curative treatment for allergic diseases. Although conventional subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) have been approved to treat respiratory allergies clinically, the progress made is far from satisfactory. Epicutaneous immunotherapy (EPIT) exploits the skin's immune properties to modulate immunological response, which is emerging as a promising alternative and has shown effectiveness in many preclinical and clinical studies for both respiratory and food allergies. It is worth noting that the stratum corneum (SC) barrier impedes the effective delivery of allergens, while disrupting the SC layer excessively often triggers unexpected Th2 immune responses. This work aims to comprehend the immunological mechanisms of EPIT, and summarize the innovative system for sufficient delivery of allergens as well as tolerogenic adjuvants. Finally, the safety, acceptability, and cost-effectiveness of these innovative delivery systems are discussed, which directs the development of future immunotherapies with all desirable characteristics.

Deciphering Differential Behavior of Immune Responses as the Foundation for Precision Dosing in Allergen Immunotherapy

Like in many fields of medicine, the concept of precision dosing has re-emerged in routine practice in allergology. Only one retrospective study on French physicians' practice has addressed this topic so far and generated preliminary data supporting dose adaptation, mainly based on experience, patient profile understanding and response to treatment. Both intrinsic and extrinsic factors shape the individual immune system response to allergen immunotherapy (AIT). Herein, we focus on key immune cells (i.e., dendritic cells, innate lymphoid cells, B and T cells, basophils and mast cells) involved in allergic disease and its resolution to further understand the effect of AIT on the phenotype, frequency or polarization of these cells. We strive to discriminate differences in immune responses between responders and non-responders to AIT, and discuss the eligibility of a non/low-responder subset for dose adaptation. A differential behavior in immune cells is clearly observed in responders, highlighting the importance of conducting clinical trials with large cohorts of well-characterized subjects to decipher the immune mechanism of AIT. We conclude that there is a need for designing new clinical and mechanistic studies to support the scientific rationale of dose adaptation in the interest of patients who do not properly respond to AIT.

Immunotherapy: State-of-the-art review of therapies and theratypes

Through its disease-modifying potential, immunotherapy is the keystone to curing allergic diseases. Allergen immunotherapy, applied for more than a century, is currently supported by novel modalities such as mAb-based therapies or small molecules targeting the key nodes of the allergic inflammation network. In this review, a summary of the most significant advances in immunotherapy is presented, addressing not only novel approaches to stratifying patients but also major controlled clinical trials and real-world evidence that strengthen the role of immunotherapy in the treatment of allergies.

Immunology of allergen immunotherapy

Allergen immunotherapy (AIT) is the only disease-modifying therapy for allergic disease. Through repeated inoculations of low doses of allergen-either as whole proteins or peptides-patients can achieve a homeostatic balance between inflammatory effectors induced and/or associated with allergen contact, and mediators of immunologic non-responsiveness, potentially leading to sustained clinical improvements. AIT for airborne/respiratory tract allergens and insect venoms have traditionally been supplied subcutaneously, but other routes and modalities of administration can also be effective. Despite differences of allergen administration, there are some similarities of immunologic responses across platforms, with a general theme involving the restructuring and polarization of adaptive and innate immune effector cells. Here we review the immunology of AIT across various delivery platforms, including subcutaneous, sublingual, epicutaneous, intradermal, and intralymphatic approaches, emphasizing shared mechanisms associated with achieving immunologic non-responsiveness to allergen.