Sublingual immunotherapy for peanut allergy: clinical and immunologic evidence of desensitization

Influence of sublingual immunotherapy on the expression of Mac-1 integrin in neutrophils from asthmatic children

Asthma can be effectively treated with sublingual immunotherapy. The influence of -sublingual immunotherapy on the function of granulocytes in asthmatic patients is largely unknown. Mac-1 integrin is a transmembrane protein containing α (CD11b) and β (CD18) chains. High expression of the complex is found on the surface of neutrophils, NK cells, and macrophages. CD11b/CD18 may bind to CD23, ICAM-1, ICAM-2, and ICAM-4. It plays a crucial role in diapedesis of neutrophils. The aim of the present study was to assess Mac-1 expression on neutrophils from asthmatic children before and after sublingual immunotherapy. Twenty five children aged of 8.1 ± 3.1 suffering from atopic asthma and allergic rhinitis, shortlisted for specific immunotherapy, served as the study group. Fifteen healthy individuals, aged 9.8 ± 3.4, served as a control group. The assessment of CD11b and CD18 expression on cells from peripheral blood was performed with a flow cytometer. The tests were performed before and after 12 months of sublingual immunotherapy. In the asthmatic children, 98.08 (90.79-99.12)% of Mac-1 positive neutrophils were detected. The group was divided into two subgroups: of more than 98% and less than 95% of neutrophils with CD11b/CD18 expression in the sample. After immunotherapy, the percentage of Mac-1 positive granulocytes increased to 99.60 (99.29-99.68)%, p = 0.01. In the control group, 90.56 (87.08-88.86)% granulocytes were Mac-1 positive, p = 0.002. We conclude that sublingual immunotherapy strongly influences the function of the immunological system, including Mac-1 expression on neutrophils.

IgE, but not IgG4, antibodies to Ara h 2 distinguish peanut allergy from asymptomatic peanut sensitization

BACKGROUND

There are no available clinical tests that can accurately predict peanut allergy (PA) and/or anaphylaxis. This study is aimed at evaluating whether the component-resolved diagnostic (CRD) IgE and IgG4 tests can (i) distinguish PA from asymptomatic peanut sensitization (PS) and (ii) differentiate anaphylactic from nonanaphylactic PA.

METHODS

This study included 20 nonatopic controls, 58 asymptomatically peanut-sensitized children, 55 nonanaphylactic, and 53 anaphylactic PA cases from the Chicago Food Allergy Study. IgE and IgG4 to 103 allergens were measured using the ImmunoCAP ISAC technology and were compared among each group of children. The random forest test was applied to estimate each allergen's ability to predict PA and/or peanut anaphylaxis.

RESULTS

Peanut allergy cases (with or without anaphylaxis) had significantly higher IgE reactivity to Ara h 1-3 (peanut allergens) and Gly m 5-6 (soy allergens) than asymptomatically sensitized children (P < 0.00001). Similar but more modest relationships were found for IgG4 to Ara h 2 (P < 0.01). IgE to Ara h 2 was the major contributor to accurate discrimination between PA and asymptomatic sensitization. With an optimal cutoff point of 0.65 ISU-E, it conferred 99.1% sensitivity, 98.3% specificity, and a 1.2% misclassification rate in the prediction of PA, which represented a higher discriminative accuracy than IgE to whole peanut extract (P = 0.008). However, none of the IgE and/or IgG4 tests could significantly differentiate peanut anaphylaxis from nonanaphylactic PA.

CONCLUSIONS

IgE to Ara h 2 can efficiently differentiate clinical PA from asymptomatic PS, which may represent a major step forward in the diagnosis of PA.

Oral immunotherapy for food allergy: towards a new horizon

Food allergy has increased dramatically in prevalence over the past decade in westernized countries, and is now a major public health problem. Unfortunately for patients with food allergy, there is no effective therapy beyond food allergen avoidance, and rapid medical treatment for accidental exposures. Recently, oral immunotherapy (OIT) has been investigated as a treatment for this problem. In this review, we will discuss the progress in developing OIT for food allergy, including a novel approach utilizing Xolair (anti-IgE monoclonal antibody, omalizumab) in combination with OIT. This combination may enhance both the safety and efficacy of oral immunotherapy, and could lead to a widely available and safe therapy for food allergy.

Blockade of peanut allergy with a novel Ara h 2-Fcγ fusion protein in mice

BACKGROUND

Conventional immunotherapy for peanut allergy using crude peanut extracts is not recommended because of the unacceptably high risk of anaphylaxis. Allergen-specific immunotherapy is not currently undertaken for peanut allergy.

OBJECTIVES

The objective of this study was to develop a novel peanut-human fusion protein to block peanut-induced anaphylaxis.

METHODS

We genetically designed and expressed a novel plant-human fusion protein composed of the major peanut allergen Ara h 2 and human IgG Fcγ1. We tested the Ara h 2-Fcγ fusion protein (AHG2)'s function in purified human basophils. Transgenic mice expressing human FcεRIα and a murine peanut allergy model were used.

RESULTS

AHG2 inhibited histamine release induced by whole peanut extract (WPE) from basophils of patients with peanut allergy, whereas the fusion protein itself did not induce mediator release. AHG2 inhibited the WPE-induced, peanut-specific, IgE-mediated passive cutaneous anaphylaxis in hFcεRIα transgenic mice. AHG2 also significantly inhibited acute anaphylactic reactivity, including the prototypical decrease in body temperature in WPE-sensitized mice challenged with crude peanut extract. Histologic evaluation of the airways showed that AHG2 decreased peanut-induced inflammation, whereas the fusion protein itself did not induce airway inflammation in peanut-sensitized mice. AHG2 did not exert an inhibitory effect in mice lacking FcγRII.

CONCLUSION

AHG2 inhibited peanut-specific IgE-mediated allergic reactions in vitro and in vivo. Linking specific peanut allergen to Fcγ can provide a new approach for the allergen immunotherapy of peanut allergy.

Allergen-specific oral immunotherapy for peanut allergy

BACKGROUND

Peanut allergy is one of the most common forms of food allergy encountered in clinical practice.  In most cases, it does not spontaneously resolve; furthermore, it is frequently implicated in acute life-threatening reactions. The current management of peanut allergy centres on meticulous avoidance of peanuts and peanut-containing foods. Allergen-specific oral immunotherapy (OIT) for peanut allergy aims to induce desensitisation and then tolerance to peanut, and has the potential to revolutionise the management of peanut allergy. However, at present there is still considerable uncertainty about the effectiveness and safety of this approach.

OBJECTIVES

To establish the effectiveness and safety of OIT in people with IgE-mediated peanut allergy who develop symptoms after peanut ingestion.

SEARCH METHODS

We searched in the following databases: AMED, BIOSIS, CAB, CINAHL, The Cochrane Library, EMBASE, Global Health, Google Scholar, IndMed, ISI Web of Science, LILACS, MEDLINE, PakMediNet and TRIP. We also searched registers of on-going and unpublished trials. The date of the most recent search was January 2012.

SELECTION CRITERIA

Randomised controlled trials (RCTs), quasi-RCTs or controlled clinical trials involving children or adults with clinical features indicative of IgE-mediated peanut allergy treated with allergen-specific OIT, compared with control group receiving either placebo or no treatment, were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently checked and reviewed titles and abstracts of identified studies and assessed risk of bias. The full text of potentially relevant trials was assessed. Data extraction was independently performed by two reviewers with disagreements resolved through discussion.

MAIN RESULTS

We found one small RCT, judged to be at low risk of bias, that enrolled 28 children aged 1 to 16 years with evidence of sensitisation to peanut and a clinical history of reaction to peanut within 60 minutes of exposure. The study did not include children who had moderate to severe asthma or who had a history of severe peanut anaphylaxis. Randomisation was in a 2:1 ratio resulting in 19 children being randomised to the intervention arm and nine to the placebo arm. Intervention arm children received OIT with peanut flour and control arm participants received placebo comprising of oat flour. The primary outcome was assessed using a double-blind, placebo controlled oral food challenge (OFC) at approximately one year. No data were available on longer term outcomes beyond the OFC conducted at the end of the study.Because of adverse events, three patients withdrew from the intervention arm before the completion of the study. Therefore, only 16 participants received the full course of peanut OIT, whereas all nine patients receiving placebo completed the trial. The per-protocol analysis found a significant increase in the threshold dose of peanut allergen required to trigger a reaction in those in the intervention arm with all 16 participants able to ingest the maximum cumulative dose of 5000 mg of peanut protein (which the authors equate as being equivalent to approximately 20 peanuts) without developing symptoms, whereas in the placebo group they were able to ingest a median cumulative dose of 280 mg (range: 0 to 1900 mg, P < 0.001) before experiencing symptoms.  Per-protocol analyses also demonstrated that peanut OIT resulted in reductions in skin prick test size (P < 0.001), interleukin-5 (P = 0.01), interleukin-13 (P = 0.02) and an increase in peanut-specific immunoglobulin G(4) (IgG(4)) (P < 0.01).Children in the intervention arm experienced more adverse events during treatment than those in the placebo arm. In the initial day escalation phase, nine (47%) of the 19 participants initially enrolled in the OIT arm experienced clinically-relevant adverse events which required treatment with H(1)-antihistamines, two of which required additional treatment with epinephrine (adrenaline).

AUTHORS' CONCLUSIONS

The one small RCT we found showed that allergen-specific peanut OIT can result in desensitisation in children, and that this is associated with evidence of underlying immune-modulation. However, this treatment approach was associated with a substantial risk of adverse events, although the majority of these were mild.  In view of the risk of adverse events and the lack of evidence of long-term benefits, allergen-specific peanut OIT cannot currently be recommended as a treatment for the management of patients with IgE-mediated peanut allergy.  Larger RCTs are needed to investigate the acceptability, long-term effectiveness and cost-effectiveness of safer treatment regimens, particularly in relation to the induction of clinical and immunological tolerance.

Advances in immunotherapy for food allergy

Food allergy is a life-threatening allergic disease that is increasing in prevalence with no approved curative therapy. Standard treatment of food allergy is limited to avoidance of the allergen and supportive management of allergic symptoms and anaphylaxis. Current research, however, has been focused on developing therapy that can modify the allergic immune response in both allergen-specific and non-specific methods. This review will provide an overview of these methods including oral immunotherapy, sublingual immunotherapy, epicutaneous immunotherapy, modified food protein vaccines, anti-IgE monoclonal antibody adjuvant therapy, Chinese herbs, and helminth therapy.

Oral immunotherapy for cow's milk allergy

PURPOSE OF REVIEW

Cow's milk allergy (CMA) is common in children and may lead to severe systemic reactions. Avoidance of the ingestion of cow milk is the only effective approach, but this does not exclude the inadvertent or accidental ingestion, or the assumption of milk hidden in other foods. As no pharmacological treatment is available, specific desensitization has been considered an attractive strategy.

RECENT FINDINGS

In the last years, several trials of oral desensitization to cow milk, with different protocols, were published. Overall the results were favourable and demonstrated the achievement of a full tolerance in a high percentage of children. Mild side effects that can be easily managed by slowing the desensitization were reported frequently. The discontinuation of the procedure was necessary in less than 20% of children, on average, due to severe side effects.

SUMMARY

Oral immunotherapy (oral desensitization) seems to be a promising treatment strategy for cow milk allergy in children that can be applied also to other foods such as eggs or peanuts.

Future therapies for food allergy

Food allergy affects 3.9% of US children and is increasing in prevalence. The current standard of care involves avoidance of the triggering food and treatment for accidental ingestions. While there is no current curative treatment, there are a number of therapeutic strategies under investigation. Allergen specific therapies include oral and sublingual immunotherapy with native food protein as well as recombinant food proteins. Allergen non-specific therapies include a Chinese herbal formula (FAHF-2) and the use of anti-IgE monoclonal antibody therapy. Although none of these treatments are ready for clinical use, these therapeutic strategies present promising options for the future of food allergy.

A European perspective on immunotherapy for food allergies

Food allergies are common, and frequently, the only treatment option is strict avoidance. Unfortunately, many patients accidentally ingest allergenic foods, which can result in severe anaphylactic reactions. Several immunotherapies are being developed for food allergies; these involve oral, sublingual, epicutaneous, or subcutaneous administration of small amounts of native or modified allergens to induce immune tolerance. Oral immunotherapy seems to be the most promising approach based on results from small uncontrolled and controlled studies. However, it is a challenge to compare results among immunotherapy trials because of differences in protocols. Studies conducted thus far have tested the most prevalent food allergens: it is not clear whether their results can be extended to other allergens. Sublingual administration of immunotherapy has shown some efficacy and fewer side effects than oral administration in some trials, yet neither approach can be recommended for routine practice. Controlled studies with larger numbers of subjects are needed to determine short- and long-term efficacy and side effects. In Europe immunotherapy trials for food allergies face many ethical and regulatory issues. Guidelines from the European Medicine Agency on the clinical development of products for specific immunotherapy of allergic diseases do not adequately address immunotherapy for food allergies, especially for therapies that orally administer native food or that include pediatric patients.

Immunological mechanisms for desensitization and tolerance in food allergy

Food allergy is a major public health concern in westernized countries, estimated to affect 5 % of children and 3-4 % of adults. Allergen-specific immunotherapy for food allergy is currently being actively evaluated, but is still experimental. The optimal protocol, in terms of the route of administration of the food, target maintenance dose, and duration of maintenance therapy, and the optimal patient for these procedures are still being worked out. The mechanisms underlying successful food desensitization are also unclear, in part, because there is no standard immunotherapy protocol. The mechanisms involved, however, may include mast cell and basophil suppression, development of food-specific IgG4 antibodies, reduction in the food-specific IgE/IgG4 ratio, up-regulation and expansion of natural or inducible regulatory T cells, a skewing from a Th2 to a Th1 profile, and the development of anergy and/or deletion in antigen-specific cells. Additional studies are required to elucidate and understand these mechanisms by which desensitization and tolerance are achieved, which may reveal valuable biomarkers for evaluating and following food allergic patients on immunotherapy.

Pepsinized cashew proteins are hypoallergenic and immunogenic and provide effective immunotherapy in mice with cashew allergy

BACKGROUND

IgE-mediated allergic reactions to cashews and other nuts can trigger life-threatening anaphylaxis. Proactive therapies to decrease reaction severity do not exist.

OBJECTIVES

We aimed to determine the efficacy of pepsin-digested cashew proteins used as immunotherapy in a murine model of cashew allergy.

METHODS

Mice were sensitized to cashew and then underwent challenges with digested or native cashew allergens to assess the allergenicity of the protein preparations. Using native or pepsinized cashew proteins, mice underwent oral or intraperitoneal sensitization protocols to determine the immunogenic properties of the protein preparations. Finally, cashew-sensitized mice underwent an immunotherapy protocol with native or pepsinized cashew proteins and subsequent provocation challenges.

RESULTS

Pepsinized cashew proteins elicited weaker allergic reactions than native cashew proteins but importantly retained the ability to stimulate cellular proliferation and cytokine production. Mice sensitized with pepsinized proteins reacted on challenge with native allergens, demonstrating that pepsinized allergens retain immunogenicity in vivo. Immunotherapy with pepsinized cashew allergens significantly decreased allergic symptoms and body temperature decrease relative to placebo after challenge with native and pepsinized proteins. Immunologic changes were comparable after immunotherapy with native or pepsinized allergens: T(H)2-type cytokine secretion from splenocytes was decreased, whereas specific IgG(1) and IgG(2a) levels were increased.

CONCLUSIONS

Pepsinized cashew proteins are effective in treating cashew allergy in mice and appear to work through the same mechanisms as native protein immunotherapy.

Advances in allergic skin disease, anaphylaxis, and hypersensitivity reactions to foods, drugs, and insects in 2011

This review highlights some of the research advances in anaphylaxis; hypersensitivity reactions to foods, drugs, and insects; and allergic skin diseases that were reported in the Journal in 2011. Food allergy appears to be increasing in prevalence and carries a strong economic burden. Risk factors can include dietary ones, such as deficiency of vitamin D and timing of complementary foods, and genetic factors, such as filaggrin loss-of-function mutations. Novel mechanisms underlying food allergy include the role of invariant natural killer T cells and influences of dietary components, such as isoflavones. Among numerous preclinical and clinical treatment studies, promising observations include the efficacy of sublingual and oral immunotherapy, a Chinese herbal remedy showing promising in vitro results, the potential immunotherapeutic effects of having children ingest foods with baked-in milk if they tolerate it, and the use of anti-IgE with or without concomitant immunotherapy. Studies of allergic skin diseases, anaphylaxis, and hypersensitivity to drugs and insect venom are elucidating cellular mechanisms, improved diagnostics, and potential targets for future treatment. The role of skin barrier abnormalities, as well as the modulatory effects of the innate and adaptive immune responses, are major areas of investigation.

The future of food allergy therapeutics

Food allergy is increasing in prevalence in westernized countries, leading to significant morbidity including nutritional deficiencies and growth delay as well as psychosocial burdens and the potential for fatal anaphylaxis. There is currently no effective form of therapy, and the mainstay of treatment remains strict avoidance. However, there are a number of promising therapeutic strategies currently being investigated for the treatment of food allergies. Allergen-specific approaches, such as various forms of immunotherapy, have been a major focus of investigation and appear to be promising methods of desensitization. More recently, the addition of anti-IgE monoclonal antibodies (mAbs) to immunotherapy regimens has been studied. Early work with antigen-fixed leukocytes in a murine model has shown promise in inducing tolerance, as have vaccines containing modified recombinant food proteins coadministered with heat-killed Escherichia coli. Nonspecific approaches include a Chinese herbal formulation, anti-IgE mAbs, and Trichuris suis ova therapy. The array of treatment modalities currently being investigated increases the likelihood of finding one or more effective therapies for the treatment of food allergy.

Perspectives on allergen-specific immunotherapy in childhood: an EAACI position statement

This article is the result of consensus reached by a working group of clinical experts in paediatric allergology as well as representatives from an ethical committee and the European Medicine Agency (EMA). The manuscript covers clinical, scientific, regulatory and ethical perspectives on allergen-specific immunotherapy in childhood. Unmet needs are identified. To fill the gaps and to bridge the different points of view, recommendations are made to researchers, to scientific and patient organizations and to regulators and ethical committees. Working together for the benefit of the community is essential. The European Academy of Allergy and Clinical Immunology (EAACI) serves as the platform of such cooperation.

Changes in antigen-specific T-cell number and function during oral desensitization in cow's milk allergy enabled with omalizumab

Food allergy is a major public health problem, for which there is no effective treatment. We examined the immunological changes that occurred in a group of children with significant cow's milk allergy undergoing a novel and rapid high-dose oral desensitization protocol enabled by treatment with omalizumab (anti-immunoglobulin (Ig)E monoclonal antibodies). Within a week of treatment, the CD4(+) T-cell response to milk was nearly eliminated, suggesting anergy in, or deletion of, milk-specific CD4(+) T cells. Over the following 3 months while the subjects remained on high doses of daily oral milk, the CD4(+) T-cell response returned, characterized by a shift from interleukin-4 to interferon-γ production. Desensitization was also associated with reduction in milk-specific IgE and a 15-fold increase in milk-specific IgG4. These studies suggest that high-dose oral allergen desensitization may be associated with deletion of allergen-specific T cells, without the apparent development of allergen-specific Foxp3(+) regulatory T cells.

Peanut sensitization during the first 5 yr of life is associated with elevated levels of peanut-specific IgG

BACKGROUND

  Allergen-specific IgE antibodies are implicated in allergic diseases while allergen-specific IgG antibodies have been proposed to prevent allergic reactions. The objective for this study was to study whether the immune response (IgG and IgG4) to peanut differs in IgE-sensitized and non-sensitized young children.

METHODS

  A total of 239 children have been followed prospectively from birth to 5 yr of age. The levels of IgG and IgG4 to peanut, Ara h 2, and Ara h 8 were analyzed at 2 and 5 yr of age and related to IgE sensitization and peanut consumption.

RESULTS

  The levels of peanut-specific IgG and IgG4 were significantly higher in peanut-sensitized children at 2 and 5 yr of age when compared with non-sensitized children and children sensitized to other food/inhalant allergens. A strong correlation was seen between levels of peanut-specific IgG/IgG4-ratios and peanut-specific IgE at 5 yr of age. Children avoiding peanuts, a subgroup of the peanut sensitized, had statistically significant higher levels of IgE to peanut and a tendency of higher IgG and IgG4 levels to peanut. In the avoidance group, significant correlations between IgE and IgG/IgG4 to peanut were found compared with children eating peanuts.

CONCLUSION

  Peanut-specific IgG or IgG4 levels were elevated in peanut-sensitized children especially those avoiding peanuts. In our study, IgG and IgG4 do not seem to indicate tolerance or protection from sensitization.

Perspectives on immunomodulation early in life

The immune system early in life is characterized by immature activation and function of immune cells and a preponderance of Th2 cytokines. Together with other factors such as genetics and epigenetics, these immature immune responses might prone newborns susceptible to severe infections as well as allergic diseases. Immunomodulation therapy may have potential as therapeutic strategy against those disorders and might have implication in early-life interventions in the future. In this review, we will focus on two immunomodulatory substance classes, Toll-like receptor (TLR) ligands and sphingolipids, which are the focus of extensive research to date. Both TLRs and sphingolipid receptors have a very distinct distribution pattern and function on immune cells. Therefore, they can potentially modulate and balance immune responses, which might be in particular beneficial for the immaturity of the immune response early in life.

One hundred years of allergen immunotherapy European Academy of Allergy and Clinical Immunology celebration: review of unanswered questions

Allergen immunotherapy was introduced by Leonard Noon 100 years ago and is the only disease-modifying treatment for allergic individuals. Improved understanding of immunology has taught us a great deal about the underlying mechanisms involved in allergen immunotherapy; however, despite these developments, a number of important questions remain unanswered. Several of these questions relate to the practice of allergen immunotherapy in the clinic, such as: Is it possible to unify units of allergen potency? Which treatment schedules are best? Is allergen immunotherapy effective in all patient groups? Is there a dose-response relationship for efficacy and safety?, and Is there evidence for long-term effects following allergen immunotherapy? Others are related to new developments, such as new indications, or developments in the production of allergens. On the centenary of Noon's discovery, European experts in the field of immunotherapy met in Geneva under the aegis of the EAACI to discuss these controversial issues. This study presents outcomes and conclusions from these discussions.

FAST: towards safe and effective subcutaneous immunotherapy of persistent life-threatening food allergies

The FAST project (Food Allergy Specific Immunotherapy) aims at the development of safe and effective treatment of food allergies, targeting prevalent, persistent and severe allergy to fish and peach. Classical allergen-specific immunotherapy (SIT), using subcutaneous injections with aqueous food extracts may be effective but has proven to be accompanied by too many anaphylactic side-effects. FAST aims to develop a safe alternative by replacing food extracts with hypoallergenic recombinant major allergens as the active ingredients of SIT. Both severe fish and peach allergy are caused by a single major allergen, parvalbumin (Cyp c 1) and lipid transfer protein (Pru p 3), respectively. Two approaches are being evaluated for achieving hypoallergenicity, i.e. site-directed mutagenesis and chemical modification. The most promising hypoallergens will be produced under GMP conditions. After pre-clinical testing (toxicology testing and efficacy in mouse models), SCIT with alum-absorbed hypoallergens will be evaluated in phase I/II^a and II^b randomized double-blind placebo-controlled (DBPC) clinical trials, with the DBPC food challenge as primary read-out. To understand the underlying immune mechanisms in depth serological and cellular immune analyses will be performed, allowing identification of novel biomarkers for monitoring treatment efficacy. FAST aims at improving the quality of life of food allergic patients by providing a safe and effective treatment that will significantly lower their threshold for fish or peach intake, thereby decreasing their anxiety and dependence on rescue medication.

ICON: food allergy

Food allergies can result in life-threatening reactions and diminish quality of life. In the last several decades, the prevalence of food allergies has increased in several regions throughout the world. Although more than 170 foods have been identified as being potentially allergenic, a minority of these foods cause the majority of reactions, and common food allergens vary between geographic regions. Treatment of food allergy involves strict avoidance of the trigger food. Medications manage symptoms of disease, but currently, there is no cure for food allergy. In light of the increasing burden of allergic diseases, the American Academy of Allergy, Asthma & Immunology; European Academy of Allergy and Clinical Immunology; World Allergy Organization; and American College of Allergy, Asthma & Immunology have come together to increase the communication of information about allergies and asthma at a global level. Within the framework of this collaboration, termed the International Collaboration in Asthma, Allergy and Immunology, a series of consensus documents called International Consensus ON (ICON) are being developed to serve as an important resource and support physicians in managing different allergic diseases. An author group was formed to describe the natural history, prevalence, diagnosis, and treatment of food allergies in the context of the global community.

Immunology in the Clinic Review Series; focus on allergies: basophils as biomarkers for assessing immune modulation

Allergen-specific immunotherapy is an effective clinical treatment for hypersensitivity to many allergens. Studies of basophils during immunotherapy have provided insight into underlying immune mechanisms and support the potential use of basophil activation as a biomarker of clinical outcomes. This review examines the evidence for different pathways of basophil modulation associated with various forms of immunotherapy. Better understanding the molecular mechanisms of basophil activation and desensitization and the relationship between suppression of these effector cells to clinical outcomes holds promise for further development and improvement in potential therapies for allergic diseases.

Immunology in the Clinic Review Series; focus on allergies: immunotherapy for food allergy

There is no approved therapy for food allergy. The current standard of care is elimination of the triggering food from the diet and accessibility to epinephrine. Immunotherapy is a promising treatment approach. While desensitization to most foods seems feasible, it remains unclear if a permanent state of tolerance is achievable. The research team at Duke is pioneering immunotherapy for food allergies. Work here has evolved over time from small open-label pilot studies to larger randomized designs. Our data show that immunological changes associated with immunotherapy include reduction in mast cell reactivity, decreased basophil responses, decreased specific-immunoglobulin (Ig)E, increased IgG4 and induction of regulatory T cells. Immunotherapy has generated much excitement in the food allergy community; however, further studies are needed before it is ready for clinical use.

Food allergy

Food allergy appears to be increasing in prevalence and is estimated to affect >2% and possibly up to 10% of the population. Food allergies are defined by an immune response triggered by food proteins. Emerging data suggest that carbohydrate moieties on food proteins, specifically mammalian meats, may also elicit allergic responses. Food is the most common trigger of anaphylaxis in the community, which can be fatal. The underlying mechanisms of food allergy usually involve food-specific immunoglobulin E antibodies, but cell-mediated disorders account for a variety of chronic or subacute skin and gastrointestinal reactions. Eosinophilic esophagitis is an emerging food-related chronic disorder. The diagnosis of food allergy is complicated by the observation that detection of food-specific immunoglobulin E (sensitization) does not necessarily indicate clinical allergy. Diagnosis requires a careful medical history, laboratory studies, and, in many cases, oral food challenges to confirm a diagnosis. Novel diagnostic methods, many of which rely upon evaluating immune responses to specific food proteins or epitopes, may improve diagnosis and prognosis in the future. Current management relies upon allergen avoidance and preparation to promptly treat severe reactions with epinephrine. Studies suggest that some children with milk or egg allergy might tolerate extensively heated forms, for example milk or egg baked into muffins, without symptoms and possibly with some immunotherapeutic benefits. Novel therapeutic strategies are under study, including oral and sublingual immunotherapy, Chinese herbal medicine, anti-immunoglobulin E antibodies, and modified vaccines.

The safety and efficacy of sublingual and oral immunotherapy for milk allergy

BACKGROUND

Oral immunotherapy (OIT) and sublingual immunotherapy (SLIT) are potential therapies for food allergy, but the optimal method of administration, mechanism of action, and duration of response remain unknown.

OBJECTIVE

We sought to explore the safety and efficacy of OIT and SLIT for the treatment of cow's milk (CM) allergy.

METHODS

We randomized children with CM allergy to SLIT alone or SLIT followed by OIT. After screening double-blind, placebo-controlled food challenges and initial SLIT escalation, subjects either continued SLIT escalation to 7 mg daily or began OIT to either 1000 mg (the OITB group) or 2000 mg (the OITA group) of milk protein. They were challenged with 8 g of milk protein after 12 and 60 weeks of maintenance. If they passed the 60-week challenge, therapy was withdrawn, with challenges repeated 1 and 6 weeks later. Mechanistic correlates included end point titration skin prick testing and measurement of CM-specific IgE and IgG(4) levels, basophil histamine release, constitutive CD63 expression, CD203c expression, and intracellular spleen tyrosine kinase levels.

RESULTS

Thirty subjects with CM allergy aged 6 to 17 years were enrolled. After therapy, 1 of 10 subjects in the SLIT group, 6 of 10 subjects in the SLIT/OITB group, and 8 of 10 subjects in the OITA group passed the 8-g challenge (P = .002, SLIT vs OIT). After avoidance, 6 of 15 subjects (3 of 6 subjects in the OITB group and 3 of 8 subjects in the OITA group) regained reactivity, 2 after only 1 week. Although the overall reaction rate was similar, systemic reactions were more common during OIT than during SLIT. By the end of therapy, titrated CM skin prick test results and CD63 and CD203c expression decreased and CM-specific IgG(4) levels increased in all groups, whereas CM-specific IgE and spontaneous histamine release values decreased in only the OIT group.

CONCLUSION

OIT was more efficacious for desensitization to CM than SLIT alone but was accompanied by more systemic side effects. Clinical desensitization was lost in some cases within 1 week off therapy.

Chinese herbal extracts of Rubia cordifolia and Dianthus superbus suppress IgE production and prevent peanut-induced anaphylaxis

Background

Peanut allergy is characterized by increased levels of peanut-specific IgE in the serum of most patients. Thus, the most logical therapy would be to inhibit the IgE production by committed B-cells. This study aims to investigate the unreported anti-IgE effects of Chinese herbal extracts of Rubia cordifolia (Qiancao) and Dianthus superbus (Qumai).

Methods

Seventy herbal extracts were tested for their ability to reduce IgE secretion by a human B-cell line. Those with the lowest inhibitory concentration 50 (IC₅₀) values were tested in a mouse model of peanut-anaphylaxis. Anaphylactic scores, body temperature, plasma histamine and peanut-specific-immunoglobulins were determined.

Results

Rubia cordifolia and Dianthus superbus inhibited the in vitro IgE production by a human B-cell line in a dose-dependent manner and the in vivo IgE production in a murine model of peanut allergy without affecting peanut-specific-IgG1 levels. After challenge, all mice in the sham groups developed anaphylactic reactions and increased plasma histamine levels. The extract-treated mice demonstrated significantly reduced peanut-triggered anaphylactic reactions and plasma histamine levels.

Conclusion

The extracts of Rubia cordifolia and Dianthus superbus inhibited the IgE production in vivo and in vitro as well as reduced anaphylactic reactions in peanut-allergic mice, suggesting potentials for allergy treatments.

Food allergy: mechanisms and therapeutics

The immunologic mechanisms responsible for the development of allergic sensitization rather than tolerance to foods are not well understood, although there have been a number of recent advances in our understanding of why some foods are inherently allergenic. In addition, the involvement of alternative routes of exposure that are not inherently tolerogenic may play a role in sensitization to foods. Although there are no currently accepted therapeutic approaches to food allergy, there are a number of approaches to treatment in preclinical or clinical trials. Here, we review selected findings published since 2009 that advance our understanding of mechanisms and new therapeutics for IgE-mediated food allergy.

Oral desensitization for food hypersensitivity

Food allergy has become an increasingly prevalent international health problem. Allergic reactions can result in life-threatening anaphylaxis in a short period of time, so the current standard of care dictates strict avoidance of suspected trigger foods and accessibility to injectable epinephrine. Intervention at the time of exposure is considered a rescue therapy rather than a disease-modifying treatment. Investigators have been studying allergen immunotherapy to promote induction of oral tolerance. This article examines the mechanisms of oral tolerance and the breakdown that leads to food allergy, as well as the history and current state of oral and sublingual immunotherapy development.

Future therapies for food allergies

Food allergy is an increasingly prevalent problem in westernized countries, and there is an unmet medical need for an effective form of therapy. A number of therapeutic strategies are under investigation targeting foods that most frequently provoke severe IgE-mediated anaphylactic reactions (peanut, tree nuts, and shellfish) or are most common in children, such as cow's milk and hen's egg. Approaches being pursued are both food allergen specific and nonspecific. Allergen-specific approaches include oral, sublingual, and epicutaneous immunotherapy (desensitization) with native food allergens and mutated recombinant proteins, which have decreased IgE-binding activity, coadministered within heat-killed Escherichia coli to generate maximum immune response. Diets containing extensively heated (baked) milk and egg represent an alternative approach to food oral immunotherapy and are already changing the paradigm of strict dietary avoidance for patients with food allergy. Nonspecific approaches include monoclonal anti-IgE antibodies, which might increase the threshold dose for food allergen in patients with food allergy, and a Chinese herbal formulation, which prevented peanut-induced anaphylaxis in a murine model and is currently being investigated in clinical trials. The variety of strategies for treating food allergy increases the likelihood of success and gives hope that accomplishing an effective therapy for food allergy is within reach.