Novel approaches for the treatment of food allergy

Efficacy of baked milk oral immunotherapy in baked milk-reactive allergic patients

BACKGROUND

Patients with IgE-mediated cow's milk allergy who are nonreactive to baked milk (BM) can be desensitized with BM to promote tolerance to unheated milk (UM).

OBJECTIVE

We sought to test whether patients who are BM reactive can progress in BM oral immunotherapy (OIT) and become desensitized to UM as well.

METHODS

Fifteen patients (>4 years) who previously failed to complete our milk OIT program were enrolled into the BM OIT protocol. A dose of BM (180 °C for 30 minutes) which was less than the eliciting dose was increased 50% monthly while under medical supervision until the primary outcome dose of 1.3 g/d BM protein was achieved. Basophil reactivity and milk protein-specific IgE binding were analyzed at the first round of BM OIT therapy (T0) and at 12 months of BM treatment.

RESULTS

In terms of the primary outcome, only 3 (21%) of 14 patients tolerated the 1.3 g/d BM dose. Although some patients initially progressed in BM OIT, 8 of 11 failed because of IgE-mediated reactions. Three did not complete the program because of non-IgE-mediated factors. An increase in challenge threshold to UM was noted in patients continuing until 12 months (P = .003), including those among whom reactions precluded continuation in the program. Patients (n = 3) who successfully reached maintenance had decreased milk-specific IgE reactivity. Furthermore, the mean difference at T0 between induced HM and UM percentages of CD203c expression was significantly lower in patients who successfully completed BM OIT than in those who did not (-11% vs 4.4%, P = .0002), which is consistent with their decreased clinical reactivity to BM.

CONCLUSIONS

Although use of hypoallergenic BM in OIT is a promising therapy, care must be taken before its administration in BM-reactive patients because of the risk for anaphylaxis and only limited increase in challenge threshold attained.

Specific immunotherapy for food allergy: basic principles and clinical aspects

PURPOSE OF REVIEW

Food allergy may be life threatening and its management continues to consist of avoiding relevant allergens and, in the case of accidental ingestion, initiation of appropriate emergency therapy. The aim of this article is to describe current treatment approaches and discuss attempts to use specific immunotherapy for food-allergy treatment.

RECENT FINDINGS

A recent study reports the use of sublingual immunotherapy for hazelnut food allergy in hazelnut-allergic patients. A significant increase in tolerance to hazelnuts after sublingual immunotherapy as assessed by double-blind, placebo-controlled food challenge, and good tolerance to this treatment, have been observed.

SUMMARY

The purpose of this review is to highlight the most promising novel approaches for treating food allergy beyond allergen avoidance. Some of these approaches alone, such as traditional Chinese herbal medicine, anti-immunoglobulin E therapy or sublingual immunotherapy for food allergy, or the combination of different approaches, would probably offer the best treatment option for food-allergic patients in the near future.

Towards immunotherapy for peanut allergy

PURPOSE OF REVIEW

Food allergy is a major cause of life-threatening hypersensitivity reactions. Peanut allergy is the most serious of the hypersensitivity reactions to foods due to its persistence and high risk of severe anaphylaxis. Currently, strict avoidance of the allergenic food and ready access to self-injectable epinephrine is the 'standard of care' for food allergy. Based on extensive characterization of food allergens and a better understanding of the immunological mechanisms underlying allergic disease, promising therapeutic modalities for food allergy treatment and prevention are being developed.

RECENT FINDINGS

Immunotherapeutic strategies include peptide immunotherapy, mutated protein immunotherapy and DNA immunization, which all strive to decrease the deleterious Th2 response. Another approach already in clinical trials for peanut allergy is the anti-IgE therapy which prevents circulating IgE from binding to effector cells, consequently decreasing clinical symptoms after peanut ingestion. In order to be applicable, these strategies must be well tolerated, inexpensive and easily administered. Realistic treatment options would likely involve a combination of different approaches.

SUMMARY

Food allergy affects approximately 4-6% of children and 3-4% of adults. Peanut allergy can be devastating as reactions range from urticaria to severe anaphylactic shock and death. The only preventive measure for peanut allergy is strict avoidance of the incriminating food. It is likely immunotherapy will be available in the near future as a well tolerated and effective therapy for treating peanut allergy. The use of the anti-IgE therapy in conjunction with other immunotherapy would possibly be the best treatment option in the future.

Functional gastrointestinal disorders and mast cells: implications for therapy

The pathophysiology of functional gastrointestinal disorders is poorly understood. Accepted common mechanisms include psychosocial factors, abnormal gastrointestinal motility and disturbed visceral sensory perception, but the underlying causes remain unclear. Mast cells (MCs) are immunocytes widely distributed throughout the gastrointestinal tract. Several stimuli (e.g. allergens, neuropeptides and stress) lead to MC activation with consequent mediator release (e.g. histamine, tryptase and prostanoids). The MC mediators interact with nerves supplying the gut leading to altered gut physiology and increased sensory perception. The intestinal mucosa of irritable bowel syndrome patients contains on average an increased number of MCs. These cells release an increased amount of mediators in close vicinity to mucosal innervation. The MC activation and their close proximity to nerve fibres is correlated with the severity of perceived abdominal painful sensations. These data provide a strong basis for considering MCs as important participants in visceral hypersensitivity and pain perception in irritable bowel syndrome. Inhibition of MC function may ameliorate irritable bowel symptoms. Novel drugs with an increased potential in the control of MC function (e.g., anti-IgE antibodies, the intracellular protein tyrosine kinase inhibitor Syk) and mediator release (e.g., second generation antihistamines, proteinase-activated receptor antagonists) may be useful pharmacological tools for these common disorders.

Beyond allergen avoidance: update on developing therapies for peanut allergy

PURPOSE OF REVIEW

Food allergy has emerged as a significant health problem. Peanut allergy is a major cause of food-induced fatal and near fatal anaphylactic reactions, and the incidence in children is increasing. Attempts to manage peanut allergy by strict avoidance are often unsuccessful. The purpose of this review is to highlight the most promising novel approaches for treating peanut allergy beyond allergen avoidance.

RECENT FINDINGS

In the past 5 years much effort has been devoted to developing a treatment for peanut allergy. A recent clinical trial showed that monthly injections of humanized recombinant anti-IgE antibodies increased the threshold for allergic responses of peanut-sensitive individuals, at least to small amounts of peanut protein. However, this treatment cannot cure peanut allergy, and continuous monthly injections are necessary to maintain protection. Developing new therapies for the treatment of peanut allergy is essential. In reviewing publications between 2003 and 2005, several novel therapeutic approaches, tested in the murine model of peanut anaphylaxis appeared promising. Immunotherapy with engineered recombinant peanut protein and bacterial adjuvant significantly protected peanut allergic mice from anaphylaxis. It was also found that a Chinese herbal medicine formula called Food Allergy Herbal Formula-2 completely blocked anaphylaxis up to 5 weeks following therapy. These potent therapeutic effects are associated with immunoregulation of Th1 and Th2 responses.

SUMMARY

Although there is no effective and safe therapy for food allergy, many novel approaches are under investigation. Some of these approaches may provide allergists with effective treatments in the near future.

Intradermal exposure of BALB/c strain mice to peanut protein elicits a type 2 cytokine response

There is a growing need for the development of methods to characterize the allergenic properties of novel proteins, particularly those expressed by transgenic crop plants. Hence, there is considerable interest in the development of suitable animal models for this purpose. The production of specific IgE antibody has been reported following sensitization with food allergen via oral or systemic (intraperitoneal) routes of exposure. We have characterized cytokine profiles induced by intradermal treatment of BALB/c strain mice with a purified peanut allergen, Arachis hypogea lectin. Mice were exposed to peanut lectin by intradermal administration and the cytokine responses in the lymph node draining the site of exposure analyzed at the secreted protein level by enyzme-linked immunosorbent assay (ELISA) and cytokine mRNA level by ribonuclease protection assay (RPA). Exposure to peanut lectin, under conditions that induced robust IgE antibody titers, was found to be associated with a T helper 2 (Th2)-type cytokine expression profile at both the mRNA and secreted protein levels. Culture of naïve lymph node cells with peanut lectin failed to stimulate marked proliferation or cytokine production, confirming this protein is not mitogenic for mouse lymphocytes. Furthermore, the expression of Th2 cytokines was associated with the effector/memory CD62L- cell population. Similar treatment with a non-allergenic protein, potato acid phosphatase, failed to induce Th2 cytokine expression. These data demonstrate that exposure of mice to peanut allergen results in the selective stimulation of a Th2-type response.

Food allergy: what do we learn from animal models?

PURPOSE OF REVIEW

This review summarizes selected articles on animal models of food allergy published in 2003. The research areas that are covered include mechanistic studies, the search for new therapies, as well as screening models for hazard identification of potential allergens.

RECENT FINDINGS

Novel treatment options of both prevention and therapeutic strategies have been reported with promising results. The induction of de-sensitization to food proteins was achieved by exposure to a mixture of recombinant food allergens and T helper 1 (Th1)-skewing bacterial components. Furthermore, research in animal models has provided new insights into the role of protein structure, digestion, and gut permeability in sensitization and tolerance induction to food proteins. The Th2 hypothesis of food allergy was tested in mouse strains, linking genetic susceptibility to sensitization with differential Th1-Th2 responses. In this context, the role of the liver in development of food antigen-specific Th2 cells, and the importance of costimulatory molecules in Th2 skewing were demonstrated. Finally, rodent models to predict potential allergenicity of novel foods have been further developed using different routes of sensitization.

SUMMARY

Currently, several animal models of food allergy are used, including mouse, rat, swine, and dog. Continuing research in these models may elucidate the immunological mechanisms that underlie the sensitization and challenge phase of food allergy and may result in improved therapeutic options. Furthermore, the development of animal models to predict relative allergenicity of novel foods remains an important topic.

Mutational analysis of major, sequential IgE-binding epitopes in alpha s1-casein, a major cow's milk allergen

BACKGROUND

Allergy to cow's milk is common in early childhood, and no therapy other than avoidance exists. In murine models of peanut allergy, immunotherapy with mutated, engineered, proteins appears promising.

OBJECTIVE

We sought to identify the critical amino acids (AAs) for immunoglobulin E (IgE) binding within the major B-cell epitopes of alpha(s1)-casein, a major cow's milk allergen. This will provide the necessary information to alter the cDNA to encode a protein capable of activating milk-specific T cells, but with reduced IgE-binding capacity.

METHODS

For mutational analysis of the IgE-binding epitopes, peptides of 10-14 AAs in length were synthesized on a derivatized cellulose membrane with single or multiple AA substitutions. Membranes were immunolabeled with pooled sera from 15 cow's-milk-allergic patients and with 8 individual sera.

RESULTS

With the pooled sera, substitution of a single AA led to complete abrogation of IgE binding to 2 of 8 peptides and diminished binding in the remainder. Substitution of multiple AAs led to an abrogation of binding in the remaining peptides. In 4 of the 8 peptides, the critical AA identified with pooled sera did not result in significant reduction of IgE binding with 1 or more individual patients. For these patients, other critical AAs were identified, indicating a more heterogeneous pattern in IgE recognition.

CONCLUSION

This study indicates that single or multiple AA substitutions within IgE-binding epitopes result in reduced binding of milk-specific IgE antibodies by patients' sera. However, for future immunotherapeutic interventions with mutated peptides, critical AAs should be evaluated with individual patient sera to determine B-cell-epitope heterogeneity.

Management of food allergies

Worldwide, approximately 8 and 2% of children and adults, respectively, suffer from food allergy. Cow's milk, egg, peanut, soy, wheat, fish, shellfish and tree nuts are responsible for the majority of allergic reactions to foods. Allergic reactions to food can occur by a variety of immune mechanisms including: IgE-mediated; non-IgE-mediated (T-cell-mediated); and combined IgE- and T-cell-mediated. Food allergies can affect any organ system, but most frequently involve the gastrointestinal system, the skin and the respiratory system. Knowledge of the spectrum of food allergies is important in order to identify patients at risk for severe or life-threatening allergic reactions. This article will review the mechanisms of specific food allergy disorders. It will also summarise the diagnosis of food allergy including the history of a food reaction, skin tests and laboratory tests. The management of food allergy will also be discussed with particular emphasis on the avoidance of food allergens and the pharmacotherapy of allergic reactions. Future therapy for food allergies will also be discussed.

Persistent protective effect of heat-killed Escherichia coli producing "engineered," recombinant peanut proteins in a murine model of peanut allergy

BACKGROUND

Peanut allergy (PNA) is a life-threatening food allergy for which there is no definitive treatment.

OBJECTIVE

We investigated the long-term immunomodulatory effect of heat-killed Escherichia coli producing engineered (mutated) Ara h1, 2, and 3 (HKE-MP123) administered rectally (pr) in a murine model of PNA.

METHODS

Peanut-allergic C3H/HeJ mice received 0.9 (low dose), 9 (medium dose), or 90 (high dose) microg HKE-MP123 pr, HKE-containing vector (HKE-V) alone, or vehicle alone (sham) weekly for 3 weeks. Mice were challenged 2 weeks later. A second and third challenge were performed at 4-week intervals.

RESULTS

After the first challenge, all 3 HKE-MP123 and HKE-V-treated groups exhibited reduced symptom scores (P <.01,.01,.05,.05, respectively) compared with the sham-treated group. Interestingly, only the medium- and high-dose HKE-MP123-treated mice remained protected for up to 10 weeks after treatment accompanied by a significant reduction of plasma histamine levels compared with sham-treated mice (P <.05 and.01, respectively). IgE levels were significantly lower in all HKE-MP123-treated groups (P <.001), being most reduced in the high-dose HKE-MP123-treated group at the time of each challenge. IL-4, IL-13, IL-5, and IL-10 production by splenocytes of high-dose HKE-MP123-treated mice were significantly decreased (P <.01;.001,.001, and.001, respectively), and IFN-gamma and TGF-beta production were significantly increased (P <.001 and.01, respectively) compared with sham-treated mice at the time of the last challenge.

CONCLUSIONS

Treatment with pr HKE-MP123 can induce long-term "downregulation" of peanut hypersensitivity, which might be secondary to decreased antigen-specific T(H)2 and increased T(H)1 and T regulatory cytokine production.

Therapeutic modalities for cow's milk allergy

OBJECTIVE

To discuss current therapeutic modalities for cow's milk allergy and its prevention.

DATA SOURCES AND STUDY SELECTION

The sources of data include original clinical studies carried out at Ste. Justine Hospital, as well as a systematic search of the published English and French language scientific literature restricted to human subjects using computerized searches (National Public Library of Medicine, Cochrane Database Systems Review) from 1997 to 2002. Search terms for article retrieval included food allergy, milk allergy, therapy, and prevention.

CONCLUSIONS

The therapy of food allergies depends upon an accurate diagnosis, which remains a challenge in non--IgE-mediated cases. Dietary exclusion remains the mainstay of therapy, with medications reserved for exceptional patients. Preliminary evidence suggests that pancreatic enzyme supplementation may be of benefit for cases with multiple food allergies and severe eczema. Hydrolysate formula use is currently recommended for dietary allergy prevention in infants at an increased risk when maternal milk is insufficient or unavailable. The use of partially hydrolyzed formulas to prevent allergic disorders, including atopic dermatitis, is supported by clinical studies, but cannot be used in the already sensitized, milk-allergic child. Probiotics show enormous potential in preventing food allergic disorders as well.

Advances in anaphylaxis and hypersensitivity reactions to foods, drugs, and insect venom

This review highlights some of the research advances in anaphylaxis and hypersensitivity reactions to foods, drugs, and insect venom that were reported primarily in this Journal from 2001 to 2002. Among the topics highlighted: Epinephrine injected intramuscularly into the thigh provides the most efficient absorption profile for adults and children; determination of serum IgE antibody-specific food allergen concentrations and atopy patch tests with foods show promise for enhanced diagnostic accuracy; numerous food allergens are now characterized on the molecular level, allowing for improved diagnostic and treatment modalities; the complex immunologic mechanisms underlying drug hypersensitivity reactions are being elucidated; venom immunotherapy improves quality of life for sufferers, and increased venom immunotherapy doses are useful in recalcitrant cases.

Food allergies

Adverse reactions to foods are commonly implicated in the causation of ill health. However, foreign antigens, including food proteins and commensal microbes encountered in the gastrointestinal tract, are usually well tolerated. True food allergies, implying immune-mediated adverse responses to food antigens, do exist, however, and are especially common in infants and young children. Allergic reactions to food manifest clinically in a variety of presentations involving the gastrointestinal, cutaneous, and respiratory systems and in generalized reactions such as anaphylaxis. Both IgE-mediated and non-IgE-mediated immune mechanisms are recognized. Important advances in the clinical features underlying specific food hypersensitivity disorders are reviewed.