L. Pons

Clinical efficacy and immune regulation with peanut oral immunotherapy

BACKGROUND Oral immunotherapy (OIT) has been thought to induce clinical desensitization to allergenic foods, but trials coupling the clinical response and immunologic effects of peanut OIT have not been reported. OBJECTIVE The study objective was to investigate the clinical efficacy and immunologic changes associated with OIT. METHODS Children with peanut allergy underwent an OIT protocol including initial day escalation, buildup, and maintenance phases, and then oral food challenge. Clinical response and immunologic changes were evaluated. RESULTS Of 29 subjects who completed the protocol, 27 ingested 3.9 g peanut protein during food challenge. Most symptoms noted during OIT resolved spontaneously or with antihistamines. By 6 months, titrated skin prick tests and activation of basophils significantly declined. Peanut-specific IgE decreased by 12 to 18 months, whereas IgG(4) increased significantly. Serum factors inhibited IgE-peanut complex formation in an IgE-facilitated allergen binding assay. Secretion of IL-10, IL-5, IFN-gamma, and TNF-alpha from PBMCs increased over a period of 6 to 12 months. Peanut-specific forkhead box protein 3 T cells increased until 12 months and decreased thereafter. In addition, T-cell microarrays showed downregulation of genes in apoptotic pathways. CONCLUSION Oral immunotherapy induces clinical desensitization to peanut, with significant longer-term humoral and cellular changes. Microarray data suggest a novel role for apoptosis in OIT.

A randomized controlled study of peanut oral immunotherapy: Clinical desensitization and modulation of the allergic response

BACKGROUND Open-label oral immunotherapy (OIT) protocols have been used to treat small numbers of patients with peanut allergy. Peanut OIT has not been evaluated in double-blind, placebo-controlled trials. OBJECTIVE To investigate the safety and effectiveness of OIT for peanut allergy in a double-blind, placebo-controlled study. METHODS In this multicenter study, children ages 1 to 16 years with peanut allergy received OIT with peanut flour or placebo. Initial escalation, build-up, and maintenance phases were followed by an oral food challenge (OFC) at approximately 1 year. Titrated skin prick tests (SPTs) and laboratory studies were performed at regular intervals. RESULTS Twenty-eight subjects were enrolled in the study. Three peanut OIT subjects withdrew early in the study because of allergic side effects. During the double-blind, placebo-controlled food challenge, all remaining peanut OIT subjects (n = 16) ingested the maximum cumulative dose of 5000 mg (approximately 20 peanuts), whereas placebo subjects (n = 9) ingested a median cumulative dose of 280 mg (range, 0-1900 mg; P < .001). In contrast with the placebo group, the peanut OIT group showed reductions in SPT size (P < .001), IL-5 (P = .01), and IL-13 (P = .02) and increases in peanut-specific IgG(4) (P < .001). Peanut OIT subjects had initial increases in peanut-specific IgE (P < .01) but did not show significant change from baseline by the time of OFC. The ratio of forkhead box protein 3 (FoxP3)(hi): FoxP3(intermediate) CD4+ CD25+ T cells increased at the time of OFC (P = .04) in peanut OIT subjects. CONCLUSION These results conclusively demonstrate that peanut OIT induces desensitization and concurrent immune modulation. The current study continues and is evaluating the hypothesis that peanut OIT causes long-term immune tolerance.

Protein Structure Plays a Critical Role in Peanut Allergen Stability and May Determine Immunodominant IgE-Binding Epitopes

Hypersensitivity to peanuts is a reaction mediated by IgE Abs in response to several peanut protein allergens. Among these allergenic proteins, Ara h 2 is one of the most commonly recognized allergens. Ara h 2 is a 17-kDa protein that has eight cysteine residues that could form up to four disulfide bonds. Circular dichroism studies showed substantial changes in the secondary and tertiary structures of the reduced Ara h 2 as compared with the native protein. Upon treatment with trypsin, chymotrypsin, or pepsin, a number of relatively large fragments are produced that are resistant to further enzymatic digestion. These resistant Ara h 2 peptide fragments contain intact IgE-binding epitopes and several potential enzyme cut sites that are protected from the enzymes by the compact structure of the protein. The enzyme-treated allergen remains essentially intact despite the action of proteases until the fragments are dissociated when the disulfide linkages are reduced. Amino acid sequence analysis of the resistant protein fragments indicates that they contain most of the immunodominant IgE-binding eptiopes. These results provide a link between allergen structure and the immunodominant IgE-binding epitopes within a population of food-allergic individuals.

Individualized IgE-based dosing of egg oral immunotherapy and the development of tolerance

BACKGROUND Hens egg allergy is among the most common food allergies in childhood and predicts later development of allergic disease. The optimal efficacy and mechanism(s) of egg allergen immunotherapy are poorly understood. OBJECTIVE To enhance immunologic and clinical outcomes of egg oral immunotherapy (OIT) using a conditionally increased dosing strategy. METHODS In an open-label clinical trial of egg OIT, egg-allergic children ingested daily doses of egg protein that were gradually increased based on the egg white (EW) IgE level. Skin prick test reactivity and EW- and ovomucoid-specific cellular and humoral responses were measured longitudinally. To confirm clinical tolerance, patients underwent double-blinded, placebo-controlled food challenges 1 month after completing the dosing protocol. RESULTS Children aged 3 to 13 years with characteristics of clinical egg allergy were enrolled. All 6 patients who completed the entire protocol developed clinical tolerance to egg during the study. The median wheal diameter on EW skin prick testing decreased from 10 to 2.5 mm during OIT (P = .03). Both EW and ovomucoid IgE levels significantly decreased during the study (median EW IgE level: from 18.8 kU/L at baseline to 3.9 kU/L, P = .03), and corresponding IgG4 levels increased (median EW IgG4 level: from 0.65 mg/L at baseline to 86.15 mg/L, P = .03). Transient increases were seen in egg-induced interleukin 10 (P = .06) and transforming growth factor β (P = .18) levels, and the ratio of T(H)2:T(H)1 cytokine production was decreased (P = .25). CONCLUSIONS Egg OIT is associated with tolerance acquisition in children with persistent egg allergy. Individualized dosing regimens may be necessary to achieve a full therapeutic effect in some patients.

Evidence of pathway‐specific basophil anergy induced by peanut oral immunotherapy in peanut‐allergic children

In Westernized countries, over 1% of the population is allergic to peanuts or tree nuts, which carries a risk of severe allergic reactions. Several studies support the efficacy of peanut oral immunotherapy (OIT) for reducing the clinical sensitivity of affected individuals; however, the mechanisms of this effect are still being characterized. One mechanism that may contribute is the suppression of effector cells, such as basophils. Basophil anergy has been characterized in vitro as a pathway‐specific hyporesponsiveness; however, this has not been demonstrated to occur in vivo.

Contribution of Ara h 2 to peanut-specific, immunoglobulin E-mediated, cell activation.

Background Ara h 2 is a potent peanut allergen but its contribution to the ability of a crude peanut extract (CPE) to cross‐link IgE and activate mast cells has not been rigorously evaluated.

Serological and clinical characteristics of children with peanut sensitization in an Asian community.

Chiang WC, Pons L, Kidon MI, Liew WK, Goh A, Wesley Burks A. Serological and clinical characteristics of children with peanut sensitization in an Asian community.
Pediatr Allergy Immunol 2010: 21: e429–e438.
© 2009 John Wiley & Sons A/S

In vivo and T Cell Cross-Reactivity between Walnut, Cashew and Peanut

Background: Examination of IgE cross-reactivity among nuts has been limited to in vitro experiments. Cross-reactivity studies of nuts at the T cell level are difficult to interpret because of the inability to determine which cellular responses are from a true sensitization and which are due to cross-reactivity. Using a mouse model in which the sensitizing nuts are controlled may provide novel methods to investigate in vivo and T cell cross-reactivity. Methods: C3H/HeJ mice were sensitized by intraperitoneal injection of cashew alone (monosensitized mice), or cashew plus walnut, utilizing alum as an adjuvant. Both groups underwent challenges to cashew, walnut and peanut, with subsequent monitoring of anaphylactic reactions. Anaphylactic antibodies were quantified by ELISA, and protein allergens were identified by Western blotting. Cellular responses were studied via splenocyte proliferation assay and measurement of secreted cytokines. Results: The monosensitized mice reacted to cashew and walnut during challenges, with significantly weaker reactions induced on challenge with peanut. Cross-reactive IgE to walnut and peanut were detected by ELISA, and the cross-reactive allergens were identified as vicilin proteins. In cellular assays, splenocytes from the monosensitized mice proliferated and produced IL-4 and IL-5 in response to cashew, walnut and peanut. The cashew- plus walnut-sensitized mice experienced stronger clinical reactions to walnut, recognized additional walnut allergens and secreted significantly more IL-4 and IL-5 in walnut-stimulated splenocyte assays compared to the monosensitized mice. Conclusions: Cross-reactivity in vivo was found between cashew and walnut, while cross-reactivity among cashew, walnut and peanut was demonstrated at the T cell level.

Single–tree nut immunotherapy attenuates allergic reactions in mice with hypersensitivity to multiple tree nuts

BACKGROUND Allergic reactions to tree nuts are often severe and are outgrown in less than 10% of diagnosed patients. OBJECTIVES To determine whether treatment of underlying tree nut sensitization will prevent allergic reactions to cross-reacting tree nuts and to determine the effects of single-tree nut immunotherapy on true multi-tree nut sensitization. METHODS Cross-reactivity model: Cashew-sensitized mice underwent immunotherapy with cashew and were subsequently challenged with cashew and pistachio. Multisensitization model: Cashew plus walnut-sensitized mice were treated with cashew alone, walnut alone, or both cashew and walnut and then underwent challenges to cashew and walnut. Challenges were assessed on the basis of symptoms, changes in body temperature, and mouse mast cell protease-1 release. RESULTS In the cross-reactivity model, cashew immunotherapy completely prevented allergic reactions on challenges with cashew or the cross-reactive pistachio. In the multisensitization model, mice with cashew plus walnut allergy were significantly protected from anaphylactic reactions on cashew challenge in both the cashew-alone and walnut-alone immunotherapy groups. Results from the walnut challenge demonstrated significantly decreased allergic responses in the walnut immunotherapy group, whereas mice in the cashew immunotherapy group experienced significantly lower symptoms. In the cross-reactivity model, immunotherapy effectively decreased IL-4 and IL-5 production and increased IL-12 relative to placebo while also inducing a 5-fold increase in specific IgG(1). CONCLUSION Single-tree nut immunotherapy can effectively decrease allergic responses in both the cross-reactivity and multisensitization mouse models. Further studies are needed to determine which single-tree nut immunotherapies will be most effective for specific multi-tree nut allergy profiles.

IgG and IgE avidity characteristics of peanut allergic individuals

The role of antibody avidity in allergy is poorly understood and there is no existing literature describing antibody avidity in food allergy. The main aim of this study was to investigate IgE and IgG avidity to a total peanut protein extract (TPPE) and purified Ara h 2 in a group of well‐characterized peanut allergic individuals. Forty peanut allergic patients underwent a double‐blind placebo‐controlled low‐dose peanut challenge, during which the severity of the patients’ peanut allergy was scored. Serum peanut‐specific IgE (psIgE) and IgG (psIgG) concentrations were measured for 37 individuals and the avidities of the same antibodies to a TPPE and purified Ara h 2 were determined using a thiocyanate ELISA method. Both IgE and IgG avidity to Ara h 2 showed weak positive correlations with challenge score [r = 0.459 (p = 0.012) and r = 0.486 (p = 0.003), respectively]. IgE avidity to TPPE showed a weak positive correlation with skin prick test results (SPT), r = 0.467 (p = 0.004) and there was an inverse relationship between the ratio of total IgE:psIgE and challenge score r = −0.561 (p < 0.001). No significant relationship was found between the ratios of IgE avidity:IgG avidity and challenge score or SPT. This is the first description of IgE and IgG avidity in peanut allergy, and it appears that the avidities of IgE and IgG antibodies to purified Ara h 2 are weakly related to the severity of peanut allergy (as measured by a challenge score).