The diagnostic value of hazelnut allergy tests in double‐blind challenged children is largely unknown. The aim of this study was to analyze the performance of current diagnostic tests for hazelnut allergy in children and the effect of spiking.

SummaryBackground T cell responses involved in peanut allergy are poorly understood.Objective To investigate T cell responses towards major peanut allergens in peanut‐allergic (PA) subjects compared with peanut‐sensitized (PS) non‐allergic children and non‐atopic (NA) controls.Methods Eighteen PA children, seven non‐allergic PS children and 11 NA adults were included. Peripheral blood mononuclear cells were stimulated with a crude peanut extract (CPE). Short‐term T cell lines were generated and subsequently stimulated with CPE and purified Ara h 1, Ara h 2, Ara h 3 and Ara h 6. The proliferation and production of IL‐13, IFN‐γ, IL‐10 and TNF‐α were analysed.Results Proliferation to CPE and major allergens was enhanced in PA subjects. The primary response to CPE was comparable with PS subjects, with increased production of IL‐13 and IFN‐γ compared with NA. Production of IL‐10 was not observed. In short‐term T cell lines, the response to CPE was stronger in PA than in PS and NA subjects. Only PA children had a detectable response to major peanut allergens, characterized by IL‐13 production. The response was the highest after Ara h 3 stimulation, and the lowest after Ara h 2 stimulation. No significant correlation was observed between peanut‐specific IgE levels and T cell responses to CPE.Conclusion T cell responses to CPE in PA and PS children were characterized by Th1 and Th2 cytokines. Only PA children showed enhanced Th2 responses to Ara h 1, Ara h 3 and Ara h 6. Cite this as: A. E. Flinterman, S. G. M. A. Pasmans, C. F. den Hartog Jager, M. O. Hoekstra, C. A. F. M. Bruijnzeel‐Koomen, E. F. Knol and E. van Hoffen, Clinical & Experimental Allergy, 2010 (40) 590–597.

Summary Background In peanut‐allergic adults, IgE is mainly directed to Ara h1 and Ara h2. More recently, a role for Ara h6 has been suggested. In contrast to adults, IgE in children can fluctuate over time. Therefore, children may have a more dynamic reactivity to peanut. Objective To examine the IgE reactivity to major peanut allergens in peanut‐allergic children at two subsequent time‐points. Methods Twenty children (3–15 years old) with peanut allergy, confirmed by a double‐blind placebo‐controlled food challenge (DBPCFC), were included. Just before and 20 months after DBPCFC, IgE reactivity to purified Ara h1, Ara h2, Ara h3 and Ara h6 was studied by immunoblots and skin prick tests (SPTs). Results Before DBPCFC, all peanut‐allergic children showed IgE reactivity to Ara h2; Ara h6 was recognized by 16 children, and Ara h1 and Ara h3 by 10 children. After 20 months, peanut‐specific IgE levels (median 23 kU/L) and the individual recognition of major allergens were comparable with the levels and recognition before challenge (median 28.2 kU/L). SPT with Ara h2 and Ara h6 was positive in most children, whereas SPT with Ara h1 and Ara h3 was positive in approximately half of the children. Ara h6 induced the largest weals. None of the parameters were related to the severity of peanut allergy. Conclusion Ara h2 and Ara h6 are the most frequently recognized major peanut allergens in children. The individual reactivity to the major peanut allergens remained stable over time, despite DBPCFC.

Background: Previous studies suggest that administration of probiotics in vitro can stimulate regulatory and Th1 immune responses. We studied both the in vitro immunological effects of probiotics and the ex vivo immunological effects after oral administration of probiotics in children with food allergy, a Th2-mediated disease. Methods: Thirteen children were enrolled. Probiotics (n = 7) or placebo (n = 6) were orally administered during 3 months. At baseline and after 1 and 3 months, peripheral blood mononuclear cells were stimulated with crude peanut extract, anti-CD3, or anti-CD40 and IL-4 in the presence (in vitro response) or absence (ex vivo response) of probiotics. The proliferation and production of IFN-γ, IL-5, IL-13, IL-10, TNF-α, IL-6 and IgE were analyzed. Sensitization to peanut, cow’s milk and hen’s egg was determined before and after treatment. Results: The in vitro addition of probiotics to peripheral blood mononuclear cell cultures resulted in enhanced proliferation and production of IFN-γ, IL-10 and TNF-α. After oral treatment, proliferation in the presence of probiotics increased, whereas in vitro IgE production decreased in the probiotics group compared to baseline. The ex vivo production of IL-10, TNF-α and IL-6 tended to decrease. Th1 and Th2 cytokines were not altered. Sensitization remained unchanged. Conclusion: Probiotics enhanced the production of Th1 and regulatory cytokines in vitro. Oral administration of probiotics resulted in a slightly decreased ex vivo production of IL-10, TNF-α and IL-6. This indicates that probiotics have a different potential to modulate the immune response in vitro versus ex vivo.

RATIONALE: Although hazelnut allergy is usually related to birch pollen allergy and limited to mild oral allergy, in particular children also report more serious reactions. In areas without birches, sensitization to lipid transfer protein (LTP) in hazelnut, Cor a 8, has been observed in subjects with severe reactions. Children from a birch-endemic area might develop sensitization to LTP at a young age independent from birch pollen. METHODS: Specific IgE to purified Cor a 1, Cor a 8, and Bet v 1 was determined in sera of 217 Dutch children aged 0-17 years. Twenty-six of these children also underwent a DBPCFC. RESULTS: In 217 hazelnut-sensitized children, sensitization to Cor a 1 was observed in 62.7%, to Cor a 8 in 31.3%, and to Bet v 1 in 55.0%. Sensitization to Cor a 8 was predominantly present at early ages, whereas sensitization to Cor a 1 and Bet v 1 was correlated with increasing age (r=0.630 and r=0.503, respectively). Children with objective reactions during DBPCFC (n=8) were all sensitized to Cor a 8 (0.51 - 23.3 kU/l), compared to only one child (1/18) without objective reactions (0.90 kU/l). Levels of IgE to Cor a 8 and Cor a 1, but not to Bet v 1, were significantly higher in the group with objective reactions. CONCLUSIONS: This is the first report of a substantial presence of LTP sensitization in children from a birch-endemic area, associated with serious reactions to hazelnut. The route of sensitization to LTP remains to be elucidated, but seems independent from birch pollen.

In this thesis the term allergy is used to denote reactions that are mediated by the antibody IgE. Such allergic reactions usually take place within half an hour after ingestion and may include itching of the mouth, swelling of the throat, hives, swelling of the face, stomach ache, vomiting, diarrhea, hay fever symptoms, obstructed breathing, and shock. In patients who develop allergic symptoms after eating certain foods, IgE specific for the offending food can be observed, which is called sensitization. Sensitization to hazelnut and peanut is common during childhood, especially in children with eczema. However, children who do not have symptoms after eating hazelnut or peanut may also be sensitized. On the other hand, young children who have never eaten hazelnut or peanut still may have become sensitized. A challenge, preferably a double-blind placebo-controlled food challenge (DBPCFC) with the relevant food is then indicated to diagnose food allergy with certainty. This thesis shows that oral challenges remain an important tool in ascertaining hazelnut and peanut allergy. It also appears that after the challenge, regardless of the results, parents feel less anxious about allergic reactions. To refine the diagnosis of hazelnut and peanut allergy, sensitization to specific allergens in hazelnut and peanut has been studied in the challenged children. It is demonstrated that in hazelnut allergy the specific allergen that is recognized is associated with the clinical severity of the allergy, while for peanut allergy it is the number of allergens recognized that seems to be paramount. In order to investigate possible therapies for peanut allergy, probiotics have been added to the diets of allergic children. However, probiotics do not change the inadequate immune response to peanut. Subsequently the activation of T cells by peanut allergens and possible T cell epitopes (an epitope is a recognition site on an allergen) has been studied in relation to IgE binding to these epitopes. This is an important issue when it comes to developing peanut-specific immunotherapy. Stimulation of T cell reactivity is necessary for immunotherapy to be successful. However, using intact peanut allergens for immunotherapy is too dangerous at present because severe IgE-mediated reactions can occur. If the B cell response (IgE reactivity) can be reduced by using a selection of non-IgE binding peptides, the side effects of such a treatment may be reduced to a considerable extent. The study showed that the epitopes that induced a T cell response were indeed only partially overlapping with IgE-binding epitopes. These promising results may allow the development of safe allergen-specific vaccines for the treatment of peanut allergy.

BACKGROUND:Food allergy is not always correctly diagnosed in children with atopic eczema dermatitis syndrome (AEDS) and treatment with an avoidance diet is not without danger.METHODS:After admission to our clinic, 11 children with a prolonged cow's milk (CM) elimination diet because of AEDS and sensitization underwent double-blind placebo-controlled food challenge (DBPCFC). Retrospectively, the exposure to CM, sensitization and reactions to accidental ingestion were carefully documented. The DBPCFC was used to evaluate the childrens' current status.RESULTS:Before the elimination period (median 2.3 years; started before the admission) all 11 children with AEDS were sensitized and had ingested CM (four bottle-fed; seven breast-fed without CM diet of the mother) without the development of acute reactions. The diagnosis of CM allergy was not confirmed by DBPCFC previously. After elimination the AEDS had not improved, but nevertheless the diet was continued. During the elimination period, eight of 11 children developed severe acute allergic reactions to CM after accidental ingestion. In evaluation, in our clinic all 11 children experienced acute allergic reactions to CM during DBPCFC.CONCLUSION:There is a considerable chance of developing acute allergic reactions to CM after elimination in children with AEDS without previous problems after CM intake.

Background: Current labeling practices for allergenic foods like peanut can be inadequate. For future regulatory and industry guidelines, information on no-observed-adverse-effect levels (NOAELs) and eliciting doses (EDs) for allergenic foods is necessary.Objective: To determine NOAEL and ED in a representative group of peanut-sensitized children, relate these data to history and sensitization, and evaluate the outcome of dietary management.Methods: From an overall eligible group of 96 peanut-sensitized children, a representative group of 27 was evaluated by questionnaires, skin prick test, determination of specific IgE, and double-blind placebo-controlled food challenge (DBPCFC) with peanut according to the international consensus protocol, with 9 doses ranging from 10 mu g to 3 g peanut flour. Dietary management was evaluated over a 12-month period.Results: Twenty-two children (81%) had a positive DBPCFC. The NOAEL in this group was 1 mg peanut flour, corresponding to 2 mg whole peanut. The ED for subjective symptoms (10 mg to 3 g) was significantly lower than for objective symptoms (100 mg to 3 g; P = .002). Severe reactions occurred only at high doses. EDs were not correlated to previous reactions by history, skin prick test, or specific IgE levels. All patients with a positive DBPCFC were advised to follow a strict diet. During the follow-up period, 10 patients had a less strict diet likely containing traces of peanut. In 3 cases, a mild reaction occurred with food products labeled "may contain peanut."Conclusion: The NOAEL in a representative group of children with peanut allergy was 2 mg. Dietary compliance in half of this group was inadequate.

RATIONALE: In ED studies patients with serious reactions to peanut are usually not included. In this study we included all children with peanut sensitization independent of their history. METHODS: Thirty two children (10 girls, 22 boys; aged 3.0-15.0 years) were included based on sensitization to peanut. During elimination, twenty of them experienced an allergic reaction to peanut, of which 8 had serious respiratory symptoms. Double blind placebo controlled food challenge (DBPCFC) with peanut was performed using the new international consensus protocol (Taylor et al, Clin Exp Allergy 2004; 34(5):689-695). Defatted peanut flour was given in 9 gradually increasing steps ranging from 10μg to 3g. Upon negative challenge an open challenge with 10g peanuts was performed. RESULTS: Sensitization to peanut was confirmed in all patients by specific IgE (<0.35-100 kU/L, mean 24.9) and/or SPT (0-18.4mm, mean 8.6). From the group without a previous reaction (n=12) 6 (50%) had a positive DBPCFC. Eliciting doses were 1g (n=3) and 3g (n=3). From the previously reacting group (n=20), 16 children (75%) developed a reaction during challenge, including 7 of 8 (88%) children with serious respiratory reaction to peanut in their history. Eliciting doses in 13 of these 16 children consisted of 10mg (n=2), 100mg (n=2), 300mg (n=3), 1g (n=5) and 3g (n=1), whereas 3/16 children reacted after the open challenge. Sensitization between both groups did not significantly differ. CONCLUSIONS: Children with previous reaction to peanut are more likely to react during DBPCFC. The ED in this group is up to 100-fold lower than in patients without previous reactions.