Publications by authors named "Maarten O Hoekstra"

32 Publications

Plasma IL-25 is elevated in a subgroup of patients with clinical reactivity to peanut.

Clin Transl Allergy 2013 Dec 2;3(1):40. Epub 2013 Dec 2.

Laboratory for Translational Immunology, Department of Paediatric Immunology, University Medical Centre, PO BOX 85090, Utrecht 3508 AB, The Netherlands.

Background: One of the IL-17 family members, IL-25, has been implicated with the initiation and amplification of Th2 responses in animal models and has been associated with airway hyper-reactivity. The involvement of IL-25 and also IL-17 in food allergic disease remains to be investigated.

Findings: In this study thirty children suspected of peanut allergic disease underwent a double-blind placebo controlled food challenge (DBPCFC) and IL-25 and IL-17 plasma levels were determined before and after challenge. IL-25 was highly elevated only in subgroup of children with a positive DBPCFC outcome. Plasma IL-25 was absent in children with a negative DBPCFC outcome and in healthy controls.

Conclusions: This study shows that IL-25, an IL-17 family member, is highly elevated only in children with a clinical response to peanut. This suggests a role for IL-25 in the pathogenesis of peanut allergy and elevated plasma IL-25 may be a sign of a severe atopic phenotype.
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http://dx.doi.org/10.1186/2045-7022-3-40DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176502PMC
December 2013

Recognition of self-heat shock protein 60 by T cells from patients with atopic dermatitis.

Cell Stress Chaperones 2013 Jan 7;18(1):87-95. Epub 2012 Aug 7.

Department of General Paediatrics, Wilhelmina Children's Hospital, Utrecht, The Netherlands.

Heat shock protein 60 (hsp60) is a highly conserved stress protein and target of self-reactive T cells in various inflammatory diseases. Not much is known about a possible role in atopic disease. As atopic diseases are considered to be the result of a disturbance in the balance between T helper cells type 2 and regulatory T cells, it is of interest to know whether hsp60 acts as a bystander antigen in atopic disease. Our aim was to investigate whether hsp60 is involved in the chronicity of inflammation of atopic dermatitis (AD). We studied the expression of hsp60 in skin tissue of adults with AD by immunohistochemistry. Peripheral blood mononuclear cells (PBMC) of children with AD were cultured with hsp60 and proliferative responses, cytokine secretion, surface markers, and functional assays were compared to responses of PBMC of healthy controls (HC). Hsp60 was detected more in lesional skin of AD patients compared to nonlesional skin. Furthermore, PBMC of children with AD proliferated more strongly in response to hsp60 compared to HC. hsp60-reactive T cells of atopic children produced high levels of IFNγ and low levels of IL-10. In vitro activation with hsp60 leads to the induction of CD4(+)CD25(bright) T cells expressing FOXP3 in both HC as well as in atopic children. However, despite their regulatory phenotype, hsp60-induced CD4(+)CD25(bright)CD127(-)FOXP3(+) T cells of AD patients were incapable of suppressing effector T cells in vitro. hsp60 is recognized by proinflammatory (IFNγ high, IL-10 low) T cells in atopic patients and is more present in lesional AD skin. This suggests that hsp60-specific T cell responses contribute to local inflammation in AD.
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http://dx.doi.org/10.1007/s12192-012-0361-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508125PMC
January 2013

Extensively hydrolysed casein formula supplemented with Lactobacillus rhamnosus GG maintains hypoallergenic status: randomised double-blind, placebo-controlled crossover trial.

BMJ Open 2012 5;2(2):e000637. Epub 2012 Mar 5.

The Food Allergy Referral Centre, Department of Pediatrics, Veneto Region, Università degli Studi di Padova, Padova, Italy.

Objective: To evaluate the hypoallergenicity of an extensively hydrolysed (EH) casein formula supplemented with Lactobacillus rhamnosus GG (LGG).

Design: A prospective, randomised, double-blind, placebo-controlled crossover trial.

Setting: Two study sites in Italy and The Netherlands.

Study Participants: Children with documented cow's milk allergy were eligible for inclusion in this trial.

Interventions: After a 7-day period of strict avoidance of cow's milk protein and other suspected food allergens, participants were tested with an EH casein formula with demonstrated hypoallergenicity (control, EHF) and a formula of the same composition with LGG added at 10(8) colony-forming units per gram powder (EHF-LGG) in randomised order in a double-blind placebo-controlled food challenge (DBPCFC). After absence of adverse reactions in the DBPCFC, an open challenge was performed with EHF-LGG, followed by a 7-day home feeding period with the same formula.

Main Outcome Measure: Clinical assessment of any adverse reactions to ingestion of study formulae during the DBPCFC.

Results: For all participants with confirmed cow's milk allergy (n=31), the DBPCFC and open challenge were classified as negative.

Conclusion: The EH casein formula supplemented with LGG is hypoallergenic and can be recommended for infants and children allergic to cow's milk who require an alternative to formulae containing intact cow's milk protein.

Trial Registration Number: http://ClinicalTrials.gov Identifier: NCT01181297.
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http://dx.doi.org/10.1136/bmjopen-2011-000637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3298831PMC
October 2012

Cord blood CD4+ T cells respond to self heat shock protein 60 (HSP60).

PLoS One 2011 13;6(9):e24119. Epub 2011 Sep 13.

Department of Pediatric Immunology, Wilhelmina Children's Hospital, Utrecht, The Netherlands.

Background: To prevent harmful autoimmunity most immune responses to self proteins are controlled by central and peripheral tolerance. T cells specific for a limited set of self-proteins such as human heat shock protein 60 (HSP60) may contribute to peripheral tolerance. It is not known whether HSP60-specific T cells are present at birth and thus may play a role in neonatal tolerance. We studied whether self-HSP60 reactive T cells are present in cord blood, and if so, what phenotype these cells have.

Methodology/principal Findings: Cord blood mononuclear cells (CBMC) of healthy, full term neonates (n = 21), were cultured with HSP60 and Tetanus Toxoid (TT) to study antigen specific proliferation, cytokine secretion and up-regulation of surface markers. The functional capacity of HSP60-induced T cells was determined with in vitro suppression assays. Stimulation of CBMC with HSP60 led to CD4(+) T cell proliferation and the production of various cytokines, most notably IL-10, Interferon-gamma, and IL-6. HSP60-induced T cells expressed FOXP3 and suppressed effector T cell responses in vitro.

Conclusion: Self-reactive HSP60 specific T cells are already present at birth. Upon stimulation with self-HSP60 these cells proliferate, produce cytokines and express FOXP3. These cells function as suppressor cells in vitro and thus they may be involved in the regulation of neonatal immune responses.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0024119PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3172234PMC
March 2012

Asthma symptoms and medication in the PIAMA birth cohort: evidence for under and overtreatment.

Pediatr Allergy Immunol 2011 Nov 13;22(7):652-9. Epub 2011 Jul 13.

Department of Pediatrics/Respiratory Medicine, Erasmus University, Rotterdam, The Netherlands.

Objective: Under and overtreatment of asthma may be a serious problem especially in young children, but the evidence is scarce and no longitudinal data are available. Our aim was to investigate whether inhaled medication use in young children was in agreement with asthma symptoms at the age of 2-8 yr.

Methods: Data were used from the 'Prevention and Incidence of Asthma and Mite Allergy' birth cohort, consisting of 3963 children born in the Netherlands. Between age 2 and 8 yr, children were followed up using annual postal questionnaires. Age-specific prevalences of asthma symptoms were assessed and compared with reported use of inhaled bronchodilators and/or corticosteroids.

Results: The proportion of current wheeze decreased with age. About a third of 'current wheezers' did not use any inhaled medication during the years in which symptoms were reported. At 8 yr, 30% of children with reported 'severe current asthma symptoms' were not using inhaled corticosteroids. On the other hand, up to 50% of children with inhaled corticosteroids for at least 2 yr did not report any wheezing during those 2 yr.

Conclusion: The proportion of symptomatic children without appropriate treatment was substantial throughout childhood, even when parents reported prolonged or severe symptoms. Treatment of asymptomatic children with inhaled corticosteroids increased with age and accounted for up to a third of all inhaled steroid use at 8 yr. These findings suggest that under and overtreatment of asthma in children was common.
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http://dx.doi.org/10.1111/j.1399-3038.2011.01193.xDOI Listing
November 2011

Gut derived lactic acid bacteria induce strain specific CD4(+) T cell responses in human PBMC.

Clin Nutr 2011 Dec 15;30(6):845-51. Epub 2011 Jun 15.

Center for Cellular and Molecular Intervention, Wilhelmina's Children Hospital, University Medical Center Utrecht, The Netherlands.

Background & Aims: Probiotic bacteria are used as food supplement in many different disease settings. The immune modulating capacity of different strains is not always properly tested which might result in a suboptimal choice of strains for clinical use.

Methods: The CD4 T cell responses to 19 different gut derived lactic acid bacteria were tested with different methods to show their diversity in immune modulation and to make a well-founded choice on which strains to use in future clinical trials. After co-culture of PBMC with bacteria, the induction of CD4(+) T cell subsets (regulatory T cells, T helper type (TH)1, TH2 and TH17) was analysed by rtPCR of transcription factor mRNA, intracellular FACS staining of transcription factors and cytokine production.

Results: Bacterial strains all have diverse, unique immune modulatory properties. Strains can induce Treg, TH1, TH2 and TH17 cells which can be shown at different levels of T cell activation, and is consistent for most strains tested. For TH1, TH17 and Treg, a positive correlation between the different methods was found. For TH2 cells the correlation was less consistent.

Conclusions: Probiotic bacteria have very different immune modulating capacities. Analysis of transcription factor mRNA is a suitable method for in vitro characterization of strains prior to clinical application.
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http://dx.doi.org/10.1016/j.clnu.2011.05.005DOI Listing
December 2011

Uncontrolled asthma at age 8: the importance of parental perception towards medication.

Pediatr Allergy Immunol 2011 Aug 20;22(5):462-8. Epub 2011 Feb 20.

Division of Pharmacoepidemiology & Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences (UIPS), Faculty of Science, Utrecht University, Utrecht, The Netherlands.

Background: Despite existing effective treatment options, asthma is uncontrolled in a considerable proportion of patients. The aim of this study was to identify determinants of uncontrolled asthma at age 8 in children participating in the PIAMA birth cohort study.

Methods: One hundred seventy children using inhaled corticosteroids in the previous 12 months at age 8 were included. Uncontrolled asthma was defined as: ≥3 items present in the past month: (1) day-time or (2) night-time asthma symptoms, (3) limitations in activities, (4) rescue medication use, (5) FEV(1) <0% predicted and (6) unscheduled physician visits because of asthma. Binomial regression was performed to study five groups of determinants representing asthma control: child and parental characteristics, environmental factors, therapy adherence and parental perception towards medication use (Beliefs about Medicines Questionnaire).

Results: Seventy seven children (45%) had uncontrolled asthma. Low maternal education (RR 1.6, 95% CI: 1.0-2.4) was associated with uncontrolled asthma. Parental necessity beliefs about medication use to maintain present and future health and parental concerns about potential adverse consequences of medication were also associated with uncontrolled asthma (RR 1.6, 95% CI: 1.1-2.2; and 1.6, 95% CI: 1.0-2.5, respectively).

Conclusions: Environmental factors and therapy adherence were not associated with asthma control. In our cohort, uncontrolled asthma is associated with low maternal education and with strong parental beliefs about medication necessity and higher concern about potential side effects of medication.
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http://dx.doi.org/10.1111/j.1399-3038.2011.01150.xDOI Listing
August 2011

Prediction of asthma in symptomatic preschool children using exhaled nitric oxide, Rint and specific IgE.

Thorax 2010 Sep;65(9):801-7

Department of Pediatrics/Respiratory Medicine, Erasmus University, Rotterdam, The Netherlands.

Rationale: For clinicians it remains very difficult to predict whether preschool children with symptoms suggestive of asthma will develop asthma in later childhood.

Objective: To investigate whether measurement of fraction of exhaled nitric oxide (FE(NO)), interrupter resistance (Rint) or specific immunoglobulin E (IgE) in 4-year-old children with suggestive symptoms can predict asthma symptoms up to age 8 years.

Methods: Children were recruited from the PIAMA birth cohort. All children with symptoms suggestive of asthma at age 3 or 4 years, who were invited for medical examination at age 4 (n=848), were eligible. Associations of FE(NO) (n=308), Rint (n=482) and specific IgE (n=380) at 4 years with wheezing and asthma at the ages of 5-8 years were assessed using repeated measurement analyses. The added predictive value of these objective tests was then investigated by including parameters for clinical history in the model.

Results: FE(NO) and specific IgE measured at 4 years were associated with wheezing and asthma at 8 years. Both tests also remained significant predictors after mutual adjustment and adjustment for clinical history: OR on wheezing at 8 years for FE(NO) ((10)log-scale, per IQR) 1.6 (95% CI 1.1 to 2.2) and for specific IgE 2.8 (95% CI 1.9 to 4.1). Rint was significantly associated with wheezing at age 6, but not at 7 and 8 years.

Conclusions: In preschool children with symptoms suggestive of asthma, both FE(NO) and specific IgE measured at age 4, but not Rint, improved the prediction of asthma symptoms until the age of 8 years, independent of clinical history.
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http://dx.doi.org/10.1136/thx.2009.126912DOI Listing
September 2010

High agreement between parental reported inhaled corticosteroid use and pharmacy prescription data.

Pharmacoepidemiol Drug Saf 2010 Nov;19(11):1199-203

Division of Pharmacoepidemiology & Pharmacotherapy, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Utrecht, the Netherlands.

Purpose: This study was conducted to assess the validity of parental reported use of inhaled corticosteroids (ICS) in children.

Methods: ICS users were identified within the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study and the PIAMA pharmacy sub-cohort which is nested within the PIAMA study. Complete medication histories were available for the first 8 years of life for children within the PIAMA pharmacy sub-cohort. Parental reported ICS use was measured by using data from questionnaires. ICS use in the pharmacy records was determined by using the Anatomical Therapeutic Chemical (ATC) codes. The proportion of overall agreement and kappa statistics with their corresponding 95% confidence intervals were calculated to quantify agreement between self-reported medication use and pharmacy prescription data.

Results: At all ages overall agreement was very high (>97%) and Cohen's kappa's ranged from 0.80 to 0.88 which also reflects excellent agreement between parental reported use of ICS and pharmacy prescription data.

Conclusions: Our finding suggests that parental report of medication use is a reliable source of data to asses ICS use in children. The questionnaire-based medication data collected within the PIAMA study can be used to study asthma medication use in a large group of children.
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http://dx.doi.org/10.1002/pds.2015DOI Listing
November 2010

Asthma therapy during the first 8 years of life: a PIAMA cohort study.

J Asthma 2010 Mar;47(2):209-13

Division of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences (UIPS), Faculty of Science, Utrecht University, 3508 TB Utrecht, The Netherlands.

Objective: Many studies evaluated asthma medication use in children in a cross-sectional manner, yet little is known about longitudinal use patterns. This study describes the formation of a longitudinal data set on asthma medication use and shows first results regarding the prevalence and incidence of medication use.

Methods: The PIAMA (Prevention and Incidence of Asthma and Mite Allergy) study is a prospective birth cohort study among 3963 Dutch children. Recruitment took place in 1996-1997. The data of the PIAMA birth cohort study were complemented with pharmacy data. Prescription information of family members was used to determine whether medication histories were complete from birth until age 8. The prevalence and incidence of asthma medication use was studied in children for whom complete medication histories were available.

Results: A first prescription for asthma medication was filled before age 8 by 280 (36%) children, with 88% starting therapy before age 5. Of all children who started therapy, 91.1% received short-acting beta(2)-agonists and 61.1% inhaled corticosteroids.

Conclusion: The applied method of data collection rendered a data set including 777 children with complete medication histories for their first 8 years of life. This data set provides the opportunity to study longitudinal medication use patterns. First analyses show that asthma medication is initiated in a rather high percentage of children in this cohort and mainly at an age at which an asthma diagnosis cannot yet be firmly established.
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http://dx.doi.org/10.3109/02770900903483790DOI Listing
March 2010

Polymorphisms in the mannan-binding lectin gene are not associated with questionnaire-reported respiratory tract infections in children.

J Infect Dis 2008 Dec;198(11):1707-13

Department of Pediatrics, Wilhelmina Children's Hospital, University Medical Center Utrecht, University of Utrecht, Lundlaan 6, Utrecht, The Netherlands.

Background: Low mannan-binding lectin (MBL) levels, caused by MBL2 polymorphisms, are suggested to contribute to susceptibility to respiratory tract infections (RTIs), particularly early in life. Large-scale replication of previous associations is needed, however. We investigated the association between MBL2 polymorphisms and the frequency of RTI in a large population-based birth cohort of white children.

Methods: The frequency of RTI was prospectively assessed by annual parental questionnaires until children were 4 years of age. Thirteen polymorphisms in MBL2 were determined in 987 Dutch children. Haplotypes, previously shown to be associated with functional levels of MBL, were constructed, and their associations with the frequency of RTI during year 1, year 2, and the first 4 years of life were assessed. High-producing, intermediate-producing, and deficient MBL2 genotypes were defined on the basis of exon 1 and Y/X promoter polymorphisms.

Results: No differences were found between investigated polymorphisms and haplotype frequencies in the population as a whole or between the groups with frequent, moderately frequent, or no RTIs reported. Deficient MBL2 genotypes were not associated with an increased risk of RTI (odds ratio, 0.71 [95% confidence interval, 0.25 to 2.05]) during years 1-4 of life. This was also true when year 1 and year 2 were studied separately.

Conclusion: These results suggest that, at the population level, MBL2 polymorphisms do not contribute to the risk of questionnaire-reported RTI in white children.
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http://dx.doi.org/10.1086/592989DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7109965PMC
December 2008

Do differences in childhood diet explain the reduced overweight risk in breastfed children?

Obesity (Silver Spring) 2008 Nov 28;16(11):2498-503. Epub 2008 Aug 28.

Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.

Breastfeeding has been associated with a reduced risk of overweight later in life. This study investigates whether differences in diet and lifestyle at 7 years of age between breastfed and formula-fed children can explain the difference in overweight prevalence at 8 years of age. We studied 2,043 Dutch children born in 1996-1997 who participated in the Prevention and Incidence of Asthma and Mite Allergy birth cohort study. Data on breastfeeding duration and diet and lifestyle factors at 7 years were collected using questionnaires. Weight and height were measured at 8 years. Overweight was defined according to international gender- and age-specific standards. Compared to nonbreastfed children (15.5%, n = 316), children breastfed for >16 weeks (38.0%, n = 776) consumed fruit and vegetables significantly more often and meat, white bread, carbonated soft drinks, chocolate bars, and fried snacks less often. Overall, breastfed children were less likely to have an unhealthy diet (adjusted prevalence ratio: 0.77, 95% confidence interval: 0.61-0.98). The associations could only partly be explained by maternal education, maternal overweight, and smoking during pregnancy. At 8 years, 14.5% (n = 297) of the children were overweight. Breastfeeding for >16 weeks was significantly associated with a lower overweight risk at 8 years (adjusted odds ratio: 0.67, 95% confidence interval: 0.47-0.97), and the association hardly changed after adjustment for diet (adjusted odds ratio: 0.71, 95% confidence interval: 0.49-1.03). Breastfed children had a healthier diet at 7 years compared to nonbreastfed children, but this difference could not explain the lower overweight risk at 8 years in breastfed children.
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http://dx.doi.org/10.1038/oby.2008.403DOI Listing
November 2008

Persistence of asthma medication use in preschool children.

Respir Med 2008 Oct 30;102(10):1446-51. Epub 2008 Jun 30.

Division of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, P.O. Box 80082, 3508 TB, Utrecht, The Netherlands.

Objective: In young children with asthmatic symptoms diagnostic difficulties lead to use of trials of asthma medication as a diagnostic tool. Our aim is to quantify the persistent use of asthma medication, initiated in the first year of life and identify determinants of this persistent use.

Patients And Methods: We identified 165 children within the PIAMA (Prevention and Incidence of Asthma and Mite Allergy) birth cohort who used asthma medication before the age of one. Persistent use was investigated during three years after the first prescription. A Cox regression analysis was performed to identify factors associated with persistent use.

Results: A total of 58.8% of children continued using asthma medication after the first prescription and 10.3% continued during three years. Children with doctor-diagnosed asthma (Hazard ratio of discontinuation (HR)=0.64, 95% CI: 0.45-0.91) or prescribed inhaled corticosteroids in the first year of life (HR of discontinuation=0.59, 95% CI: 0.40-0.86) were 1.6-1.7 times more likely to continue using asthma medication.

Conclusions: Persistence of asthma medication, prescribed in the first year of life is very low and is positively associated with doctor-diagnosed asthma and use of inhaled corticosteroids. Characterizing persistent users of asthma medication is important to understand prescribing of asthma medication in this age group.
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http://dx.doi.org/10.1016/j.rmed.2008.04.003DOI Listing
October 2008

Maternal food consumption during pregnancy and the longitudinal development of childhood asthma.

Am J Respir Crit Care Med 2008 Jul 10;178(2):124-31. Epub 2008 Apr 10.

Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, P.O. Box 80178, 3508 TD Utrecht, The Netherlands.

Rationale: Maternal diet during pregnancy has the potential to affect airway development and to promote T-helper-2-cell responses during fetal life. This might increase the risk of developing childhood asthma or allergy.

Objectives: We investigated the influence of maternal food consumption during pregnancy on childhood asthma outcomes from 1 to 8 years of age.

Methods: A birth cohort study consisting of a baseline of 4,146 pregnant women (1,327 atopic and 2,819 nonatopic). These women were asked about their frequency of consumption of fruit, vegetables, fish, egg, milk, milk products, nuts, and nut products during the last month. Their children were followed until 8 years of age. Longitudinal analyses were conducted to assess associations between maternal diet during pregnancy and childhood asthma outcomes over 8 years.

Measurements And Main Results: Complete data were obtained for 2,832 children. There were no associations between maternal vegetable, fish, egg, milk or milk products, and nut consumption and longitudinal childhood outcomes. Daily consumption of nut products increased the risk of childhood wheeze (odds ratio [OR] daily versus rare consumption, 1.42; 95% confidence interval [95% CI], 1.06-1.89), dyspnea (OR, 1.58; 95% CI, 1.16-2.15), steroid use (OR, 1.62; 95% CI, 1.06-2.46), and asthma symptoms (OR, 1.47; 95% CI, 1.08-1.99).

Conclusions: Results of this study indicate an increased risk of daily versus rare consumption of nut products during pregnancy on childhood asthma outcomes. These findings need to be replicated by other studies before dietary advice can be given to pregnant women.
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http://dx.doi.org/10.1164/rccm.200710-1544OCDOI Listing
July 2008

Lipid transfer protein-linked hazelnut allergy in children from a non-Mediterranean birch-endemic area.

J Allergy Clin Immunol 2008 Feb 26;121(2):423-428.e2. Epub 2007 Nov 26.

Department of Dermatology/Allergology, University Medical Centre, Utrecht, The Netherlands.

Background: Hazelnut allergy in birch pollen-exposed areas is usually due to cross-reactivity (Cor a 1 and 2) and is usually mild in nature (oral allergy). In areas without birches, severe reactions are more prevalent and linked to sensitization to the lipid transfer protein (LTP) Cor a 8.

Objective: We sought to investigate whether sensitization to LTP plays a role in more severe (objective) hazelnut-induced symptoms in children from a birch-endemic area.

Methods: Sensitization to Cor a 8, Cor a 2, Cor a 1, and Bet v 1 was determined by means of RASTs and immunoblotting in hazelnut-sensitized children with (n = 8) and without (n = 18) objective reactions during double-blind, placebo-controlled food challenges. Additionally, samples from 191 hazelnut-sensitized nonchallenged children were analyzed.

Results: Children with objective reactions during double-blind, placebo-controlled food challenge had higher IgE titers to hazelnut (P < .001) and recognized more allergens on immunoblotting (P = .001) than those without such reactions. All children with objective symptoms were sensitized to Cor a 8 (0.51-23.3 IU/mL) compared with only 1 child without objective reactions (0.90 IU/mL). In a multivariate analysis only IgE against Cor a 8 remained as an independent risk factor (undefined odds ratio; P < .0001). In the group of nonchallenged children (n = 191), the prevalence of LTP sensitization was greater than 30%. Unexpectedly, sensitization to Cor a 1 was observed in children not sensitized to Bet v 1.

Conclusion: Sensitization to hazelnut LTP is a risk factor for objective symptoms in children from a birch-endemic area.
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http://dx.doi.org/10.1016/j.jaci.2007.10.009DOI Listing
February 2008

No day-care visits during the first year of life for infants with atopic parents?

J Allergy Clin Immunol 2008 Feb 27;121(2):535; author reply 535-6. Epub 2007 Sep 27.

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http://dx.doi.org/10.1016/j.jaci.2007.07.064DOI Listing
February 2008

Mannose-binding lectin and upper respiratory tract infections in children and adolescents: a review.

Arch Otolaryngol Head Neck Surg 2006 May;132(5):482-6

Department of Pediatric Immunology, Wilhelmina Children's Hospital, University Medical Center, Utrecht, the Netherlands.

Objective: To review the literature on mannose-binding lectin (MBL) polymorphisms and susceptibility for upper respiratory tract infection (URI) in children and adolescents.

Data Sources: We searched PubMed from 1966 and EMBASE from 1974 to July 2005, using the terms respiratory tract infection, respiratory infection, upper respiratory infection, MBL, and mannose-binding lectin.

Study Selection: Initially, 110 studies were identified. Two reviewers independently screened identified titles and abstracts. Potentially relevant studies were obtained and the full text examined. Inclusion criteria were human subjects, 18 years or younger, URI, and MBL polymorphisms. Seven of the initially identified studies met the inclusion criteria.

Data Extraction: Information was gathered for each study on study design, population, possible confounders, and outcomes measured.

Data Synthesis: Because there was significant heterogeneity between the identified studies, we had to describe the identified studies separately. The largest case-control studies (n = 3) as well as the cohort study (n = 1) suggest an association between MBL polymorphisms and URI, especially in young children. Results of the smaller studies (n = 3) are inconsistent.

Conclusions: The association between MBL polymorphisms and URI in children remains controversial. Large prospective cohort studies with regular documentation of URI and possible confounders such as atopy and environmental factors are required to establish the role of MBL polymorphisms in susceptibility for URI.
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http://dx.doi.org/10.1001/archotol.132.5.482DOI Listing
May 2006

Determination of no-observed-adverse-effect levels and eliciting doses in a representative group of peanut-sensitized children.

J Allergy Clin Immunol 2006 Feb;117(2):448-54

Department of Dermatology/Allergology, University Medical Center, Utrecht, The Netherlands.

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 microg 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.
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http://dx.doi.org/10.1016/j.jaci.2005.11.035DOI Listing
February 2006

Electromyographic monitoring of respiratory muscle activity in dyspneic infants and toddlers.

Respir Physiol Neurobiol 2006 Feb 14;150(2-3):191-9. Epub 2005 Jul 14.

Department of Pediatric Pulmonology, Emma Children's Hospital, University Hospital, PO Box 22.660, 1100 DD Amsterdam, The Netherlands.

The aim of this study was to investigate whether the changes that occurred in the clinical asthma score (CAS) correlated with the changes in the respiratory electromyographic (EMG) activity over the days during admission to hospital in dyspneic infants and toddlers. Sixteen infants and toddlers (9 males) were studied during admission and 7 days after discharge. The CAS was used to assess the severity of dyspnea and consists of five items: respiration rate, wheezing, retractions, observed dyspnea, and inspiration-to-expiration ratio. Each item was scaled 0, 1, or 2, with a maximum score of 10. Electrical activity from the diaphragm (di) and intercostal muscles (int) was derived from surface electrodes. The logarithm of the EMG-Activity-Ratio (log EMGAR; ratio of mean peak-to-bottom EMG activity during admission to the hospital, to that at baseline, 7 days after discharge) was used as EMG parameter. For assessing the association between the repeated observations of the CAS and the EMG measurements we used the quantity r2 obtained with analysis of covariance. On the day of admission the patients had a mean CAS of 5.9 +/- 1.2. On the day of discharge the mean CAS decreased significantly to 2.1 +/- 1.6, indicating that the CAS returned to normal values. In line with this observation, a significant decrease in the log EMGARdi and log EMGARint was observed during the stay in the hospital. Over all subjects the correlation coefficient (r) of log EMGARdi versus CAS was 0.71, log EMGARint versus CAS was 0.67, and the mean log EMGAR versus CAS was 0.75 (p < 0.01, for all values). The correlation coefficients of subjects of < or = 1 year seemed to be lower than those of subjects of > 1 year of age (p < 0.01) and female subjects showed higher correlation coefficients than males. This study showed a moderate, but significant, relationship between the changes that occurred in the CAS and the changes in respiratory EMG activity during admission to hospital in dyspneic infants and toddlers. Moreover, the correlation coefficients of the combined leads of the intercostals and diaphragm (mean log EMGAR) were higher than those of the separate leads. The EMG measurements would extend diagnostic possibilities and would provide an objective measure to evaluate the clinical course of the disease and the efficacy of therapy in infants and toddlers with recurrent wheezing disorders.
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http://dx.doi.org/10.1016/j.resp.2005.05.029DOI Listing
February 2006

The Slc11a1 (Nramp1) gene controls efficacy of mycobacterial treatment of allergic asthma.

J Immunol 2003 Jul;171(2):754-60

Department of Pharmacology and Pathophysiology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.

Genes controlling antibacterial resistance may be important in the hygiene hypothesis, which states that lack of bacterial infections during childhood would favor development of allergic disease. We, therefore, studied whether Nramp1 (Slc11a1) alleles, which determine susceptibility (Nramp1(s)) or resistance (Nramp1(r)) to intracellular bacteria, affect the efficacy of heat-killed Mycobacterium vaccae in the treatment of allergic asthma in a mouse model. Treatment of OVA-sensitized Nramp1(s) mice with M. vaccae suppressed airway hyperresponsiveness, airway eosinophilia, Ag-specific IgE, and IL-4 and IL-5 production after OVA aerosol challenge. In contrast, M. vaccae hardly affected these parameters in Nramp1(r) mice. In addition, The Nramp1 gene affected both T cell-mediated responses to M. vaccae in vivo and the level of macrophage activation after stimulation with M. vaccae in vitro. In conclusion, the efficacy of M. vaccae in preventing allergic and asthmatic manifestations in a mouse model is strongly affected by Nramp1 alleles. These findings could have important implications for the future use of mycobacteria and their components in the prevention or treatment of allergic asthma. A new link is described between genes, the environment, and the development of allergy, in which the Nramp1 gene fine tunes the hygiene hypothesis.
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http://dx.doi.org/10.4049/jimmunol.171.2.754DOI Listing
July 2003

Therapeutic treatment with heat-killed Mycobacterium vaccae (SRL172) in a mild and severe mouse model for allergic asthma.

Eur J Pharmacol 2003 Jun;470(3):193-9

Department of Pharmacology and Pathophysiology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB, Utrecht, The Netherlands.

The hypothesis that a lack of early childhood bacterial infections would favor the development of allergic disease suggests that bacteria can be used as a potential treatment for allergic asthma. Therefore, in this study, we investigated the therapeutic potential of heat-killed Mycobacterium vaccae in two mouse models of allergic asthma. For this purpose, mice were sensitized i.p. with ovalbumin/alum (severe model) or ovalbumin alone (mild model) and challenged on days 77, 80 and 83 by inhalation of either ovalbumin or saline aerosols. Treatment of mice with M. vaccae (s.c. 10(7) or 10(8) colony-forming units) on days 56 and 63, however, did not reduce airway hyperresponsiveness and eosinophilia, IgE and interleukin-5 production 24 h after ovalbumin challenge in either mouse model. We therefore conclude that treatment of sensitized mice with M. vaccae before allergen exposure is not able to reduce the allergic and asthma-like response in a mild and a severe model of allergic asthma.
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http://dx.doi.org/10.1016/s0014-2999(03)01794-1DOI Listing
June 2003

Influence of the macrophage bacterial resistance gene, Nramp1 (Slc11a1), on the induction of allergic asthma in the mouse.

FASEB J 2003 May 28;17(8):958-60. Epub 2003 Mar 28.

Department of Pharmacology and Pathophysiology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.

Based on the hygiene hypothesis that lack of early childhood bacterial infections would favor development of allergic disease, we hypothesize that genes controlling antibacterial resistance may be important as well. We, therefore, studied whether Nramp1 alleles that determine resistance (Nramp1r) or susceptibility (Nramp1s) to intracellular bacteria at the macrophage level affect sensitivity to induction of allergic asthma. Nramp1s and congenic Nramp1r mice were sensitized with ovalbumin/alum on days 0 and 14 and challenged with ovalbumin or saline aerosols on days 42, 45, and 48. On day 49, airway responsiveness was assessed, blood was withdrawn, and lung lavage was performed. We demonstrated that ovalbumin sensitization and challenge of Nramp1s and Nramp1r mice caused comparable airway hyperreactivity and airway eosinophilia and a similar increase in serum levels of ovalbumin-specific IgG1 and IgG2a. Ovalbumin challenge, however, induced significantly lower serum levels of total and ovalbumin-specific IgE and significantly lower mast cell degranulation in Nramp1r mice as compared with Nramp1s mice. In addition, ovalbumin challenge of Nramp1r mice led to significantly less release of Th2 cytokines into the airways. Results show that Nramp1 can affect the development of allergy but not the development of airway hyperresponsiveness in the mouse.
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http://dx.doi.org/10.1096/fj.02-0985fjeDOI Listing
May 2003