Total Synthesis of a Partial Structure from Arabinogalactan and Its Application for Allergy Prevention.

Arabinogalactan, a microheterogeneous polysaccharide occurring in plants, is known for its allergy-protective activity, which could potentially be used for preventive allergy treatment. New treatment options are highly desirable, especially in a preventive manner, due to the constant rise of atopic diseases worldwide. The structural origin of the allergy-protective activity of arabinogalactan is, however, still unclear and isolation of the polysaccharide is not feasible for pharmaceutical applications due to a variation of the activity of the natural product and contaminations with endotoxins. Therefore, a pentasaccharide partial structure was selected for total synthesis and subsequently coupled to a carrier protein to form a neoglycoconjugate. The allergy-protective activity of arabinogalactan could be reproduced with the partial structure in subsequent in vivo experiments. This is the first example of a successful simplification of arabinogalactan with a single partial structure while retaining its allergy-preventive potential.

Effect of grass sublingual tablet immunotherapy is similar in children and adults: A Bayesian approach to design pediatric sublingual immunotherapy trials.

BACKGROUND: Large sample sizes are needed for sublingual immunotherapy (SLIT) trials because of inherent data variability secondary to inconsistent allergen exposure. Obtaining large sample sizes for pediatric SLIT trials is challenging, but a Bayesian approach using prior adult data can reduce the necessary sample size. OBJECTIVE: We sought to describe how a Bayesian framework using prior information from adult trials can be used to improve pediatric SLIT clinical development. METHODS: Data were compiled by using a frequentist approach (conventional clinical trial approach independent of prior data) from trials conducted during the clinical development of timothy grass SLIT-tablets. RESULTS: The treatment effect of timothy grass SLIT-tablets was considered similar between pediatric (n = 795) and adult (n = 2299) data pools, with relative total combined symptom plus medication score improvement versus placebo of 21% (95% CI, 11.0% to 30.4%) and 20% (95% CI, 14.6% to 24.4%), respectively. Phleum pratense-specific IgG4 and IgE-blocking factor increased from baseline in both children and adults treated with timothy grass SLIT-tablets. Given the reasonable assumption in similarity of treatment response between adults and children, a Bayesian approach is described to demonstrate rigorous efficacy criteria for pediatric trials incorporating information from prior adult trials and thereby reduce the sample size. CONCLUSIONS: Data support the similarity of efficacy and immunologic changes between children and adults treated with SLIT for allergic rhinoconjunctivitis. Therefore it is appropriate to use data from adult trials to design feasible trials in children, which might reduce unsafe off-label use by promoting more quickly proper labeling of approved products.

Side effects during subcutaneous immunotherapy in children with allergic diseases.

BACKGROUND: Allergen-specific immunotherapy is the only causal form of therapy for IgE-mediated allergic diseases. Subcutaneous immunotherapy (SCIT) is considered safe and well tolerated in adults, yet there is less evidence of safety in the pediatric population. METHODS: A non-interventional prospective observing longitudinal study was carried out to determine the incidence of local and systemic side effects by SCIT, routinely performed in pediatric patients. A total of 581 pediatric patients were observed in 18 study centers between March 2012 and October 2014, recording 8640 treatments and 10 015 injections. RESULTS: A total of 54.6% of the patients experienced immediate local side effects at least once; delayed local side effects were seen in 56.1%. Immediate systemic adverse reactions occurred in 2.2% of patients; 7.4% experienced delayed systemic side effects. However, severe systemic side effects (grade III in the classification of Ring and Messmer) were seen in 0.03% of all treatments, all appearing within 30 minutes after the injections. No grade IV reactions were observed. In addition, many potential risk factors were investigated, yet only a few were found to be associated with the occurrence of side effects. CONCLUSIONS: Subcutaneous immunotherapy is a safe form of therapy in pediatric patients, with similar rates of local side effects compared to adult patients and low rates of severe systemic side effects. However, local and systemic reactions occurring later than 30 minutes after injection were observed more often than expected, which makes it essential to be attentive on behalf of pediatricians, patients, and parents.

Allergy-Protective Arabinogalactan Modulates Human Dendritic Cells via C-Type Lectins and Inhibition of NF-κB.

Arabinogalactan (AG) isolated from dust of a traditional farm prevents disease in murine models of allergy. However, it is unclear whether this polysaccharide has immune regulatory properties in humans. The aim of this study was to test the influence of AG on the immune-stimulating properties of human dendritic cells (DCs). Moreover, we sought to identify the receptor to which AG binds. AG was produced from plant callus tissue under sterile conditions to avoid the influence of pathogen-associated molecular patterns in subsequent experiments. The influence of AG on the human immune system was investigated by analyzing its impact on monocyte-derived DCs. To analyze whether the T cell stimulatory capacity of AG-stimulated DCs is altered, an MLR with naive Th cells was performed. We revealed that AG reduced T cell proliferation in a human MLR. In the search for a molecular mechanism, we found that AG binds to the immune modulatory receptors DC-specific ICAM-3 -: grabbing non integrin (DC-SIGN) and macrophage mannose receptor 1 (MMR-1). Stimulation of these receptors with AG simultaneously with TLR4 stimulation with LPS increased the expression of the E3 ubiquitin-protein ligase tripartite motif -: containing protein 21 and decreased the phosphorylation of NF-κB p65 in DCs. This led to a reduced activation profile with reduced costimulatory molecules and proinflammatory cytokine production. Blocking of MMR-1 or DC-SIGN with neutralizing Abs partially inhibits this effect. We conclude that AG dampens the activation of human DCs by LPS via binding to DC-SIGN and MMR-1, leading to attenuated TLR signaling. This results in a reduced T cell activation capacity of DCs.

Doublesex and mab-3 related transcription factor 1 (DMRT1) is a sex-specific genetic determinant of childhood-onset asthma and is expressed in testis and macrophages.

BACKGROUND: Asthma is a disease affecting more boys than girls in childhood and more women than men in adulthood. The mechanisms behind these sex-specific differences are not yet understood. OBJECTIVE: We analyzed whether and how genetic factors contribute to sex-specific predisposition to childhood-onset asthma. METHODS: Interactions between sex and polymorphisms on childhood asthma risk were evaluated in the Multicentre Asthma Genetics in Childhood Study (MAGICS)/Phase II International Study of Asthma and Allergies in Childhood (ISAAC II) population on a genome-wide level, and findings were validated in independent populations. Genetic fine mapping of sex-specific asthma association signals was performed, and putatively causal polymorphisms were characterized in vitro by using electrophoretic mobility shift and luciferase activity assays. Gene and protein expression of the identified gene doublesex and mab-3 related transcription factor 1 (DMRT1) were measured in different human tissues by using quantitative real-time PCR and immunohistochemistry. RESULTS: Polymorphisms in the testis-associated gene DMRT1 displayed interactions with sex on asthma status in a population of primarily clinically defined asthmatic children and nonasthmatic control subjects (lowest P = 5.21 × 10(-6)). Replication of this interaction was successful in 2 childhood populations clinically assessed for asthma but showed heterogeneous results in other population-based samples. Polymorphism rs3812523 located in the putative DMRT1 promoter was associated with allele-specific changes in transcription factor binding and promoter activity in vitro. DMRT1 expression was observed not only in the testis but also in lung macrophages. CONCLUSION: DMRT1 might influence sex-specific patterns of childhood asthma, and its expression in testis tissue and lung macrophages suggests a potential involvement in hormone or immune cell regulation.

Influence of an Allergen-Specific Th17 Response on Remodeling of the Airways.

We showed previously that sensitization of mice with dendritic cells (DCs) via the airways depends on activation of these cells with LPS. Allergen-pulsed DCs that were stimulated with low doses of LPS induce a strong Th2 response in vivo. Our objective was to investigate whether airway sensitization of mice by the application of DCs with a phenotype that is able to induce Th17 cells results in increased remodeling of the airways. We generated DCs from the bone marrow of mice and pulsed them with LPS-free ovalbumin. Subsequently, cells were activated with LPS with or without ATP for inflammasome activation. The activated cells were used to sensitize mice via the airways. Intranasal instillation of DCs that were activated with 0.1 ng/ml LPS induced a Th2 response with airway eosinophilia. High doses of LPS, particularly when given in combination with ATP, led to induction of a mixed Th2/Th17 response. Interestingly, we found a correlation between IL-17A production and the remodeling of the airways. Stimulation of mouse fibroblasts with purified IL-17A protein in vitro resulted in transforming growth factor-ß1 secretion and collagen transcription. Interestingly, we found enhanced secretion of transforming growth factor-ß1 by fibroblasts after costimulation with IL-17A and the profibrotic factor wingless-type MMTV integration site family, member 5A (Wnt5a). We showed that an allergen-specific Th17 response in the airway is accompanied by increased airway remodeling. Furthermore, we revealed that increased remodeling is not only based on neutrophilic inflammation, but also on the direct impact of IL-17A on airway structural cells.

Polymorphisms related to ORMDL3 are associated with asthma susceptibility, alterations in transcriptional regulation of ORMDL3, and changes in TH2 cytokine levels.

BACKGROUND: Chromosome 17q21, harboring the orosomucoid 1-like 3 (ORMDL3) gene, has been consistently associated with childhood asthma in genome-wide association studies. OBJECTIVE: We investigated genetic variants in and around ORMDL3 that can change the function of ORMDL3 and thus contribute to asthma susceptibility. METHODS: We performed haplotype analyses and fine mapping of the ORMDL3 locus in a cross-sectional (International Study of Asthma and Allergies in Childhood Phase II, n = 3557 total subjects, n = 281 asthmatic patients) and case-control (Multicenter Asthma Genetics in Childhood Study/International Study of Asthma and Allergies in Childhood Phase II, n = 1446 total subjects, n = 763 asthmatic patients) data set to identify putative causal single nucleotide polymorphisms (SNPs) in the locus. Top asthma-associated polymorphisms were analyzed for allele-specific effects on transcription factor binding and promoter activity in vitro and gene expression in PBMCs after stimulation ex vivo. RESULTS: Two haplotypes (H1 and H2) were significantly associated with asthma in the cross-sectional (P = 9.9 × 10(-5) and P = .0035, respectively) and case-control (P = 3.15 × 10(-8) and P = .0021, respectively) populations. Polymorphisms rs8076131 and rs4065275 were identified to drive these effects. For rs4065275, a quantitative difference in transcription factor binding was found, whereas for rs8076131, changes in upstream stimulatory factor 1 and 2 transcription factor binding were observed in vitro by using different cell lines and PBMCs. This might contribute to detected alterations in luciferase activity paralleled with changes in ORMDL3 gene expression and IL-4 and IL-13 cytokine levels ex vivo in response to innate and adaptive stimuli in an allele-specific manner. Both SNPs were in strong linkage disequilibrium with asthma-associated 17q21 SNPs previously related to altered ORMDL3 gene expression. CONCLUSION: Polymorphisms in a putative promoter region of ORMDL3, which are associated with childhood asthma, alter transcriptional regulation of ORMDL3, correlate with changes in TH2 cytokines levels, and therefore might contribute to the childhood asthma susceptibility signal from 17q21.

Allergy and asthma prevention 2014.

Asthma and allergic diseases have become one of the epidemics of the 21st century in developed countries. Much of the success of other areas of medicine, such as infectious diseases, lies on preventive measures. Thus, much effort is also being placed lately in the prevention of asthma and allergy. This manuscript reviews the current evidence, divided into four areas of activity. Interventions modifying environmental exposure to allergens have provided inconsistent results, with multifaceted interventions being more effective in the prevention of asthma. Regarding nutrition, the use of hydrolyzed formulas in high-risk infants reduces the incidence of atopic dermatitis, while there is for now not enough evidence to recommend other dietary modifications, prebiotics, probiotics, or other microbial products. Pharmacologic agents used until now for prevention have not proved useful, while there is hope that antiviral vaccines could be useful in the future. Allergen-specific immunotherapy is effective for the treatment of allergic patients with symptoms; the study of its value for primary and secondary prevention of asthma and allergy is in its very preliminary phases. The lack of success in the prevention of these disorders lies on their complexity, which involves many genetic, epigenetic, and environmental interactions. There is a need to identify target populations, involved mechanisms and interactions, and the best interventions. These must be effective, feasible, implementable, and affordable.

Proteolytic activity in cowshed dust extracts induces C5a release in murine bronchoalveolar lavage fluids which may account for its protective properties in allergic airway inflammation.

OBJECTIVE: Intranasal application of cowshed dust extract (CDE) during sensitisation in a murine model of experimental asthma leads to a significant alleviation of the clinical parameters of the allergic immune response. However, neither the immunological mechanisms underlying this protective effect nor all of the protective substances included in CDE have yet been described. Recently, complement factor 5a (C5a) receptor signalling has been identified to play a regulatory role in allergic airway disease. Thus we investigated whether CDE can activate the complement system to release biologically active C5a in the lung. METHODS: Proteins included in CDE were identified by mass spectrometry. Complement cleaving activity of a serine protease identified in CDE was validated with the purified enzyme, and the biological activity of the released C5a was determined. C5a was applied in a murine model of allergy to prove its protective impact on allergic airway disease. RESULTS: CDE induced the release of C5a in murine bronchoalveolar lavages (BAL). We identified a serine protease from the midgut of tenebrio molitor larvae in CDEs which was able to induce the release of biologically active C5a in murine BAL. We applied C5a in different doses to female Balb/c mice during the sensitisation phase and during the first antigen challenge and showed that C5a has the ability to dampen important parameters of allergic airway inflammation, such as infiltration of proinflammatory cells into lung tissue or Th2 cytokine secretion by lung cells. CONCLUSIONS: We conclude that the C5a generating enzyme included in CDE might account for some of the allergy protective effects of CDE by generation of C5a in murine lungs.

Different FCER1A polymorphisms influence IgE levels in asthmatics and non-asthmatics.

BACKGROUND: Recently, three genome-wide association studies (GWAS) demonstrated FCER1A, the gene encoding a ligand-binding subunit of the high-affinity IgE receptor, to be a major susceptibility locus for serum IgE levels. The top association signal differed between the two studies from the general population and the one based on an asthma case-control design. In this study, we investigated whether different FCER1A polymorphisms are associated with total serum IgE in the general population and asthmatics specifically. METHODS: Nineteen polymorphisms were studied in FCER1A based on a detailed literature search and a tagging approach. Polymorphisms were genotyped by the Illumina HumanHap300Chip (6 polymorphisms) or MALDI-TOF MS (13 polymorphisms) in at least 1303 children (651 asthmatics) derived from the German International Study of Asthma and Allergies in Childhood II and Multicentre Asthma Genetics in Childhood Study. RESULTS: Similar to two population-based GWAS, the peak association with total serum IgE was observed for SNPs rs2511211, rs2427837, and rs2251746 (mean r(2) > 0.8), with the lowest p-value of 4.37 × 10(-6). The same 3 polymorphisms showed the strongest association in non-asthmatics (lowest p = 0.0003). While these polymorphisms were also associated with total serum IgE in asthmatics (lowest p = 0.003), additional polymorphisms (rs3845625, rs7522607, and rs2427829) demonstrated associations with total serum IgE in asthmatics only (lowest p = 0.01). CONCLUSIONS: These data suggest that FCER1A polymorphisms not only drive IgE levels in the general population but that specific polymorphisms may also influence IgE in association with asthma, suggesting that disease-specific mechanisms in IgE regulation exist.

Genetic variants regulating ORMDL3 expression contribute to the risk of childhood asthma.

Asthma is caused by a combination of poorly understood genetic and environmental factors. We have systematically mapped the effects of single nucleotide polymorphisms (SNPs) on the presence of childhood onset asthma by genome-wide association. We characterized more than 317,000 SNPs in DNA from 994 patients with childhood onset asthma and 1,243 non-asthmatics, using family and case-referent panels. Here we show multiple markers on chromosome 17q21 to be strongly and reproducibly associated with childhood onset asthma in family and case-referent panels with a combined P value of P < 10(-12). In independent replication studies the 17q21 locus showed strong association with diagnosis of childhood asthma in 2,320 subjects from a cohort of German children (P = 0.0003) and in 3,301 subjects from the British 1958 Birth Cohort (P = 0.0005). We systematically evaluated the relationships between markers of the 17q21 locus and transcript levels of genes in Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines from children in the asthma family panel used in our association study. The SNPs associated with childhood asthma were consistently and strongly associated (P < 10(-22)) in cis with transcript levels of ORMDL3, a member of a gene family that encodes transmembrane proteins anchored in the endoplasmic reticulum. The results indicate that genetic variants regulating ORMDL3 expression are determinants of susceptibility to childhood asthma.

High-dose sublingual immunotherapy with single-dose aqueous grass pollen extract in children is effective and safe: a double-blind, placebo-controlled study.

BACKGROUND: Sublingual allergen-specific immunotherapy is a viable alternative to subcutaneous immunotherapy particularly attractive for use in children. OBJECTIVE: This study investigated efficacy and safety of high-dose sublingual immunotherapy (SLIT) in children allergic to grass pollen in a randomized, double-blind, placebo-controlled trial. METHODS: After a baseline seasonal observation, 207 children aged 4 to 12 years with grass pollen-allergic rhinitis/rhinoconjunctivitis with/without bronchial asthma (Global Initiative for Asthma I/II) received either high-dose grass pollen SLIT or placebo daily for 1 pre-/co-seasonal period. The primary end point was the change of the area under the curve of the symptom-medication score (SMS) from the baseline season to the first season after start of treatment. Secondary outcomes were well days, responders, immunologic changes, and safety. RESULTS: Mean changes in the area under the curve of the SMS from the baseline to the first grass pollen season after the start of treatment were -212.5 for the active group and -97.8 for the placebo group (P = .0040). Rhinoconjunctivitis SMS (P = .0020) and separated symptom and medication scores were also statistically different between the 2 groups (P = .0121 and P = .0226, respectively). The number of well days and the percentage of responders were greater in the active group. Changes in allergen-specific IgE and IgG levels indicated a significant immunologic effect. The treatment was well tolerated, and no serious treatment-related events were reported. CONCLUSIONS: This study confirmed that this SLIT preparation significantly reduced symptoms and medication use in children with grass pollen-allergic rhinoconjunctivitis. The preparation showed significant effects on allergen-specific antibodies, was well tolerated, and appeared to be a valid therapeutic option in children allergic to grass pollen. This trial was registered at www.clinicaltrials.gov as NCT00841256.

Genetic variants in Protocadherin-1, bronchial hyper-responsiveness, and asthma subphenotypes in German children.

BACKGROUND: Recently, Protocadherin-1 (PCDH1) was reported as a novel susceptibility gene for bronchial hyper-responsiveness (BHR) and asthma. PCDH1 is located on chromosome 5q31-33, in the vicinity of several known candidate genes for asthma and allergy. To exclude that the associations observed for PCDH1 originate from the nearby cytokine cluster, an extensive linkage disequilibrium (LD) analysis was performed. Effects of polymorphisms in PCDH1 on asthma, BHR, and related phenotypes were studied comprehensively. METHODS: Genotype information was acquired from Illumina HumanHap300Chip genotyping, MALDI-TOF MS genotyping, and imputation. LD was assessed by Haploview 4.2 software. Associations were investigated in a population of 1454 individuals (763 asthmatics) from two German study populations [MAGICS and International Study of Asthma and Allergies in Childhood phase II (ISAAC II)] using logistic regression to model additive effects. RESULTS: No relevant LD between PCDH1 tagging polymorphisms and 98 single nucleotide polymorphisms within the cytokine cluster was detected. While BHR was not associated with PCDH1 polymorphisms, significant associations with subphenotypes of asthma were observed. CONCLUSION: Protocadherin-1 polymorphisms may specifically affect the development of non-atopic asthma in children. Functional studies are needed to further investigate the role of PCDH1 in BHR and asthma development.

Arabinogalactan isolated from cowshed dust extract protects mice from allergic airway inflammation and sensitization.

BACKGROUND: Extract from cowshed dust (CDE) is a source of immunomodulating substances. We have previously shown that such substances protect from experimental allergic disorders in a mouse model of asthma. OBJECTIVE: The objective of this study was to identify immunomodulatory molecules in extracts of dust from an allergy protective farming environment. METHODS: Polysaccharides were isolated from CDE and plants by chromatography and precipitation with specific reagents. Polysaccharides were then characterized by nuclear magnetic resonance spectroscopy. Subsequently, the allergy-protective potential of isolated polysaccharides was tested in a mouse model of asthma. RESULTS: The authors demonstrate that plant arabinogalactans are contained in CDE in high concentrations. The source of this arabinogalactan is fodder, in particular a prevalent grass species known as Alopecurus pratensis. Treatment of murine dendritic cells with grass arabinogalactan resulted in autocrine IL-10 production. Interestingly, these dendritic cells were not able to induce an allergic immune response. Furthermore, intranasal application of grass arabinogalactan protected mice from developing atopic sensitization, allergic airway inflammation and airway hyperreactivity in a mouse model of allergic asthma. This allergy-protective effect is specific for grass arabinogalactan because control experiments with arabinogalactan from gum arabic and larch revealed that these molecules do not show allergy-protective properties. This is likely because of structural differences because we were able to show by nuclear magnetic resonance spectroscopy that although they are predominantly composed of arabinose and galactose, the molecules differ in structure. CONCLUSIONS: The authors conclude that grass arabinogalactans are important immunomodulatory substances that contribute to the protection from allergic airway inflammation, airway hyperresponsiveness, and atopic sensitization in a mouse model of asthma.

T-cell polarization depends on concentration of the danger signal used to activate dendritic cells.

Although several studies have focused on allergic sensitization by dendritic cells, to date it is still open under which conditions these antigen-presenting cells are able to induce an allergic immune response. Our study reveals that BMDCs pulsed with LPS-free ovalbumine did not induce allergic disease. However, when BMDCs were activated with low-dose LPS during pulsing with allergen, these cells expressed an inflammatory set of cytokines and co-stimulatory molecules like CD86 and OX40L. Moreover, activated cells were able to prime mice for massive eosinophilic inflammation of the lung, airway hyper-reactivity, IgE production and production of Th2 cytokines by lymphocytes. Blocking experiments showed that expression of OX40L is not involved in induction of Th2 response. Interestingly, BMDCs that were activated with high dose of LPS lose their Th2-sensitizing capacity. Instead these cells induce a Th17 type immune response. We conclude that presentation of allergen by dendritic cells generated with GMCSF is not sufficient to lead to induction of allergic immune response. Further activation of BMDCs is required to prime mice for allergic immune response. In this study, we show that LPS is a suitable stimulus. However, when cells were activated with high dose LPS they tended to induce a Th17 response.

Safety and efficacy in children of an SQ-standardized grass allergen tablet for sublingual immunotherapy.

BACKGROUND: Immunotherapy with the SQ-standardized grass tablet Grazax is efficacious and well-tolerated in adult patients with rhinoconjunctivitis. Allergic asthma and rhinoconjunctivitis are closely linked, and a strategy combining treatment of the upper and lower airways is recommended. OBJECTIVE: To investigate the efficacy of treatment with the grass tablet on grass pollen-induced rhinoconjunctivitis and asthma as well as the immunologic response and the safety profile in children. METHODS: A total of 253 children age 5 to 16 years, with grass pollen-induced rhinoconjunctivitis with/without asthma, were randomized 1:1 to active treatment or placebo. Treatment was initiated 8 to 23 weeks before the start of the grass pollen season 2007 and continued throughout the entire season. Symptomatic medication was provided as relief medication to both groups in a stepwise fashion. Primary endpoints were rhinoconjunctivitis symptom and medication scores. RESULTS: The rhinoconjunctivitis symptom and medication scores and the asthma symptom score were all statistically significantly different between the 2 treatment groups. The differences in medians relative to placebo were 24%, 34%, and 64% in favor of active treatment. The immunologic response was similar to that observed in adults. The most common adverse reaction was oral pruritus, reported by 40 subjects (32%) in the active and 3 (2%) in the placebo group. Six subjects withdrew because of adverse events. No serious adverse events were assessed as treatment-related. CONCLUSION: Immunotherapy with the grass tablet reduced grass pollen-induced rhinoconjunctivitis and asthma symptoms in a pediatric population and introduced an immunomodulatory response, consistent with treatment of the underlying allergic disease. The treatment was well tolerated.

Animal shed Bacillus licheniformis spores possess allergy-protective as well as inflammatory properties.

BACKGROUND: Numerous epidemiologic studies have demonstrated an allergy-protective effect of farm life early in childhood. It has been hypothesized that environmental exposure to microbes may contribute to this effect. Because of their small size and thereby their potential for deposition in lower airways of small children, bacterial spores may be candidates for such allergy-protective effects. OBJECTIVE: To investigate immune responses elicited by exposure to Bacillus spores in experimental settings. METHODS: Animal shed and mattress dusts were analyzed for bacteria and fungi by aerobic and anaerobic growth. Bacillus licheniformis, the most prominent microorganism found in these samples, was investigated with respect to spore specific stimulation of pattern recognition receptors, monocyte-derived dendritic cells and T(H)-cell polarization in vitro as well as to the prevention of asthma development in a mouse model of allergic asthma. RESULTS: In vitro, B. licheniformis spores activated a T(H)1 cytokine expression profile. In vivo application of these spores resulted in less spore-specific but long-lasting immune activation preventing eosinophilia and goblet cell hyperplasia; however, they provoked an influx of neutrophils in lung tissue of asthmatic mice. CONCLUSION: Bacterial spores may contribute to the allergy-protective properties of farming environments, but their persistence in the lung causes ongoing immune activation in mouse experiments.