High exposure to endotoxin in farming is associated with less new-onset pollen sensitisation.

OBJECTIVES: Little is known about risk factors for new onset and loss of atopic sensitisation in adulthood. The aim is to examine the longitudinal effect of quantitatively assessed endotoxin exposures on changes in specific allergen sensitisation in young adults. METHODS: The cohort consisted of 1113 young Danish farmers and rural controls, with a mean age of 19 years at baseline. Sensitisation to birch pollen, grass pollen, cat dander and house dust mite was measured by specific IgE levels in serum samples from baseline and at 15 years' follow-up. Changes in sensitisation were analysed in relation to cumulative endotoxin exposure during follow-up, considering early life farm exposure. RESULTS: Endotoxin exposure during follow-up was significantly associated with less new onset of specifically grass and birch pollen sensitisation. For the highest versus lowest quartile of cumulative endotoxin exposure, the OR for new-onset IgE sensitisation was 0.35 (0.13-0.91) for birch and 0.14 (0.05-0.50) for grass. On the other hand, loss of pollen sensitisation showed a positive, although mostly non-significant, association with increased levels of endotoxin exposure. Endotoxin exposure was not associated with significant changes in cat dander and house dust mite sensitisation. CONCLUSIONS: High exposure to endotoxin during young adulthood appears to protect against new onset of pollen sensitisation, independent of childhood farm exposure.

Exposure to nonmicrobial N-glycolylneuraminic acid protects farmers' children against airway inflammation and colitis.

BACKGROUND: Childhood exposure to a farm environment has been shown to protect against the development of inflammatory diseases, such as allergy, asthma, and inflammatory bowel disease. OBJECTIVE: We sought to investigate whether both exposure to microbes and exposure to structures of nonmicrobial origin, such as the sialic acid N-glycolylneuraminic acid (Neu5Gc), might play a significant role. METHODS: Exposure to Neu5Gc was evaluated by quantifying anti-Neu5Gc antibody levels in sera of children enrolled in 2 farm studies: the Prevention of Allergy Risk factors for Sensitization in Children Related to Farming and Anthroposophic Lifestyle (PARSIFAL) study (n = 299) and the Protection Against Allergy Study in Rural Environments (PASTURE) birth cohort (cord blood [n = 836], 1 year [n = 734], 4.5 years [n = 700], and 6 years [n = 728]), and we associated them with asthma and wheeze. The effect of Neu5Gc was examined in murine airway inflammation and colitis models, and the role of Neu5Gc in regulating immune activation was assessed based on helper T-cell and regulatory T-cell activation in mice. RESULTS: In children anti-Neu5Gc IgG levels correlated positively with living on a farm and increased peripheral blood forkhead box protein 3 expression and correlated inversely with wheezing and asthma in nonatopic subjects. Exposure to Neu5Gc in mice resulted in reduced airway hyperresponsiveness and inflammatory cell recruitment to the lung. Furthermore, Neu5Gc administration to mice reduced the severity of a colitis model. Mechanistically, we found that Neu5Gc exposure reduced IL-17+ T-cell numbers and supported differentiation of regulatory T cells. CONCLUSIONS: In addition to microbial exposure, increased exposure to non-microbial-derived Neu5Gc might contribute to the protective effects associated with the farm environment.

Phenotypes of Atopic Dermatitis Depending on the Timing of Onset and Progression in Childhood.

Importance: Atopic dermatitis is an inflammatory, pruritic skin disease that often occurs in early infancy with a chronic course. However, a specific description of subtypes of atopic dermatitis depending on the timing of onset and progression of the disease in childhood is lacking. Objective: To identify different phenotypes of atopic dermatitis using a definition based on symptoms before age 6 years and to determine whether some subtypes are more at risk for developing other allergic diseases. Design, Setting, and Participants: The Protection Against Allergy Study in Rural Environments (PASTURE) is a European birth cohort where pregnant women were recruited between August 2002 and March 2005 and divided in 2 groups dependent on whether they lived on a farm. Children from this cohort with data on atopic dermatitis from birth to 6 years of age were included. Exposures: Atopic dermatitis, defined as an itchy rash on typical locations from birth to 6 years. Main Outcomes and Measures: The latent class analysis was used to identify subtypes of atopic dermatitis in childhood based on the course of symptoms. Multivariable logistic regressions were used to analyze the association between atopic dermatitis phenotypes and other allergic diseases. Results: We included 1038 children; of these, 506 were girls. The latent class analysis model with the best fit to PASTURE data separated 4 phenotypes of atopic dermatitis in childhood: 2 early phenotypes with onset before age 2 years (early transient [n = 96; 9.2%] and early persistent [n = 67; 6.5%]), the late phenotype with onset at age 2 years or older (n = 50; 4.8%), and the never/infrequent phenotype (n = 825; 79.5%), defined as children with no atopic dermatitis. Children with both parents with history of allergies were 5 times more at risk to develop atopic dermatitis with an early-persistent phenotype compared with children with parents with no history of allergies. Both early phenotypes were strongly associated with food allergy. The risk of developing asthma was significantly increased among the early-persistent phenotype (adjusted odds ratio, 2.87; 95% CI, 1.31-6.31). The late phenotype was only positively associated with allergic rhinitis. Conclusions and Relevance: Using latent class analysis, 4 phenotypes of atopic dermatitis were identified depending on the onset and course of the disease. The prevalence of asthma and food allergy by 6 years of age was strongly increased among children with early phenotypes (within age 2 years), especially with persistent symptoms. These findings are important for the development of strategies in allergy prevention.

Predictors of microbial agents in dust and respiratory health in the Ecrhs.

BACKGROUND: Dampness and mould exposure have been repeatedly associated with respiratory health. However, less is known about the specific agents provoking or arresting health effects in adult populations. We aimed to assess predictors of microbial agents in mattress dust throughout Europe and to investigate associations between microbial exposures, home characteristics and respiratory health. METHODS: Seven different fungal and bacterial parameters were assessed in mattress dust from 956 adult ECRHS II participants in addition to interview based home characteristics. Associations between microbial parameters and the asthma score and lung function were examined using mixed negative binomial regression and linear mixed models, respectively. RESULTS: Indoor dampness and pet keeping were significant predictors for higher microbial agent concentrations in mattress dust. Current mould and condensation in the bedroom were significantly associated with lung function decline and current mould at home was positively associated with the asthma score. Higher concentrations of muramic acid were associated with higher mean ratios of the asthma score (aMR 1.37, 95%CI 1.17-1.61). There was no evidence for any association between fungal and bacterial components and lung function. CONCLUSION: Indoor dampness was associated with microbial levels in mattress dust which in turn was positively associated with asthma symptoms.

Component-resolved diagnosis of baker's allergy based on specific IgE to recombinant wheat flour proteins.

BACKGROUND: Sensitization to wheat flour plays an important role in the development and diagnosis of baker's asthma. OBJECTIVES: We evaluated wheat allergen components as sensitizers for bakers with work-related complaints, with consideration of cross-reactivity to grass pollen. METHODS: Nineteen recombinant wheat flour proteins and 2 cross-reactive carbohydrate determinants were tested by using CAP-FEIA in sera of 101 bakers with wheat flour allergy (40 German, 37 Dutch, and 24 Spanish) and 29 pollen-sensitized control subjects with wheat-specific IgE but without occupational exposure. IgE binding to the single components was inhibited with wheat flour, rye flour, and grass pollen. The diagnostic efficiencies of IgE tests with single allergens and combinations were evaluated by assessing their ability to discriminate between patients with baker's allergy and control subjects based on receiver operating characteristic analyses. RESULTS: Eighty percent of bakers had specific IgE levels of 0.35 kUA/L or greater and 91% had specific IgE levels of 0.1 kUA/L or greater to at least one of the 21 allergens. The highest frequencies of IgE binding were found for thiol reductase (Tri a 27) and the wheat dimeric α-amylase inhibitor 0.19 (Tri a 28). Cross-reactivity to grass pollen was proved for 9 components, and cross-reactivity to rye flour was proved for 18 components. A combination of IgE tests to 5 components, Tri a 27, Tri a 28, tetrameric α-amylase inhibitor CM2 (Tri a 29.02), serine protease inhibitor-like allergen (Tri a 39), and 1-cys-peroxiredoxin (Tri a 32), produced the maximal area under the curve (AUC = 0.84) in receiver operating characteristic analyses, but this was still lower than the AUC for wheat- or rye flour-specific IgE (AUC = 0.89 or 0.88, respectively). CONCLUSIONS: Component-resolved diagnostics help to distinguish between sensitization caused by occupational flour exposure and wheat seropositivity based on cross-reactivity to grass pollen. For routine diagnosis of baker's allergy, however, allergen-specific IgE tests with whole wheat and rye flour extracts remain mandatory because of superior diagnostic sensitivity.

Early exposure to bio-contaminants and asthma up to 10 years of age: results of the HITEA study.

Inverse associations have been found between exposure to bio-contaminants and asthma and allergies. The aim of this study was to prospectively assess whether early exposure to bio-contaminants in dust is associated with asthma and allergy later in childhood among children from (sub)-urban areas. In subsets of three European birth cohorts (PIAMA: n=553; INMA: n=481; and LISAplus: n=395), endotoxin, (1,3,)-ß-d-glucan and extracellular polysaccharide were measured in dust from living rooms shortly after birth. Current asthma at 6 years and 10 years of age and ever asthma up to 10 years of age were assessed by parental questionnaires. Specific IgE levels at 8 years (PIAMA) and 10 years (LISAplus) were available. Adjusted, cohort-specific logistic regression analyses were performed. Higher endotoxin concentrations were positively associated with current asthma at 6 years of age in PIAMA (adjusted OR 1.96, 95% CI 1.07-3.58), but were inversely related with ever asthma up to 10 years of age in INMA (adjusted OR 0.39, 95% CI 0.16-0.94). No associations with asthma were found for LISAplus. No associations were observed with atopic sensitisation in all cohorts. All associations with (1,3)-ß-d-glucan and extracellular polysaccharide were statistically nonsignificant. The suggested immunological mechanisms of early exposure to bio-contaminants with regards to asthma and allergy might be different for children growing up in (sub)-urban environments.

Dampness, bacterial and fungal components in dust in primary schools and respiratory health in schoolchildren across Europe.

BACKGROUND: Respiratory health effects of damp housing are well recognised, but less is known about the effect of dampness and water damage in schools. The HITEA study previously reported a higher prevalence of respiratory symptoms in pupils from moisture damaged schools, but the role of specific microbial exposures remained unclear. OBJECTIVES: To study associations between school dampness, levels of fungal and bacterial markers, respiratory symptoms and lung function in children. METHODS: Primary schools in Spain, the Netherlands and Finland were selected on the basis of the observed presence (n=15) or absence (n=10) of moisture, dampness and/or mould. Settled dust was repeatedly sampled in 232 classrooms and levels of 14 different microbial markers and groups of microbes were determined. Parental reports of respiratory symptoms were available from 3843 children aged 6-12 years, of whom 2736 provided acceptable forced spirometry testing. Country-specific associations between exposure and respiratory health were evaluated by multilevel mixed-effects logistic and linear regression models and combined using random-effects meta-analysis. RESULTS: The prevalence of respiratory symptoms was higher in moisture damaged schools, being more pronounced in Finnish pupils. Effects on lung function were not apparent. Levels of microbial markers were generally higher in moisture damaged schools, varied by season and were lower in Finnish schools. Wheeze tended to be inversely associated with microbial levels. All other respiratory symptoms were not consistently associated with microbial marker levels. CONCLUSIONS: Health effects of moisture and microbial exposures may vary between countries, but this requires further study.

Daily changes of peak expiratory flow and respiratory symptom occurrence around a soy processing factory.

OBJECTIVES: To evaluate sensitization and acute respiratory health effects in inhabitants living in the vicinity of a factory producing soy oil. METHODS: Two panels of potential responders were created on the basis of a response to a short screening questionnaire sent to random samples of 1,000 exposed and 1,000 non-exposed individuals living around the factory and a control area. Individuals responding to the questionnaire were invited for a medical evaluation, including a respiratory symptom questionnaire and skin prick testing, for a panel of common allergens and a soy allergen extract. This resulted in 53 atopic and/or asthmatic inhabitants from the area surrounding the factory and 30 comparable control subjects. In these subjects, morning and evening Peak Expiratory Flow (PEF), respiratory symptoms and medication use were recorded daily during a 10-week period in the autumn. At the same time, soy allergen and endotoxin concentrations were determined in airborne dust in the exposed and the control area. The wind direction relative to the location of a subjects' house and the factory was used to determine whether an individual was exposed on a particular day. RESULTS: Only few of the atopic subjects were sensitized to soy. PEF showed a decrease, respiratory symptoms and bronchodilator use, an increase among soy sensitized subjects after having been downwind from the factory. Airborne soy allergen was found more frequently in the area surrounding the factory and levels were higher than in the control area. Highest levels were found on the factory premises. Only a weak association was found with wind direction. Airborne endotoxin concentrations did not show a consistent pattern with distance, but levels were clearly higher on the factory premises. CONCLUSION: Sensitization to soy allergen was not increased among the population sample living in the vicinity of the factory. Soy sensitized individuals living in the surroundings of the factory reported more respiratory symptoms, used bronchodilators more often and had a lower PEF after having been downwind of the factory.

Exhaled nitric oxide in spray painters exposed to isocyanates: effect modification by atopy and smoking.

BACKGROUND: Isocyanate asthma is one of the most frequently identified forms of occupational asthma in industrialised countries. The underlying mechanisms have not been clarified. There is only limited information about the relationship between exhaled nitric oxide (eNO) and occupational exposure to isocyanates and asthma. OBJECTIVES: To investigate the association between isocyanate exposure and eNO levels in isocyanate-exposed workers and to elucidate whether eNO acts as a marker of airway inflammation controlling for smoking and atopy in an industry-wide survey. METHODS: Information on estimated personal isocyanate exposure, measured eNO levels, health effects and sensitisation were analysed in 229 workers from a cross-sectional study. Univariate and multiple regression analyses were used to explore the exposure-response relationships between isocyanate exposure and eNO, stratified by smoking and atopy. RESULTS: A marginally significant exposure-response relationship was found between isocyanate exposure and eNO in atopic, non-smokers (p=0.054). eNO was significantly associated with atopy and smoking, bronchial hyper-responsiveness (BHR), work-related conjunctivitis and rhinitis after adjustment for age, gender, atopy and smoking (p<0.05). A borderline significant association was found between eNO and asthma-like symptoms after adjustment for age, gender, atopy and current smoking (p=0.055). In a small group of isocyanate-exposed workers with positive serum-specific immunoglobulin E (IgE) antibodies to hexamethylene diisocyanate (HDI), elevated eNO levels were clearly exposure related. eNO was associated with the positive specific IgG antibodies to HDI in non-atopic, non-smokers (p=0.03). CONCLUSIONS: Increased eNO levels may indicate increased airway inflammation in atopic, non-smokers exposed to isocyanates especially at higher levels of isocyanate exposure.

Expression of genes related to anti-inflammatory pathways are modified among farmers' children.

BACKGROUND: The hygiene hypothesis states that children exposed to higher loads of microbes such as farmers' children suffer less from allergies later in life. Several immunological mechanisms underpinning the hygiene hypothesis have been proposed such as a shift in T helper cell balance, T regulatory cell activity, or immune regulatory mechanisms induced by the innate immunity. OBJECTIVE: To investigate whether the proposed immunological mechanisms for the hygiene hypotheses are found in farmers' children. METHODS: We assessed gene expression levels of 64 essential markers of the innate and adaptive immunity by quantitative real-time PCR in white blood cells in 316 Swiss children of the PARSIFAL study to compare farmers' to non-farmers' expressions and to associate them to the prevalence of asthma and rhinoconjunctivitis, total and allergen-specific IgE in serum, and expression of Cε germ-line transcripts. RESULTS: We found enhanced expression of genes of the innate immunity such as IRAK-4 and RIPK1 and enhanced expression of regulatory molecules such as IL-10, TGF-ß, SOCS4, and IRAK-2 in farmers' children. Furthermore, farmers' children expressed less of the TH1 associated cytokine IFN-γ while TH2 associated transcription factor GATA3 was enhanced. No significant associations between the assessed immunological markers and allergic diseases or sensitization to allergens were observed. CONCLUSION: Farmers' children express multiple increased innate immune response and immune regulatory molecules, which may contribute to the mechanisms of action of the hygiene hypothesis.

Rule-based models of the interplay between genetic and environmental factors in childhood allergy.

Both genetic and environmental factors are important for the development of allergic diseases. However, a detailed understanding of how such factors act together is lacking. To elucidate the interplay between genetic and environmental factors in allergic diseases, we used a novel bioinformatics approach that combines feature selection and machine learning. In two materials, PARSIFAL (a European cross-sectional study of 3113 children) and BAMSE (a Swedish birth-cohort including 2033 children), genetic variants as well as environmental and lifestyle factors were evaluated for their contribution to allergic phenotypes. Monte Carlo feature selection and rule based models were used to identify and rank rules describing how combinations of genetic and environmental factors affect the risk of allergic diseases. Novel interactions between genes were suggested and replicated, such as between ORMDL3 and RORA, where certain genotype combinations gave odds ratios for current asthma of 2.1 (95% CI 1.2-3.6) and 3.2 (95% CI 2.0-5.0) in the BAMSE and PARSIFAL children, respectively. Several combinations of environmental factors appeared to be important for the development of allergic disease in children. For example, use of baby formula and antibiotics early in life was associated with an odds ratio of 7.4 (95% CI 4.5-12.0) of developing asthma. Furthermore, genetic variants together with environmental factors seemed to play a role for allergic diseases, such as the use of antibiotics early in life and COL29A1 variants for asthma, and farm living and NPSR1 variants for allergic eczema. Overall, combinations of environmental and life style factors appeared more frequently in the models than combinations solely involving genes. In conclusion, a new bioinformatics approach is described for analyzing complex data, including extensive genetic and environmental information. Interactions identified with this approach could provide useful hints for further in-depth studies of etiological mechanisms and may also strengthen the basis for risk assessment and prevention.

Interaction between retinoid acid receptor-related orphan receptor alpha (RORA) and neuropeptide S receptor 1 (NPSR1) in asthma.

Retinoid acid receptor-related Orphan Receptor Alpha (RORA) was recently identified as a susceptibility gene for asthma in a genome-wide association study. To investigate the impact of RORA on asthma susceptibility, we performed a genetic association study between RORA single nucleotide polymorphisms (SNPs) in the vicinity of the asthma-associated SNP (rs11071559) and asthma-related traits. Because the regulatory region of a previously implicated asthma susceptibility gene, Neuropeptide S receptor 1 (NPSR1), has predicted elements for RORA binding, we hypothesized that RORA may interact biologically and genetically with NPSR1. 37 RORA SNPs and eight NPSR1 SNPs were genotyped in the Swedish birth cohort BAMSE (2033 children) and the European cross-sectional PARSIFAL study (1120 children). Seven RORA SNPs confined into a 49 kb region were significantly associated with physician-diagnosed childhood asthma. The most significant association with rs7164773 (T/C) was driven by the CC genotype in asthma cases (OR = 2.0, 95%CI 1.36-2.93, p = 0.0003 in BAMSE; and 1.61, 1.18-2.19, p = 0.002 in the combined BAMSE-PARSIFAL datasets, respectively), and strikingly, the risk effect was dependent on the Gln344Arg mutation in NPSR1. In cell models, stimulation of NPSR1 activated a pathway including RORA and other circadian clock genes. Over-expression of RORA decreased NPSR1 promoter activity further suggesting a regulatory loop between these genes. In addition, Rora mRNA expression was lower in the lung tissue of Npsr1 deficient mice compared to wildtype littermates during the early hours of the light period. We conclude that RORA SNPs are associated with childhood asthma and show epistasis with NPSR1, and the interaction between RORA and NPSR1 may be of biological relevance. Combinations of common susceptibility alleles and less common functional polymorphisms may modify the joint risk effects on asthma susceptibility.

Early life exposures to home dampness, pet ownership and farm animal contact and neuropsychological development in 4 year old children: a prospective birth cohort study.

Exposure to biocontaminants is associated with behavioural problems and poorer cognitive function. Our study assesses the associations between early life exposure to home dampness, pets and farm animal contact and cognitive function and social competences in 4-year old children, and the associations between these indoor factors and microbial compounds (bacterial endotoxin and fungal extracellular polysaccharides). A Spanish population-based birth-cohort enrolled 482 children, and 424 of them underwent psychometric testing at 4 years of age, including the McCarthy Scales of Child Abilities (MSCA) and the California Preschool Social Competence Scale (CPSCS). Information on pet ownership, farm animal contact and home dampness was periodically reported by the parents through questionnaires. Microbial compounds were measured in living room sofa dust collected at the age of 3 months. Persistent home dampness during early life significantly decreased the general score of MSCA by 4.9 points (95% CI: -8.9; -0.8), and it decreased the CPSCS by 6.5 points (95% CI: -12.2; -0.9) in the child's bedroom. Cat or dog ownership were not associated with the outcomes, but occasional farm animal contact increased the general cognitive score of MSCA by 5.6 points (95% CI: 1.8; 9.3). Cat and dog ownership were associated with higher levels of endotoxins in home dust. None of the measured microbial compounds were related with the psychometric tests scores. In conclusion, damp housing in early life may have adverse effects on neuropsychological development at 4 years old. More research is needed to explore the possible involvement of mycotoxins in the observed results.

Skin symptoms in bakery and auto body shop workers: associations with exposure and respiratory symptoms.

PURPOSE: Despite the importance of skin exposure, studies of skin symptoms in relation to exposure and respiratory symptoms are rare. The goals of this study were to describe exposure-response relationships for skin symptoms, and to investigate associations between skin and respiratory symptoms in bakery and auto body shop workers. METHODS: Data from previous studies of bakery and auto body shop workers were analyzed. Average exposure estimates for wheat allergen and isocyanates were used. Generalized linear models were constructed to describe the relationships between exposure and skin symptoms, as well as between skin and respiratory symptoms. RESULTS: Data from 723 bakery and 473 auto body shop workers were analyzed. In total, 5.3% of bakery and 6.1% of auto body shop workers were female; subjects' mean age was 39 and 38 years, respectively. Exposure-response relationships were observed in auto body shop workers for itchy or dry skin (PR 1.55, 95% CI 1.2-2.0) and work-related itchy skin (PR 1.97, 95% CI 1.2-3.3). A possible exposure-response relationship for work-related itchy skin in bakery workers did not reach statistical significance. In both groups, reporting skin symptoms was strongly and significantly associated with reporting respiratory symptoms, both work-related and non-work-related. CONCLUSIONS: Exposure-response relationships were observed for skin symptoms in auto body shop workers. The lack of significant exposure-response associations in bakery workers should be interpreted cautiously. Workers who reported skin symptoms were up to four times more likely to report respiratory symptoms. Improved awareness of both skin and respiratory outcomes in exposed workers is needed.

Comparison of the potency of a variety of ß-glucans to induce cytokine production in human whole blood.

ß-Glucans are components of fungal cell walls and potent stimulants of innate immunity. The majority of research on biological activities of glucans has focused on ß-(1→3)-glucans, which have been implicated in relation to fungal exposure-associated respiratory symptoms and as important stimulatory agents in anti-fungal immune responses. Fungi-and bacteria and plants-produce a wide variety of glucans with vast differences in the proportion and arrangement of their ß-(1→3)-, -(1→4)- and -(1→6)-glycosidic linkages. Thus far, the pro-inflammatory potential of different ß-glucans has not been studied within the same experimental model. Therefore, we compared the potency of 13 different glucan preparations to induce in vitro production of IL-1ß, IL-6, IL-8 and TNF-α in human, whole blood cultures. The strongest inducers of all cytokines were pustulan [ß-(1→6)-glucan], lichenan [ß-(1→3)-(1→4)-glucan], xyloglucan [ß-(1→4)-glucan] and pullulan [α-(1→4)-(1→6)-glucan]. Moderate-to-strong cytokine production was observed for curdlan [ß-(1→3)-glucan], baker's yeast glucan [ß-(1→3)-(1→6)-glucan] and barley glucan [ß-(1→3)-(1→4)-glucan], while all other glucan preparations induced very low, or no, detectable levels of cytokines. We therefore conclude that innate immunity reactions are not exclusively induced by ß-(1→3)-glucans, but also by ß-(1→6)- and ß-(1→4)-structures. Thus, not only ß-(1→3)-glucan, but also other ß-glucans and particularly ß-(1→6)-glucans should be considered in future research.

IgG to various beta-glucans in a human adult population.

BACKGROUND: Fungal ß-(1,3)-glucans are pro-inflammatory agents, and exposures to ß-(1,3)-glucans are associated with respiratory tract symptoms. IgG anti-(1,3)-glucan titers are measured in diagnosis of fungal infections. Although other ß-glucan structures exist, like ß-(1,6)-glucans, little is known about their antigenic or pro-inflammatory properties. We aimed to investigate IgG titers and specificities in human sera against different ß-glucans with varying structures. METHODS: IgG anti-ß-glucan was measured by enzyme immunoassay in a random sample of 40 sera from healthy adults, with a panel of 8 differently structured glucans. In a subsequent larger series, IgG anti-ß-(1,6)-glucan was measured in a random sample of 667 sera from three occupational populations with different organic dust exposures. Possible determinants of IgG anti-ß-(1,6)-glucan titers were explored with linear-regression analysis. RESULTS: We found wide variation in anti-ß-glucan IgG levels. The highest titers were found for pure ß-(1,6)-glucan pustulan. Moderate to strong reactions with other ß-(1,6)-containing structures appeared to be due to cross-reacting anti-ß-(1,6)-glucan antibodies. Surprisingly, the mean IgG anti-ß-(1,6)-glucan titer was significantly lower in agricultural workers - with highest organic dust exposure - than in spray painters and bakery workers. Smoking status was associated with lower IgG anti-ß-(1,6)-glucan titers in all populations. CONCLUSIONS: IgG to ß-(1,3)- and ß-(1,6)-glucans can be found in normal human sera. ß-(1,6)-glucans appear to be much more potent antigens. The health impact of high anti-ß-(1,6)-glucan antibody levels remains unclear and further investigations are needed.

Health effects of selected microbiological control agents. A 3-year follow-up study.

INTRODUCTION AND OBJECTIVES: Microbiological control agents (MBCA) are widely used in greenhouses, replacing chemical pesticides. The presented study aims to describe health effects of exposure to three types commonly used: Bacillus thuringiensis, Verticillium lecanii, and Trichoderma harzenianum covering seven different products in greenhouse workers with emphasis on sensitization and respiratory effects. METHODS: 579 persons aged 17-67 years culturing ornamental flowers were included. They were followed for three years with annual examinations including interview about exposure and symptoms, lung function, including bronchial (histamine) challenge test, and blood samples. Direct and indirect exposure for each person and year was estimated by information from respondents and employers. IgE in serum against the 7 products of MCBA was analyzed using an enzyme immunoassay technique. RESULTS: 65%, 40%, and 78% were exposed to B. thuringiensis, V. lecanii, and T. harzenianum, respectively, while 6, 3 and 3% were handling the products. IgE against B. thuringiensis was seen in 53% of the samples and with prevalence rate ratios among exposed increasing from 1.20 (CI95%:1.01-1.42) to 1.43 (CI95%:1.09-1.87) over the 3-year period. There was no relation between exposure to any MBCA and neither prevalence nor incidence of respiratory symptoms and there was no effect on lung function or bronchial responsiveness. CONCLUSIONS: Use of B. thuringiensis in greenhouses may give rise to sensitization while no effect on the occurrence of respiratory symptoms or lung function was observed. The persons had a relatively long exposure. Therefore, a healthy worker effect may have influenced the results.