G. Doekes

Validation of a screening questionnaire for atopy with serum IgE tests in a population of pregnant Dutch women

We have started a large birth cohort study in which pregnant women with and without atopy are differentially included. In view of the large number of subjects to be screened (12u2003000), a simple questionnaire was developed for the assessment of atopy in pregnant women.

Upper airway inflammation assessed by nasal lavage in compost workers: A relation with bio-aerosol exposure

BACKGROUNDnExposure to microbial agents in the composting industry may cause work related airway inflammation. Nasal lavage (NAL) has been proposed as a noninvasive method to assess such effects in population studies.nnnMETHODSnPre- and post-shift NAL were performed in the workers of a compost plant visited in 1995 (n = 14) and 1996 (n=15), of whom only four participated in both surveys. Total cells, cytokines and other inflammation markers were measured in NAL fluid, and pre-shift levels and post/pre concentration ratios were compared with NAL results obtained in the same periods in 10 and 9 controls, respectively, and with levels of airborne exposure to microbial agents endotoxin and beta(1,3)-glucan as measured in personal air samples.nnnRESULTSnJob-title specific exposure levels in the first survey ranged from 75 to 527 EU/m(3) for endotoxin and from 0.54 to 4.85 microg/m(3) for beta(1,3)-glucan. In the second survey these values were lower, 29-285 EU/m(3) and 0.36-4.44 microg/m(3), respectively. In the first survey pre-shift NAL concentrations of total cells, MPO, IL-8, NO and albumin were significantly (1.1-4.8 fold) higher in compost workers than in controls. Post/pre ratios for various markers were significantly (1.2-3.2 fold) higher in compost workers in both surveys. NAL cells were mainly neutrophils, while eosinophils were only incidentally observed. A weak relation with exposure was found for pre-shift levels of MPO, uric acid and urea in the first survey.nnnCONCLUSIONSnOccupational exposure of compost workers may cause acute and possibly (sub-)chronic inflammatory reactions in the upper airways, presumably induced by non-allergenic pro-inflammatory agents like endotoxins and beta(1, 3)-glucans.

Enzyme immunoassays for total and allergen specific IgE in population studies.

OBJECTIVE--Extensive IgE serology in occupational or environmental health studies is often hampered by a lack of technical facilities and finance. The use in population studies of relatively simple and inexpensive enzyme immunoassays (EIAs) was therefore evaluated for the assessment of total serum immunoglobulin E (IgE), and of specific IgE reactions with various common (house dust mites, grass and birch pollen, and cat) or occupational (fungal alpha-amylase and rat urinary protein) allergens. METHODS--Total IgE was measured with a sandwich EIA, calibrated with commercially available IgE standards. Reproducibility was studied by testing pooled normal human serum samples in each of a large series of test plates. A panel of 156 childrens serum samples with known IgE values was used to compare the assay with other total IgE assays. A previously developed EIA for anti-yeast IgE was adapted for the measurement of IgE reacting with various common and occupational allergens. Binding of IgE to microwells coated with commercially available allergen extracts, or allergen preparations from our own laboratory, was measured with a monoclonal anti-human IgE antibody and subsequent incubations with biotinylated rabbit anti-mouse Ig and avidin-peroxidase. Panels of serum samples from school children (n = 116), bakery workers (n = 126), and laboratory animal workers (n = 52) were used to study sensitivity and specificity, with reference to skin prick tests as the standard, and to compare the EIAs with commercially available test kits. RESULTS--The detection limit of the EIA for total IgE was 0.5-1 kU/l for undiluted serum samples, and the coefficient of variation between assays was less than 15% at serum concentrations between 1 and 150 kU/l. Results obtained with the panel of 156 childrens serum samples were strongly correlated (r2 = 0.86) with IgE concentrations measured previously by radioimmunoassay. The results of the EIA for various occupational allergens correlated very well, both qualitatively and quantitatively, with the results of commercial test kits. Sensitivity and specificity of the EIA results as a predictor of skin prick test reactivity towards common allergens (house dust mite, grass pollen, birch pollen, and cat) were remarkably high (> 80%-90%) in the series of 116 childrens serum samples. In a population of bakery workers the specificity of the EIAs was also very high (> 90%). The sensitivity was notably lower (30%-70%) in this adult population, which is, however, in agreement with results reported for conventional IgE tests. CONCLUSION--As the costs were estimated to be at least five to 10-fold lower than those of commercial test kits, the EIAs for total and specific IgE may be very useful tools in epidemiological studies of atopic respiratory or other disorders.

Der p I concentrations in mattress surface and floor dust collected from infants' bedrooms.

Background Allergen exposure in early childhood is thought to be important for sensitization and subsequent development of asthma. Not much is known, however, about exposure of young children to allergens in the home.

Occupational IgE sensitisation to phytase, a phosphatase derived from Aspergillus niger

OBJECTIVE: Phytase is a phosphatase derived from Aspergillus niger that enhances phosphate bioavailability in the gut, and therefore has been increasingly used as an animal feed additive since the early 1990s. The aim of this study was to assess whether work related respiratory symptoms among workers in a so called premix factory producing animal feed additives, could be due to type I (mediated by immunoglobulin E (IgE) allergic sensitisation to phytase. METHODS: Preparations of specific IgE against phytase as used in the factory were assessed by enzyme immunoassay (EIA) in serum samples of 11 exposed workers who regularly handled the enzyme, in 11 office and laboratory workers of the same plant (non-exposed internal controls), and in 19 laboratory animal workers as external controls. The factory workers also completed a questionnaire on common and work related respiratory symptoms. RESULTS: Depending on the cut off level in the EIA for IgE, and the preparation used as coated allergen, antiphytase sensitisation was found in one to four of the 19 external controls, in one to five of the 11 internal controls, and in four to 10 of the 11 exposed workers. Strongest IgE reactions were found in four exposed workers who reported work related respiratory symptoms, particularly wheezing, and in one internal control who possibly had become sensitised because the structure of the factory building did not preclude airborne exposure in the offices and corridors of the plant. Experiments with inhibition EIA for IgE showed that (a) phytase of another commercial source was only partially cross reactive with phytase as used in the premix factory, and (b) phytase used as an animal feed additive did not cross react with common mould extracts, except for extracts from the species of origin, Aspergillus niger. The amount of IgE binding phytase in Aspergillus niger was estimated to be between 0.1% and 1% of the extractable mould proteins. CONCLUSIONS: Phytase is a potentially important new occupational allergen causing specific IgE immune responses among exposed workers. Such IgE sensitisation could probably be the cause of work related asthmatic and other respiratory symptoms if no effective measures are taken to prevent airborne occupational exposure at sites where phytase is handled, particularly during addition of enzyme preparations to animal feed.

Infant respiratory symptoms in relation to mite allergen exposure.

The relationship between the Dermatophagoides pteronyssinus (Der p) I content of house dust and the respiratory symptoms reported for young infants was studied. One hundred and four infants, aged 3-15 months, were selected during July-September 1993 through the Dutch postnatal health care service, using a short screening questionnaire to identify mothers with respiratory allergy to house dust and/or pets. Forty-eight were selected from this group of mothers (high risk infants) and 56 infants were selected when neither of the parents reported allergy or chronic respiratory symptoms (low risk infants). All homes were visited in October 1993. Dust samples were collected from the infants mattress and from other places in the home, and the Der p I content was measured in dust extracts. The results indicate that on more than half of the mattresses, the Der p I level was over 2,000 ng.g-1, the level suggested to be associated with an increased risk of sensitization. Information on respiratory symptoms (wheeze and prolonged cough) experienced since birth was obtained by questionnaire from one of the parents on the dust sampling day. The occurrence of respiratory symptoms in the infants appeared to be positively related to the Der p I concentration of the dust. Although no objective measurements of respiratory symptoms were available, the results of this study suggest that exposure to mite allergen in early life may lead to respiratory symptoms that are suggestive of airway obstruction in the first year of life.

Early indoor microbial exposure lowers the risk of asthma: The PIAMA birth cohort study

Early life exposures to microbial agents such as bacterial endotoxin have been suggested to inhibit the development of atopy and asthma. In this study we assessed the relation between living room floor levels of bacterial endotoxin, fungal β(1,3)-glucan and fungal extracellular polysaccharides (EPS-Pen/Asp) and the development of atopic sensitisation and asthma in 810 infants born from allergic parents. Exposure to microbial agents was determined at 3 months, serum IgE at 12 and 24 months, and asthma symptoms & diagnosis at 12, 24, and 48 months. Low, medium and high exposure groups were defined based on tertiles of the exposure distributions. Analyses were adjusted for gender, pets, ETS, siblings, parental education, and mite allergen levels. Microbial exposure was inversely associated with atopic sensitization at 24 months in a dose dependent manner with ORs ranging from 0.3–0.5 for the highest exposure groups (statistically significant only for EPS-Pen/Asp). A similar but weaker dose response was observed for atopy at 12 months. A doctors diagnosis of asthma at 48 months was also less common in highly exposed children with ORs ranging from 0.3–0.5, statistically significant (p < 0.01) for endotoxin and EPS. A protective effect in the medium exposure group was also observed but the effect was less pronounced suggesting a dose-response effect. These protective effects on doctors diagnosed asthma were shown consistently across the three time points, but were statistically significant only at 24 and 48 months. Interestingly, the protective effects of microbial exposure were observed both in atopic and non-atopic asthmatics. Asthma symptoms (wheeze and night cough) in the last 12 months (at age 4) were slightly less prevalent in the high exposure groups (NS). No associations were found for eczema. Endotoxin, EPS-Pen/Asp, and glucan concentrations were highly correlated limiting the potential to study them separately. In conclusion, although our findings need confirmation at older ages, they provide, for the first time, evidence from a prospective cohort study that non-infectious microbial exposure at a very young age may protect from developing atopy and asthma.