Comparison of methods to assess airborne rat and mouse allergen levels. I. Analysis of air samples

Bovine Allergens in a Ruminant Clinic and Dairy Barns: Exposure Levels, Determinants, and Variability

Background

Dairy farmers may develop specific sensitization and allergic airway diseases due to bovine allergens. However, dose-response relationships are lacking, and as yet little is known on bovine allergen exposure levels.

Objective

To investigate bovine allergen exposure levels in a ruminant clinic and dairy barns, and to assess exposure determinants and variability of exposure.

Methods

Samples were collected using active and passive airborne dust measurements in a ruminant clinic and several dairy barns. Bovine allergen levels were determined by sandwich enzyme-linked immunosorbent assay. Linear mixed models were applied to explore the association between bovine allergen exposure levels and potential exposure determinants. Day-to-day within-worker and between-worker exposure variability was determined, as well as how exposure determinants affect exposure variability.

Results

Bovine allergens were measureable in all samples. Personal bovine allergen exposure levels in the ruminant clinic ranged from 0.10 to 24.8 µg/m3, geometric mean (GM) 1.34 µg/m3. Exposure levels varied dependent on job titles. Personal exposure levels in dairy barns ranged from 0.10 to 46.8 µg/m3, GM 1.47 µg/m3. Type of bedding materials in the barns appeared to be a significant determinant of bovine allergen levels. Compost bedding, particularly, increased allergen levels. Milking by robot was the most important determinant explaining between-worker exposure variability, while bedding was important as well. Bovine allergen levels in stationary measurements were somewhat lower than personal measurements (GM ratio 0.47). Bovine allergens could be readily detected in electrostatic dust-fall collector measurements.

Conclusion

This study provides insight in bovine allergen exposure levels and their determinants, which is a first step to investigate dose-response relationships between sensitization/allergy associated with exposure to bovine allergen levels in future studies.

Characterization and epitope identification of the T cell response in non-allergic individuals exposed to mouse allergen

Background

Exposure to airborne allergens is a frequent trigger of respiratory allergy and asthma in atopic individuals. While allergic patients suffer hypersensitivity reactions to these allergens, non-allergic individuals do not exhibit clinical symptoms despite environmental exposure to these ubiquitous allergen sources. The aim of this study was to characterize T cell responses in non-allergic laboratory workers, who are heavily exposed to mice allergens (Exposed Non-Allergics, ENA) and compare this data to previously published T cell responses measured in mouse (MO)-allergic patients. METHODS: Peripheral mononuclear cells (PBMC) from ENA subjects were expanded for 2 weeks in vitro with mouse urine extract and screened for IFNγ and IL-5 cytokine production in response to mouse antigen-derived peptides by ELISPOT. Ex vivo T cell reactivity in the ENA cohort was performed after 6hr stimulation with peptide pools by intracellular staining of CD154.

Results

Vigorous responses were detected, associated with 147 epitopes derived from 16 mouse antigens. As expected, responses in ENA subjects were somewhat lower than those observed in MO-allergics for both responder frequency and overall response magnitude. While responses in allergics were polarized towards IL-5 production and associated with low IFNγ production, ENA responses were not polarized. The composition of targeted antigens and epitopes was overall similar between the two cohorts, with the majority of T cell reactivity directed against Mus m 1 and other major urinary proteins. However, kappa-casein precursor and odorant binding protein Ib were more abundantly recognized in MO-allergics compared to ENA subjects. Additionally, T cell responses against oligopeptides derived from the low molecular weight fraction of mouse urine were also assessed. Interestingly, no difference in the response frequency, magnitude or polarization between MO-allergic and ENA individuals was observed. Finally, assessment of ex vivo T cell activation also revealed T cell reactivity in the ENA cohort, with a non-significant trend for lower responses compared to MO-allergics.

Conclusion

Exposure to mouse induces potent T cell responses in non-allergic individuals, targeting similar epitopes as seen in allergic patients.

Allergen and Epitope Targets of Mouse-Specific T Cell Responses in Allergy and Asthma

Mouse allergy has become increasingly common, mainly affecting laboratory workers and inner-city households. To date, only one major allergen, namely Mus m 1, has been described. We sought to identify T cell targets in mouse allergic patients. PBMC from allergic donors were expanded with either murine urine or epithelial extract and subsequently screened for cytokine production (IL-5 and IFNγ) in response to overlapping peptides spanning the entire Mus m 1 sequence, peptides from various Mus m 1 isoforms [major urinary proteins (MUPs)], peptides from mouse orthologs of known allergens from other mammalian species and peptides from proteins identified by immunoproteomic analysis of IgE/IgG immunoblots of mouse urine and epithelial extracts. This approach let to the identification of 106 non-redundant T cell epitopes derived from 35 antigens. Three major T cell-activating regions were defined in Mus m 1 alone. Moreover, our data show that immunodominant epitopes were largely shared between Mus m 1 and other MUPs even from different species, suggesting that sequence conservation in different allergens is a determinant for immunodominance. We further identified several novel mouse T cell antigens based on their homology to known mammalian allergens. Analysis of cohort-specific T cell responses revealed that rhinitis and asthmatic patients recognized different epitope repertoires. Epitopes defined herein can be formulated into an epitope "megapool" used to diagnose mouse allergy and study mouse-specific T cell responses directly ex vivo. This analysis of T cell epitopes provides a good basis for future studies to increase our understanding of the immunopathology associated with MO-allergy and asthma.

Monitoring of occupational and environmental aeroallergens-- EAACI Position Paper. Concerted action of the EAACI IG Occupational Allergy and Aerobiology & Air Pollution

Exposure to high molecular weight sensitizers of biological origin is an important risk factor for the development of asthma and rhinitis. Most of the causal allergens have been defined based on their reactivity with IgE antibodies, and in many cases, the molecular structure and function of the allergens have been established. Significant information on allergen levels that cause sensitization and allergic symptoms for several major environmental and occupational allergens has been reported. Monitoring of high molecular weight allergens and allergen carrier particles is an important part of the management of allergic respiratory diseases and requires standardized allergen assessment methods for occupational and environmental (indoor and outdoor) allergen exposure. The aim of this EAACI task force was to review the essential points for monitoring environmental and occupational allergen exposure including sampling strategies and methods, processing of dust samples, allergen analysis, and quantification. The paper includes a summary of different methods for sampling and allergen quantification, as well as their pros and cons for various exposure settings. Recommendations are being made for different exposure scenarios.

Performance of the halogen immunoassay to assess airborne mouse allergen-containing particles in a laboratory animal facility

Airborne mouse allergen is a risk factor for respiratory diseases. Conventional assessment techniques provide mass-based exposure estimates that may not capture completely the inhalation risk of airborne allergen particles. In contrast to mass-based estimates, the halogen immunoassay (HIA) combines immunoblotting and microscopy to directly assess allergen-containing particles. We evaluated the HIA for the assessment of airborne mouse allergen and compared the results to the enzyme linked immunosorbent assay (ELISA). Particulate matter (PM)(10) and PM(2.5) samples (30 min, 4 l/m) were collected in a mouse facility before, during, and after disturbance of soiled bedding. Concentrations of Mus m 1-positive particles (haloed particles (HPs)) and intensities of the haloes were determined with the HIA. Although HPs/m(3) were positively correlated with mass concentration (statistically significant only with Mus m 1 concentration on PM(10)), replicates of mass concentration showed higher variability than HPs/m(3). After disturbance, most of the HPs were in the PM(2.5) fraction. Mean haloes intensities were similar before, during, and after disturbance. The HIA was able to measure allergen-containing particles with less variability than the ELISA, detected the shift of HPs to smaller particles after disturbance, and may suggests similar halo intensity by particles detected during and after disturbance. Our findings suggest that the HIA can be used to assess indoor concentrations of mouse allergen particles and their morphological characteristics.

Exposure to parvalbumin allergen and aerosols among herring processing workers

BACKGROUND

There are increasing reports of allergies and respiratory symptoms among workers in the fish processing industry, coinciding with an increasing use of high-pressure water in the processing plants. However, few studies have measured exposure in these work environments.

OBJECTIVES

The aim of this study was to characterize the occupational exposure of workers to herring antigen and to screen environmental factors at a herring (Clupea harengus) plant in which new and more encapsulated filleting machines had been installed. To assist in this, a method to assess airborne exposure to herring allergen was needed.

METHODS

Exposure to airborne herring antigen, mould spores, and endotoxin were measured during work. Antigen exposure was assessed using a newly developed sensitive (detection limit, 0.1 ng ml(-1)) rabbit polyclonal sandwich enzyme-linked immunosorbent assay against the major herring muscle protein allergen, parvalbumin. Aerosols were measured by mass concentration (DataRAM) and number of particles (Climet I-500).

RESULTS

Personal geometric mean herring allergen exposure was 986 ng m(-3) at the old filleting workstations and 725 ng m(-3) at the new workstations (difference not significant). Outside the production room, the level was ~130 ng m(-3). Number of particles and mass concentration were both significantly lower around the new machines than around the old machines (P < 0.001 and P < 0.0001, respectively). The highest particle count was seen for the 0.3-0.5 μm fraction, with more than 400,000 particles per cubic metre air. Endotoxin concentration in the air varied between 3 and 92 EU m(-3), with the highest levels when the catch mainly contained herring that had eaten krill or seaweed.

CONCLUSIONS

We developed a sensitive method to detect herring antigen. High exposure to herring antigen was measured during filleting work. The particles in the air around the fillet machines were mainly <0.5 μm and the newer encapsulated machines generated fewer particles. It is important to reduce occupational exposure of workers to aerosols by improving the ventilation system, machines, and organization of work.

Salmon allergen exposure, occupational asthma, and respiratory symptoms among salmon processing workers

BACKGROUND

This investigation was triggered by three cases of asthma-about 10% of the workforce-occurring in a salmon processing plant over a short period of time. The aim of the investigation was to characterize the work exposure of inhalable organic particles with personal measurements. Respiratory symptoms at work among workers were also assessed.

METHODS

Exposures to airborne salmon allergen, airborne mold spores, and endotoxin in water and air were measured during work. To assess the Atlantic salmon (Salmo salar) Sal s 1 allergen exposure a polyclonal sandwich enzyme-linked immunosorbent assay (ELISA) was developed. Current workers (n = 26) answered questionnaires and underwent allergy and lung function tests.

RESULTS

Using the sensitive ELISA method (0.05 ng/ml), we found that workers were exposed to high levels of salmon major allergen at the filleting machine and at the filleting table. Airborne endotoxin levels were low, and mold levels were elevated. Only the three initial asthma cases had IgE to salmon. Of the other workers, 65% reported respiratory symptoms at work. These had lower pulmonary function than workers without such symptoms.

CONCLUSIONS

We developed a sensitive method to measure salmon antigen in air and found that filleting workers were most exposed. It is important to reduce aerosols by improving the ventilation system, machines and organization of work since respiratory symptoms at work among workers were common.

Both the variability and level of mouse allergen exposure influence the phenotype of the immune response in workers at a mouse facility

BACKGROUND

The role of natural aeroallergen exposure in modulating allergen-specific immune responses is not well understood.

OBJECTIVE

We sought to examine relationships between mouse allergen exposure and mouse-specific immune responses.

METHODS

New employees (n = 179) at a mouse facility underwent repeated assessment of mouse allergen exposure, skin prick tests (SPTs), and measurement of mouse-specific IgG levels. Relationships between the mean level of exposure, variability of exposure (calculated as log deviation), and time to development of immunologic outcomes were examined by using Cox proportional hazards models.

RESULTS

By 24 months, 32 (23%) participants had experienced a positive SPT response, and 10 (8%) had mouse-specific IgG₄. The incidence of a positive SPT response increased as levels of exposure increased from low to moderate, peaking at 1.2 ng/m³, and decreased beyond this point (P = .04). The more variable the exposure was across visits, the lower the incidence of a positive SPT response (hazard ratio [HR], 0.17; 95% CI, 0.07-0.41). Variability of exposure was an independent predictor of a positive SPT response in a model that included both exposure metrics. In contrast, the incidence of mouse-specific IgG₄ increased with increasing levels of mouse allergen exposure (HR, 2.9; 95% CI, 1.4-6.0), and there was evidence of a higher risk of mouse-specific IgG₄ with greater variability of exposure (HR, 6.3; 95% CI, 0.4-95.2).

CONCLUSION

Both the level and variability of mouse allergen exposure influence the humoral immune response, with specific patterns of exposure associated with specific immunophenotypes. Exposure variability might be a more important predictor of a positive SPT response, whereas the average exposure level might be a more important predictor of mouse-specific IgG₄.

Occupational mouse allergen exposure among non-mouse handlers

This study assessed mouse allergen exposure across a range of jobs, including non-mouse handling jobs, at a mouse facility. Baseline data from 220 new employees enrolled in the Jackson Laboratory (JAXCohort) were analyzed. The baseline assessment included a questionnaire, allergy skin testing, and spirometry. Exposure assessments consisted of collection of two full-shift breathing zone air samples during a 1-week period. Air samples were analyzed for mouse allergen content, and the mean concentration of the two shifts represented mouse allergen exposure for that employee. The mean age of the 220 participants was 33 years. Ten percent reported current asthma and 56% were atopic. Thirty-eight percent were animal caretakers, 20% scientists, 20% administrative/support personnel, 10% materials/supplies handlers, and 9% laboratory technicians. Sixty percent of the population handled mice. Eighty-two percent of study participants had detectable breathing zone mouse allergen, and breathing zone mouse allergen concentrations were 1.02 ng/m³ (0.13-6.91) (median [interquartile range (IQR)]. Although mouse handlers had significantly higher concentrations of breathing zone mouse allergen than non-handlers (median [IQR]: 4.13 ng/m³ [0.69-12.12] and 0.21 ng/m³ [below detection (BD)-0.63], respectively; p < 0.001), 66% of non-handlers had detectable breathing zone mouse allergen. Mouse allergen concentrations among administrative/support personnel and materials/supplies handlers, jobs that generally do not entail handling mice, were median [IQR]: 0.23 ng/m³ [BD-0.59] and 0.63 ng/m³ [BD-18.91], respectively. Seventy-one percent of administrative/support personnel, and 68% of materials/supplies handlers had detectable breathing zone mouse allergen. As many as half of non-mouse handlers may have levels of exposure that are similar to levels observed among mouse handlers.

Airborne exposure to wheat allergens: measurement by human immunoglobulin G4 and rabbit immunoglobulin G immunoassays

BACKGROUND

Exposure to airborne wheat allergens in the bakery trade is associated with a high risk of occupational allergy and asthma. Control and reduction of allergen exposure require relatively simple but reliable monitoring techniques. We developed new rabbit IgG-based enzyme immunoassays (EIA) for wheat allergens, which might be a convenient alternative for the thus far used human IgG4 inhibition assay.

METHODS

The reactivity and specificity of rabbit antibodies were assessed by EIA and immunoblotting, and compared with those of IgE from wheat-sensitized bakers, and with the antibodies used in the IgG4 inhibition EIA. An IgG inhibition and a sandwich EIA were developed for analysis of airborne dust samples.

RESULTS

Human IgG4 and rabbit IgG inhibition EIAs had comparable sensitivities, with limits of detection (LOD) between 18 and 88 ng/mL, while the sandwich EIA was much more sensitive (LOD<0.2 ng/mL). Human IgG4 and rabbit IgG reacted in immunoblotting with most of the IgE-binding wheat proteins, although with quantitative differences. All three assays showed a strong reaction with wheat proteins, and some cross-reactivity with rye and barley, but were further highly specific for cereal flour proteins. Concentrations measured with the three EIAs in 432 airborne dust samples were highly correlated (r>0.95) and their absolute values showed less than 10-20% differences.

CONCLUSION

The rabbit IgG EIAs are valid substitutes for the human IgG4 inhibition EIA, with important practical advantages. The inhibition EIA is recommended for routine wheat allergen measurements. The sandwich EIA may be used to measure low allergen levels, as in short task-related exposure measurements or in subfractions of airborne dust samples.

Spreading of occupational allergens: laboratory animal allergens on hair-covering caps and in mattress dust of laboratory animal workers

BACKGROUND

Family members of laboratory animal workers are at risk of developing allergy to laboratory animals. Little is known about the spreading of laboratory animal allergens outside the animal facilities.

OBJECTIVE

To assess the presence of laboratory animal allergens in dust collected from mattresses of laboratory animal workers and unexposed controls.

METHODS

Mouse and rat urinary proteins were measured in samples of mattress dust collected by laboratory animal workers and unexposed controls. In addition, rat and mouse allergens were determined in extracts of hair-covering caps, used during laboratory animal work, to estimate spreading of allergen through dust captured on hair. Allergen concentrations on hair caps were compared with exposure measured by personal airborne dust sampling.

RESULTS

Levels of rat urinary allergens (RUA) and mouse urinary allergens (MUA) and mouse urinary protein (MUP) 8, a specific pheromone-binding mouse allergen, were significantly higher in mattress samples of laboratory animal workers than in those of controls. Hair-covering caps used in animal facilities harboured large amounts of RUA and MUA, which correlated significantly with exposure measured by the personal sampling technique in the animal facility.

CONCLUSIONS

Occupational laboratory animal allergens are detectable in mattress dust of laboratory animal workers. Transfer of allergens via uncovered hair of animal workers is likely contributing to this phenomenon. This study stresses the importance of using hair caps to prevent spreading of occupational allergens.

An amplified sandwich EIA for the measurement of soy aeroallergens

BACKGROUND

Soy hull low-molecular-weight (SHLMW) allergens were responsible for the soy asthma epidemics in Barcelona, with one 7.5 kDa protein (Gly m 1) being the main IgE-binding component. The aims of this study were to develop a sensitive sandwich enzyme immunoassay (EIA) using rabbit polyclonal antibodies to measure low levels of SHLMW allergens, and to compare this method with the previously described human IgE EIA-inhibition technique.

METHODS

IgG was isolated from serum of rabbits immunized with a chromatographically purified SHLMW extract (SHLMWE). Antibody-binding profiles were compared with those of human IgE anti-soy protein antibodies by Western blot analysis. An amplified sandwich EIA was developed using the purified SHLMWE as a calibration standard. Results were expressed in nanograms per millilitre. To compare the two assays, 54 air samples were analysed by both methods.

RESULTS

SDS-PAGE of the SHLMWE revealed four bands of 6, 8, 15 and 17 kDa. Gly m 1 in the SHLMWE was identified by fingerprinting. The detection limit of the assay was 40 pg/mL. The two methods correlated well (r=0.89; P<0.001). The allergen concentration was detected in all 54 (100%) samples by the sandwich EIA but in only 37 (68.5%) by the EIA inhibition.

CONCLUSIONS

The amplified sandwich EIA for SHLMW components has a high sensitivity and appeared to be a useful tool for the measurement of airborne SHLMW allergens, even at relatively low concentrations. Moreover, the method uses rabbit antibodies at high dilutions and does not require human sera, with limited availability and quantitative and qualitative pool-to-pool variability.

Airborne exposure to wheat allergens: optimised elution for airborne dust samples

Well-validated methods for measuring airborne occupational allergens are essential for effective control and reduction of allergen exposures. For wheat flour allergens, specific immunoassays are available, but there is a need for optimisation and standardization of sample processing procedures. Wheat flour allergen elution and storage were studied using airborne dust samples collected in bakeries with a new parallel sampler. Forty-eight series of 9 parallel filters were subjected to extraction procedures varying in elution medium, shaking method, extraction vial, and centrifugation speed. Wheat allergens were measured with enzyme immunoassays, and the effect of various procedures evaluated by mixed regression analyses. The stability of the eluted allergens was assessed after storage for 20 days and 4 months at -20 degrees C, in the presence or absence of casein in the medium. Only the type of elution medium had significant effects on allergen recovery: addition of Tween-20 resulted in 3- to 100-fold increased levels, an effect that was most pronounced at low concentrations. Allergen levels in extracts were stable for at least 4 months at -20 degrees C, irrespective of the presence of casein in the medium. Addition of Tween-20 to the elution medium is essential for optimal extraction of wheat allergen. The recommended procedure further includes the use of conventional polystyrene tubes, simple shaking methods, and centrifugation after extraction. Wheat dust extracts in PBS-Tween can be stored frozen for at least 4 months, and addition of a stabilising protein is not required.

Environmental detection of mouse allergen by means of immunoassay for recombinant Mus m 1

BACKGROUND

Mouse urinary allergens are an important cause of occupational asthma in animal facilities. Domestic exposure to mouse allergens is a risk factor for asthma among inner-city residents.

OBJECTIVE

We sought to develop a sensitive and specific assay for assessing environmental mouse allergen exposure.

METHODS

An ELISA for recombinant (r)Mus m 1 was developed by using rabbit polyclonal antibodies to rMus m 1 that were affinity purified against the natural allergen. Assay specificity was established by means of immunoblotting and ELISA. Mus m 1 levels in mouse, other mammalian allergenic products, and house dust samples from inner-city homes were compared.

RESULTS

Polyclonal antibodies to Mus m 1 showed a single 20-kd band on immunoblots against rMus m 1 and male mouse urine. Parallel dose-response curves were obtained by using mouse urine extract and natural Mus m 1 or rMus m 1. Mus m 1 was detected in mouse allergenic products (0.10-10.0 microg/mL) and in gerbil allergenic products (0.1 microg/mL) but was less than the limit of detection in epithelial extracts from 10 other animal species. Environmental measurements showed an excellent correlation between Mus m 1 levels in house dust extracts from inner-city asthma studies by using 2 different Mus m 1 standards (n=22; r=0.99; P <.001).

CONCLUSIONS

A highly sensitive ELISA has been developed with rMus m 1. This assay is suitable for monitoring domestic and environmental exposure to mouse urinary allergens.

Epidemic asthma in Barcelona: an evaluation of new strategies for the control of soybean dust emission

BACKGROUND

Asthma attacks and mortality due to inhalation of soybean antigens in Barcelona have been well documented. Strict protective measures in the unloading process were established in 1998 to avoid the release of soybean dust into the atmosphere. The present study was undertaken to assess the effectiveness of these latest environmental measures, and, if effective, to recommend their implementation in the many harbours where soybean is unloaded.

METHODS

Levels of soybean aeroallergen were analysed daily during a period of 5 years and 2 months in a total of 1,854 samples, 125 from the pre-intervention period and 1,729 from the postintervention period. Additionally, the number of asthma admissions to the emergency rooms of the city's three largest hospitals was recorded. Asthma patients attended at home by the public home emergency service and judicial autopsies registering asthma deaths were also investigated.

RESULTS

The mean concentration of soybean aeroallergen was 159 U/m(3) in the pre-intervention period and 39 U/m(3) in the postintervention period (p < 0.0001). Significant differences in postintervention aeroallergen concentrations were found between days of soybean unloading (42 U/m(3)) and days of no unloading (33 U/m(3)), with p < 0.0001. No significant relationship was found between concentrations of environmental soybean aeroallergens and the number of emergency room admissions for asthma.

CONCLUSIONS

Implementation of stricter protective measures in silos for the soybean unloading process has reduced the concentration of soybean dust in the atmosphere and evidences the effectiveness of the measures adopted.

Detection of mouse and rat urinary aeroallergens with an improved ELISA

BACKGROUND

Risk analysis of laboratory animal work presupposes allergen monitoring with sensitive methods. Commercial ELISA kits have recently become available for the detection of mouse (Mus m 1) and rat (Rat n 1) urinary allergen from settled dust samples and air samples with high allergen levels.

OBJECTIVE

Our aims were to enhance the sensitivities of the commercial ELISA kits for low aeroallergen levels (less than 1 ng/m(3)) and to test these methods with air samples collected from an animal facility.

METHODS

Personal and stationary air samples were collected from an animal facility during various tasks of laboratory animal work and from various premises of the animal facility.

RESULTS

The sensitivities of the ELISA assays were improved with a careful choice of analysis parameters and reagents. The detection limits of 0.1 ng/m(3) for Mus m 1 and 0.8 ng/m(3) for Rat n 1 were established. The sensitized assays enabled detection of mouse and rat aeroallergens also from premises in which animals or dirty cages were not present during sampling.

CONCLUSION

These sensitive assays will help to perform risk assessment in laboratory animal work. However, there remains a lack of standardized analytic procedures and occupational exposure limits for laboratory animal allergens.

Exposure to airborne allergens: a review of sampling methods

A number of methods are used to assess exposure to high-molecular weight allergens. In the occupational setting, airborne dust is often collected on filters using pumps, the filters are eluted and allergen content in the eluate analysed using immunoassays. Collecting inhalable dust using person-carried pumps may be considered the gold standard. Other allergen sampling methods are available. Recently, a method that collects nasally inhaled dust on adhesive surfaces within nasal samplers has been developed. Allergen content can be analysed in eluates using sensitive enzyme immunoassays, or allergen-bearing particles can be immunostained using antibodies, and studied under the microscope. Settling airborne dust can be collected in petri dishes, a cheap and simple method that has been utilised in large-scale exposure studies. Collection of reservoir dust from surfaces using vacuum cleaners with a dust collector is commonly used to measure pet or mite allergens in homes. The sampling methods differ in properties and relevance to personal allergen exposure. Since methods for all steps from sampling to analysis differ between laboratories, determining occupational exposure limits for protein allergens is today unfeasible. A general standardisation of methods is needed.

Controlling exposure to laboratory animal allergens

Laboratory animal allergy (LAA) is a significant occupational disease that may affect up to one third of personnel exposed to laboratory animals. Research has characterized the relative risks of exposure, in terms of intensity, frequency, and duration, associated with given tasks and work areas in the animal facility. Studies have shown that reduced exposure to animal allergens can reduce the incidence of LAA and relieve symptoms among affected workers. A combination of measures to eliminate or control allergen exposure, including engineering and administrative controls and personal protective equipment, have been integral components of effective LAA management programs. The author provides a comprehensive review of exposure control options, considerations, and " best practices" relative to laboratory animal allergen in the context of traditional industrial hygiene methods.

Laboratory animal allergy: a British perspective on a global problem

In the United Kingdom, laboratory animal allergy (LAA) has been recognized as an important occupational disease for nearly 25 years. However, introduction of health and safety legislation (e.g., the Control of Substances Hazardous to Health Regulations of 1988) and an increasing knowledge of the factors that contribute to the etiology of this disease have had surprisingly little impact on the prevalence and incidence of LAA over the last 10 to 20 yr. Studies of the relation between exposure to animal allergens and the development of LAA reveal that the risk of disease increases with increasing intensity of exposure. Current evidence suggests that animal allergens are very potent, and substantial decreases in allergen exposure are therefore necessary before a reduction in symptoms will be observed. In the United Kingdom, it is unlikely that an Occupational Exposure Limit will be set for animal allergens in the near future, partly because an adequately standardized assay for quantifying exposure is not yet available. Prevention of LAA in the future will probably be driven by the needs of the industry and will most likely rely on the adoption of guidelines describing " best practise" which incorporate sophisticated engineering methods of controlling exposure to animal allergens.

An amplified ELISA inhibition method for the measurement of airborne soybean allergens

BACKGROUND

Measurement of the soybean aeroallergen in Barcelona and other cities where soybean is unloaded is of increasing importance in controlling population exposure and evaluating the influence of such exposure on the persistence of asthma symptoms.

OBJECTIVE

The aims of the study were: (1) to standardize an amplified ELISA inhibition method for the quantification of soybean aeroallergen and (2) to compare this method to a previously described RAST inhibition method.

METHODS AND RESULTS

An amplified competitive ELISA inhibition method with a biotin-streptavidin system was carried out using a pool of sera from soybean-sensitized patients. The results were expressed as U/ml using a low-molecular-mass soybean allergen as reference standard. Reproducibility was calculated by statistically comparing the slope of the regression lines of the standard curve of 4 consecutive assays and by determining the coefficient of variation (CV) of the percent inhibition data for each point of several independent standard curves, each from the same assay (intra-assay) and also from a separate assay (inter-assay). No significant differences in the slopes were obtained by analysis of covariance (ANCOVA) F = 1.04. The CV between assays varied between 4 and 22% (for the assay range used in the reference standard) and was greater than the CV within assays (5-10%). Only values with a CV(%) smaller than 20% were considered acceptable. 78.5% of the samples satisfied this criterion. The RAST inhibition and ELISA inhibition methods were compared by difference plots from the values of 338 air filter eluates. The intraclass correlation coefficient was 0.456 (p < 0.001). After the results of both methods were classified as lower and higher than 165 U/m(3), the kappa index was 0.46 (p < 0.001).

CONCLUSIONS

The data obtained in the present study are comparable to those reported from other similar immunoassays. Moreover, despite the difficulty in comparing air-sampling values from different laboratories, the kappa index may be taken to represent fairly good agreement beyond chance between both methods. All these data demonstrate that the present immunoassay is useful for measuring airborne soybean aeroallergens and can also be applied to evaluate the relationship between exposure and the development of asthma symptoms.

Exposure assessment of high molecular weight sensitisers: contribution to occupational epidemiology and disease prevention

An important group of sensitising agents are so called high molecular weight sensitisers--proteins or glycoproteins with molecular weights in the 5-70 kDa range that can provoke a specific IgE response in workers exposed to these agents. Exposure to high molecular weight sensitisers could only be evaluated indirectly in the recent past. Few measurement techniques existed that made it possible to measure the allergens directly. As a result, few studies focused on establishing exposure-response relations, and exposure standards have not been established for high molecular weight sensitisers, or those that have are of doubtful scientific basis. Recent use of immunoassays changed this perspective dramatically. Antibodies used in the assays can originate from human serum (sensitized workers), serum from sensitised animals (rabbits producing polyclonal antibodies), or animal derived cell cultures producing monoclonal antibodies. Although few comparative studies exist, the available evidence suggests that although the correlation of allergen concentrations obtained with different assays is good, large systematic differences occur. The use of conversion factors to make data from previously performed allergen measurements comparable or exchangeable is limited and thorough standardization of assays is preferred. Validation and comparison of different assays by comparisons between laboratories seem important issues that have not received the attention needed. Epidemiological studies in several industries that used immunoassay for the exposure characterisation have shown that risk of sensitisation increases with increasing exposure to allergens. Several studies have also shown that clear differences in potency seem to exist. Sensitisation to rat urinary allergens and fungal alpha-amylase occurred in the pg/m3 and ng/m3 range. The main research questions of the near future have to focus on the prevention of occupational sensitisation. Standard setting seems possible for some allergenson the basis of the available scientific evidence for the existence of exposure response relations. However, assays for characterising exposure to allergens have to be rigorously standardised before they can be used under field conditions.

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.

Comparison of methods to assess airborne rat and mouse allergen levels. II. Factors influencing antigen detection

Potential factors influencing antigen detection in immunoassays for measuring rat or mouse aeroallergen (i.e., assay setup, antigen specificities, standard extracts used, and antigen decay) were investigated in a three-country study (the UK, The Netherlands, Sweden). An inhibition enzyme immunoassay (EIA) setup gave nominal rat urinary allergen (RUA) sample values seven times higher than a sandwich EIA setup utilizing identical antibodies and standards. In immunoblotting experiments, pooled patient serum and polyclonal rabbit antibodies partly detected different rat antigens; monoclonal antibody specificity could not be determined. Immunoblot detection of mouse urinary antigens (MUA) by the polyclonal rabbit antibodies from all laboratories was similar. In both the RUA and the MUA assays, urinary antigen standards were detected with similar potency, except purified Rat n 1, which was an inefficient inhibitor in the RUA RAST inhibition. In the sandwich EIA RUA assays, a rat room-dust extract was detected with 700800-fold less sensitivity than rat urine, whereas in the RAST RUA assay, dust inhibited equally with rat urine. Simulated decay did not decrease the potency of urinary antigen in any assay. Thus, assay setup and choice of detection antibodies strongly influence the nominal allergen levels. We recommend the use of standardized and characterized antibodies and standard extracts in sandwich EIAs to measure airborne rodent urinary allergens.