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Notes: Background Occupational exposure to rodent allergens may cause laboratory animal allergy. Personal exposure to occupational allergens is measured by collecting airborne dust on filters using person-carried pumps. This technique cannot be used to evaluate personal protective respiratory equipment. Recently developed intranasal air samplers collect inhaled particles by impaction on adhesive strips within the samplers.Objective The aims were to compare rodent aeroallergen exposure assessment using nasal air samplers with personal air sampling, and to evaluate the efficacy of using respiratory protection during rodent work using nasal air samplers.Methods Aeroallergen exposure was assessed during rodent work using both nasal air samplers and personal air samplers. The efficacy of respiratory protection (P2 facemasks and fresh-air helmets) was studied in subject pairs working side by side, one person with protection, the other without. Right nostril samples were laminated with protein-binding membrane and immunostained for rat urinary allergen-containing particles. Left nostril samples and air samples were eluted in buffer and analysed in amplified ELISAs for rat (RUA) and mouse (MUA) urinary allergen content (detection limit 10 pg/mL). Allergen collection efficacy of the nasal air samplers was tested at high and low exposure levels and at different flow rates using static sampling.Results P2 facemasks decreased the amount of inhaled allergen by about 90%, and very little allergen was inhaled using fresh-air helmets. Allergen levels in air and nasal samples correlated well (rs was about 0.8 for both RUA and MUA). The number of RUA-positive particles and nasal allergen levels measured in ELISA also correlated significantly (rs = 0.8). Collection efficacy of the nasal air sampler was better during high exposure (cleaning cages, median 73% of allergenic particles collected), than during low exposure (undisturbed room, 49% of particles).Conclusion Nasal air sampling is a relevant and sensitive complement to personal air sampling and enables evaluation of personal respiratory protection equipment. Use of P2 facemasks and fresh-air helmets may substantially reduce occupational exposure to inhaled allergens.

Notes: Background Several allergen-sampling methods are used to assess level of personal or indirect exposure to cat in homes, schools and other public buildings and working environments.Objective To compare four different allergen-sampling methods (dust collectors, Petri dishes, person-carried pumps and intranasal samplers) by simultaneous sampling in classrooms and to compare the cat allergen levels between conventional classrooms and allergy prevention classrooms. Another aim was to relate the results to self-reported frequency of allergy and asthma symptoms among the children, to their perception of the school environment.Methods Among all compulsory schools (n = 257) in the Stockholm suburban area, 35 classrooms (five with implemented allergy prevention measures, seven with additional cleaning and 23 with normal cleaning routines) were chosen for allergen-sampling. Dust collectors (two models), Petri dishes, person-carried pumps and intranasal samplers were used simultaneously. All children (n = 829) received a self-administered questionnaire which included questions about home and school environment, allergic disease, asthma symptoms and pet contact.Results The correlation between sampling methods was generally poor. Furthermore, there was no significant difference in allergen levels between allergy prevention and allergen avoidance classes compared to conventional classes. Median levels were generally, but not significantly, lower in classes with few cat owners, compared to classes with many cat owners. Children in allergy prevention classes were more satisfied with the indoor air quality and cleaning than children attending classes with fewer or no allergy prevention measures (P 〈 0.0001). Nine per cent of all children reported allergic symptoms while at school.Conclusion The lack of correlation between sampling methods used simultaneously demonstrates the difficulty in assessing allergen levels in schools and similar environments. The implemented intervention measures (allergy prevention/allergen avoidance) did not influence cat allergen levels at school.

Notes: Background Mouse and rat urinary proteins are potent occupational allergens for exposed personnel. Methods of measuring airborne allergens differ greatly, and reported levels of allergens vary considerably between laboratories.Objectives To compare the values obtained using two different methods of allergen detection.Methods Air samples were collected in rat rooms in Sweden and the United Kingdom at 2 L/min on to polytetrafluoroethylene (PTFE) filters and extracted in buffer containing 0.5% v/v Tween 20. Airborne rat urinary allergen (RUA) was measured in all samples by both RAST inhibition using a polyclonal human serum pool (UK) and a two monoclonal antibody sandwich ELISA employing antibodies specific for Rat n 1.02 (α2u-globulin) (Sweden).Results The two methods gave values which were correlated (r2 log values = 0.72, P 〈 0.0001), but differed by several orders of magnitude (median [range] ratio of RAST inhibition/ELISA = 316 [7-2680]. There was a systematic bias; as the absolute values increased, the difference in the measurements increased. The rat urine standards used were antigenically similar.Conclusions A large contrast in RUA values obtained from the two assays was observed in this study. This may be primarily due to methodological differences, but variations in antibody specificities or composition of allergenic epitopes in the air samples may contribute. The results demonstrate that standardization of methods and antibodies is necessary before interlaboratory comparisons can be made.

Notes: Background:  Some schools in Sweden offer allergen avoidance classrooms for allergic children with severe asthma. However, the measures commonly used to achieve a reduction in allergen levels have not been properly evaluated. The aim of the present prospective study was to study whether the levels of airborne cat allergen are altered after introducing feasible intervention measures in classrooms, without interfering with peoples’ freedom of choice regarding pet ownership.Methods:  Twenty-five classes, including five established allergy prevention classrooms participated in the study during a school year. After one term, six classes underwent a number of intervention measures recommended by the Swedish National Institute of Public Health. Curtains, upholstery and plants were removed, bookshelves were replaced with cupboards and regular cleaning was increased. Airborne dust was collected weekly (32 weeks) using duplicate Petri dishes (n = 1574) and on six occasions using two personal air samplers in each class (n = 264).Results:  Airborne cat allergen levels were showing a similar variability throughout the whole study in all classes. Despite extensive measures in order to reduce allergen exposure, cat allergen levels were unaltered in the six classes after intervention. Allergen levels were not significantly lower in the established allergy prevention classes, compared with the other classes. Cat allergen levels differed, however, significantly between classes with few and many cat owners (P 〈 0.05).Conclusions:  We conclude that the recommended allergen avoidance measures used in this study did not reduce airborne cat allergen. It seems plausible that measures that fail to reduce allergen levels also fail to influence health status in allergic children but this remains to be shown.

Notes: 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 700–800-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. Abbreviations: NHLI: National Heart and Lung Institute, London, UK; WAU: Wageningen Agricultural University, Wageningen, The Netherlands; NIWL: National Institute for Working Life, Solna, Sweden; Ab: antibody; mAb: monoclonal antibody; EIA: enzyme immunoassay; RAST: radioallergosorbent test; RIA: radioimmunoassay; MUA: mouse urinary allergen; RUA: rat urinary allergen; BSA: bovine serum albumin; HSA: human serum albumin; PBS: phosphate-buffered saline; PTFE: polytetrafluoroethylene (Teflon); TBS: Tris-buffered saline.

Notes: Background:  We have previously shown that airborne cat allergen levels are significantly lower in school classes using special school clothing or in classes with no pet owners. However, cat allergen is present and the levels are in fact two- to threefold higher on cat owners’ than noncat owners’ school clothing which is used, washed and stored at school only. This suggests that allergen is transferred to schools by routes other than clothing.Aim:  To analyse levels of cat allergen (Fel d 1) in hair from cat owners and noncat owners among children and adults.Methods:  Samples of unwashed hair (≥1 day prior to sampling) from adults and children with (n = 22) or without (n = 22) cats at home were collected at a hairdresser. In addition, samples of newly washed hair (adults only, n = 11) were collected. The hair sample was extracted and analysed for Fel d 1 content with ELISA.Results:  The geometric mean levels were more than two orders of magnitude higher in unwashed hair from cat owners, compared with noncat owners (P 〈 0.0001) and more than 10-fold higher in newly washed hair from adults. The allergen contamination of unwashed hair among noncat owners appeared higher in children than in adults (P = 0.045).Conclusions:  Hair may be an important source for transfer and deposition of cat allergen in schools and may explain why cat allergen is found in environments with strict allergen avoidance measures. Although it may be unrealistic to apply allergen avoidance strategies against this allergen source, it is important to be aware of it.

Notes: Background: Dust reservoir sampling is the most commonly used method for assessment of indirect allergen exposure. Because assessment of personal exposure using person-carried pumps is time-consuming and expensive we evaluated the Petri dish sampling method for measurement of airborne cat allergen in classrooms. Methods: Petri dish sampling was evaluated in three study parts. Part I: by comparison between Petri dish sampling and personal air sampling in 44 classrooms with many (≥ 20%) and few (≤ 10%) cat owners and by additional Petri dish sampling in 40 pet-free homes. Part II: by sampling with duplicate Petri dishes in 28 classrooms. Part III: by sampling in three classrooms at four sampling heights during different sampling times. All samples were analyzed for cat allergen (Fel d 1) content with a monoclonal antibody two-site ELISA (enzyme linked immunosorbent assay), using signal amplification when necessary. Results: There was a significant correlation between Petri dish sampling and personal air sampling (r = 0.66; P 〈 0.0001). Levels were five-fold higher in classes with many cat owners than in classes with few cat owners, regardless of method. A corresponding difference was found in the homes. Duplicate sample values were in fair agreement (Bland-Altman test) and were correlated (r = 0.77; P 〈 0.0001). Cumulative levels collected weekly in one Petri dish were lower than using five daily Petri dishes, regardless of sampling height. Conclusions: Petri dish sampling can be useful as an alternative method to personal air sampling of airborne allergens.

Notes: Airborne laboratory-animal allergens can be measured by several methods, but little is known about the effects of important differences in methodology. Therefore, methods used in research projects in The Netherlands, the UK, and Sweden were compared. Seventy-four sets of three parallel inhalable dust samples were taken by a single operator in animal facilities in the three countries, and analyzed in parallel by the three institutes for rat and mouse urinary allergen. Rat-allergen levels measured by RAST inhibition (UK) were 3000 and 1700 times higher than levels measured by enzyme immunoassay (EIA)-sandwich methods with polyclonal rabbit (The Netherlands) or monoclonal mouse (Sweden) antibodies, while the difference between the two EIA-sandwich methods was much smaller: a factor of 2.2. For mouse allergen, an inhibition radioimmunoassay (RIA) with rabbit antimouse antibodies (UK) gave 4.6 and 5.9 times higher concentrations than sandwich EIAs with rabbit polyclonal antibodies (Sweden and The Netherlands), while the difference between the two sandwich EIAs was, on average, 1.6-fold. Thus, although levels of rat and mouse aeroallergens are significantly correlated, the assay type gives large differences in absolute concentrations, and interlaboratory technical differences affect even the same assay type. Conversion factors can aid comparison between studies, and, in the long term, assay standardization is desirable. Abbreviations: NHLI: National Heart and Lung Institute (UK); WAU: Wageningen Agricultural University (The Netherlands); NIWL: National Institute for Working Life (Sweden); EIA: enzyme immunoassay; RAST: radioallergosorbent test; RIA: radioimmunoassay; MUA: mouse urinary allergen; RUA: rat urinary allergen; BSA: bovine serum albumin; HSA: human serum albumin; PBS: phosphate-buffered saline; PTFE: polytetrafluoroethylene (Teflon); CI: confidence interval.

Notes: Background: Our aim was to study the risk of laboratory animal all_ergy (LAA) among research staff working in laboratories separate from the animal confinement area. The roles of atopy and exposure intensity in LAA were studied with special regard to exposure to male rodents, who excrete higher levels of urinary all_ergens than female rodents. Methods: Eighty rodent-exposed subjects gave blood samples for the analysis of total IgE, Phadiatop, and specific IgE against rat (RUA) and mouse urinary all_ergens (MUA), and answered questionnaires. Air samples were collected for RUA and MUA aeroall_ergen measurement in both laboratories and animal confinement facilities. Results: Twenty percent of the subjects had IgE 〉0.35 kU/l to RUA and/or MUA, and 32% had experienced animal work-related symptoms, although 90% of aeroall_ergen samples from the research department laboratories were below the detection limit (〈0.26 ng RUA per m3 and 〈0.8 ng MUA per m3). Atopy (positive Phadiatop), total IgE 〉100 kU/l, other all_ergies (especiall_y to other animals), or more than 4 years of exposure significantly increased laboratory animal sensitization and symptoms. Working with mainly male rodents gave odds ratios (95% CI) of 3.8 (0.97–15) for sensitization and 4.4 (1.4–14) for symptoms. Subjects with both exposure to mainly male rodents and atopy or elevated total IgE had a 10-fold higher frequency of sensitization than exposed subjects with neither risk factor. Conclusions: A majority of subjects with a combination of exposure to mainly male rodents and atopy or elevated total IgE developed sensitization to and symptoms from laboratory animals. Current low exposure seems to maintain the presence of specific IgE. Further measures must be undertaken to provide a safe workplace for laboratory animal workers.

Notes: In a prospective study of laboratory technicians, selected indicators of allergy and atopy were studied in an attempt to determine predictors of laboratory-animal allergy (LAA). Laboratory technicians underwent spirometry, methacholine provocation tests, and blood sampling, and responded to a questionnaire during training and after 2 years' work. Among 38 laboratory-animal-exposed subjects, total IgE before exposure gave the best correlation (P 〈 0.01; Mann-Whitney U-test) to reported symptoms caused by laboratory animals (n= 8) at follow-up. The prevalence of atopy and allergic symptoms had increased in exposed technicians at follow-up, but this was also found among unexposed matched referents (n= 36 pairs). One subject in the exposed group reported asthma before exposure, compared with seven at follow-up (P 〈 0.05; Fisher's exact test). However, the prevalence of asthma had increased from two to six (not significant) also among unexposed technicians. There were no significant differences between the groups in any measured variable at follow-up. Among 43 subjects who later worked with laboratory animals, 21%, had a positive skin prick test for common allergens, as compared with 37% among 112 without animal exposure P= 0.06; x2 test), suggesting selection for laboratory animal work.