Increasing prevalence of asthma over 12 years among dairy farmers on Gotland, Sweden: storage mites remain dominant allergens

Regulatory roles of three miRNAs on allergen mRNA expression in Tyrophagus putrescentiae

BACKGROUND

Tyrophagus putresecentiae is an important mite species in rural and urban environments, causing sensitization and allergic disease. While evidence suggests that microRNAs (miRNAs) may regulate the expression of allergen-encoding genes, no study has directly investigated this possibility. Here, this gap was addressed by profiling miRNAs and elucidating their target allergen messenger RNAs (mRNAs) in this mite species.

METHODS

Small RNA and transcriptome libraries were constructed for eggs, larvae, nymphs, and adults. After deep miRNA and whole-transcriptome sequencing were performed, the miRNA and allergen-encoding mRNA regulatory networks were explored.

RESULTS

A total of 540 miRNAs were identified, including 155 with expression levels differing significantly across the four mite developmental stages (p < .01), 59 of which were novel. The mRNA expression for allergens was higher for Tyr p 1 in adults than in other developmental stages; Tyr p 2-5, 7, 10, 13, 33, and 34 in immature stages; and Tyr p 28, 35, and 36 in eggs and adults. A combined miRNA and transcriptome bioinformatics analysis showed that allergen Tyr p 3 was regulated by miRNA PC-5p-5698441_1, Tyr p 4 was regulated by PC-5p-7050653_1, and Tyr p 34 was regulated by PC-5p-5534223_1 and PC-5p-5698441_1. These three allergen mRNA and three miRNAs were identified using qRT-PCR, and their regulatory roles were confirmed by double-fluorescent reporter gene system and site-directed mutagenesis technology.

CONCLUSIONS

For the first time, allergen mRNA expression and miRNAs were profiled throughout the life cycle for an allergen-producing mite, and the results showed that miRNAs bind to target allergen mRNAs to regulate their expression.

Potential Metabolic Biomarkers in Adult Asthmatics

Asthma is the most common chronic airway inflammation, with multiple phenotypes caused by complicated interactions of genetic, epigenetic, and environmental factors. To date, various determinants have been suggested for asthma pathogenesis by a new technology termed omics, including genomics, transcriptomics, proteomics, and metabolomics. In particular, the systematic analysis of all metabolites in a biological system, such as carbohydrates, amino acids, and lipids, has helped identify a novel pathway related to complex diseases. These metabolites are involved in the regulation of hypermethylation, response to hypoxia, and immune reactions in the pathogenesis of asthma. Among them, lipid metabolism has been suggested to be related to lung dysfunction in mild-to-moderate asthma. Sphingolipid metabolites are an important mediator contributing to airway inflammation in obese asthma and aspirin-exacerbated respiratory disease. Although how these molecular variants impact the disease has not been completely determined, identification of new causative factors may possibly lead to more-personalized and precise pathway-specific approaches for better diagnosis and treatment of asthma. In this review, perspectives of metabolites related to asthma and clinical implications have been highlighted according to various phenotypes.

Prevalence of allergic sensitization to storage mites in Northern Europe

BACKGROUND

Allergic sensitization to storage mites has mostly been related to occupational exposures like farming, grain/cattle handling, whereas for non-occupational settings, storage mite sensitization has been attributed to cross-reactivity with house dust mite (HDM) allergens.

OBJECTIVE

We aimed to describe the prevalence of allergic sensitization to storage mites, co-sensitization to HDM allergens and respiratory symptoms in Denmark, Iceland, Norway and Sweden.

METHODS

The population comprised of 1180 participants born 1945-1972 of the third follow-up of the population-based cohort European Community Respiratory Health Survey (ECRHS) in Aarhus, Bergen, Reykjavik and Uppsala. A clinical examination included skin prick tests (SPT) to Lepidoglyphus destructor, Tyrophagus putrescentiae, Acarus siro and common inhalant allergens, as well as standardized interviews.

RESULTS

8% were sensitized to HDM and 10% to storage mite, with some variation by study centre: Reykjavik 13%, Bergen 8% and Aarhus 7%. In Uppsala, only L destructor (3%) was measured. Storage mite sensitization was higher among men (11%) than women (8%). Among storage mite sensitized, 44% were also sensitized to HDM. Storage mite sensitization was associated with asthma and nasal allergies, but not with age, education, pet keeping or place of upbringing.

CONCLUSIONS AND CLINICAL RELEVANCE

In this Northern European population-based study, allergic sensitization to storage mite was as common as HDM sensitization. Storage mite sensitization was, independently of HDM sensitization, associated with respiratory symptoms and asthma. Our findings suggest that storage mite sensitization should be evaluated with regard to inclusion into the common inhalant allergen panel in Northern Europe.

[Blomia tropicalis: A house dust mite in the tropics]

INTRODUCTION

Blomia tropicalis is a mite that belongs to the superfamily of Glycyphagidae. Initially described as a storage mite, it is now considered as a house dust mite of tropical and sub-tropical areas.

STATE OF THE ART

Sensitization to this mite is very common in South America and Southeast Asia. Epidemiological studies have also found sensitization to this mite in Africa and Central America. Blo t 5 is the major allergen of B. tropicalis. Co-sensitization to other house dust mites such as Dermatophagoides pteronyssinus (Der p) and Dermatophagoides farinae (Der f) is very common. Cross-reactivity has been described but recombinant allergens revealed by molecular biology techniques do not explain this cross-reactivity. Sensitization to B. tropicalis seems to begin at the age of 36 months, the incidence increases until adulthood, and decreases from the age of 50. The involvement of B. tropicalis in allergic rhinitis and asthma is well described. It is also implicated in other allergic diseases. Few studies have assessed the therapeutic strategies available against this mite but immunotherapy is widely used.

PERSPECTIVES

Studies are needed to better understand the role of B. tropicalis in human diseases and to develop specific treatments.

Animal allergens and their presence in the environment

Exposure to animal allergens is a major risk factor for sensitization and allergic diseases. Besides mites and cockroaches, the most important animal allergens are derived from mammals. Cat and dog allergies affect the general population; whereas, allergies to rodents or cattle is an occupational problem. Exposure to animal allergens is not limited to direct contact to animals. Based on their aerodynamic properties, mammalian allergens easily become airborne, attach to clothing and hair, and can be spread from one environment to another. For example, the major cat allergen Fel d 1 was frequently found in homes without pets and in public buildings, including schools, day-care centers, and hospitals. Allergen concentrations in a particular environment showed high variability depending on numerous factors. Assessment of allergen exposure levels is a stepwise process that involves dust collection, allergen quantification, and data analysis. Whereas a number of different dust sampling strategies are used, ELISA assays have prevailed in the last years as the standard technique for quantification of allergen concentrations. This review focuses on allergens arising from domestic, farm, and laboratory animals and describes the ubiquity of mammalian allergens in the human environment. It includes an overview of exposure assessment studies carried out in different indoor settings (homes, schools, workplaces) using numerous sampling and analytical methods and summarizes significant factors influencing exposure levels. However, methodological differences among studies have contributed to the variability of the findings and make comparisons between studies difficult. Therefore, a general standardization of methods is needed and recommended.

Animal allergens and their presence in the environment

Exposure to animal allergens is a major risk factor for sensitization and allergic diseases. Besides mites and cockroaches, the most important animal allergens are derived from mammals. Cat and dog allergies affect the general population; whereas, allergies to rodents or cattle is an occupational problem. Exposure to animal allergens is not limited to direct contact to animals. Based on their aerodynamic properties, mammalian allergens easily become airborne, attach to clothing and hair, and can be spread from one environment to another. For example, the major cat allergen Fel d 1 was frequently found in homes without pets and in public buildings, including schools, day-care centers, and hospitals. Allergen concentrations in a particular environment showed high variability depending on numerous factors. Assessment of allergen exposure levels is a stepwise process that involves dust collection, allergen quantification, and data analysis. Whereas a number of different dust sampling strategies are used, ELISA assays have prevailed in the last years as the standard technique for quantification of allergen concentrations. This review focuses on allergens arising from domestic, farm, and laboratory animals and describes the ubiquity of mammalian allergens in the human environment. It includes an overview of exposure assessment studies carried out in different indoor settings (homes, schools, workplaces) using numerous sampling and analytical methods and summarizes significant factors influencing exposure levels. However, methodological differences among studies have contributed to the variability of the findings and make comparisons between studies difficult. Therefore, a general standardization of methods is needed and recommended.

Sensitization to aeroallergens in Korean children: a population-based study in 2010

We performed this study to assess the prevalence of sensitization to aeroallergens and to analyze the difference between prevalence rates according to children's ages and residential areas. In this nationwide cross-sectional study, first grade students of 45 elementary schools and 40 middle schools were randomly selected, and skin prick tests were performed for 18 inhalant allergens between October and November 2010. Of 7,829 analyzed subjects, 3,753 (47.9%) were sensitized to at least one aeroallergen. Sensitization to Dermatophagoides farinae was found to be the most prevalent in elementary schoolchildren (32.4%), followed by Dermatophagoides pteronyssinus, Tyrophagus putrescentiae, Japanese hop, and oak. In middle schoolchildren, D. pteronyssinus yielded the highest prevalence (42.7%), followed by D. farinae, T. putrescentiae, Japanese hop, and cat. In middle schoolchildren, the sensitization rate to aeroallergens in metropolitan, urban, and rural areas was 57.2%, 54.3%, and 49.8%, respectively (P = 0.019). In this age group, the sensitization rate in low, middle, high, and very high income groups was 53.8%, 51.8%, 59.0%, and 59.6%, respectively (P = 0.002). In conclusion, the sensitization rate is 47.9% and house dust mite is the most prevalent allergen in the pediatric population in Korea. The rate is higher in metropolitan areas and the highest income group than in rural areas and low income groups.

New-onset asthma and the effect of environment and occupation among farming and nonfarming rural subjects

BACKGROUND

Many factors, including environmental exposures, have been related to the increase in the prevalence of asthma, but only few have been tested for in longitudinal studies.

OBJECTIVE

We studied farming students to determine whether their environment during childhood and as adults was a factor determining subsequent onset of asthma.

METHODS

From 1994 to 1998, new cases of asthma were identified by means of an annual posted questionnaire followed by a telephone interview in a prospective cohort consisting of 1964 farming-school students and 407 nonfarming subjects aged 16 to 26 years. For each case, we selected a control subject from the cohort with no asthma in a case-based design, and all underwent an interview and a clinical examination.

RESULTS

We found 122 new cases of asthma. In a multiple regression model the odds ratio for new asthma was 3.3 (95% CI, 1.7-6.3) for smoking; 3.4 (95% CI, 1.6-7.0), 2.5 (95% CI, 1.1-5.3), and 7.0 (95% CI, 1.2-41.6) for exposure to swine, dairy production, and welding, respectively; and 11.7 (95% CI, 2.4-56.4) for bronchial hyperresponsiveness at baseline. Being born and raised on a farm significantly reduced the risk odds ratio (0.5 [95% CI, 0.3-0.98]), whereas atopy had no influence.

CONCLUSION

Exposure to swine and dairy confinements, welding, smoking, and bronchial hyperresponsiveness are risk factors for nonallergic asthma, and being born and raised on a farm reduces the subsequent risk. These findings support the theory that immune and inflammatory responses can be influenced by environmental exposure to early childhood, reducing the risk of asthma later in life.

Asthma increase among farmers: a 12-year follow-up

Respiratory disease is a well known health hazard for farmers, but the long-term prognosis is less well known. This is a 12-year follow-up of an investigation of Swedish farmers, most of them dairy farmers. A questionnaire was mailed to all 418 farmers who were alive of the farmers originally participating in 1982. They were invited to an interview, spirometry, and blood sampling. Ninety-one per cent (380) of the farmers, 321 men and 59 women, responded to the questionnaire. The mean age was 56 years for the men and 55 years for the women. Of the group, 10% were smokers, 25% ex-smokers, and 65% had never smoked. The population estimate for asthma in the farmers was 8.9% in 1994 compared to 2% in 1982, and to 5.4%-6.6% in the general population in the region in 1982. Of the asthmatic subjects, one-third had positive RAST tests (radioallergosorbent tests). Almost 90% of the new onset asthma cases since 1982 had non-IgE-mediated asthma. Most of the IgE-mediated asthmatics had had symptoms for many years, while 70% of the non-IgE-mediated asthmatic farmers had no or only wheezing with colds 1982. Two new cases of hypersensitivity pneumonitis were identified, and 7.3% had experienced inhalation fever during the last 12 years. In general, individuals with asthma and chronic bronchitis who had left farming were in better health in 1994 as compared to 1982. In conclusion, farmers have an enhanced risk to develop asthma increasing with age. Asthma in farmers is often non-IgE-mediated.

Sensitization of children to storage mites in Kutahya, Turkey

Specific IgE against Acarus siro, Glycphagus domesticus, Tyrophagus putrescentiae, and Lepidoglyphus destructor have been investigated by ELISA in sera of 92 children. Of them, 41 were found to be specific IgE positive (> or = 0.35 IU/ml) against at least one of house dust mite species, Dermatophagoides pteronyssinus and Dermatophagoides farinae, by an immunoblot. In 65.9% of the dust mite-sensitized children, specific IgE against at least one of these mite species was found. Sensitization levels, including co-sensitization cases were found to be 35.7% against A. siro, 24.4% against T. putrescentiae, 31.7% against L. destructor, and 26.8% against G. domesticus. In non-sensitized children, dust mite sensitization level was found to be 25.5%. Breakdown of sensitization by individual species in this group was; against A. siro and T. putrescentiae at 7.8%, against L. destructor at 13.7%, and against G. domesticus at 9.8%. When all children were reckoned, 43.5% was found to be sensitized against at least one storage mite species, with sensitizations against A. siro at 18.5%, T. putrescentiae at 26.1%, L. destructor at 21.7%, and G. domesticus at 17.4%. In dust samples collected from the dwellings of children, distribution of species was found to be A. siro (17%), G. domesticus (23%), T. putrescentiae (29%), L. destructor (25%), and unidentified (6%). In Fisher's chi-square test on SPSS program, there was a relationship between dust mite sensitization and storage mite sensitization (P < 0.05), but no meaningful relationship was found on the basis of individual mite species.

Variability of IgE reactivity profiles among European mite allergic patients

BACKGROUND

House dust mites (HDM) Dermatophagoides pteronyssinus are a frequent indoor allergen source. Our aim was to determine the frequencies of IgE reactivity to purified HDM allergen molecules in mite allergic patients from different parts of Europe in order to establish an allergen panel for diagnosis of HDM allergy.

MATERIALS AND METHODS

Populations of D. pteronyssinus-allergic patients from Austria (n = 56), France (n = 55), Italy (n = 67) and Sweden (n = 65) and storage mite allergic patients from Sweden (n = 31) were analysed for IgE reactivity to eight purified natural (n) and recombinant (r) D. pteronyssinus allergens (nDer p 1, rDer p 2, nDer p 4, rDer p 5, rDer p 7, rDer p 8, rDer p 10 and rDer p 14) in RAST-based dot blot assays.

RESULTS

Using a combination of Der p 1 and Der p 2, at least 97% of the D. pteronyssinus-allergic patients could be diagnosed in each of the HDM allergic populations. However, more than 50% of the patients also reacted with other allergens and significant variabilities regarding the frequencies of IgE reactivity to individual allergen molecules were found. Patients with a predominant storage mite allergy showed none or only very weak IgE reactivity to purified D. pteronyssinus allergens.

CONCLUSIONS

Purified Der p 1 and Der p 2 are sufficient for the diagnosis of > or = 97% of D. pteronyssinus allergic patients in Europe, but other allergens may also play an important role for the diagnosis and treatment of HDM allergy.

Hypoallergens for allergen-specific immunotherapy by directed molecular evolution of mite group 2 allergens

Allergen-specific immunotherapy is the only treatment that provides long lasting relief of allergic symptoms. Currently, it is based on repeated administration of allergen extracts. To improve the safety and efficacy of allergen extract-based immunotherapy, application of hypoallergens, i.e. modified allergens with reduced IgE binding capacity but retained T-cell reactivity, has been proposed. It may, however, be difficult to predict how to modify an allergen to create a hypoallergen. Directed molecular evolution by DNA shuffling and screening provides a means by which to evolve proteins having novel or improved functional properties without knowledge of structure-function relationships of the target molecules. With the aim to generate hypoallergens we applied multigene DNA shuffling on three group 2 dust mite allergen genes, two isoforms of Lep d 2 and Gly d 2. DNA shuffling yielded a library of genes from which encoded shuffled allergens were expressed and screened. A positive selection was made for full-length, high-expressing clones, and screening for low binding to IgE from mite allergic patients was performed using an IgE bead-based binding assay. Nine selected shuffled allergens revealed 80-fold reduced to completely abolished IgE binding compared with the parental allergens in IgE binding competition experiments. Two hypoallergen candidates stimulated allergen-specific T-cell proliferation and cytokine production at comparable levels as the wild-type allergens in patient peripheral blood mononuclear cell cultures. The two candidates also induced blocking Lep d 2-specific IgG antibodies in immunized mice. We conclude that directed molecular evolution is a powerful approach to generate hypoallergens for potential use in allergen-specific immunotherapy.

Occupational respiratory health of New Zealand horse trainers

OBJECTIVES

To confirm that working with horses is an occupational respiratory hazard and observed associations are not attributable to confounding.

METHODS

A postal survey of the respiratory health of 659 horse trainers and a comparison group of 506 vegetable growers was conducted. Data were analysed using logistic regression.

RESULTS

Relative to vegetable growers, horse trainers reported higher rates of chronic bronchitis [odds ratio (OR) = 6.8, 95% confidence interval (CI): 2.2-21.4] and organic dust toxic syndrome/farmers' lung (ODTS/FL) (OR = 3.5, 95% CI: 1.8-6.8). Grinding oats, spreading hay, and using powdered feed supplements were associated with increased respiratory symptoms among trainers. Associations between symptoms and working with horses increased for full-time workers.

CONCLUSIONS

This study found evidence that working with horses is a risk factor for ODTS/FL and bronchitis. The associations did not appear to be explained by bias, including confounding. However, the possibility of confounding cannot be entirely ruled out, and confirmatory studies are needed. Future studies should consider inorganic dust exposures.

Mite allergens

There is an increasing awareness of the health implications of mite sensitivity, as it is closely related to asthma. Mite allergy constitutes a complex worldwide problem, with sanitary and economical implications. Not only are mite species present in house dust, producing potent allergens, but other, less studied species are also responsible for significant allergic reactions in occupational settings. In this review, we focus on the growing number of mite species that are implicated in allergic cutaneous and respiratory diseases in humans. Mite allergy is not restricted only to the human "indoor" environment, because numerous reports clearly demonstrate that many species that can induce sensitization and symptoms are encountered in occupational settings. An important component of allergy research is the evaluation of the allergenic cross-reactivity to verify to what extent different mite species have unique, species-specific, or cross-reactive allergens. The results of these investigations have important clinical consequences for the diagnosis and treatment of allergic diseases. Internationally standardized mite extracts are needed to compare sensitization rates around the world and clearly establish risk factors associated with sensitization and asthma. In spite of recent controversial results, a significant reduction in the exposure to mite allergens continues to be an important challenge and one of the main goals in the treatment of mite-induced respiratory symptoms. In many cases, this reduction must be achieved in the workplace as well as in the home environment.

Pesticides and respiratory symptoms among farmers

OBJECTIVE

Despite the intensive use of pesticides in agriculture there are few studies assessing the risk of respiratory conditions from this exposure. The study aimed at quantifying the prevalence of respiratory symptoms among farmers and evaluating its relationship with occupational use of pesticides and the prevalence of respiratory symptoms.

METHODS

A cross-sectional study was conducted among 1,379 farmers from two municipalities of Southern Brazil in 1996. Frequency and type of chemical exposure and pesticide poisoning were recorded for both sexes. All subjects aged 15 years or older with at least 15 weekly hours of agricultural activity were interviewed. An adapted questionnaire developed by the American Thoracic Society was used for the assessment of respiratory symptoms. Multivariate logistic regression analysis was carried out.

RESULTS

More than half (55%) of interviewees were male. The prevalence of asthma symptoms was 12% and chronic respiratory disease symptoms was 22%. Higher odds ratios for both asthma (OR=1.51; 95% CI: 1.07-2.14) and chronic respiratory disease (OR=1.34; 95% CI 1.00-1.81) symptoms were found in women. Logistic regression analysis identified associations between many forms of exposure to pesticides and increased respiratory symptoms. Occurrence of pesticide poisoning was associated with higher prevalence of asthma symptoms (OR=1.54; 95% CI: 1.04-2.58) and chronic respiratory disease symptoms (OR=1.57; 95% CI: 1.08-2.28).

CONCLUSIONS

In spite of causality limitations, the study results provide evidence that farming exposure to pesticides is associated with higher prevalence of respiratory symptoms, especially when the exposure is above two days per month.

IgE-sensitization to predatory mites and respiratory symptoms in Swedish greenhouse workers

BACKGROUND

Predatory mites are used as biological pesticides worldwide for control of spider mites and other pests in greenhouses. The aim of this study was to evaluate the impact of occupational exposure to Phytoseiulus persimilis and Hypoaspis miles on IgE sensitization among a large group of Swedish greenhouse workers and to examine the relationship between exposure and allergic asthma and rhinoconjunctivitis.

METHODS

A total of 96 greenhouse workers from the southern part of Sweden, who were using the predatory mites for control of pests, were investigated with a questionnaire and a medical examination including lung function test. Blood samples were taken to test for allergen-specific IgE antibodies to Phytoseiulus persimilis and Hypoaspis miles as well as to Tetranychus urticae, Dermatophagoides pteronyssinus/farinae and Tyrophagus putrescentiae.

RESULTS

Seventeen of the 96 workers were positive in ImmunoCAP to predatory mites: 17 to P. persimilis (17.7%) and 14 to H. miles (14.6%). Subjects sensitized to predatory mites were significantly more often atopic (13/17), defined as a positive Phadiatop, than those who lacked IgE against these mite species (17/79) (P <0.01). IgE antibodies to the red spider mite T. urticae were present among 23 subjects. Thirty-five of the investigated subjects displayed a positive ImmunoCAP to at least one of the investigated mite species. Furthermore, sensitization to any of the mites tested was significantly associated with asthma (OR=9.3) and rhinoconjunctivitis (OR=4.3).

CONCLUSIONS

IgE sensitization to predatory mites, P. persimilis and H. miles, is common among greenhouse workers. The findings stress the importance of improved allergen avoidance in greenhouse environments.

Occupational exposures as triggers of asthma

The prevalence of occupational asthma is rising, possibly due to the introduction of different chemicals and substances in the workplace. Etiologic agents include organic and inorganic compounds that are encountered in a variety of industries. Early diagnosis, adequate management of inflammation, and prevention of further exposure are essential to occupational asthma management. Reducing complications and disability while providing work rehabilitation should be the ultimate goal of the health care provider. This article discusses these issues and gives guidance to the clinician treating patients with possible occupational asthma.

[Dermatologic occupationally relevant type I allergies]

In Germany the most frequent initial report of occupational disease is due to occupational skin diseases ("Berufskrankheitenanzeige nach Nr. 5101 der Berufskrankheitenverordnung") defined as "severe or recurrent skin diseases that force the discontinuation of any activity that causes or that could be causing the development, the worsening, or the recurrence of the skin disease". The majority of these occupational skin diseases consists of irritant and allergic contact dermatitis. In contrast, work place- related Type I allergy (contact urticaria syndrome) is less frequent, but carries the risk of systemic reactions. The clinical manifestations and pattern of exposure to Type I allergens in the work place are described.

Respiratory status in dairy farmers in France; cross sectional and longitudinal analyses

AIMS

To compare respiratory status in dairy farmers with that of non-farming controls.

METHODS

Longitudinal study in the Doubs (France). From a cohort constituted in 1994 (T1), 215 (81.1%) dairy farmers and 110 (73.8%) controls were reevaluated in 1999 (T2). The protocol comprised a medical and occupational questionnaire, spirometric tests at both evaluations, allergological tests at T1, and a non-invasive measure of blood oxygen saturation (SpO2) at T2.

RESULTS

In 1999 analyses, the prevalence of chronic bronchitis was higher (p = 0.013), and FEV1/VC (p < 0.025) and SpO2 (-0.7%, p < 0.01) lower in dairy farmers than in controls. In a multiple linear regression model, farming, age, and smoking were significantly and inversely correlated with SpO2. In the whole population, the mean annual decline in FEV1 and FEV1/VC was -13.4 ml and -0.30%, respectively. Farming was associated with an accelerated decline in FEV1/VC (p < 0.025) after adjustment for covariates. No relation between allergy and respiratory function changes was observed, except for FEF25-75.

CONCLUSIONS

This prospective study shows that dairy farming is associated with an excess of chronic bronchitis, with a moderate degree of bronchial obstruction and a mild decrease in SpO2.

Occupational asthma caused by high-molecular-weight substances

More than 250 agents that are encountered in the workplace have been shown to induce asthma in susceptible individuals. It is estimated that 2% to 15% of cases of asthma may be occupational. High-molecular-weight substances, such as plant and animal proteins, enzymes, and large carbohydrate molecules, can induce IgE-mediated occupational asthma. The incidence of disease varies among industries and is dependent on the physiochemical properties of the agent, the level and duration of exposure, industrial hygiene, engineering practices, and host factors. Risk factors, common high-molecular-weight workplace antigens, diagnosis, treatment, and prognosis are discussed.

Lep d 2 polymorphisms in wild and cultured Lepidoglyphus destructor mites

We have previously cloned, expressed and characterized two variants of the major allergen Lep d 2 from cultured Lepidoglyphus destructor mites. These variants, Lep d 2.0101 and Lep d 2.0201, differ at 13 amino acid positions. In this study we investigated Lep d 2 sequence diversity between wild and cultured mites. PCR, Southern blot and DNA sequence analysis revealed the presence of two different Lep d 2 genes, one with and one without an intron. In addition, two new variants of Lep d 2, Lep d 2.0102 and Lep d 2.0202, were found at different frequencies in wild and cultured mites. When we expressed the Lep d 2 variants and compared their IgE binding properties by ELISA inhibition, we found that Lep d 2.0102 was a more potent inhibitor than Lep d 2.0101, and to a lesser extent Lep d 2.0202 was more potent than Lep d 2.0201. Long-term cultures of peripheral blood mononuclear cells were used to assess the ability of the expressed Lep d 2 variants to induce cytokine release. Although cells from different individuals released different amounts of interferon-gamma and interleukin-5, no consistent cytokine release pattern could be linked to any specific Lep d 2 variant. In conclusion, we show that both cultured and wild Lepidoglyphus destructor mites contain the same pattern of polymorphism. Furthermore, this Lep d 2 sequence diversity seems not to have any significant impact on the allergens IgE binding or its ability to induce T cell cytokine release.

Associations of Fc epsilon R1-beta polymorphisms with immunoglobin E antibody responses to common inhalant allergens in a rural population

BACKGROUND

Polymorphisms within the beta subunit of the high-affinity receptor for IgE (Fc epsilon R1-beta ) on chromosome 11q13 have been related to atopy and asthma and the lymphotoxin alpha (LT alpha) gene on chromosome 6 is implicated in asthma.

OBJECTIVE

To elucidate the association of polymorphisms in the Fc epsilon R1-beta and LT alpha genes to IgE responses and asthma in a family-orientated rural population.

METHODS

A total of 461 adult farmers, who participated in an epidemiological follow-up study on respiratory symptoms among farmers on the Swedish island of Gotland, were examined. The traits assessed included serum total IgE, IgE antibody responses to 21 common inhalant allergens and asthma.

RESULTS

The 237G mutation was only detected in seven persons. Atopy was found to be associated with the RsaI-ex7 AB-genotype (OR = 1.9; P = 0.04). The RsaI-ex7 B allele had a significant influence on IgE responses to pollens and dust mites (OR = 5.5; P = 0.03 and OR = 5.2; P = 0.049, respectively). The influence of this allele was stronger when the association towards single dust mite species (Lepidoglyphus destructor) was estimated (OR = 7.1, P = 0.03) and the association increased even more when the major allergen of L. destructor (rLep d 2) was analysed (OR = 11.2, P = 0.02). These associations were independent of sex, age and smoking, and the estimates of RsaI-in2 independent of RsaI-ex7. RsaI-in2, RsaI-ex7 and LT alpha genotypes were unassociated with total serum IgE. No significant difference in the distribution of RsaI-in2, RsaI-ex7 and LT alpha genotypes was found among subjects with atopy or asthma compared to healthy controls.

CONCLUSION

This study supports the notion that polymorphisms in the Fc epsilon R1-beta gene have significant effects on IgE responsiveness. Secondly, dust mites in rural populations influence the expression of genes on chromosome 11q13.

The impact of asthma risk factors on home management of childhood asthma

There have been few studies of childhood asthma among families who live in nonmetropolitan settings. This work is part of the baseline assessment conducted before implementing a health education program to study the impact of asthma risk factors (gender, ethnicity, socioeconomic status, asthma severity) on home asthma management. Data analysis yielded no significant differences in home asthma management performed by parents or children with asthma based on the child's gender, ethnicity, asthma severity, or family socioeconomic status. Factors that define the child's experienced asthma pattern, such as activity limitations, number of allergens, and school absenteeism, were associated with the parent's work of asthma management. Trends in the data for the different ethnic and gender subgroups that have implications for clinical practice were identified. Future directions for research to address questions that emerged in this analysis are discussed.

Effect of ingestion of honey on symptoms of rhinoconjunctivitis

BACKGROUND

Allergic rhinoconjunctivitis is a common disorder, affecting >20% of people of all socioeconomic strata. Despite this high prevalence, relatively few sufferers seek professional medical help, presumably because of a widespread reliance on complementary remedies.

OBJECTIVE

We investigated the widely held belief among allergy-sufferers that regular ingestion of honey ameliorates the symptoms of allergic rhinoconjunctivitis.

METHODS

The study was conducted at the University of Connecticut Health Center's Lowell P. Weicker General Clinical Research Center. Thirty-six participants who complained of allergic rhinoconjunctivitis were recruited. All recruits were scratch-tested at entry for common aeroallergens. The cohort was randomly assigned to one of three groups, with one receiving locally collected, unpasteurized, unfiltered honey, the second nationally collected, filtered, and pasteurized honey, and the third, corn syrup with synthetic honey flavoring. They were asked to consume one tablespoonful a day of the honey or substitute and to follow their usual standard care for the management of their symptoms. All participants were instructed to maintain a diary tracking 10 subjective allergy symptoms, and noting the days on which their symptoms were severe enough to require their usual antiallergy medication.

RESULTS

Neither honey group experienced relief from their symptoms in excess of that seen in the placebo group.

CONCLUSIONS

This study does not confirm the widely held belief that honey relieves the symptoms of allergic rhinoconjunctivitis.

An ELISA for recombinant Lepidoglyphus destructor, Lep d 2, and the monitoring of exposure to dust mite allergens in farming households

BACKGROUND

Exposure to indoor allergens, such as dust mites, has been recognized as a risk factor for sensitization and symptoms.

OBJECTIVE

To develop a two-site ELISA for the determination of Lep d 2 in the reservoir, to measure dust mite allergen exposure (Lep d 2, Der p 1, Der f 1 and Der 2) in farm households, and to investigate whether exposure to these allergens is associated with sensitization, asthma and rhinoconjunctivitis.

METHODS

Monoclonal antibodies to recombinant (r)Lep d 2 were produced with standard hybridoma technique. Dust samples from 393 households were analysed for allergen content by two-site ELISA methods.

RESULTS

A two-site Lep d 2 ELISA was developed with a detection limit of 0.09 microg/g. The assay was highly reproducible and levels of Lep d 2 showed a strong correlation with the number of Lepidoglyphus mites (r(s): 0.7; P = 0.0002). Lep d 2 was detected in 20% of the homes; levels ranged from 0.09 to 1.7 microg/g of dust. Der p 1 was recorded in 59% of the samples, ranging from 0.055 to 139 microg/g, and Der f 1 and Der 2 in 40% and 50% of the samples, ranging from 0.055 to 24.5 microg/g and 24.3 microg/g, respectively. Dermatophagoides allergens were significantly higher in mattresses than in carpets (P < 0.0001), but this difference was not observed with Lep d 2. A strong relationship between immunoglobulin (Ig)E to rLep d 2 and asthma (OR = 10.4) and rhinoconjunctivitis (OR = 7.5) was seen. Furthermore, sensitization to D. pteronyssinus was significantly associated with asthma (OR: 13.7) and rhinoconjunctivitis (OR: 5.7).

CONCLUSION

When assessing mite allergen exposure in rural homes, not only the Der p 1, Der f 1 and Der 2 allergens, but also the Lep d 2 allergen should be taken into consideration.

Dust mites: update on their allergens and control

Mites are ubiquitous organisms, and as a result, humans come into contact with mites and mite products in a variety of situations. Molecules from many mite species can induce IgE-mediated reactions. Best known among the allergy-causing mites are the house dust and storage mites. However, allergists should be aware that, in specific situations, contact with products of many other less-known species of mites also may cause IgE-mediated reactions.

Occupational allergens

Occupational agents are important in a significant number of respiratory diseases. More than 250 occupational substances have been reported to cause occupational asthma. Occupational allergens are the subset of agents causing occupational diseases through an IgE-mediated mechanism. These allergens may be classified as being of either high or low molecular weight. The more common occupational allergens and the industries at increased risk of exposing workers to these agents are discussed.

A hypoallergenic derivative of the major allergen of the dust mite Lepidoglyphus destructor, Lep d 2.6Cys, induces less IgE reactivity and cellular response in the skin than recombinant Lep d 2

BACKGROUND

The major allergen of the dust mite Lepidoglyphus destructor, Lep d 2, has been produced as a recombinant allergen (rLep d 2) with IgE reactivity both in vivo and in vitro. A modified form of rLep d 2 (rLep d 2.6Cys) obtained by site-directed mutagenesis has been shown to have a reduced IgE reactivity in vitro. In this study we have compared the ability of rLep d 2 and rLep d 2.6Cys to elicit positive skin prick tests and cellular responses among L. destructor-sensitized subjects.

METHODS

Seventeen subjects were skin prick-tested with rLep d 2, rLep d 2.6Cys, histamine and negative controls and 17-20 h later skin biopsy specimens were taken from the skin prick-tested sites. The biopsy specimens were stained immunohistochemically for EG2+, CD3+, CD1a+, mast cell tryptase+, and IgE+ cells. Dermal cell infiltrates were judged in hematoxylin and eosin staining. Total IgE and allergen-specific IgE were determined by CAP-RAST.

RESULTS

Compared to rLep d 2, rLep d 2.6Cys induced significantly smaller and fewer skin prick test reactions (p < 0.001) and dermal cell infiltrates (p < 0.05). Further, rLep d 2.6Cys induced fewer EG2+ cells (p < 0.001) but more tryptase+ cells (p < 0.05) than rLep d 2. A positive RAST to rLep d 2 was obtained for 88.2% of the subjects, while only 35.2% displayed a positive RAST to rLep d 2.6Cys.

CONCLUSION

This study demonstrates that rLep d 2.6Cys is less able to evoke IgE-mediated reactions and cellular responses, as measured both in skin and in serum, than rLep d 2. In the future this hypoallergenic derivative may be a promising candidate molecule for immunotherapy of L. destructor-allergic patients.

Allergenic cross-reactivity between the nematode Anisakis simplex and the dust mites Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, and Dermatophagoides pteronyssinus

BACKGROUND

The nematode Anisakis simplex is a common parasite on fish and other seafood. It is considered to be a food allergen and to induce IgE-mediated reactions. Allergenic cross-reactivity between A. simplex and other nematodes has been reported, as has cross-reactivity with arthropods: red mosquito larvae and German cockroach. We have here studied the allergenic relationship between A. simplex and four different dust-mite species.

METHODS

Serum samples collected from 69 farmers allergic to dust mites were analyzed for IgE to A. simplex by CAP FEIA. Allergenic cross-reactivity between A. simplex and dust mites was studied in two of the sera by CAP FEIA and immunoblotting inhibition.

RESULTS

We found that 14/69 farmers had detectable levels of IgE antibodies to A. simplex. The IgE response in CAP FEIA to A. simplex was inhibited to various degrees in the two studied sera by extracts of the dust mites Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, and Dermatophagoides pteronyssinus. In the reverse inhibition experiment, extract of A. simplex inhibited the response in both sera to A. siro and T. putrescentiae, but not to L. destructor. The IgE binding to D. pteronyssinus was inhibited in one of the two sera. In blotting inhibition experiments, the IgE binding to several allergens in A. simplex was inhibited by each of the four mite extracts, especially by A. siro and T. putrescentiae, which completely inhibited the IgE binding to several allergens.

CONCLUSION

The results show allergenic cross-reactivity between several allergens in A. simplex and four dust-mite species. The clinical significance of this cross-reactivity remains to be evaluated.

Current concepts on the genetics of asthma

Asthma is a complex genetic disorder with variable phenotype, largely attributed to the interactions of the environment and multiple genes, each potentially having small effects. Numerous asthma and atopy loci have been reported in studies demonstrating associations and/or linkage of the asthma-associated phenotypes, atopy, elevated IgE levels, and bronchial hyperresponsiveness to alleles of microsatellite markers and single nucleotide polymorphisms within specific cytokine/chemokine and IgE regulating genes. Although the studies reporting these observations are compelling, most of them lack statistical power. This review compiles the evidence that supports linkage and associations to the various genetic loci and candidate genes. Whereas significant progress has been made in the field of asthma genetics in the past decade, the roles of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype remain to be determined.

Is the increase in childhood asthma coming to an end? Findings from three surveys of schoolchildren in Rome, Italy

Time trends in the prevalence of asthma, family history of asthma and atopy in Roman schoolchildren were assessed. The study population consisted of all children (aged 6-14 yrs) attending two primary schools in Rome, situated in urban areas that differed markedly in socioeconomic conditions and environmental pollution. Three questionnaire-based surveys were conducted in 1974, 1992 and 1998 in 2,259, 1,229 and 1,139 children. The prevalence of asthma in males and females increased significantly during 1974-1992 and remained stable from 1992-1998. In age groups born in the subsequent 4-yr periods it increased almost linearly, for children born from 1962-1965 to 1982-1985 (4.4%-12.5%), and remained remarkably stable in children born after 1985. Because the prevalence of asthma had a steeper trend in males than in females (approximately 0.55% x yr(-1) versus 0.25% x yr(-1)), the male:female asthma ratio increased (1:38 in 1974; 1:84 in 1992 and 1:62 in 1998). No single environmental factor, including area of residence, seemed to influence the prevalence of asthma. Family history of asthma and atopy also increased steadily (0.72% x yr(-1) and 0.30% x yr(-1) respectively) more than doubling during the 24-yr study period. The strong relationship between asthma and a family history of atopy not only persisted but also strengthened over time (23.3% of asthmatic children belonged to families with atopic illnesses in 1974 but 44.2% in 1998). The environmental factors that might explain the almost three-fold rise in childhood asthma between 1974 and 1992 remain unknown but the genetic background of the disease has presumably remained unchanged since the early 1970s. The fact that the prevalence of asthma increased no further during the past 6 yrs suggests that the progressive induction of asthma symptoms in genetically predisposed subjects is a self-limiting process that has probably come to an end in the authors' study area.

Oilseed rape flour: another allergen causing occupational asthma among farmers

BACKGROUND

Farmers are exposed to a wide variety of sensitizers. Since occupational asthma (OA) can lead to permanent disability, exposure discontinuation is the preferred treatment. When this is not possible, the identification of the causative allergen may allow an alternative therapy.

METHODS

We present three farmers diagnosed with OA as a consequence of handling fodder. We carried out skin tests with common and occupational allergens and with oilseed rape (OSR) extract. Total and specific serum IgE levels were measured. The patients underwent the OSR-bronchial provocation test (OSR-BPT). The day before and 24 h after the OSR-BPT, the methacholine (M)-BPT and induced sputum were performed. Eosinophil percentages and ECP levels were measured in the sputum samples.

RESULTS

OSR sensitization (skin tests and specific serum IgE) was detected in all the patients. The OSR-BPT elicited early responses in two subjects. Methacholine sensitivity, sputum eosinophils, and sputum ECP levels increased 24 h after the OSR-BPT in all the patients.

CONCLUSIONS

We have demonstrated that inhalation of OSR flour causes bronchoconstriction, induces an eosinophilic inflammatory bronchial response, and increases bronchial hyperresponsiveness in sensitized asthmatics. OSR flour contained in animal fodder should be considered another potential cause of OA among farmers.

Cloning of three new allergens from the dust mite Lepidoglyphus destructor using phage surface display technology

The dust mite Lepidoglyphus destructor is a common species in Europe and a major cause of dust mite allergy in rural surroundings, but it also contributes to dust mite allergy in urban areas. One major allergen, Lep d 2, has been expressed as a recombinant protein and evaluated both in vivo and in vitro and shown to detect 60% or more of L. destructor-sensitized subjects. Additional recombinant allergens are needed to obtain a reliable diagnostic tool for L. destructor allergy. The aim of this study was to clone and express new allergens from L. destructor and determine their recognition frequency among sensitized individuals. A phage display cDNA expression library was constructed and screened with sera from L. destructor-sensitized individuals. The cDNAs encoding the allergens were cloned into the pET17b vector and subsequently expressed in Escherichia coli as C-terminal His6-tagged proteins. Immunoblotting of the recombinant proteins was performed using sera from 45 subjects allergic to L. destructor. Three new allergens from L. destructor, Ld 5 (originating from a partial Lep d 5 clone), Lep d 7 and Lep d 13, were identified and recognized by 4/45 (9%), 28/45 (62%) and 6/45 (13%) sera from L. destructor-sensitized subjects, respectively.

Skin prick test and serological analysis with recombinant group 2 allergens of the dust mites L. destructor and T. putrescentiae

BACKGROUND

The dust mites Lepidoglyphus destructor and Tyrophagus putrescentiae are important sources of allergen in farming environments. The major allergens of the dust mites L. destructor and T. putrescentiae have been cloned and expressed as recombinant proteins.

OBJECTIVE

To evaluate the use of recombinant group 2 allergens of L. destructor (rLep d 2) and T. putrescentiae (rTyr p 2) in skin prick test (SPT), and serological analysis in sensitized and non-sensitized farmers chronically exposed to dust mites.

METHODS

Skin prick test with rLep d 2, rTyr p 2 and the corresponding commercial extracts was performed in 44 farmers sensitized to L. destructor and/or T. putrescentiae, and 38 control farmers. IgE and IgG subclass antibodies to the recombinant allergens were analysed by RAST and ELISA, respectively.

RESULTS

Out of the 44 subjects positive in SPT to L. destructor and/or T. putrescentiae extract, 26 (59%) displayed a positive SPT to one or the other of the recombinant allergens, whereas 21 (48%) were positive to both. Significant correlations were registered between the sizes of the weals induced by rLep d 2 and rTyr p 2 and the corresponding RAST values (P < 0.001). A majority of subjects positive in SPT to the recombinant allergens had detectable IgG4 antibodies, and the levels were significantly higher in the dust mite sensitized group than in the controls (P < 0.05). No such differences were found in the IgG1 values (P > 0.05). The results obtained with rLep d 2 and rTyr p 2 correlated relatively well with each other with respect to SPT, RAST and IgG4, suggesting that the allergens have similar or shared IgE epitopes. All the control subjects had a negative SPT and RAST to rLep d 2 and rTyr p 2.

CONCLUSION

Recombinant group 2 allergens from the dust mite L. destructor and T. putrescentiae represent useful tools for diagnosis of dust mite allergy.

Risk factors associated with asthma and rhinoconjunctivitis among Swedish farmers

BACKGROUND

Earlier studies have shown a high prevalence of respiratory symptoms in farming communities and that storage mites constitute important allergens. We examined risk factors associated with asthma and rhinoconjunctivitis among Swedish farmers.

METHODS

A population of 1015 small-scale dairy farmers was part of an epidemiologic survey. After selection based on symptom reports in a questionnaire, 461 of the farmers attended a medical examination, which comprised SPT, RAST analyses, and lung-function measurements. Risk factors for sensitization to different allergens, and development of asthma and rhinoconjunctivitis were assessed by multiple logistic regression.

RESULTS

The prevalence of atopy was 26.7% among the farmers. For both asthma and rhinoconjunctivitis, sensitization to mites (OR = 5.8 vs. OR = 3.8) and pollens (OR = 10.3 vs. OR=5.8) was a significant risk factor. There was a significant relationship between sensitization to mites and working time (OR = 5.2). Environmental tobacco smoke and exposure to different animal species at the farm did not appear to affect the risk of allergen sensitization or respiratory symptoms. Farmers smoked less than the general population, but they more frequently had reduced FEV1.

CONCLUSIONS

Allergen sensitization, especially to mites and pollens, was significantly associated with asthma and rhinoconjunctivitis in a farming community. The results point to allergen avoidance as a major goal for the prevention of occupational respiratory diseases among the farming population.

Evaluation of specific IgE to the recombinant group 2 mite allergens Lep d 2 and Tyr p 2 in the Pharmacia CAP system

BACKGROUND

Several recombinant allergens have been shown to be potentially useful for diagnosis of IgE-mediated allergy, but only a few recombinant allergens are at present commercially available in serological assays for detection of specific IgE. The aim of this study was to evaluate the IgE binding to the recombinant major dust mite allergens rLep d 2 and rTyr p 2 and compare it with the IgE binding to the commercial mite extracts Lepidoglyphus destructor and Tyrophagus putrescentiae in the Pharmacia RAST CAP System.

METHODS

The recombinant allergens rLep d 2 and rTyr p 2 were immobilised on ImmunoCAPs, and sera from 461 Swedish farmers who are frequently exposed to mites were analysed for specific IgE antibodies. Immunoblotting was performed to evaluate discrepancies between the results obtained with the recombinant and the commercial CAP assays.

RESULTS

The IgE values of each recombinant assay significantly correlated with the IgE values of the corresponding commercial CAP assay. The sensitivity of the rLep d 2 assay was 73.3% and that of the rTyr p 2 assay, 60.5% of that provided by the commercial L. destructor and T. putrescentiae assays. Two subjects out of 416, who tested negative in the commercial L. destructor assay, were positive to rLep d 2. The corresponding figures for rTyr p 2 and the T. putrescentiae extract were 5/418. The possibility that these subjects were sensitised to L. destructor and T. putrescentiae could not be excluded.

CONCLUSIONS

The data suggest that it may be possible to use rLep d 2 and rTyr p 2 on ImmunoCAPs to detect and quantify IgE antibodies to these, the major allergens of L. destructor and T. putrescentiae. It appears likely that the addition of just a few more recombinant L. destructor and T. putrescentiae allergens in the CAP assay will be sufficient for in vitro diagnosis of IgE mediated allergy to L. destructor and T. putrescentiae.

Identification and characterisation of two allergens from the dust mite Acarus siro, homologous with fatty acid-binding proteins

BACKGROUND

Dust mites are a major cause of allergic disease worldwide. The dust mite Acarus siro is an inducer of occupational allergy among farmers, but sensitisation has also been found in non-farming populations.

METHODS

A degenerate primer was designed to the N-terminal amino acid sequence of a 15-kD IgE-binding protein in A. siro extract. The cDNA sequence was obtained by using reverse transcriptase polymerase chain reaction, standard cloning and sequencing techniques. The protein was expressed in Escherichia coli with a 6-histidine tag at its C-terminus. Immunoblotting of the recombinant protein and whole extract was performed using patient sera.

RESULTS AND CONCLUSION

15 and 17-kD allergens were identified in a fraction of A. siro extract. The cDNA of the 15-kD allergen was isolated, cloned and sequenced and the allergen was expressed as a recombinant protein. The calculated molecular weight of the cDNA-encoded protein is 14.2 kD. The predicted amino acid sequence has one potential N-glycosylation site at position 4-6 and a cytosolic fatty acid-binding protein signature at position 5-22. The protein has 64% sequence identity with Blo t 13, an allergen from the dust mite Blomia tropicalis, as well as homology with several other fatty acid-binding proteins (FABPs) from different organisms. The allergen was named Aca s 13 and was recognised strongly by 3 of 13 (23%) of the subjects investigated. The amino acid sequence of the 17-kD protein was partly determined and it also showed high sequence homology with Blo t 13 and FABPs.

Clinical and immunologic aspects of storage mite allergy

Exposure to storage (nonpyroglyphid) mites has been increasingly recognized as a cause of asthma and rhinitis. Several species have been identified in Europe; e.g., Lepidoglyphus destructor, Acarus farris/siro, Tyrophagus spp., Glycyphagus domesticus, and Blomia tjibodas. Blomia tropicalis, on the other hand, predominates in subtropical and tropical areas. Studies from several countries have shown that IgE-mediated allergy in rural populations is of considerable importance and that storage mites are major allergens. Since these mites are found in homes, especially in regions with damp housing conditions, urban populations are at risk of becoming sensitized. Therefore, sensitization is not restricted only to those with occupational exposure. Several major allergens from storage mites have been identified and characterized. There seems to be a limited allergenic cross-reactivity between storage- and house dust mites. Molecular cloning has demonstrated that the Group 2 allergens from storage mites (Lep d 2 and Tyr p 2) show more than 40% sequence identity with the Group 2 allergens from Dermatophagoides spp. The availability of a large number of recombinant dust mite allergens will make it possible to investigate their homology and the number of allergens required for the diagnosis and treatment of storage mite allergy.

Exposure to an abundance of cat (Fel d 1) and dog (Can f 1) allergens in Swedish farming households

BACKGROUND

Earlier studies have shown that farmers are to a low degree sensitized to animal allergens. We have measured the amount of cat (Fel d 1) and dog (Can f 1) in farm households and examined the relationship between exposure and sensitization to cat and dog allergens.

METHODS

Dust samples from the homes of 403 farmers who had participated in an epidemiologic follow-up study on respiratory symptoms were analyzed for allergen content by two-site ELISA methods.

RESULTS

Fel d 1 was detected in 99.5% of the farmers' households ranging from 0.055 to 1455 microg/g dust in mattresses (GM 13.2) and to 3775 microg/g dust in living-room carpets (GM 17.1). Can f 1 was detected in 90.6% of the households from 0.2 to 116 microg/g dust in mattresses (GM 2.0) and to 504 microg/g dust in carpets (GM 4.3). Homes with pets present had the highest levels of the allergens (P<0.001). A total of 8.4% and 7.4% of the farmers were sensitized to cat and dog, respectively. A significant correlation was noted between exposure to the allergens and specific IgE to cat and dog, respectively (P<0.001). Sensitization to cat (OR = 4.9) and dog (OR = 17.8) was significantly associated with asthma.

CONCLUSIONS

In spite of the abundance of Fel d 1 and Can f 1, farmers are only to a low degree sensitized to cats and dogs.