The role and remediation of animal allergens in allergic diseases

Recommendations for asthma monitoring in children: A PeARL document endorsed by APAPARI, EAACI, INTERASMA, REG, and WAO

Monitoring is a major component of asthma management in children. Regular monitoring allows for diagnosis confirmation, treatment optimization, and natural history review. Numerous factors that may affect disease activity and patient well-being need to be monitored: response and adherence to treatment, disease control, disease progression, comorbidities, quality of life, medication side-effects, allergen and irritant exposures, diet and more. However, the prioritization of such factors and the selection of relevant assessment tools is an unmet need. Furthermore, rapidly developing technologies promise new opportunities for closer, or even "real-time," monitoring between visits. Following an approach that included needs assessment, evidence appraisal, and Delphi consensus, the PeARL Think Tank, in collaboration with major international professional and patient organizations, has developed a set of 24 recommendations on pediatric asthma monitoring, to support healthcare professionals in decision-making and care pathway design.

Horse allergy: Curly Horses can mediate immune tolerance

American Bashkir Curly Horses are claimed to be hypoallergenic, but this has not been clinically proven. In the present study, the effect of exposure to Curly Horses was investigated in 141 patients allergic to horses by measuring their lung function and nasal patency during Curly Horse contact. Continuous contact with Curly Horses, including riding and brushing, decreased the allergic riders' reactivity as measured by FEV1, PEF, and PNIF. Subsequent visits (up to 40 or more hours of riding) further reduced reactivity to the Curly Horses. Allergic events to horses occurred only in 72 out of 1312 riding hours, mainly in the first ten riding hours.In 41 out of the 141 patients, it was further investigated whether repeated exposure to Curly Horses could induce tolerance to other horses. Patients in the tolerance induction study were tested annually for horse allergy using a nasal provocation test. The tolerance induction study showed that exposure to Curly Horses induced immune tolerance to other horses in 88% of patients who completed the study.To understand the mechanism causing hypoallergenicity, we performed IgE immunoblots to determine whether Curly Horse hairs contain IgE binding proteins. However, no differences in IgE reactivity were found between Curly and non-Curly Horses. Moreover, the immune tolerance induction study patients did not show decreased IgE reactivity to hairs from Curly or non-Curly Horses even though patients had developed tolerance. However, we did find increasing levels of anti-horse IgG antibodies in the study patients.Overall, our data strongly suggests that continuous exposure to Curly Horses can induce immune tolerance, rendering these patients non-reactive to horses. The reason for the reduced clinical allergenicity of Curly Horses remains unclear, but the data suggest that blocking IgG antibodies may be of importance for immune tolerance development.

[Allergenic and chemical pollutants of indoor environments and asthma: Characterization, assessment and eviction]

The environment of an asthmatic patient can contain numerous sources of pollutants that degrade the quality of indoor air and have major repercussions on the occurrence and control of asthma. Assessment and improvement of the quality of indoor air should be assigned a major role in pneumology and allergology consultations. Characterization of an asthmatic's environment entails a search for biological pollutants with mite allergens, mildew, and allergens resulting from the proximity of pets. It is important to evaluate the chemical pollution represented by exposure to volatile organic compounds, which are increasingly present in our lodgings. Active or second-hand smoking must in all circumstances be sought out and quantified. Assessment of the environment is mediated by several methods, of which the application depends not only on the pollutant sought out, but also on enzyme-linked immunosorbent assay (ELISA), which has an essential role in quantification of biological pollutants. Attempts at expulsion of the different indoor environment pollutants is mediated by indoor environment advisors, whose efforts are aimed at obtaining reliable evaluation and control of indoor air. Implemented as a form of tertiary prevention, their methods are conducive to improved asthma control, in adults as well as children.

Exposure to household dust, allergens, and endotoxin and allergy-related outcomes alternation in the general U.S. population

It has been widely reported that the general population was at an increased risk of allergy diseases, which probably be related with household allergens exposure. However, the difference of local and systemic allergic reactions exposure to allergens has not been reported in the general population previously. The data of 1094 U.S. adults from the National Health and Nutrition Examination Survey (NHANES) 2005-2006 data bank were analyzed. Dust, allergens (Bia g 1, Bia g 2, Can f 1, Feld 1, Derp 1, Mus m 1, Rat n 1, Alternaria alternate, and Aspergillus fumigatus), and endotoxin, were measured to estimate sensitizing source exposure. And allergy-related outcomes indicators including hay fever, sneezing, allergic rhinitis (AR), immunoglobulin E (IgE), and allergic sensitization, were evaluzted to estimate local and systemic allergic reactions. Multiple linear regression and logistic regression models were used to examine the associations of sensitizer and allergy-related outcomes. The mean or median concentration of dust and endotoxin were 0.66 g and 12.98 EU/mg dust. The Derp 1, Mus m 1, Rat n 1, Alternaria alternate, and Aspergillus fumigatus were the main allergens in the dust, with the concentrations of 30.66 ng/g dust, 30.73 ng/g dust, 5.94 ng/g dust, 5.20 ng/g dust, and 207.68 μg/g dust, respectively. The prevalence of AR was 34.2% among the general population. After controlling for sociodemographic factors, we found that the allergens, such as Can f 1 and Feld 1, were positively associated with AR. The prevalence of allergic sensitization was about 20%. Dust and endotoxin were found positively associated with allergic sensitization, while Bia g 2, Rat n 1, Alternaria alternate, and Aspergillus fumigatus were inversely associated with that. Dust and endotoxin probably be associated with higher risk of local allergic reactions, while some allergens, such as Bia g 2, Rat n 1, Alternaria alternate, and Aspergillus fumigatus probably be associated with lower risk of systemic allergic reactions.

Biological activity of human IgE monoclonal antibodies targeting Der p 2, Fel d 1, Ara h 2 in basophil mediator release assays

Background

Human Immunoglobulin E monoclonal antibodies (hIgE mAb) are unique tools for investigating IgE responses. Here, the biological activity of hIgE mAb, derived from immortalized B cells harvested from the blood of allergic donors, targeting three allergens (Der p 2, Fel d 1 and Ara h 2) was investigated.

Methods

Three Der p 2-, three Fel d 1- and five Ara h 2-specific hIgE mAb produced by human B cell hybridomas, were combined in pairs and used to passively sensitize humanized rat basophilic leukemia cells and compared with sensitization using serum pools. Sensitized cells were stimulated with corresponding allergens (recombinant or purified), allergen extracts or structural homologs, having 40-88% sequence similarity, and compared for mediator (β-hexosaminidase) release.

Results

One, two and eight pairs of Der p 2-, Fel d 1- and Ara h 2-specific hIgE mAb, respectively, produced significant mediator release (>50%). A minimum hIgE mAb concentration of 15-30 kU/L and a minimum antigen concentration between 0.01-0.1 µg/mL were sufficient to induce a pronounced mediator release. Individual sensitization with one Ara h 2-specific hIgE mAb was able to induce crosslinking independently of a second specific hIgE mAb. Der p 2- and Ara h 2-specific mAb showed a high allergen specificity when compared to homologs. Mediator release from cells sensitized with hIgE mAb was comparable to serum sensitization.

Conclusion

The biological activity of hIgE mAb reported here provides the foundation for novel methods of standardization and quality control of allergen products and for mechanistic studies of IgE-mediated allergic diseases, using hIgE mAb.

Evolutionary Biology and Gene Editing of Cat Allergen, Fel d 1

Allergy to domestic cat affects up to 15% of the population, and sensitization to cat allergen is associated with asthma. Despite the pervasiveness of cat allergic disease, current treatments have limited impact. Here, we present a bioinformatics analysis of the major cat allergen, Fel d 1, and demonstrate proof of principle for CRISPR gene editing of the allergen. Sequence and structural analyses of Fel d 1 from 50 domestic cats identified conserved coding regions in genes CH1 and CH2 suitable for CRISPR editing. Comparative analyses of Fel d 1 and orthologous sequences from eight exotic felid species determined relatively low-sequence identities for CH1 and CH2, and implied that the allergen may be nonessential for cats, given the apparent lack of evolutionary conservation. In vitro knockouts of domestic cat Fel d 1 using CRISPR-Cas9 yielded editing efficiencies of up to 55% and found no evidence of editing at predicted potential off-target sites. Taken together, our data indicate that Fel d 1 is both a rational and viable candidate for gene deletion, which may profoundly benefit cat allergy sufferers by removing the major allergen at the source.

New Frontiers: Precise Editing of Allergen Genes Using CRISPR

Genome engineering with clustered regularly interspaced short palindromic repeats (CRISPR) technology offers the unique potential for unequivocally deleting allergen genes at the source. Compared to prior gene editing approaches, CRISPR boasts substantial improvements in editing efficiency, throughput, and precision. CRISPR has demonstrated success in several clinical applications such as sickle cell disease and β-thalassemia, and preliminary knockout studies of allergenic proteins using CRISPR editing show promise. Given the advantages of CRISPR, as well as specific DNA targets in the allergen genes, CRISPR gene editing is a viable approach for tackling allergy, which may lead to significant disease improvement. This review will highlight recent applications of CRISPR editing of allergens, particularly cat allergen Fel d 1, and will discuss the advantages and limitations of this approach compared to existing treatment options.

Evaluation of The Safety and Efficacy of Newly Developed Domestic Allergenic Extracts for Skin Prick Testing

Background

Allergic disorders are common health problems worldwide with significant socio-economic impacts. The best diagnostic method using allergenic extract is the skin prick test. Regarding the effects of geo-climatic factors and allergenic extract source material quality, the aim of study was to determine the safety and efficacy of some in-house-developed allergenic extracts.

Methods

Forty-five different allergenic extracts, including common regional pollen, foods, and dog and cat hair, as well as positive and negative extracts, were prepared from domestic sources using optimum extraction methods. All extracts passed stability and sterility testing, and sterile final products containing 50% glycerin in 10 and 20 w/v concentrations were used. Skin prick testing was performed on volunteers and immediate or late side effects were recorded.

Results

In total, 56 students (mean age: 21.2±2.3y, M/F ratio: 1.07) participated in this study. For inhalant allergens, all extracts except dog hair extract caused positive responses. Salsola kali (Russian thistle) and Fraxinus velutina (ash tree) were the most common grass and tree pollen extracts, respectively. Of 18 different food extracts, five, including egg white, tomato, fig, melon, and green pepper caused skin reactivity in only one person. No participant reported any immediate or late side effects, including large local reaction or systemic response.

Conclusion

The result of the current study confirmed the safety of all our in-house-developed allergenic extracts. Regarding efficacy, almost all inhalant and five food allergens caused positive skin responses.

Effect of Exposure to Cats and Dogs on the Risk of Asthma and Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Controversies persist regarding whether exposure to cat or dog increases the risk of asthma and allergic rhinitis.

OBJECTIVE

This meta-analysis aimed to assess the associations between exposure to cats or dogs and the development of asthma and allergic rhinitis.

METHODS

A systematic review was performed to identify case-control and cohort studies before May 2019, evaluating the association between exposure to cats and dogs and the risk of asthma and rhinitis. The risk of bias was assessed using the Newcastle-Ottawa Scale. The odds ratios (ORs) and risk ratios (RRs) were pooled for case-control and cohort studies, respectively. Subgroup analyses were performed on prespecified study-level characteristics.

RESULTS

The meta-analysis of 34 cohort studies showed a protective role of exposure to cats [RR: 0.88, 95% confidence interval (CI): 0.77-0.99] or dogs (RR: 0.85, 95% CI: 0.73-0.97) in the development of asthma. The subgroup analysis of birth cohort (RR: 0.74, 95% CI: 0.56-0.93) and children population (RR: 0.83, 95% CI: 0.70-0.96) also suggested a favorable role of exposure to dogs in the development of asthma. Pooled evidence from 13 case-control studies indicated no significant impact of cats (OR: 1.66, 95% CI: 0.39-2.94) and dogs (OR: 1.22, 95% CI: 0.92-1.52) on the development of asthma. A pooled analysis of five cohort studies showed a favorable effect of exposure to cats (RR: 0.60, 95% CI: 0.33-0.86) or dogs (RR: 0.68, 95% CI 0.44-0.90) on the development of allergic rhinitis.

CONCLUSION

The findings indicated a protective effect of exposure to cats and dogs, especially ownership, on the development of asthma and allergic rhinitis.

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.

Cat ownership is associated with increased asthma prevalence and dog ownership with decreased spirometry values

The association between pet ownership and the development of allergic and respiratory diseases has been the aim of several studies, however, the effects of exposure in adults remain uncertain. The aims of the present study were to investigate the prevalence of asthma and lung function status among dog and cat owners. This cross-sectional study was performed at two universities with students and workers who were allocated into 3 groups according to pet ownership in the previous year: cat owners, dog owners, and no pets (control group). Subjects underwent spirometry, bronchial challenge test with mannitol, skin prick tests, and questionnaires about animal exposures and respiratory symptoms. Control group comprised 125 subjects; cat owner group, 51 subjects; and dog owner group, 140 subjects. Cat owners had increased asthma prevalence (defined by symptoms and positive bronchial challenge test), but no changes in lung function compared to the control group. The dog owner group had lower spirometry values (forced expiratory volume in one second and lower forced vital capacity), but similar asthma prevalence, compared to the control group. In the cat owner group, excess of asthma may have an immunological basis, since we found an association with atopy. Although we did not have endotoxin data from volunteers' households, we postulated that low values of lung function were associated to exposure to endotoxins present in environments exposed to dogs.

Prevalence of occupational exposure to asthmagens derived from animals, fish and/or shellfish among Australian workers

OBJECTIVE

Several animal, fish and/or shellfish derived substances encountered in the workplace can initiate or exacerbate asthma. The aims of this study were: to produce a population-based estimate of the current prevalence of occupational exposure to animal, fish and/or shellfish derived asthmagens, to identify the main circumstances of exposures and to identify occupations with the highest proportions of exposed respondents.

METHODS

We used data from the Australian Work Exposure Study-Asthma, a national telephone survey that investigated the current prevalence of occupational exposure to asthmagens among Australian workers. A web-based tool was used to collect job task information and assign exposure to asthmagens, including animal, fish and/or shellfish derived asthmagens. Prevalence ratios to determine risk factors for exposure were estimated using modified Poisson regression.

RESULTS

Of the 4878 respondents, 12.4% were exposed to asthmagens derived from animals, fish and/or shellfish. Exposure to these asthmagens was significantly higher in workers residing in regional and remote areas, compared with major cities. The main circumstance of exposure to animal derived asthmagens was through cleaning up rat/mice infestations, while the main circumstance of exposure to fish and/or shellfish derived asthmagens was through preparing and cooking salmon. Occupational groups with the highest proportion of exposure to animal or fish and/or shellfish derived asthmagens were farmers/animal workers and food workers, respectively.

CONCLUSIONS

This is the first study investigating occupational exposure to animal, fish and/or shellfish derived asthmagens in a nationwide working population. The results of this study can be used to inform the direction of occupational interventions and policies to reduce work-related asthma.

Mammalian raw materials used to produce allergen extracts

OBJECTIVE

To provide information about the complexity of skin-derived mammalian allergen extracts and recent advances made in their characterization and production.

DATA SOURCES

Original and review articles (involving nonfood allergy to mammals) published in indexed journals were searched in the PubMed database.

STUDY SELECTIONS

Studies were selected with the following criteria: novelty, species of the study, and date of publication.

RESULTS

The information provided will help in the understanding and the selection of the appropriate allergen source materials for the preparation of extracts for the diagnosis and treatment of allergic respiratory diseases induced by the inhalation of skin-derived mammalian allergens. The data presented herein suggest the presence of cross-reactive and species-specific allergens in extracts prepared from different mammalian dander. Dander should be strongly considered in the preparation of allergenic extracts not only of cats and dogs but also of other mammalian species.

CONCLUSION

New methods should be developed to estimate the relative quantities of specific allergens in the extracts. The current knowledge illustrates the complexity of these extracts, and more efforts should be undertaken to fully understand the wide spectrum of mammalian allergens.

Sensitization to common allergens among patients with allergies in major Iranian cities: a systematic review and meta-analysis

Various allergens are implicated in the pathogenesis of allergic diseases in different regions. This study attempted to identify the most common allergens among patients with allergies based on the results of skin prick tests in different parts of Iran. Relevant studies conducted from 2000 to 2016 were identified from the MEDLINE database. Six common groups of allergen types, including animal, cockroach, food, fungus, house dust mite, and pollen were considered. Subgroup analysis was performed to determine the prevalence of each type of allergen. The Egger test was used to assess publication bias. We included 44 studies in this meta-analysis. The overall prevalence of positive skin test results for at least one allergen was estimated to be 59% in patients with allergies in various parts of Iran. The number of patients was 11,646 (56% male and 44% female), with a mean age of 17.46±11.12 years. The most common allergen sources were pollen (47.0%), mites (35.2%), and food (15.3%). The prevalence of sensitization to food and cockroach allergens among children was greater than among adults. Pollen is the most common allergen sensitization in cities of Iran with a warm and dry climate; however, sensitization to house dust mites is predominant in northern and southern coastal areas of Iran.

Animal allergen sensitization in veterinarians and laboratory animal workers

BACKGROUND

Animals secrete allergens into the environment and exposure to these in the workplace may cause sensitization.

AIMS

To identify the frequency of animal allergen sensitization and symptoms in animal workers.

METHODS

Using skin prick tests (SPT), we assessed sensitization to 15 mammal and bird allergens in animal workers and controls. We also recorded symptoms and pulmonary function tests.

RESULTS

There were 100 animal workers and 50 controls included in the study. Thirty-six per cent of animal workers and 10% of controls had positive SPT (P < 0.001, odds ratio [OR] = 5.1, 95% CI 1.7-16.0). The most common sensitizations were to horse (16% in animal workers versus 0% in controls, P < 0.01), canary (16% in animal workers versus 2% in controls, P < 0.05, OR = 9.3, 95% CI 1.2-194), cattle (13% in animal workers versus 0% in controls, P < 0.05), cat (12% in animal workers versus 6% in controls, not significant), rabbit and hamster (10% each in animal workers versus 0% in controls, P < 0.05). Allergy symptoms were reported by 52 animal workers, but only 36 of them had positive SPT. Twelve animal workers had abnormal pulmonary function tests and six had positive SPT.

CONCLUSIONS

Animal workers are at high risk of occupational sensitization to animal allergens. Exposure should be minimized through control measures and worker education about the risks of exposure and sensitization.

Severe pulmonary exacerbation in cystic fibrosis caused by cat allergy

This paper describes a preschool child who had persistent symptoms suggestive of significant cystic fibrosis lung disease over a period of eighteen months following first isolation of Pseudomonas aeruginosa. Despite vigorous anti-infective treatment and extensive investigations seeking undetected infection, improvement only occurred once severe cat allergy was diagnosed and cats were removed from the household. Whilst infection is the most common cause of respiratory exacerbations in cystic fibrosis, this article serves as a reminder that it is important to consider non-infective pathologies when the response to anti-infective treatment is unexpectedly poor.

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.

Prevalence of allergic sensitization in the United States: results from the National Health and Nutrition Examination Survey (NHANES) 2005-2006

BACKGROUND

Allergic sensitization is an important risk factor for the development of atopic disease. The National Health and Nutrition Examination Survey (NHANES) 2005-2006 provides the most comprehensive information on IgE-mediated sensitization in the general US population.

OBJECTIVE

We investigated clustering, sociodemographic, and regional patterns of allergic sensitization and examined risk factors associated with IgE-mediated sensitization.

METHODS

Data for this cross-sectional analysis were obtained from NHANES 2005-2006. Participants aged 1 year or older (n = 9440) were tested for serum specific IgEs (sIgEs) to inhalant and food allergens; participants 6 years or older were tested for 19 sIgEs, and children aged 1 to 5 years were tested for 9 sIgEs. Serum samples were analyzed by using the ImmunoCAP System. Information on demographics and participants' characteristics was collected by means of questionnaire.

RESULTS

Of the study population aged 6 years and older, 44.6% had detectable sIgEs, whereas 36.2% of children aged 1 to 5 years were sensitized to 1 or more allergens. Allergen-specific IgEs clustered into 7 groups that might have largely reflected biological cross-reactivity. Although sensitization to individual allergens and allergen types showed regional variation, the overall prevalence of sensitization did not differ across census regions, except in early childhood. In multivariate modeling young age, male sex, non-Hispanic black race/ethnicity, geographic location (census region), and reported pet avoidance measures were most consistently associated with IgE-mediated sensitization.

CONCLUSIONS

The overall prevalence of allergic sensitization does not vary across US census regions, except in early life, although allergen-specific sensitization differs based on sociodemographic and regional factors. Biological cross-reactivity might be an important but not the sole contributor to the clustering of allergen-specific IgEs.

Direct and indirect exposure to horse: risk for sensitization and asthma

Most studies on the sensitization to horse allergens in populations without professional exposure have been carried out in geographical areas where the rate of horse ownership is high and horse riding is popular. Very few studies have been carried out in populations living in large urban areas. This gap in the literature probably reflects the widespread view that prevalence of horse-related allergy is low in urban populations because the latter are not regularly exposed to horses. On the contrary, we suggest that urban areas constitute a model useful to study potential modalities of exposure and sensitization to horse allergen by other routes of exposure than horse-riding. In this article, we describe the risks related to various modalities of exposure to horse allergen, clinical aspects of airway sensitization to horse allergens in patients living in urban areas, and non-occupational exposure to horse allergen. In addition, we illuminate some aspects related to dispersion of horse allergens from sources such as stables to indoor environments.

Anaphylaxis as a manifestation of horse allergy

Allergic disease induced by animal exposure is a common phenomenon worldwide. Whereas cat and dog dander exposure are well recognized as causative of allergic rhinitis, allergic asthma, and contact urticaria, horse allergy can present with anaphylaxis. Horse allergy is induced by exposure to the major horse allergens Equ 1 through 5. The severity of the symptoms may be related to the level of exposure. Greatest risk of anaphylaxis occurs in those sensitized patients who have large amounts of animal allergen exposure, such as when in a barn, or when an animal bite occurs exposing sensitized persons to large quantities of the animal allergen that resides in the saliva. Horse allergy may be successfully treated with allergen specific immunotherapy.

Fel d 1-derived peptide antigen desensitization shows a persistent treatment effect 1 year after the start of dosing: a randomized, placebo-controlled study

BACKGROUND

Allergic rhinoconjunctivitis is an increasingly common source of morbidity, with sensitivity to cats accounting for 10% to 15% of disease burden. Allergy to cats is also a major risk factor for the development of asthma.

OBJECTIVES

We sought to probe the persistence of the treatment effect of a novel F el d 1-derived peptide antigen desensitization (Cat-PAD) 1 year after the start of treatment in subjects with cat allergy-induced rhinoconjunctivitis after standardized allergen challenge.

METHODS

In a randomized, double-blind, placebo-controlled, parallel-group clinical trial, subjects attended an environmental exposure chamber in which they were exposed to cat allergen before and after treatment with 2 different regimens of Cat-PAD over a 3-month period. Clinical efficacy was assessed as a change in total rhinoconjunctivitis symptom scores 18 to 22 weeks and 50 to 54 weeks after the start of treatment.

RESULTS

Treatment with Cat-PAD showed greater efficacy with 4 administrations of a 6-nmol dose 4 weeks apart than with 8 administrations of a 3-nmol dose 2 weeks apart. The treatment effect of 6 nmol persisted 1 year after the start of treatment and was significantly different from that of 3 nmol (P = .0342) and placebo (P = .0104). The treatment effect was apparent on both nasal and ocular symptoms at 1 year.

CONCLUSIONS

A short course of Cat-PAD improves the ocular and nasal components of rhinoconjunctivitis symptoms in subjects with cat allergy, with the treatment effect persisting 1 year after the start of treatment.

Effects of omalizumab on changes in pulmonary function induced by controlled cat room challenge

BACKGROUND

Environmental exposure to cat allergen is common, and sensitization to cat allergens is strongly associated with asthma.

OBJECTIVE

We sought to examine the efficacy of omalizumab in preventing acute bronchoconstriction induced by environmental exposure to cat allergen.

METHODS

Patients with a history of cat allergen-induced asthma were randomized to treatment with omalizumab or placebo and exposed to cat allergen in a controlled chamber for up to 1 hour at baseline and after 16 weeks of treatment. The primary efficacy outcome was area under the curve for percentage decrease from prechallenge FEV(1) at week 16 for omalizumab-treated versus placebo-treated patients. FEV(1) was recorded before and every 10 minutes during the 1-hour challenge. Chest, nasal, and ocular symptoms were also monitored during cat chamber exposure as secondary end points.

RESULTS

The area under the curve for percentage decrease in FEV(1) was 15.2% per hour for omalizumab-treated patients (n = 32) and 27.3% per hour for placebo-treated patients (n = 33), reflecting 44% less reduction in FEV(1) and a treatment difference of -12.1% per hour (P = .0009; 95% CI, -19.0 to -5.2). Compared with placebo-treated patients, omalizumab-treated patients were also able to tolerate longer allergen exposure (P = .0006) and demonstrated significant reductions from prechallenge values in their chest symptom score (P < .0001) and nasal-ocular symptom score (P = .0002).

CONCLUSIONS

The severity of acute airway reactions and symptoms caused by controlled cat room exposure to allergens was significantly reduced by treatment with omalizumab.

Home and school environmental assessment and remediation

Children spend a considerable portion of their time indoors. Therefore, homes and schools are an important source of allergen exposure. Chronic exposure to the major indoor allergens can lead to allergic sensitization and provoke allergic symptoms in children. Environmental assessment is crucial for the identification and quantification of such allergens in indoor spaces. Reduction of allergen exposure below sensitization and symptom thresholds is possible with various remediation techniques. This article reviews and discusses evidence for the assessment and remediation of indoor allergens commonly found in homes and schools. A literature review was performed using the PubMed database for English-language articles published between January 1, 1980, and February 2009. Additional information was obtained from a review of recent textbooks and one professional society's webpage.

Horse allergens: An underestimated risk for allergic sensitization in an urban atopic population without occupational exposure

BACKGROUND

Data on allergic sensitization to horse allergen in modern urban areas are scarce. The aim of this study was to investigate the characteristics of allergic sensitization and the modality of exposure to horse allergens in atopic patients living in an urban area and without occupational exposure to horse and/or horse-derived materials.

METHODS

From among 1822 consecutive outpatients, we selected all subjects who had an immediate skin reaction to horse dander. We recorded the patients' clinical history including a meticulous evaluation of the possibility and eventual modality of horse exposure, and the results of skin-prick tests (SPT) and total/specific IgE antibody analyses.

RESULTS

Of 1201 SPT-positive patients, 35 (3.43%) were sensitized to horse dander. No patient was mono-sensitized. Six individuals reported having direct horse contact, 10 subjects had occasional contact with horse owners (indirect exposure), and 19 denied direct or indirect exposure to horses or horse allergens. Twenty of the 35 horse-sensitized patients reported both nasal and bronchial symptoms, 14 had rhinitis without asthma and one had asthma without rhinitis.

CONCLUSIONS

Our results suggest that allergic sensitization to horse allergens is more frequent than expected in urban-dwelling subjects without direct or occupational exposure to horses. Highly atopic individuals or individuals who are sensitized to common pet dander should undergo SPT and evaluation of serum specific IgE before starting activities involving regular contact with horses such as riding, and before entering environments associated with horses.

Production of recombinant allergens in plants

A large percentage of allergenic proteins are of plant origin. Hence, plant-based expression systems are considered ideal for the recombinant production of certain allergens. First attempts to establish production of plant-derived allergens in plants focused on transient expression in Nicotiana benthamiana infected with recombinant viral vectors. Accordingly, allergens from birch and mugwort pollen, as well as from apple have been expressed in plants. Production of house dust mite allergens has been achieved by Agrobacterium-mediated transformation of tobacco plants. Beside the use of plants as production systems, other approaches have focused on the development of edible vaccines expressing allergens or epitopes thereof, which bypasses the need of allergen purification. The potential of this approach has been convincingly demonstrated for transgenic rice seeds expressing seven dominant human T cell epitopes derived from Japanese cedar pollen allergens. Parallel to efforts in developing recombinant-based diagnostic and therapeutic reagents, different gene-silencing approaches have been used to decrease the expression of allergenic proteins in allergen sources. In this way hypoallergenic ryegrass, soybean, rice, apple, and tomato were developed.

Occupational allergic rhinoconjunctivitis and asthma to goat and cross-reactivity with cow epithelium

BACKGROUND

The development of sensitization and symptoms after the inhalation of epithelial allergens is common.

OBJECTIVES

To investigate the allergic response (in vivo and in vitro) of 3 individuals clinically sensitive and occupationally exposed to cow and goat and to evaluate the allergenic cross-reactivity between cow and goat epithelium extracts.

METHODS

Three patients--a butcher and 2 doctors in veterinary medicine--were evaluated. These patients reported allergic respiratory symptoms after occupational exposure to goats and cows. Extracts were prepared from epithelia of both animals. All the patients underwent organ-specific allergen challenges with cow and goat extracts. Four nasal and 2 bronchial challenges were conducted following standardized procedures.

RESULTS

All 3 patients had positive challenge results with the offending allergen extract. Specific IgE to goat allergens was detected in all patients. Several IgE-binding bands were detected. Inhibition assays (enzyme allergosorbent test and immunoblots) confirmed moderate-to-high cross-reactivity between goat and cow extracts.

CONCLUSIONS

We confirm clinical sensitivity and specific IgE binding to goat and cow allergens in occupationally exposed individuals. There was good correlation among the clinical history, exposure, and the laboratory findings.

How exposures to biologics influence the induction and incidence of asthma

A number of environmental factors can affect the development and severity of allergy and asthma; however, it can be argued that the most significant inhaled agents that modulate the development of these conditions are biologics. Sensitization to environmental allergens is an important risk factor for the development of asthma. Innate immune responses are often mediated by receptors on mononuclear cells whose primary ligands arise from microorganisms. Many pathogens, especially viruses, target epithelial cells and affect the host immune response to those pathogens. The acquired immune response to an allergen is influenced by the nature of the innate immune system. Products of innate immune responses to microbes promote T(H)1-acquired responses. In the absence of T(H)1 responses, T(H)2 responses can dominate. Central to T(H)1/T(H)2 balance is the composition of contaminants that derive from microbes. In this review we examine the biology of the response to allergens, viruses, and bacterial products in the context of the development of allergy and asthma.

Protective effect of montelukast on lower and upper respiratory tract responses to short-term cat allergen exposure

BACKGROUND

Challenge with short-term exposure to airborne cat allergen in sensitized patients produces pulmonary function changes and rhinitis symptoms.

OBJECTIVE

To determine the benefit of montelukast, 10 mg, for patients with concomitant asthma and allergic rhinitis as demonstrated by protection against both lower and upper airway responses to cat allergen challenge.

METHODS

This randomized, crossover study treated patients with montelukast vs placebo during two 2-week, double-blind treatment periods, separated by a 1-week washout period. After each treatment period, patients underwent a 60-minute or less exposure to high levels of airborne cat allergen. Lower and upper airway responses were measured by spirometry and symptom scores.

RESULTS

Of 52 patients with data from both treatment arms, 79% of patients taking montelukast and 67% taking placebo were exposed to the full 60-minute allergen challenge. Montelukast provided significant (P < or = .001) protection against allergen challenge in the lower airway coprimary end point of area under the curve during challenge (AUC0-60min) for percentage decrease in forced expiratory volume in 1 second: mean of 10.5% per hour and 14.7% per hour for montelukast and placebo, respectively. Although the effect on the overall nasal symptoms score (NSS) coprimary end point of AUC0-60min was not statistically significance (P = .12), nasal congestion during the challenge and NSS during recovery showed statistically significant (P = .048) protection by montelukast. Additional analyses of simultaneous lower and upper airway responses showed that more patients taking montelukast (22, 43%) vs placebo (13, 26%) were protected from both asthma and rhinitis (P = .02), with an odds ratio of 2.24 (95% CI, 1.16-4.32) in favor of montelukast.

CONCLUSIONS

Montelukast has a protective effect against both lower and upper airway responses during exposure to high levels of cat allergen.

Animal danders

Animals release proteins into their surroundings through secretions, as excretions, or as dander. The quantity of dander that is dispersed by cats, dogs, or humans is sufficient to supply food for dust mites and to supply easily measurable quantities of proteins in dust. Fel d 1, Can f 1, and human IgA or IgG can be found in microgram quantities in dust samples. Allergens also can accumulate from the urine of wild or pet rodents. For cats and dogs, the accumulation of dander particles is not related to the cleanliness of the animals. All animals, including humans, provide a fully adequate supply of organic material for bacterial growth in a carpet, provided conditions are sufficiently humid. The authors' preliminary results in Virginia do not find a significant difference in endotoxin between homes with or without animals. The likely explanation for the nonallergic IgG and IgG4 response to cat, dog, or rat allergens is high exposure to proteins from these animals. If the highest levels of cat allergen in a home can result in immunologic tolerance, it is unlikely that primary avoidance would be successful at reducing exposure. The data showing that 80% of Swedish children with cat allergies never had lived with a cat imply that the concentrations of cat allergen in schools or in houses without a cat are sufficient to cause sensitization. Primary prevention would be possible only on a community basis, which is unlikely to occur. Sensitization to cat, rat, dog, or mouse allergens consistently is associated with asthma. In symptomatic children with positive skin test results, there is a strong case for allergen avoidance and a clear need for controlled trials. Controlled trials of avoidance should include houses without cats and schools. Controlling exposure to cat allergens with the cat in situ requires aggressive measures, such as removing reservoirs, washing the cat, and air cleaning. Many allergic or symptomatic children who live with a cat do not have positive skin test results or positive IgE antibodies to cats. Avoidance measures related to animals should be recommended only for individuals with positive skin test results. Increasing evidence shows that exposure to cats, dogs, rats, and other animals can induce a form of immunologic tolerance without causing allergic disease, and it is important to understand why this change occurs with dander allergens rather than with all allergens. The most probable explanations are related to the form and quantity of airborne allergens.

Control of environmental allergens as a therapeutic approach

The first rule of environmental allergen control is that avoidance is appropriate for allergic patients with asthma. Although this rule is obvious to allergists, it frequently is not considered by families and physicians who are not trained in allergy. The next step in environmental avoidance is to determine the specific sensitivity of a patient. Clinically, practitioners have to address reduction of exposure to more than one allergen, and it is likely that the complexity of dealing with several treatment regimes decreases compliance.

Focus on cat allergen (Fel d 1): immunological and aerodynamic characteristics, modality of airway sensitization and avoidance strategies

The increasing frequency of pet ownership (especially cats) in many industrialized countries has raised the level of exposure to the allergens produced by these animals. Moreover, it is likely that modern energy-saving systems and the wide use of upholstered furniture has resulted in closer contact between cats (and their allergens) and humans. Many different methods have been developed to quantify the main cat allergen (Fel d 1) in settled dust and in ambient air. The threshold levels of cat allergen inducing sensitization or triggering respiratory symptoms in sensitized patients have been calculated in settled dust, but airborne amounts of Fel d 1 probably represent a more reliable index of allergen exposure. Noticeably, the amount of Fel d 1 may be relatively high also in confined environments where cats have never been kept. It has been demonstrated that clothes of cat owners are the main source for dispersal of allergens in cat-free environments. This fact may be of relevance, because recent studies have shown that allergic sensitization to cats is more likely to develop in children exposed to moderate levels of this allergen than in children exposed to high amounts of Fel d 1. The ubiquity of cat allergen may justify the common observation that allergen avoidance is often insufficient to reduce the risk of developing allergic sensitization and/or symptom exacerbation in highly susceptible patients. Further efforts are needed to improve the efficacy of Fel d 1 avoidance strategies to try to reduce the risk of allergic sensitization to this allergen.

Morbidity patterns among low-income wheezing infants

OBJECTIVE

This study describes morbidity attributable to wheezing illness in a multi-ethnic sample of low-income infants younger than age 2, and examines biological, environmental, and psychosocial correlates of morbidity indexes.

METHOD

Infants 9 to 24 months old, considered at risk for developing asthma on the basis of having had 3 or more health care contacts with documented wheezing, received comprehensive evaluations as part of an environmental intervention study. Baseline evaluations with the infants, their families, and their home environments focused on biological, environmental, and psychosocial factors that would potentially increase asthma risk for the children. At study entry, prior morbidity attributable to wheezing illness was assessed with caregiver reports of symptom frequency and severity and medication use, caregiver quality of life, and medical record documentation of hospitalizations and emergency department (ED) visits.

RESULTS

Forty-six percent of the infants had 1 or more hospitalizations and 59% had 2 or more ED visits since birth for wheezing illness. Foreign-born Hispanic families had significantly more ED visits for their children's wheezing illness than US-born Hispanic families, whites, or blacks, although they used fewer controller medications and they reported less illness severity. Multivariate analyses showed 3 biological factors, respiratory syncytial virus, elevated child IgE, and cockroach allergen in the home, were independently associated with hospitalizations within this sample. Similar analyses showed that ED visits were not associated with biological variables, but rather with caregivers with single parent status and smokers. Caregiver reports of wheezing illness severity were correlated with ED visits, but not with hospitalizations. Severity ratings were higher for children of mothers with asthma and for those whose caregivers had higher anxiety and stress. The only correlate of caregiver ratings of poor quality of life was high caregiver anxiety.

CONCLUSIONS

Ethnic and immigrant status was an important factor in morbidity attributable to infant wheezing illness. In addition to respiratory infection, both allergic processes and social variables were associated with morbidity as measured by health care utilization. Caregiver reports of illness severity were significantly correlated with psychosocial factors.

High-level expression of immunoreactive recombinant cat allergen (Fel d 1): Targeting to antigen-presenting cells

BACKGROUND

Cat allergen Fel d 1 is a heterodimer encoded by 2 separate genes that has been difficult to produce as a fully immunoreactive molecule.

OBJECTIVE

We sought to engineer recombinant (r) Fel d 1 with IgE and IgG antibody binding comparable with that of the natural allergen that could be targeted to antigen-presenting cells.

METHODS

The rFel d 1 chains were coexpressed in baculovirus, either linked to the anti-CD64 antibody H22 (rFel d 1 H22(+)) or alone (rFel d 1 H22 (-)). Binding of expressed allergens to mouse and human antibodies was compared with that of natural (n) Fel d 1 by means of enzyme immunoassay and antigen-binding and inhibition RIAs. Binding of rFel d 1 H22 (+) to the CD64 receptor on leukocyte subpopulations and on the THP -1 cell line was analyzed by means of flow cytometry.

RESULTS

The baculovirus-expressed allergens migrated with molecular weights of 49 kd (rFel d 1 H22(+)) and 22 kd (rFel d 1 H22 (-)). The rFel d 1 inhibited IgG antibody binding to nFel d 1 by greater than 95% and showed identical dose-dependent inhibition curves. There was an excellent quantitative correlation between IgE and IgG antibody binding to rFel d 1 and nFel d 1 in sera from patients with cat allergy (IgE: n = 258, r = > 0.72,P <.001). The rFel d 1 H22(+) bound to monocytes but not to lymphocytes or neutrophils, and binding of rFel d 1 H22(+) to THP-1 cells was inhibited by a soluble CD64 fusion protein.

CONCLUSIONS

Recombinant Fel d 1 chains have been successfully coexpressed as mature proteins with comparable immunoreactivities to nFel d 1. The rFel d 1 can be targeted to antigen-presenting cells through CD64. These constructs will facilitate structural studies of Fel d 1 and the development of improved allergy diagnostics and therapeutics.