Exposure to dog allergens and subsequent allergic sensitization: an updated review

Exposures in the Indoor Environment and Prevalence of Allergic Conditions in the United States of America

Our study examines the association of the presence of mildew, cockroaches, and pets in homes as well as household dust allergens with the prevalence and/or severity of allergic diseases. No study has concurrently assessed home environment exposures in relation to allergic conditions in the general US population. Data from 5409 participants from the 2005–2006 National Health and Nutrition Examination Survey (NHANES) living in their current homes for ≥one year were analyzed. Multivariate logistic regression analyses between home exposures and allergic diseases prevalence and severity were performed. In adjusted analyses, mildew was associated with higher current asthma, allergies, and allergic rhinitis prevalence; endotoxin, with higher current asthma prevalence; and dust Canis familiaris (Can f) 1, with higher allergic rhinitis prevalence. However, presence of cockroaches and dust Dermatophagoides farinae (Der f) 1 were associated, respectively, with lower current asthma and allergies prevalence. Presence of mildew, dust Der f1, Dermatophagoides pteronyssinus (Der p) 1, Felis domesticus (Fel d) 1, and endotoxin were all associated with asthma and/or wheeze severity. Non-atopic asthma was more frequent with mildew and/or musty smell dust and higher dust Fel d1 concentration, while atopic asthma was more prevalent with higher Can f1 and endotoxin concentrations in dust. This study confirms previous relationships and reports novel associations, generating hypotheses for future research.

Consensus document on dog and cat allergy

The prevalence of sensitization to dogs and cats varies by country, exposure time and predisposition to atopy. It is estimated that 26% of European adults coming to the clinic for suspected allergy to inhalant allergens are sensitized to cats and 27% to dogs. This document is intended to be a useful tool for clinicians involved in the management of people with dog or cat allergy. It was prepared from a consensus process based on the RAND/UCLA method. Following a literature review, it proposes various recommendations concerning the diagnosis and treatment of these patients, grounded in evidence and clinical experience. The diagnosis of dog and cat allergy is based on a medical history and physical examination that are consistent with each other and is confirmed with positive results on specific IgE skin tests. Sometimes, especially in polysensitized patients, molecular diagnosis is strongly recommended. Although the most advisable measure would be to avoid the animal, this is often impossible and associated with a major emotional impact. Furthermore, indirect exposure to allergens occurs in environments in which animals are not present. Immunotherapy is emerging as a potential solution to this problem, although further supporting studies are needed.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

A Review on the Role of Vitamin D in Asthma

Asthma, a major public health issue, is one of the most common diseases affecting millions of population globally. It is a chronic respiratory disease characterized by increased airway inflammation and hyper-responsiveness. Vitamin D is of particular interest in asthma due to its immunomodulatory effects. Serum 25-hydroxyvitamin D is found to be associated with a wide range of pulmonary diseases, including viral and bacterial respiratory infections, asthma, and cancer. Several researches have reported positive associations between vitamin D and asthma. On the other hand, others have reported contrasting effects of vitamin D on asthma.

This review provides an examination of current epidemiologic and experimental evidence of a causal association between vitamin D status and asthma or asthma exacerbations, including its probable protective mechanism. Most of the evidence regarding vitamin D and asthma is reported by observational studies. Therefore, results from the experimental trials of vitamin D supplementation are important as they can provide evidence for future recommendations about the significance of vitamin D for asthma. Moreover, the trials can be effective in assessing the correct dosage and safety of vitamin D supplementation when given in diverse age groups such as children, teenagers, and adults for prevention and treatment of asthma.

Protein expression and genetic variability of canine Can f 1 in golden and Labrador retriever service dogs

BACKGROUND

Valued for trainability in diverse tasks, dogs are the primary service animal used to assist individuals with disabilities. Despite their utility, many people in need of service dogs are sensitive to the primary dog allergen, Can f 1, encoded by the Lipocalin 1 gene (LCN1). Several organizations specifically breed service dogs to meet special needs and would like to reduce allergenic potential if possible. In this study, we evaluated the expression of Can f 1 protein and the inherent variability of LCN1 in two breeds used extensively as service dogs. Saliva samples from equal numbers of male and female Labrador retrievers (n = 12), golden retrievers (n = 12), and Labrador-golden crosses (n = 12) were collected 1 h after the morning meal. Can f 1 protein concentrations in the saliva were measured by ELISA, and the LCN1 5' and 3' UTRs and exons sequenced.

RESULTS

There was no sex effect (p > 0.2) nor time-of-day effect; however, Can f 1 protein levels varied by breed with Labrador retrievers being lower than golden retrievers (3.18 ± 0.51 and 5.35 ± 0.52 μg/ml, respectively, p < 0.0075), and the Labrador-golden crosses having intermediate levels (3.77 ± 0.48 μg/ml). Although several novel SNPs were identified in LCN1, there were no significant breed-specific sequence differences in the gene and no association of LCN1 genotypes with Can f 1 expression.

CONCLUSIONS

As service dogs, Labrador retrievers likely have lower allergenic potential and, though there were no DNA sequence differences identified, classical genetic selection on the estimated breeding values associated with salivary Can f 1 expression may further reduce that potential.

Structural similarities of human and mammalian lipocalins, and their function in innate immunity and allergy

Owners and their domestic animals via skin shedding and secretions, mutually exchange microbiomes, potential pathogens and innate immune molecules. Among the latter especially lipocalins are multifaceted: they may have an immunomodulatory function and, furthermore, they represent one of the most important animal allergen families. The amino acid identities, as well as their structures by superposition modeling were compared among human lipocalins, hLCN1 and hLCN2, and most important animal lipocalin allergens, such as Can f 1, Can f 2 and Can f 4 from dog, Fel d 4 from cats, Bos d 5 from cow's milk, Equ c 1 from horses, and Mus m 1 from mice, all of them representing major allergens. The β-barrel fold with a central molecular pocket is similar among human and animal lipocalins. Thereby, lipocalins are able to transport a variety of biological ligands in their highly conserved calyx-like cavity, among them siderophores with the strongest known capability to complex iron (Fe(3+) ). Levels of human lipocalins are elevated in nonallergic inflammation and cancer, associated with innate immunoregulatory functions that critically depend on ligand load. Accordingly, deficient loading of lipocalin allergens establishes their capacity to induce Th2 hypersensitivity. Our similarity analysis of human and mammalian lipocalins highlights their function in innate immunity and allergy.

Dog and cat exposure and respective pet allergy in early childhood

BACKGROUND

The association of dog and cat exposure in early childhood with the incidence of respective allergies has remained controversial. The aim of the study was to obtain population-based evidence on the association of early exposure to dog or cat, or both, with dog and cat allergies.

METHODS

The study population was identified from the nationwide population register comprising all children aged 1-4 yr (N = 4779) born between 2001 and 2005 and living in the province of South Karelia, Finland. Cross-sectional questionnaire data on pet exposure in infancy and physician-diagnosed pet allergies were obtained from 3024 participants and merged with longitudinally accumulated data on sIgE and skin prick tests indicating allergic sensitization abstracted from all patient records in the area.

RESULTS

The adjusted relative incidence of positive test results (with 95% confidence intervals) was 2.69 (1.45-5.02) for dog and 5.03 (2.47-10.2) for cat allergens among children exposed to a respective pet alone compared with children without such exposure. The corresponding adjusted prevalence odds ratios for diagnosed dog and cat allergies were 1.75 (0.77-3.79) and 5.13 (2.30-11.4), respectively. The association between pet exposure and the incidence of positive test results was independent of parents' allergies.

CONCLUSIONS

Early exposure to dog and cat at home is associated with a higher incidence of respective pet allergy during the first four years of life. Further evidence from population-based studies with longer follow-up is required to justify any recommendation concerning early pet contacts with a view to preventing pet allergies later in life.

The role of the early-life environment in the development of allergic disease

A consensus has been reached that the development of allergic disorders is strongly influenced by early life exposures. An overview of several prenatal and early life factors that have been investigated for their associations with development of childhood allergy is presented. Delivery mode, the gut microbiome, vitamin D, folate, breastfeeding, pets, antibiotics, environmental tobacco smoke, and airborne traffic pollutants are discussed. Although many studies suggest an effect, overall, no risk factors clearly increase or reduce the risk of allergic outcomes.

Sparse modeling of spatial environmental variables associated with asthma

Geographically distributed environmental factors influence the burden of diseases such as asthma. Our objective was to identify sparse environmental variables associated with asthma diagnosis gathered from a large electronic health record (EHR) dataset while controlling for spatial variation. An EHR dataset from the University of Wisconsin's Family Medicine, Internal Medicine and Pediatrics Departments was obtained for 199,220 patients aged 5-50years over a three-year period. Each patient's home address was geocoded to one of 3456 geographic census block groups. Over one thousand block group variables were obtained from a commercial database. We developed a Sparse Spatial Environmental Analysis (SASEA). Using this method, the environmental variables were first dimensionally reduced with sparse principal component analysis. Logistic thin plate regression spline modeling was then used to identify block group variables associated with asthma from sparse principal components. The addresses of patients from the EHR dataset were distributed throughout the majority of Wisconsin's geography. Logistic thin plate regression spline modeling captured spatial variation of asthma. Four sparse principal components identified via model selection consisted of food at home, dog ownership, household size, and disposable income variables. In rural areas, dog ownership and renter occupied housing units from significant sparse principal components were associated with asthma. Our main contribution is the incorporation of sparsity in spatial modeling. SASEA sequentially added sparse principal components to Logistic thin plate regression spline modeling. This method allowed association of geographically distributed environmental factors with asthma using EHR and environmental datasets. SASEA can be applied to other diseases with environmental risk factors.

Babies Galore; or recent findings and future perspectives of pregnancy cohorts with a focus on immunity

Population-based pregnancy cohorts recruiting women before or at the moment of childbirth allow a longitudinal follow-up on children's health later in life. Important findings arising from pregnancy cohorts are discussed in the present review. These insights have led to revised guidelines on how to minimize disease risks in children, e.g., in the context of chronic immune diseases including allergies and asthma. Moreover, insights from pregnancy cohorts also unveiled a collateral effect of pregnancy on maternal immunity, mirrored by an ameliorated course of certain autoimmune diseases, but also an increased risk of infection with influenza A virus. Future pregnancy cohort studies are still required to close gaps in knowledge on how parameters involved in the developmental origin of health or poor immunity observed in children later in life are operational. We discuss here features that should be covered by future pregnancy cohort studies. Expected insights from such studies will then lay the foundation for biomarker discovery and offer opportunities for interventions to ameliorate adverse immune responses in humans.

Sensitization to aeroallergens in atopic dermatitis patients: association with concomitant allergic diseases

BACKGROUND

A few reports demonstrate the relationship between IgE sensitization to aeroallergens in atopic dermatitis (AD) patients and other allergic diseases and parameters.

OBJECTIVES

The objective of this study was to evaluate, if there is a significant relationship between the sensitization to common aeroallergens in AD patients and the occurrence of asthma bronchiale, rhinitis and other atopic parameters.

METHODS

Sensitization to dust, mites, animal dander and bird feather was examined (skin prick test, specific IgE) and the relationship with the occurrence of asthma bronchiale, rhinitis, duration of AD, family history and onset of AD was evaluated.

RESULTS

Two hundred and eighty-eight patients were examined - 90 men and 198 women. According to our results, IgE sensitization to animal dander, dust and mites may increase the risk of developing asthma or rhinitis. Persistent lesions of AD occur more often in patients with sensitization to animal dander, mites and dust. Patients with the sensitization to bird feather have the onset of AD more often above 5 years of age and in these patients, there is no relationship with the positive data about atopy in the family history.

CONCLUSION

There is a greater likelihood of developing other allergic diseases in atopic dermatitis patients who suffer from sensitisation to animal dander, mites, and dust. Thus, prompt management of atopic dermatitis and allergy to inhallant allergens that develop in early infancy may be a successful method for preventing of atopic march.

Severe childhood asthma and allergy to furry animals: refined assessment using molecular-based allergy diagnostics

BACKGROUND

Allergy to cats and dogs and polysensitization towards these animals are associated with severe childhood asthma. Molecular-based allergy diagnostics offers new opportunities for improved characterization and has been suggested to be particularly useful in patients with polysensitization and/or severe asthma. The aim was to use extract- and molecular-based allergy diagnostics to compare patterns of IgE sensitization towards aeroallergens in children with problematic severe and controlled asthma.

METHODS

Children with a positive ImmunoCAP towards any furry animal (cat, dog or horse) were recruited from a Nationwide Swedish study on severe childhood asthma. Severe (n = 37, age 13 years) and controlled (n = 28, age 14 years) asthmatics underwent assessment of allergic sensitization by ImmunoCap (kUA /l) and immunosolid-phase allergen chip (ISAC). In addition, Asthma Control Test, spirometry and a methacholine challenge were performed.

RESULTS

Children with severe asthma had lower asthma control (p < 0.001) and FEV1 (p = 0.001) and more bronchial hyper-responsiveness (p = 0.008) in spite of high doses of inhaled steroids (≥800 μg budesonide). Children with severe asthma displayed higher levels of IgE antibodies towards cat (17 vs. 3.9, p = 0.027), dog (3.8 vs. 1.2, p = 0.012) and horse (7.4 vs. 0.7, p = 0.014). Sensitization towards Can f 2 (22% vs. 0%, p = 0.009) and Equ c 1 (51% vs. 25%, p = 0.03) was more common in severe asthma. IgE levels towards Equ c 1 correlated with asthma control (r = -0.41, p = 0.04).

CONCLUSION

Children with severe allergic asthma had higher sIgE levels to cat, dog and horse. Molecular-based allergy diagnostics revealed a more complex molecular spreading of allergen components in children with the most severe disease.

A nationwide survey of inhalant allergens sensitization and levels of indoor major allergens in Korea

PURPOSE

The higher prevalence of respiratory allergic disease may be due to increased exposure to inhalation allergens. We conducted a survey of allergic diseases in autumn and winter with detection of major indoor allergens in major cities in Korea.

METHODS

We enrolled 110 subjects from the fourth Korea National Health and Nutrition Examination Survey with stratified, cluster, and systematic sampling procedures. All participants answered a health questionnaire as well as underwent a skin prick test (SPT) and ImmunoCAP for 11 indoor major allergens. We also measured the levels of 5 major allergens (Der f 1, Der p 1, Can f 1, Bla g 1, and Asp f 1) in fine indoor dust from the houses of 60 subjects with a 2-site ELISA.

RESULTS

The prevalence of allergic rhinitis and asthma were 25.5% and 7.3%, respectively. The most common sensitized allergens identified by SPT and ImmunoCAP were Dermatophagoides farinae (40.9%, 36.8%), followed by cockroach (23.6%, 19.5%), mugwort (13.6%, 22.9%), oak (9.1%, 22.9%), Japanese hop (9.1%, 8.6%), and dog dander (8.2%, 6.9%). There was a modest discrepancy between SPT and ImmunoCAP. Der f 1 and Der p 1 were detected in 91.7% and 45.0% of the enrolled houses, respectively. Der f 1 indicated high concentrations in all specific provinces in Korea; however, Der p 1 measured high only in the south. Dog dander allergens were present in 71.7% of houses; however, Bla g 1 was present in only 11.7% of houses and Asp f 1 was not detected in any houses.

CONCLUSIONS

The most important inhalant allergens in Korea are house dust mites followed by cockroach, mugwort, oak, Japanese hop, and dog dander in indoor environment, in which The dominant species of house dust mites were different according to region.

A cross-sectional analysis of pet-specific immunoglobulin E sensitization and allergic symptomatology and household pet keeping in a birth cohort population

It is unknown whether family members with detectable specific immunoglobulin E (sIgE) and/or allergic symptoms to pets are more or less likely to reside in a household with pets. We cross-sectionally investigated potential relationships between family members' allergic sensitization and symptoms to dogs and cats and current household pet-keeping practices, using birth cohort data. Blood samples taken from children enrolled in a birth cohort and their biological mothers and fathers, when the children were aged 18 years, were assessed for sIgE to dog and cat allergens. Interviews assessed subjects' self-reported pet exposure symptoms, current household pet-keeping practices, and socioeconomic characteristics. Overall, household dog or cat keeping was not associated with sIgE to these animals and/or self-reported allergic symptoms in the presence of these animals, even after controlling for factors such as education and household income. In subgroup analyses, current household dog keeping among dog-symptomatic teens (n = 40) was significantly lower than among teens who were not dog symptomatic (n = 289), at 48.8 and 61.1%, respectively (p = 0.036). Current household cat keeping was significantly lower among cat-symptomatic mothers (n = 27) compared with mothers who were not cat symptomatic (n = 120), at 24.3 and 37.0%, respectively (p = 0.015). However, when considering those who were both sensitized and reported symptoms, only the mother and cat-keeping associations persisted (p = 0.049). When cat-sensitized mothers report allergic symptoms to cats, these pets may be less likely to be kept in homes. Elevated dog and cat allergen sIgE does not appear to be associated with the keeping of these pets.

Mammalian-derived respiratory allergens - implications for diagnosis and therapy of individuals allergic to furry animals

Furry animals cause respiratory allergies in a significant proportion of the population. A majority of all mammalian allergens are spread as airborne particles, and several have been detected in environments where furry animals are not normally kept. The repertoire of allergens from each source belongs to a restricted number of allergen families. Classification of allergen families is particularly important for the characterization of allergenicity and cross-reactivity of allergens. In fact, major mammalian allergens are taken from only three protein families, i.e. the secretoglobin, lipocalin and kallikrein families. In particular, the lipocalin superfamily harbours major allergens in all important mammalian allergen sources, and cross-reactivity between lipocalin allergens may explain cross-species sensitization between mammals. The identification of single allergen components is of importance to improve diagnosis and therapy of allergic patients using component-resolved diagnostics and allergen-specific immunotherapy (ASIT) respectively. Major disadvantages with crude allergen extracts for these applications emphasize the benefits of careful characterization of individual allergens. Furthermore, detailed knowledge of the characteristics of an allergen is crucial to formulate attenuated allergy vaccines, e.g. hypoallergens. The diverse repertoires of individual allergens from different mammalian species influence the diagnostic potential and clinical efficacy of ASIT to furry animals. As such, detailed knowledge of individual allergens is essential for adequate clinical evaluation. This review compiles current knowledge of the allergen families of mammalian species, and discusses how this information may be used for improved diagnosis and therapy of individuals allergic to mammals.

Prenatal environmental factors influencing IgE levels, atopy and early asthma

PURPOSE OF REVIEW

There is increasing evidence that the prenatal window represents a critical period in which the developing immune system may be primed toward an allergic phenotype. Studies have investigated the role of a number of maternal environmental exposures on subsequent allergic disorders in the offspring. We summarize findings from recent studies on prenatal environmental factors influencing IgE levels, atopy, and early asthma.

RECENT FINDINGS

A building literature supports the influence of maternal exposure to environmental pollutants, such as allergens, traffic-related air pollution, tobacco smoke, and organochlorine compounds and social factors on allergic outcomes. More novel associations have been investigated, such as the effect of prenatal exposures to phthalates, bisphenol A, and magnetic fields. There is also rising interest in epigenetics as a pathway of action by which maternal exposure affect immune health.

SUMMARY

Emerging research highlights the challenges of investigating in-utero exposures and of relating exposures to such a heterogeneous and complex outcome as allergic disease. Further research is needed on the mechanisms by which prenatal exposure influences allergic response in childhood and how postnatal, familial and social factors, and sex can modify disease outcomes. Epigenetics is a promising new frontier, and likely one of several explanatory factors.

Microbial regulation of allergic responses to food

The incidence of food allergy in developed countries is rising at a rate that cannot be attributed to genetic variation alone. In this review, we discuss the environmental factors that may contribute to the increasing prevalence of potentially fatal anaphylactic responses to food. Decreased exposure to enteric infections due to advances in vaccination and sanitation, along with the adoption of high-fat (Western) diets, antibiotic use, Cesarean birth, and formula feeding of infants, have all been implicated in altering the enteric microbiome away from its ancestral state. This collection of resident commensal microbes performs many important physiological functions and plays a central role in the development of the immune system. We hypothesize that alterations in the microbiome interfere with immune system maturation, resulting in impairment of IgA production, reduced abundance of regulatory T cells, and Th2-skewing of baseline immune responses which drive aberrant responses to innocuous (food) antigens.