Environmental exposure to allergens of different dog breeds and relevance in allergological diagnostics

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.

Cat-NPC2, a Newly Identified Allergen, With High Cross-Reactivity to Can f 7

Purpose

Pet-derived allergens are the common indoor inhalant allergens. Among them, cat and dog allergens constitute more than 80% of animal allergic patients, which greatly affect the quality-of-life of patients and increase the burden of social health care. The aim of this study was to identify Cat-Niemann pick type C2 (NPC2) protein, a homologue of Can f 7, as a new allergen.

Methods

Cat-NPC2 complementary DNA (cDNA) was cloned and optimized for amplification and expression in Escherichia coli. Then, recombinant Cat-NPC2 (rCat-NPC2) was purified by Ni²⁺ affinity chromatography. The allergenicity was assessed by enzyme-linked immunosorbent assay (ELISA), western blot and basophil activation test (BAT). Based on the sequence similarity, the cross-reactivity between Cat-NPC2 and Can f 7 was investigated by inhibition ELISA. Circular dichroism spectroscopy and homology modeling were used to characterize the structure of Cat-NPC2.

Results

The cDNA sequence of Cat-NPC2 was cloned with a 450-bp open reading frame coding for 149 amino acids (GenBank MN_737596). The condon-optimized NPC2 gene was subcloned and expressed in E. coli with a molecular weight of 18.9 kDa. The native Cat-NPC2 was detected in cat dander extracts. The allergenicity determined by ELISA, western blot and BAT suggested at least 14.5% cat-allergic patients displayed high specific immunoglobulin E (IgE) recognition of Cat-NPC2. The predicted structure of Cat-NPC2 was found to consist of 7 β-strands arranged in 2 β-sheets. An ELISA based assay showed that rCat-NPC2 bound to cholesterol in a dose dependent manner. Based on the structure and sequence similarities, IgE cross-reactivity was demonstrated between Cat-NPC2 and Can f 7/Der f 2.

Conclusions

In the study, a novel cat allergen, belonging to the NPC2 protein family, was identified and characterized at both molecular and immunological levels. The study will offer a deeper understanding of cat allergens and improve a component-resolved diagnosis in pet allergy.

Dog-assisted therapy in the dental clinic: Part A-Hazards and assessment of potential risks to the health and safety of humans

Background

Dog-assisted therapy in the dental clinic may be an attractive alternative to sedation for anxious patients. Including a dental therapy dog in a clinical setting introduces new hazards and potential risks to health and safety for both humans and animal.

Objectives

The study aims to describe potential hazards associated with risks to humans by having a therapy dog present in the dental clinic and to provide guidance on best practices to minimise and control risks for the patients, the dentist, and the dental clinic staff.

Materials and Methods

Literature searches in Medline, http://Clinicaltrials.gov, and Google Scholar for qualitative and quantitative assessments of hazards and risks associated with the use of therapy dogs in health care settings, in combination with a review of the reference list of the included studies. Identified hazards and risks were analysed with respect for the health and welfare of humans in a dental clinic setting that involves the presence of a therapy dog.

Results

Potential risks to health and safety for humans in dental clinics that offer dog-assisted therapy can be categorised within four general categories of hazards: the dog as a source of zoonotic pathogens and human diseases, exposure to canine allergens, adverse animal behaviour, and dangers associated with high activity in a congested dental clinic operatory. Risks to humans are reduced by maintaining awareness amongst the dental clinic staff and the dog handler of all potential hazards in the dental clinic, and on how to reduce these hazards as well as adverse events that may scare the dental therapy dog.

Conclusions

Risks to the health and safety of humans in the presence of therapy dog in the clinics are present but are low if the dental clinical staff and dog handlers comply with best practices.

Regional differences in the prevalence of sensitization to environmental allergens: Analysis on IgE antibody testing conducted at major clinical testing laboratories throughout Japan from 2002 to 2011

BACKGROUND

Identification of sensitized allergens for patients with respiratory allergy is an important step in disease care and environmental allergen control. The Japanese archipelago belongs to various climate categories due to its length from north to south which transverse the subarctic in the north to the subtropical in the south, suggesting substantial regional differences in dominant environmental allergens. However, few studies have assessed the regional differences in the prevalence of sensitization to environmental allergens.

METHODS

We requested three major clinical testing laboratories to provide us with summarized results of antigen-specific IgE-antibody (Ab) measurements. These measurements were collected for clinical purposes throughout Japan from 2002 through 2011. The prevalence of positivity for IgE-Ab against 19 environmental allergens was calculated for each prefecture in order to evaluate regional differences.

RESULTS

Test data on specific IgE-Ab of 19,969,753 orders were analyzed. The prevalence of positivity for house dust mites was high and the regional difference was low, whereas apparent regional differences were found for pollen, insects, and fungi. The prevalence of positivity for Japanese cedar was low in Hokkaido and Okinawa, while those to alder was highest in Hokkaido. Higher prevalence for insects was observed in southern areas (Okinawa and prefectures in Kyusyu).

CONCLUSIONS

Findings of this study clearly demonstrated regional differences in the prevalence of sensitization to environmental allergens in Japan and the study also provides useful information for the clinician when deciding which allergens should preferentially be measured for IgE-Ab after considering regional difference.

Immunological methods for diagnosis and monitoring of IgE-mediated allergy caused by industrial sensitizing agents (IMExAllergy)

Industrial sensitizing agents (allergens) in living and working environments play an important role in eliciting type 1 allergic disorders including asthma and allergic rhinitis. Successful management of allergic diseases necessitates identifying their specific causes (ie, identify the causative agent(s) and the route of contact to allergen: airborne, or skin contact) to avoid further exposure. Identification of sensitization by a sensitive and validated measurement of specific IgE is an important step in the diagnosis. However, only a limited number of environmental and occupational allergens are available on the market for use in sIgE testing. Accordingly, specific in‐house testing by individual diagnostic and laboratory centers is often required. Currently, different immunological tests are in use at various diagnostic centers that often produce considerably divergent results, mostly due to lack of standardized allergen preparation and standardized procedures as well as inadequate quality control. Our review and meta‐analysis exhibited satisfactory performance of sIgE detection test for most high molecular weight (HMW) allergens with a pooled sensitivity of 0.74 and specificity of 0.71. However, for low molecular weight (LMW) allergens, pooled sensitivity is generally lower (0.28) and specificity higher (0.89) than for HMW tests. Major recommendations based on the presented data include diagnostic use of sIgE to HMW allergens. A negative sIgE result for LMW agents does not exclude sensitization. In addition, the requirements for full transparency of the content of allergen preparations with details on standardization and quality control are underlined. Development of standard operating procedures for in‐house sIgE assays, and clinical validation, centralized quality control and audits are emphasized. There is also a need for specialized laboratories to provide a custom service for the development of tests for the measurement of putative novel occupational allergens that are not commercially available.

Dog and Cat Allergies: Current State of Diagnostic Approaches and Challenges

Allergies to dogs and cats affect 10%-20% of the population worldwide and is a growing public health concern as these rates increase. Given the prevalence of detectable dog and cat allergens even in households without pets, there is a critical need to accurately diagnose and treat patients to reduce morbidity and mortality from exposure. The ability to diagnose cat sensitization is good, in contrast to dogs. Component resolved diagnostics of sensitization to individual allergenic proteins will dramatically improve diagnosis. This review focuses on the current state of knowledge regarding allergies to dogs and cats, recent advances, therapies such as subcutaneous immunotherapy, and discusses important areas to improve diagnosis and therapy.

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.

The NPC2 protein: A novel dog allergen

BACKGROUND

Dogs are an important source of indoor allergens that cause rhinoconjunctivitis, urticaria, and asthma in sensitized individuals. Can f 1 is reported as a major dog allergen, but other allergens have also been identified. Identification of immunologically important allergens is important for both the diagnosis and treatment of dog allergy.

OBJECTIVE

To identify and characterize the canine NPC2 protein, a novel dog allergen.

METHODS

We screened commercial and laboratory-generated aqueous dog extracts by 2-dimensional polyacrylamide gel electrophoresis with IgE immunoblotting using human serum samples from 71 dog-allergic individuals. A target of interest was excised from the gel and sequenced. Canine NPC2 sequence was generated, and recombinant proteins expressed in yeast and bacteria were used to determine allergenicity. An IgE enzyme-linked immunosorbent assay was used for screening 71 dog-positive and 30 dog-negative serum samples.

RESULTS

A 16-kDa protein (pK = 8.5) in dog allergen extracts was recognized by specific IgE. The protein was identified by sequencing as a CE1 protein or NPC2 protein. Human IgE bound to recombinant protein was expressed in both yeast and bacteria. Ten (14%) of 71 individuals had specific IgE to NPC2 protein from bacteria, and 12 (17%) had IgE to NPC2 protein from yeast. Binding of pooled dog-allergic serum IgE to the dust mite protein Der p 2 was partially inhibited by recombinant NPC2 protein.

CONCLUSION

NPC2 protein, a member of the MD-2-related lipid recognition family, is identified as a dog allergen (Can f 7), with an apparent seroprevalence of 10% to 20%.

Dog saliva - an important source of dog allergens

BACKGROUND

Allergy to dog (Canis familiaris) is a worldwide common cause of asthma and allergic rhinitis. However, dander extract in routine diagnostics is not an optimal predictor of IgE-mediated dog allergy. Our objective was to evaluate saliva as an allergen source for improved diagnostics of allergy to dog.

METHODS

IgE-binding proteins in dog saliva and dander extract were analysed by immunoblot and mass spectrometry (LC-MS/MS) using pooled or individual sera from dog-allergic patients (n = 13). Sera from 59 patients IgE positive to dander and 55 patients IgE negative to dander but with symptoms to dog were analysed for IgE against saliva and dander by ELISA. Basophil stimulation with dog saliva and dander extract was measured by flow cytometry among three dog-allergic patients. Additionally, IgE-binding protein profiles of saliva from different breeds were investigated by immunoblot.

RESULTS

Greater number and diversity of IgE-binding proteins was found in saliva compared to dander extract and varied among dog breeds. In saliva, Can f 1, 2, 3 and 6 were identified but also four new saliva allergen candidates. The majority of the 59 dog dander-positive sera (n = 44) were IgE positive to dog saliva. Among patients IgE negative to dander, but with symptoms to dog, 20% were IgE positive to saliva. The biological activity of saliva was confirmed by basophil degranulation.

CONCLUSIONS

Dog saliva is an allergen source for improved diagnostics of dog allergy. The IgE-binding protein profile of saliva from different dogs varies.

Dog allergen levels in homes with hypoallergenic compared with nonhypoallergenic dogs

BACKGROUND

Despite the public interest in hypoallergenic dogs, few scientific, including epidemiological studies have attempted to evaluate claims of hypoallergenicity. This study was designed to determine whether dog breeds reported as hypoallergenic correspond to lower dog allergen in the home versus nonhypoallergenic dogs.

METHODS

A web search was conducted to identify breeds cited as hypoallergenic. Four separate classification schemes using combinations of purebred and mixed breed dogs were used to compare the levels of Canis familiaris 1 in dust samples collected from homes with hypoallergenic versus nonhypoallergenic dogs from an established birth cohort.

RESULTS

No classification scheme showed that the level of dog allergen in homes with hypoallergenic dogs differed from other homes.

CONCLUSION

Dog-allergic individuals should have access to scientifically valid information on the level of allergen shedding of different breeds of dogs.

The complexities of defining atopy in severe childhood asthma

BACKGROUND

Defining atopy in children with severe, therapy-resistant asthma is complex. There is currently no gold standard test; both skin prick testing (SPT) and allergen-specific IgE (sIgE) are used. Furthermore, atopy is increasingly considered to be a spectrum, not an all-or-none phenomenon.

HYPOTHESIS

SPTs and sIgE cannot be used interchangeably, and if both tests are not performed, opportunities for intervention will be missed. Furthermore, the severity of atopy will be defined differently by the two tests.

METHODS

Cross-sectional study of 47 children with severe, therapy-resistant asthma, mean age 11.8 years, range 5.3-16.6 years, who underwent SPT, and measurement of total and sIgE as part of their clinical work-up.

RESULTS

Overall, 42/47 (89%) were atopic (defined as either one positive SPT or sIgE). There was 98% concordance between the two tests in classifying atopy. When each allergen was considered individually, in 40/200 (20%), the SPT and sIgE results were discordant, most commonly in 25/200 (12.5%), the SPT was negative and the sIgE was positive. House dust mite and cat sensitization were more likely detected by sIgE, but dog sensitization by SPT. When atopy was quantified, the sum of sIgEs compared with the sum of SPT weal diameter showed a moderate correlation (r(2) =0.44, P<0.001). Total IgE increased with an increasing number of positive sIgEs (P=0.028), but not significantly with increasing numbers of positive SPTs.

CONCLUSION AND CLINICAL RELEVANCE

SPT and sIgE identify group prevalence of atopy equally well; however, for individual allergens, concordance is poor, and when used to quantify atopy, SPTs and sIgE were only moderately correlated. In a clinical setting, if allergen avoidance is contemplated in children with severe, therapy-resistant asthma, both tests should be performed in order to detect sensitization.

Factors associated with furry pet ownership among patients with asthma

BACKGROUND

Exposure to indoor allergens is an established risk factor for poor asthma control. Current guidelines recommend removing pets from the home of patients with asthma.

OBJECTIVES

This cross-sectional study was conducted to determine the prevalence of furry pet ownership in asthmatics compared to non-asthmatics and to identify factors associated with furry pet ownership among those with asthma. Secondary analysis assessed characteristics among asthmatics that might be associated with allowing a furry pet into the bedroom.

METHODS

Using data from The National Asthma Survey collected from 2003 to 2004, we carried out univariate and multiple regression analyses, in 2009, to identify independent predictors of furry pet ownership in asthma sufferers after controlling for potential confounders.

RESULTS

Overall, asthmatics were more likely to own a furry pet than nonasthmatic individuals in the general population (49.9% versus 44.8%, p < .001). Multivariate analysis showed that female sex, older age, white race, and high income were independent predictors of furry pet ownership among asthmatics. Additionally, 68.7% of patients with asthma who own a furry pet allowed them into their bedroom. Higher income and carrying out < or =2 environmental control practices in the home were associated with increased likelihood of allowing a furry pet into the bedroom.

CONCLUSIONS

Furry pet ownership is equally or more common among asthmatics compared to those without asthma. The majority of asthmatics with furry pets allow them into the bedroom. Recognizing and addressing these problems may help decrease asthma morbidity.

Exposure to allergens of different cattle breeds and their relevance in occupational allergy

Introduction

Cattle are an important source of allergens in the working area of farmers. Asthma caused by cow allergens is a significant occupational problem. Yet in allergological testing, the results of in vivo and in vitro diagnostic tests are often inconsistent even in cases with clearly cattle-related symptoms.

Objectives and methods

The aim of this study was to investigate four different commercial cow allergen extracts and to compare them with self prepared extracts of different cattle breeds by means of SDS-PAGE and immunoblotting using the sera of 42 German farmers with asthma and rhino-conjunctivitis caused by cattle contact.

Results

The commercial extracts investigated in this study showed only minor differences in protein pattern. Using sera in immunoblotting experiments distinct bands were found for all symptomatic farmers, even in 13 farmers with a negative result in commercially available serological allergy tests. Bands with molecular weights in the range between about 11 and 67 kDa were observed; reactivity with the major allergen Bos d 2 at about 20 kDa was detected in all farmers, although it was not the strongest band in all cases.

Conclusions

We demonstrate for the first time the allergenic relevance of additional proteins with molecular weights of 14, 30, 55 and approx. 67–97 kDa in more than 50% of farmers with cattle related symptoms. One of our most striking results was that 32% of the investigated farmers with cattle related symptoms showed negative results with commercial serological tests but distinct reactions with cow allergen in immunoblotting experiments. The Bos d 2 content in hair showed differences between certain breeds whereas German Brown and Simmental had particularly higher quantities of Bos d 2 in their hair than breeds such as Holstein-Friesian. These results strongly support the following recommendation: test results with commercial extracts that are contradictory to the clinical symptoms should be supplemented by skin tests using extracts of the hair of the farmers’ own cattle.