Affinity purification of a major and a minor allergen from dog extract: serologic activity of affinity-purified Can f I and of Can f I-depleted extract

Children Monosensitized to Can f 5 Show Different Reactions to Male and Female Dog Allergen Extract Provocation: A Randomized Controlled Trial

BACKGROUND

Dog dander consists of several allergenic molecules including Can f 5, which is a protein expressed in the prostate of male dogs.

OBJECTIVE

To investigate whether children monosensitized to Can f 5 show different reactions to provocation tests with male versus female dog dander in a double-blind randomized clinical trial.

METHODS

Twenty-two children (15-18 years) with a history of dog sensitization were enrolled from the COpenhagen Prospective Studies on Asthma in Childhood₂₀₀₀ mother-child cohort. Skin prick test, specific IgE levels to dog dander (e5), and dog components Can f 1, 2, 3, and 5 were first assessed. We subsequently performed skin prick test and conjunctival allergen provocation test using dog dander collected separately from male and female dogs.

RESULTS

Seven of the 22 children were monosensitized to Can f 5. Eight were sensitized to a mix of the dog components, and 7 were no longer sensitized to dog. Of the children monosensitized to Can f 5, all had a positive skin prick test result to male dog extract and 1 of 7 was also positive to female dog extract (P = .01). Furthermore, 5 of 7 had a positive conjunctival allergen provocation test result to male dog extract and 1 of 7 also reacted to the female dog extract (P = .03). There was no difference between reactions to male and female dog extract provocation in children sensitized to a mix of the dog components.

CONCLUSIONS

Children monosensitized to Can f 5 show different reactions to male and female dog extract provocation using both skin prick test and conjunctival allergen provocation test, suggesting tolerance to female dogs.

Allergens in dog extracts: Implication for diagnosis and treatment

BACKGROUND

Five to ten percent of the population in affluent countries are allergic to dog. Diagnosis and treatment is based on allergen extracts from natural sources where composition and concentration are poorly defined.

OBJECTIVE

We aimed to quantify six dog allergens (Can f 1-6) in commercial skin prick test (SPT) solutions and to determine individual allergen profiles in dogs.

METHOD

The allergen content of SPT solutions from five vendors and allergen source material from three anatomical sites were analyzed. Fur and saliva samples were collected from a mixed population of 120 dogs. Can f 1-6 were quantified by inhibition ELISA using purified recombinant or natural allergens and polyclonal or monoclonal antibodies. Allergenicity was analyzed by basophil activation test.

RESULTS

Extensive variation in allergen composition was observed in commercial SPT vials resulting in a patient-dependent ability to activate basophils. Extract heterogeneity depended on collection site and allergen composition in individual dogs and source materials. Can f 2 and Can f 6 exhibited low levels in fur and SPT solutions, whereas Can f 4, which was the dominating allergen in fur samples, did not display similar high proportions in SPT solutions. Can f 3 varied most among SPT solutions.

CONCLUSION

There is a great variation of dog allergens in natural extracts raising questions of source, sampling, processing and ultimately of standardization and minimum allergen levels for accurate diagnosis and treatment.

Molecular allergy diagnostics refine characterization of children sensitized to dog dander

BACKGROUND

Sensitization to dog dander is an important risk factor for rhinoconjunctivitis and asthma but is not sufficient for diagnosing dog allergy. Molecular allergy diagnostics offer new opportunities for refined characterization.

OBJECTIVES

We sought to study the association between sensitization to all presently known dog allergen components and clinical symptoms of dog allergy in children evaluated by using nasal provocation tests (NPTs).

METHODS

Sixty children (age, 10-18 years) sensitized to dog dander extract underwent NPTs with dog dander extract. Measurement of IgE levels to dog dander and to Can f 1, Can f 2, Can f 3, and Can f 5 was performed with ImmunoCAP, and measurement of IgE levels to Can f 4 and Can f 6 was performed with streptavidin ImmunoCAP. An IgE level of 0.1 kU_A/L or greater was considered positive.

RESULTS

There was an association between sensitization to an increasing number of dog allergen components and a positive nasal challenge result (P = .01). Sensitization to lipocalins (odds ratio [OR], 6.0; 95% CI, 1.04-34.5), in particular Can f 4 (OR, 6.80; 95% CI 1.84-25.2) and Can f 6 (OR, 5.69; 95% CI, 1.59-20.8), was associated with a positive NPT result. Monosensitization to Can f 5 was related to a negative NPT result (OR, 5.78; 95% CI, 1.01-33.0).

CONCLUSION

Sensitization to an increasing number of dog allergen components and to lipocalins is associated with dog allergy. Monosensitization to Can f 5 should not be regarded primarily as a marker for dog allergy.

An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen

Background

Cats are the major source of indoor inhalant allergens after house dust mites. The global incidence of cat allergies is rising sharply, posing a major public health problem. Ten cat allergens have been identified. The major allergen responsible for symptoms is Fel d 1, a secretoglobin and not a lipocalin, making the cat a special case among mammals.

Main body

Given its clinical predominance, it is essential to have a good knowledge of this allergenic fraction, including its basic structure, to understand the new exciting diagnostic and therapeutic applications currently in development. The recent arrival of the component-resolved diagnosis, which uses molecular allergens, represents a unique opportunity to improve our understanding of the disease. Recombinant Fel d 1 is now available for in vitro diagnosis by the anti-Fel d 1 specific IgE assay. The first part of the review will seek to describe the recent advances related to Fel d 1 in terms of positive diagnosis and assessment of disease severity. In daily practice, anti-Fel d 1 IgE tend to replace those directed against the overall extract but is this attitude justified? We will look at the most recent arguments to try to answer this question. In parallel, a second revolution is taking place thanks to molecular engineering, which has allowed the development of various forms of recombinant Fel d 1 and which seeks to modify the immunomodulatory properties of the molecule and thus the clinical history of the disease via various modalities of anti-Fel d 1-specific immunotherapy. We will endeavor to give a clear and practical overview of all these trends.

An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen

Background

Cats are the major source of indoor inhalant allergens after house dust mites. The global incidence of cat allergies is rising sharply, posing a major public health problem. Ten cat allergens have been identified. The major allergen responsible for symptoms is Fel d 1, a secretoglobin and not a lipocalin, making the cat a special case among mammals.

Main body

Given its clinical predominance, it is essential to have a good knowledge of this allergenic fraction, including its basic structure, to understand the new exciting diagnostic and therapeutic applications currently in development. The recent arrival of the component-resolved diagnosis, which uses molecular allergens, represents a unique opportunity to improve our understanding of the disease. Recombinant Fel d 1 is now available for in vitro diagnosis by the anti-Fel d 1 specific IgE assay. The first part of the review will seek to describe the recent advances related to Fel d 1 in terms of positive diagnosis and assessment of disease severity. In daily practice, anti-Fel d 1 IgE tend to replace those directed against the overall extract but is this attitude justified? We will look at the most recent arguments to try to answer this question. In parallel, a second revolution is taking place thanks to molecular engineering, which has allowed the development of various forms of recombinant Fel d 1 and which seeks to modify the immunomodulatory properties of the molecule and thus the clinical history of the disease via various modalities of anti-Fel d 1-specific immunotherapy. We will endeavor to give a clear and practical overview of all these trends.

Indoor Allergens and Allergic Respiratory Disease

PURPOSE OF REVIEW

The purpose of this review is to evaluate the most recent findings on indoor allergens and their impact on allergic diseases.

RECENT FINDINGS

Indoor allergens are present inside buildings (home, work environment, school), and given the chronic nature of the exposures, indoor allergies tend to be associated with the development of asthma. The most common indoor allergens are derived from dust mites, cockroaches, mammals (including wild rodents and pets), and fungi. The advent of molecular biology and proteomics has led to the identification, cloning, and expression of new indoor allergens, which have facilitated research to elucidate their role in allergic diseases. This review is an update on new allergens and their molecular features, together with the most recent reports on their avoidance for allergy prevention and their use for diagnosis and treatment. Research progress on indoor allergens will result in the development of new diagnostic tools and design of coherent strategies for immunotherapy.

Particularities of allergy in the Tropics

Allergic diseases are distributed worldwide and their risk factors and triggers vary according to geographical and socioeconomic conditions. Allergies are frequent in the Tropics but aspects of their prevalence, natural history, risk factors, sensitizers and triggers are not well defined and some are expected to be different from those in temperate zone countries. The aim of this review is to investigate if allergic diseases in the Tropics have particularities that deserve special attention for research and clinical practice. Such information will help to form a better understanding of the pathogenesis, diagnosis and management of allergic diseases in the Tropics. As expected, we found particularities in the Tropics that merit further study because they strongly affect the natural history of common allergic diseases; most of them related to climate conditions that favor permanent exposure to mite allergens, helminth infections and stinging insects. In addition, we detected several unmet needs in important areas which should be investigated and solved by collaborative efforts led by the emergent research groups on allergy from tropical countries.

Indoor Allergens and Allergic Respiratory Disease

PURPOSE OF REVIEW

The purpose of this review is to evaluate the most recent findings on indoor allergens and their impact on allergic diseases.

RECENT FINDINGS

Indoor allergens are present inside buildings (home, work environment, school), and given the chronic nature of the exposures, indoor allergies tend to be associated with the development of asthma. The most common indoor allergens are derived from dust mites, cockroaches, mammals (including wild rodents and pets), and fungi. The advent of molecular biology and proteomics has led to the identification, cloning, and expression of new indoor allergens, which have facilitated research to elucidate their role in allergic diseases. This review is an update on new allergens and their molecular features, together with the most recent reports on their avoidance for allergy prevention and their use for diagnosis and treatment. Research progress on indoor allergens will result in the development of new diagnostic tools and design of coherent strategies for immunotherapy.

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.

Dog allergen immunotherapy: past, present, and future

OBJECTIVE

To review the published medical literature on dog allergy immunotherapy and discuss prior clinical trials, important allergens, extract specifics, and potential future treatment options for dog allergy relevant to the clinical allergist.

DATA SOURCES

MEDLINE search was performed using the terms dog, immunotherapy, and allergy limited to human studies from any period. Articles cited in selected studies also were reviewed for appropriateness of inclusion into this review.

STUDY SELECTIONS

Publications were included that were original research and fit the topic of dog allergen immunotherapy, specifically articles that investigated prior effectiveness and safety of dog allergen immunotherapy, dog extracts, identification of dog allergens, and current prescribing trends among allergists.

RESULTS

Two hundred fifteen articles were initially identified and 60 were reviewed in complete detail for inclusion in this review. The primary focus was placed on the 17 clinical trials that investigated the safety and efficacy of dog immunotherapy and the 19 studies that explored and defined the complex allergenic profile of dog extracts.

CONCLUSION

The medical literature on the use of dog extract immunotherapy in patients with hypersensitivity to dog shows poor and conflicting results of clinical efficacy, which has been attributed to poor-quality extracts and the inherent complex allergenic profile of dogs that remains without a clearly dominant allergen.

Historic overview of allergy research in the Netherlands

Research in allergy has a long history in the Netherlands, although the relation with immunology has not always been appreciated. In many aspects Dutch researchers have made major contribution in allergy research. This ranges from the first characterization of house dust mite as an important allergen, the first characterization of human Th2 and Th1 T cell clones, to the development of diagnostic test systems. In this overview Aalberse and Knol have made an overview of the major contributions of Dutch immunologists in allergy.

Structural aspects of dog allergies: the crystal structure of a dog dander allergen Can f 4

Four out of six officially recognized dog allergens are members of the lipocalin protein family. So far, a three-dimensional structure has been determined for only one dog allergen, Can f 2, which is a lipocalin protein. We present here the crystal structure of a second lipocalin allergen from dog, a variant of Can f 4. Moreover, we have compared and analyzed the structures of these two weakly homologous (amino acid identity 21%) dog allergens. The size and the amino acid composition of the ligand-binding pocket indicate that Can f 4 is capable of binding only relatively small hydrophobic molecules which are different from those that Can f 2 is able to bind. The crystal structure of Can f 4 contained both monomeric and dimeric forms of the allergen, suggesting that Can f 4 is able to form transient (weak) dimers. The existence of transient dimers in solution was confirmed by use of native mass spectrometry. The dimeric structure of Can f 4 is formed when the ends of four β-strands are packed against the same strands from the second monomer. The residues in the interface are mainly hydrophobic and the formation of the dimer is similar to the major horse allergen Equ c 1. Interestingly, the crystal structure of dog Can f 2 has been reported to show a different type of dimer formation. The capability of these allergens to form dimers may be important for the development of immediate allergic reaction (mast cell activation) because oligomeric allergens can effectively present multivalent epitopes.

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.

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.

Controversial role of pets in the development of atopy in children

BACKGROUND

Exposure to environmental allergens originating from different sources has been implicated in the sensitization to the respective allergens and development of atopic diseases. Keeping domestic animals is associated with exposure to relevant allergens but there are controversial data whether this exposure promotes or protects from the development of atopy.

DATA SOURCES

We herein reviewed the literature regarding the available data for the exposure to pets (cats and/or dogs) and the development of atopy. For this purpose, we searched the PubMed database.

RESULTS

This review attempts to answer the following questions that arise from the daily practice and the relevant studies, which are: a) is pet keeping associated with sensitization? b) is there an association between keeping pets and the development of asthma, allergic rhinitis and eczema, and, c) what is the underlying mechanism of any possible protective association? Despite the fact that several studies and meta-analyses have been conducted to explore the role of pets in the development of atopy, there are still conflicting pieces of evidence. It seems that there are different effects depending on the type of pets, the time and duration of exposure, and the genetic background of the individual.

CONCLUSION

Further appropriately designed birth cohort studies are needed to explore whether exposure to relevant allergens from pets promotes or protects from the development of atopy.

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.

A multi-allergen standard for the calibration of immunoassays: CREATE principles applied to eight purified allergens

BACKGROUND

Allergen measurements are widely used for environmental exposure assessments and for determining the potency of allergen vaccines, yet few purified allergen standards have been developed. The aim of the study was to develop a single standard containing multiple purified allergens that could be used in enzyme immunoassays and in multiplex arrays for the standardization of allergen measurements.

METHODS

Eight purified allergens were formulated into a single multi-allergen, or 'universal', standard based on amino acid analysis. Dose-response curves were compared with previous individual ELISA standards and allergen measurements of house dust extracts to obtain correction factors. Measured allergen concentrations were also modeled using linear regression, and the predictive accuracy was determined.

RESULTS

Parallel dose-response curves were obtained between the universal allergen standard and the individual ELISA standards, with close agreement between curves for 5/8 allergens. Quantitative differences of greater than twofold were observed for Fel d 1, Can f 1, and Der f 1, which were confirmed by the analysis of house dust extracts. Correction factors were developed that allowed ELISA data to be expressed in terms of the universal standard. Linear regression data confirmed the predictive accuracy of the universal standard.

CONCLUSION

This study shows that a single standard of eight purified allergens can be used to compare allergen measurements by immunoassay. This approach will improve the continuity of environmental exposure assessments and provide improved standardization of allergy diagnostics and vaccines used for immunotherapy.

Crystal structure of the dog lipocalin allergen Can f 2: implications for cross-reactivity to the cat allergen Fel d 4

The dog lipocalin allergen Can f 2 is an important cause of allergic sensitization in humans worldwide. Here, the first crystal structure of recombinant rCan f 2 at 1.45 A resolution displays a classical lipocalin fold with a conserved Gly-Xaa-Trp motif, in which Trp19 stabilizes the overall topology of the monomeric rCan f 2. Phe38 and Tyr84 localized on the L1 and L5 loops, respectively, control access to the highly hydrophobic calyx. Although the rCan f 2 calyx is nearly identical with the aero-allergens MUP1, Equ c 1 and A2U from mouse, horse and rat, respectively, no IgE cross-reactivity was found using sera from five mono-sensitized subjects. However, clear IgE cross-reactivity was demonstrated between Can f 2 and the cat allergen Fel d 4, although they share less than 22% sequence identity. This suggests a role for these allergens in co-sensitization between cat- and dog-allergic patients.

Prostatic kallikrein: a new major dog allergen

BACKGROUND

Dog dander is an important cause of respiratory allergy, but the spectrum of known dog allergens appears incomplete. Two lipocalins, Can f 1 and Can f 2, and serum albumin, Can f 3, have been characterized in detail but do not fully account for the IgE antibody-binding activity of dog dander extract. Allergen activity has previously been detected in dog urine but not further characterized.

OBJECTIVE

We sought to identify, characterize, and assess the importance of allergen components in dog urine.

METHODS

Dog urine was fractionated by means of size exclusion chromatography and examined for IgE antibody binding. A protein present in one fraction displaying IgE antibody-binding activity was identified by means of N-terminal sequencing and mass spectrometry. A recombinant form of the protein was produced in Pichia pastoris. IgE antibody binding to dog allergen components among sera of 37 subjects with dog allergy was determined by means of ImmunoCAP analysis.

RESULTS

An IgE antibody-binding protein was isolated from dog urine and identified as prostatic kallikrein. A closely related or identical protein was detected in dog dander. The recombinant prostatic kallikrein displayed immunologic and biochemical properties similar to those of the natural protein and bound IgE antibodies from 26 (70%) of 37 sera of subjects with dog allergy, 14 of which reacted to none of Can f 1, Can f 2, or Can f 3. The dog allergen identified here was found to cross-react with human prostate-specific antigen, a key culprit in IgE-mediated vaginal reactions to semen.

CONCLUSION

Prostatic kallikrein is a new major dog allergen.

Hydrophilic fungi and ergosterol associated with respiratory illness in a water-damaged building

BACKGROUND

Damp building-related respiratory illnesses are an important public health issue.

OBJECTIVE

We compared three respiratory case groups defined by questionnaire responses [200 respiratory cases, 123 of the respiratory cases who met the epidemiologic asthma definition, and 49 of the epidemiologic asthma cases who had current physician-diagnosed asthma with post-occupancy onset] to a comparison group of 152 asymptomatic employees in an office building with a history of water damage.

METHODS

We analyzed dust samples collected from floors and chairs of 323 cases and comparisons for culturable fungi, ergosterol, endotoxin, and cat and dog allergens. We examined associations of total fungi, hydrophilic fungi (requiring water activity > or = 0.9), and ergosterol with the health outcomes using logistic regression models.

RESULTS

In models adjusted for demographics, respiratory illnesses showed significant linear exposure-response relationships to total culturable fungi [interquartile range odds ratios (IQR-OR) = 1.37-1.72], hydrophilic fungi (IQR-OR = 1.45-2.19), and ergosterol (IQR-OR = 1.54-1.60) in floor and chair dusts. Of three outcomes analyzed, current asthma with postoccupancy physician diagnosis was most strongly associated with exposure to hydrophilic fungi in models adjusted for ergosterol, endotoxin, and demographics (IQR-OR = 2.09 for floor and 1.79 for chair dusts). Ergosterol levels in floor dust were significantly associated with epidemiologic asthma independent of culturable fungi (IQR-OR = 1.54-1.55).

CONCLUSIONS

Our findings extend the 2004 conclusions of the Institute of Medicine [Human health effects associated with damp indoor environments. In: Damp Indoor Spaces and Health. Washington DC:National Academies Press, 183-269] by showing that mold levels in dust were associated with new-onset asthma in this damp indoor environment. Hydrophilic fungi and ergosterol as measures of fungal biomass may have promise as markers of risk of building-related respiratory diseases in damp indoor environments.

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

In our environment, dogs are a relevant source of allergens, but diagnosing dog-related allergies may present difficulties, as in diagnostic tests with commercial dog allergens, some patients show only slight positive or negative results, even though they suffer from dog-related symptoms. Occasionally, allergy tests with extracts of dog hair belonging to patients' dogs or from dogs of the same breed were found to yield more reliable results, possibly due to breed-specific allergen components. The purpose of this study was to determine breed-specific differences or possibly hypo- or hyperallergenic dog breeds. The dog allergen content and protein patterns of different commercial and self-prepared dog allergen extracts were compared. Protein extracts were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and stained with silver. The major allergen Can f 1 was quantified using the commercially available enzyme-linked immunosorbent assay (ELISA) technique. The majority of the bands in the self-prepared extracts of different breeds had a molecular mass lower than 30 kD. Notably, the self-prepared extracts of hair of common breeds showed distinct protein bands with a molecular mass lower than 14 kD, which the commercial extracts did not. With regard to Can f 1 content, a marked variability occurred. Factors related to individual dogs seem to influence the allergenicity more than breed or gender. This is the first report to describe allergens with low molecular mass that are absent in extracts of commercial test kits. Consequently, skin tests with self-prepared dog allergen extracts need to be performed in case of inconsistent test results with commercial extracts.

Allergy to human seminal fluid: cross-reactivity with dog dander

BACKGROUND

Human seminal plasma (HSP) allergy is uncommon, with symptoms ranging from vulvovaginal pruritus to life-threatening anaphylaxis. Although several seminal plasma allergens have been reported and their molecular masses have been estimated to range between 12 and 75 kd, the prostate-specific antigen (PSA) has recently been identified as a causative allergen. Given that in a large number of cases symptoms appeared during or after the first intercourse, a cross-reactivity phenomenon might be implicated.

OBJECTIVE

We sought to assess the presence of IgE cross-reactivity among proteins from dog epithelium and HSP and to attempt to identify the allergens involved.

METHODS

Forty-one patients with dog epithelium allergy were selected. One of them experienced anaphylaxis in contact with her husband's seminal plasma. Skin prick tests, serum specific IgE measurements, SDS-PAGE immunoblotting, and inhibition tests were performed to study the pattern of IgE-binding proteins and the potential cross-reactivity between HSP and dog epithelium. Mass spectrometry was carried out to identify the protein involved in allergy reactions.

RESULTS

Twenty-four percent of the sera from patients with dog epithelium allergy recognized an IgE-binding band of 28 kd in HSP immunoblotting. Mass spectrometry identified this band as the PSA. SDS-PAGE immunoblotting-inhibition showed a complete IgE-binding inhibition when sera from these patients were preincubated with dog dander extract.

CONCLUSIONS

IgE cross-reactivity among proteins from dog dander and human PSA is demonstrated.

Characterization of Dog Allergens Can f 1 and Can f 2. 2. A Comparison of Can f 1 with Can f 2 Regarding Their Biochemical and Immunological Properties

BACKGROUND

The major dog allergens, Can f 1 and Can f 2, are members of the lipocalin protein family. The characterization of both dog allergens is still not complete. Their deduced amino acid sequences indicate the presence of three cysteine residues, probably connected with a disulfide bridge. We compared the biochemical and immunological properties of Can f 1 with those of Can f 2 using gel filtration, electrophoresis, and immunological assays.

METHODS

The rCan f 1, rCan f 2 and dog salivary proteins containing natural Can f 1 and Can f 2 were analyzed by HPLC gel filtration. The recombinant Can f 1 (rCan f 1) and rCan f 2 were analyzed by native and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) with or without reduction. The binding ability of rabbit IgG purified by protein G affinity chromatography from the antiserum against rCan f 1 and rCan f 2 was examined after a reduction in the recombinant allergens. The immunological cross-reaction between rCan f 1 and rCan f 2 was examined by an enzyme-linked immunosorbent assay (ELISA) using the rabbit IgG against rCan f 1 and rCan f 2. The cross-reaction of human IgE in the serum of a patient with dog allergy between rCan f 1 and rCan f 2 was also analyzed by competitive ELISA.

RESULTS

The molecular weights of rCan f 1 and of rCan f 2 were 18 and 21 kDa, respectively, using SDS-PAGE under reducing conditions, but the natural Can f 1 and Can f 2 were separated by HPLC gel filtration into fractions containing proteins of 31 and 34 kDa, respectively. rCan f 1 and rCan f 2 migrated as multiple bands (30-100 kDa) in native PAGE in the presence or absence of a reductant. The molecular weights of natural Can f 1 and of Can f 2 were 20 and 23 kDa, respectively, in SDS-PAGE under reducing conditions. The ability of rabbit IgG to bind to rCan f 1 and rCan f 2 increased after the reduction of the recombinant allergens. The rabbit IgG against rCan f 1 bound to rCan f 2. Cross-reaction of human IgE was observed between rCan f 1 and rCan f 2.

CONCLUSIONS

In the native and recombinant forms, Can f 1 and Can f 2 possessed a dimer structure under natural (non-reduced) condition. The dimers of Can f 1 and of Can f 2 were not built with a disulfide bridge but by non-covalent association. Cleavage of a disulfide bond of rCan f 1 and rCan f 2 increased the ability of binding of rabbit IgG to the allergens. The cross-reactivity of rabbit IgG and human IgE between rCan f 1 and rCan f 2 indicates that the same epitope(s) was present in Can f 1 and Can f 2.

Characterization of dog allergens Can f 1 and Can f 2. 1. Preparation of their recombinant proteins and antibodies

BACKGROUND

Recombinant dog allergens, rCan f 1 and rCan f 2, and their antibodies are good tools for the characterization of dog allergens in order to develop modern therapeutic and preventive methods for dog allergy.

METHODS

In this study, cDNA was synthesized from the mRNA of dog salivary glands and cloned into the pGEX4T vector. rCan f 1 and rCan f 2 containing glutathione S-transferase were prepared by an Escherichia coli expression system. The antibodies against the recombinant allergens were prepared in rabbit. The serum of patients with dog allergy was evaluated by ELISA and immunoblot, using the recombinant allergens, goat anti-human immunoglobulin (Ig) E (epsilon) labeled with biotin, and enzyme-labeled streptavidin. The binding of IgE in the serum of patients with dog allergy to dog saliva as a natural antigen was determined in the presence or absence of dog saliva, rCan f 1 and rCan f 2 as competitors. The anaphylactic potential of rCan f 1 and rCan f 2 was evaluated. The body temperature of the mice sensitized with rCan f 1 and rCan f 2 was monitored after intravenous injection of the allergens. The passive cutaneous anaphylaxis reaction was examined for rCan f 1 and rCan f 2. Dog salivary glands, dog saliva and dog hair/dander extracts were analyzed with antibodies by means of an immunoblot assay. The expression of the mRNA of Can f 1 and Can f 2 was verified in various dog tissues by reverse transcription polymerase chain reaction.

RESULTS

The E. coli expression system revealed the yield of rCan f 1 and rCan f 2 in 36 and 30 mg/l of culture. The molecular weights of rCan f 1 and rCan f 2 were 18 and 20 kDa in SDS-PAGE, respectively. rCan f 1 and rCan f 2 were found to bind to specific IgE in the serum of dog allergy patients. The binding of IgE in the patient serum for dog saliva was partially inhibited in the presence of rCan f 1 and rCan f 2. These recombinant allergens showed positive signals in passive cutaneous anaphylaxis reaction and induced anaphylactic shock in the mouse model, resulting in a decrease in body temperature. The polyclonal rabbit antibody for rCan f 1 bound to a protein of 20 kDa in the salivary gland, saliva and hair/dander extracts of dogs. The rabbit antibody for rCan f 2 bound to proteins in the saliva and the hair/dander extracts. The proteins possessed a molecular weight of 22/ 23 kDa. Reverse transcription polymerase chain reaction showed the presence of mRNA expression of Can f 1 and Can f 2 not only in the salivary gland but also in dog skin. A clear expression of Can f 2 mRNA was observed in dog skin.

CONCLUSIONS

The recombinant allergens and antibodies for Can f 1 and Can f 2 are available for immunological and biochemical characterization of dog allergens. The molecular weight of the natural Can f 1 and Can f 2 in dog saliva and hair/dander extracts showed a higher molecular weight than that of rCan f 1 and rCan f 2. The significance of dog skin as the tissue producing dog allergens, especially Can f 2, should be considered in further studies.

Assessment of indoor allergen exposure

Of the four modes of treating human allergic disease, avoidance or separation of the allergic patient from the allergen source is most effective and least expensive. The clinical immunology laboratory has established efficient and inexpensive "reservoir" dust sampling and processing procedures to obtain a surface dust specimen that reflects the allergen burden of the environment. Following extraction, allergens are quantified by reproducible, validated immunoenzymetric assays for the quantification of "indicator" aeroallergen levels in home, school, and work environments. In this paper, the strategies and methods for collecting and processing dust samples are discussed, and assays are reviewed for quantifying indoor aeroallergen exposure from dust mites (Der p 1 and 2, Der f 1 and 2), animals (cat: Fel d 1; dog: Can f 1; mouse: Mus m 1; rat: Rat n 1), and insects (cockroach: Bla g 1 and 2). Accurate quantification of the levels of allergen in indoor environments facilitates avoidance therapy by identifying environmental risk factors for asthma and allergy exacerbation and allowing the allergic patient to monitor the effectiveness of environmental remediation actions.

Dog factor differences in Can f 1 allergen production

BACKGROUND

The clinical importance of dog allergy is well known, but it is unknown if all types of dogs represent the same risk for allergic patients. The purpose of this work was to evaluate among 288 healthy dogs if the levels of Can f 1 on fur vary between breeds (German Shepherd, Pyrenean Shepherd, Poodle, Cocker spaniel, Spaniel, Griffon, Labrador retriever and Yorkshire terrier), gender, hormonal status, hair length, and according to the presence of seborrhea.

METHODS

Each dog was shaved in a limited area and Can f 1 concentrations were measured in mug/g fur by ELISA. The results (geometric mean values and 95% confidence intervals) were analyzed using analysis of variance and with nonparametric tests.

RESULTS

A wide variability in Can f 1 levels was found between dog breeds, from Labradors [1.99 (0.03-129.91)] to Yorkshires [16.72 (3.67-76.16)] and Poodles [17.04 (2.79-103.94)] but only the Labrador levels were significantly different from each other breed. Males produced more Can f 1 than females, 11.75 (1.27-108.40) vs 8.89 (0.91-86.39). No difference was found according to hair length or hormonal status. The seborrheic status highly (P = 0.0019) influenced the presence of Can f 1 on hair: 16.66 (1.59-173.96) vs 9.40 (1.03-85.70).

CONCLUSION

Breeds (Labrador retriever), sex and seborrhea seem to influence the levels of Can f 1 on fur.

Assessment of recombinant dog allergens Can f 1 and Can f 2 for the diagnosis of dog allergy

BACKGROUND

The use of recombinant allergens for the diagnosis and immunotherapy of allergy may offer several advantages over allergen extracts.

OBJECTIVE

To produce recombinant dog allergens Can f 1 and Can f 2 in Pichia pastoris yeast and to assess their suitability for the diagnosis of dog allergy.

METHODS

Clinically diagnosed dog-allergic patients' and healthy non-atopic dog owners' reactivities against recombinant Can f 1 and Can f 2 and commercial dog epithelial extract were studied by a panel of methods including skin prick test (SPT), ELISA and IgE immunoblotting.

RESULTS

Recombinant Can f 1 and Can f 2 were found immunologically functional: they bound dog-allergic patients' IgE in immunoblotting and inhibited specifically the binding of IgE to their natural counterparts in the dog allergen extract. Moreover, patients' IgE reactivity in immunoblotting to natural Can f 1 and their SPT with the recombinant allergen were perfectly concordant (phi coefficient 1.0, P<0.001). The concordance was slightly lower with recombinant Can f 2 (phi coefficient 0.92, P<0.001). A lower number of dog-allergic patients, 52%, reacted against Can f 1 than previously reported. About one-third of the patients reacted to Can f 2. In immunoblotting, the highest prevalence of reactivity, 60%, was directed to an 18 kDa component. Aminoterminal sequencing showed this to be a previously unidentified allergenic protein.

CONCLUSIONS

The recombinant allergens can be used reliably to identify Can f 1 and Can f 2-sensitized individuals. However, the two allergens are insufficient as reagents for diagnosing dog allergy.

Effect of environmental interventions to reduce exposure to asthma triggers in homes of low-income children in Seattle

The effectiveness of community health workers (CHWs) assisting families in reducing exposure to indoor asthma triggers has not been studied. In all, 274 low-income asthmatic children were randomly assigned to high- or low-intensity groups. CHWs visited all homes to assess exposures, develop action plans and provide bedding encasements. The higher-intensity group also received cleaning equipment and five to nine visits over a year focusing on asthma trigger reduction. The asthma trigger composite score decreased from 1.56 to 1.19 (Delta=-0.37, 95% CI 0.13, 0.61) in the higher-intensity group and from 1.63 to 1.43 in the low-intensity group (Delta=-0.20, 95% CI 0.004, 0.4). The difference in this measure due to the intervention was significant at the P=0.096 level. The higher-intensity group also showed improvement during the intervention year in measurements of condensation, roaches, moisture, cleaning behavior, dust weight, dust mite antigen, and total antigens above a cut point, effects not demonstrated in the low-intensity group. CHWs are effective in reducing asthma trigger exposure in low-income children. Further research is needed to determine the effectiveness of specific interventions and structural improvements on asthma trigger exposure and health.

Allergens, Der p 1, Der f 1, Fel d 1 and Can f 1, in newly bought mattresses for infants

BACKGROUND

To avoid allergen exposure of newborn babies, the use of a new mattress for the baby bed may be recommended. However, it is not certain that new mattresses are always free of allergens.

OBJECTIVE

In the present study the allergen content of new infant mattresses was investigated.

METHODS

Dust samples were vacuumed from 90 new mattresses for infant beds bought in 50 different Dutch shops, and the concentrations of Der p 1, Der f 1, Fel d 1 and Can f 1 were determined by radioimmunoassays.

RESULTS

Most mattresses contained some allergen and often the allergen concentrations were surprisingly high. Only 15 of the 90 mattresses contained no detectable amounts of any of the four allergens. The highest concentration found for each allergen was 3.1, 46.5, 20.2 and 95.7 microg/g of dust, respectively. However, the total amount of allergen in a mattress was still rather low because the new mattresses contained only modest amounts of dust. Baby mattresses more often contained an increased allergen load than the larger, standard-sized, infant mattresses. This may be caused by differences in manufacturing procedure. Also, mattresses that were sold without a plastic encasement more often contained an increased allergen load.

CONCLUSIONS

It is advisable to buy a mattress that is wrapped in plastic, but it may still contain a substantial amount of allergen. Thorough vacuuming of a newly bought mattress before it is installed on a child's bed, is also advisable. After instalment, regular vacuuming of the mattress and washing of the bed linen as well as measures to eliminate allergen reservoirs in other parts of the house are important, because our observations indicate that mattresses easily pick up allergens from the environment.

Animal allergens and their control

Animal allergens play a significant role in the pathogenesis of asthma and allergic rhinitis, and are potent causes of acute and chronic symptoms. Although cat and dog allergens are the most important, exposure to a wide variety of other furred animals is not uncommon. Recent reports state that 60% to 70% of households in the western world have at least one pet. Because of this significant exposure, hypersensitivity to animals has become increasingly important. This review focuses on the importance of animal allergens, concentrating on cat and dog allergens, but including others as well. It also discusses the pathogenesis, diagnosis, prevention, and management of animal allergy.

The role and remediation of animal allergens in allergic diseases

Animal allergens are common causes of both acute and chronic allergic disease. The most important animal allergens are derived from mammals, principally cats, dogs, rats, mice, horses, and cows, which secrete or excrete allergens into the environment. Allergic sensitization may occur at home or in the workplace. Cat and dog allergens commonly cause allergies in the home and affect the general population. Laboratory animal handlers often have allergic reactions to rats and mice. Cow dander allergy is usually caused by occupational exposure and occurs in farmers and farm workers. Horse allergy occurs among people who regularly handle horses, either professionally or for recreational purposes. Over the past 20 years, the major animal allergens have been defined and characterized with regard to their molecular structure, immunogenicity, and environmental distribution. One remarkable finding has been the fact that most of the mammalian allergens that have thus far been cloned belong to a single family of proteins called the lipocalins. In addition to these molecular similarities, it has also been shown that most of the animal allergens are quite similar with regard to their aerodynamic properties. Although much is yet to be learned, progress is being made in our knowledge regarding the steps that may be necessary to control exposure to these allergens through environmental modifications in both homes and occupational settings. These measures include source control, air filtration devices, barrier devices, removal of carpeting and other reservoirs, and, in some cases, washing of the animal.

Lipocalins as allergens

The term allergy refers to clinical conditions caused by an inappropriate immune response to innocuous proteins in genetically predisposed persons. Allergens of animal origin are responsible for a significant proportion of allergies. In recent years, it has become evident that practically all respiratory animal allergens characterized at the molecular level belong to the lipocalin family of proteins. The current list comprises the major allergens of horse, cow, dog, mouse, rat and cockroach as well as beta-lactoglobulin of cow's milk. While the molecular structure of all these allergens is known, far less information is available regarding their immunological characteristics. Knowing the way the immune system recognizes these allergens and reacts to them might, however, be the key for discovering the common denominator of the allergenicity of lipocalins. The human body contains numerous endogenous lipocalins, and the immune system has to adapt to their presence. We have proposed that under these conditions the immune response against the lipocalin allergens which are structurally related to endogenous lipocalins might be the pathway to allergy in genetically predisposed persons. The same might well apply also to other allergens with homologous endogenous counterparts.

The effect of air filtration on airborne dog allergen

BACKGROUND

Effective methods of reducing dog allergen are required to help alleviate symptoms in asthmatic patients sensitized to dog who refuse to part with their pet. The aim of this study was to investigate the use of the high efficiency particulate air (HEPA) filter air cleaner to reduce airborne Can f 1 in homes with a dog.

METHODS

The effect of a HEPA air cleaner was investigated in nine homes with a dog. Samples were collected from two rooms of each house concurrently, one of which contained the dog, on two separate days (active day - HEPA air cleaner on - and control day). Eight consecutive 1-h samples were collected from each room with a high-volume air sampler (airflow rate 60 l/ min). Can f 1 was determined by monoclonal-polyclonal antibody-based ELISA.

RESULTS

Baseline airborne Can f 1 levels were 3.8-fold greater when sampling was performed with a dog in the room (GM 27.1 ng Can f 1/m3, range 2.63-329) than when the dog was elsewhere in the house (GM 7.1 ng Can f 1/m3, range 0.69-27.2). When the dog was elsewhere in the house, airborne Can f 1 levels fell on both active and control days, but the magnitude of the reduction was significantly greater on the active days (P<0.05), and was approximately 90% from baseline. With the dog in the room, a significant fall in airborne Can f 1 was observed only on active days (75% from baseline), but not on control days (active vs control P<0.001).

CONCLUSIONS

HEPA air cleaners reduce airborne Can f 1 in homes with dogs. Furthermore, preventing the access of the dog to the bedroom and possibly the living room may reduce the total allergen load inhaled.

Washing the dog reduces dog allergen levels, but the dog needs to be washed twice a week

BACKGROUND

Many asthmatic patients allergic to dogs refuse to part with their dog, and it is essential to develop techniques for lowering exposure with a dog in the home.

OBJECTIVE

This study investigated the effect of dog washing on the subsequent recovery of Can f 1 from dog hair clippings and on the airborne allergen over a 7-day period.

METHODS

Dogs, which had not been washed for at least the previous 3 weeks, were washed with a hand-held shower and proprietary shampoo. Hair clippings and dander samples from 25 dogs were collected before and immediately after washing. After these initial studies, 16 dogs had a small tuft of hair clipped from the collar or spinal area before washing and then daily for the next 7 days. Air sampling was performed in 5 homes, and the air samples were collected (airflow rate, 9 L/min) over an 8-hour period per day on 10 consecutive days (3 days of baseline sampling before washing and then 7 consecutive days after washing). Can f 1 level was measured by using 2-site ELISA.

RESULTS

Washing significantly reduced recoverable Can f 1 from clippings (84% reduction: from 73 microg/g to 12 microg/g [geometric mean]; P <.0001) and from dander samples (86% reduction: from 347 microg/g to 50 microg/g [geometric mean]; P <.0001). There was a significant reduction in Can f 1 levels in dog hair over the observed 8-day period (F = 18.4, P <. 0001). By using a multiple comparison test, this observed significance was found to be due to the difference between the baseline levels and those on days 1 and 2 after washing, with no difference in the baseline Can f 1 compared with days 3 to 7. Airborne Can f 1 levels showed a downward trend, which reached statistical significance when the data were grouped into 3 sampling periods as follows: baseline (ie, mean of 3 days before sampling) was compared with days 1 to 4 after washing (41% reduction, 95% CI 13%-60%) and days 5 to 7 after washing (61% reduction, 95% CI 2%-84%; P =.014).

CONCLUSIONS

Washing the dog reduces recoverable allergen from dog hair and dander. The dog needs to be washed at least twice a week to maintain the reduction in recoverable Can f 1 from its hair. Washing the dog achieves a modest reduction in the level of airborne Can f 1 in homes with a dog.

Importance of indoor allergens in the induction of allergy and elicitation of allergic disease

During the last few decades, many countries have experienced an increase in the prevalence and severity of asthma. Over the same period, the population in the developed world has retreated indoors, and homes have become better insulated and more energy efficient, resulting in a warm and humid environment with low ventilation rates, ideally suited to house-dust-mite population growth throughout the year. Increasing exposure and increasing sensitivity to indoor allergens represent a progressively higher risk factor for the development of asthma. The development of sensitivity to indoor allergens and the symptoms and severity of asthma in later childhood are directly related to the exposure to allergens in infancy. It was relatively straightforward to demonstrate a quantitative linear dose-response relationship between exposure to house-dust-mite allergens and subsequent sensitization. However, showing the same for exposure and asthma severity has been more difficult, as the relationship between exposure and asthma symptoms in already sensitized individuals is much more complex than in the case of exposure and sensitization. Nevertheless, sensitized individuals are likely to have more severe asthma if exposed to high allergen levels than if their level of exposure is low. Sensitization to house-dust mites is a major independent risk factor for asthma in all areas where climate is conducive to mite population growth. The relevance of allergens other that mite is not consistent between different areas, and depends on the climate, habits, and socio-economic features of the local community. It would appear that presence of mite allergens in homes "overshadows" other allergens (e.g., cat, dog, or cockroach) as a risk factor for sensitization and subsequent development of allergic disease. It is possible that this is the consequence of the difference in inherent potency between allergen sources, and the question of why mite allergens are so potent in inducing sensitization and atopic disease remains to be answered.

Risk levels for mite allergens. Are they meaningful?

Allergens found in house dust are among the most common environmental antigens to which man is naturally exposed. Standardized methods for measuring allergen exposure are essential for assessing the relationship between exposure, sensitization, and the severity of asthma. Monoclonal antibody-based assays are the most widely used method for assessing allergen exposure. In the effort to define the best "index of exposure" to mite allergens, several factors need to be investigated, including: 1) whether allergen should be measured in reservoir dust or airborne 2) whether the results of reservoir measurement should be expressed as recovered allergen per unit weight or per unit area. As yet, airborne sampling is insufficiently sensitive to produce reliable and repeatable results. Therefore, measurement of house-dust-mite allergen concentration in reservoir dust should be regarded as the best-validated index of exposure. The results should be expressed and reported both per unit weight (concentration) and per unit area. The strongest predictor of chronic symptoms and acute exacerbation of asthma is sensitization to indoor allergens. A simple dose-response relationship between IgE-mediated hypersensitivity and allergen exposure has been established. For example, exposure to more than 2 microg Group 1 mite allergen/g dust should be regarded as a risk factor for the development of IgE antibody and asthma in susceptible children. The quantitative relationship between exposure and symptoms in patients already sensitized is complex due to a number of possible confounding factors (e.g., other allergens, viruses, asthma medication). A simple threshold level for provocation of asthmatic symptoms has not been clearly defined.

Laboratory animal allergy

Approximately one third of laboratory animal workers have occupational allergy to animal danders, and a third of these have symptomatic asthma. Sensitization generally occurs with the first 3 years of employment, and risk factors include atopic background, as well as job description as it relates to the intensity of exposure. A symptomatic worker can reduce allergen exposure with personal protective devices. A laboratory can further reduce exposure with generally available equipment, such as laminar flow caging, and procedures, such as frequent wet washing of vivaria and careful maintenance of ventilation systems. It is advisable to institute periodic medical screening of all laboratory animal workers with questionnaires and allergy skin testing in addition to providing them with training programs to reduce personal exposure.

Immune-reactivity of recombinant isoforms of the major house dust mite allergen Der p 2

BACKGROUND

Recombinant Der p 2, expressed in yeast, lacked reactivity with 5 monoclonal antibodies against natural Der p 2.

OBJECTIVE

The aim of this study was to investigate whether the lack of reactivity with recombinant Der p 2 can be explained by the existence of isoforms.

METHODS

By site-directed mutagenesis three recombinant isoforms of Der p 2 were produced. Reactivity with monoclonal antibodies and human IgE was analysed by means of RAST and RAST-inhibition.

RESULTS

All five monoclonals that lacked reactivity with the originally selected isoform, showed reactivity upon replacement of aspartic acid by asparagine at position 114. The other two substitutions (at position 26 and 47) had no effect. Binding of human IgE (n = 10) was not significantly influenced by the isogenetic variation at position 114.

CONCLUSIONS

Monoclonal antibodies raised against natural Der p 2 can sometimes discriminate between different isoforms, allowing the study of the natural occurrence of isoforms. For application in allergen-measurement assays, non-discriminating monoclonal antibodies should be selected.

The major dog allergens, Can f 1 and Can f 2, are salivary lipocalin proteins: cloning and immunological characterization of the recombinant forms

Canis familiaris allergen 1 (Can f 1) and Canis familiaris allergen 2 (Can f 2) are the two major allergens present in dog dander extracts. We now report the isolation of cDNAs encoding both proteins and present their nucleotide and deduced amino acid sequences. Can f 1, produced by tongue epithelial tissue, has homology with the von Ebner's gland (VEG) protein, a salivary protein not previously thought to have allergenic properties. Can f 2, produced by tongue and parotid gland, has homology with mouse urinary protein (MUP), a known allergen. Both VEG protein and MUP are members of the lipocalin family of small ligand-binding proteins. Recombinant forms of Can f 1 and Can f 2 were produced and tested for immunoglobulin E (IgE) reactivity. Among dog-allergic subjects, 45% had IgE directed exclusively to rCan f 1, and 25% had IgE to both rCan f 1 and rCan f 2. In addition, both recombinant proteins were able to cross-link IgE and elicit histamine release from peripheral blood leucocytes in vitro. These findings confirm that Can f 1 and Can f 2 are major and minor dog allergens, respectively, and demonstrate that recombinant forms of dog allergens retain at least some IgE-binding epitopes.

Environmental allergen analyses

Environmental specimens (dust) from indoor home, school, and work-place environments can be evaluated for the content of aeroallergens produced by dust mite, cat, dog, cockroach, and molds, as a means of determining exposure risk and facilitating avoidance therapy. This article examines the variables that influence the levels of these allergens in indoor environments, methods for sampling, clinical laboratory assays used for testing, and interpretation of aeroallergen results for making decisions about remediation.

Major cat and dog allergens share IgE epitopes

BACKGROUND

Patients allergic to cats and dogs frequently display IgE reactivity against allergens from different animals, suggesting a cross-sensitization to common allergenic determinants. Although albumins have been recognized as relevant cross-reactive allergens, little is known regarding cross-reactive epitopes of the major cat and dog allergens.

OBJECTIVE

In this study, sera from patients allergic to cats and/or dogs were used to investigate the presence of common IgE epitopes among the major cat and dog allergens.

METHODS

The IgE reactivity profile of 109 patients who were allergic to allergens from several species of animals was determined with nitrocellulose-blotted cat and dog allergens. Sera from patients who were strongly allergic to the major cat and dog allergens were tested for the presence of cross-reactive IgE antibodies by one-dimensional and two-dimensional immunoblot inhibition experiments and by quantitative measurements obtained with the CAP-FEIA system (Pharmacia).

RESULTS

Sixty-eight of 109 patients with animal allergy showed IgE reactivity to cat allergens and dog allergens. Sera from patients with both cat and dog allergy detected allergens of similar molecular weight in nitrocellulose-blotted cat and dog hair/dander extracts. Common, as well as species-restricted, IgE epitopes of the major cat and dog allergens could be demonstrated by IgE inhibition studies.

CONCLUSION

Shared IgE epitopes of the major cat and dog allergens may provide an explanation for the clinical observation that allergies to cats and dogs are frequently associated.