The collaborative study of the international standard of dog, Canis domesticus, hair/dander extract

Effects of mechanical washing and drying on the removal of pet allergens

Background: In Korea, the number of households with indoor pets is rapidly increasing in parallel with changes in cultural lifestyles. The sensitization rate of pet allergens is also increasing in Korea. Objective: We evaluated the effectiveness of washing machines to remove dog and cat hair and their allergens. In addition, this study aimed to investigate whether only a mechanical dryer without mechanical washing could be used for pet allergen removal. Method: We brushed cats and dogs, and thereafter collected their hair and used a residential vacuum cleaner to obtain dust and other particulate matter from a household. The contents of the vacuum bag were sifted through a 300-μm sieve filter. Some of the contents were placed in phosphate-buffered saline solution with 0.5% Tween 20 to make a liquid extract. Hair, dust, and liquid extract-contaminated fabric samples after mechanical washing or after drying without mechanical washing were analyzed for pet allergens (Fel d l [cat], Can f 1 [dog]) by using a two-site enzyme-linked immunosorbent assay. We assessed the remaining allergens in the contaminated fabrics after mechanical drying and washing. Results: The mean Fel d l and mean Can f 1 removal ratios after mechanical washing with detergent were > 99.99% for the dust, hair, and liquid extract. The removal ratios after mechanical washing without a detergent were lower for both Fel d 1 and Can f 1, for hair, dust, and their respective liquid extracts (p < 0.05). Mechanical drying was just as effective as mechanical washing with detergent for removing Can f 1 but was less effective for Fel d 1 (p < 0.05). Conclusion: Mechanical washing with detergent is important to remove pet allergens from contaminated fabrics. If washing is difficult, then using just a dryer without washing can be an alternative method to remove allergens from contaminated bedding or clothing.

The History, Present and Future of Allergen Standardization in the United States and Europe

The topic of standardization in relation to allergen products has been discussed by allergists, regulators, and manufacturers for a long time. In contrast to synthetic medicinal products, the natural origin of allergen products makes the necessary comparability difficult to achieve. This holds true for both aspects of standardization: Batch-to-batch consistency (or product-specific standardization) and comparability among products from different manufacturers (or cross-product comparability). In this review, we focus on how the United States and the European Union have tackled the topic of allergen product standardization in the past, covering the early joint standardization efforts in the 1970s and 1980s as well as the different paths taken by the two players thereafter until today. So far, these two paths have been based on rather classical immunological methods, including the corresponding benefits like simple feasability. New technologies such as mass spectrometry present an opportunity to redefine the field of allergen standardization in the future.

Standardization of Allergen Extracts

Allergens are molecules with the capacity to elicit IgE responses in humans. When stimulated with allergens, most allergic patients respond with production of IgE specific for several proteins/allergens in the source material. The standardization of allergen extracts is essential in order to control variability and to achieve consistency and reproducibility in a clinical setting.Because the IgE binding capacity of an allergen extract is related to the content of one or a few major allergens, it is important that the standardization procedure ensures consistency, not only in the overall IgE binding potency, but also in the content and ratio of individual major allergens. Owing to the complexity of allergen extracts, a key element in standardization of allergen extracts is the use of standards.This chapter describes the principles for standardization of allergen extracts to be used by research laboratories. Other chapters in this volume describe in vitro methods in detail.

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.

European Academy of Allergy and Clinical Immunology task force report on 'dose-response relationship in allergen-specific immunotherapy'

BACKGROUND

For a century, allergen-specific immunotherapy (SIT) has proven to be an effective treatment for allergic rhinitis, asthma, and insect sting allergy. However, as allergen doses are frequently adapted to the individual patient, there are few data on dose-response relationship in SIT. Allergen products for SIT are being increasingly required to conform to regulatory requirements for human medicines, which include the need to demonstrate dose-dependent effects.

METHODS

This report, produced by a Task Force of the EAACI Immunotherapy Interest Group, evaluates the currently available data on dose-response relationships in SIT and aims to provide recommendations for the design of future studies.

RESULTS

Fifteen dose-ranging studies fulfilled the inclusion criteria and twelve reported a dose-response relationship for clinical efficacy. Several studies also reported a dose-response relationship for immunological and safety endpoints. Due to the use of different reference materials and methodologies for the determination of allergen content, variations in study design, and choice of endpoints, no comparisons could be made between studies and, as a consequence, no general dosing recommendations can be made.

CONCLUSION

Despite recently introduced guidelines on the standardization of allergen preparations and study design, the Task Force identified a need for universally accepted standards for the measurement of allergen content in SIT preparations, dosing protocols, and selection of clinical endpoints to enable dose-response effects to be compared across studies.

The CREATE project: development of certified reference materials for allergenic products and validation of methods for their quantification

Allergen extracts have been used for diagnosis and treatment of allergy for around 100 years. During the second half of 20th century, the notion increasingly gained foothold that accurate standardization of such extracts is of great importance for improvement of their quality. As a consequence, manufacturers have implemented extensive protocols for standardization and quality control. These protocols have overall IgE-binding potencies as their focus. Unfortunately, each company is using their own in-house reference materials and their own unique units to express potencies. This does not facilitate comparison of different products. During the last decades, most major allergens of relevant allergen sources have been identified and it has been established that effective immunotherapy requires certain minimum quantities of these allergens to be present in the administered maintenance dose. Therefore, the idea developed to introduce major allergens measurements into standardization protocols. Such protocols based on mass units of major allergen, quantify the active ingredients of the treatment and will at the same time allow comparison of competitor products. In 2001, an EU funded project, the CREATE project, was started to support introduction of major allergen based standardization. The aim of the project was to evaluate the use of recombinant allergens as reference materials and of ELISA assays for major allergen measurements. This paper gives an overview of the achievements of the CREATE project.

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.

Standardization of allergen-specific immunotherapy vaccines

In the 1970s and 1980s, scientific methods were introduced in the standardization of allergen vaccines and, in combination with improved documentation of the clinical benefits obtained using standardized vaccines, specific allergy treatment as a scientifically based, reproducible, and safe treatment for allergic disease was established. This article describes important issues in the control of source materials and vaccine preparation as part of the European standardization of allergen vaccines, and also includes a discussion of vaccines that are based on recombinant allergens, which may appear on the market in the near future.

Laboratory animal allergy: an update

Allergic reactions are among the most common conditions affecting the health of workers involved in the care and use of research animals. Between 11 and 44% of the individuals working with laboratory animals report work-related allergic symptoms. Of those who become symptomatic, 4 to 22% may eventually develop occupational asthma that can persist even after exposure ceases. Allergic symptoms consist of rashes where animals are in contact with the skin, nasal congestion and sneezing, itchy eyes, and asthma (cough, wheezing, and chest tightness). The generation of immunoglobulin E (IgE) antibodies is a prerequisite for the production of allergic symptoms. The mechanism by which IgE antibodies develop is becoming clearer. The propensity to produce IgE is genetically determined, and pre-existing allergy may be a risk factor for the development of laboratory animal allergy (LAA). However, exposure to animal allergens is the major risk factor for the development of LAA. Techniques to measure the airborne concentration of laboratory animal allergens have been developed. Research on animal allergens themselves indicates that many of the mouse and rat urinary proteins belong to a family of proteins called lipocalins, which share sequence homology with antigens of the parasitic agent that causes schistosomiasis. The fact that parasite infections also trigger IgE antibody responses may account for the development of LAA in persons who have never had any previous allergy. The prevention of LAA should be a major goal of an effective health and safety program in the animal research facility, and it can be accomplished by education and training of employees, reduction of exposure (including the use of personal protective gear), and changes in facility design. Medical surveillance programs can also play a role in improving health of individuals working with laboratory research animals. Early recognition of symptoms and evidence of sensitization can lead to interventions to reduce exposure and thereby avoid the long-term health consequences of LAA.

Recombinant allergens/allergen standardization

Recombinant allergens are genetically engineered isoforms representing allergen molecules from allergen extracts. Immunologic responses of allergic patients toward allergen extracts define the major allergens. For the average allergic patient, the diagnostic sensitivity and treatment efficacy correlate with the concentration of major allergen. Standardization of allergen products (extracts or genetically engineered allergens) can therefore advantageously be performed using a selected recombinant major allergen as a standard. The standardization will furthermore require reagents for which both monospecific, monoclonal, or preferably, recombinant antibodies can be used. Due to differences in the allergenic activity of individual isoallergens and the naturally occurring mixture of isoallergens found in an allergen extract, and due to additional contribution to the allergenic activity from other molecules in the extract, a biologic potency assessment must always be performed as a supplement. This is also the case for a genetically engineered allergen product.

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.

Laboratory animal allergens

Allergic sensitivity to laboratory animals can pose a significant occupational hazard to anyone with regular animal contact. Reactions to mice and rats are most common although all furred animals produce allergens that can lead to sensitization and disease. Most of the relevant allergens of laboratory animals have been defined and characterized, which has revealed that these allergens are typically small, acidic glycoproteins and that many of them are members of a superfamily of extracellular proteins called lipocalins. In addition to understanding their molecular characteristics, the identification of these allergens has also made it possible to measure their distribution in laboratory environments and to relate exposure levels to sensitization and symptoms. These studies have shown that the major laboratory animal allergens are carried on small particles that are both capable of remaining airborne for extended periods and penetrating into the lower airways of exposed workers. These advances in the understanding of these important occupational allergens will allow for the development of better methods of diagnosis and avoidance for affected workers and others who may be at risk for future difficulties.

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.

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.

Role of animal danders as inhalant allergens in bronchial asthma in India

The etiological significance of animal danders in Indian patients with nasobronchial disorders has not yet been investigated. In the present study, the role of animal danders in the etiology of bronchial asthma was studied. Extracts of danders from 6 animals along with guinea pig whole pelt were prepared. Intradermal and bronchial provocation tests with these extracts were performed on (i) 68 asthmatics and (ii) 20 nonallergic healthy volunteers. In patients, significant positive skin reactions (2+ to 4+) ranged from 1.4% each with guinea pig whole pelt and ox dander to 8.8% with dog dander extracts. None of the healthy volunteers elicited such a response. On bronchial provocation, 20% and 53.8% of the tests were positive in asthmatics showing 1+ and 2+ skin reactivity, respectively. All the patients as well as controls eliciting negative intradermal responses demonstrated uniformly negative bronchial provocation tests to different dander extracts. Analysis of various clinical features of asthmatics with respect to skin positivity to dander/pelt extract was also carried out. Radioallergosorbent tests (RASTs) were performed to estimate dander-specific IgE levels in the sera of patients showing different grades of skin response to dander extracts of dog, horse, and goat. Sixty percent of sera from the patients showing 2+ to 4+ skin reactivity to various animal dander extracts showed positive RASTs. RAST positivity as well as RAST ratio increased with increase in the intensity of skin response. All the patients with positive cutaneous as well as positive bronchial responses also showed positive RASTs. Similarly, all the patients with positive skin and positive RASTs showed positive bronchoprovocation tests. These results suggested that animal danders play an important role in the etiology of bronchial asthma. Some of the clinical characteristics of asthmatics, such as (i) early age at onset of asthma, (ii) positive family history, and (iii) asthma with associated allergies, have significant bearing on the cutaneous response to various dander extracts.

Dander is the best epithelial source for dog allergenic extract preparations

Four different commercially available raw materials of dog epithelia (dander, hair and skin scraping, skin scraping, and whole skin) were compared by means of biochemical methods such as SDS-PAGE and chromatography with the SMART System, immunochemical methods such as RAST and SDS-PAGE immunoblotting, and cutaneous tests. Dander extract clearly exhibited the highest IgE binding and in vivo allergenic activity. The dog major allergens Can fI and the 19-kDa protein were adequately detected only in dander extract. Thus, it is concluded that dander is the most suitable epithelial source for preparing dog allergenic extracts.

Detection and characterization of atopic allergens

The aim of the research of atopic allergens is to gather knowledge in order to be able to identify and to characterize environmental allergens and to develop better allergen preparations for diagnosis and treatment of IgE-mediated hypersensitivity diseases. Allergens or allergen activity can be detected and characterized with several in vivo and in vitro methods. In vivo tests measure the biological allergen activity, which is the most important characteristic of allergen preparations. Chemical and some immunochemical methods do not directly measure allergen activity, unless human IgE antibodies have been utilized. Since all these methods have their advantages and disadvantages, more than one method would be favourable in characterization of an allergen or an allergen preparation.

Molecular characterization of dog albumin as a cross-reactive allergen

Indoor allergens comprise a group of allergenic proteins that are commonly derived from house dust mite and cat and dog dander. In addition to the two major dog allergens (molecular weights: 19 and 23 kd), dog albumin represents an important allergen for up to 35% of patients who are allergic to dogs. In IgE immunoblot inhibition studies and histamine release tests it has been demonstrated that patients who react to dog albumin exhibit IgE reactivity with purified albumins from cat, mouse, chicken, and rat. The proportion of dog-specific IgE directed against dog albumin was determined for patients allergic to dog albumin, and it ranges from 70% to 90%. By IgE immunoscreening of a lambda gt11 expression library from a dog salivary gland, we identified a number of reactive complementary DNA clones. All patients with IgE reactivity against natural dog albumin displayed IgE reactivity to the beta-galactosidase fusion protein encoded by clone 54c, which was therefore assumed to contain major IgE epitopes of dog albumin. The deduced amino acid sequence of clone 54c was compared with the Swiss-Prot library, and significant sequence homologies were found with albumins from different species (human: 82.6%, pig: 81.8%, cattle: 77.3%, sheep: 78.8%, mouse: 75.8%, and rat: 76.2%). Several other IgE-positive clones hybridized with oligonucleotides that were prepared according to this sequence. Partial complementary DNA coding for dog albumin fragments may be considered a useful tool for further characterization of major IgE epitopes of dog albumin.

Standardization of pollen allergens of Parthenium hysterophorus and selection of an in-house reference extract

A standardized in-house reference extract from the pollen of Parthenium hysterophorus, which is responsible for the high incidence of allergic rhinitis in India, was generated and examined by skin test, radio-allergosorbent test inhibition and isoelectric focusing. Parthenium reference allergen discs and positive reference serum were also generated. These reference reagents could not only be used for the quantitation of Parthenium-specific IgE in the sera of rhinitis patients but also for the evaluation of allergenic activity (relative potency and lot-to-lot variation) of different batches of Parthenium pollen.

The allergens of dog. II. Identification and partial purification of a major dander allergen

A dog hair and dander (DHD) extract was prepared from hair obtained from mixed breeds. By SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting, using sera from 32 dog-allergic subjects, a number of IgE radio-staining bands could be seen. In 78% of sera a protein of molecular weight (MW) of 21,000 daltons, designated Ag X, was found to bind IgE and in 34% it did so strongly. This allergen was isolated from DHD by size-exclusion and ion exchange chromatography. The final product was a single allergen of MW of 21,000 and an isoelectric point of approximately 5.2. An additional protein-staining band could still be seen of MW of 24,000 daltons. Using a serum which contained IgE antibodies only to Ag X, this allergen was found only in DHD extract and dog saliva and was absent from dog serum and urine. It was the same dog allergen that we [1] reported as Ag 8 using crossed radio-immunoelectrophoresis (CRIE) and that Blands et al. [2] and Løwenstein [3] described as Ag 13. We propose that this major dog allergen be given the title Can f I according to the new allergen nomenclature.

Assay for the major dog allergen, Can f I: investigation of house dust samples and commercial dog extracts

Monospecific rabbit antibodies were used to develop a sensitive two-site enzyme immunoassay to measure a major dog hair and dander allergen, Can f I. This Can f I assay demonstrated no reaction with 17 heterologous allergen sources, including dog albumin, cat, guinea pig, and horse. Analysis of serial dilutions of purified Can f I and the international standard for dog was parallel. The assay was considered specific for Can f I with a lower limit of detection at 0.03 micrograms/ml. Total imprecision was from 2% to 6%. Commercial dog extracts for specific immunotherapy contained from 0.7 to 290 micrograms of Can f I per milliliter. The assay was used to measure Can f I in 136 house dust samples collected from 103 homes across the United States. Concentration of the dog allergen was expressed as micrograms of Can f I per gram of dust. Prevalence of Can f I in the dust samples ranged from less than 0.3 to 10,000 micrograms/gm. Serial dilutions of samples containing Can f I were parallel to the standard. The median Can f I value for homes with a dog in residence was 120 micrograms/gm, and for homes with no dog, 3 micrograms/gm. With few exceptions, homes with no dog in residence had less than 10 micrograms/gm. This Can f I assay will provide useful information for assessing commercial extracts as well as monitoring dog-allergen exposure and allergen-control methods.

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

Most dog-allergic patients react to a major 25 kd component on sodium dodecyl sulfate blots, Can f I (Ag 13). We initially raised monoclonal antibodies (Cf-3 and Cf-2) reactive with IgE-binding components distinct from Can f I. After a slight modification, we immunized other strains of mice and produced monoclonal antibodies coded Cf-1a and Cf-1b reactive with Can f 1. We affinity purified the allergens, Can f I and "dog allergen 2" with Cf-1a and Cf-2 ascites, respectively, and house dust-rich dog dander. Comparison of purified Can f I with dog saliva in RAST demonstrated that Can f I is a potent allergen for most dog-allergic patients (average response, 70%). After depletion of dog saliva of Can f I, a slightly lower contribution for Can f I was found, but the overall results supported the conclusion that Can f I is a major allergen in dog saliva. Comparison of purified dog allergen 2 with dog dander in RAST demonstrated that dog allergen 2 is less important for dog-allergic patients (average response, 23%). We radiolabeled the purified allergens and developed assays to measure Can f I and dog allergen 2 in allergen extracts and dust samples. Dog saliva was a strong allergen source, dog urine and feces contained very little of the allergens, and both allergens were found to a variable degree in the nine dog breeds tested.

Purification and characterization of the major dog allergen, Can f I

An important dog-hair and dander-specific allergen Ag13 has been purified by means of immunoaffinity chromatography utilizing rabbit antibody specific for Ag13. Purity was judged to be very high as detected by crossed immunoelectrophoresis and SDS-PAGE. The purified allergen was subjected to amino acid analyses. Molecular weight was about 22 kD in HPLC-gel filtration and 25 kD in SDS-PAGE with an additional band at 18 kD. In vitro IgE binding of the allergen was investigated by luminescence immunoassay (LIA) inhibition. Removal of Ag13 from dog hair and dander extract (DHD) removed 50 +/- 1.5% of the IgE binding capacity. The purified allergen inhibited up to 56.5% of the IgE activity to DHD as measured with a pool of serum from dog-allergic patients. Out of 26 dog-allergic patients, 24 had a positive skin-prick test to the allergen. Out of 23 dog-allergic patients, 16 reacted with the allergen in IgE immunoblotting. We suggest that Ag13 be termed Can f I. The allergen will be a marker allergen for environmental dog hair and dander exposure.

The allergens of dog. I. Identification using crossed radio-immunoelectrophoresis

The antigens present in an extract of dog hair and dander were examined by crossed immunoelectrophoresis (CIE) and the IgE-binding allergens by crossed radio-immunoelectrophoresis (CRIE), respectively, using sera from 60 British and Finnish animal-allergic subjects. The extract was comprised of a minimum of 28 antigens, 11 of which were common to dog serum. IgE antibody in the sera of the dog-sensitive patients bound to 21 of the 28 antigens at varying frequencies and intensities. Binding of any intensity occurred most frequently to two serum proteins: antigen 23 (IgG) binding IgE in 88% of cases, and antigen 3 (dog serum albumin, DSA) in 77% of cases. Dander antigen 8 bound in 63% and antigen 1 in 42% of the sera. Strong IgE binding, however, was most commonly associated with dander antigen 8 followed by antigens 1 and 23 (IgG) then 3 (DSA). The ranking of the antigens as allergens was similar for the two populations except that DSA was more important for the British than for the Finnish subjects.