Diagnosis of hypersensitivity to dog epithelium in patients with asthma bronchiale

Albumins represent highly cross-reactive animal allergens

Albumins from animals are highly cross-reactive allergens for patients suffering from immunoglobulin E (IgE)-mediated allergy. Approximately 20-30% of cat and dog allergic patients show IgE reactivity and mount IgE-mediated allergic reactions to cat and dog albumin. It is astonishing that allergic patients can develop specific IgE responses against animal albumins because these proteins exhibit a more than 70% sequence identity to human serum albumin (HSA) which is the most abundant protein in the blood of the human body. The sequence identity of cat albumin (Fel d 2) and dog albumin (Can f 3) and HSA are 82% and 80%, respectively. Given the high degree of sequence identity between the latter two allergens and HSA one would expect that immunological tolerance would prohibit IgE sensitization to Fel d 2 and Can f 3. Here we discuss two possibilities for how IgE sensitization to Fel d 2 and Can f 3 may develop. One possibility is the failed development of immune tolerance in albumin-allergic patients whereas the other possibility is highly selective immune tolerance to HSA but not to Fel d 2 and Can f 3. If the first assumption is correct it should be possible to detect HSA-specific T cell responses and HSA-containing immune complexes in sensitized patients. In the latter scenario few differences in the sequences of Fel d 2 and Can f 3 as compared to HSA would be responsible for the development of selective T cell and B cell responses towards Fel d 2 as well as Can f 3. However, the immunological mechanisms of albumin sensitization have not yet been investigated in detail although this will be important for the development of allergen-specific prevention and allergen-specific immunotherapy (AIT) strategies for allergy to albumin.

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.

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.

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.

Evaluation of a capsulated hydrophilic carrier polymer (the ImmunoCAP) for measurement of specific IgE antibodies

The Pharmacia CAP System is a new assay for serum specific IgE, utilising a solid phase capable of binding more antigen than conventional systems. The CAP System has been evaluated in 69 consecutive patients referred to one allergy clinic in relation to skin prick test (SPT), radioallergosorbent test (Phadebas RAST) and specific allergy diagnosis for five inhalant allergens, D.pteronyssinus, timothy grass pollen, cat epithelium/dander, Cladosporium and Alternaria. Good correlation was obtained between RAST and CAP for all allergens, e.g. r = 0.974 for D.pteronyssinus and r = 0.964 for grass pollen. When sensitivity and specificity were examined for both CAP and RAST versus SPT, CAP was usually found to be of greater sensitivity than RAST, and of similar or slightly lower specificity. SPT gave more positive reactions than either in vitro test, but CAP gave more positives than RAST. Twenty-two of 336 (6.6%) tests were CAP positive/RAST negative, whereas a negative CAP with a positive RAST occurred in only 2/336 (0.6%) tests. Of patients with any test (SPT or RAST or CAP) for specific IgE positive, up to 20-30% did not have clinical allergy, confirming the importance of the history in interpreting these tests. Our results suggest that, for the allergens tested, the Pharmacia CAP System is more sensitive than the RAST, identifying more positive tests and approximating more closely to the SPT. It offers the additional advantages of speed and efficiency.

Risk factors for sensitization to furred pets

The risk factors for sensitization to pets was investigated in 169 male pupils. A recent or former contact with cats, dogs, and guinea pigs in own home was reported in 52 (30.8%), 42 (24.9%), and 20 (11.8%) study subjects, respectively. Clinically manifested allergy was found in two probands to cats and in two others to guinea pigs, three of them had formerly had pets and one proband with allergic rhinitis to cats had never had any pet. Sensitization to animals and aeroallergens was investigated with Phadezym-RAST. Only owners of cats had a higher incidence of cat sensitization than probands without direct contact (26.9% versus 10.3%, P less than 0.01). No statistically significant difference in sensitization to dogs and guinea pigs was found in groups with and without these pets. A strong correlation existed between sensitization to pets and other aeroallergens (house dust mite: P less than 0.025, birch pollen: P less than 0.0001, mugwort: P less than 0.0001, and grass pollens: P less than 0.0001). No association was found between sensitization to pets and smoking history, bronchial hyperreactivity to methacholine or radiological findings of the paranasal sinus.

Cross-allergenicity between extracts of hair from different dog breeds and cat fur

Skin tests and RAST determinations with breed-specific dog allergen extracts and a cat allergen preparation were made on forty-four atopic patients divided into three groups. Group 1 were twenty dog-owning atopic patients without clinical signs of dog sensitivity, Group 2 contained twenty-one patients with a clinical history that suggested allergy to dogs, and Group 3 contained ten atopic patients who were sensitive to cats. In neither the in vivo nor the in vitro tests was there any evidence for dog breed specificity, nor was dog albumin found to be a major allergen in the population studied, though a few individuals showed strong RAST activity to albumin. Furthermore, a cat fur extract inhibited the reaction between dog hair and anti-dog serum, and a dog hair extract inhibited the reaction between cat fur extract and anti-cat serum.

Antigenic/allergenic composition of Poodle/Alsatian dandruff extract

Poodle and Alsatian dog dandruff extracts were characterized by crossed immunoelectrophoresis (CIE) and crossed radioimmunoelectrophoresis (CRIE) using sera from 24 individuals clinically sensitive to dogs. By using a system with intermediate gel in immunoelectrophoresis, the content of dander-specific and serum-specific allergens was established. 29 antigens (18 dander-specific and 11 serum-specific) were identified in the mixed breed Poodle/Alsation dandruff extract. Of these, 24 antigens were radiostained in CRIE. 16 allergens were dander specific and the remaining eight were serum specific. Positive dog dander RAST (e5 and Poodle/Alsatian dandruff extract) results were observed in the tested dog hypersensitive subjects. Our results suggest that the mixture of Poodle/Alsatian dandruff extract may be a suitable preparation for the diagnosis and treatment of dog allergy.

Breed-specific dog hypersensitivity in humans

The contribution of allergenic components of dander and serum from individual dog breeds in human hypersensitivity and the different responses to the various breeds in vivo and in vitro were examined. Differences in IgE antibodies directed against 13 individual dog breed danders and five different breed-specific sera were measured in groups sensitive and nonsensitive to dogs by the radioallergosorbent test (RAST). Cross-reactivity between dander extracts and sera was examined by RAST inhibition. Mean RAST binding to dog danders and sera was 15.9% and 14%, respectively, for the dog-sensitive group versus 0.6% for both danders and sera in the nonsensitive group. The mean difference in binding between groups was statistically different for all dander extracts and sera. The variances in binding were statistically greater for danders than sera in six of eight dog-reactive subjects. RAST binding and intradermal skin tests at a 1:10,000 w/v dilution correlated well (p < 0.05) for seven of nine breed-specific extracts. RAST inhibition studies showed that dog serum proteins were relatively poor inhibitors of dander extracts, and vice versa. Variability of skin test and RAST responses to different dog breed dander extracts support the existence of breed-specific allergens.

Skin test reactivity to dog-derived antigens

Skin test reactivity to canine antigens was studied by testing atopic patients and veterinarians using a commercially prepared mixed-dog epithelial antigen and breed-specific antigens including dander extracts, serum and urine, obtained from thirty-one different pure-bred dogs. Increased skin test reactivity was noted using breed-specific antigens as compared to the mixed-dog commercial screening extract. Variation in skin test responsivity related to specific breed antigens was also noted. The results suggest that skin tests using canine urine and serum antigens, in addition to the conventional dander antigens, may be useful in the diagnosis of hypersensitivity to dogs.

Skin prick test in the diagnosis of dog dander allergy: a comparison of different extracts with clinical history, provocation tests and RAST

Skin prick tests (SPT) were carried out on 164 asthmatic children using dog dander allergen preparations (A, B1, B2 and D) from three manufacturers. Bronchial and/or conjunctival provocation tests with allergen A were performed on all patients, as well as the Phadebas RAST (allergen e5). There was a close agreement between the clinical history and the SPT with allergens A and D. The provocation tests and RAST gave results in good agreement with the SPT reactions to all allergens except B1. The overall agreement between the SPT reactions to the different allergens was good. However, significant differences were observed in the allergenic activity of the different preparations and between different batches from the same manufacturer (allergens B1 and B2).

Epithelial or dandruff allergen for the diagnosis of dog allergy by RAST?

When used for screening by the RAST technique, dog epithelium provided too few positive results (29.2%) compared with dog dandruff (58.8%), cat epithelium (53.6%) and horse dandruff (52.2%). However, dog dandruff can provide an unexpectedly high incidence of positive RAST results (45.2%) in sera from patients with an allergic history to cat or horse, but not to dog. Dog dandruff allergens were found to cross-react with some cat or horse serum proteins in about 25% of such patients. We conclude that dog dandruff is preferable to epithelium for screening by the RAST technique, but if emotional issues involving a family pet arise then confirmation by a trial separation is likely to be more convincing than a provocation test with a possibly non-specific allergenic extract.

RAST in the diagnosis of hypersensitivity to dog and cat allergens. A comparison of different extract preparations with clinical history, skin test and provocation tests

A comparison was made of clinical signs and provocation tests with the RAST for allergy to dog in eight and cat in twenty patients. Twenty-two had high IgE levels and all gave positive reactions to provocation tests. A commercially available dog epithelium extract gave more positive RASTs than five other dog allergen preparations, and there were no positive reactions to dog serum. The RAST was negative in patients with a low degree of sensitivity. All twenty patients allergic to cat gave positive intracutaneous test reactions and in the RAST the cat epithelial allergen showed 90% agreement with the in vivo findings.

[Allergy diagnosis in patients with bronchial asthma (bronchial provocation test, skin test and RAST) (author's transl)]

87 patients with bronchial asthma underwent skin test, RAST and measurment of airway resistance before and after inhalation of control solution as well as at least 10 times after each of one to four bronchial provocations (making up a total of 171 tests) with extracts of house dust, house dust mite, animal dander, mould spores and pollen in increasing concentrations. An actual clinical significance of the skin test reactions was found in 60% of all cases and of the RAST results in 66% of all cases. The overall agreement between skin test results and RAST results was 61%. The correlations between the different tests depended on the degree of hypersensitivity, on the tested allergen and on whether the results of skin test and RAST, respectively, were positive or negative. There existed a good correlation between the results of all three test methods and case history only for pollen allergens and animal dander. Noticeably often negative RAST results with house dust and mould spores, as well as positive skin tests with house dust mite and mould spores could not be confirmed by the provocation test. Important indications for a bronchial provocation test in asthmatics are doubtful case history, doubtful skin test or RAST results with the problem-allergens house dust, house dust mite and mould spores; the bronchial provocation test is especially commendable when drastic or cumbersome therapeutic measures (immunotherapy, change of home, change of job) are to follow or if late asthmatic reactions are expected.

Reappraisal of intracutaneous tests in the diagnosis of reaginic allergy

In an attempt to determine the clinical relevance of positive intracutaneous tests when epicutaneous tests are negative, 34 patients with symptoms of perennial rhinitis who had negative epicutaneous but positive intracutaneous tests were evaluated by radioallergosorbent (RAST) test, nasal provocation (NP) tests and leukocyte histamine release (LHR) assay. Nineteen patients with perennial rhinitis who had positive epicutaneous tests and 13 normal healthy volunteers were also studied as positive and negative controls, respectively. None of the 34 patients with negative epicutaneous but positive intracutaneous tests had positive RASTs or LHR assays, but 1 patient had a positive NP test. In contrast, of the 19 patients with positive epicutaneous tests, 12 patients had positive RASTs, 17 had positive LHR assays, and 17 had positive NP tests. In the negative control group of 13 subjects, none had positive RAST, LHR assays, or NP tests, although 3 subjects showed positive intracutaneous tests. These results indicate that when epicutaneous tests are negative in patients with perennial rhinitis, positive intracutaneous tests are not likely to indicate the presence of reaginic allergy.

Characterization of extract of dog hair and dandruff from six different dog breeds by quantitative immunoelectrophoresis. Identification of allergens by crossed radioimmunoelectrophoresis (CRIE)

An extract of mixed dog hair and dandruff from six different dog breeds (alsatian, boxer, collie, poodle, and long-haired and short-haired dachshund) was obtained by mild extraction, centrifugation, dialysis and freeze-drying. Extract of hair and dandruff from the individual dog breeds was obtained in the same way, but the material was not freeze-dried. Examination and characterization of the mixed extract by means of crossed immunoelectrophoresis revealed a precipitation pattern composed of 25 antigens, some of which were mutually partially identical, and a high content of dog serum proteins was found. Quantitative and qualitative differences between the individual dog breeds were demonstrated. Partial identity of the antigens of the mixed extract with antigens of serum, antigens of extracts of hair and dandruff from cat, cow, horse and guinea pig, and antigens from extract of house dust was also observed. By means of crossed radioimmunoelectrophoresis, using sera from 21 patients who were RAST-positive to dog hair and dandruff extract, the specific IgE-binding to antigens of the mixed extract was examined. On the basis of these results major and minor allergens were identified. Dog albumin was found to be a very important major allergen, but alpha1-antitrypsin and gamma-globulin were also identified. Furthermore, four non-serum proteins were shown to be allergens. No breed-specific allergens could be identified in the extracts from the individual dog breeds.

Animal dander allergy

In a group of twenty-three atopic patients skin tests were performed with the dander allergens of horse, cat and guinea-pig, and with house dust and Timothy pollen allergens. A good agreement was observed between positive skin reactions and the results of RAST with these various allergens. In a number of cases, positive skin reactions were not related to the clinical histories. Likewise, positive RAST scores in several instances proved clinically meaningless. In patients with history-related skin reactions better correlation with RAST was observed. In such patients, skin reactions with photo-inactivated allergens remained strongly positive.

Specific IgE antibodies in nasal secretion from patients with allergic rhinitis and with negative or weakly positive RAST on the serum

Nasal secretions from eighteen patients with allergic rhinitis with a positive case history, intradermal test and nasal provocation test, but with negative or only weakly positive RAST (radioallergosorbent test) on the serum against a total of thirty-five allergens, were studied. In the RAST an immunosorbent-purified anti-IgE with DE2 specificity was used, which raised the detection limit. Nasal secretion was collected by washing the nasal mucosa with 0-9% and 18% NaCl solution respectively, and the latter secretion was also luophilized and concentrated. In ten cases RAST was slightly positive on the nasal secretion, and in three of the concentrated secretions the RAST value was higher than on the serum. In none of the serum or nasal secretion samples was RAST positive according to the cut off value for a positive result defined by the reference system used in Phadebas Rast. From these results it is concluded that RAST analyses of nasal secretion from patients with allergic rhinitis is of no appreciable value in routine clinical allergological diagnosis. However, the increased sensitivity of RAST obtained with isotope-labelled anti-DE2 may be useful in the serological diagnosis of patients with low grade allergy having low levels of IgE antibodies in serum.

The cross-reactivity of IgE antibodies with pollen allergens. I. Analyses of various species of grass pollens

Atopic patients with histories of grass pollen allergy often are sensitive to a variety of species of grasses. Using a serum pool from patients sensitive to June grass, we analyzed the reactivity of IgE antibodies to seven grasses by the radioallergosorbent test. Extracts were analyzed for their inhibitory activities with solid-phase allergens prepared from all of the grass pollen. Also samples of serum were exhaustively absorved with solid-phase allergens and the supernatants tested to determine the reactivity of the remaining IgE antibodies. Three patterns of reactivity were observed: (1) June, orchard, meadow fescue, and perennial rye grasses displayed similar reactivity in both inhibition and absorption studies; (2) sweet vernal and Bermuda grasses were considerably less reactive with the serum pool, indicating that they lacked antigenic determinants possessed by the other grasses; and (3) timothy grass possessed unique antigenic determinants. Knowledge of these patterns of cross-allergenicity is of importance for diagnosis and treatment of sensitive patients as well as for in vitro standardization of extracts.

Studies on Alternaria allergens. I. Establishment of the radioallergosorbent test for measurement of Alternaria allergens

The ability to covalently couple Alternaria allergens to microcrystalline cellulose particles has permitted not only the measurement of IgE antibodies to Alternaria in patient serums but also the identification of allergenic fractions from crude Alternaria extracts. Crude aqueous Alternaria extracts from 3 commerical suppliers were coupled to cellulose but failed to bind more than 5% of total radioactive counts (TRC) when reacted with serums from highly sensitive patients. Fractionation of a commercial extract through Sephadex G-25 showed that almost all allergenic activity was located in a protein- and carbohydrate-containing peak eluting at the column void volume. These fractions were pooled and coupled to cellulose to yield a RAST polymer which produced up to 20% TRC binding when tested with serums from over 100 Alternaria-sensitive patients, and only up to 1% TRC binding with 17 nonallergic serums. The study of commercial Alternaria extracts by chromatographic and Rast inhibition techniques showed that present extracts are neither qualitatively or quantitatively comparable.

Pet sensitivities in asthmatic children

A history of pet contact and/or apparent clinical sensitivity was obtained in 65 (55%) of 118 unselected asthmatic children. These 65 children were skin tested and their sera examined for specific IgE using the radioallergosorbent test. Those children who had apparent clinical sensitivities had larger skin test reactions and were more likely to have positive specific IgE results than those without apparent sensitivities. Positive skin tests were very common (80%), but the larger the skin test reaction (weal diameter greater than 4 mm diameter) the more likely was there to be a positive history or a positive specific IgE result. Hence a large skin test reaction can provide a helpful pointer to animal allergy of clinical importance. Commercially available animal extracts have limitations for diagnostic tests. A questionnaire survey of 150 day schools emphasized the potential opportunities for contact with animal allergens at school.

Measurement of specific IgE antibodies in nasal secretion--evidence for local production

Serum levels of total and specific immunoglobulin E (IgE) have been determined by radioimmunoassays in sixty-nine allergic subjects. The forty-one subjects with mild symptoms were the most difficult to diagnose, since nine had IgE levels less than 50 U/ml and nineteen had no detectable specific IgE antibodies. Samples of nasal secretions were collected from these nineteen subjects and five were found to have specific IgE antibodies, and in a further eight increased amounts of total IgE. The possibility of locally produced IgE antibodies should therefore be considered when using in vitro tests to diagnose mild or recently acquired allergies, especially when serum IgE levels are less than 50 U/ml.

In vitro diagnosis of atopic allergy. The occurrence and clustering of positive RAST results as a function of age and total IgE concentration

Specific IgE antibodies were determined on a routine basis in patient sera using the radioallergosorbent test (RAST) with a panel of ten common allergens. Total IgE was also assayed. Of all positive RAST reactions observed, 74% were against the following allergens: horse and cat epithelium, birch and timothy pollen, and house dust. Clustering (occurrence together with significantly elevated frequencies) accompanied both positive reactions to some animal danders and food allergens. Children in all age groups had significantly more positive food RAST results than adults, and this explains the clustering among food allergen results. Children aged 0-4 years had few positive pollen results. Among those with at least one positive RAST result, the mean number of positive results was 3.3, a figure which did not vary with age. In the present patient population 37% had a total IgE above the upper reference (normal) limit, and of these 95% had at least one positive RAST result. A normal or low IgE value was found to be less informative.

Measurement of IgE antibodies by the radioallergosorbent test. I. Technical considerations in the performance of the test

Since its introduction by Wide, Bennich, and Johansson in 1967, the radioallergosorbent test (RAST) has been increasingly used for measurement of specific IgE antibodies. In this study we have varied the conditions during the performance of the RAST and have investigated the effect of altering: (1) the speed of rotation of tubes, (2) the number of washes in both steps of the test, (3) the length of rotation of tubes, (4) the temperature, (5) the conditions during centrifugation, (6) the quantity of antibody to IgE in the second step of the test, (7) the composition of buffers in the reactions, (8) the type of tube employed in the test, (9) the quantity of antigen employed during the coupling procedure, and, finally, (10) the iodine isotope, 125I or 131I, used to radiolabel anti-IgE. Of these variables the most significant were the quantity of anti-IgE used in the second step of the test and the quantity of antigen used in the coupling procedure. Other variables of importance were the choice of radioiodine, whether the tubes were rotated or not, the type of tube used, and finally the diluent employed.