Allergy to rabbits. I. Specificity and non-specificity of RAST and crossed-radioimmunoelectrophoresis due to the presence of light chains in rabbit allergenic extracts

Angora wool asthma in textile industry

Up to now the exposures to hair and skin derivatives of animals have not yet been the subject of systematic studies. The observation of a clinical case has provided the opportunity for a review of the literature. The inpatient was a 49-year-old man, a carder in a textile factory, exposed to angora wool. He noticed the appearance of dyspnea during working hours. There was no eosinophilia in blood, and the results of pulmonary function tests were normal. The nonspecific bronchial provocation test with methacholine demonstrated an abnormal bronchial reactivity. The challenge test with angora wool was positive (decrease in FEV1 of more than 40%) as well as total IGE and specific IgE to rabbit epithelium (433 KU/l and 12.1 KUA/l, resp.). Several sources of allergens were found in the rabbit, and the main allergen was represented by proteins from epithelia, urine, and saliva. Most of these proteins belong to the family of lipocalin, they function as carriers for small hydrophobic molecules (vitamins and pheromones). If the diagnosis of occupational asthma caused by animal hair and skin derivatives may be relatively easy by means of the challenge test, defining etiology is complicated because of the lack of in vitro tests.

Identification of some rabbit allergens as lipocalins

Rabbits are frequently used as laboratory animals or kept as domestic pets. Rabbit serum albumin and a 17-kDa protein referred to as Ory c 1 have previously been reported as allergens. Several other allergenic proteins have been recognized by crossed immuno-electrophoresis but have not been characterized. The aim of this study was to characterize the allergenic proteins present in rabbit saliva, urine and fur on the basis of molecular size and, where possible, to determine their amino acid sequences. Extracts from the male New Zealand white rabbit were used for developing specific direct RAST and RAST inhibition assays. Proteins in the extracts were separated by SDS-PAGE and the individual allergens identified by immunoblotting with serum from rabbit-allergic individuals. The N-termini of four allergens were sequenced. Saliva was the most potent extract. In total, 26 protein bands were recognized as allergens in the three extracts: 12 in saliva, seven in urine and seven in fur. Their molecular weights ranged from an 8-kDa species in saliva to an 80-kDa protein in urine. The N terminal sequences of an 18 kDa and a 21-kDa species in saliva, were identified as lipocalins with sequence similarity to a recently described odourant binding protein. This is the first evidence that allergens from the rabbit are members of the lipocalin superfamily of proteins, suggesting that similar mechanisms may be involved in eliciting the allergic response to rabbits. The 18 kDa allergen from saliva may be the previously named rabbit allergen, Ory c 1.

Laboratory animal allergy: anaphylaxis from a needle injury

A 32 year old male research physician accidentally received a minor wound from a needle which had been previously used on rabbit tissue. Within 15 minutes serious anaphylactic reactions started and he was taken to hospital where his condition stabilised within five hours. Serum immunoglobulin E antibodies to rabbit epithelium were high (16.2 U/ml), although other antibody titres were low. Allergy tests were not carried out before employment, so this alarming scenario could not have been predicted. People with confirmed laboratory animal allergy should be warned of the dangers of continued unprotected exposure and avoidance of the allergen should be encouraged by good laboratory practice and respiratory protective equipment.

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.

Measurement of airborne rat urinary allergen in an epidemiological study

The suitability of radioallergosorbent test (RAST) inhibition to quantify occupational exposure to rat urinary aeroallergen (RUA) has been assessed. When using a constant pool of rat allergic sera, the reproducibility of the assay over 1 year was comparable to that reported for other immunoassays; at 50% RAST inhibition the inter-assay coefficient of variation (CV) was 7.0% and the intra-assay CV was 3.0%. The assay was highly specific for rat urine; mouse urine was 1100-fold less potent at inhibiting the rat urine RAST system. Significant inter-assay variation in the 'high' control was not due to batch variation and was relatively small when compared with the variation in RUA concentrations in the occupational environment. Measurement of workplace RUA exposure demonstrated that those directly involved in the care of rats experienced the highest RUA exposure of the nine occupational groups studied (animal technicians GM = 23.10 micrograms/m3), dead animals (e.g. post mortem GM = 1.60 micrograms/m3, scientists GM = 0.67 microgram/m3) and rat tissue (e.g. slide production GM = 0.04 microgram/m3). In view of the complexity of rat allergens, RAST inhibition is an appropriate method for the quantification of occupational exposure to rats.

Allergy to rabbits. III. Further identification and characterisation of rabbit allergens

Crossed immunoelectrophoresis and crossed radio-immunoelectrophoresis techniques have been employed for analysis of extracts of various rabbit source materials to identify rabbit allergens in addition to the already described Antigen R1 (AgR1). Urine and dander extracts were found to contain only low levels of AgR1 and its presence in urine was as a contaminant due to mode of collection--it was not present in urine collected directly from the bladder. Other allergens were only recognised by highly rabbit-sensitive individuals, one in particular (Ag2) being present in several source materials. Serum albumin proved to be of minor allergenic importance and except for dander its presence was only in minimal amounts. As both AgR1 and Ag2 are significant components in extracts of fur and dust these extracts are therefore most recommended for use in investigations of individuals sensitive to rabbits.

Allergy to rabbits. II. Identification and characterization of a major rabbit allergen

Quantitative immunoelectrophoretic techniques have been used to study the antigenic components found in extracts of dust collected from rabbit housing areas. To determine the possible source of these antigens, comparisons have been made to rabbit saliva, urine, fur and dander. Specific antisera for the rabbit extracts were raised in guinea pigs. One major component of the dust (Ag Rl) was also found in large amounts in saliva, slightly less in fur and in only minimal amounts in urine and dander. Crossed radioimmunoelectrophoresis (XRIE) of the dust, performed with sera from 14 rabbit allergic individuals who were RAST positive to rabbit saliva, urine and dust identified four IgE-binding constituents. Individual responses varied but all sera reacted with Ag Rl, identifying this as a major rabbit allergen. Dust RAST inhibition studies with rabbit dust, saliva and urine indicated saliva to be closely related to the dust. Ag Rl is a glycoprotein which appears to be very heterogeneous in nature. It produced a broad biphasic precipitin peak on immunoelectrophoresis and eluted from Sephacryl S-200 gel filtration over the molecular weight range 30-50 Kd, although a molecular weight of 17 Kd was indicated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and gradient gel electrophoresis. The RAST inhibition results and the antigenic similarity of saliva to the dust suggest this to be the most likely source of the major rabbit allergen, Ag Rl.