Important animal allergens are lipocalin proteins: why are they allergenic?

Urinary Proteins of Female Domestic Dog (Canis familiaris) during Ovarian Cycle

The presence and identity of non-volatile chemical signals remain elusive in canines. In this study, we aim to evaluate the urinary proteins of female domestic dogs in the estrus and anestrus phases to evidence the presence of non-volatile chemical signals and to elucidate their identities. We collected urine samples from eight female dogs in the estrus and anestrus phases. A total of 240 proteins were identified in the urine samples using liquid chromatography-mass spectrometry (LC-MS analysis). The comparison of the proteins revealed a significant difference between the estrus and anestrus urine. We identified proteins belonging to the lipocalin family of canines (beta-lactoglobulin-1 and beta-lactoglobulin-2, P33685 and P33686, respectively), one of whose function was the transport of pheromones and which was present only in the estrus urine samples. Moreover, proteins such as Clusterin (CLU), Liver-expressed antimicrobial peptide 2 (LEAP2), and Proenkephalin (PENK) were more abundant in the estrus urine when compared to the anestrus urine. LEAP2 was recently described as a ghrelin receptor antagonist and implicated in regulating food intake and body weight in humans and mice. Proenkephalin, a polypeptide hormone cleaved into opioid peptides, was also recognized as a candidate to determine kidney function. As of yet, none of these have played a role in chemical communication. Clusterin, an extracellular chaperone protecting from protein aggregation implicated in stress-induced cell apoptosis, is a plausible candidate in chemical communication, which is a claim that needs to be ascertained further. Data are available via ProteomeXchange with the identifier PXD040418.

Quantitative Proteomic Analysis of the Slime and Ventral Mantle Glands of the Striped Pyjama Squid (Sepioloidea lineolata)

Cephalopods are known to produce an extensive range of secretions including ink, mucus, and venom. Sepiadariidae, a family of small, benthic bobtail squids, are notable for the high volume of viscous slime they emit when stressed. One species, Sepioloidea lineolata (striped pyjama squid), is covered with glands along the perimeter of the ventral mantle, and these structures are hypothesized to be the source of its slime. Using label-free quantitative proteomics, we analyzed five tissue types (dorsal and ventral mantle muscle, dorsal and ventral epithelium, and ventral mantle glands) and the slime from four individuals. In doing so, we were able to determine the relationship between the slime and the tissues as well as highlight proteins that were specifically identified within the slime and ventral mantle glands. A total of 28 proteins were identified to be highly enriched in slime, and these were composed of peptidases and protease inhibitors. Seven of these proteins contained predicted signal peptides, indicating classical secretion, with four proteins having no identifiable domains or similarity to any known proteins. The ventral mantle glands also appear to be the tissue with the closest overall proteomic composition to the slime; therefore, it is likely that the slime originates, at least in part, from these glands.

Occupational Animal Allergy

PURPOSE OF REVIEW

This review explores animal allergen exposure in research laboratories and other work settings, focusing on causes and prevention.

RECENT FINDINGS

(1) Consistent with the hygiene hypothesis, there is new evidence that early childhood exposure to pets produces changes in the gut microbiome that likely lead to a lower risk of allergy. (2) Anaphylaxis from laboratory animal bites occurs more frequently than suggested by prior literature. (3) Animal allergens represent an occupational hazard in a wide variety of work settings ranging from fields that work with animals to public settings like schools and public transportation where allergens are brought into or are present in the workplace. Exposure to animal allergens can result in allergy, asthma, and anaphylaxis. Animal allergy has been most studied in the research laboratory setting, where exposure reduction can prevent the development of allergy. Similar prevention approaches need to be considered for other animal work environments and in all settings where animal allergens are present.

The cat lipocalin Fel d 7 and its cross-reactivity with the dog lipocalin Can f 1

We investigated the prevalence of sensitization to the cat lipocalin Fel d 7 among 140 cat-sensitized Swedish patients and elucidated its allergenic activity and cross-reactivity with the dog lipocalin Can f 1. Sixty-five of 140 patients had IgE to rFel d 7 whereof 60 also had IgE to rCan f 1. A moderate correlation between IgE levels to rFel d 7 and rCan f 1 was found. rFel d 7 activated basophils in vitro and inhibited IgE binding to rCan f 1 in 4 of 13 patients, whereas rCan f 1 inhibited IgE binding to rFel d 7 in 7 of 13 patients. Fel d 7 and Can f 1 showed high similarities in protein structure and epitopes in common were found using cross-reactive antisera. Fel d 7 is a common allergen in a Swedish cat-sensitized population that cross-reacts with Can f 1, and may contribute to symptoms in cat- but also in dog-allergic patients.

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.

Maximizing lipocalin prediction through balanced and diversified training set and decision fusion

Lipocalins are short in sequence length and perform several important biological functions. These proteins are having less than 20% sequence similarity among paralogs. Experimentally identifying them is an expensive and time consuming process. The computational methods based on the sequence similarity for allocating putative members to this family are also far elusive due to the low sequence similarity existing among the members of this family. Consequently, the machine learning methods become a viable alternative for their prediction by using the underlying sequence/structurally derived features as the input. Ideally, any machine learning based prediction method must be trained with all possible variations in the input feature vector (all the sub-class input patterns) to achieve perfect learning. A near perfect learning can be achieved by training the model with diverse types of input instances belonging to the different regions of the entire input space. Furthermore, the prediction performance can be improved through balancing the training set as the imbalanced data sets will tend to produce the prediction bias towards majority class and its sub-classes. This paper is aimed to achieve (i) the high generalization ability without any classification bias through the diversified and balanced training sets as well as (ii) enhanced the prediction accuracy by combining the results of individual classifiers with an appropriate fusion scheme. Instead of creating the training set randomly, we have first used the unsupervised Kmeans clustering algorithm to create diversified clusters of input patterns and created the diversified and balanced training set by selecting an equal number of patterns from each of these clusters. Finally, probability based classifier fusion scheme was applied on boosted random forest algorithm (which produced greater sensitivity) and K nearest neighbour algorithm (which produced greater specificity) to achieve the enhanced predictive performance than that of individual base classifiers. The performance of the learned models trained on Kmeans preprocessed training set is far better than the randomly generated training sets. The proposed method achieved a sensitivity of 90.6%, specificity of 91.4% and accuracy of 91.0% on the first test set and sensitivity of 92.9%, specificity of 96.2% and accuracy of 94.7% on the second blind test set. These results have established that diversifying training set improves the performance of predictive models through superior generalization ability and balancing the training set improves prediction accuracy. For smaller data sets, unsupervised Kmeans based sampling can be an effective technique to increase generalization than that of the usual random splitting method.

Human CD4+ T cell responses to the dog major allergen Can f 1 and its human homologue tear lipocalin resemble each other

Lipocalin allergens form a notable group of proteins, as they contain most of the significant respiratory allergens from mammals. The basis for the allergenic capacity of allergens in the lipocalin family, that is, the development of T-helper type 2 immunity against them, is still unresolved. As immunogenicity has been proposed to be a decisive feature of allergens, the purpose of this work was to examine human CD4+ T cell responses to the major dog allergen Can f 1 and to compare them with those to its human homologue, tear lipocalin (TL). For this, specific T cell lines were induced in vitro from the peripheral blood mononuclear cells of Can f 1-allergic and healthy dog dust-exposed subjects with peptides containing the immunodominant T cell epitopes of Can f 1 and the corresponding TL peptides. We found that the frequency of Can f 1 and TL-specific T cells in both subject groups was low and close to each other, the difference being about two-fold. Importantly, we found that the proliferative responses of both Can f 1 and TL-specific T cell lines from allergic subjects were stronger than those from healthy subjects, but that the strength of the responses within the subject groups did not differ between these two antigens. Moreover, the phenotype of the Can f 1 and TL-specific T cell lines, determined by cytokine production and expression of cell surface markers, resembled each other. The HLA system appeared to have a minimal role in explaining the allergenicity of Can f 1, as the allergic and healthy subjects' HLA background did not differ, and HLA binding was very similar between Can f 1 and TL peptides. Along with existing data on lipocalin allergens, we conclude that strong antigenicity is not decisive for the allergenicity of Can f 1.

Anaphylaxis as a manifestation of horse allergy

Allergic disease induced by animal exposure is a common phenomenon worldwide. Whereas cat and dog dander exposure are well recognized as causative of allergic rhinitis, allergic asthma, and contact urticaria, horse allergy can present with anaphylaxis. Horse allergy is induced by exposure to the major horse allergens Equ 1 through 5. The severity of the symptoms may be related to the level of exposure. Greatest risk of anaphylaxis occurs in those sensitized patients who have large amounts of animal allergen exposure, such as when in a barn, or when an animal bite occurs exposing sensitized persons to large quantities of the animal allergen that resides in the saliva. Horse allergy may be successfully treated with allergen specific immunotherapy.

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.

Characterization of occupational sensitization by multiallergen immunoblotting in workers exposed to laboratory animals

BACKGROUND

Studies have estimated that 10% to 23% of workers exposed to laboratory animals report symptoms of laboratory animal allergy.

OBJECTIVES

To determine the level of occupational sensitization in workers exposed to laboratory animals and to develop a diagnosis system based on a multiallergen IgE immunoblot.

METHODS

A total of 75 workers exposed to laboratory animals were initially studied with skin prick tests performed with animal epithelia extracts. The workers with suspected occupational disease and positive skin prick test results were further studied with the ImmunoCAP system to determine specific IgE levels to urine and epithelia allergens and with multiallergen IgE immunoblotting to detect specific IgE levels to epithelia allergens and bovine serum albumin.

RESULTS

Twenty of the 75 workers were studied with ImmunoCAP and multiallergen IgE immunoblotting. Nine were polysensitized and 3 were sensitized to only one animal. The results obtained by ImmunoCAP and multiallergen IgE immunoblotting were concordant except for in 3 workers, who had low or negative values of specific IgE determined by ImmunoCAP but positive allergen detections by immunoblotting. On the basis of the results of the study and the clinical symptoms related by workers, 16% were diagnosed as having occupational allergy.

CONCLUSIONS

Multiallergen immunoblotting by means of a unique test offers a graphic representation of sensitization to the different animals to which workers are exposed, providing additional information on the clinical symptoms caused by the involved allergens. The results presented suggest that this system can improve the diagnosis of laboratory animal allergy by obtaining a sensitization profile for each exposed worker.

Mammalian lipocalin allergens--insights into their enigmatic allergenicity

Most of the important mammal-derived respiratory allergens, as well as a milk allergen and a few insect allergens, belong to the lipocalin protein family. As mammalian lipocalin allergens are found in dander, saliva and urine, they disperse effectively and are widely present in the indoor environments. Initially, lipocalins were characterized as transport proteins for small, principally hydrophobic molecules, but now they are known to be involved in many other biological functions. Although the amino acid identity between lipocalins is generally at the level of 20-30%, it can be considerably higher. Lipocalin allergens do not exhibit any known physicochemical, functional or structural property that would account for their allergenicity, that is, the capacity to induce T-helper type 2 immunity against them. A distinctive feature of mammalian lipocalin allergens is their poor capacity to stimulate the cellular arm of the human or murine immune system. Nevertheless, they induce IgE production in a large proportion of atopic individuals exposed to the allergen source. The poor capacity of mammalian lipocalin allergens to stimulate the cellular immune system does not appear to result from the function of regulatory T cells. Instead, the T cell epitopes of mammalian lipocalin allergens are few and those examined have proved to be suboptimal. Moreover, the frequency of mammalian lipocalin allergen-specific CD4(+) T cells is very low in the peripheral blood. Importantly, recent research suggests that the lipocalin allergen-specific T cell repertoires differ considerably between allergic and healthy subjects. These observations are compatible with our hypothesis that the way CD4(+) T-helper cells recognize the epitopes of mammalian lipocalin allergens may be implicated in their allergenicity. Indeed, as several lipocalins exhibit homologies of 40-60% over species, mammalian lipocalin allergens may be immunologically at the borderline of self and non-self, which would not allow a strong anti-allergenic immune response against them.

Prawn lipocalin: characterization of a color shift induced by gene knockdown and ligand binding assay

The lipocalin family of proteins functions in the transport of steroids, carotenoids, retinoids, and other small hydrophobic molecules. Recently, a lipocalin (MrLC) was isolated from the prawn Macrobrachium rosenbergii and its expression varied with the molting cycle. In this study, knockdown of the MrLC gene by RNA interference (RNAi) was performed and resulted in a shift in body color from blue to orangish red over the entire carapace. By immune-gold electron microscopy, MrLC was found to co-localize with the lipid droplets in subepidermal adiose tissue that were found to be decreased dramatically in MrLC knockdown prawns, in which a reduction in relative fat content was also quantified. Furthermore, MrLC was found to specifically bind astaxanthin and molt hormone (20-hydroxyecdysone) in both in vitro ligand binding assay and in vivo native ligand detection. These results suggested that MrLC plays roles in the regulation of coloration through its association with astaxanthin and may also be involved in the regulation of molting in crustacean.

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.

The vomeronasal organ mediates interspecies defensive behaviors through detection of protein pheromone homologs

Potential predators emit uncharacterized chemosignals that warn receiving species of danger. Neurons that sense these stimuli remain unknown. Here we show that detection and processing of fear-evoking odors emitted from cat, rat, and snake require the function of sensory neurons in the vomeronasal organ. To investigate the molecular nature of the sensory cues emitted by predators, we isolated the salient ligands from two species using a combination of innate behavioral assays in naive receiving animals, calcium imaging, and c-Fos induction. Surprisingly, the defensive behavior-promoting activity released by other animals is encoded by species-specific ligands belonging to the major urinary protein (Mup) family, homologs of aggression-promoting mouse pheromones. We show that recombinant Mup proteins are sufficient to activate sensory neurons and initiate defensive behavior similarly to native odors. This co-option of existing sensory mechanisms provides a molecular solution to the difficult problem of evolving a variety of species-specific molecular detectors.

IgE binding reactivity of peptide fragments of Bla g 4, a major German cockroach allergen

Cockroaches have been recognized as a major cause of asthma. Bla g 4 is one of the most important German cockroach allergens. The aim of this study is to investigate IgE reactivity to the recombinant Bla g 4 (rBla g 4) in the sera of allergic patients and identify linear IgE binding epitope. For protein expression, full-length Bla g 4 (EF202172) was divided into 5 overlapping peptide fragments (E1: aa 1-100, E2: aa 34-77, E3: aa 74-117, E4: aa 114-156, and E5: aa 153-182). The full-length and 5 peptide fragments of Bla g 4 was generated by PCR and over-expressed in E. coli BL21 (DE3). The IgE binding reactivities of the full-length and peptide fragments were measured by ELISA using 32 serum samples of cockroach allergy. The sera of 8 patients (25%) reacted with rBla g 4. Four sera (100%) showed IgE-binding reactivity to full-length and peptide fragment 4, and 2 sera (50%) reacted with peptide fragment 2. One (20%) serum reacted with peptide fragment 3. The results of ELISA using overlapping recombinant fragments indicated that the epitope region was located at amino acid sequences 34-73 and 78-113, and major IgE epitope of Bla g 4 was located at amino acid sequences 118-152 of C-terminal. B-cell epitope analysis of German cockroach allergen Bla g 4 could contribute to the strategic development of more specific and potentially efficacious immunotherapy.

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.

Immunotherapeutic potential of the immunodominant T-cell epitope of lipocalin allergen Bos d 2 and its analogues

Lipocalin allergens, which contain most of the important animal-derived respiratory sensitizers, induce T helper type 2 (Th2) deviation, but the reasons for this are not clear. To explore the prospects for peptide-based allergen immunotherapy and to elucidate the characteristics of the immunodominant epitope of Bos d 2, BALB/c mice were immunized with a peptide containing the epitope, peptides containing its analogues, peptides from the corresponding regions of other lipocalin proteins, and peptides with a homologous sequence. We observed that murine spleen cells recognized the immunodominant epitope of Bos d 2, p127-142, in almost the same way as human Bos d 2-specific T cells did. Enzyme-linked immunosorbent spot-forming cell assay (ELISPOT) analyses showed that p127-142 and a corresponding peptide from horse Equ c 1 induced a Th2-deviated cellular response, whereas a homologous bacterial peptide from Spiroplasma citri induced a Th0-type response. Interestingly, the spleen cell response to the bacterial peptide and p127-142 was cross-reactive, that is, able to induce reciprocally the proliferation and cytokine production of primed spleen cells in vitro. More importantly, the peptides were able to skew the phenotype of T cells primed with the other peptide. Our results suggest that modified peptides can be useful in allergen immunotherapy.

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.

Prevalence and host determinants of occupational bronchial asthma in animal shelter workers

OBJECTIVE

We examined the risk factors for the development of airway allergy in animal shelter workers.

METHODS

The study population comprised 88 animal shelter workers occupationally exposed to cats and dogs. They responded to a questionnaire concerning the history of exposure to animal allergens and job characteristics and were subjected to skin prick test (SPT) to common and occupational allergens (cat and dog), and determination of total serum IgE level and specific IgE. In addition, SPT with rat and mouse allergens were performed. Bronchial hyperreactivity and peak expiratory flow rate were measured at work and off work only in workers with work-related symptoms suggestive of occupational asthma (OA).

RESULTS

The prevalence of OA was 9.1%. Sensitization to dog allergens was higher than to cats. The multivariate logistic regression analysis revealed a significant role of positive family history of atopy and having a dog as pet in the past for the development of occupational airway allergy (OR 5.9; 95% CI 1.76, 20.00; P = 0.003; OR 6.47; 95% CI 1.90, 22.02; P = 0.002, respectively). In the multivariate logistic regression analysis, the risk for developing OA was most clearly associated with growing up in the country (OR 7.59; 95% CI 1.25, 45.9; P = 0.025).

CONCLUSIONS

Allergic disease is a serious occupational health concern for subjects who have occupational contact with cats and dogs.

Risk factors associated with airway allergic diseases from exposure to laboratory animal allergens among veterinarians

OBJECTIVES

Investigate the risk factors for the development of occupational airway allergy (OAA) from exposure to laboratory animal allergens (LAA) among Polish veterinarians.

METHODS

Two hundred veterinarians responded to the questionnaire and were subjected to skin prick test (SPT) to common allergens and LAA (rat, mouse, hamster, guinea pig, rabbit). Evaluation of total serum IgE level and specific IgE against occupational allergens was performed. In addition, bronchial hyperreactivity (BHR) and peak expiratory flow rate (PEFR) were measured before and after specific challenge testing (SCT) only in the subjects with work-related symptoms suggestive of occupational asthma (OA).

RESULTS

The prevalence of asthmatic and ocular symptoms was statistically more prevalent in the group of veterinarians sensitised to LAA versus non-sensitised subjects. The most frequent occupational allergens of skin and serum reactivity were LAA (44.5 and 31.5%, respectively). In 41 (20.5%) and in 22 (11%) subjects out of 200 veterinarians, serum specific IgE to natural rubber latex (NRL) allergens and disinfectants was also found. Serum sensitisation to cat allergens and daily contact with laboratory animals (LA) increased the risk for developing isolated occupational rhinitis. Furthermore, working time of more than 10 years and daily contact with LA were also significant risk factors for the development of OAA. Measuring PEFR and BHR before and after SCT is a useful method to confirm the presence of OA.

CONCLUSIONS

Allergy to LAA is an important health problem among veterinary medicine practitioners in Poland.

The DR4-DQ8 haplotype and a specific T cell receptor Vbeta T cell subset are associated with absence of allergy to Can f 1

BACKGROUND

The significance of specific T cell receptor (TCR) Vbeta subtypes and human leucocyte antigen (HLA) class II alleles for the development of allergy to lipocalin allergens such as the major dog allergen Can f 1 is not clear at present.

OBJECTIVE

To characterize the TCR Vbeta usage in the Can f 1-specific T cell lines and the HLA class II genotypes of Can f 1-allergic and non-allergic subjects.

METHODS

T cell lines were induced with recombinant Can f 1 from the peripheral blood mononuclear cells of 12 non-atopic dog owners and 26 dog-allergic patients. Thirteen of the dog-allergic subjects were sensitized to Can f 1. Expression of the TCR Vbeta subtypes on CD4(+) T cells in the T cell lines was measured by flow cytometry. The subjects were HLA genotyped for DRB1, DQB1 and DPB1 loci.

RESULTS

Can f 1-specific T cell lines were obtained from 18 subjects, with either positive (n=8) or negative (n=10) skin prick tests (SPTs) to recombinant Can f 1. The frequency of TCR Vbeta5.1(+) T cells was significantly higher in the T cell lines of subjects with negative SPTs to the allergen. Moreover, DR4-DQ8 haplotype was over-represented among these subjects.

CONCLUSION

The DR4-DQ8 haplotype and the TCR Vbeta5.1(+) CD4(+) T cells may be protective against allergy to Can f 1.

Lysine as a Critical Amino Acid for IgE Binding in Phl p 5b C Terminus

BACKGROUND

Allergens induce the formation of specific immunoglobulin (Ig)E and harbor at least two IgE-binding regions (epitopes) to facilitate crosslinking of basophilic or mast-cell-bound specific IgE antibodies. Studies mapping linear epitopes have shown that these regions often contain charged or hydrophobic amino acids. Nevertheless, these studies are hampered by limited significance due to the often conformational nature of IgE epitopes. This prompted us to study the role of lysines in the context of an intact 3-dimensional model.

METHODS

Major allergen Phl p 5b from timothy grass bears 12 lysines in its C-terminal half. Using site-directed mutagenesis, we substituted all 10 surface-exposed lysines by alanines.

RESULTS

Although structural integrity of the lysine-deficient mutant was not altered, IgE-binding capacity measured by ELISA inhibition tests and crosslinking activity in ex vivo basophil stimulation and in vivo skin prick tests were significantly diminished. Interestingly, binding of specific IgG antibodies was considerably less reduced by loss of lysines.

CONCLUSION

Lysine is an important amino acid for IgE binding in more than one epitope of major grass pollen allergen Phl p 5b C terminus. Allergenicity, but not IgG binding of the molecule, is substantially diminished by single amino acid substitutions without structural integrity being hampered.

Determination of the T cell epitopes of the lipocalin allergen, Rat n 1

BACKGROUND

Laboratory animal allergy (LAA) is an important cause of occupational sensitization and asthma. Rats are a frequent cause of LAA and the major rat allergen, Rat n 1, is a member of the lipocalin protein family, which includes several other animal allergens such as the cow allergen, Bos d 2. To date, Bos d 2 is the only mammalian lipocalin allergen to have been studied in detail.

OBJECTIVE

We undertook a cross-sectional study of a large population of individuals exposed to laboratory rats to determine the proliferative responses of peripheral blood mononuclear cells (PBMCs) to the major rat allergen, Rat n 1.

METHODS

Eighty-three cases (defined by a positive skin prick test (SPT) > or =3 mm and/or a positive RAST > or =2% binding) and 274 referents without specific IgE to rats were tested for their proliferative responses of PBMCs to rat allergen. Cytokine release to rat urinary protein was examined in 28 sensitized and 42 non-sensitized exposed individuals.

RESULTS

Proliferation to rat urinary protein was weak in all individuals. Four regions within Rat n 1 were identified as containing potential immunodominant T cell epitopes and three of these co-localized within the conserved regions of the lipocalin molecule. All four regions within Rat n 1 overlapped considerably with the characterized epitopes of the lipocalin allergen, Bos d 2. IL-5 and ratios of IL-5/IFN-gamma were significantly increased in cases.

CONCLUSION

The response to Rat n 1 is remarkably similar to the cow lipocalin allergen Bos d 2. T cell epitopes within lipocalins appear to co-localize with the conserved regions of the molecule. LAA is characterized by an increased production of IL-5. Investigation of other lipocalin allergens will provide further information about the allergenicity of this group of proteins.

Correlation between age and allergens in pediatric atopic dermatitis

BACKGROUND

There has been significant progress recently in the clinical investigation of atopic dermatitis (AD), especially in the recognition of aeroallergens as aggravating factors in AD. However, sensitization to food allergens and aeroallergens in children with AD has not been fully studied.

OBJECTIVE

To evaluate the correlation between age and allergens in children with AD.

METHODS

A retrospective cross-sectional study was performed between January 1, 1999, and December 31, 2002, on 262 children with a definitive diagnosis of AD aged 0 to 16 years. Comparison of 3 age groups (<2 years, 2-5 years, and >5 years) with the correlation of food allergens and aeroallergens using the CAP-FEIA test was made using linear regression and logistic regression analyses.

RESULTS

In children younger than 2 years, AD was associated with food allergens. In children aged 2 to 5 years, both food allergens and aeroallergens played an important role. In children older than 5 years, only elevated aeroallergen specific IgE levels were noted (P < .02). Age correlated negatively with food allergens and positively with aeroallergens after adjusting for sex (P < .04). Sensitization to aeroallergens may correlate with acquisition of the respiratory symptoms of the atopic state.

CONCLUSIONS

Food allergens may be the major trigger of AD in early life, after which the role of environmental aeroallergens become more important and may be associated with respiratory sensitization.

Human IgE response to the Schistosoma haematobium 22.6 kDa antigen

In Schistosoma mansoni and S. japonicum infection, the 22.6 kDa tegumental antigens Sm22.6 and Sj22.6 are principal targets for the human IgE response, and levels of IgE to Sm22.6 have been correlated with resistance to re-infection after chemotherapy. S. haematobium is arguably a more important species in terms of human infection, and in this report we describe for the first time the molecular characterization of a cDNA from S. haematobium (Sh22.6) that is closely homologous to Sm22.6 and Sj22.6. As a member of the tegument-associated antigen family, Sh22.6 possesses EF-hand domains and regions homologous to the dynein light chain domains. We have expressed recombinant Sh22.6 and studied the IgE responses to the antigen in a group of 99 infected individuals (68 children and 31 adults) from an endemic area of Gabon who donated blood before and 5 weeks after praziquantel treatment. IgE to Sh22.6 was detected by ELISA in 18 subjects (18%), and in the majority of responders levels rose between pre- and post-treatment. Interestingly, the proportion of adults expressing IgE to Sh22.6 was 35.5%, significantly higher than the 10.3% seen in children. IgE from at least 10 of the 18 ELISA responders recognized Sh22.6 on Western blots of adult worm extract and recombinant antigen. These results demonstrate that like related molecules in other species, Sh22.6 is a target for the human IgE response. The data also indicate that changes in the IgE response occur with age or with progressive exposure to key antigens.

Characterization of B- and T-cell responses and HLA-DR4 binding motifs of the latex allergen Hev b 6.01 (prohevein) and its post-transcriptionally formed proteins Hev b 6.02 and Hev b 6.03

BACKGROUND

Multiple immunoglobulin E (IgE)-binding proteins in natural rubber latex extracts have been identified. In the case of Hev b 6 a differentiation was made between the precursor protein prohevein (Hev b 6.01) and its two post-transcriptionally formed proteins, the N-terminal hevein (Hev b 6.02) and the C-terminal domain (Hev b 6.03). All three components act as independent allergens. The aim of this study was a detailed analysis of the T-cell responses and the IgE-binding capacity of Hev b 6.01, Hev b 6.02 and Hev b 6.03 by using these allergens as recombinant maltose-binding fusion (MBP) proteins and the usage of synthetic modified hevein peptides.

METHODS

Latex-allergic health care workers (HCWs) suffering from rhinitis, conjunctivitis, contact urticaria and/or asthma with increased specific IgE-antibodies to latex were tested for their IgE-binding capacity and T-cell reactivity (by proliferation response) to the recombinant MBP-rHev b 6.01, MBP-rHev b 6.02, MBP-rHev b 6.03, to native Hev b 6.02, to modified hevein peptides and wheat germ agglutinin (WGA). For testing of the human leucocyte antigen (HLA) class II restriction of MBP-rHev b 6.01 induced peripheral blood mononuclear cell (PBMC) responses, monoclonal antibodies against HLA-DR, HLA-DP or HLA-DQ were added.

RESULTS

Seventeen of 18 (94%) serum samples from latex-allergic HCWs had increased levels of specific IgE to MBP-rHev b 6.01, 16 (89%) to MBP-rHev b 6.02 and 13 (72%) to MBP-rHev b 6.03. A significant difference existed between the specific IgE-values of MBP-rHev b 6.02 and MBP-rHev b 6.03 (P < 0.01). Proliferation responses of PBMC of the same 18 latex-allergic patients were positive for MBP-rHev b 6.01 and MBP-rHev b 6.03 in 83 and 67% of the tested PBMC suspension, whereas the proliferation responses induced with MBP-rHev b 6.02 or native Hev b 6.02 were very low (5.6 and 22.2%). Sera from nine additional latex-allergic patients showed specific IgE binding to the native Hev b 6.02, but none of these sera showed specific IgE binding to the modified Hev b 6.02-peptides [whereby all eight cysteine residues were substituted by serine (C --> S) or by alanine (C --> A)]. Proliferation responses induced by the modified Hev b 6.02 peptides were not significantly different from that induced by Hev b 6.02. Potential HLA-DR4Dw4(DRB1*0401)-restricted T-cell epitopes of Hev b 6.01 predicted by two computer algorithms were only found in the Hev b 6.03-part of Hev b 6.01.

CONCLUSION

In the Hev b 6.01 precursor the regions responsible for IgE binding and those for inducing the T-cell proliferation responses are settled in different parts of the protein. The Hev b 6.02 domain is responsible for IgE binding and carries discontinuous B-cell epitopes whereas Hev b 6.03 is a better inducer of a proliferation response and contains HLA-DR4-binding motifs.

Further characterization of IgE-binding antigens from guinea pig hair as new members of the lipocalin family

BACKGROUND

Guinea pigs are important sources of inhalant allergens in home and working environments. However, little is known about the molecular characteristics and the relevant epitopes of guinea pig allergens. Recently, several allergens have been identified in hair extract and urine, and the major allergen Cav p 1 (20 kDa) has been characterized.

OBJECTIVE

The aim of the present study was to isolate and to characterize a further major allergen from guinea pig hair with 17 kDa.

METHODS

Guinea pig hair extract was fractionated using anion exchange chromatography and reverse-phase high performance liquid chromatography. Analyses were carried out by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, 2D-PAGE, immunoblotting, immunoblot inhibition, glycoprotein detection, and N-terminal amino acid sequencing.

RESULTS

The nonglycosylated 17 kDa allergen, which was named Cav p 2, was purified to homogeneity. On the basis its 15 N-terminal residues, there was 69% identity with a sequence of Bos d 2, an allergenic protein from cow dander belonging to the lipocalin family. The 2D-immunoblotting analyses of guinea pig hair extract demonstrated that Cav p 2 and Cav p 1, contained several isoforms with pI values ranging from 3.6 to 5.3. The 2D-immunoblot inhibition disclosed cross-reactive IgE epitopes on the allergens Cav p 2 and Cav p 1. Furthermore, Cav p 1 can form both monomers (20 kDa) and dimers (40-42 kDa).

CONCLUSION

These studies provide important information on the isoallergen character of two relevant guinea pig allergens Cav p 1 and Cav p 2 as well as on their cross-reactive properties.

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.

Effect of heat denaturation on beta-lactoglobulin-induced gastrointestinal sensitization in rats: denatured betaLG induces a more intensive local immunologic response than native betaLG

Beta-lactoglobulin (betaLG) is one of the first foreign antigens encountered by a newborn child, and it is the major allergen causing cow's milk allergy. Heat denaturation causes changes to the protein structure, but the significance of heat-induced changes for immunogenicity or allergenicity is not known. To clarify how heat denaturation affects allergenicity and immunogenicity, we immunized Hooded-Lister rat pups with intra-peritoneal injections of native or heat-denatured betaLG at days 43 and 62 after birth. The animals were then fed native and denatured milk products twice weekly from 73 to 101 days of age with a feeding tube, after which they were allowed cheese and milk ad libitum, until they were killed on day 131. Total immunoglobulin (Ig)E and betaLG-specific IgG1 and IgG2a levels were determined from serum samples. Spontaneous interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) production was measured from duodenal specimens, and specimens of gastrointestinal mucosae were studied for the presence of inflammatory cells. The rats immunized with native betaLG had higher levels of total serum IgE than the unimmunized controls or the rats immunized with heat-denatured betaLG, while heat-denatured betaLG induced a significantly more intensive mononuclear inflammatory cell and eosinophil infiltration in the gastroduodenal mucosa. The betaLG-specific IgG antibody and IL-4 and IFN-gamma responses were similar in the two groups of immunized animals. Hence, denaturation modifies the immunogenic and allergenic properties of betaLG. Heat-denatured betaLG induces a more intensive local reaction in the gastrointestinal mucosa, while there is some evidence for enhanced systemic allergic sensitization by native betaLG.

Purification and partial characterization of the major allergen, Cav p 1, from guinea pig Cavia porcellus

BACKGROUND

Allergic reaction to guinea pig has been recognized as a problem in domestic settings and work environments for many years. Until recently, limited information was available on the properties of guinea pig allergen(s). In this study the major allergen Cav p 1 was characterized and the N-terminal amino-acid sequence was determined.

METHODS AND RESULTS

Sera from 40 patients with IgE-mediated allergy to guinea pigs were investigated by means of immunoblotting using extracts prepared from guinea pig hair and urine. Three major allergens were identified within both sources with molecular weights (MW) of 8 kDa, 17 kDa and 20 kDa, respectively. From aqueous hair extracts the 20 kDa allergen (Cav p 1) was purified to homogeneity by anion exchange chromatography and reverse-phase HPLC and the N-terminal amino-acid sequence was determined. On the basis of the 15 residues, 57% identity was obtained from computer search with a sub-sequence of MUP (major urinary protein), a member of the lipocalin superfamily. Allergenic relationships among guinea pig allergens derived from various sources (hair and urine) or different animal species (mouse, rat, cat) were studied by ELISA inhibition assays. Neither urine of mouse, rat and cat, nor hair extracts of rat and cat produced appreciable inhibitions in guinea pig ELISA.

CONCLUSION

Although the physicochemical characteristics of isolated Cav p 1 are very similar to those for other rodent allergens and furthermore partial sequence identity with Mus m 1 was found, it is clearly shown here to be an immunologically independent major allergen.

Lipocalin allergen Bos d 2 is a weak immunogen

The immunological characteristics of an important group of animal-derived allergens, lipocalins, are poorly known. To explore the immunology of the lipocalin allergen Bos d 2, several mouse strains with different H-2 haplotypes were immunized with the allergen. Only the BALB/c mouse mounted a distinct humoral response against Bos d 2. The proliferative spleen cell responses of all mouse strains remained very weak. Further experiments with BALB/c mice confirmed that Bos d 2 is a weak inducer of both humoral and cellular responses, and that the responses were weaker than with the control antigens hen egg lysozyme (HEL) and tetanus toxoid. IgG subclass analyses showed that Bos d 2 was prone to favor the T(h)2 response. Although s.c. immunization using complete Freund's adjuvant favored the T(h)1-deviated immune response by lymph node cells, Bos d 2 was able to induce the production of IL-4 while the control antigen HEL did not. Epitope mapping revealed that BALB/c mice recognized one immunodominant epitope in Bos d 2, almost identical to that recognized by humans. The epitope was shown to be immunogenic in subsequent experiments. However, further studies are needed to clarify the significance of priming and stimulation doses of the immunodominant and other epitopes in Bos d 2 for the outcome of immune response against the allergen. The murine immune response against Bos d 2 closely resembled that observed in humans. The weak immunogenicity of Bos d 2 may be associated with its allergenicity.

Microarrayed allergen molecules: diagnostic gatekeepers for allergy treatment

Type I allergy is an immunoglobulin E (IgE)-mediated hypersensitivity disease affecting more than 25% of the population. Currently, diagnosis of allergy is performed by provocation testing and IgE serology using allergen extracts. This process defines allergen-containing sources but cannot identify the disease-eliciting allergenic molecules. We have applied microarray technology to develop a miniaturized allergy test containing 94 purified allergen molecules that represent the most common allergen sources. The allergen microarray allows the determination and monitoring of allergic patients' IgE reactivity profiles to large numbers of disease-causing allergens by using single measurements and minute amounts of serum. This method may change established practice in allergy diagnosis, prevention, and therapy. In addition, microarrayed antigens may be applied to the diagnosis of autoimmune and infectious diseases.

Methods and effectiveness of indoor environmental control

LEARNING OBJECTIVES

The purpose of this review is to describe recommended methods of decreasing exposure to indoor allergens.

DATA SOURCES

Data were obtained from published studies and reviews.

STUDY SELECTION

The reviewed studies met these criteria: 1) measurement of environmental allergens; 2) selection of participants with clearly defined allergic airway disease confirmed by detection of allergen-specific immunoglobulin E; and 3) clearly defined clinical and environmental outcomes. The studies were conducted as controlled clinical trials and the results between treated and control groups were compared with appropriate statistics.

RESULTS

The results of these studies show that installing allergen proof encasings and washing bedding frequently reduces house-dust mite exposure by 10-fold or more and significantly improves clinical measures of asthma. Washing pets reduces allergen levels temporarily. Excluding the pet from the bedroom while installing allergen-proof encasings and operating air cleaner reduces airborne allergens although having no significant effect on allergic symptoms. Cockroach populations can be controlled for over 6 months and allergens can be reduced with controlled pesticide application and cleaning, but clinical correlates have not been reported. Methods to improve adherence to environmental control measures have not been tested but effective methods can be recommended from literature on medication adherence.

CONCLUSIONS

For patients allergic to indoor allergens, reasonable recommendations include installation of allergen-impermeable encasings, frequent laundering of bedding, removing furred pets from the home, and controlling of cockroach populations with effective pesticides using the principles of integrated pest management.

Working with male rodents may increase risk of allergy to laboratory animals

BACKGROUND

Our aim was to study the risk of laboratory animal allergy (LAA) among research staff working in laboratories separate from the animal confinement area. The roles of atopy and exposure intensity in LAA were studied with special regard to exposure to male rodents, who excrete higher levels of urinary allergens than female rodents.

METHODS

Eighty rodent-exposed subjects gave blood samples for the analysis of total IgE, Phadiatop, and specific IgE against rat (RUA) and mouse urinary allergens (MUA), and answered questionnaires. Air samples were collected for RUA and MUA aeroallergen measurement in both laboratories and animal confinement facilities.

RESULTS

Twenty percent of the subjects had IgE >0.35 kU/l to RUA and/or MUA, and 32% had experienced animal work-related symptoms, although 90% of aeroallergen samples from the research department laboratories were below the detection limit (<0.26 ng RUA per m(3) and <0.8 ng MUA per m(3)). Atopy (positive Phadiatop), total IgE >100 kU/l, other allergies (especially to other animals), or more than 4 years of exposure significantly increased laboratory animal sensitization and symptoms. Working with mainly male rodents gave odds ratios (95% CI) of 3.8 (0.97-15) for sensitization and 4.4 (1.4-14) for symptoms. Subjects with both exposure to mainly male rodents and atopy or elevated total IgE had a 10-fold higher frequency of sensitization than exposed subjects with neither risk factor.

CONCLUSION

A majority of subjects with a combination of exposure to mainly male rodents and atopy or elevated total IgE developed sensitization to and symptoms from laboratory animals. Current low exposure seems to maintain the presence of specific IgE. Further measures must be undertaken to provide a safe workplace for laboratory animal workers.

Identification, cloning, and recombinant expression of procalin, a major triatomine allergen

Among the most frequent anaphylactic reactions to insects are those attributed to reduviid bugs. We report the purification and identification of the major salivary allergen of these insects. This 20-kDa protein (procalin) is a member of the lipocalin family, which includes salivary allergens from other invertebrates and mammals. An expression system capable of producing reagent quantities of recombinant allergen was developed in Saccharomyces cerevisiae. Antisera produced against recombinant protein cross-reacts with ELISA with salivary allergen. Recombinant Ag is also shown to react with sera from an allergic patient but not with control sera. By immunolocalization, the source of the salivary Ag is the salivary gland epithelium and its secretions.

Lipocalin allergens

Most animal-derived major allergens causing respiratory sensitization belong to the family of proteins called lipocalins. Their sequential identity varies but the three-dimensional structure is conserved. They are present in body fluids and secretions. Several lipocalins are able to bind and transport small hydrophobic ligands like retinol. The immunological characteristics of lipocalin allergens are poorly known. Cow dust-derived allergen, Bos d2, which is a potent inducer of IgE production, was observed to induce the weak proliferative responses of peripheral blood mononuclear cells of asthmatic patients upon stimulation in vitro. The responses were Th2-deviated and directed to a few epitopes in Bos d2. One of the epitopes, situated adjacent to a structurally conserved region of lipocalins, was recognized by the T cells of all patients. Computer predictions suggested that human endogenous lipocalins may contain epitopes in the corresponding region. We have proposed that the allergenicity of lipocalins may be associated with the adaptation of the immune system to the presence of endogenous lipocalins.

Biochemical characterization and surfactant properties of horse allergens

A new allergen from horse dander, Equ c 5 has been purified. Its biochemical and biophysical properties have been characterized and compared with those of Equ c 1, Equ c 2 and Equ c 4. Their molecular masses, determined by mass spectrometry, were 22 kDa for Equ c 1, 16 kDa for Equ c 2, 18.7 kDa for Equ c 4 and 16.7 kDa for Equ c 5. Their pI values were between 3.8 and 5.25. Equ c 2 and Equ c 5 are not glycosylated, while Equ c 4 contains a tri-antennary tri-sialylated N-linked glycan. Linkages of terminal N-acetylneuraminic acid to galactose were: alpha-(2-->6) in Equ c 4, and both alpha-(2-->3) and alpha-(2-->6) in Equ c 1. Oligosaccharide portions of Equ c 1 or Equ c 4 were barely involved in IgE-immunoreactivity. Partial N-terminal sequence of Equ c 4 shares a significant sequence homology with the rat submandibular gland protein A. No matching was found for two internal peptides of Equ c 5. Surfactant properties of horse allergens as well as other proteins were investigated. In contrast to Equ c 2 and Equ c 3, solutions of Equ c 1, Equ c 4 and Equ c 5 significantly lowered the surface tension. Relationship between a property such as this, involving oriented hydrophobic patches of a molecule and allergenicity, is addressed.

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.

Mechanism and epidemiology of laboratory animal allergy

Laboratory animal allergy (LAA) is a form of occupational allergic disease. The development of laboratory animal allergy is due to the presence of IgE antibodies directed against animal proteins. The process of sensitization (development of IgE antibodies) is a complex process which involves interaction of antigen presenting cells and lymphocytes of the Th-2 cell type. These cells generate a host of cytokines and other factors which lead to immediate hypersensitivity reactions and other factors which lead to immediate hypersensitivity reactions and the generation of allergic inflammation. Typical symptoms of laboratory animal allergy include nasal symptoms, such as sneezing, watery discharge, and congestion. Skin rashes are also common. Asthma, which produces symptoms of cough, wheezing, and shortness of breath, may affect 20-38% of workers who are sensitized to laboratory animal allergens. Rarely a generalized, life-threatening allergic reaction (anaphylaxis) may occur. The estimated prevalence of laboratory animal allergy is variable depending on the method used for diagnosis, but nonetheless may affect up to 46% of exposed workers. The presence of pre-existing allergies to non-work place allergens (e.g., dust mite, pollens, molds), exposure to laboratory animal allergens, and possibly tobacco smoking are risk factors for the development of laboratory animal allergy. Progress in the understanding of the mechanism and epidemiology of laboratory animal allergy will lead to improved methods for its prevention.

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.

Structural biology of allergens

One of the major challenges of molecular allergy is to predict the allergenic potential of a protein, particularly in novel foods. Two aspects have to be distinguished: immunogenicity and cross-reactivity. Immunogenicity reflects the potential of a protein to induce IgE antibodies, whereas cross-reactivity is the reactivity of (usually preexisting) IgE antibodies with the target protein. In addition to these two issues, the relation between IgE-binding potential and clinical symptoms is of interest. This is influenced by physical properties (eg, stability and size) and immunologic properties (affinity and epitope valence). Discussions on immunogenicity and cross-reactivity of allergens rely on the establishment of structural similarities and differences among allergens and between allergens and nonallergens. For comparisons between the 3-dimensional protein folds, the representation as 2-dimensional proximity plots provides a convenient visual aid. Analysis of approximately 40 allergenic proteins (or parts of these proteins), of which the protein folds are either known or can be predicted on the basis of homology, indicates that most of these can be classified into 4 structural families: (1) antiparallel beta-strands: the immunoglobulin-fold family (grass group 2, mite group 2), serine proteases (mite group 3, 6, and 9), and soybean-type trypsin inhibitor (Ole e 1, grass group 11); (2) antiparallel beta-sheets intimately associated with one or more alpha-helices: tree group 1, lipocalin, profilin, aspartate protease (cockroach group 2); (3) (alpha+beta) structures, in which the alpha- and beta-structural elements are not intimately associated: mite group 1, lysozyme/lactalbumin, vespid group 5; and (4) alpha-helical: nonspecific lipid transfer protein, seed 2S protein, insect hemoglobin, fish parvalbumin, pollen calmodulin, mellitin from bee venom, Fel d 1 chain 1, serum albumin. Allergens with parallel beta-strands (in combination with an alpha-helix linking the two strands, a motif commonly found in, for example, nucleotide-binding proteins) seem to be underrepresented. The conclusion is that allergens have no characteristic structural features other than that they need to be able to reach (and stimulate) immune cells and mast cells. Within this constraint, any antigen may be allergenic, particularly if it avoids activation of T(H)2-suppressive mechanisms (CD8 cells and T(H)1 cells).