Analysis of allergens in rat fur and saliva

Perspectives of Proteomics in Respiratory Allergic Diseases

Proteomics in respiratory allergic diseases has such a battery of techniques and programs that one would almost think there is nothing impossible to find, invent or mold. All the resources that we document here are involved in solving problems in allergic diseases, both diagnostic and prognostic treatment, and immunotherapy development. The main perspectives, according to this version, are in three strands and/or a lockout immunological system: (1) Blocking the diapedesis of the cells involved, (2) Modifications and blocking of paratopes and epitopes being understood by modifications to antibodies, antagonisms, or blocking them, and (3) Blocking FcεRI high-affinity receptors to prevent specific IgEs from sticking to mast cells and basophils. These tools and targets in the allergic landscape are, in our view, the prospects in the field. However, there are still many allergens to identify, including some homologies between allergens and cross-reactions, through the identification of structures and epitopes. The current vision of using proteomics for this purpose remains a constant; this is also true for the basis of diagnostic and controlled systems for immunotherapy. Ours is an open proposal to use this vision for treatment.

In silico analysis of a major allergen from Rattus norvegicus, Rat n 1, and cross-reactivity with domestic pets

Background: Lipocalins play a role in the cellular trafficking of pheromones and are involved in allergic responses to domestic pets. However, the cross-reactivity among allergens of this group has been poorly explored, and the pheromone linking capacity is not well characterized. The aim of this study was to explore cross-reactive epitopes and pheromone linking capacity among Rat n 1 and homologues in domestic pets through an in silico approach. Methods: ElliPro and BepiPred in silico tools were used to predict B cell linear and cross-reactive epitopes. The pheromone linking capacity was explored by docking virtual screening with 2-ethylhexanol, 2,5-dimethylpyrazine, 2-sec-butyl-4,5-dihydrothiazole, and 2-heptanone ligands. Results: According to the analysis, Rat n 1 shares 52% identity with Equ c 1, Can f 6, Fel d 4, and Mus m 1 allergens. The overlapping structures analysis  revealed high structural homology (root mean square deviation < 1). Four lineal and three discontinuous epitopes were predicted on Ra t n 1. A lineal epitope located between amino acids residues 24 and 36 was highly conserved on all allergens explored. A cross-reactive discontinuous epitope (T142, K143, D144, L145, S146, S147, D148, K152, L170, T171, T173, D174) was also found. Docking molecular simulations revealed the region involved in linking ligands, and we identified the properties of the binding of four pheromones and the binding potential of Rat n 1. Critical residues for interactions are reported in this study. Conclusions: We identified some possible allergens from Rattus norvegicus, and those allergens could have cross-reactivity with allergens from some animals. The results need to be confirmed with in vitro studies and could be utilized to contribute to immunotherapy and reduce allergic diseases related to lipocalins.

Animal lipocalin allergens

Lipocalins represent the most important group of inhalant animal allergens. For some of them, three-dimensional protein structures have been resolved, but their functions are still elusive. Lipocalins generally display a low sequence identity between family members. The characterization of new lipocalin allergens has revealed however that some of them display a high sequence identity to lipocalins from another species. They constitute a new group of potentially cross-reactive molecules which, in addition to serum albumins, may contribute to allergic cross-reactions between animal dander of different species. However, the clinical relevance of cross-reactivity needs to be assessed. Further studies are needed to understand which of these animal lipocalins are the primary allergens and which are cross-reacting molecules. The use of single, well characterized allergens for diagnosis will allow the identification of the sensitizing animal, which is a prerequisite for specific immunotherapy.

Dog saliva - an important source of dog allergens

BACKGROUND

Allergy to dog (Canis familiaris) is a worldwide common cause of asthma and allergic rhinitis. However, dander extract in routine diagnostics is not an optimal predictor of IgE-mediated dog allergy. Our objective was to evaluate saliva as an allergen source for improved diagnostics of allergy to dog.

METHODS

IgE-binding proteins in dog saliva and dander extract were analysed by immunoblot and mass spectrometry (LC-MS/MS) using pooled or individual sera from dog-allergic patients (n = 13). Sera from 59 patients IgE positive to dander and 55 patients IgE negative to dander but with symptoms to dog were analysed for IgE against saliva and dander by ELISA. Basophil stimulation with dog saliva and dander extract was measured by flow cytometry among three dog-allergic patients. Additionally, IgE-binding protein profiles of saliva from different breeds were investigated by immunoblot.

RESULTS

Greater number and diversity of IgE-binding proteins was found in saliva compared to dander extract and varied among dog breeds. In saliva, Can f 1, 2, 3 and 6 were identified but also four new saliva allergen candidates. The majority of the 59 dog dander-positive sera (n = 44) were IgE positive to dog saliva. Among patients IgE negative to dander, but with symptoms to dog, 20% were IgE positive to saliva. The biological activity of saliva was confirmed by basophil degranulation.

CONCLUSIONS

Dog saliva is an allergen source for improved diagnostics of dog allergy. The IgE-binding protein profile of saliva from different dogs varies.

Allergy to rodents: an update

Allergy to rodents in the workplace is an important occupational health problem affecting research, pharmaceutical and toxicological sectors and can have a serious impact on employees working in this area. Despite measures to reduce aeroallergen exposures to rodents in the workplace, there are few signs that this occupational health problem is declining. Rodent allergens are well characterized and exposure-response relationships have been demonstrated to be complex. More recently, the importance of rodent allergens outside of the workplace has been demonstrated in several studies of individuals with asthma. This review focuses on rodent allergy both in the workplace and in the home and examines the complex exposure-response relationships between allergen exposure and sensitization and asthma. Risk factors for rodent allergy and mechanisms of tolerance to rodent allergens are discussed.

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.

Rodent allergens

Rodent allergens play a significant role in the pathogenesis of asthma and allergic rhinitis, and are potent causes of acute and chronic symptoms. This has long been apparent in occupational settings, particularly in the laboratory, but has been most recently studied and found to be important in home environments. These allergens have been suggested as uniquely important among inner-city children with asthma. Furthermore, rodents have become increasingly popular as pets. With recent awareness of significant exposure in a variety of settings, hypersensitivity to rodents has become increasingly important. This review focuses on the importance of rodent allergens, concentrating on mouse and rat, but including other potentially important rodents such as gerbil, hamster, and rabbit. It also discusses the pathogenesis, diagnosis, prevention, and management of rodent allergy.