Cross-reaction and co-sensitization among related and unrelated allergens in canine intradermal tests

Survey of Sensitization to Common Fungi in an Allergic Dog Population: The Need for Further Focus on Sensitization and Allergy to Fungi in Veterinary Medicine

Most fungal species are commensals and non-pathogenic to plants, humans, or animals. However, several species of the Alternaria, Aspergillus, Trichophyton, and Microsporum genera are common causes of disease, even for immunocompetent individuals. Besides mucosal damage, fungi may contribute to a skin barrier impairment, favoring sensitization and allergy development. A total of 68 allergic dogs were selected from a veterinary dermatology and allergy outpatient consultation for conditions related to both Malassezia overgrowth and other fungal complications. The allergy diagnosis was made through anamnesis and current clinical criteria, with the involved allergenic species being identified by intradermal tests (IDTs) and allergen-specific immunoglobulin E (sIgE) determination in serum. Dermatophagoides farinae, Dactylis glomerata, and Malassezia pachydermatis showed as the higher sensitization species from house dust mites, grass pollen, and fungi, respectively. Significant correlations at p < 0.05 were found between sensitization to Dactylis glomerata and Phleum pratense grass pollens, Dermatophagoides farinae and Dermatophagoides pteronyssinus, Acarus siro, Tyrophagus putrescentiae, and Lepidoglyphus destructor dust/storage mites, and between fungi like Aspergillus mix and Penicillium or Alternaria alternata. A significant correlation was also found between sensitization to the Aspergillus mix and D. farinae, D. pteronyssinus, or A. siro. Rather severe dermatitis was observed when a positive IDT to Malassezia pachydermatis was found, regardless of the detection of circulating sIgE, allowing us to consider the usefulness of both the IDT and the sIgE for a systematic diagnosis of allergy to fungi.

Detection of Serum Allergen-Specific IgE in Atopic Dogs Tested in Northern Italy: Preliminary Study

Canine atopic dermatitis (CAD) is a pruritic allergic skin disease associated with IgE-mediated hypersensitivity. IgE is detected using Serum Allergen-Specific IgE test (SAT) in order to identify allergens. The present study aims to identify the environmental allergens in atopic dogs living in Northern Italy using SAT. The screening SAT (sSAT), using a monoclonal antibody cocktail-based ELISA to identify indoor and outdoor allergens, was performed. In all positive samples, an anti-IgE monoclonal antibody ELISA test was performed to extend panel of allergens. Out of 117 selected dogs, 69 were included in the study; 71% were positive and 29% were negative to sSAT. Among the 49 positive sSAT, 53% were positive for both indoor and outdoor, 38.8% only for indoor, and 8.2% only for outdoor allergens. This is the first study on the frequency of allergens involved in CAD in Italy using SAT. IgE hypersensitivity in atopic dogs of Northern Italy is usually associated with indoor allergens, primarily house dust mites. Among the outdoor allergens, an important role was played by Rumex acetosa. Polysensitization also commonly occurs. Therefore, since the numerous factors affect the IgE positivity in CAD, specific panels for geographical areas should be considered and re-evaluated at time intervals.

Co-reactivity between related and unrelated environmental allergens in equine allergen-specific IgE serology testing in the UK

BACKGROUND

Identification of environmental allergens in horses with allergic disease facilitates allergen avoidance and targeted immunotherapy.

HYPOTHESIS/OBJECTIVES

To evaluate allergenic co-reactivity between 44 environmental allergens.

ANIMALS

Horses with suspected allergic disease (n = 344) whose sera were submitted for environmental allergen testing.

METHODS AND MATERIALS

Allergen-specific IgE serological assays were performed using 44 allergens divided into six taxonomically related groups: house dust/storage mites, moulds, insects, grass, tree and weed pollens. Using pairwise comparisons, odds ratios (ORs) were calculated for each environmental pair to determine if there was increased or decreased likelihood of a positive result for one allergen, given a positive result to another. The OR significance was set (using Holm-Bonferroni correction) at P < 0.00006 for all horses (n = 344) and P < 0.00005 for horses with at least one positive reaction (n = 239). Using one-way ANOVA with Tukey's post hoc tests (significance at P < 0.05), differences in mean log e ORs between three groups, taxonomically related allergens with a statistically significant association (related-associated), related allergens lacking a significant association (related-nonassociated) and unrelated allergens were tested.

RESULTS

Statistically significant associations were found between both related and unrelated allergen pairs, the former being more frequent. For all horses (n = 344) and horses with at least one positive reaction (n = 239), co-reactivity ranged from 100% (grasses) to 0% (moulds). The weeds group was exceptional in having more co-reactions with another group (grasses).

CONCLUSIONS AND CLINICAL IMPORTANCE

Co-reactivity was shown within and between certain related allergen groups. Further studies are required to determine whether this is the result of antigenic cross-reactivity.

Prevalence of positive reactions in intradermal and IgE serological allergy tests in dogs from South Australia, and the subsequent outcome of allergen-specific immunotherapy

OBJECTIVE

To determine the prevalence of positive allergen reactions in intradermal and IgE serological tests in dogs presenting to a dermatology referral centre in South Australia and the clinical efficacy of subsequent allergen-specific immunotherapy.

DESIGN

Retrospective study.

METHODS

Results from 108 intradermal allergy tests, 25 IgE serological assays and immunotherapy outcomes in 37 dogs were retrospectively analysed. Immunotherapy outcomes were determined as excellent, good, modest or failure using a global assessment of efficacy matrix which incorporated pruritus scores, lesion severity, medication requirements, and owner and clinician opinion.

RESULTS

The most common positive reactions in intradermal allergy tests were Red clover (59%), Dermatophagoides farinae (29%), Tyrophagus putrescentiae (28%), Yellow dock (25%) and Malassezia pachydermatis (24%). In the IgE serological tests, Yorkshire fog grass (40%), Yellow dock (36%), Kentucky bluegrass (36%) and T. putrescentiae (36%) were the most commonly reported positive results. The outcome of allergen-specific immunotherapy was judged to be excellent in 20% of dogs, good in 15%, modest in 18% and a failure in 47%.

CONCLUSION

As has been reported in other geographical areas, environmental mites and plant pollens frequently gave positive reactions in allergy tests in South Australia. However, the prevalence of individual allergen reactions differed between intradermal and IgE serological tests, with M. pachydermatis being identified as a common cause of hypersensitivity in intradermal tests but not in IgE serological assays. Immunotherapy was judged to be a beneficial treatment in 35% of dogs but was essentially unsuccessful in 65%.

Longitudinal evaluation of immunological responses to allergen-specific immunotherapy in horses with IgE associated dermatological disease, a pilot study

BACKGROUND

The long-term effects of allergen specific immunotherapy (ASIT) on concentrations of circulating immunoglobulin E (IgE) and immunoglobulin G (IgG) in horses have not been reported.

OBJECTIVES

To document changes in clinical severity of horses with atopic dermatitis (AD) and to monitor allergen-specific IgE and IgG concentrations during a two-year course of ASIT.

ANIMALS

Nineteen client-owned horses with a conditional diagnosis of AD.

METHODS AND MATERIALS

Three ASIT groups were randomly assigned based upon results obtained by either intradermal testing (IDT) for regional allergens (n = 7); enzyme-linked immunosorbent assay (ELISA) for specific IgE (n = 6); or a composite of results from both tests (n = 6). Serum concentrations of IgE and IgG specific for allergens included in ASIT were measured at time zero and at four-month intervals. A visual analog scale (VAS) was used to record severity of clinical signs at times zero, 12 and 24 months.

RESULTS

Positive correlations were documented between IgE and both immediate and delayed IDT results (P < 0.00001), and between immediate IDT and IgG results (P = 0.003). Specific IgE in sera decreased significantly (P < 0.05) for allergens that were included in ASIT, whereas IgG increased. Across all horses, the mean VAS score decreased by 1.2 units [95% CI: 1.28, 1.14; (P < 0.0001)] during each 12-month period of ASIT therapy. Improvement in clinical signs was noted in 76.5% of the horses following 12 months of ASIT and in 82% after 24 months on ASIT.

CONCLUSIONS AND CLINICAL IMPORTANCE

In this pilot study, ASIT in horses with AD provided significant clinical benefit associated with a concomitant reduction of allergen-specific IgE and elevation of IgG.

Effectiveness of regionally-specific immunotherapy for the management of canine atopic dermatitis

Background

Canine atopic dermatitis is a common pruritic skin disease often treated with allergen immunotherapy (AIT). AIT in dogs traditionally begins with attempting to identify clinically relevant environmental allergens. Current allergen testing methodologies and immunotherapy techniques in dogs are not standardized. Immunotherapy with a mixture of allergenic extracts selected based on regional aerobiology rather than intradermal tests or serum IgE assays has been described. The objective of this study was to evaluate the effectiveness of regionally-specific immunotherapy in dogs with atopic dermatitis. The medical records of a veterinary dermatology referral clinic were searched for dogs with atopic dermatitis that began regionally-specific subcutaneous immunotherapy from June, 2010 to May, 2013. An overall assessment of treatment effectiveness (excellent, good, fair, or poor) was assigned based upon changes in pruritus severity, lesion severity, and the reduction in concurrent medication(s) during a follow-up period of at least 270 days. Baseline characteristics that might predict treatment success were analyzed with the Spearman’s correlation and the Kruskal-Wallis tests.

Results

Of the 286 dogs that began regionally-specific immunotherapy (RESPIT) during a 3 year period, 103 met the inclusion criteria. The overall response to RESPIT was classified as excellent in 19%, good in 38%, fair in 25%, and poor in 18% of dogs. The response classification correlated significantly with a reduction in pruritus severity (r = 0.72, p < 0.001) and lesion severity (r = 0.54, p < 0.001), but not with the dogs’ baseline characteristics. Adverse reactions were reported in 7/286 (2.4%) of treated dogs.

Conclusions

Under the conditions of this study, RESPIT was safe and effective for the treatment of atopic dermatitis in dogs.

Allergens in veterinary medicine

Allergic diseases in animals are increasingly gaining importance in veterinary practice and as research models. For intradermal testing and allergen immunotherapy, a good knowledge of relevant allergens for the individual species is of great importance. Currently, the knowledge about relevant veterinary allergens is based on sensitization rates identified by intradermal testing or serum testing for allergen-specific IgE; crude extracts are the basis for most evaluations. Only a few studies provide evidence about the molecular structure of (particularly) dust mite, insect and mould allergens in dogs and horses, respectively. In those species, some major allergens differ from those in humans. This position paper summarizes the current knowledge about relevant allergens in dogs, cats and horses.

Sensitization study of dogs with atopic dermatitis in the central region of Rio Grande do Sul

Canine atopic dermatitis (CAD) is a common dermatosis, defined as a genetic-related disease which predisposes to skin inflammation and pruritus, associated to a IgE-specific response in most of cases. Clinical diagnosis may be later complemented by skin allergy and/or serological tests. The aim of these tests is to identify possible allergens in order to enable the clinicians to select candidate antigens for allergen specific immunotherapy. In the present study 58 CAD positive animals were tested. All were submitted to the intradermal test (IDT) and screened for the presence of antibodies against different antigens using ELISA. The obtained results show a high prevalence of sensitization among the tested dogs to house dust mites and to pollen ofC. dactylon. With this work it was possible to identify the main allergens involved in immunological response of dogs with CAD living in central area of Rio Grande do Sul.

Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification

BACKGROUND

Canine atopic dermatitis (AD) is a common, genetically predisposed, inflammatory and pruritic skin disease. The variation in clinical presentations, due to genetic factors, extent of the lesions, stage of the disease, secondary infections, as well as resemblance to other non-atopic related skin diseases, can complicate a diagnosis of canine AD. A sub-group of the International Committee for Allergic Diseases in Animals (ICADA) was tasked with the development of a set of practical guidelines that can be used to assist practitioners and researchers in the diagnosis of canine AD. Online citation databases and abstracts from international meetings were searched for publications related to the topic, and combined with expert opinion where necessary. The final set of guidelines was approved by the entire ICADA committee.

RESULTS

A total of 81 publications relevant for this review were identified. The guidelines generated focus on three aspects of the diagnostic approach: 1. Ruling out of other skin conditions with clinical signs resembling, or overlapping with canine AD. 2. Detailed interpretation of the historical and clinical features of patients affected by canine AD. 3. Allergy testing by intradermal versus allergen-specific IgE serum testing.

CONCLUSIONS

The diagnosis of canine AD is based on meeting clinical criteria and ruling out other possible causes with similar clinical signs. Flea combing, skin scraping and cytology should be performed, where necessary, as part of a thorough work-up. Elimination diet trials are required for patients with perennial pruritus and/or concurrent gastrointestinal signs. Once a clinical diagnosis of canine AD is made, allergy testing can be performed to identify potential causative allergens for allergen-specific immunotherapy.

Pollen Allergies in Humans and their Dogs, Cats and Horses: Differences and Similarities

Both humans and their most important domestic animals harbor IgE and a similar IgE receptor repertoire and expression pattern. The same cell types are also involved in the triggering or regulation of allergies, such as mast cells, eosinophils or T-regulatory cells. Translational clinical studies in domestic animals could therefore help cure animal allergies and at the same time gather knowledge relevant to human patients. Dogs, cats and horses may spontaneously and to different extents develop immediate type symptoms to pollen allergens. The skin, nasal and bronchial reactions, as well as chronic skin lesions due to pollen are in principle comparable to human patients. Pollen of various species most often causes allergic rhinitis in human patients, whereas in dogs it elicits predominantly eczematous lesions (canine atopic dermatitis), in horses recurrent airway obstruction or hives as well as pruritic dermatitis, and in cats bronchial asthma and so-called cutaneous reactive patterns (eosinophilic granuloma complex, head and neck pruritus, symmetric self-induced alopecia). In human allergy-specific IgE detection, skin tests or other allergen provocation tests should be completed. In contrast, in animals IgE and dermal tests are regarded as equally important and may even replace each other. However, for practical and economic reasons intradermal tests are most commonly performed in a specialized practice. As in humans, in dogs, cats and horses allergen immunotherapy leads to significant improvement of the clinical symptoms. The collected evidence suggests that canines, felines and equines, with their spontaneous allergies, are attractive model patients for translational studies.

Agreement between allergen-specific IgE assays and ensuing immunotherapy recommendations from four commercial laboratories in the USA

BACKGROUND

Canine allergen-specific IgE assays in the USA are not subjected to an independent laboratory reliability monitoring programme.

HYPOTHESIS/OBJECTIVES

The aim of this study was to evaluate the agreement of diagnostic results and treatment recommendations of four serum IgE assays commercially available in the USA.

METHODS

Replicate serum samples from 10 atopic dogs were submitted to each of four laboratories for allergen-specific IgE assays (ACTT(®) , VARL Liquid Gold, ALLERCEPT(®) and Greer(®) Aller-g-complete(®) ). The interlaboratory agreement of standard, regional panels and ensuing treatment recommendations were analysed with the kappa statistic (κ) to account for agreement that might occur merely by chance. Six comparisons of pairs of laboratories and overall agreement among laboratories were analysed for ungrouped allergens (as tested) and also with allergens grouped according to reported cross-reactivity and taxonomy.

RESULTS

The overall chance-corrected agreement of the positive/negative test results for ungrouped and grouped allergens was slight (κ = 0.14 and 0.13, respectively). Subset analysis of the laboratory pair with the highest level of diagnostic agreement (κ = 0.36) found slight agreement (κ = 0.13) for ungrouped plants and fungi, but substantial agreement (κ = 0.71) for ungrouped mites. The overall agreement of the treatment recommendations was slight (κ = 0.11). Altogether, 85.1% of ungrouped allergen treatment recommendations were unique to one laboratory or another.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our study indicated that the choice of IgE assay may have a major influence on the positive/negative results and ensuing treatment recommendations.