Organ‐specific allergen challenges in airway allergy: current utilities and future directions

Atopy has been long used as the screening method for airway allergy. Nevertheless, aeroallergens can trigger respiratory symptoms not only in atopic patients (atopic respiratory allergy, ARA), but also in non-atopic subjects (local respiratory allergy, LRA). Moreover, ARA and LRA can coexist in the same patient, and this clinical scenario has been called dual respiratory allergy (DRA). When the clinical history cannot determine the relevance of sensitizations in ARA patients, nasal, conjunctival or bronchial allergen challenges (NAC, CAC, and BAC, respectively) should be conducted. Moreover, these tests are required to identify patients with LRA and DRA. The clarification of the allergic triggers of airway diseases has a profound impact on the management strategies the patients can be offered. Importantly, allergen immunotherapy (AIT) remains as the only disease-modifying intervention for ARA. Recent data indicate that AIT might have a similar effect on LRA patients. Nevertheless, AIT success relies largely on the correct phenotyping of allergic individuals, and NAC, CAC, and BAC are very helpful tools in this regard. In this review, we will summarize the main indications and methodology of CAC, NAC, and BAC. Importantly, the clinical implementation of these tests might translate into precision medicine approaches and better health outcomes for patients with airway allergy.

An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen

Background

Cats are the major source of indoor inhalant allergens after house dust mites. The global incidence of cat allergies is rising sharply, posing a major public health problem. Ten cat allergens have been identified. The major allergen responsible for symptoms is Fel d 1, a secretoglobin and not a lipocalin, making the cat a special case among mammals.

Main body

Given its clinical predominance, it is essential to have a good knowledge of this allergenic fraction, including its basic structure, to understand the new exciting diagnostic and therapeutic applications currently in development. The recent arrival of the component-resolved diagnosis, which uses molecular allergens, represents a unique opportunity to improve our understanding of the disease. Recombinant Fel d 1 is now available for in vitro diagnosis by the anti-Fel d 1 specific IgE assay. The first part of the review will seek to describe the recent advances related to Fel d 1 in terms of positive diagnosis and assessment of disease severity. In daily practice, anti-Fel d 1 IgE tend to replace those directed against the overall extract but is this attitude justified? We will look at the most recent arguments to try to answer this question. In parallel, a second revolution is taking place thanks to molecular engineering, which has allowed the development of various forms of recombinant Fel d 1 and which seeks to modify the immunomodulatory properties of the molecule and thus the clinical history of the disease via various modalities of anti-Fel d 1-specific immunotherapy. We will endeavor to give a clear and practical overview of all these trends.

An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen

Background

Cats are the major source of indoor inhalant allergens after house dust mites. The global incidence of cat allergies is rising sharply, posing a major public health problem. Ten cat allergens have been identified. The major allergen responsible for symptoms is Fel d 1, a secretoglobin and not a lipocalin, making the cat a special case among mammals.

Main body

Given its clinical predominance, it is essential to have a good knowledge of this allergenic fraction, including its basic structure, to understand the new exciting diagnostic and therapeutic applications currently in development. The recent arrival of the component-resolved diagnosis, which uses molecular allergens, represents a unique opportunity to improve our understanding of the disease. Recombinant Fel d 1 is now available for in vitro diagnosis by the anti-Fel d 1 specific IgE assay. The first part of the review will seek to describe the recent advances related to Fel d 1 in terms of positive diagnosis and assessment of disease severity. In daily practice, anti-Fel d 1 IgE tend to replace those directed against the overall extract but is this attitude justified? We will look at the most recent arguments to try to answer this question. In parallel, a second revolution is taking place thanks to molecular engineering, which has allowed the development of various forms of recombinant Fel d 1 and which seeks to modify the immunomodulatory properties of the molecule and thus the clinical history of the disease via various modalities of anti-Fel d 1-specific immunotherapy. We will endeavor to give a clear and practical overview of all these trends.

EAACI Guidelines on Allergen Immunotherapy: Allergic rhinoconjunctivitis

Allergic rhinoconjunctivitis (AR) is an allergic disorder of the nose and eyes affecting about a fifth of the general population. Symptoms of AR can be controlled with allergen avoidance measures and pharmacotherapy. However, many patients continue to have ongoing symptoms and an impaired quality of life; pharmacotherapy may also induce some side-effects. Allergen immunotherapy (AIT) represents the only currently available treatment that targets the underlying pathophysiology, and it may have a disease-modifying effect. Either the subcutaneous (SCIT) or sublingual (SLIT) routes may be used. This Guideline has been prepared by the European Academy of Allergy and Clinical Immunology's (EAACI) Taskforce on AIT for AR and is part of the EAACI presidential project "EAACI Guidelines on Allergen Immunotherapy." It aims to provide evidence-based clinical recommendations and has been informed by a formal systematic review and meta-analysis. Its generation has followed the Appraisal of Guidelines for Research and Evaluation (AGREE II) approach. The process included involvement of the full range of stakeholders. In general, broad evidence for the clinical efficacy of AIT for AR exists but a product-specific evaluation of evidence is recommended. In general, SCIT and SLIT are recommended for both seasonal and perennial AR for its short-term benefit. The strongest evidence for long-term benefit is documented for grass AIT (especially for the grass tablets) where long-term benefit is seen. To achieve long-term efficacy, it is recommended that a minimum of 3 years of therapy is used. Many gaps in the evidence base exist, particularly around long-term benefit and use in children.

Diagnostic tools in ocular allergy

Ocular allergy (OA) includes a group of common and less frequent hypersensitivity disorders frequently misdiagnosed and not properly managed. The diagnosis of OA is usually based on clinical history and signs and symptoms, with the support of in vivo and in vitro tests when identification of the specific allergen is required. To date, no specific test is available for the diagnosis of the whole spectrum of the different forms of OA. The lack of recommendations on diagnosis of OA is considered a medical need not only for allergists but also for ophthalmologists. This position paper aims to provide a comprehensive overview of the currently available tools for diagnosing OA to promote a common nomenclature and procedures to be used by different specialists. Questionnaires, sign and symptom grading scales, tests, and potential biomarkers for OA are reviewed. We also identified several unmet needs in the diagnostic tools to generate interest, increase understanding, and inspire further investigations. Tools, recommendations, and algorithms for the diagnosis of OA are proposed for use by both allergists and ophthalmologists. Several unmet needs in the diagnostic tools should be further improved by specific clinical research in OA.

Ocular allergy: recognizing and diagnosing hypersensitivity disorders of the ocular surface

Ocular allergy includes several clinically different conditions that can be considered as hypersensitivity disorders of the ocular surface. The classification of these conditions is complex, and their epidemiology has not been adequately studied because of the lack of unequivocal nomenclature. Ocular allergy symptoms are often, but not always, associated with other allergic manifestations, mostly rhinitis. However, specific ocular allergic diseases need to be recognized and managed by a team that includes both an ophthalmologist and an allergist. The diagnosis of ocular allergy is usually based on clinical history and signs and symptoms, with the support of in vivo and in vitro tests when the identification of the specific allergic sensitization is required for patient management. The aims of this Task Force Report are (i) to unify the nomenclature and classification of ocular allergy, by combining the ophthalmology and allergy Allergic Rhinitis and its Impact on Asthma criteria; (ii) to describe current methods of diagnosis; (iii) to summarize the therapeutic options for the management of ocular allergic inflammation.

Oral food challenge in children: an expert review

Oral food challenges are indicated for the diagnosis of food allergy and the double-blind, placebo-controlled oral food challenge is considered the gold standard diagnostic method in children with suspected food allergy. This practice parameter for oral food challenges in children was prepared by a workgroup at the request of the French Society for Allergology and Clinical Immunology (SFAIC) and the French Paediatric Society for Allergology and Pulmonology (SP2A). We aimed to develop practical guidelines for oral food challenges in children for the diagnosis of suspected food allergy or the evaluation of food tolerance. We also considered the safety measures to be implemented during testing and management of the potentially serious allergic reactions that may arise during the test. The strength of the recommendations was established, using the GRADE evidence-based approach. We considered four issues: (1) the selection of children for oral food challenges (indications and contraindications); (2) the procedure used (material, where the test should be carried out, technique and management of reactions); (3) interpretation of the test and (4) consequences of the test.

Le test de provocation conjonctival : recommandations pratiques pour le diagnostic des conjonctivites allergiques

The diagnosis of ocular allergy, which has become a real public health problem occurring in 25% of the general population and continues to rise, requires allergic testing. Skin and blood tests combined with interviewing the patient demonstrate sensitivity to one or more antigens. However, while allergic testing and interviews generally reveal the cause of the symptoms, only the conjunctival provocation test (CPT) provides clear evidence of a functional relation between the conjunctival pathology and exposure to the antigen. Since there is still no validated consensus regarding the criteria for positivity of the CPT in routine practice, the working group attempted to establish the major guidelines for conducting the test, to standardize approaches and pinpoint areas of uncertainty. The group established a consensus regarding the conditions for using the test (patient selection, allergens to be tested, usable concentrations, the test protocol, the signs and symptoms to be assessed, interpretation of results, follow-up) and identified two distinct patient groups (outpatients and hospitalized patients) in whom test-taking conditions are different. The outpatient group includes patients suffering from benign forms of conjunctivitis (acute, seasonal, or chronic) and those sensitive to the usual allergens (mainly domestic and airborne). In these cases, the test is given in a medical setting with an allergologist or an ophthalmologist who instills the drops relatively rapidly. The criterion for positivity is the extent of the pruritus. On the other hand, in the hospital population, which is composed of patients suffering from vernal conjunctivitis, the attempt to establish the triggering factor requires a more elaborate protocol carried out in an ophthalmologic setting and based on the association of a range of clinical and biological factors. The deliberations of the working group should lead to the standardization of the CPT procedure for diagnostic purposes.

High magnesium concentration in vitro decreases human leukocyte activation

In view of experimental data suggesting that pharmacological magnesium (Mg) therapy could be expected to temper hypersensitivity, the aim of the present study was to assess the effect of in vitro high Mg concentration (8 mmol/l vs. 0.8 mmol/l) on human leukocyte activation. The first experiment in nine healthy volunteers was performed on total leukocyte suspension containing 82 +/- 4 per cent of neutrophils. The results demonstrate the inhibitory effect of high Mg concentration as shown by the significant reduction of superoxide anion production following phorbol myristate acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (fMLP) activation. Moreover, neutrophils activated with fMLP showed an increased respiratory burst when incubated in low Mg concentration (0.2 mmol/l) as compared to normal Mg concentration (0.8 mmol/l). Similarly, high concentration of Mg resulted in a significant reduction in superoxide anion production by eosinophils in response to PMA in five eosinophilic patients. In patients showing Hymenoptera venom hypersensitivity, high Mg concentration resulted in a significant reduction of sulphidoleukotrienes production by leukocytes in response to venom allergen (six patients) or in response to zymosan activated particules (fourteen patients). Taken together, the results suggests that Mg acts via a non specific mechanism and appears to be non specific to a particular cell type. As Mg counteracts calcium in many physiological and pathological processes, it is reasonable to hypothesise that extracellular Mg can diminish leukocyte activation by its calcium antagonism.

Atopy parameters in asthmatic infants

We evaluated various atopy parameters in 44 asthmatic infants aged 1-3 years: nonspecific parameters (total IgE and eosinophilia), and specific parameters relative to 21 allergens (specific IgE and skin tests), together with tests of leukotriene release by blood leukocytes (cellular allergen stimulation test; CAST) in the presence of a mixture of 21 allergens. Thus far 17 infants have displayed no sign of atopy, but 27 met at least one criterion. Eight met nonspecific criteria, and the others single or multiple criteria. Of the 21 allergens, 20 gave rise to at least one sensitization in this population. The specific IgE was more frequently positive than the skin tests. Dissociations between the two types of specific tests were practically systematic. Different phenotypes based on the chosen parameters were individualized, demonstrating heterogeneity in the expression of atopy in these young infants. The polyvalent CAST was positive only when other criteria of atopy were also positive (specific IgE and/or skin tests), and the range of intensity of the responses obtained supports reactivity rather than sensitization.

[Vernal keratoconjunctivitis in the child. Clinical and complementary study apropos of 22 cases]

PURPOSE

Vernal kératoconjunctivitis was studied in a population of 22 children aged 3 to 14 years and followed up in an allergy and ophthalmology outpatient clinic. The role of allergy and the severity of inflammation where assessed by a systematic exploration, which combined a detailed allergy evaluation and blood and lacrimal sampling.

MATERIALS AND METHODS

Allergy criteria chosen and recorded in 9 cases are: an increase of total IgE over the higher limit for the age, a positive skin prick test to one allergen, a positive serum specific IgE dosage (> 0.35 IU/mL) of specific IgE. Conjunctival allergy was present in 6 of the 9 children with a positive allergenic provocation test, or with a high local production of total IgE and a lacrimal/serum eosinophilic cationic protein ratio greater than one.

RESULTS

Criteria used for supporting the IgE mediated hypersensitivity diagnosis are discussed: they have to be very strict to eliminate false positive results. Allergen involvement can only be evidenced by a specific provocation test. When evidenced as described, limbic or palpebral conjunctivitis had the same frequency. Lacrimal ICAM 1 levels seemed to be higher (p < 0.05) in the severe limbal forms (24.7 +/- 3 pg/mL) than in the palpebral ones (8.1 +/- 6.5 pg/mL). Interpretation of biological parameters evidencing conjunctival inflammation is more difficult.

CONCLUSION

Allergic involvement in child vernal keratoconjunctivitis can only be assessed through a detailed evaluation, leading to a specialised ophthalmic and allergic management. A specific treatment can then be established, based on allergen eviction and possibly on specific immunotherapy (5 cases). H1 antihistamin treatments are dedicated only to children with a positive allergic evaluation.

[Comparison of specific IgE levels versus various milk proteins in 76 eczematous children]

Among 76 eczematous children, we realized a RAST test for whole milk and milk specific proteins: lactalbumin, lactoglobulin and casein. One of these RAST tests, at least, was positive for 27 children. Whole milk RAST test is the most frequently positive (77%) but some non specific reactions seem to interfere: only three children are clinically milk sensitive. Among specific proteins, lactalbumin is more frequently positive (59%) than lactoglobulin (51%) and casein (18%). Eczematous children with positive milk RAST tests, if compared to other eczematous children, have currently more mite allergies and positive egg RAST tests. They have a tendency (non significative) to be more frequently breast fed. The positivity of milk RAST tests seems to belong to a polysensitization and infrequently concerns a clinical allergy.