Les allergènes de l’arachide et des fruits à coque

The foods contain several hundreds of proteins for which only a small number, called allergens, is responsible for allergic reactions. The edible tree nuts (almond, walnut, cashew, Brazil nut, macadamia nut, pecan, Nangai nut, pistachio, pine nut, chestnut and coconut) consist of approximately, 15% of proteins. The objective of this review is to present, from a biochemical point of view, the allergens of these nuts known at the present time and to discuss what this type of information can bring in the comprehension of the mechanisms of cross reaction.     

Allergènes alimentaires croisant avec les allergènes des pollens

The range of pollen-food cross-reactions has increased over the past decade, the clinical pictures are more clear with respect to the allergens concerned, and the molecular basis for some of them have been determined. Diagnostic methods include skin tests, assays for specific IgE, and open and double blind oral provocation tests. Investigation of allergic cross-reactions, first based solely on immunological inhibition techniques using natural allergen extracts, have benefited from molecular biology. Many allergens homologous with pollen allergens have been sequenced and the three dimensional structure of Pru av 1 has been determined, allowing studies on a sub-molecular scale. Allergen cross-reactions between pollen and food, for which the clinical relevance is well established, involve allergens of the Bet v 1 and Bet v 2 families. These allergens are present in numerous edible fruits and vegetables. Identity with the Bet v 1 sequence varies from 38 to 67%, being closest for the profilins (70-80%). Cross sensitization with Bet v 1 and profilins, although particularly frequent, may be silent clinically. Other candidate molecules involved in cross-reactions between pollen and food allergens are Bet v 6, a minor birch allergen, the lipotransferases found in some of the compositae, and the 1,3-β-glucanases corresponding to a major olive allergen. The significance of the detection of specific IgE directed against carbohydrate determinants remains to be investigated. A major problem for the clinician is the absence of clinical significance of cross-reactivity that has been demonstrated in vitro and in vivo.     

Les recombinants des panallergènes polliniques : application à l’interprétation des polysensibilisations

Multiple pollen sensitization is frequently encountered in patients who present with seasonal allergic respiratory symptoms. This regularly leads the allergist to question the significance of skin and laboratory test results because such results make it difficult to differentiate between cross-reactions and co-sensitization. Assays for specific IgE with recombinant panallergens, such as those in the profilin or polcalcin families, the results of which are now available in clinical practice, may lead to a better interpretation of such cases.     

Les allergènes du grain de blé

Wheat is a major dietary cereal, which can cause respiratory, contact and food allergies. Wheat grain contains a large panel of proteins with very particular structures and functions. This review will consider diverse wheat grain proteins and summarize recent work on wheat grain allergens.     

Caractéristiques non allergéniques des allergènes

Allergens are capable of inducing specific IgE production and are recognized by IgE-receptor bearing cells, more particularly mast cells and basophils expressing Fc?RI, the high affinity IgE receptor. However, they are also capable of directly stimulating certain cells of the bronchial mucosa, especially in a protease-dependent way. For example, many allergens such as those from house dust mites (Dermatophagoides pteronyssinus et Dermatophagoides farinae) have protease activity which is involved in the activation of bronchial epithelial cells, dendritic cells, T lymphocytes, B cells, eosinophils and airway smooth muscle cells. Overall, these activations amplify Th2 polarization, recruitment and activation of inflammatory cells, and airway smooth muscle cell contraction. Receptors such as the protease-activated receptor (PAR) have been involved in these functions. PAR-2, which has a role in protease-dependent activation by many allergens, is over-expressed in bronchial biopsies from asthmatic patients. Both phenomena may be involved in the development and amplification of allergic asthma.     

Intérêt des allergènes recombinants pour la prise en charge de patients allergiques : cas cliniques

Allergen extracts used in diagnosis by clinicians are manufactured from crude source materials. These extracts contain a number of allergenic proteins and their composition can vary. The employment of molecular biological methods in the field of allergy has led to the production of recombinant allergens from a variety of sources. Their use has allowed us to improve our understanding of allergenic proteins, to define families of allergens, to explain allergenic cross-reactions, and to show that pollen sensitivity profiles vary as a function of the geographic region in which individuals live. As a result, in the 21st century reasoning on the molecular scale should be included in patient management. In 2005, the clinician has at his disposal the level of specific IgE with 27 recombinant allergens from 7 different allergenic sources. The use of these materials can, in certain cases, allow us to have a more precise diagnosis and to orient the therapeutic decision more accurately. Three observations made in our consultation service are described to illustrate the contribution of these new diagnostic methods.     

Quoi de neuf en allergologie pédiatrique en 2006–2007 ?: Partie 1 : épidémiologie,diagnostic précoce et prévention. (Une revue de la littérature internationale d’octobre 2005 à septembre 2007)

A very large number of epidemiological studies on allergy and/or asthma in children have been published during the two last years. Some of these studies have been performed in a low number of highly selected children. Other studies are multicenter and multinational studies performed in very large numbers of children, adolescents and young adults. Major risk factors are familial history of allergy and/or asthma, early childhood eczema and/or sensitizations, and passive smoking during pregnancy and early life. The risk for atopy and/or asthma is decreased in rural children, especially farm children, and in children living in anthroposophic families, except for children living near swine feeding farmings. However risk and « preventive » factors do not work equally in all children, and their effects are modulated by complex interactions with other genetic and/or environmental factors. The results of epidemiological studies should be interpreted with caution, since they may be affected by a « prudent lifestyle » in atopic and atopy-prone families, leading to eviction of passive smoking, prolonged maternal breast-feeding, delayed introduction of solid foods, and eviction of pets. Epidemiological studies should also take into account the parental understanding of allergy and wheeze, which is affected by educational and socioeconomical level and ethnic origin, and its impact on allergy and asthma prevalence estimates. Finally, the « programmed death » of the « allergy and asthma epidemics » is probably a reality in most developed countries, but the prevalence of allergy and asthma is still increasing in developing countries.     

Épidémiologie de la plainte allergique en médecine générale

Allergic conditions account for a large proportion of chronic diseases. Here, the presenting complaints of patients with allergic diseases seen in consultation with three general practitioners are compared with published epidemiologic data. Questionnaires from 346 patients (mean age 36.3 years, 213 women:133 men) were available for analysis. There was no statistically significant difference between the allergy as seen by the patients and that observed by the doctor (28.9% versus 35.3%, P = 0.09). Seventy-six percent of the allergic patients said that they had previously consulted their generalist for this problem. Forty-two percent reported a positive family history of allergy (63% of the allergic patients versus 33.3% of the nonallergic patients, P < 0.001). Allergic rhinitis was the most frequent complaint, reported by 19.8% of the patients, followed by conjunctivitis (14.4%), eczema (11.9%), asthma (7.6%), urticaria (5.8%), and angioedema (3.2%). For each of these complaints, the doctor's evaluation was practically identical. Food allergy, all complaints included, was claimed by 4% of the patients but food allergy was recognized by only 0.3% of the doctors. Drug allergy was reported by 10.8% of the patients and recognized as such by 7.8% of the doctors. In conclusion, the results of this study on allergic complaints reported by patients seen in general practice demonstrate no overvaluation of these complaints by the patients. These results are difficult to compare with published data, which are disparate.     

Épidémiologie de l’allergie alimentaire

The epidemiology of food allergy normally relies on surveys using questionnaire in general populations and studies on cohorts and through professionals in allergy clinics, sometimes completed by prick-tests, specific IgE assays and/or oral challenges. Complementary data are supplied by specialized medical networks. In European countries, the prevalence of food allergy in the pediatric population is about 4.7%, and in adults it is about 3.2%. Striking disparities characterize the response to questionnaires in EU countries. Life-threatening anaphylaxis occurs in 1/10,000 inhabitants, fatal anaphylaxis in 1/1 million inhabitants. A drastic increase of life-threatening and lethal anaphylaxis has been noted in the UK and Australia over the past ten years. In France, there has been an increase of 28% between 2001 and 2006. The Allergy Vigilance Network, which includes 400 allergists, reports that this increase has occurred in the pediatric population. The prevalence of food allergies depends on age and consuming habits. Milk, egg, peanut and tree-nuts are at the top of the list in children. Prunoïdeae, latex-group fruits, Apiaceae, wheat and tree-nuts are the most important food allergens in adults. Peanut and tree nuts are the main offending allergens in severe anaphylactic cases. Since 2002 the Allergy Vigilance Network in France and Belgium has been identifying newly-appearing dangerous allergens. Molluscs, lupine flour and cashew nuts are the most common on this list and labelling these foods is now compulsory. Goat and sheep milk proteins (14 cases), buckwheat (25 cases) and wheat isolates are not yet required to be labelled. The danger of anaphylaxis to goat and sheep proteins (two deaths out of 14 cases) is due to the likelihood of their being masked allergens, for which reason the EU Scientific Agency should be made aware of the necessity of required labelling of foods containing these substances.     

Les allergènes croisants à l'échelle moléculaire : comparaison nord-sud

Fruit of the Rosaceae family, in particular apples and peachs, are frequent causes of food allergy. The clinical manifestations of these allergies differ as a function of geographic location. In the context of the SAFE project (QLK1-CT-2000-01394), financed by the European Community, the apple has been chosen as a model for the study of the relationship between the clinical presentation and the profile of sensitivity to Rosaceae allergens. This study included 389 patients allergic to apples and who live in four European regions: the Netherlands (Utrecht), Austria (Vienna), northern Italy (Milan) and central Spain (Madrid). Two different profiles of apple allergy were found in Europe: one in the Netherlands, Austria and in most of the patients (90%) in northern Italy, the other in Spain and in a minority (10%) of the Italians patients. Patients coming from regions where birch pollen is present become allergic to this pollen and to its major allergen Bet v 1 through contact via the respiratory tract; allergy to apple begins later as a consequence of cross-reactivity between Bet v 1 and Mal d 1. In Spain, allergy to apple is a result of primary sensitization to peach and its major allergen Pru p 3, subsequent allergy to apple being the consequence of cross-reactivity between lipid transfer proteins Pru p 3 and Mal d 3.     

Quel est le profil d’un asthme sévère chez l’enfant ?

Severe asthma is estimated to occur in 9.6% of asthmatics. Even though severe asthma does not occur frequently in asthmatic children, still it accounts for 80% of health expenditures in this group of patients. International guidelines grade the severity of asthma in four stages (intermittent, mild persistent, moderate, severe) according to daytime and night time symptoms, the frequency of exacerbations that affect the patient's activities, and the forced expiratory volume in the first second (FEV₁) before starting treatment. This classification appears insufficient for an evaluation of the severity of asthma in children because it does not take into account their current treatment, namely, inhaled corticoids, as well as previous acute severe exacerbations, the condition of the lower airways, the existence of an atopic terrain, and the importance of the patient's age and sex on the severity of the asthma. Finally, it must be remembered that in the clinical workup of a child with severe asthma, it is first of all necessary to rule out “false asthma” (by systematic etiologic investigation), to distinguish between severe asthma and poorly controlled asthma related to co-existing conditions not otherwise considered, an inadequate environment, and poor adherence to prescribed therapy.