Wheat is one of the major crops grown, processed and consumed by humankind and is associated with both intolerances (notably coeliac disease) and allergies. Two types of allergy are particularly well characterized. The first is bakers' asthma, which results from the inhalation of flour and dust during grain processing. Although a number of wheat proteins have been shown to bind IgE from patients with bakers' asthma, there is no doubt a well-characterized group of inhibitors of alpha-amylase (also called chloroform methanol soluble, or CM, proteins) are the major components responsible for this syndrome. The second well-characterized form of allergy to wheat proteins is wheat-dependent exercise-induced anaphylaxis (WDEIA), with the omega(5)-gliadins (part of the gluten protein fraction) being the major group of proteins which are responsible. Other forms of food allergy have also been reported, with the proteins responsible including gluten proteins, CM proteins and non-specific lipid transfer proteins. Processing of wheat and of related cereals (barley and rye, which may contain related allergens) may lead to decreased allergenicity while genetic engineering technology offers opportunities to eliminate allergens by suppressing gene expression.

Allergens to wheat and related cereals

Asthma is a chronic life-threatening disease of worldwide importance. Although allergic asthma and related atopic conditions correlate strongly with immune sensitization to house dust mites, it is unclear why antigens from mites provoke such powerful allergic immune responses. We have characterized the protease activity of Der p I, the group I protease allergen of the house dust mite Dermatophagoides pteronyssinus, and here report that it cleaves the low-affinity immunoglobulin (Ig) E Fc receptor (CD23) from the surface of human B lymphocytes. Der p I selectively cleaves CD23 and has no effect on the expression of any other B cell surface molecules tested. We speculate that this loss of cell surface CD23 from IgE-secreting B cells may promote and enhance IgE immune responses by ablating an important feedback inhibitory mechanism that normally limits IgE synthesis. Furthermore, since soluble CD23 is reported to promote IgE production, fragments of CD23 released by Der p I may directly enhance the synthesis of IgE. alpha 1-Antiprotease, a pulmonary antiprotease, is also shown to inhibit the cleavage of CD23 by Der p I. This may be significant in the etiopathogenesis of asthma, because other indoor pollutants associated with asthma are known to potently inhibit this antiprotease. These data suggest that the proteolytic activity of Der p I, the group I allergen of the house dust mite D. pteronyssinus, is mechanistically linked to the potent allergenicity of house dust mites. Furthermore, inhibition of Der p I by alpha 1-antiprotease suggests a mechanism by which confounding factors, such as tobacco smoke, may act as a risk factor for allergic asthma.

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A major house dust mite allergen disrupts the immunoglobulin E network by selectively cleaving CD23: innate protection by antiproteases

Trichoderma spp. are known to produce enzymes with high xylanolytic activity. Different xylanases and various components of their xylanolytic system have been identified and purified. Some of the xylanases have been characterized extensively with respect to their physicochemical, hydrolytic, and molecular properties. Cellulase-free xylanase preparations have been tested successfully in industrial applications such as the prebleaching of kraft pulps in the pulp and paper industry. Future work on understanding the functional significance of xylanase multiplicity, the mechanisms of xylanase prebleaching, and the structural conformation of xylanases could lead to improved or alternative applications of Trichoderma xylanases.

Trichoderma Xylanases, Their Properties and Application

In recent years, our knowledge ofthe structure of many of the important aeroallergens has increased greatly due to the application of sophisticated molecular biological and protein chemistry techniques. We now know the complete amino acid sequences of more than 50 allergens, and the number of clinically significant allergens remaining to be sequenced is rapidly growing smaller. The data obtained from such studies have been extensively reviewed [1] and they clearly indicate that, from a structural standpoint, allergens are indistinguishable from conventional antigens, and that factors known to contribute to antigenicity per se will apply to allergens entering the respiratory tract. However, it has become apparent too that many allergens demonstrate a range of biochemical activities suggesting these properties may also contribute to immunogenicity [2]. In this article, the available information on the physicochemical characteristics and biochemical properties of many of the individual protein allergens from common aeroallergenic sources such as plants, fungi and bacteria (Tables 1-6), dust mites and insects (Table 7, 8), animals (Tables 6, 9) and birds (Table 10) have been collated.

The biochemistry of common aeroallergens

Baking and food industry workers are exposed to several powdered Aspergillus -derived enzymes with carbohydrate-cleaving activity that are commonly used to enhance baked products. We describe a retrospective study of sensitization to fungal α-amylase and cellulase on bakers. Five bakers in whom respiratory allergy symptoms developed when they were exposed to bread "improvers" that contained fungal α-amylase and cellulase were investigated by in vivo and vitro tests. Type I hypersensitivity to these enzymes was demonstrated in the five patients by means of skin testing, histamine release test, positive reverse enzyme-immunoassay for specific IgE antibodies, and bronchial provocation test response to α-amylase or cellulase or both. Isolated immediate and dual responses to the bronchial challenge tests with these enzymes were observed. Immunoblot analysis with use of a pooled serum identified IgE-binding components in both enzymes. In the reverse-enzyme immunoassay-inhibition assays cross-reactivity between α-amylase and cellulase was not found, but some degree of cross-reactivity between α-amylase and A. oryzae , and between cellulase and A. niger was demonstrated. Four of the patients were also sensitized to cereal flour. Aspergillus -derived enzymes used as flour additives can elicit IgE-mediated respiratory allergy, and this fact has to be considered in the diagnosis and clinical management of bakers' asthma.

https://www.jacionline.org/article/0091-6749(92)90470-M/pdf

Respiratory allergy to Aspergillus-derived enzymes in bakers' asthma.

Modern biotechnical methods have enabled production of many new types of potentially allergenic proteins. Enzymes have long been known to be respiratory allergens, but relatively few cases of skin allergy have been reported. Here we describe four patients who developed occupational allergic respiratory symptoms, three with bronchial asthma and one with allergic rhinitis, caused by cellulase and/or xylanase enzymes. Each patient also had urticarial symptoms after skin contact with these enzymes. In addition, one of the patients had allergic contact dermatitis from cellulase, and one from xylanase. Allergic contact dermatitis was verified by positive patch tests with the enzymes, and the immediate allergy was revealed by skin prick tests, specific IgE determinations (RAST) and RAST-inhibition tests. All patients had positive RASTs to both cellulase and xylanase. In the RAST inhibition test 20 microliters of cellulase brought about a 94% inhibition, indicating the specificity of the RAST. Xylanase (20 microliters, 5% w/v) gave an 92% inhibition of cellulase RAST, indicating cross-reactivity between cellulase and xylanase. Three patients have been able to continue at their previous places of work, but at different worksites. One of the patients requires continuous medication for asthma and had to change her job because of persistent symptoms.

B. Grenquist-Norden

Papers

Allergy from cellulase and xylanase enzymes.

Berulfsallergien durch Cellulase, Xylanase und Alpha-Amylase