The influence of carbohydrate structures present in common allergen sources on specific IgE results.

BACKGROUND: Cross-reactive carbohydrate determinants (CCD) are well known interferants in specific IgE assays (sIgE). Glyco-epitopes are not restricted to CCD and extracts used to prepare in vitro tests contain many other glycoproteins able to bind glycan-specific IgE. The overall amounts of IgE-bindable glycan structures in allergen sources are unknown. OBJECTIVE: We aimed at quantifying the influence of N-glycan structures on IgE reactivity to commonly tested allergen sources. METHODS: IgE reactivity to 51 allergen extracts, one purified natural allergen and 10 recombinant allergens was measured on Phadia UniCAP system using 2 sera demonstrating significant levels of glycan-related IgE reactivity. Immobilized bromelain and horseradish peroxidase (HRP) were used to capture N-glycan-specific IgE from these sera. Residual IgE reactivity was measured for 42 allergen sources and 4 recombinant/purified allergens. RESULTS: An obviously excessive number of positive CAP-results were obtained with both sera, especially for plant-based allergen sources. Capture of glycan-specific IgE led to a decrease of serum IgE ractivity, variable among allergen sources and between sera. Among others, peanut results were proven largely interfered by the presence of glycan-specific IgE. Unexpectedly some allergen sources showed a slight influence of glycan-related reactivity, such as cockroach, mosquito, mussel, shrimp and domestic mites. CONCLUSION: In patients sensitized to pollens or to Hymenoptera venoms sIgE results should be interpreted with caution. One cannot substract the result of a glyco-reporter test (bromelain and/or HRP) in order to compute glycan-free slgE results for common allergen sources like peanuts. As long as the demonstration of a significant role for glycan structures in clinical allergic reactions is lacking, a simple pre-treatment able to discard glycan-specific IgE from serum would be useful to improve accuracy of in vitro diagnostic tests.

IgE-reactive carbohydrate epitopes--classification, cross-reactivity, and clinical impact.

A glycan-related IgE-reactivity has been demonstrated in most allergen sources, especially in plant kingdom. Recent progress in glycobiology has allowed a clearer classification of these glyco-epitopes. Unlike classical peptide chain-based epitopes, glyco-epitopes can share significant structural homologies beyond the limits of protein families. These glycoepitopes are thus prone to extensive cross-reactivity. They have been called Cross-reactive Carbohydrate Determinants or CCD. Many of these glyco-epitopes behave as "panepitopes", leading to cross-reactivity between products as distant as pollens and hymenoptera venoms. But CCD are not universally cross-reactive and they rather cluster into subgroups such as plant CCD or fungal CCD. Because a monovalent IgE-binding is sufficient in serum-based assays, glyco-epitopes and CCD are classically considered as a potential source of positive in vitro results without clinical significance. But some authors recently demonstrated that glyco-epitopes could induce a response at the cell level and suggested that they might play a role in vivo. As long as in vitro assays include glycan- and CCD-related IgE responses, laboratory results should be carefully interpreted in the light of existing knowledge about the glycomes of natural products. IgE-reactivity of the patient's serum can also be tested towards a glycoprotein model such as bromelain.

Transglutaminases: a meeting point for wheat allergy, celiac disease, and food safety.

Wheat is the staple cereal in many countries and its uses in manufactured foods are ever growing due to the technological qualities of gluten proteins. Transglutaminases (TG) are ubiquitous enzymes with many functions. They are able to transform proteins by deamidation and/or transamidation. This last reaction can cross-link proteins together. Intestinal tissue TG has been shown to play an important role in two kinds of immune reactions to wheat: celiac disease and wheat-dependent exercise-induced anaphylaxis. In addition, new epitopes have been suspected in cases of anaphylaxis to wheat isolates, a food ingredient consisting mainly of deamidated gluten proteins. As a microbial TG is included in many food technological processes, its safe use should be checked. This assessment must cover not only the safety of the TG itself but also that of the deamidated/cross-linked proteins generated by this enzyme. This article aims at discussing the possible consequences of using TG in food industry in the light of today knowledge about immune reactions to wheat.

Widening sensitization spectrum through carbohydrate panepitopes--a hypothesis.

Cross-reactive carbohydrate determinants (CCD) differ from classical peptide epitopes because their cross-reactivity is not restricted to a protein family or domain. They can be considered as panepitopes. Antigen presenting cells (APC) express membrane receptors for IgE. APC-bound IgE are able to widen the patient's sensitization spectrum through cross-binding of allergens belonging to the same protein family or domain. In the case of carbohydrate panepitopes the same mechanism could induce a much larger array of new sensitizations than peptide epitopes can do.

[Allergies associated with both food and pollen]. / Les allergies associant pollens et aliments.

Recent progress in understanding structural relationships between allergens has allowed their classification into molecular families. Proteins belonging to a molecular family often show some degree of IgE cross-reactivity. These cross-reactions can lead to a clinical association like birch-apple syndrome whose basis is a sensitization to a PR-10 protein (birch pollen Bet v 1) and then oral symptoms in contact to apple Mal d 1, another PR-10 family member. Food allergens implicated into pollen-food allergy syndromes differ from those linked to crustacea or milk cross-allergies: they seem unable to sensitize the patient through oral route. As a result, they most often induce weaker clinical reactions than complete allergens like those present in shrimp or cow milk. Numerous molecular families have been isolated from pollens. PR-10 and profilins have a well established role in inducing clinical reactions to food like fruits and vegetables. Some molecular families need more studies to delineate their true impact on pollen-driven food reactions: polygalacturonases, pectate lyases, isoflavone reductases, thaumatin-like, cyclophilins.... Others are found in pollen but not in eaten products: 2-EF-hand calcium binding proteins, beta expansins,... Lipid transfer proteins (LTP) are widespread plant food allergens (e.g. in peach): these proteins seem able to directly sensitize the patient through oral route. But recent data have suggested a possible additional effect of some LTP present in pollens (mugwort, olive, pellitory).

Interferences of glycerol, propylene glycol, and other diols in the enzymatic assay of ethylene glycol.

As an alternative to gas chromatography, the enzymatic UV assay of ethylene glycol is often used by emergency laboratories. Many variants of this technique have been published, all based on the reaction between NAD(+) and ethylene glycol in the presence of glycerol dehydrogenase (EC 1.1.1.6). We show that other alpha-diols interfere in this reaction. Some of them, like 2,3-butanediol, give false positive reactions; whereas other diols, e.g. glycerol and propylene glycol, interfere only when ethylene glycol is present in the sample and lower the ethylene glycol response; these interferents are of particular concern because some parenteral drugs used in emergency situations contain glycerol or propylene glycol in their vehicle. This drawback has hitherto been largely underestimated, and we think that ethylene glycol results obtained with these enzymatic techniques should be interpreted with caution, even if the sample is pre-treated with glycerokinase (EC 2.7.1.30); this pre-treatment effectively corrects the glycerol interference but not that of propylene glycol.

Results of the multicenter evaluation of a novel homogeneous immunoassay for digoxin based on the cloned enzyme donor immunoassay technology.

A new CEDIA assay for the measurement of digoxin in serum on random access analyzers was evaluated by twelve laboratories in Europe and the United States. Studies on the analytical range, reproducibility, calibration stability, recovery in controls, interlaboratory comparability, comparability with routine methods, and the effect of various interfering factors have been performed and the results are presented in this paper. The analytical performance was comparable to that of routine methods provided the manual pipetting step for pre-incubation was performed with accurate pipettes. A major advantage of the CEDIA Digoxin assay in terms of convenience is the simple two-point calibration procedure. Moreover, digoxin can be determined within 15 minutes after receiving the samples on random access analyzers like Boehringer Mannheim/Hitachi analysis systems. Thus, the CEDIA Digoxin assay represents an attractive alternative to the measurement of digoxin on dedicated immunochemical assay systems.

Results of the multicenter evaluation of a homogeneous immunoassay for digitoxin based on the cloned enzyme donor immunoassay technology.

We evaluated a CEDIA assay for the determination of digitoxin in serum on random access analyzers. The multicenter evaluation included studies on the analytical range, calibration stability and reproducibility of the new assay. Moreover, recovery in controls, transferability of results obtained in different laboratories, comparability with routine methods, and the effect of various interfering factors have been analyzed. Summarized the analytical performance was comparable to that of routine methods. The CEDIA Digitoxin assay represents an attractive alternative to established digitoxin immunoassays because it can be performed on random access analyzers, thus permitting the simultaneous determination of digitoxin and other serum analytes without sample splitting.

[Bibliography in clinical biochemistry: analysis of the literature beginning with a computerized data bank]. / Bibliographie en biochimie clinique: analyse de la littérature médicale à partir d'une banque de données informatisée.

In which fields of medicine, and in which journals does one publish the majority of articles which concern clinical biochemistry? We are trying to reply to this question by studying the basis of the biographical data developed in our laboratory, proceeding from the perusal of 290 journals and representing 16 802 articles stored from 1978 to 1983. Clinical Chemistry is the most important journal as far as number of articles is concerned, but less articles arises from journals of clinical biochemistry than from those of general medicine and internal medicine. The theme "lipoproteins and atherosclerosis" is the most prolific. It is studied in more detail. In a general way, a theme is rarely covered in a satisfactory manner with 5 journals or less. We think that, faced with the great dispersion of the same theme across the medical literature, our results will help the biologist to make a choice both from the point of view of contract and biographical research.