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Coping with cross-reactive carbohydrate determinants in allergy diagnosis

View Article: PubMed Central - PubMed

ABSTRACT

A relevant proportion of allergy diagnosis is accomplished by in vitro determination of specific immunglobulin E (sIgE) to extracts from suspected allergens. Such extracts inevitably contain glycoproteins, which may react with patients’ IgE. In the case of plant and insect allergens, the relevant epitope structure is an α-1,3-fucose on the Asn-linked sugar residue of so-called N-glycans. Due to their wide distribution, N-glycans carrying this epitope are known as “cross-reactive carbohydrate determinant(s)” (CCD[s]). About 15 years of awareness allow the conclusion that anti-CCD IgE does not cause noticeable clinical symptoms. In consequence, diagnostic results arising from CCD reactivity must be rated as false positives. With up to 30 % of CCD reactive patients, this can be regarded as a serious problem.

Another cross-reactive carbohydrate determinant became notorious as a potential cause of anaphylactic reactions to a recombinant glycoprotein drug carrying α-1,3-galactose. This galactose-containing determinant (GalCD, galactose containing cross-reactive carbohydrate determinant) was supposed as a trigger for delayed allergic reactions to red meat in several cases. Thus, α-1,3-galactose may have clinical relevance in certain cases – possibly as a result of tick bites. Often, however, GalCDs probably cause false-positive results with milk and meat extracts. No clear evidence for the role of other non-human carbohydrate structures such as N-glycolylneuraminic acid as CCD has been presented so far.

Remedies for sIgE based in vitro diagnosis come in the form of non-glycosylated recombinant allergen components or of specific CCD inhibitors. The high potential of recombinant allergens is optimally realized in the context of component resolved diagnosis using allergen arrays with more than 100 components, whereas CCD inhibitors increase the specificity of conventional extract-based diagnosis. Reagents for the detection and inhibition of CCDs from plants and insects have been developed, whereas tools for GalCDs of milk and meat lag behind.

No MeSH data available.


Example of the effect of CCD inhibition. Serum of a 46-year-old male from Carinthia, Austria, was tested with custom made multi-allergen strips (Mediwiss Analytics, Moers, Germany) containing one or three CCD reporter bands. Experimental details can be found in [20]. In the presence of inhibitor only allergens with anamnestic substantiation appeared as positive.
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Fig3: Example of the effect of CCD inhibition. Serum of a 46-year-old male from Carinthia, Austria, was tested with custom made multi-allergen strips (Mediwiss Analytics, Moers, Germany) containing one or three CCD reporter bands. Experimental details can be found in [20]. In the presence of inhibitor only allergens with anamnestic substantiation appeared as positive.

Mentions: An example for a protease treated inhibitor is the “proglycan” CCD-blocker (www.proglycan.com) consisting of bromelain glycopeptide coupled to human serum albumin [20]. This semi-synthetic inhibitor is added to serum in a volume ratio of 1 : 50 to arrive at a final concentration of 20 µg/mL. Extensive tests were performed with allergen strips (Fig. 3), the ImmunoCAP single allergen system, the ImmunoCAP ISAC (both Phadia, Uppsala, Sweden), and the Immulite 2000 (Siemens Healthcare, Erlangen, Germany) [20]. Generally, CCD inhibition led to a vast reduction of the number of positive, recte false-positive results in all test systems, even in the ISAC system for the reasons detailed above. Unsatisfactory results where the reading remained above or only slightly below the threshold of 0.35 U/mL were notably obtained for honeybee venom and the venom component Api m 1 (Tab. 1).


Coping with cross-reactive carbohydrate determinants in allergy diagnosis
Example of the effect of CCD inhibition. Serum of a 46-year-old male from Carinthia, Austria, was tested with custom made multi-allergen strips (Mediwiss Analytics, Moers, Germany) containing one or three CCD reporter bands. Experimental details can be found in [20]. In the presence of inhibitor only allergens with anamnestic substantiation appeared as positive.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5016538&req=5

Fig3: Example of the effect of CCD inhibition. Serum of a 46-year-old male from Carinthia, Austria, was tested with custom made multi-allergen strips (Mediwiss Analytics, Moers, Germany) containing one or three CCD reporter bands. Experimental details can be found in [20]. In the presence of inhibitor only allergens with anamnestic substantiation appeared as positive.
Mentions: An example for a protease treated inhibitor is the “proglycan” CCD-blocker (www.proglycan.com) consisting of bromelain glycopeptide coupled to human serum albumin [20]. This semi-synthetic inhibitor is added to serum in a volume ratio of 1 : 50 to arrive at a final concentration of 20 µg/mL. Extensive tests were performed with allergen strips (Fig. 3), the ImmunoCAP single allergen system, the ImmunoCAP ISAC (both Phadia, Uppsala, Sweden), and the Immulite 2000 (Siemens Healthcare, Erlangen, Germany) [20]. Generally, CCD inhibition led to a vast reduction of the number of positive, recte false-positive results in all test systems, even in the ISAC system for the reasons detailed above. Unsatisfactory results where the reading remained above or only slightly below the threshold of 0.35 U/mL were notably obtained for honeybee venom and the venom component Api m 1 (Tab. 1).

View Article: PubMed Central - PubMed

ABSTRACT

A relevant proportion of allergy diagnosis is accomplished by in vitro determination of specific immunglobulin E (sIgE) to extracts from suspected allergens. Such extracts inevitably contain glycoproteins, which may react with patients’ IgE. In the case of plant and insect allergens, the relevant epitope structure is an α-1,3-fucose on the Asn-linked sugar residue of so-called N-glycans. Due to their wide distribution, N-glycans carrying this epitope are known as “cross-reactive carbohydrate determinant(s)” (CCD[s]). About 15 years of awareness allow the conclusion that anti-CCD IgE does not cause noticeable clinical symptoms. In consequence, diagnostic results arising from CCD reactivity must be rated as false positives. With up to 30 % of CCD reactive patients, this can be regarded as a serious problem.

Another cross-reactive carbohydrate determinant became notorious as a potential cause of anaphylactic reactions to a recombinant glycoprotein drug carrying α-1,3-galactose. This galactose-containing determinant (GalCD, galactose containing cross-reactive carbohydrate determinant) was supposed as a trigger for delayed allergic reactions to red meat in several cases. Thus, α-1,3-galactose may have clinical relevance in certain cases – possibly as a result of tick bites. Often, however, GalCDs probably cause false-positive results with milk and meat extracts. No clear evidence for the role of other non-human carbohydrate structures such as N-glycolylneuraminic acid as CCD has been presented so far.

Remedies for sIgE based in vitro diagnosis come in the form of non-glycosylated recombinant allergen components or of specific CCD inhibitors. The high potential of recombinant allergens is optimally realized in the context of component resolved diagnosis using allergen arrays with more than 100 components, whereas CCD inhibitors increase the specificity of conventional extract-based diagnosis. Reagents for the detection and inhibition of CCDs from plants and insects have been developed, whereas tools for GalCDs of milk and meat lag behind.

No MeSH data available.