Reza Falak1, Mojtaba Sankian2, Hanieh Ketabdar3, Malihe Moghadam4, Abdol-Reza Varasteh4. 1. Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2. Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. 3. Department of Biology, Faculty of Science, Islamic Azad University, Mashhad Branch, Mashhad, Iran. 4. Allergy Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Abstract
BACKGROUND: Allergens are mostly composed of glycoprotein structures. It is believed that glycan-specific antibodies may lead to false-positive reactions in immunoassays. In this study we investigated the glycosylation state of grape allergens as well as the presence of antibodies to cross-reactive carbohydrate determinants (anti-CCDs) in sera from grape-sensitive individuals. METHODS: Grape extract proteins were electrotransferred onto PVDF membranes and their glycosylation states were analyzed by blotting methods. To assess the presence of anti-CCDs, natural and mildly deglycosylated proteins were immunoblotted with grape-allergic subjects' sera. We also measured the IgE reactivity of each subject's sera with other fruit extracts via an indirect ELISA. RESULTS: Immunoblotting studies showed that mildly deglycosylated grape proteins had lower IgE-binding capacity than their intact natural counterparts, which could be due to the presence of anti-CCDs. Biotinylation studies confirmed that the glycosylation levels of the 24, 32, and 60 kDa IgE-reactive proteins were higher than those of the 38 and 45 kDa ones. Lectin blotting showed that the 24 and 60 kDa bands were highly mannosylated, with the highest level of mannosylation on the 24 kDa allergen. CONCLUSION: This study showed that some grape allergens are glycosylated and that anti-CCD antibodies may cause weakly false-positive results during assessment of IgE reactivity to grape allergens.
BACKGROUND: Allergens are mostly composed of glycoprotein structures. It is believed that glycan-specific antibodies may lead to false-positive reactions in immunoassays. In this study we investigated the glycosylation state of grape allergens as well as the presence of antibodies to cross-reactive carbohydrate determinants (anti-CCDs) in sera from grape-sensitive individuals. METHODS: Grape extract proteins were electrotransferred onto PVDF membranes and their glycosylation states were analyzed by blotting methods. To assess the presence of anti-CCDs, natural and mildly deglycosylated proteins were immunoblotted with grape-allergic subjects' sera. We also measured the IgE reactivity of each subject's sera with other fruit extracts via an indirect ELISA. RESULTS: Immunoblotting studies showed that mildly deglycosylated grape proteins had lower IgE-binding capacity than their intact natural counterparts, which could be due to the presence of anti-CCDs. Biotinylation studies confirmed that the glycosylation levels of the 24, 32, and 60 kDa IgE-reactive proteins were higher than those of the 38 and 45 kDa ones. Lectin blotting showed that the 24 and 60 kDa bands were highly mannosylated, with the highest level of mannosylation on the 24 kDa allergen. CONCLUSION: This study showed that some grape allergens are glycosylated and that anti-CCD antibodies may cause weakly false-positive results during assessment of IgE reactivity to grape allergens.
Authors: M J van der Veen; R van Ree; R C Aalberse; J Akkerdaas; S J Koppelman; H M Jansen; J S van der Zee Journal: J Allergy Clin Immunol Date: 1997-09 Impact factor: 10.793
Authors: A Mari; P Iacovacci; C Afferni; B Barletta; R Tinghino; G Di Felice; C Pini Journal: J Allergy Clin Immunol Date: 1999-06 Impact factor: 10.793