Presentation: Discovery of Putative Macadamia Nut Allergens By Patient IgE Binding and a Label-Free Shotgun Proteomics Approach ( World Allergy Congress)

Wednesday, 14 October 2015

Hall D1 Foyer (Floor 3) (Coex Convention Center)

Nanju Alice Lee, PhD , ARC Training Centre for Advanced Technologies in Food Manufacture, University of New South Wales, Sydney, Australia

Johanna Rost , ARC Training Centre for Advanced Technologies in Food Manufacture, University of New South Wales, Sydney, Australia

Sridevi Muralidharan, PhD , ARC Training Centre for Advanced Technologies in Food Manufacture, University of New South Wales, Sydney, Australia

Dianne Campbell, MD, PhD , Allergy and Immunology, Children's Hospital Westmead, Syndey, Australia

Sam Mehr, MD , Children's Hospital Westmead, Sydney, Australia

Backgrounds: Macadamia nut is a tree nut listed as a major allergen to be labelled on pre-packaged foods globally. At least 19 cases of macadamia nut allergy have been reported to date, however, the eliciting allergenic proteins have not been identified and consequently component resolved diagnosis has not been developed. This study aims to identify putative allergenic proteins in macadamia nut by combining patient IgE recognition with an allergenomics approach. The challenge is that macadamia nut genome sequence is only partially complete.

Methods: The proteomic profile was studied using a label-free shotgun proteomics approach. As the genome sequence of macadamia nut allergens is not available, homologies to other known allergens and affiliations to protein families were determined. The results from the allergenomic screening method were used to predict potential allergenic proteins and cross-reactivity with other plants particularly. The molecular weight distribution of proteins was determined by gel electrophoresis. Following in-gel digestion with trypsin, proteins were subjected to liquid chromatography coupled tandem mass spectrometry. Based on the shared peptide evidence, the identified proteins were clustered and the allergenic proteins were identified. Immunoreactive proteins were identified by immunoblotting with three patient sera confirmed to exhibit IgE-mediated reaction.

Results: Peptides matched to the sequences of 21 allergenic proteins belonging to different protein families such as seed storage proteins (conglutins and vicilins), rubber elongation factor proteins, phosphate binding proteins and detoxifying methylglyoxalases were identified. This included peptide sequence homologies to 5 conglutins, which are known allergens from Lupin angustifolius.

Conclusion: Allergenic proteins were confirmed to be seed storage proteins belonging to 11S, 7S and 2S proteins. Significant number of peptide sequence homologies to conglutins from Lupin angustifolius was observed, suggesting that there may be cross-reaction between macadamia and lupin allergens

1173 Discovery of Putative Macadamia Nut Allergens By Patient IgE Binding and a Label-Free Shotgun Proteomics Approach