T07019: Do protein structural features confer stability to digestion of food allergens?

Study Duration: January 2001 to February 2004

Contractor: Nottingham University

Allergens found in plants can be grouped into 19 protein families. This suggests that the proteins capable of causing allergic reactions might share common features. It is possible that particular structural features could account for the high stability to digestion (i.e. proteolytic stability) of many food allergens, and that such stability might be involved in sensitisation or reaction to these allergens. This project aims to determine whether structural features of proteins affect their allergenicity.

Two members of the 2S albumin family of proteins will be used in this study; Ber e 1, an allergen found in Brazil nuts, and SFA8, a widely consumed protein from sunflower seed, not yet implicated as a major allergen. Parts of the Ber e 1 protein will be recombined with the SFA8 protein in order to determine which specific parts of the Ber e 1 protein confer allergenicity.

Ber e 1 and SFA8 will be produced by genetically modified yeast. The two proteins will also be prepared from brazil nuts and sunflower seeds using conventional protein purification techniques. The proteolytic stability of the proteins will be determined by digestion in simulated gastric fluid. The allergenicity of the proteins will be investigated using an experimental model system. In addition, the structure, thermal stability and chemical stability of the proteins will be assessed.

The yeast will also be genetically modified to produce hybrid proteins in which regions of the SFA8 protein have been replaced by the equivalent region of Ber e 1. The region of Ber e 1 responsible for inducing an allergic reaction will be identified by exposing the hybrid proteins to sera from brazil nut allergic subjects. The sera is likely to contain IgE antibodies capable of recognising the allergenic region.

Ber e 1 and SFA8 produced by the yeast were very similar to the corresponding proteins purified from brazil nuts and sunflower seeds in terms of structure, immunogenicity, and thermal and chemical stability. Yeast-derived Ber e 1 and SFA8 will therefore be useful tools in future research to identify the features that make some proteins allergenic. There was no significant difference between the proteolytic stability of Ber e 1 and SFA8, suggesting that proteolytic stability alone does not accurately predict whether a protein is likely to be allergenic.

Using a protein microarray system and in agreement with previous published studies, the immunodominant determinant of Ber e 1 was found to be similar to the allergenic regions of other 2S albumin family proteins.

Although Ber e 1 purified from Brazil nut is known to be an important allergen, it only induced relatively weak IgE responses in the experimental system. This suggests that other components of brazil nuts might be required for Ber e 1 to induce an allergenic response.

The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: library&info@foodstandards.gsi.gov.uk)

Publications:

Murtagh, G.J., Archer, D.B., Dumoulin, M., Ridout, S., Matthews, S., Arshad, S.H., Alcocer, M.J.C. (2003). In vitro stability and immunoreactivity of the native and recombinant plant food 2S albumins Ber e 1 and SFA-8. Clinical and Experimental Allergy 33 (8):1147-52.

Alcocer, M.J.C., Murtagh, G.J., Bailey, K., Dumoulin, M., Mesenguer, A.S., Parker, M.J., Archer, D.B. (2002). The disulphide mapping, folding and chracterisation of recombinant Ber e 1, an allergenic protein and SFA8, two sulphur-rich 2S plant albumins. Journal of Molecular Biology 324 (1), 165-175.

Murtagh, G.J., Archer, D.B., Dumoulin, M., Alcocer, M.J.C. (2002). Stability of recombinant 2S albumin plant food allergens in vitro. Biochemical Society Transactions 30 (6), 913-915.

Posters:

Lin J, Murtagh GJ, George S, Alcocer MJC (2004). Are protein structural features involved in the 'intrinsic' allergenicity of 2S albumins? - a protein microarray approach. 9th International Food Allergy Symposium. Budapest, April.

Murtagh, G.J., Dumoulin, M., Archer, D.B., Alcocer, M.J. (2003). Brazil nut Ber e 1 and sunflower SFA-8 � models for the study of the structure/allergenicity relationship in 2S albumin proteins. Rank Prize Funds Mini-Symposium on Plant Food Allergens, March.

Akkerdaas, J.,Schocker, F., Alcocer, M., Murtagh, G., Schilte, P., Knulst, A., Hefle, S., Ferreira, F., Aalberse, R., van Ree, R. (2003). Detection and Immunological Characterization of Hazelnut 2S albumin. American Academy of Allergy, Asthma and Immunology meeting, Denver, March.

Murtagh GJ, M, Dumoulin, D B, Archer and M J, Alcocer (2002). Stability of 2S albumin allergens in vitro. Biochemical Society Meeting No.677, Cardiff University, Cardiff, Wales, July.

Contact: For any enquiries concerning this research project, please contact the relevant Programme contact or email food.allergy@foodstandards.gsi.gov.uk