Peanut components

Allergen related documents

Print Print icon Tell a friend Tell a friend icon

Summary

Latin: Arachis hypogaea

Recombinant allergens:

  • rAra h 1
  • rAra h 2
  • rAra h 3
  • rAra h 8

Peanuts are the seeds of an annual legume, which grows close to the ground and produces its fruit below the soil surface. This is in contrast to tree nuts like Walnuts and Almonds. Peanut is a member of the Fabaceae or legume family, whereas tree nuts are not.

Multiple Peanut varieties are grown, with more than 40% of the American Peanut crop consumed as Peanut butter (1). Runners have become the dominant Peanut type grown in the U.S. due to the spectacular increase in yield that they allow; they are a very important source of Peanut butter. Virginias have the largest kernels and account for most of the Peanuts roasted and sold in their shells. Spanish peanuts have smaller kernels covered with a reddish-brown skin. Valencias are small, very sweet Peanuts usually roasted and sold in the shell, or boiled, but seldom used in processed foods.

The major Peanut allergens are homologous to the seed storage proteins of the conglutin, vicilin, and glycinin families (2).

Peanut proteins were originally classified as albumins (water-soluble) or globulins (saline-soluble); the globulins were in turn subdivided into arachin and conarachin fractions (the major storage proteins). Components of the albumin fraction of Peanuts are agglutinins, lectin-reactive glycoproteins, protease inhibitors, alpha-amylase inhibitors and phospholipases (3).

The major storage proteins of legumes are globulins, subdivided into legumins and vicillins. Two major Peanut allergens, Ara h 1 and Ara h 2, are heat-stable vicillin proteins (1, 4).

Peanut contains up to 32 different proteins, of which at least 18 have been identified as being capable of binding specific IgE antibodies (5-6). Varieties of Peanuts from different parts of the world contain similar proteins, including Ara h 1 and Ara h 2, and the IgE-binding properties have also been reported to be similar to a great extent (7).

Allergens characterised to date include:

  • Ara h 1, a 7S vicilin-like globulin (8)
     
  • Ara h 2, a 2S albumin, a conglutin seed storage protein, a trypsin inhibitor (9)
     
  • Ara h 3, an 11S globulin, a glycinin, a trypsin inhibitor (10)
     
  • Ara h 4, a glycinin (11)
     
  • Ara h 5, a profilin (11)
     
  • Ara h 6, a conglutin, 2S albumin (12)
     
  • Ara h 7, a conglutin (11)
     
  • Ara h 8, a Bet v 1-homologous allergen (13)
     
  • Ara h Agglutinin (14)
     
  • Ara h LTP, a lipid transfer protein (15)
     
  • Ara h Oleosin (16)

Ara h 1 comprises 12% to 16% of the total protein in Peanut In population studies, sensitisation to Ara h 1 was found in 95% of Peanut-allergic patients from North America (4, 17-19), but in fewer Peanut-allergic patients of 3 European populations, varying from 35% to 70% (1, 12, 20-21). These differences were not reported for Ara h 2, even though Peanuts from different varieties and from different parts of the world contain similar proteins and the IgE binding properties are similar (7). Unidentified Peanut proteins with molecular weights somewhat lower than 15 kDa may be important allergens as well (22). Ara h 3 is recognised by serum IgE from 45% - 50% of patients with Peanut sensitivity (23). Ara h 5 shows up to 80% amino acid sequence identity with the panallergen profilin, but is present only in low amounts in Peanut extracts. 13% to 16% of Peanut-allergic individuals are sensitised to Peanut profiling (24). Nonetheless, a number of peanut allergens are involved in the sensitisation process as demonstrated in an European study of Peanut-allergic individuals, where sensitisation to Ara h 2 was found in 85%, to Ara h 4 in 53%, to Ara h 5 in 13%, to Ara h 6 in 38%, and to Ara h 7 in 43% of the selected sera (12).

Sensitization to Peanut occurs with a high degree of heterogeneity to a number of Peanut allergens. Mono-sensitization to a single Peanut allergen is relatively rare (25). Although sensitisation to Ara h 1 and Ara h 2 occurs in the great majority of Peanut-allergic individuals, the wide range of allergens present in whole Peanut protein extract appears to be most appropriate to consider when testing for Peanut allergy (19).

For example, in a British study, evaluating sera of 40 Peanut-allergic individuals, of 18 allergens identified, 8 were bound by >50% of patients. The study concluded that promiscuity of IgE binding appears more important than the recognition of individual proteins (26).

Furthermore, some Peanut-allergic subjects fail to bind to either Ara h 1 or 2 suggesting that whole Peanut, rather than Ara h 1 or 2, or the use of individual Peanut allergens would be more appropriate for measuring specific-IgE responses. This also illustrates that the relative contribution of all Peanut allergens needs to be investigated (19).

Helpful in this regard are the Peanut allergens that have been expressed as recombinant allergens.

Recombinant allergens, which are genetically engineered isoforms resembling allergen molecules from known allergen extracts, have immunoglobulin E (IgE) antibody binding comparable to that of natural allergens and generally show excellent reactivity in in vitro and in vivo diagnostic tests (27). To date, many different recombinant allergens of pollens, molds, mites, bee venom, latex and foods have been cloned, sequenced, and expressed.

Recombinant allergens have a wide variety of uses, from the diagnosis and management of allergic patients to the development of immunotherapy to the standardisation of allergenic test products as tools in molecular allergology (28-29). Recombinant allergens are particularly useful for further investigations in allergies manifesting wide cross-reactivity.

Compiled by Dr Harris Steinman, harris@zingsolutions.com.

 

References

  1. Saavedra-Delgado AM. The many faces of the peanut. Allergy Proc 1989;10(4):291-4
    Bohle B, Swoboda I, Spitzauer S, et al. Food Antigens: structure and function. In Metcalf DD, Sampson HA, Simon RA, editors. Food Allergy: Adverse reactions to Foods and Food Additives. Blackwell Scientific Publications 2003:38-50
  2. Loza C, Brostoff J Peanut allergy. Clin Exp Allergy 1995;25(6):493-502
    Bohle B, Swoboda I, Spitzauer S, et al. Food Antigens: structure and function. In Metcalf DD, Sampson HA, Simon RA, editors. Food Allergy: Adverse reactions to Foods and Food Additives. Blackwell Scientific Publications 2003:38-50
  3. Dean TP. Immunological responses in peanut allergy. [Editorial] Clin Exp Allergy 1998;28:7-9
  4. Scurlock AM, Burks AW. Peanut allergenicity. Ann Allergy Asthma Immunol 2004;93(5 Suppl 3):S12-8.
  5. Koppelman SJ, Vlooswijk RA, Knippels LM, Hessing M, Knol EF, van Reijsen FC, Bruijnzeel-Koomen CA. Quantification of major peanut allergens Ara h 1 and Ara h 2 in the peanut varieties Runner, Spanish, Virginia, and Valencia, bred in different parts of the world. Allergy 2001 Feb;56(2):132-7
  6. Wichers HJ, De Beijer T, Savelkoul HF, Van Amerongen A. The major peanut allergen Ara h 1 and its cleaved-off N-terminal peptide; possible implications for peanut allergen detection. J Agric Food Chem 2004;52(15):4903-7
  7. Maleki SJ, Viquez O, Jacks T, Dodo H, Champagne ET, Chung SY, Landry SJ. The major peanut allergen, Ara h 2, functions as a trypsin inhibitor, and roasting enhances this function. J Allergy Clin Immunol 2003;112(1):190-5
  8. Koppelman SJ, Knol EF, Vlooswijk RA, Wensing M, Knulst AC, Hefle SL, Gruppen H, Piersma S. Peanut allergen Ara h 3: isolation from peanuts and biochemical characterization. Allergy 2003;58(11):1144-51
  9. Kleber-Janke T, Crameri R, Appenzeller U, Schlaak M, Becker WM Selective cloning of peanut allergens, including profilin and 2S albumins, by phage display technology. Int Arch Allergy Immunol 1999;119:265-274
  10. Koppelman SJ, de Jong GA, Laaper-Ertmann M, Peeters KA, Knulst AC, Hefle SL, Knol EF. Purification and immunoglobulin E-binding properties of peanut allergen Ara h 6: evidence for cross-reactivity with Ara h 2. Clin Exp Allergy 2005;35(4):490-7.
  11. Mittag D, Akkerdaas J, Ballmer-Weber BK, Vogel L, Wensing M, Becker WM, Koppelman SJ, Knulst AC, Helbling A, Hefle SL, Van Ree R, Vieths S. Ara h 8, a Bet v 1-homologous allergen from peanut, is a major allergen in patients with combined birch pollen and peanut allergy. J Allergy Clin Immunol 2004;114(6):1410-7.
  12. Burks AW, Cockrell G, Connaughton C, Guin J, Allen W, Helm RM. Identification of peanut agglutinin and soybean trypsin inhibitor as minor legume allergens. Int Arch Allergy Immunol 1994;105(2):143-9
  13. Asero R, Mistrello G, Roncarolo D, Amato S, Caldironi G, Barocci F, Van Ree R. Immunological cross-reactivity between lipid transfer proteins from botanically unrelated plant-derived foods: a clinical study. Allergy 2002;57(10):900-6
  14. Pons L, Chery C, Romano A, Namour F, Artesani MC, Gueant JL. The 18 kDa peanut oleosin is a candidate allergen for IgE-mediated reactions to peanuts. Allergy 2002;57 Suppl 72:88-93
    Pomes A, Helm RM, Bannon GA, Burks AW, Tsay A, Chapman MD. Monitoring peanut allergen in food products by measuring Ara h 1. J Allergy Clin Immunol 2003;111(3):640-5
  15. Burks AW, Sampson HA, Bannon GA. Review article series II: peanut allergens. Allergy 1998;28:1251-1257
  16. Bernard H, Paty E, Mondoulet L, Burks AW, Bannon GA, Wal JM, Scheinmann P. Serological characteristics of peanut allergy in children. Allergy 2003;58(12):1285-1292
    Clarke MC, Kilburn SA, Hourihane JO, Dean KR, Warner JO, Dean TP. Serological characteristics of peanut allergy. Clin Exp Allergy 1998;28(10):1251-7
  17. de Jong EC, Van Zijverden M, Spanhaak S, Koppelman SJ, Pellegrom H, Penninks AH. Identification and partial characterization of multiple major allergens in peanut proteins. Clin Exp Allergy 1998;28(6):743-51
  18. Koppelman SJ, Wensing M, Ertmann M, Knulst AC, Knol EF. Relevance of Ara h1, Ara h2 and Ara h3 in peanut-allergic patients, as determined by immunoglobulin E Western blotting, basophil-histamine release and intracutaneous testing: Ara h2 is the most important peanut allergen. Clin Exp Allergy 2004 Apr;34(4):583-90
  19. Stanley JS, Bannon GA. Biochemistry of food allergens. Clin Rev Allergy Immunol 1999;17(3):279-91
  20. Martinez A, Asturias JA, Monteseirin J, Moreno V, Garcia-Cubillana A, Hernandez M, de la Calle A, Sanchez-Hernandez C, Perez-Formoso JL, Conde J. The allergenic relevance of profilin (Ole e 2) from Olea europaea pollen. Allergy 2002;57 Suppl 71:17-23.
  21. Shreffler WG, Beyer K, Chu TH, Burks AW, Sampson HA. Microarray immunoassay: association of clinical history, in vitro IgE function, and heterogeneity of allergenic peanut epitopes. J Allergy Clin Immunol 2004;113(4):776-82.
  22. Lewis SA, Grimshaw KE, Warner JO, Hourihane JO. The promiscuity of immunoglobulin E binding to peanut allergens, as determined by Western blotting, correlates with the severity of clinical symptoms. Clin Exp Allergy 2005;35(6):767-73.
  23. Niederberger V, Stubner P, Spitzauer S, Kraft D, Valenta R, Ehrenberger K, Horak F. Skin test results but not serology reflect immediate type respiratory sensitivity: a study performed with recombinant allergen molecules. J Invest Dermatol 2001;117(4):848-51.
  24. B.K. Ballmer-Weber, J. Lidholm and S. Vieths Recombinant allergens in the diagnosis of food allergy: Which are the advantages? Revue francaise d allergologie 2007;47(3):126-128
    Lidholm J, Ballmer-Weber BK, Mari A, Vieths S. Component-resolved diagnostics in food allergy. Curr Opin Allergy Clin Immunol 2006;6(3):234-240
2008