Identification of a new natural Ara h 6 isoform and of its proteolytic product as major allergens in peanut.
Numerous food allergens of plant origin belong to the 2S albumin family, including peanut Ara h 2. In addition to Ara h 2, several other conglutins related to 2S albumins are present in peanut seeds. We evaluated the allergenicity of different peanut conglutins as compared with Ara h 2. Several conglutins were isolated from the kernel, i.e. Ara h 2, a new isoform of Ara h 6 and its derived product, which is likely to be naturally formed during seed processing. Enzyme allergosorbent tests performed on sera of peanut allergic patients showed that more than 94% of 47 analyzed patients had positive IgE responses to Ara h 6 isoform and to its degradation product. Skin prick tests with the new isoform of Ara h 6 led to a positive response in seven out of the eight tested patients. Both enzyme allergosorbent tests and skin prick tests showed that the reactivity of Ara h 6 was similar to, or even higher than, that of Ara h 2, suggesting that the present isoform of Ara h 6 is as allergenic as Ara h 2. In addition the IgE response to the plant processed (i.e., hydrolyzed) Ara h 6 new isoform is equivalent to the IgE response to the native isoform. The IgE immunoreactivity is mostly abrogated by chemical reduction and denaturation of Ara h 6 isoforms, which underlined the importance of tertiary structure in Ara h 6 immunoreactivity. These results, and particularly the high correlation between anti-Ara h 2 and anti-Ara h 6 IgE responses, emphasise the major role of 2S albumins in peanut allergenicity.
Bernard
H
H
INRA-Laboratoire d'immuno-allergie alimentaire, CEA-Saclay, 91191 Gif-sur-Yvette, France. herve.bernard@cea.fr
Mondoulet
L
L
Drumare
M F
MF
Paty
E
E
Scheinmann
P
P
Thaï
R
R
Wal
J M
JM
D055516:2S Albumins, Plant; D000485:Allergens / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D002648:Child; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D021183:Peanut Hypersensitivity / Q000276:immunology; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D020033:Protein Isoforms / Q000032:analysis*; D012882:Skin Tests; D014357:Trypsin / Q000378:metabolism
D055516:2S Albumins, Plant; D000485:Allergens; D052179:Antigens, Plant; C492737:Ara h 6 allergen, Arachis hypogaea; D010446:Peptide Fragments; D020033:Protein Isoforms; D007073:Immunoglobulin E; D014357:Trypsin