Pistachio vicilin, Pis v 3, is immunoglobulin E-reactive and cross-reacts with the homologous cashew allergen, Ana o 1.
BACKGROUND
Patients allergic to cashew nuts often report allergy to pistachio, which could be a result of cross-reactivity between the two as both are members of the Anacardiaceae family.


OBJECTIVE
Because cashew 7S globulin (vicilin, Ana o 1) is a recognized major allergen, we cloned the pistachio homologue and assayed it for IgE reactivity and cross-reactivity with Ana o 1.


METHODS
Degenerate primers for 7S globulin were used in PCR to amplify DNA from a pistachio cDNA library. An isolate was sequenced, cloned and expressed in Escherichia coli. Reactivity to the allergen was screened by dot blot using 19 pistachio and/or cashew-allergic patients' sera. Cross-reactivity was investigated by inhibition dot- and Western immunoblot assays using pistachio/cashew-allergic patients' sera, and monoclonal antibodies (MAbs) raised against recombinant Ana o 1 (rAna o 1).


RESULTS
An isolate was found that coded for a 7S vicilin-like protein, designated Pis v 3. IgE reactivity to Pis v 3 was found in the serum of seven of the 19 (37%) patients with histories of allergy to both pistachio and cashew or who were allergic to cashew but had never eaten pistachio. The seven patients with IgE that recognized rPis v 3 also recognized rAna o 1. Six of nine anti-rAna o 1 MAbs also showed reactivity to rPis v 3 on dot blots.


CONCLUSIONS
Of the 37% of pistachio/cashew-allergic patients' sera that recognized the pistachio allergen, rPis v 3, all showed complete cross-reactivity with rAna o 1. The data does not identify the primary sensitizing agent but suggests that IgE reactivity to rPis v 3 and rAna o 1 is focused on the most conserved regions of the proteins. Clinical histories suggest that in some cases, cashew was the sensitizing agent. rPis v 3 is a likely contributor to the observed co-sensitivity to pistachio and cashew in some patients.
Willison
L N
LN
Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA.
Tawde
P
P
Robotham
J M
JM
Penney
R M
RM
Teuber
S S
SS
Sathe
S K
SK
Roux
K H
KH
D000328:Adult; D000485:Allergens / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000595:Amino Acid Sequence; D031021:Anacardium / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D052179:Antigens, Plant; D001483:Base Sequence; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D021184:Nut Hypersensitivity / Q000276:immunology*; D027927:Pistacia / Q000276:immunology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D055314:Seed Storage Proteins; D016415:Sequence Alignment
D000485:Allergens; C464614:Ana o 1 protein, Anacardium occidental; D000911:Antibodies, Monoclonal; D052179:Antigens, Plant; D010940:Plant Proteins; D011994:Recombinant Proteins; D055314:Seed Storage Proteins; D007073:Immunoglobulin E; C015575:vicilin protein, plant