Class I endochitinase containing a hevein domain is the causative allergen in latex-associated avocado allergy.
BACKGROUND
In the medical literature immunoglobulin (Ig)E-mediated sensitization to avocado is rarely reported. On the other hand, more than 50% of subjects having IgE-mediated natural rubber latex allergy are sensitized to avocado fruit as demonstrated by skin-prick testing and/or specific IgE measurements and about 10-20% report hypersensitivity reactions after ingesting avocado.


OBJECTIVE
The underlying pathomechanism of latex-associated avocado allergy is still unknown. The conserved hevein domain of the major latex allergen prohevein (Hev b 6.01) is a ubiquitous chitin-binding protein structure that can be found in several plant proteins and may be responsible for the observed cross-reactivity between latex and avocado fruit.


METHODS
Chitin-binding avocado proteins (CBAPs) were isolated by affinity-chromatography and their IgE-binding characteristics were studied by immunoblotting using the sera from 15 avocado-sensitized latex patients. Inhibition experiments using isolated hevein and CBAPs as inhibitor solutions were performed to study the immunological cross-reactivity between both protein species and to assess the role of the CBAPs as mediators in latex-associated avocado allergy.


RESULTS
In 80% of avocado-sensitized subjects (n = 15), IgE antibodies directed against a 31-kDa allergen were detected by immunoblotting. This IgE-binding protein was identified by protein sequencing to be a class I endochitinase containing a hevein domain at the N-terminus. Purified native and digested (using simulated gastric fluid) endochitinase were able to completely block all avocado-specific IgE antibodies in six out of seven avocado patients.


CONCLUSIONS
Sensitization to endochitinase class I containing a hevein domain is the main underlying pathomechanism in latex-mediated avocado allergy.
Posch
A
A
Research Institute for Occupational Medicine (BGFA), Bochum, Germany.
Wheeler
C H
CH
Chen
Z
Z
Flagge
A
A
Dunn
M J
MJ
Papenfuss
F
F
Raulf-Heimsoth
M
M
Baur
X
X
D000485:Allergens / Q000276:immunology; D052179:Antigens, Plant; D023181:Antimicrobial Cationic Peptides; D002686:Chitin / Q000378:metabolism; D002688:Chitinases / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D003429:Cross Reactions; D005512:Food Hypersensitivity / Q000276:immunology*; D006282:Health Personnel; D006801:Humans; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000097:blood; D007840:Latex / Q000009:adverse effects; D020315:Latex Hypersensitivity; D019770:Lauraceae / Q000009:adverse effects* / Q000201:enzymology; D037102:Lectins / Q000737:chemistry* / Q000276:immunology; D037121:Plant Lectins; D010940:Plant Proteins / Q000737:chemistry* / Q000276:immunology; D011498:Protein Precursors / Q000276:immunology; D012882:Skin Tests
D000485:Allergens; D052179:Antigens, Plant; D023181:Antimicrobial Cationic Peptides; C097982:Hev b 6.01 protein, Hevea brasiliensis; D007840:Latex; D037102:Lectins; D037121:Plant Lectins; D010940:Plant Proteins; D011498:Protein Precursors; C045875:hevein; D002686:Chitin; D007073:Immunoglobulin E; D002688:Chitinases