The major Platanus acerifolia pollen allergen Pla a 1 has sequence homology to invertase inhibitors.
BACKGROUND
Sycamores or plane trees are an important source of airborne allergens in many cities of the United States and Western Europe. Pla a 1 has been described as a major allergen from Platanus acerifolia (London plane tree).


OBJECTIVE
To clone and characterize the cDNA for Pla a 1 and to express the recombinant protein.


METHODS
Pla a 1 was isolated by cationic exchange, gel filtration, and reverse-phase chromato-graphies. Pla a 1 cDNA was cloned by reverse transcription followed by polymerase chain reaction, using amino acid sequences from tryptic peptides of the allergen. The Pla a 1 encoding sequence has been subcloned into the pKN172 expression vector and expressed in Escherichia coli as a non-fusion protein. Purified recombinant protein has been tested for its IgE-binding capacity in immunoblot, immunoblot inhibition, and ELISA.


RESULTS
Pla a 1 reacted with serum IgE from 35 of the 42 (83.3%) Platanus-allergic patients studied and represented 60% of the total IgE-binding capacity of the P. acerifolia pollen extract. The allergen displayed 43% sequence identity to a grape invertase inhibitor and showed a predicted secondary structure characteristic of all-alpha proteins. Serological analysis revealed that both natural and recombinant forms of Pla a 1 displayed similar IgE-binding capacity.


CONCLUSIONS
Pla a 1 belongs to a new class of allergens related to proteinaceous invertase inhibitors. Recombinant Pla a 1 binds IgE in vitro like its natural counterpart and, therefore, it can be useful for specific diagnosis and structural studies.
Asturias
J A
JA
R&D Department, Bial-Arístegui, Bilbao, Spain. la.lp@bial.es
Ibarrola
I
I
Eraso
E
E
Arilla
M C
MC
Martínez
A
A
D031001:Aceraceae; D000485:Allergens / Q000235:genetics*; D052179:Antigens, Plant; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D006801:Humans; D010936:Plant Extracts / Q000235:genetics*; D011058:Pollen / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014197:Trees; D043324:beta-Fructofuranosidase / Q000037:antagonists & inhibitors / Q000235:genetics*
D000485:Allergens; D052179:Antigens, Plant; D018076:DNA, Complementary; C479039:Pla a 1, Platanus acerifolia; D010936:Plant Extracts; D012333:RNA, Messenger; D043324:beta-Fructofuranosidase