Complementary DNA cloning of the major allergen Phl p I from timothy grass (Phleum pratense); recombinant Phl p I inhibits IgE binding to group I allergens from eight different grass species.

Background: Grass pollens, such as pollen from timothy grass (Phleum pratense), represent a major cause of type I allergy.

Objective: In this report we attempted to determine how cross-reactive allergenic components of grass pollens from different species can be represented by a minimum number of recombinant allergens.

Methods: We isolated and sequenced a timothy grass pollen cDNA coding for the major allergen Phl p I. A recombinant Phl p I-beta-galactosidase fusion protein, which bound to IgE in 87% of patients with grass pollen allergy, was produced in Escherichia coli. Using recombinant Phl p V and Phl p I, we defined representative patients' sera that bound to group I but not to group V allergens, as well as sera with reactivity against group I and group V allergens. IgE immunoblot inhibition studies were done with nitrocellulose-blotted pollen extracts from eight grass species with different geographic distribution.

Results: Preadsorption of patients' sera with recombinant nonfusion Phl p I strongly reduced IgE binding to group I allergens from the eight grasses, showing extensive cross-reactivity between species.

Conclusions: A single recombinant group I allergen contains many of the IgE epitopes of group I isoallergens from a number of different grass species.