CLONING OF A CDNA-ENCODING A GROUP-V (GROUP-IX) ALLERGEN ISOFORM FROMRYE-GRASS POLLEN THAT DEMONSTRATES SPECIFIC ANTIGENIC IMMUNOREACTIVITY

We have isolated and characterized the cDNA clone, 19R, that encodes a n isoform of a major rye-grass pollen allergen, Lol p V [previously re ferred to as Lol p 1b; Singh et al., Proc. Natl. Acad. Sci. USA 88 (19 91) 1384-1388; and Lol p IX; Suphioglu et al., Lancet 339 (1992) 569-5 72]. Clone 19R was isolated from a rye-grass pollen cDNA expression li brary using grass pollen-specific immunoglobulin E (IgE) antibodies (A b) from an allergic serum pool. The nucleotide (nt) sequence of clone 19R potentially encodes a 33.8-kDa protein of 339 amino acids (aa). It possesses a leader peptide essentially identical to the previously ch aracterized isoform of Lol p V (Lol p VA). This indicates a mature pro cessed 31.3-kDa protein of 314 aa, correlating well with the size of t he polypeptides revealed by Western analysis of pollen proteins using IgE Ab affinity purified from recombinant fusion protein (reFP) encode d by clone 19R as solid matrix. There is no N-glycosylation motif. The protein encoded by clone 19R, designated Lol p VB, has 66.4% identity and 80.4% similarity with Lol p VA. However, a Lol p VA-specific mono clonal Ab, FMC A7, does not recognize reFP encoded by clone 19R, indic ating that Lol p VB does not share this epitope. Cross-reactivity stud ies using affinity purified IgE Ab showed that both isoforms share sim ilar allergenic epitopes. Immunoblot analysis using sera from a popula tion of 30 patients showed that 80% possess IgE Ab that recognize both Lol p V isoforms. Variation occurred in the signal intensities of IgE binding. Like Lol p VA, Lol p VB is pollen specific and is part of th e same multigene family.