Differential recognition of recombinant Phl p 5 isoallergens by Phl p 5-specific T cells

Background: At present, recombinant allergens are considered for the diagno sis and treatment of atopic allergies. To evaluate the theoretical impact o f isoallergen variation on the selection of isoallergens for specific aller gy vaccination, we characterized the T-cell response of allergic patients t o the Phleum pratense major allergen, Phl p 5, and five of its recombinant isoallergens. Methods: Phl p 5-specific T cell lines (TCLs) were isolated f rom the peripheral blood of 3 allergic rhinitis patients, and their reactiv ity patterns were studied in detail. Results: The TCLs were highly crossrea ctive with related grasses. The crossreactivity with Poa pratensis was more extensive than with Lolium perenne, directly reflecting the sequence ident ity between Phl p 5, Poa p 5, and Lol p 5. The TCLs produced IFN-gamma and IL-4 simultaneously, resembling a Th0-like cytokine production profile. Int erestingly, when T cell clones were tested with natural Phl p 5 and five rP hl p 5 isoallergens, a differential recognition pattern was found. One of t he TCLs exclusively reacted with Phl p 5b, another reacted with all isoform s tested, and the third reacted strongly with native purified Phl p 5, but only weakly with all five recombinant isoallergens. Conclusion: These resul ts indicate that Phl p 5-specific T cells are highly heterogeneous, and tha t they differentially recognize isoallergens. This indicates that when reco mbinant Phl p 5 is considered for allergy vaccination, a mixture of isoalle rgens representing the different isoallergen groups may clinically prove to be more effective than single isoallergens.