ALLERGENIC ACTIVITY OF A MAJOR GRASS-POLLEN ALLERGEN IS ELEVATED IN THE PRESENCE OF NASAL SECRETION

Phl p5 is a major allergen of timothy grass and causes rhinitis and br onchial asthma in nearly all patients allergic to grass pollen. The bi ochemical processing of this molecule by the nasal mucosa at its first encounter and possible changes of its biologic activity are unknown. Two isoforms of the allergen were expressed in Escherichia coli and su bsequently purified. Conversion of these preparations to various forms with molecular size between 10 and 20 kD in the presence of nasal sec retion was observed. Surprisingly, in skin prick test assays with alle rgic patients the mixture of converted peptides caused significantly h igher allergic response when compared with the parent protein. Allerge nic activity of the recombinant N-terminal Phl p5a and the C-terminal Phl p5b as measured by skin prick test and histamine release assays wa s significantly higher than that of the respective parent molecules. U sing pancreatic rather than nasal secretion, Phl p5b was completely de graded and its allergenicity was almost completely reduced. Proteolyti c degradation converts Phl p5 to defined fragments with increased alle rgenicity. Complete degradation of Phl p5 on the mucosa could be a pre ventive strategy to destroy its potency for the induction of an allerg ic response.