Characterization of a dodecapeptide containing a dominant epitope of Par j1 and Par o 1, the major allergens of P-judaica and P-officinalis pollen

The pollen of Parietaria, a weed of the Urticaceae family, is a major cause of respiratory allergy in Europe, where the most common species are P.juda ica and P. officinalis. Previously, we reported that a beta-galactosidase f usion protein (Ga-BG) expressing a 26-bp cDNA fragment (6a cDNA) contained a dominant IgE-binding epitope (6a epitope) of the major allergens Par J 1 and Par J 1. The present study aimed to define. the amino-acid sequence con taining the 6a epitope. We analyzed the reactivity of anti-Par o 1 antibodi es affinity purified from allergic patient sera with: 1) a panel of synthetic peptides deduced from the 6a nucleotide sequence us ing different reading frames 2) glutathione 5-transferase (GST) fusion proteins containing selected pept ides. The peptide NSARARADSCRI (p102) specifically bound anti-Par o 1 antibodies affinity purified from allergic patient sera or from rabbit anti-Par o 1 an tiserum (ELISA). The related peptide NSARAGTSSCRI (p101) reacted to human b ut not to rabbit, anti-Par o 1 antibodies. GST fusion proteins containing p 101 (GST 3.5) or p102 (GST 3.2) extensively inhibited the binding between P ar o 1 and IgE or IgG antibodies from an allergic patient serum pool accord ing to a dose-response curve. Percent inhibition of: IgE antibodies binding obtained by absorbing a solution (50 pi) of affinity-purified antibodies w ith 5 mu g of GST 3.2 or with 1.2 mg of GST 3.5 was 69% and 66%, respective ly. In conclusion, the results of the present study indicate that the amino -acid sequences NSARARADSCRI (p102) and NSARAGTSSCRI (p101) contain the dom inant epitope of Par o I and Par J 2 for human IgE and IgG antibodies indic ated as 6a epitope. Moreover, the study shows that the epitope is conserved in recombinant molecules containing these peptides, irrespective of the fu sed polypeptide (beta-galactosidase or GST). The knowledge of the amino-aci d sequence of this dominant epitope is important in therapeutic approaches to the development of allergen-derived haptens.