A clone (P2) coding for an allergen of Parietaria judaica (Pj) pollen has been isolated and sequenced from a cDNA library in lambda ZAP using a pool of 23 sera from Pj-allergic patients. The clone contained an insert of 622 nucleotides with an open reading frame of 133 amino acids (aa) and a putative signal peptide of 31 aa giving a deduced mature processed protein of 102 aa with a molecular mass of 11 344 Da. The expressed recombinant protein, named rPar j 2.0101, was a major allergen since it reacted with IgE of 82% (23/28) of the sera of Pj-allergic subjects analyzed. It was shown to be a new allergen since (i) the amino acid sequence homology with the already reported recombinant allergen Par j 1.0101 was 45% and (ii) there was no cross-inhibition between rPar j 2.0101 and rPar j 1.0101. In addition, rPar j 2.0101 inhibited 35% of the specific IgE for 10–14 kDa native allergens and preincubation of sera from Pj-allergic patients with both rPar j 2.0101 and rPar j 1.0101 fully abolished the IgE recognition of the 10–14 kDa native allergen region, suggesting that these two allergens contributed to the region.
