Humoral and Cell-mediated Autoimmune Reactions to Human Acidic Ribosomal P(2) Protein in Individuals Sensitized to Aspergillus fumigatus P(2) Protein

A panel of cDNAs encoding allergenic proteins was isolated from an Aspergillus fumigatus cDNA library displayed on the surface of filamentous phage. Solid phase–immobilized serum immunoglobulin E (IgE) from A. fumigatus–allergic individuals was used to enrich phage displaying IgE-binding molecules. One of the cDNAs encoded a 11.1-kD protein that was identified as acidic ribosomal phosphoprotein type 2 (P(2) protein). The allergen, formally termed rAsp f 8, shares >62% sequence identity and >84% sequence homology to corresponding eukaryotic P(2) proteins, including human P(2) protein. The sequences encoding human and fungal P(2) protein were subcloned, expressed in Escherichia coli as His(6)-tagged fusion proteins, and purified by Ni(2+)–chelate affinity chromatography. Both recombinant P(2) proteins were recognized by IgE antibodies from allergic individuals sensitized to the A. fumigatus P(2) protein and elicited strong type 1–specific skin reactions in these individuals. Moreover, human and fungal P(2) proteins induced proliferative responses in peripheral blood mononuclear cells of A. fumigatus– allergic subjects sensitized to the fungal P(2) protein. These data provide strong evidence for in vitro and in vivo humoral and cell-mediated autoreactivity to human P(2) protein in patients suffering from chronic A. fumigatus allergy.