Molecular cloning of Per a 1 and definition of the cross-reactive Group 1 cockroach allergens.

BACKGROUND Sensitization to allergens produced by German and American cockroaches is strongly associated with the cause of asthma. Most of the cockroach allergens identified to date have been species specific. OBJECTIVE The aim of this study was to identify and sequence cross-reactive cockroach allergens. METHODS A Periplaneta americana cDNA library was screened with IgE antibody from patients in the United States who were allergic to cockroach and who were sensitized to Blattella germanica. RESULTS A cDNA clone was isolated that contained an 870-bp sequence with a 695-bp open reading frame, encoding a 231 amino acid protein, molecular weight 26.2 kd. Plaque immunoassays using anti-Bla g 1 and anti-Per a 1 mAbs and a panel of human IgE antibodies showed that the protein expressed by these clones was Per a 1. Sequence homology searches showed that Per a 1 was homologous to 5 previously reported, but unidentified, sequences from B germanica and P americana. These sequences encoded proteins with multiple molecular sizes containing approximately 100 amino acid repeats. The Per a 1 sequence also showed 31% identity to a mosquito precursor protein, ANG12, which may be involved in digestion. The Per a 1 cDNA was expressed in Pichia pastoris to produce purified recombinant allergen (yield, 14 mg/L). CONCLUSION The results define the molecular structure and antigenic relationships between a new family of cross-reactive "Group 1" allergens produced by both P americana and B germanica. These recombinant allergens and specific mAbs will provide tools to improve the diagnosis and treatment of allergic diseases caused by cockroaches.