Identification of aldolase and pyruvate kinase as novel cockroach allergens, Per a 21 and Per a 22.

Background: Exposure to cockroach allergens is associated with an increased risk of allergy. Currently, 20 cockroach allergen groups have been identified, in which Per a 13 was reported by our group. However, the diverse sensitization profiles require comprehensive characterization of cockroach allergens. We previously found that there existed two undescribed allergens in the American cockroach that merits further study.

Methods: The cDNA encoding the two novel allergens was cloned based on the identified peptides and transcriptomic results of the American cockroach. Both the natural and recombinant molecules were purified and characterized using SDS-PAGE, size exclusion chromatography, and periodic acid-Schiff staining. Their allergenicities were characterized and compared with those of Per a 13 and cockroach extracts.

Results: Two novel allergens belonging to fructose bisphosphate aldolase and pyruvate kinase were first identified in the American cockroach, they were designated as Per a 21 and Per a 22 in the WHO/IUIS Allergen Nomenclature database. The IgE-binding ELISA showed that 48 (62%) and 44 (57%) of the 77 cockroach allergic patients' sera were positive for natural and recombinant Per a 21, respectively, while 55 (71%) and 56 (73%) sera were positive for natural and recombinant Per a 22, respectively. Per a 21 and Per a 22 were recognized by 83% of the cockroach-IgE positive sera.

Conclusions: We identified two novel inhalant allergens (Per a 21 and Per a 22) in the American cockroach. These findings enrich the information on allergenic components and could be useful in developing allergen panels for molecular diagnosis of cockroach allergy.