Identification of important allergens in German cockroach extracts by sodium dodecylsulfate-polyacrylamide gel electrophoresis and western blot analysis.

Abstract

Despite recent advances in the purification and characterization of cockroach allergens, identification of clinically important allergens and their source have not been completely elucidated. This study investigated the allergen content of German cockroach (Blattella germanica) whole body (GWBE) and fecal (GFE) extracts. Sera from 37 subjects with asthma, with positive skin test results to cockroach, were used for RAST and Western blot (after sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE] under reducing conditions); this serum panel is the largest used to date for cockroach allergen analysis. RAST reactivity to GWBE and GFE were highly correlated (r = 0.882, p < 0.001). SDS-PAGE and Western blotting showed that GWBE and GFE had similar patterns of IgE binding. Furthermore, Western blot inhibition investigations revealed that either GWBE or GFE could almost completely inhibit the reactivity of the other extract, SDS-PAGE and Western blotting demonstrated in both extracts numerous bands that displayed a high prevalence of IgE binding. Protein bands at 67, 50, 45, and 36 kd bound more than 50%, and the band at 60 kd bound approximately 80% of the sera tested. In summary, this investigation identified German cockroach allergens, established their relative importance by prevalence of reactivity to a large serum panel, and demonstrated that cockroach feces possess significant allergenic activity. Five allergens identified demonstrated reactivity with up to 50% to 80% of the 37 subjects' sera tested.