Comparison of allergenic components between German cockroach whole body and fecal extracts

Background: Cockroaches have been demonstrated to be an etiologic factor in allergic diseases. Further, sensitivity to cockroach places patients with asthma at risk for exacerbations that require emergency medical care. Objective: This study compared the differences in allergenic components bet ween German cockroach whole body and German cockroach fecal extracts (GWBE and GFE). Methods: Patients with asthma and/or allergic rhinitis were skin prick test ed with German cockroach extract (Bayer Corporation, West Haven, CT). Serum specimens from these patients, 25 with positive skin tests and 8 with nega tive tests, were used for the ELISA and immunoblot experiments. Results: By ELISA, 72% (18 of 25) and 60% (15 of 25) of positive responders ' sera showed IgE antibodies to GWBE and GFE, respectively, and the IgE lev els to GWBE were highly correlated with those to GFE (r = .84, P < .01). In inhibition ELISA experiments, extensive cross-reactivity was observed betw een GWBE and GFE, slight cross-reactivity between GWBE and Dermatophagoides farinae, and no cross-reactivity between GFE and D. farinae. The two-site monoclonal antibody ELISA detected more of the German cockroach major aller gens in GFE compared with GWBE; 6.2 times (2420 vs 390 U/mL) for Bla g 1 an d 3 times (15.32 vs 5.07 <mu>g/mL) for Bla g 2. In the immunoblot compariso n of patients' sera, the IgE antibodies binding to GWBE were apparently dif ferent from those binding to GFE in all the positive responders' sera; eg, 50% or more of the 25 positive responders' sera reacted to 43- to 67-kDa pr oteins in GWBE and to 28- to 30-kDa proteins in GFE, respectively. No IgE a ntibodies bound to components in GWBE and GFE in the 8 negative responders' sera. Conclusions: There are major differences between the allergenic components of GWBE and GFE. Based on the amounts of major allergens (Bla g 1, Bla g 2) , German cockroach feces are a more important source of allergen than the w hole body in respiratory allergic diseases.