Biologic potency and immunoblotting studies of extracts of three cockroach species

Although cockroaches are responsible for severe allergic disease, cockroach extracts are not yet standardized by the ID50EAL method, nor have the allergens been completely characterized.

To determine biologic potency and immunoblotting patterns of whole-body extracts of three cockroach species: Periplaneta americana, Blattella germanica, and Blatta orientalis.

Twenty-four subjects puncture test positive to mixed cockroach extract were puncture tested with the three extracts. Fourteen qualified for endpoint titration testing by the ID50EAL method to P. americana with a sum of erythema (sigma E) > or = 20 mm by puncture testing, while 13 qualified for B. germanica and 12 qualified for B. orientalis.

The mean D50s were 9.67 +/- 1.33 (mean +/- SD) for P. americana, 10.24 +/- 1.16 for B. germanica, and 10.36 +/- 1.40 for B. orientalis, resulting in a potency of 1000 BAU/mL for each extract. Omitting data from subjects with puncture sigma E < 30 mm did not change the calculated potency. Sixteen serum specimens revealed up to 17 bands with molecular weight 14 to 263 kD by SDS-PAGE immunoblotting. Four specimens showed no bands; of these, one had a positive RAST only to P. americana and one only to B. germanica. There was no correlation between number of bands or RAST counts with D50.

IgE immunoblots of cockroach-allergic patients vary considerably as to the number and intensity of bands. Most patients react similarly to all three species. Current nonstandardized products (1:10 wt/vol) in glycero-Coca's solution appear to contain approximately 1000 BAU/mL. Ideally these extracts should be more potent, eg, 10,000 BAU/mL.