Allergenicity of Sigma and Delta Class Glutathione S-Transferases from the German Cockroach

Abstract

Background: Cockroach glutathione S-transferases (GSTs) are known to elicit strong IgE responses. This study was undertaken to compare the IgE reactivity of German cockroach GSTs, Bla g 5 (σ class) and δ class GST (BgGSTD1). Methods: Full-length Bla g 5 and BgGSTD1 were cloned, and their recombinant proteins were expressed and purified. Their IgE reactivities and cross-reactivities were examined by ELISA using sera from cockroach-sensitized subjects. Results: A predominant variant of Bla g 5 cDNA has amino acid substitutions at positions 10 (C to F) and 42 (N to K). BgGSTD1 has substitutions at positions 27 (E to N) and 207 (K to R). Sera from cockroach-sensitized patients showed 20.5% IgE reactivity to Bla g 5 and 17.9% IgE reactivity to BgGSTD1. However, inhibition studies using 1 serum sample with the highest IgE reactivity showed limited cross-reactivity. Conclusions: IgE-binding frequency to the cockroach GSTs was low, but the titer of IgE reactivity was strong in some sera. The inclusion of different classes of GSTs could be helpful for the delicate diagnosis and immunotherapy of cockroach allergy.