Polyacrylamide gel electrophoresis of baculovirus proteins: A simplified and sensitive modification for differentiating between isolates

Abstract

A rapid and sensitive modification of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of baculovirus structural proteins has been developed. Polyhedral inclusion bodies (PIBs) were pretreated with 1% SDS and 0.5% 2-mercaptoethanol (2-ME) for 30 min at pH 7.2, washed to remove soluble material, dissociated with Laemmli's sample buffer, and analyzed by SDS-PAGE. When the gels were stained with silver nitrate, as little as 48 μg of protein, comprising both polyhedrin and virion proteins, could be resolved on the same gel. Pretreatment with SDS and 2-ME eliminated the need to further purify PIBs by sucrose gradient centrifugation, since gel profiles of PIB proteins before and after such centrifugation were indistinguishable. The method was used to distinguish between the nuclear polyhedrosis viruses (NPVs) of the following species: Mamestra brassicae, Wiseana cervinata, Autographa californica, Mythimna convecta, Persectania dyscrita, Spodoptera exigua, S. frugiperda, Anthela varia, Pterolocera amplicornis, and Heliothis punctiger. Cross-transmission of A. californica NPV to H. punctiger and M. convecta and of M. convecta NPV to P. dyscrita was confirmed by analysis of progeny virus proteins.