A Bacterially Produced Virus Enhancing Factor from an Entomopoxvirus Enhances Nucleopolyhedrovirus Infection in Armyworm Larvae

Abstract

Using an Escherichia coli expression system, pGEX-2T, that expresses foreign sequences as fusion proteins with a glutathione S-transferase (GST) carrier, we have expressed a virus enhancing factor (EF) from Pseudaletia separata entomopoxvirus, which enhances P. unipuncta multi nucleopolyhedrovirus (PsunMNPV) infection in larvae of the armyworm, P. separata. The lysates of transformed E. coli cells, which were not active in enhancing PsunMNPV infection, became active when treated with either trypsin or thrombin. The GST–EF fusion protein in a lysate was purified with a bulk GST purification module and cleaved into the EF and GST moieties with thrombin. Removal of the GST moiety with glutathione–Sepharose 4B resulted in a highly purified EF preparation, which enhanced PsunMNPV infection in armyworm larvae and PsunMNPV fusion with an armyworm cell line, SIE-MSH-805-F.