PERSISTENT BACULOVIRUS INFECTION RESULTS FROM DELETION OF THE APOPTOTIC SUPPRESSOR GENE P35

Infection with the wild-type baculovirus Autographa californica multip le nuclear polyhedrosis virus (AcMNPV) results in complete death of Sp odoptera frugiperda (Sf) cells. However, infection of Sf cells with Ac MNPV carrying a mutation or deletion of the apoptotic suppressor gene p35 allowed the cloning of surviving Sf cells that harbored persistent viral genomes, Persistent infection established with the virus with p 35 mutated or deleted was blocked by stable transfection of p35 in the host genome or by insertion of the inhibitor of apoptosis (iap) gene into the viral genome. These artificially established persistently vir us-infected cells became resistant to subsequent viral challenge, and some of the cell lines carried large quantities of viral DNA capable o f early gene expression. Continuous release of viral progenies was evi dent in some of the persistently virus-infected cells, and transfectio n of p35 further stimulated viral activation of the persistent cells, including the reactivation of viruses in those cell lines without orig inal continuous virus release. These results have demonstrated the suc cessful establishment of persistent baculovirus infections under labor atory conditions and that their establishment may provide a novel cont inuous, nonlytic baculovirus expression system in the future.