The wild-type Autographa californica nuclear polyhedrosis virus induces apoptosis of Spodoptera littoralis cells

Abstract

Spodoptera littoralis cells infected with the Autographa californica multiple nuclear polyhedrosis virus (AcMNPV) yielded significantly lower budded virus titers than Spodoptera frugiperda-infected cells and produced very low levels of polyhedrin. Relative to AcMNPV-infected S. frugiperda SF9 cells viral DNA replication was severely reduced in Spodoptera littoralis SL2 cells. Microscopic examination of SL2-infected cells revealed progressive cell blebbing starting at 6-8 hr postinfection and culminating in total cell destruction at 24 hr postinfection. The data suggested that AcMNPV-infected SL2 cells undergo apoptosis. The occurrence of an active apoptotic process in the infected cells was confirmed by: (1) observation of fragmentation of the cell nuclei stained with the specific fluorescent dye DAPI (4',6'-diamidino-2-phenylindole) and (2) the presence of low-molecular-weight DNA oligomers. Neither SL2 cells infected with S. littoralis nuclear polyhedrosis virus (SINPV) nor SF9 cells infected with AcMNPV, respectively, showed nuclear fragmentation or oligonucleosomal ladder formation.