CfMNPV blocks AcMNPV-induced apoptosis in a continuous midgut cell line

Morphological and molecular changes produced by Autographa californica nuclear polyhedrosis virus (AcMNPV) infection in a permissive cell line, IPLB-SF-21AE (SF-21), of Spodoptera frugiperda and a nonpermissive cell line, FPMI-CF-203 (CF-203), of Choristoneura fumiferana are described. CF-203 cells inoculated with AcMNPV showed a DNA ladder and morphological changes such as plasma membrane granulation, blebbing, and nuclear fragmentation, which are characteristic of apoptosis. Typical virus replication and occlusion body (OB) production were seen in SF-21 cells inoculated with AcMNPV and no apoptosis-like symptoms were observed. mRNA for the apoptosis suppressor gene p35 was detected 9 hr later in AcMNPV-inoculated CF-203 cells than in SF-21 cells. Only a trace amount of mRNA for the AcMNPV-inhibitor of apoptosis homologue (Ac-iap) gene and no mRNAs for the late genes, AcMNPV-polyhedrin (Ac-polh) and AcMNPV-p10 (Ac-p10), were detected in AcMNPV-inoculated CF-203 cells. Inoculation of CF-203 cells with CfMNPV at least 12 hr prior to inoculation with AcMNPV prevented apoptosis-like cell death, and mRNAs far Ac-iap, Ac-polh, and Ac-p10 genes were expressed resulting in successful virus replication and OB production.