Apoptosis resulting from superinfection of Heliothis zea virus 1 is inhibited by p35 and is not required for virus interference.

Superinfection of Spodoptera frugiperda insect cells that are persistently infected with Heliothis zea 1 (Hz-1) virus induces general cellular apoptosis and subsequently results in homologous virus interference. Since apoptosis correlates closely with both a significant decrease in yield of virus progeny and expansion of virus infection among cells, further experiments were designed to verify the direct association of apoptosis with homologous interference. It was found that superinfection-induced apoptosis can be efficiently blocked by the stable transfection of p35 into cells before or after the establishment of persistent virus infection. However, persistently infected cells are still strongly resistant to the challenge of Hz-1 virus, indicating that the induction of apoptosis is not essential for the resulting homologous Hz-1 virus interference. Replication and transcription of viral genomes are greatly retarded upon Hz-1 virus superinfection of persistently infected cells, whether stably transfected with p35 or not, suggesting that upon superinfection, the decreasing yield of virus progeny in these persistently infected cells is caused by a blockage early after virus infection.