SUPERINFECTION-INDUCED APOPTOSIS AND ITS CORRELATION WITH THE REDUCTION OF VIRAL PROGENY IN CELLS PERSISTENTLY INFECTED WITH HZ-1 BACULOVIRUS

Differential induction of necrosis or apoptosis was found upon challen ge of cells of the insect Spodoptera frugiperda productively or persis tently infected with Hz-1 baculovirus, respectively. Unlike parental S F9 cells, which were essentially all killed by virally induced necrosi s, persistently infected cells underwent a process of massive cell dea th by apoptosis; cells which were not killed by apoptosis then reestab lished a cell monolayer. Upon viral challenge, the yield of viral prog eny was reduced greatly in persistently virus-infected cells but not i n parental cells. Immunolabelling of individual cells revealed that up on viral challenge, production of viral progeny was detectable only in necrotic cells and not in apoptotic cells. These results indicated th at induction of apoptosis greatly reduces the yield of viral progeny i n cells persistently infected with Hz-1 baculovirus. This is the first report of apoptosis induction in persistently infected cells upon vir al superinfection.