Affection Of Infection Of Autographa Californica Nucleopolyhdrovirus On Sf9 Cells Cycle

Baculovirus infection results in many inductive changes of cellular proteins and cellular structures and cellular biology chemistry events. Therefore, one goal of this study was to investigate the effect of baculovirus infection on the cell cycle of Spodoptera frugiperda IPLB-Sf21-AE clonal isolate 9 (Sf9) host cells. Since few data are available on the cell cycle of insect cells. The first task was to define Sf9 cell cycle kinetics. Flow cytometry analysis of the cell-cycle progression was performed in Sf9 cells infected AcNPV ( Autographa californica nucleopolyhedrovirus ) in the cultures. The cell cycle phase distribution of Sf9 cells grown in suspension culture was determined to be evenly distributed (20-30% of cells in G, phase, 30-40% in S phase, and 30-40% in G2/M phase), with the duration of GI phase and S phase and G2/M phase all being about 6 h and the whole time of the cell cycle was about 18 hours.When Sf9 cells were infected with AcNPV, approximately 80-90% of the cells were arrested in G2/M phase by 18-36 h p.i. Sf9 cells were infected with AcNPV during the Gi/S phase synchronized by drugs, and 70% of the cells progressed past the S phase, which were arrested in the G2/M phase, and 30% of the cells did not progressed past the S phase.Cells with 4N DNA content were observed in the Sf9 cultures infected with AcNPV. In AcNPV-infected cultures, cells with >4N DNA accumulated irrespective of the cell-cycle phase at infection, indicating that synthesis of DNA content occurred independently of cell-cycle phases in arrest. The study indicated that the DNA overaccumulated in AcNPV-infected cells with >4N DNA content was of viral origin.Association of the susceptibility of Sf9 cells to AcNPV infection with different phases of the cell cycle was studied in Sf9 cells.We found Sf9 cells synchronized in Gi/S phase are more susceptible to AcNPV infection than cells in other phases of the cell cycle. It is likely that the state of health and/or the phase of the host in the cell cycle has an important role in influencing the rate of temporal progression and the amount and form of progeny virus produced during baculovirus infection.The cell-cycle arrest of Sf9 cells was induced by AcNPV infection.Maybe the immediate-early genes of AcNPV played key roles on the arrest. The transfection of Sf9 cells with AcNPV iel gene showed that it was sufficient to induce arrest of the cell cycle and apoptosis, which were characterized by flow cytometry analysis. Moreover, the transfection of Sf9 cells with DNAs of HaNPV gene or S1NPV gene or SfaNPV gene induced arrest of the cell cycle and apoptosis, too. And the apoptosis rate of Sf9 cells induced by the transfection with AcNPV iel gene was higher than with DNAs of HaNPV gene or S1NPV gene or SfaNPV gene.Concomitant with the viral-induced arrest in G2/M phase, high levels of both cyclinB and cyclinD3 were detected by 48 h p.i. These data suggest that the cell-cycle arrest in AcNPV -infected Sf9 cells is an event triggered early in infection by specific interaction of viral gene products with cellular compomets that regulate cell-cycle progression.