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

Area of Science:

• Molecular Biology
• Virology
• Cell Biology

Background:

• Autographa californica nuclear polyhedrosis virus (AcMNPV) is a baculovirus that infects insect cells.
• Cellular responses to baculovirus infection can vary depending on the host cell permissivity.
• Apoptosis, or programmed cell death, is a critical cellular process that can be triggered by viral infections.

Purpose of the Study:

• To investigate the morphological and molecular changes induced by AcMNPV infection in permissive (Spodoptera frugiperda SF-21) and nonpermissive (Choristoneura fumiferana CF-203) cell lines.
• To compare the expression of apoptosis-related genes and viral genes in response to AcMNPV infection in both cell types.
• To determine if co-infection with another virus (CfMNPV) can alter the cellular response to AcMNPV in nonpermissive cells.

Main Methods:

• Inoculation of SF-21 and CF-203 cell lines with AcMNPV.
• Observation of morphological changes using microscopy.
• Analysis of DNA fragmentation (DNA laddering) as an indicator of apoptosis.
• Detection of specific viral and cellular gene messenger RNAs (mRNAs) using molecular techniques.
• Co-infection experiments with AcMNPV and Choristoneura fumiferana NPV (CfMNPV).

Main Results:

• AcMNPV infection induced apoptosis-like changes (DNA ladder, plasma membrane granulation, blebbing, nuclear fragmentation) in nonpermissive CF-203 cells.
• Permissive SF-21 cells supported typical AcMNPV replication and occlusion body production without apoptosis.
• Apoptosis suppressor gene p35 mRNA was detected later in infected CF-203 cells compared to SF-21 cells.
• Expression of inhibitor of apoptosis homologue (Ac-iap), polyhedrin (Ac-polh), and p10 (Ac-p10) genes was significantly reduced or absent in AcMNPV-infected CF-203 cells.
• Pre-inoculation of CF-203 cells with CfMNPV prevented AcMNPV-induced apoptosis and enabled viral replication and occlusion body production.

Conclusions:

• AcMNPV infection triggers apoptosis in nonpermissive CF-203 cells, characterized by specific morphological and molecular changes.
• The differential gene expression, particularly the reduced expression of viral late genes and altered apoptosis-related gene expression, contributes to the non-permissivity of CF-203 cells.
• Co-infection with CfMNPV can overcome AcMNPV-induced apoptosis in CF-203 cells, restoring viral replication and production, suggesting complex interactions between different NPVs in host cells.