Egress of budded virions of Autographa californica nucleopolyhedrovirus does not require activity of Spodoptera frugiperda HSP/HSC70 chaperones

• Infection cycle of AcMNPV depends on the chaperone activity of host HSP/HSC70s.
• Expression of viral proteins of AcMNPV requires activity of chaperones HSP/HSC70s.
• Egress of budded virions of AcMNPV does not depend on activity of host HSP/HSC70s.

The induction of heat shock proteins in baculovirus infected cells is well documented. However a role of these chaperones in infection cycle remains unknown. The observation that HSP70s are associated with virions of different baculoviruses reported by several researchers suggests that HSPs might be structural components of viruses or involved in virion assembly. These hypotheses were examined by using a novel inhibitor of the ATPase and chaperoning activity of HSP/HSC70s, VER-155008. When VER-155008 was added early in infection, the synthesis of viral proteins, genome replication and the production of budded virions (BV) were markedly inhibited indicating the dependence of virus reproduction on host chaperones. However, BV production was unaffected when VER-155008 was added in the mid-replication phase which is after accumulation of products required for completion of the viral DNA replication. These results suggest that the final stages in assembly of BV and their egress from cells do not depend on chaperone activity of host HSP/HSC70s.