Abstract
A recombinant Bombyx mori nucleopolyhedrovirus (BmNPV), vBmΔpolh/lacZ/hrf1 (vBm/hrf1), that possessed the hrf-1 (host range factor 1) gene derived from Lymantria dispar multicapsid NPV (LdMNPV) was generated and examined for its biological properties in nonpermissive L. dispar Ld652Y cells. Although budded virus (BV) production was undetectable in vBm/hrf1-infected Ld652Y cells under the conditions used, a significant amount of BVs were yielded in Ld652Y cells transfected with vBm/hrf1 DNA, while transfection of DNA from a control recombinant BmNPV, vBmΔpolh/lacZ (vBm), that did not possess the hrf-1 gene, produced no detectable BVs in Ld652Y cells. BV yields increased when vBm/hrf1 DNA-transfected Ld652Y cells were cotransfected with a plasmid expressing HRF-1. Immunoblot analysis showed that viral structural proteins were produced in vBm/hrf1-infected Ld652Y cells, while viral structural proteins were not detected in vBm-infected Ld652Y cells. Pre-transfection of Ld652Y cells with a plasmid expressing HRF-1 increased viral structural proteins produced in vBm/hrf1-infected Ld652Y cells. No difference was observed between vBm/hrf and vBm in viral DNA replication in infected Ld652Y cells, indicating no direct effects of hrf-1 on viral DNA replication. These results indicate that HRF-1 expressed from the hrf-1 gene embedded within the vBm/hrf1 genome functions to preclude global protein synthesis shutdown and aids the vBm/hrf1 replication in Ld652Y cells, providing additional evidence for the hypothesis that HRF-1 is an essential viral factor commonly required for NPVs to replicate productively in Ld652Y cells.
© 2006 by Japan Academic Association for Copyright Clearance (Except in the USA), Copyright Clearance Center, Inc. (In the USA)
