Expression profiling of baculovirus genes in permissive and nonpermissive cell lines.

The baculoviruses Bombyx mori nucleopolyhedrovirus (BmNPV) and Autographa californica multicapsid NPV (AcMNPV) are highly homologous at the genomic level, but they have essentially nonoverlapping host ranges. In order to characterize baculovirus replication in permissive and nonpermissive cell lines, the expression profiles of baculovirus-specific genes (at 2, 6, 12, 24, 36, 48 or 72 h post-infection) were examined in BmN (BmNPV-permissive) or Sf-9 (AcMNPV-permissive) cells that were inoculated with BmNPV or AcMNPV. Surprisingly, nearly all of the 154 genes of AcMNPV appeared to be expressed in both Sf-9 and BmN cells although the peak expression levels of these genes were delayed by roughly 12 h in the nonpermissive BmN cells. In addition, the expression levels of the very late AcMNPV polyhedrin and p10 genes were dramatically reduced in BmN cells, which presumably led to the inability of AcMNPV to form polyhedral inclusion bodies in BmN cells. Nearly all of the 136 genes of BmNPV appeared to be expressed in BmN cells, however, BmNPV gene expression was dramatically reduced in Sf-9 cells inoculated with BmNPV. Experiments in which BmNPV DNAs were transfected to Sf-9 cells suggested that this dramatic reduction in gene expression was not the result of poor attachment, penetration or uncoating of the BmNPV virion into Sf-9 cells. In conclusion, we established a system to monitor global gene expression patterns during baculovirus infection in permissive and nonpermissive cell lines. This system was used to identify global trends in the transcription of baculovirus genes during productive and nonproductive infection.