Abortive infection of the baculovirus Autographa californica nuclear polyhedrosis virus in Sf-9 cells after mutation of the putative DNA helicase gene.
Homologous recombination between the Autographa californica nuclear polyhedrosis virus (AcNPV) genome and a 0.6-kbp-long DNA fragment derived from the putative DNA helicase gene of Bombyx mori nuclear polyhedrosis virus generates eh2-AcNPV, an expanded-host-range AcNPV mutant (S. Maeda, S.G. Kamita, and A. Kondo, J. Virol. 67:6234-6238, 1993). After inoculation at a high multiplicity of infection (MOI), eh2-AcNPV replicates efficiently in both the Sf-9 (AcNPV-permissive) and BmN (non-AcNPV-permissive) cell lines. In this study, we found that after the inoculation of Sf-9 cells at a low MOI (i.e., 1 and 0.1 PFU per cell), the release of eh2-AcNPV virions was dramatically reduced (approximately 900- and 10,000-fold, respectively, at 72 h postinoculation) compared with that of wild-type AcNPV. In addition, the titer of eh2-AcNPV determined by plaque assay on Sf-9 cells was approximately 200-fold lower than that determined by plaque assay on BmN cells. Analyses of gene expression and viral DNA replication after low-MOI eh2-AcNPV inoculation of Sf-9 cells indicated that viral early genes were expressed normally. However, DNA replication and late-gene expression were significantly reduced. These findings suggested that abortive infection occurred at the stage of viral DNA replication in nearly all low-MOI eh2-AcNPV-infected Sf-9 cells. In the larvae of Spodoptera frugiperda, the organism from which Sf-9 cells are derived, the infectivity of eh2-AcNPV was lower than that of AcNPV; however, abortive infection was not found.
Kamita
S G
SG
Department of Entomology, University of California, Davis 95616, USA.
Maeda
S
S
D000818:Animals; D015152:Blotting, Northern; D012831:Bombyx; D002460:Cell Line; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D005260:Female; D015870:Gene Expression; D005814:Genes, Viral; D016679:Genome, Viral; D007700:Kinetics; D007814:Larva; D016296:Mutagenesis; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D010063:Ovum; D018411:Spodoptera / Q000821:virology; D014779:Virus Replication
D004265:DNA Helicases