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J. Virol., Aug 1996, 5123-5130, Vol 70, No. 8
A Lu and LK Miller
The host cell-specific factor 1 gene (hcf-1) of the baculovirus Autographa
californica nuclear polyhedrosis virus (AcMNPV) is required for the
efficient replication and/or stability of reporter plasmids carrying an
AcMNPV-derived origin of DNA replication in a cell-specific manner; hcf-1
is required for reporter plasmid replication or stability in TN-368 cells,
a cell line derived from the cabbage looper Trichoplusia ni, but not in
IPLB-SF-21 (SF-21) cells, a cell line derived from the fall armyworm
Spodoptera frugiperda (A. Lu and L. K. Miller, J. Virol. 69:6265-6272,
1995). To further define the function of hcf-1, recombinant viruses with
null mutations in hcf-1 were constructed in SF-21 cells and the phenotype
of the mutants was determined in selected cell lines as well as in insect
larvae. In S.frugiperda larvae and SF-21 cells, the phenotype of hcf-1
mutants was indistinguishable from that of wild-type AcMNPV. In T. ni
larvae as well as T. ni-derived cell lines, hcf-1 mutants exhibited a
mutant phenotype. In TN-368 cells, the replication of hcf-1 mutants was
extremely impaired; the phenotype included a defect in viral DNA
replication, late gene transcription, and virus production as well as a
complete cessation of host and viral protein synthesis. In another cell
line derived from T. ni, the BTI-TN5B1-4 cell line, the hcf-1 mutants
exhibited a less severe phenotype. In T. ni larvae, the infectivity of the
budded form of hcf-1 mutants was decreased significantly (50-fold),
although no difference in the oral infectivity of the occluded form was
observed. T. ni larvae infected with hcf-1 mutants by either oral or
hemocoelic routes, however, died 20 to 30% more slowly than those infected
with wild-type AcMNPV. These data indicate that there is a host-specific
requirement for hcf-1 and that it exerts cell line- specific effects and
possibly tissue-specific effects on the rate at which the virus replicates,
thereby affecting the virulence of the virus in a species-specific manner.
Copyright © 1996, American Society for Microbiology
Species-specific effects of the hcf-1 gene on baculovirus virulence
Department of Entomology, The University of Georgia, Athens 30602, USA.
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