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Journal of Virology, March 2001, p. 2544-2556, Vol. 75, No. 6
Boyce Thompson Institute at Cornell
University1 and Department of Molecular
Biology and Genetics, Cornell
University,3 Ithaca, New York 14853, and
Novagen Inc., Madison, Wisconsin 537112
Received 11 September 2000/Accepted 11 December 2000
The Autographa californica multiple
nucleopolyhedrovirus (AcMNPV) GP64 protein is an essential
virion protein that is involved in both receptor binding and membrane
fusion during viral entry. Genetic studies have shown that GP64-null
viruses are unable to move from cell to cell and this results from a
defect in the assembly and production of budded virions (BV). To
further examine requirements for virion budding, we asked whether a
GP64-null baculovirus, vAc64
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.6.2544-2556.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
A GP64-Null Baculovirus Pseudotyped with Vesicular
Stomatitis Virus G Protein
, could be pseudotyped by
introducing a heterologous viral envelope protein (vesicular stomatitis
virus G protein [VSV-G]) into its membrane and whether the resulting
virus was infectious. To address this question, we generated a stably
transfected insect Sf9 cell line (Sf9VSV-G) that inducibly
expresses the VSV-G protein upon infection with AcMNPV
Sf9VSV-G and Sf9 cells were infected with
vAc64
, and cells were monitored for infection and for
movement of infection from cell to cell. vAc64
formed
plaques on Sf9VSV-G cells but not on Sf9 cells, and plaques
formed on Sf9VSV-G cells were observed only after prolonged
intervals. Passage and amplification of vAc64
on
Sf9VSV-G cells resulted in pseudotyped virus particles that
contained the VSV-G protein. Cell-to-cell propagation of
vAc64
in the G-expressing cells was delayed in comparison
to wild-type (wt) AcMNPV, and growth curves showed that
pseudotyped vAc64
was generated at titers of
approximately 106 to 107 infectious units
(IU)/ml, compared with titers of approximately 108 IU/ml
for wt AcMNPV. Propagation and amplification of pseudotyped vAc64
virions in Sf9VSV-G cells suggests that
the VSV-G protein may either possess the signals necessary for
baculovirus BV assembly and budding at the cell surface or may
otherwise facilitate production of infectious baculovirus virions. The
functional complementation of GP64-null viruses by VSV-G protein was
further demonstrated by identification of a
vAc64
-derived virus that had acquired the G gene through
recombination with Sf9VSV-G cellular DNA. GP64-null viruses
expressing the VSV-G gene were capable of productive infection,
replication, and propagation in Sf9 cells.
*
Corresponding author. Mailing address: Boyce Thompson
Institute at Cornell University, Tower Rd., Ithaca, NY 14853. Phone and
fax: (607) 254-1366. E-mail: gwb1{at}cornell.edu.
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