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Journal of Virology, September 1999, p. 7399-7409, Vol. 73, No. 9
Department of Molecular Pathology, The
Windeyer Institute of Medical Sciences, University College London,
London W1P 6DB, England
Received 25 February 1999/Accepted 7 June 1999
Herpes simplex virus (HSV) has often been suggested for development
as a vector, particularly for the nervous system. Considerable evidence
has shown that for use of HSV as a vector, immediate-early (IE) gene
expression must be minimized or abolished, otherwise such vectors are
likely to be highly cytotoxic. Mutations of vmw65 which abolish IE
promoter transactivating activity may also be included to reduce IE
gene expression generally. However, when vmw65 mutations are combined
with an IE gene deletion, such viruses are hard to propagate, even on
cells which otherwise complement the IE gene deletion effectively. We
have found that vmw65 mutants can be effectively grown on cell lines
expressing equine herpesvirus 1 gene 12, a non-HSV homologue of vmw65
with little sequence similarity to its HSV counterpart. This prevents
repair by homologous recombination of vmw65 mutations in the virus,
which would occur if mutations were complemented by vmw65 itself. The
gene 12 protein is not packaged into HSV virions, which is important if
viruses grown on such cells are to be used as vectors. These results
not only further strengthen the evidence for direct functional homology between and similar modes of action of the two proteins but have allowed the generation of gene 12-containing cell lines in which ICP4
and ICP27 expression is induced by virus infection (probably by ICP0)
and which give efficient growth of viruses deficient in ICP27, ICP4,
and vmw65 (the viruses also have ICP34.5/ORFP deleted). Efficient
growth of such viruses has not previously been possible. As these
viruses are highly deficient in IE gene expression generally, such
virus-cell line combinations may provide an alternative to HSV vectors
with deletions of all four of the regulatory IE genes which, for
optimal growth, require cell lines containing all four IE genes but
which are hard to generate due to the intrinsic cytotoxicity of each of
the proteins.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Equine Herpesvirus 1 Gene 12 Can Substitute for
vmw65 in the Growth of Herpes Simplex Virus (HSV) Type 1, Allowing the
Generation of Optimized Cell Lines for the Propagation of HSV
Vectors with Multiple Immediate-Early Gene Defects
*
Corresponding author. Mailing address: Department of
Molecular Pathology, The Windeyer Institute of Medical Sciences,
University College London, 46 Cleveland St., London W1P 6DB, England.
Phone: 44-171-504-9230. Fax: 44-171-387-3310. E-mail:
r.coffin{at}ucl.ac.uk.
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