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Journal of Virology, September 1998, p. 7341-7348, Vol. 72, No. 9
Institute of Molecular and Cellular Virology,
Friedrich-Loeffler-Institutes, Federal Research Centre for Virus
Diseases of Animals, D-17498 Insel Riems, Germany
Received 2 March 1998/Accepted 9 June 1998
Initiation of herpesvirus infection requires attachment of virions
to the host cell followed by fusion of virion envelope and cellular
cytoplasmic membrane during penetration. In several alphaherpesviruses,
glycoprotein C (gC) is the primary attachment protein, interacting with
cell-surface heparan sulfate proteoglycans. Secondary binding is
mediated by gD, which, normally, is also required for penetration.
Recently, we described the isolation of a gD-negative infectious
pseudorabies virus (PrV) mutant, PrV gD
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Infectivity of a Pseudorabies Virus Mutant Lacking
Attachment Glycoproteins C and D
Pass (J. Schmidt,
B. G. Klupp, A. Karger, and T. C. Mettenleiter, J. Virol. 71:17-24, 1997). In PrV gD
Pass, attachment and
penetration occur in the absence of gD. To assess the
importance of specific attachment for infectivity of PrV
gD
Pass, the gene encoding gC was deleted, resulting in
mutant PrV gCD
Pass. Deletion of both known
attachment proteins reduced specific infectivity compared to
wild-type PrV by more than 10,000-fold. Surprisingly, the
virus mutant still retained significant infectivity and could
be propagated on normal noncomplementing cells, indicating the presence
of another receptor-binding virion protein. Selection of bovine kidney
(MDBK) cells resistant to infection by PrV gCD
Pass
resulted in the isolation of a cell clone, designated NB, which was
susceptible to infection by wild-type PrV but refractory to infection
by either PrV gCD
Pass or PrV gD
Pass, a
defect which could partially be overcome by polyethylene glycol
(PEG)-induced membrane fusion. However, even after PEG-induced infection plaque formation of PrV gCD
Pass or PrV
gD
Pass did not ensue in NB cells. Also, phenotypic gD
complementation of PrV gCD
Pass or PrV gD
Pass rescued the defect in infection of NB cells but did not restore
plaque formation. Glycosaminoglycan analyses of MDBK and NB cells
yielded identical results, and NB cells were normally susceptible to
infection by other alphaherpesviruses as well as vesicular
stomatitis virus. Infectious center assays after PEG-induced infection of NB cells with PrV gD
Pass on MDBK cells
indicated efficient exit of virions from infected NB cells. Together,
our data suggest the presence of another receptor and
receptor-binding virion protein which can mediate PrV entry and
cell-to-cell spread in MDBK cells.
*
Corresponding author. Mailing address: Institute of
Molecular and Cellular Virology, Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17498 Insel Riems, Germany. Phone: 49-38351-7102. Fax: 49-38351-7151. E-mail:
Thomas.C.Mettenleiter{at}rie.bfav.de.
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