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Journal of Virology, August 2001, p. 7481-7488, Vol. 75, No. 16
Department of Pediatrics, Mount Sinai School
of Medicine, New York, New York 10029
Received 20 March 2001/Accepted 24 May 2001
The envelope of human parainfluenza virus type 3 (HPF3) contains
two viral glycoproteins, the hemagglutinin-neuraminidase (HN) and the fusion protein (F). HN, which is responsible for receptor
attachment and for promoting F-mediated fusion, also possesses
neuraminidase (receptor-destroying) activity. We reported previously that 4-guanidino-neu5Ac2en (4-GU-DANA) and related sialic
acid-based inhibitors of HPF3 neuraminidase activity also inhibit HN-mediated receptor binding and fusion processes not involving
neuraminidase activity. We have now examined this
mechanism, as well as neuraminidase's role in the viral
life cycle, using a neuraminidase-deficient HPF3
variant (C28a) and stable cell lines expressing C28a or wild-type (wt)
HN. C28a, which has a wt F sequence and two point mutations in the HN
gene corresponding to two amino acid changes in the HN protein, is the
first HPF3 variant with insignificant neuraminidase
activity. Cells expressing C28a HN did not bind erythrocytes at 4°C
unless pretreated with neuraminidase, but no such
pretreatment was required for hemadsorption activity (HAD) at 22 or
37°C. HAD was blocked by 4-GU-DANA, attesting to the ability of this
compound to inhibit HN's receptor-binding activity. C28a or wt plaque
enlargement, a process that involves cell-cell fusion and does
not depend on virion release, is diminished by the presence of
4-GU-DANA, confirming the inhibitory effect of 4-GU-DANA on the
fusogenic function of C28a HN. In C28a-infected cell monolayers, virion
release and thus multicycle replication are severely restricted. This
defect was corrected by supplementation of exogenous
neuraminidase and also by the addition of 4-GU-DANA; neuraminidase destroys the receptors whereby newly formed
C28a virions would remain attached to the cell surface, whereas
4-GU-DANA prevents the attachment itself, obviating the need for
receptor cleavage. In accord with the ability of 4-GU-DANA to prevent
attachment, the neuraminidase inhibitory effect of
4-GU-DANA on wt HPF3 did not diminish virion release into the medium.
Thus, it is by inhibition of viral entry and syncytium formation that
sialic acid analogs like 4-GU-DANA may counteract wt HPF3 infection.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.16.7481-7488.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Human Parainfluenza Virus Type 3 HN-Receptor Interaction: Effect
of 4-Guanidino-Neu5Ac2en on a Neuraminidase-Deficient Variant
*
Corresponding author. Mailing address: Department of
Pediatrics, Mount Sinai School of Medicine, 1 Gustave L. Levy Pl., New York, NY 10029. Phone: (212) 241-6930. Fax: (212) 426-4813. E-mail: Anne.moscona{at}mssm.edu.
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