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Journal of Virology, April 2000, p. 3353-3365, Vol. 74, No. 7
Graduate Institute of Life Science, National
Defense Medical Center and Institute of Molecular Biology, Academia
Sinica, Taipei, Taiwan, Republic of China,1 and
Australian Animal Health Laboratory, CSIRO Animal Health,
Geelong, Victoria, Australia2
Received 30 September 1999/Accepted 4 January 2000
An immunodominant antigen, p35, is expressed on the envelope of
intracellular mature virions (IMV) of vaccinia virus. p35 is encoded by
the viral late gene H3L, but its role in the virus life cycle is not
known. This report demonstrates that soluble H3L protein binds to
heparan sulfate on the cell surface and competes with the binding of
vaccinia virus, indicating a role for H3L protein in IMV adsorption to
mammalian cells. A mutant virus defective in expression of H3L
(H3L
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Vaccinia Virus Envelope H3L Protein Binds to Cell Surface
Heparan Sulfate and Is Important for Intracellular Mature Virion
Morphogenesis and Virus Infection In Vitro and In Vivo
) was constructed; the mutant virus has a small
plaque phenotype and 10-fold lower IMV and extracellular enveloped
virion titers than the wild-type virus. Virion morphogenesis is
severely blocked and intermediate viral structures such as viral
factories and crescents accumulate in cells infected with the
H3L
mutant virus. IMV from the H3L
mutant
virus are somewhat altered and less infectious than wild-type virions.
However, cells infected by the mutant virus form multinucleated syncytia after low pH treatment, suggesting that H3L protein is not
required for cell fusion. Mice inoculated intranasally with wild-type
virus show high mortality and severe weight loss, whereas mice infected
with H3L
mutant virus survive and recover faster,
indicating that inactivation of the H3L gene attenuates virus virulence
in vivo. In summary, these data indicate that H3L protein mediates
vaccinia virus adsorption to cell surface heparan sulfate and is
important for vaccinia virus infection in vitro and in vivo. In
addition, H3L protein plays a role in virion assembly.
*
Corresponding author. Mailing address: Institute of
Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan 11529, Republic of China. Phone: 886-2-2789-9230. Fax: 886-2-2782-6085. E-mail: mbwen{at}ccvax.sinica.edu.tw.
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