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Journal of Virology, December 1999, p. 9832-9842, Vol. 73, No. 12
Department of Biochemistry, University of
Oxford, Oxford OX1 3QU, and U.K. and NERC Institute of Virology and
Environmental Microbiology, Oxford OX1 3SR, United
Kingdom,1 and Department of
International Health, University of Alabama at Birmingham,
Birmingham, Alabama 352942
Received 20 April 1999/Accepted 18 August 1999
Segment 2 of bluetongue virus (BTV) serotype 10, which encodes the
outer capsid protein VP2, was tagged with the S-peptide fragment of
RNase A and expressed by a recombinant baculovirus. The recombinant
protein was subsequently purified to homogeneity by virtue of the S
tag, and the oligomeric nature of the purified protein was determined.
The data obtained indicated that the majority of the protein forms a
dimer and, to a lesser extent, some trimer. The recombinant protein was
used to determine various biological functions of VP2. The purified VP2
was shown to have virus hemagglutinin activity and was antigenically
indistinguishable from the VP2 of the virion. Whether VP2 is
responsible for BTV entry into permissive cells was subsequently
assessed by cell surface attachment and internalization studies with an
immunofluorescence assay system. The results demonstrated that VP2
alone is responsible for virus entry into mammalian cells. By
competition assay, it appeared that both VP2 and the BTV virion
attached to the same cell surface molecule(s). The purified VP2 also
had a strong affinity for binding to glycophorin A, a sialoglycoprotein
component of erythrocytes, indicating that VP2 may be responsible for
BTV transmission by the Culicoides vector to vertebrate
hosts during blood feeding. Further, by various enzymatic treatments of
BTV-permissive L929 cells, preliminary data have been obtained which
indicated that the BTV receptor molecule(s) is likely to be a
glycoprotein and that either the protein moiety of the glycoprotein or
a second protein molecule could also serve as a coreceptor for BTV infection.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Expression and Functional Characterization of
Bluetongue Virus VP2 Protein: Role in Cell Entry
*
Corresponding author. Mailing address: NERC Institute
of Virology and Environmental Microbiology, Mansfield Rd., Oxford OX1 3SR, United Kingdom. Phone: 01865 281640. Fax: 01865 281696. E-mail: por{at}mail.nerc-oxford.ac.uk.
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