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Journal of Virology, September 1998, p. 7357-7366, Vol. 72, No. 9
Department of Microbiology and Immunology,
School of Medicine, University of North Carolina at Chapel Hill,
Chapel Hill, North Carolina
Received 6 April 1998/Accepted 12 June 1998
Attachment of Sindbis virus to the cell surface glycosaminoglycan
heparan sulfate (HS) and the selection of this phenotype by cell
culture adaptation were investigated. Virus (TR339) was derived from a
cDNA clone representing the consensus sequence of strain AR339 (K. L. McKnight, D. A. Simpson, S. C. Lin, T. A. Knott,
J. M. Polo, D. F. Pence, D. B. Johannsen, H. W. Heidner, N. L. Davis, and R. E. Johnston, J. Virol.
70:1981-1989, 1996) and from mutant clones containing either
one or two dominant cell culture adaptations in the E2 structural
glycoprotein (Arg instead of Ser at E2 position 1 [designated TRSB])
or this mutation plus Arg for Ser at E2 114 [designated TRSB-R114]).
The consensus virus, TR339, bound to baby hamster kidney (BHK) cells
very poorly. The mutation in TRSB increased binding 10- to 50-fold, and
the additional mutation in TRSB-R114 increased binding 3- to 5-fold
over TRSB. The magnitude of binding was positively correlated with the
degree of cell culture adaptation and with attenuation of these viruses in neonatal mice. HS was identified as the attachment receptor for the
mutant viruses by the following experimental results. (i) Low
concentrations of soluble heparin inhibited plaque formation on and
binding of mutant viruses to BHK cells by >95%. In contrast, TR339
showed minimal inhibition at high concentrations. (ii) Binding and
infectivity of TRSB-R114 was sensitive to digestion of cell surface HS
with heparinase III, and TRSB was sensitive to both heparinase I and
heparinase III. TR339 infectivity was only slightly affected by either
digestion. (iii) Radiolabeled TRSB and TRSB-R114 attached efficiently
to heparin-agarose beads in binding assays, while TR339 showed
virtually no binding. (iv) Binding and infectivity of TRSB and
TRSB-R114, but not TR339, were greatly reduced on Chinese hamster ovary
cells deficient in HS specifically or all glycosaminoglycans. (v)
High-multiplicity-of-infection passage of TR339 on BHK cell cultures
resulted in rapid coselection of high-affinity binding to BHK cells and
attachment to heparin-agarose beads. Sequencing of the passaged virus
population revealed a mutation from Glu to Lys at E2 70, a mutation
common to many laboratory strains of Sindbis virus. These results
suggest that TR339, the most virulent virus tested, attaches to cells
through a low-affinity, primarily HS-independent mechanism. Adaptive
mutations, selected during cell culture growth of Sindbis virus,
enhance binding and infectivity by allowing the virus to attach by an
alternative mechanism that is dependent on the presence of cell surface
HS.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Adaptation of Sindbis Virus to BHK Cells Selects
for Use of Heparan Sulfate as an Attachment Receptor
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, University of North Carolina at Chapel
Hill, School of Medicine, Chapel Hill, NC 27599-7290. Phone: (919)
966-4026. Fax: (919) 962-8103. E-mail: wklimstr{at}med.unc.edu.
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