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Journal of Virology, November 2001, p. 10912-10922, Vol. 75, No. 22
Department of Molecular Microbiology and
Immunology, St. Louis University Health Sciences Center, St. Louis,
Missouri 63104
Received 22 May 2001/Accepted 16 August 2001
A neuroadapted strain of yellow fever virus (YFV) 17D derived
from a multiply mouse brain-passaged virus (Porterfield
YF17D) was additionally passaged in SCID and normal mice. The virulence properties of this virus (SPYF) could be distinguished from
nonneuroadapted virus (YF5.2iv, 17D infectious clone) by decreased
average survival time in SCID mice after peripheral inoculation,
decreased average survival time in normal adult mice after
intracerebral inoculation, and occurrence of neuroinvasiveness in
normal mice. SPYF exhibited more efficient growth in peripheral tissues
of SCID mice than YF5.2iv, resulting in a more rapid accumulation of
virus burden, but with low-titer viremia, at the time of fatal
encephalitis. In cell culture, SPYF was less efficient in replication
than YF5.2iv in all cell lines tested. The complete nucleotide sequence
of SPYF revealed 29 nucleotide substitutions relative to YF5.2iv, and
these were distributed throughout the genome. There were a total of 13 predicted amino acid substitutions, some of which correspond to known
differences among the Asibi, French viscerotropic virus, French
neurotropic vaccine, and YF17D vaccine strains. The envelope (E)
protein contained five substitutions, within all three functional
domains. Substitutions were also present in regions encoding the NS1,
NS2A, NS4A, and NS5 proteins and in the 3' untranslated region (UTR).
Construction of YFV harboring all of the identified coding nucleotide
substitutions and those in the 3' UTR yielded a virus whose cell
culture and pathogenic properties, particularly neurovirulence and
neuroinvasiveness for SCID mice, generally resembled those of the
original SPYF isolate. These findings implicate the E protein and
possibly other regions of the genome as virulence determinants during
pathogenesis of neuroadapted YF17D virus in mice. The determinants
affect replication efficiency in both neural and extraneural tissues of
the mouse and confer some limited host-range differences in cultured
cells of nonmurine origin.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.22.10912-10922.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Neuroadapted Yellow Fever Virus 17D: Genetic and Biological
Characterization of a Highly Mouse-Neurovirulent Virus and Its
Infectious Molecular Clone
*
Corresponding author. Mailing address: Department of
Molecular Microbiology and Immunology, St. Louis University Health
Sciences Center, 1402 S. Grand Ave., St. Louis, MO 63104. Phone: (314) 577-8447. Fax: (314) 773-3403. E-mail: chambetj{at}slu.edu.
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