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Journal of Virology, January 2001, p. 934-942, Vol. 75, No. 2
OraVax, Inc., Cambridge, Massachusetts
02139,1 and Department of Molecular
Microbiology and Immunology, St. Louis University Health Sciences
Center, St. Louis, Missouri 631042
Received 11 July 2000/Accepted 11 October 2000
A yellow fever virus (YFV)/Japanese encephalitis virus (JEV)
chimera in which the structural proteins prM and E of YFV 17D are
replaced with those of the JEV SA14-14-2 vaccine strain is under
evaluation as a candidate vaccine against Japanese encephalitis. The
chimera (YFV/JEV SA14-14-2, or ChimeriVax-JE) is less neurovirulent than is YFV 17D vaccine in mouse and nonhuman primate models (F. Guirakhoo et al., Virology 257:363-372, 1999; T. P. Monath et al., Vaccine 17:1869-1882, 1999). Attenuation depends on the presence of the JEV SA14-14-2 E protein, as shown by the high neurovirulence of
an analogous YFV/JEV Nakayama chimera derived from the wild JEV
Nakayama strain (T. J. Chambers, A. Nestorowicz, P. W. Mason, and C. M. Rice, J. Virol. 73:3095-3101, 1999). Ten amino
acid differences exist between the E proteins of ChimeriVax-JE and the
YFV/JEV Nakayama virus, four of which are predicted to be neurovirulence determinants based on various sequence comparisons. To
identify residues that are involved in attenuation, a series of
intratypic YFV/JEV chimeras containing either single or multiple amino
acid substitutions were engineered and tested for mouse neurovirulence.
Reversions in at least three distinct clusters were required to restore
the neurovirulence typical of the YFV/JEV Nakayama virus. Different
combinations of cluster-specific reversions could confer
neurovirulence; however, residue 138 of the E protein (E138) exhibited a dominant effect. No single amino acid
reversion produced a phenotype significantly different from that of the ChimeriVax-JE parent. Together with the known genetic stability of the
virus during prolonged cell culture and mouse brain passage, these
findings support the candidacy of this experimental vaccine as a novel
live-attenuated viral vaccine against Japanese encephalitis.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.2.934-942.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Molecular Basis for Attenuation of Neurovirulence
of a Yellow Fever Virus/Japanese Encephalitis Virus Chimera
Vaccine (ChimeriVax-JE)
*
Corresponding author. Mailing address: Department of
Molecular Microbiology and Immunology, St. Louis University Health
Sciences Center, 1402 S. Grand Blvd., St. Louis, MO 63104. Phone: (314) 577-8447. Fax: (314) 773-3403. E-mail: chambetj{at}slu.edu.
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