Affiliation:
1. Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-8133
Abstract
ABSTRACT
Langat virus (LGT), the naturally attenuated member of the tick-borne encephalitis virus (TBEV) complex, was tested extensively in clinical trials as a live TBEV vaccine and was found to induce a protective, durable immune response; however, it retained a low residual neuroinvasiveness in mice and humans. In order to ablate or reduce this property, LGT mutants that produced a small plaque size or temperature-sensitive (
ts
) phenotype in Vero cells were generated using 5-fluorouracil. One of these
ts
mutants, clone E5-104, exhibited a more than 10
3
-fold reduction in replication at the permissive temperature in both mouse and human neuroblastoma cells and lacked detectable neuroinvasiveness for highly sensitive immunodeficient mice. The E5-104 mutant possessed five amino acid substitutions in the structural protein E and one change in each of the nonstructural proteins NS3 and NS5. Using reverse genetics, we demonstrated that a Lys
46
→Glu substitution in NS3 as well as a single Lys
315
→Glu change in E significantly impaired the growth of LGT in neuroblastoma cells and reduced its peripheral neurovirulence for SCID mice. This study and our previous experience with chimeric flaviviruses indicated that a decrease in viral replication in neuroblastoma cells might serve as a predictor of in vivo attenuation of the neurotropic flaviviruses. The combination of seven mutations identified in the nonneuroinvasive E5-104 mutant provided a useful foundation for further development of a live attenuated TBEV vaccine. An evaluation of the complete sequence of virus recovered from brain of SCID mice inoculated with LGT mutants identified sites in the LGT genome that promoted neurovirulence/neuroinvasiveness.
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
Cited by
44 articles.
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