Construction, characterization and immunogenicity of recombinant yellow fever 17D-dengue type 2 viruses

Chimeric yellow fever (YF)-dengue type 2 (Den 2) viruses were constructed b y replacing the premembrane (prM) and envelope (E) genes of YF 17D virus wi th those from Den 2 virus strains of south-east Asian genotype. Whereas via ble chimeric viruses were successfully recovered when the YF 17D C gene and the Den 2 prM gene were fused at the signalase cleavage site, no virus cou ld be rescued from the constructions fused at the viral protease cleavage s ite. Unlike YF virus that replicated in all the cell lines tested and simil ar to the Den 2 virus, the recombinant viruses did not replicate in vaccine -production certified CEF and MRC5 cells. Besides, chimeric 17D/Den 2 virus es and their parental viruses reached similar growth titers in Vero and C6/ 36 cell cultures. Analysis of mouse neurovirulence, performed by intracereb ral inoculation, demonstrated that the 17D/Den 2 chimera is more attenuated in this system than the YF 17DD virus. Immunization of mice with this chim era induced a neutralizing antibody response associated with a partial prot ection against an otherwise lethal dose of mouse neurovirulent Den 2 NGC vi rus. Overall, these results provide further support for the use of chimeric viruses as an attractive methodology for the development of new live flavi virus vaccines. (C) 2001 Elsevier Science B.V. All rights reserved.