The Antigenicity And Immunogenicity Of JEV-YFV Chimeric Virus

To develop new attenuated live vaccine of the Yellow Fever virus, chimeric virus rYJ based on the backbone vector of Japanese encephalitis virus was constructed and evaluated for the antigenicity and immunogenicity. Based on the two-plasmid system, the prM-E genes of the vaccine strain YF-17D were chosen to replace the reciprocal genes of JEV vaccine strain SA14-14-2. After transfection into the Vero cells, the rescued chimerica viruses were tested for infectivities by plaque assay and then were analyzed for its antigenicity and immunogenicity by neutralization test, immunology test, neuroinvasiveness and neurovirulence test in mice, ect. The connected products recovered viable chimeras after direct transfection into the cells at high titers of 1.39×107PFU/mL. The plaque size of the new virus displayed the same needletip-like shape as that of the parental YF-17D, but smaller than that of SA 14-14-2. It was confirmed that the recovered viruses were JEV-YFV chimerica viruses by serological methods and named rYJ. Similar to YF-17D vaccine strain, rYJ showed no neuroinvasiveness, but relatively high neurovirulence in weanling mice. All mice immunized with rYJ or YF-17D seroconverted and the neutralization titers were>1:40. More importantly, the rYJ vaccine conferred 100% protection against the challenge of 100000 LD50 of YFV. These data further supported the application of SA14-14-2 virus as a backbone carrier for construction of new type chimeras with other flavivirus. The chimeric virus rYJ has good antigenicity and immunogenicity to serve as a vaccine candidate. But for the sake of safety, attenuation of rYJ, especially in the neurovirulence in weanling mice, should be considered for further research, such as changing the E gene by point mutation.