Japanese encephalitis virus/yellow fever virus chimera is safe and confers full protection against yellow fever virus in intracerebrally challenged mice.

Yellow fever (YF) is an acute viral haemorrhagic disease caused by the yellow fever virus (YFV), which remains a potential threat to public health. The live-attenuated YF vaccine (17D strain) is a safe and highly effective measure against YF. However, increasing adverse events have been associated with YF vaccinations in recent years; thus, safer, alternative vaccines are needed. In this study, using the Japanese encephalitis live vaccine strain SA14-14-2 as a backbone, a novel chimeric virus was constructed by replacing the pre-membrane (prM) and envelope (E) genes with their YFV 17D counterparts.The chimeric virus exhibited a reduced growth rate and a much smaller plaque morphology than did either parental virus. Furthermore, the chimera was much less neurovirulent than was YF17D and protected mice that were challenged with a lethal dose of the YF virus. These results suggest that this chimera has potential as a novel attenuated YF vaccine.