Tembusu virus-vectored chimeric vaccine induces potent neutralizing antibody response against West Nile virus in ducks.

West Nile virus (WNV) is a zoonotic, mosquito-borne flavivirus with birds as its primary reservoir host. Infection of domestic ducks leads to disease, decreased egg production, and mortality, highlighting the need for an effective WNV vaccine for ducks. In this study, several live-attenuated chimeric vaccine candidates were engineered with WNV pre-Membrane (prM) and Envelope (E) genes in the backbone of the duck Tembusu virus (TMUV) vaccine strain FX2010-180P. Two mutations in E (D120N and S156P) were introduced to alter glycosylation and reduce virulence. In mice, the vaccine candidates 180P/WNV-prM-E, 180P/WNV-prM-ED120N and 180P/WNV-prM-ES156P exhibited high neurovirulence via intracranial inoculation, but were safe when administered intramuscularly with a dose of 104 TCID50. Neutralizing antibody levels after a single intramuscular dose were modest. In ducks, low viraemia was detected in all groups of intramuscularly inoculated ducks at 2 dpi but the virus was cleared at 3 dpi. Low virus titers were detected in the spleen of 2 out of 3 ducks in the 180P/WNV-prM-E group and 1out of 3 ducks in the 180P/WNV-prM-ES156P group, but not in the 180P/WNV-prM-ED120N group. All vaccinated ducks developed strong neutralizing antibody responses by day 14, with 180P/WNV-prM-E inducing the highest neutralization levels. This study supports the use of the TMUV vaccine strain as a platform for developing live-attenuated, chimeric flavivirus vaccines against WNV in ducks.