Development of an attenuated live vaccine candidate of duck Tembusu virus strain.

Highlights • The DTMUV virus strain was attenuated via passaging serially in chicken embryos and duck embryos alternately for 100 passages. • The 70th adapted strain, designated SDS-70, was used as the live attenuated vaccine candidate. • After immunization with SDS-70 strain, the ducklings obtained the protection of 100% against the attack of the SDS-10 virulent strain. • Substitutions of 33 base were present in the SDS-20/40/60/80/100 sequence, which included 15 neutral mutations and 18 amino acid mutations. Abstract Infection with duck Tembusu virus (DTMUV) can cause large economic losses to the duck-rearing industry in China. In this study, we isolated a virulent strain of DTMUV (SDS) from sparrows near a duck farm and attenuated it via serially passaging (alternately for 100 passages) in specific pathogen-free chicken and duck embryos. We attenuated the virus after the 60th passage (SDS-60), based on the production of embryos that were free of visible lesions and still alive. The 70th adapted strain (SDS-70), obtained with a virus titer of 10−2.46 EID 50 was chosen to be the live attenuated vaccine. After immunizing ducklings with the SDS-70 strain, they obtained 100% protection against infection by the SDS-10 virulent strain. Our data demonstrate that the vaccine can protect ducks from becoming infected with TMUV. Our study also shows that this newly developed attenuated vaccine candidate provides excellent immunogenicity, is safe, and has the potential to control DTMUV infections in ducks. [ABSTRACT FROM AUTHOR]