Virus-Like Particle Vaccine Confers Protection against a Lethal Newcastle Disease Virus Challenge in Chickens and Allows a Strategy of Differentiating Infected from Vaccinated Animals

In this study, we developed Newcastle disease virus (NDV) virus-like particles (VLPs) expressing NDV fusion (F) protein along with influenza virus matrix 1 (M1) protein using the insect cell expression system. Specific-pathogen-free chickens were immu-nized with oil emulsion NDVVLP vaccines containing increasing dosages of VLPs (0.4, 2, 10, or 50g of VLPs/0.5-ml dose). Three weeks after immunization, the immunogenicity of the NDVVLP vaccines was determined using a commercial enzyme-linked immunosorbent assay (ELISA) kit, and a lethal challenge using a highly virulent NDV strain was performed to evaluate the protective efficacy of the NDVVLP vaccines. NDVVLP vaccines elicited anti-NDV antibodies and provided protection against a lethal challenge in a dose-dependent manner. Although the VLP vaccines containing 0.4 and 2g of VLPs failed to achieve high levels of protection, a single immunization with NDVVLP vaccine containing 10 or 50g could fully protect chick-ens from a lethal challenge and greatly reduced challenge virus shedding. Furthermore, we could easily differentiate infected from vaccinated animals (DIVA) using the hemagglutination inhibition (HI) test. These results strongly suggest that utilization of NDVVLP vaccine in poultry species may be a promising strategy for the better control of NDV. Newcastle disease virus (NDV), also known as avian paramyxovi-rus serotype 1 (APMV-1), is an enveloped nonsegmented negative-strand RNA virus which is a member of the genus Avulavirus in the family Paramyxoviridae (1). On the basis of their pathogenicity for chickens, specifically by the intracerebral patho