Genotype-matched recombiant inactivated Newcastle disease virus vaccine confer protection against genotype Ⅻ challenge in geese with maternal antibodies

The majority of Newcastle disease virus (NDV) strains circulating in China, which exhibit a tendency toward increased virulence, are from genotype Ⅻ infections obtained from waterfowl. Based on our previous findings, the genotype Ⅻ strain E115 was non-pathogenic in geese but induced notable clinical symptoms in chickens without mortality. However, in recent years, we isolated the genotype Ⅻ strain E117 from dead geese and confirmed its lethality in geese through animal regression tests. Genotype-matched vaccination has been proposed as a potential solution. In this study, two NDV vaccination strains, mE115 and mE117, were rescued and evaluated for their resistance to wild-type virus attacks. In vivo analysis revealed that compared with that of the commercial vaccine group, the mE117, and mE115 immune groups exhibited higher antibody levels. The results of the immune protection test showed that the mE117 and mE115 vaccines prevented geese from dying when exposed to the E117 challenge. In contrast, the commercial vaccine group exhibited a survival rate of 62.5%. Furthermore, viral shedding drastically decreased to 0% in the mE117 and mE115 immunised groups, whereas virus shedding was observed in the visceral organs, oropharynx, or cloaca in the commercial vaccine group. Compared with that of the commercial vaccine, the two vaccine candidates developed in this study provided complete protection for geese against genotype Ⅻ challenges. These findings provide a foundation for the development of more effective vaccines to control Newcastle disease.