Recombinant Newcastle disease virus (NDV) La Sota expressing the haemagglutinin-neuraminidase protein of genotype VII NDV shows improved protection efficacy against NDV challenge

Intensive vaccination strategies against Newcastle disease (ND) have been implemented in many countries for a long time, but ND outbreaks still occur frequently, with most isolates belonging to genotype VII of Newcastle disease virus (NDV). Many researchers have revealed that vaccines closely matched to epidemic viruses provide better protection. Therefore, using a previously established reverse genetics system, we generated a recombinant NDV vaccine strain (rLa Sota-HN) based on the La Sota vaccine strain expressing the haemagglutinin-neuraminidase (HN) protein of genotype VII NDV. The pathogenicity of the recombinant virus was confirmed by the mean death time in 9-day-old specific-pathogen-free embryonated chicken eggs and the intracerebral pathogenicity index in 1-day-old specific-pathogen-free chickens. Subsequently, 1-day-old chickens were immunized with commercial vaccine La Sota and recombinant virus rLa Sota-HN and then challenged with virulent genotype VII NDV strain. The results indicated that recombinant virus rLa Sota-HN provided increased protection of vaccinated chickens from morbidity and mortality, and inhibited the shedding of virulent virus after challenging with genotype VII virus, compared with the conventional vaccine La Sota. Our findings indicated that rLa Sota-HN is a promising vaccine candidate to improve the protection efficiency against ND in chickens, thereby preventing frequent outbreaks of this disease.