Title: Effect of genotype specific live recombinant Newcastle disease vaccines on virus shedding after challenge Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2013
Publication Date: N/A
Technical Abstract: All Newcastle disease viruses (NDVs) are part of a single serotype; however, current vaccine strains display between 15 and 18% amino acid differences at the F and HN protein compared with current virulent viruses. Previous studies have shown that increased amino acid similarity between NDV vaccines and field viruses is important to decrease virus shedding after challenge. In the present study, two lentogenic recombinant viruses were generated by replacing the F and HN genes from virulent NDV of genotypes VIId and XIII circulating in South Africa and Pakistan, respectively, into the Lasota vaccine backbone (genotype II). The pathogenicity of the recombinant viruses was attenuated by changing the fusion protein cleavage site. Intracerebral pathogenicity index, clinical signs, and virus shedding were also evaluated to determine if the vaccine virus was capable of replicating or causing disease in chickens. One day old SPF chicks were vaccinated with live virus and 14 days after vaccination were challenged with their respective homologous virulent virus from South Africa or Pakistan to test their performance in comparison with the LaSota vaccine strain. Results from these experiments demonstrate that these experimental vaccines replicate in birds and do not cause disease; even more, this vaccines conferred 100% survival, prevented clinical signs, and decreased oropharyngeal virus shedding compared with the LaSota strain. In conclusion, these recombinant viruses seem to be good candidates to be used as live vaccines.