Submitted to: American Veterinary Medical Association Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 8, 2014
Publication Date: July 26, 2014
Citation: Cardenas Garcia, S., Miller, P.J., Brown, C.C., Afonso, C.L. 2014. Improving newcastle disease vaccination with homologous vaccines [abstract]. American Veterinary Medical Association. Abstract/Paper ID No. 16714. p. 59. Technical Abstract: All Newcastle disease viruses (NDVs) belong to a single serotype; however, current vaccine strains display important amino acid differences at the F and HN protein compared with virulent outbreak strains (vNDV). Previous studies have shown decreased viral shedding after challenge when vaccines were genetically homologous to the vNDV. In the present study, two recombinant vaccine viruses were generated by replacing the F and HN genes from the LaSota vaccine backbone (genotype II) with the F and HN genes from vNDV of genotypes VIId and XIII. The recombinant viruses were attenuated by mutating the fusion protein cleavage site and thoroughly characterized to confirm their safety. One-day-old SPF chickens were either vaccinated with one of these viruses or the LaSota vaccine and 14 days after vaccination were challenged with their respective homologous virulent virus (vNDV-VIId or vNDV-XIII). Results demonstrate that the experimental vaccines conferred 100% survival, prevented clinical signs, and decreased oropharyngeal virus shedding compared with the LaSota vaccine. Additionally, when four-week-old SPF chickens were vaccinated with the experimental vaccine expressing the F and HN glycoproteins from the genotype XIII virus or with the LaSota vaccine at 10^3, 10^4, 10^5 or 10^6 EID50/bird, and challenged with the vNDV-XIII, the mortality after challenge was decreased in those groups that received the vaccine homologous to the challenge virus, compared to the LaSota vaccine. In conclusion, the F and HN genes homologous to the circulating virulent NDV are sufficient to decrease virus shedding of the challenge virus and to reduce mortality more effectively than the LaSota vaccine.