Location: Endemic Poultry Viral Diseases Research
2019 Annual Report
Accomplishments
1. Newcastle disease (ND) recombinant expressing the infectious laryngotracheitis virus (ILTV) glycoprotein D(gD) has been demonstrated to confer protection against both virulent NDV and ILTV challenges. However, there is a concern on the genetic stability of the recombinant vaccine. ARS scientists in Athens, Georgia, evaluated the genetic stability of the recombinant vaccine after eight serial passages in embryonated chicken eggs (ECE) to mimic Newcastle disease virus (NDV) vaccine production. Next-generation sequencing analysis of the vaccine master seed and the egg-passaged virus stocks confirmed their genome integrity and revealed a total of thirteen single-nucleotide polymorphisms (SNPs). However, none of these SNPs was located in the ILTV gD insert or any of the known critical biological determinant positions. Virological and immunofluorescent assays provided additional evidence that the egg-passaged virus stocks retained their growth kinetics, low pathogenicity, and robust level of gD expression comparable to that of the vaccine master seed virus. These results demonstrated that the insertion of ILTV gD gene into the NDV LaSota backbone did not significantly affect the genetic stability of the recombinant virus, and that the rLS/ILTV-gD virus is a safe and genetically stable vaccine candidate after at least eight serial passages in ECE.
