VacciMonitor (Sep 2023)
Alternative method using Real Time PCR for evaluation of inactivated Newcastle disease viral vaccine
Abstract
The present work aims to establish a new alternative protocol to evaluate in vitro potency of inactivated Newcastle disease virus vaccine using Real Time PCR. Aqueous phases of seven inactivated Newcastle disease virus vaccines batches of different manufacturers were extracted by isopropyl myristate. The Newcastle disease virus antigen of each vaccine sample was determined by a standard Real Time PCR assay. Vaccines were inoculated into separate groups of 3-week-old specific pathogen free chickens using the recommended dose of vaccine. The immunogenicity was assessed for each vaccine by the Newcastle disease virus hemagglutination inhibition antibody titers. Individual serum samples were collected 4 weeks post vaccination, then vaccine efficacy and protection rates were recorded after challenge test of birds vaccinated with the virulent Newcastle disease virus. There is the possibility of using the Real Time PCR as an in vitro assay for vaccine evaluation. The Cycle Threshold values were ranged between 21.17 and 25.23. On the other hand, the hemagglutination inhibition titers ranged between 7.1 log2 to 6.2. The comparison between the Cycle Threshold values of the antigen extracts and the corresponding results of challenge test and in vivo hemagglutination inhibition assays using sera of vaccinated birds proved a strong correspondence between the in vitro and in vivo results.
