Advancement in Vaccination Against Newcastle Disease: Recombinant HVT NDV Provides High Clinical Protection and Reduces Challenge Virus Shedding with the Absence of Vaccine Reactions

Abstract

Newcastle disease (ND) is a highly contagious disease of chickens causing significant economic losses worldwide. Due to the limitation in their efficacy, current vaccination strategies against ND need improvements. This study aimed to evaluate a new-generation ND vaccine for its efficacy in providing clinical protection and reducing virus shedding after challenge. Broiler chickens were vaccinated in ovo or subcutaneously at hatch with a turkey herpesvirus-based recombinant vaccine (rHVT) expressing a key protective antigen (F glycoprotein) of Newcastle disease virus (NDV). Groups of birds were challenged at 20, 27, and 40 days of age with a genotype V viscerotropic velogenic NDV strain. Protection was 57% and 81%, 100% and 95%, and 100% and 100% after the subsequent challenges in the in ovo and subcutaneously vaccinated chickens, respectively. Humoral immune response to vaccination could be detected from 3-4 wk of age. Challenge virus shedding was lower and gradually decreased over time in the vaccinated birds compared to the unvaccinated control chickens. In spite of the phylogenetic distance between the NDV F gene inserted into the vector vaccine and the challenge virus (genotype I and V, respectively), the rHVT NDV vaccine provided good clinical protection and significantly reduced challenge virus shedding.

Newcastle disease vaccines—A solved problem or a continuous challenge?

“…However, the rHVT-ND vaccines are cell associated, so like Marek's disease vaccines, they are required to be kept in liquid nitrogen, and to be administered within an hour of being thawed. Unfortunately, rHVT-ND require four weeks before full immunity will be reached (Palya et al, 2012), which would require the strictest level of biosecurity to prevent infection during that period. This may be impossible in countries where ND is endemic.…”

Presence of Vaccine-Derived Newcastle Disease Viruses in Wild Birds

“…Circulating live vaccine viruses present additional risks such as reversion of virulence and recombination with wild-type strains. In addition, the immune response of wild birds induced by infection with vaccine strains may provide selective pressures resulting in viral antigenic drift or increased virulence [23,[28][29][30][31].Nonetheless, the use of live vaccines continues to dominate the poultry industry, as attested by their performance in the field. Their use is highly desirable as they are inexpensive, allow mass application, and stimulate both strong mucosal and cell-mediated immunity [32][33][34].…”

“…Circulating live vaccine viruses present additional risks such as reversion of virulence and recombination with wild-type strains. In addition, the immune response of wild birds induced by infection with vaccine strains may provide selective pressures resulting in viral antigenic drift or increased virulence [23,[28][29][30][31].…”

Virus-Like Particle Vaccine Confers Protection against a Lethal Newcastle Disease Virus Challenge in Chickens and Allows a Strategy of Differentiating Infected from Vaccinated Animals

“…It is expected that increasing the immunogenicity of the NDV VLP vaccine might confer sterilizing immunity against lethal NDV infection, and further studies on enhancing immunogenicity of the NDV VLP vaccine (e.g., incorporation of a molecular adjuvant into VLPs) will be required. Especially, application of a priming-boosting vaccination regimen in combination with viral vector vaccines expressing the F gene (24) and the NDV VLP vaccine developed in this study is strongly expected to confer sterilizing immunity while still allowing DIVA, although this needs to be studied.…”