Location: Endemic Poultry Viral Diseases Research
2020 Annual Report
Accomplishments
1. Many Newcastle disease virus (NDV) strains have been developed as vectors to express a foreign gene (FG) for vaccine and cancer therapy purposes. Since the early 2000s, reverse genetics technology has been used to develop Newcastle disease virus (NDV) vaccine strains as vectors to deliver antigens from other avian pathogens as dual or multivalent vaccines. However, most of these NDV vectors express only a single or two foreign genes (FGs) from suboptimal insertion sites in the NDV genome, obtaining different FG expression or vaccine protection levels. To improve the FG expression, ARS researchers in Athens, Georgia, developed a novel NDV LaSota vaccine-based vector to express two FGs from the identified optimal insertion sites in the NDV genome. Biological assessments showed that the expression of two FGs from the optimal insertion sites was significantly more efficient than those from the suboptimal insertion sites. These results suggest that the NDV LaSota vector could efficiently express two antigens derived from an avian pathogen or two different pathogens as a dual or multivalent vaccine candidate, which will provide a broad protection against poultry infectious diseases.
2. Infectious bronchitis virus (IBV, a coronavirus) causes severe infectious bronchitis (IB) of chickens, resulting in significant economic losses to the poultry industry worldwide. Infectious bronchitis virus (IBV, a coronavirus) causes severe infectious bronchitis (IB) of chickens, resulting in significant economic losses to the poultry industry worldwide. Vaccination with serotype-specific attenuated live IBV vaccines is a common practice to control the disease. However, like most coronaviruses, the IBV vaccine viruses are constantly evolving in the vaccinated chickens. Some of the mutated vaccine subpopulations revert virulence and contribute to the IB outbreaks. Therefore, there is a need to develop a safe, genetically stable, and efficacious vaccine against IB. ARS researchers in Athens, Georgia, in collaboration with scientists at Auburn University, generated a Newcastle disease virus (NDV) LaSota vaccine-based recombinant virus as a vaccine candidate. Biological assessments demonstrated that the new recombinant virus was safe and stable. At 1 or 10 days of age, chickens were vaccinated with different doses of the vaccine and challenged with different virulent IBV Ark strains in two experiments. The results showed that single-dose vaccination provided inefficient protection against the IBV challenge. A higher single-dose or a prime-boost vaccination approach conferred significant clinical protection and reduced tracheal lesions. However, neither single-dose nor a prime-boost vaccination reduced the challenge virus shedding. Thus, further development of the vaccine compositions and vaccination approach is needed to improve the overall vaccine protective efficacy.
Review Publications
Yu, Q., Li, Y., Dimitrov, K., Afonso, C.L., Spatz, S.J., Zsak, L. 2020. Genetic stability of a Newcastle disease virus vectored infectious laryngotracheitis virus vaccine after serial passages in chicken embryos. Vaccine. 38(4):925-932. https://doi.org/10.1016/j.vaccine.2019.10.074.
He, L., Zhang, Z., Yu, Q. 2020. Expression of two foreign genes by a Newcastle disease virus vector from the optimal insertion sites through a combination of the ITU and IRES-dependent expression approaches. Frontiers in Microbiology. 11:769. https://doi.org/10.3389/fmicb.2020.00769.
Zegpi, R.A., He, L., Yu, Q., Joiner, K.S., Van Santen, V.C., Toro, H. 2020. Limited protection conferred by recombinant Newcastle disease virus expressing infectious bronchitis spike protein. Avian Diseases. 64(1):53-59. https://doi.org/10.1637/0005-2086-64.1.53.
