Protection of chickens from Newcastle disease by vaccination with a linear plasmid DNA expressing the F protein of Newcastle disease virus.

To evaluate the usefulness of a DNA vaccine for chickens, we constructed a plasmid vector expressing the Newcastle disease virus F protein (NDV-F) under the control of the human cytomegalovirus immediate early enhancer and chicken beta-actin gene promoter. One-week-old chickens injected intramusculary with the circular plasmid DNA did not produce significant levels of antibody against NDV-F. However, two of five birds injected with the linearized plasmid DNA produced high levels of the antibody. Moreover, four of five birds injected with a mixture of the linearized-plasmid and Lipofectin produced the antibody efficiently. At 9 weeks post-injection, chickens were challenged with the velogenic NDV Sato strain. These chickens that had the antibody against NDV-F were protected from lethal NDV challenge. These results demonstrate that the DNA vaccine conferred efficient protection against the disease.