Protection Against Avian Influenza Virus By Immunization With DNA Vaccines

In 1997, a highly pathogenic H5N1 avian influenza virus (AIV) transmitted directly from birds to humans in Hong Kong providing evidence that some AIV have the ability to cross the avian - human species barrier. In 1999, H9N2 subtype avian influenza viruses (AIV) were widely distributed in avian species and were also isolated from humans in Hong Kong and Guangdong provinces. We should pay attention to their potential for pandemic spread and preventive strategies have focused on the development of vaccines. There are many authors indicate that inactivated vaccine provides protective immunity against avian influenza virus infection in mice, chicken and human. Some investigations suggest that the protective efficacy of DNA vaccine is adequate against lethal influenza virus infection. In this study, we examined the antibody response to DNA vaccine and inactivated vaccine and the protection against H5N1 AIV lethal challenge using mouse and avian model. Mice and chicken were immunized with different immune formation. First, animals immunized with DNA priming and protein boosting. Second, animals immunized with protein priming and protein boosting. Third and fourth, animals immunized twice with protein or DNA alone at an interval of 3 weeks. Three weeks after the second immunization, animals were challenged with a lethal dose (20XLD50) of H5N1 AIV. The ability of protection against virus challenge in animals was evaluated by induction of serum antibody response, the lung virus titers of mice, the cloaca virus titers of chicken and...