The discovery that domestic cats have not only been naturally and fatally infected with the H5N1 avian influenza virus, but have transmitted it to other cats, raises concerns about their potential role in a global pandemic. In the event of a pandemic, vaccine manufacturers do not have the resources to produce inactivated or modified live viral vaccines for both humans and cats, therefore other types of vaccines need to be developed to protect pets. A recombinant DNA vaccine expressing antigens of H5N1 influenza is safer, easier and less expensive to make since DNA is used as the immunogen rather than whole virus. The goal of this project is to develop a recombinant DNA vaccine that induces potentially protective immune responses in cats. To achieve this goal, we have assembled a collaborative team with the expertise and reagents to make the vaccines, assess feline immune responses, and insure the proper and humane handling of cats. Neutralizing antibody and cell-mediated immune responses generated in cats vaccinated with recombinant DNA vaccines encoding the HA or nucleoprotein (NP) antigens of H5N1 avian influenza will be assessed. Experimental groups will consist of cats receiving: 1) plasmid vector alone; 2) plasmid vaccine with cDNA encoding the HA of an H5N1 influenza virus; 3) a vector encoding influenza A NP cDNA; and 4) H5N1 inactivated influenza vaccine. To assess the serum antibody response, anti-HA and NP ELISA and hemaglutination inhibition (HI) assays will be performed. Cell proliferation and interferon-g assays will be used to assess cell mediated immune responses.