Abstract: A method of delivering a protein to domestic poultry by administering to the poultry by whole body spray an effective amount of a live avirulent derivative of an enteropathogenic bacterium that contains a recombinant gene encoding the protein.

Abstract: A method of vaccinating poultry by spraying the poultry with an effective amount of a live avirulent derivative of an enteropathogenic enterobacteria is disclosed.

Abstract: Disclosed are bacteria having virulence attenuated by a mutation to the regulatory gene poxR. Also disclosed is a method of producing bacteria having virulence attenuated by mutating to the regulatory gene poxR. Such bacteria are useful for inducing an immune response in an animal or human against virulent forms of the bacteria with reduced risk of a virulent infection. Such bacteria are also useful to allow use of normally virulent bacteria as research tools with reduced risk of virulent infection. In a preferred embodiment, poxR attenuated bacteria can be used as a vaccine to induce immunoprotection in an animal against virulent forms of the bacteria. The disclosed bacteria can also be used as hosts for the expression of heterologous genes and proteins or to deliver DNA for genetic immunization. Attenuated bacteria with such expression can be used, for example, to deliver and present heterologous antigens to the immune system of an animal.

Abstract: A vaccine for protecting birds against infection by avian pathogenic gram negative microbes is disclosed. The vaccine is a recombinant Salmonella strain expressing O-antigen of an avian pathogenic gram negative microbe such as an E. coli strain that is pathogenic in poultry. The recombinant Salmonella strain also does not express Salmonella O-antigen. Methods of using the vaccine to immunize birds are also disclosed.