The present invention is directed to a bacterial delivery system for delivering alphavirus replicon DNA into an animal or animal cells with the replicon encoding one or more heterologous genes to be expressed in the animal or the animal cells. The bacteria are invasive bacteria or attenuated invasive bacteria engineered to contain a DNA vector that encodes the alphavirus replicon in a eukaryotic expression cassette. The heterologous gene can encode an antigen, a therapeutic agent, an immunoregulatory agent, an anti-sense RNA, a catalytic RNA, a protein, a peptide, an antibody or an antigen-binding fragment of an antibody. In a preferred embodiment, the heterologous gene encodes one or more antigens useful as a vaccine for HIV. In addition to the bacterial delivery system, the invention provides methods of introducing and expressing the heterologous gene(s) in animal or animal cells and methods of stimulating or inducing an immune response.