The present invention provides a live, attenuated, invasive bacterium that infects a mammalian host cell, and releases exogenous RNA into the cytoplasm of the host cell. The present invention further provides compositions, including immunogenic compositions, comprising a subject bacterium. The present invention provides methods of delivering an RNA to a eukaryotic host cell in vitro, ex vivo, or in vivo. The present invention provides methods of delivering a protein to a host cell in vitro, ex vivo, or in vivo. The present invention provides methods of controlling expression of a target gene in a eukaryotic host cell. The present invention provides methods of inducing an immune response in a mammalian host to a polypeptide antigen, the method involving administering to the host a subject bacterium, wherein the antigen is encoded by the exogenous RNA produced by the bacterium.