Abstract: A system for delivering a payload nucleic acid into target cells of a subject and production of a payload (or payloads) encoded by the payload nucleic acid in the cells. The system includes a Bifidobacterium sp. bacterium comprising a plasmid and a transporter nucleic acid, the transporter nucleic acid configured for expression in the bacterium. The transporter nucleic acid encodes a transporter polypeptide comprising, in an amino-terminal to carboxy-terminal order, a bacterial secretion signal peptide, a DNA-binding domain to bind the plasmid, and a cell penetrating peptide. The transporter polypeptide complexes with the plasmid and transports the plasmid from the bacterium into the target cells. The plasmid encodes one or more payloads (protein and/or ribonucleic acid) for production in the target cells. The target cells may be colonic cells. When the payload(s) include an antigen, the system may be a DNA vaccine.