Bacteria-Mediated Transfer of Eukaryotic Expression Plasmids into Mammalian Host Cells

Abstract

Invasive intracellular bacteria are able to transfer eukaryotic expression plasmids into mammalian host cells in vitro and in vivo. This can be used to induce immune responses toward protein antigens encoded by the plasmid or to complement genetic defects. Plasmid transfer takes place when the recombinant bacterium dies within the host cell, either due to metabolic attenuation or induction of autolysis. Alternatively, antibiotics can be used and spontaneous transfer has also been observed, indicating that this phenomenon might also occur under physiological conditions. Plasmid transfer has been reported for Shigella flexneri, Salmonella typhimurium and S. typhi, Listeria monocytogenes and recombinant Escherichia coli, but other invasive bacteria should also share this property. In vivo attempts were mainly directed toward vaccination using shigella and salmonella as carrier. So far a wide variety of antigens have been used succesfully in mice. Often this type of immunization was superior over direct application of antigen or using the same bacterium as a heterologous carrier expressing the antigen via a prokaryotic promoter. Characterization of the host cells revealed that macrophages and dendritic cells might be responsible for immune stimulation by either expressing the antigen or cross-presenting the antigen after uptake of apoptotic antigen expressing cells.

Delivery of functional DNA and messenger RNA to mammalian phagocytic cells by recombinant yeast

“…4,27 We show, for the first time, that recombinant yeast cells are able to deliver DNA very efficiently to murine macrophages and, importantly, also to human DCs. Conveniently, the yeast-based system developed in this study is not restricted to the transfer of DNA, but can also effectively deliver functional mRNA.…”

“…In contrast, classical DNA/RNA vaccination is per se unspecific, and the majority of carriers currently under investigation (bacteria and viruses) is unable to target APCs in particular and rather infects a variety of cell types like epithelial, muscle cells and other non-APCs. 3,4,[29][30][31] Taking this into account, the effective delivery of DNA by recombinant yeast regains in importance considering the danger of unwanted genomic integration of plasmid DNA into APCs in which no known potential to develop diseases like cancer exists. Likewise, the novel yeast carrier described here could also be used for therapeutic purposes in which delivery of nucleic acids into APCs is desired.…”

“…Among these bacteria, most of the strains that have been used for antigen delivery belong to the large group of invasive enteric bacterial pathogens such as Escherichia coli, Shigella, Salmonella or Listeria. 4 Hitherto, several of these attenuated bacteria have been exploited to deliver heterologous antigens to mammalian cells as functional DNA or messenger RNA (mRNA) to be expressed in the infected host cell. [4][5][6][7] However, although a number of studies have indicated the principle feasibility of this approach, convincing results of clinical trials are still missing.…”

“…4 Hitherto, several of these attenuated bacteria have been exploited to deliver heterologous antigens to mammalian cells as functional DNA or messenger RNA (mRNA) to be expressed in the infected host cell. [4][5][6][7] However, although a number of studies have indicated the principle feasibility of this approach, convincing results of clinical trials are still missing. 8 Furthermore, bacteria often contain highly toxic cellular components such as lipopolysaccharides (gram-negative bacteria) or super antigens (many gram-positive bacteria), which detract them from being used in humans for safety concerns or at least diminish the acceptance of a putative vaccine.…”

A One-Plasmid System To Generate Influenza Virus in Cultured Chicken Cells for Potential Use in Influenza Vaccine

“…In addition to various DNA transfection methods, bacterium-mediated gene transfer, known as bactofection, is a well-established method (8,23). Salmonella enterica, Shigella spp., and other invasive bacteria are employed as vectors to deliver DNA vaccines into host cells (1,4,13,21,22).…”