Functional transfer of eukaryotic expression plasmids to mammalian cells by Listeria monocytogenes: a mechanistic approach.
BACKGROUND
Cystic fibrosis (CF) is one of the most common monogenic disorders in the caucasian population. Gene therapy for CF is principally feasible and bacterial transfer systems might provide novel possibilities for therapy. However, transfection efficiencies are low and need to be improved. Thus, more detailed understanding of the DNA transfer mechanism is necessary to systematically eliminate these restrictions.


METHODS
Functional transfer of GFP-CFTR (cystic fibrosis transmembrane conductance regulator) to eukaryotic cells using attenuated Listeria monocytogenes mediated gene transfer (bacteriofection) was shown by fluorescent microscopy, flow cytometry, immunoblotting and whole cell patch clamping. The characteristics of plasmid transfer were studied by use of electron and fluorescence microscopy, flow cytometry and Southern blotting. Polymerase chain reaction (PCR) was used to screen the genome of bacteriofected cells for cotransfer of chromosomal bacterial DNA.


RESULTS
Correct intracellular localization and functionality of the GFP-CFTR fusion protein after bacteriofection was shown. Efficient bacterial lysis and release of bacterial content was demonstrated using antibiotics to kill intracellular bacteria. Although only low transfection rates were observed, high numbers of transferred plasmids were detected in host cells under these conditions. However, they were associated with high molecular weight entities and not available to cytosolic transcription. Cotransfer of bacterial genomic DNA was observed in transfectants but occurred at low frequencies.


CONCLUSIONS
In this work we demonstrate that low rates of bacteria-mediated transfection are not due to poor invasion of bacteria, insufficient bacterial lysis, or plasmid DNA degradation. Our data suggest that the transferred plasmid DNA is associated with higher macromolecular structures inhibiting nuclear transport and transgene transcription.
Molecular Immunology, GBF, German Research Centre for Biotechnology, Mascheroder Weg 1, D-38124 Braunschweig, Germany.
Andrea
A
Zelmer
Stefan
S
Krusch
Andreas
A
Koschinski
Manfred
M
Rohde
Holger
H
Repp
Trinad
T
Chakraborty
Siegfried
S
Weiss
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016466:CHO Cells; D002130:Calcium Phosphates; D002467:Cell Nucleus / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism; D003600:Cytosol; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004337:Drug Carriers; D004594:Electrophysiology; D018014:Gene Transfer Techniques; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D010957:Plasmids / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D000900:Anti-Bacterial Agents; D002130:Calcium Phosphates; D004269:DNA, Bacterial; D004337:Drug Carriers; D011993:Recombinant Fusion Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator