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August 19, 2011

Bacteria inject DNA into human cells

Bacterial pathogens can translocate genetic information, in the form of DNA, into human host cells. This has been demonstrated for the first time by scientists at the Biozentrum of the University of Basel using the bacterium Bartonella as an example. The underlying DNA-transfer mechanism provides possible new approaches for the development of gene therapies and new strategies in combating hereditary diseases. The results of Prof. Christoph Dehio’s research group have been published in the current issue of the American journal PNAS.

Nobel Laureates in Chemistry 2014

The bacterium Bartonella transfers a cocktail of bacterial proteins into human cells with the aid of a molecular injection needle (“Type IV secretion system”), which enables this pathogen to cause chronic infections. Christoph Dehio’s research group at the Biozentrum has now been able to demonstrate that the molecular injection needle can also transfer DNA, in a similarly way to which the gene transfer between bacteria (conjugative DNA-transfer) is known to occur. Furthermore, through genetic alterations, the scientists have been successful in specifically altering the size, sequence and number of transferred DNA molecules.

Lasting Effect of Transferred DNA

Once in the human cell, the DNA, which has been mobilized via the molecular injection needle, can be integrated into the genome in the cell’s nucleus. This naturally occurring DNA-transfer process could thus be utilized to intentionally introduce specific genetic information via bacteria into human cells and to bring about a lasting effect. The introduced DNA could replace existing defective DNA segments in the genetic material of the cell and so provide new approaches in gene therapy.

New Approach in Gene Therapy

This evidence of bacterial DNA transport into human cells and the possibility to adjust the amount and size of the DNA molecules are unique. In contrast to viruses, which can only introduce short segments of DNA into human host cells, the size of bacterially transferred DNA is not limited. For this reason, these findings demonstrate an enormous potential for possible therapeutic interventions. “It is conceivable to be able to alter a bacterial pathogen, which would normally be the cause of infections, such that it could be utilized for a therapeutic gene therapy in humans. In the light of the diversity of gene defects, this could be a very promising therapeutic approach“, commented Dehio.

Original article:

“Conjugative DNA transfer into human cells by the VirB/VirD4 type IV secretion system of the bacterial pathogen Bartonella henselae”

http://www.pnas.org/content/early/2011/07/28/1019074108.abstract?sid=acb67515-c50f-4559-bd4b-73f11b6ecced

Contact: Communications, Heike Sacher