A few years ago, scientists explored the idea of making bacteria seek out certain other cells.They engineered the microbes to display antibodies on their surface. However, it is difficult to get the cells to deliver antibodies to their surfaces. Scientists then learned about adhesins. Adhesins are cell-surface components or appendages of bacteria that facilitate adhesion or adherence to other cells or to surfaces. The adhesins contain an antibody-like moiety that targets antigens on other cells. In order to kill tumor cells or deliver drugs, scientists want to deploy engineered microbes to specific parts of the body. Researchers have now designed a way to target bacteria to particular surfaces by modifying sticky proteins on the microbes’ surfaces.
The researchers built a synthetic adhesin with an antibody that binds to green fluorescent protein (GFP). They incorporated the new adhesin’s gene into the chromosome of E. coli, along with a gene for a bioluminescent protein. The bacteria’s targets were human cancer cells that the researchers modified to express GFP on their surfaces. After mixing the human and bacterial cells together, the team inspected the cells with fluorescence imaging and found that the bacteria colonized the cancer cells. Bacteria without the synthetic adhesin did not adhere to the human cells.
However, the researchers still need to demonstrate safety and that the bacteria can be engineered to target real-world cancer cell proteins. Scientists are currently developing synthetic adhesins that target proteins in bladder and gastrointestinal cancers. These diseases represent what may be the safest application of this technology because they occur in parts of the body normally inhabited by bacteria.