A microscopic syringe to deliver vaccines

Sometimes there’s a goof-up when bacteria divide, and one cell, called a “minicell,” contains no chromosomal DNA. Minicells can’t replicate (or cause infection), and scientists can tweak them to carry proteins, making them a safe vehicle for vaccines.

Jorge E. Galán, Ph.D., D.V.M., chair and Lucille P. Markey Professor and chair of Microbial Pathogenesis and professor of cell biology, had previously shown that a needle-like machine possessed by the bacterium Salmonella typhimurium could be engineered to inject into human cells any particle that scientists wanted the body’s immune system to attack. But using this syringe mechanism meant setting a small number of bacteria loose in the body, which can be risky in some patient populations.

In a new study, published March 12 in Nature Communications, Galán and colleagues isolated minicells from a strain of Salmonella and engineered them to contain all the components of the injection system. When administered to mice, the minicells elicited an immune response but did not generate a full-blown infection, the ideal response to a vaccine.

The system could be used to combat cancer as well as a wide variety of infectious diseases, says Galán.