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Stanford scientists co-opt viral machinery to create medical delivery system

James Swartz

Stanford engineering researcher James Swartz, PhD, and his colleagues have remodeled a hepatitis B virus to turn it into a microscopic taxi for medical therapies. The team stripped the virus of its pathogenic DNA and modified an outer shell so that they could “hang” molecular tags on the outside to help deliver vaccines or other therapies to specific cells. The researchers reported their findings in a paper in the scientific journal Proceedings of the National Academy this week.

They call the engineered product a virus-like particle (as opposed to a real virus with infectious material) or a smart particle. “We make it smart by adding molecular tags that act like addresses to send the therapeutic payload where we want it to go," Swartz said in a Stanford News story.

The smart particle is a novel way to deliver vaccines or cancer therapies by teaching the body’s immune cells to recognize pathogens or cancer cells. Alternatively, the smart particle can deliver medicine specifically to the cells that need it.

Swartz and his colleagues’ effort is part of a larger field of targeted therapies that aims to precisely deliver therapies to the cells that need them and avoid damaging nearby healthy cells. Current cancer therapies, for example, are effective at fighting malignant cells, but also kill off healthy cells. That’s why cancer therapies often have such devastating side effects. But previous attempts to create virus-sized delivery systems have not been successful. In fact, Swartz's team had a hard time getting funding for the early stages of this project because of previous failed efforts by other scientists.

So far, Swartz and colleagues have created the self-assembling shell that is invisible to the body’s natural immune defenses and strong enough to weather conditions in the blood stream and get its packaged contents to its destination inside the body. Next, they’ll work on putting specific cancer-fighting tags on the shell.

The most challenging task will be to pack the shell with a tiny dose of medicine. But Swartz sounded optimistic about his team’s goals. “I believe we can use this smart particle to deliver cancer-fighting immunotherapies that will have minimal side effects," he said.

Previously: A less toxic, targeted therapy for childhood brain cancerIs cancer too complex for targeted therapies? and Working to create a universal flu vaccine
Photo, of Swartz holding an enlarged replica of a virus-like particle, by Linda Rice

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