Plant Virus Shows Potential as a Cancer Treatment

The cowpea mosaic virus (CPMV) is made up of a potent center covered by a thin coating. The outer shell is harmless, but not useless: Researchers at Case Western Reserve University and Dartmouth University have found that exposure to tiny pieces of CPMV shell can prompt the immune system to begin attacking tumors.

The cowpea, also known as the black-eyed pea, is a bean-like plant that grows in Africa, Asia, Europe, and South America. Cowpeas infected with CPMV develop a patchy pattern on their leaves (hence the name). The virus only infects plants, so we’re safe, even when we get up close and personal with virus particles.

Our immune systems are pretty good at nipping cancerous cells in the bud. But as tumors get larger, they can effectively shut off a person’s immune system, which allows cancer to continue to grow and spread. Researchers were looking for a way to give the immune system a good poke and startle it into working again.

As it turns out, CPMV shells do this pretty well. "The cowpea virus-based nanoparticles act like a switch that turns on the immune system to recognize and fight against the tumor—as well as to remember it," said Nicole Steinmetz, assistant professor of biomedical engineering at Case Western Reserve and the study's co-author, in a press release.

Steinmetz and her colleagues administered microscopic shell particles to mice with lung cancer and melanoma. The treatment prompted an incredibly successful immune response, and several of the mice were declared cancer-free.

The research team also applied CPMV shell particles to tumors in breast, ovarian, and colon tissue. Again, the reactivated immune response destroyed the tumors. It also was able to prevent metastasis—the spreading of tumors throughout the body.

"The particles are shockingly potent," added co-author Steven Fiering, a professor of microbiology and immunology at Dartmouth's Geisel School of Medicine. "They're easy to make and don't need to carry antigens, drugs, or other immunostimulatory agents on their surface or inside."

The treatment seems incredibly effective, and the side effects are minimal. This is not the case with most cancer treatments, which can often be as grueling for patients as the disease itself.

The researchers published their findings in the journal Nature Nanotechnology. Their next steps will include trying to figure out just why and how the CPMV shells are so effective.