Veronique Beiss, who is the study’s first author, prepares a tray of plants to produce cowpea mosaic virus nanoparticles. Credit: David Baillot/UC San Diego Jacobs School of Engineering
Cowpea mosaic virus, a plant virus that infects legumes, has a special power that you may not be aware of: when injected into a tumor, it activates the immune system to treat the cancer—even metastatic cancer—and prevent it from returning.
Researchers at the University of California San Diego and Dartmouth College have spent the last seven years studying and testing cowpea mosaic virus—in the form of nanoparticles—as a cancer immunotherapy and have reported encouraging results in lab mice and companion dog patients. Its effectiveness has been unrivaled by other cancer-fighting techniques examined by the researchers. However, the precise reasons for its effectiveness have remained a mystery.
In a recent research study published in the journal Molecular Pharmaceutics, the researchers uncover details that explain why cowpea mosaic virus in particular is extraordinarily effective against cancer.
The beauty of this approach is that it not only takes care of that one tumor, but it also launches a systemic immune response against any metastatic and future tumors.
The work was led by Nicole Steinmetz, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering, and Steven Fiering, a professor of microbiology and immunology at the Geisel School of Medicine at Dartmouth. Steinmetz and Fiering are co-founders of a biotechnology startup, called Mosaic ImmunoEngineering Inc., which has licensed the cowpea mosaic virus nanotechnology and is working to translate it into the clinic as a cancer immunotherapy.
“This study helps validate the cowpea mosaic plant virus nanoparticle as our lead cancer immunotherapy candidate,” said Steinmetz, who also serves as the director of the Center for NanoImmunoEngineering at UC San Diego. “Now we have mechanistic data to explain why it is the most potent candidate, which further de-risks it for clinical translation.”
Up until now, Steinmetz, Fiering and their teams had a general idea of how their lead candidate worked. The cowpea mosaic virus nanoparticles, which are infectious in plants but not in mammals, are injected directly inside a tumor to serve as immune system bait. The body’s immune cells recognize the virus nanoparticles as foreign agents and get fired up to attack. When the immune cells see that the virus nanoparticles are inside a tumor, they go after the cancerous cells.
The beauty of this approach, noted Steinmetz, is that it not only takes care of that one tumor, but it also launches a systemic immune response against any metastatic and future tumors. The researchers have seen it work in mouse models of melanoma, ovarian cancer, breast cancer, colon cancer, and glioma. They’ve also had success using it to treat canine patients with melanoma, breast cancer, and sarcoma.
What’s also interesting is that cowpea mosaic virus has worked the best at triggering an anti-cancer immune response compared to other plant viruses or virus-like particles the researchers have studied. “We’ve shown that it works, and now we need to show what makes it so special that it can induce this kind of response,” said first author Veronique Beiss, a former postdoctoral researcher in Steinmetz’s lab. “That’s the knowledge gap we’re looking to fill.”
To get answers, the researchers compared cowpea mosaic virus with two other plant viruses from the same family that have the same shape and size. One virus, cowpea severe mosaic virus, shares a similar
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