This Virus Doesn’t Make You Sick. It Makes You Stronger

A virus normally found in black-eyed peas is emerging as a powerful ally in the fight against cancer.

Scientists discovered that this plant virus, called CPMV, doesn’t infect human cells—but it does trigger a potent immune response, training the body to recognize and destroy cancer cells. Unlike typical therapies, it primes both innate and adaptive immunity, offering long-term protection.

Plant Virus Shows Promise as Cancer Immunotherapy

A virus known for infecting black-eyed peas is now emerging as a surprisingly powerful tool in cancer treatment, and scientists are beginning to understand why.

Researchers from the University of California San Diego, led by a team of chemical and nano engineers, recently published a study in Cell Biomaterials that dives into how the cowpea mosaic virus (CPMV) stimulates the human immune system in a way that other plant viruses do not. Unlike its viral relatives, CPMV appears to uniquely trigger immune cells to recognize and fight cancer.

Immune System Activation and Anti-Tumor Memory

In laboratory studies involving mice and even dogs with cancer, CPMV has shown strong anti-tumor effects. When injected directly into a tumor, the virus draws various innate immune cells into the area, including neutrophils, macrophages, and natural killer cells, which begin attacking the cancer. At the same time, CPMV activates B cells and T cells to build a long-term immune memory. This response not only helps eliminate the original tumor but also prepares the immune system to find and attack cancer that may have spread elsewhere in the body.

“It is fascinating that CPMV but not other plant viruses stimulates an anti-tumor response,” said Nicole Steinmetz, the Leo and Trude Szilard Chancellor’s Endowed Chair in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering and the study’s corresponding author.

“This work gives us insight into how CPMV works so well,” said study first author Anthony Omole, a chemical and nano engineering Ph.D. student in Steinmetz’s lab. “What we found most exciting is that although human immune cells are not infected by CPMV, they respond to it and are reprogrammed towards an activated state, which ultimately trains them to detect and eradicate cancerous cells.”

What Makes CPMV Unique? A Side-by-Side Viral Comparison

A key question in translating CPMV to human cancer patients has been: what makes this plant virus so effective at fighting cancer?

To investigate, Omole, Steinmetz, and colleagues at the National Cancer Institute’s ​​Nanotechnology Characterization Laboratory performed a side-by-side comparison of CPMV with the cowpea chlorotic mottle virus (CCMV), a closely related plant virus that does not exhibit anti-tumor effects when administered intratumorally. Both viruses form similarly sized nanoparticles and are taken up by human immune cells at similar rates. Yet, once inside, the viruses produce different outcomes.

Viral RNA Processing and Immune Signaling

CPMV, the team found, stimulates type I, II and III interferons—proteins with well-known anti-cancer properties. “This is particularly interesting because some of the earliest cancer immunotherapy drugs were recombinant interferons,” noted Omole. Meanwhile, CCMV stimulates a set of pro-inflammatory interleukins that do not translate to effective tumor clearance.

Another difference lies in how these viruses’ RNAs are processed within mammalian cells. CPMV RNAs persist longer and get delivered to the endolysosome, where they activate toll-like receptor 7 (TLR7), a critical component in priming antiviral—and more importantly—anti-tumor immune responses. CCMV RNAs, on the other hand, fail to reach this activation point.

A Cheap, Scalable Therapy Grown in Plants

CPMV also offers a unique advantage as a cost-effective immunotherapy. Unlike many other therapies that require complex and costly manufacturing, CPMV can be produced using molecular farming. “It can be grown in plants using sunlight, soil, and water,” Omole said.

The team is working toward advancing CPMV to clinical trials.

“The present study provides important insights into the mechanism of action of CPMV. We are diligently working toward the next steps to ensure that the most potent lead candidate is selected to achieve anti-tumor efficacy and safety,” Steinmetz said. “This is the time, and we are poised to move this work beyond the bench and toward clinical trials.”

Reference: “Comparative analyses for plant virus-based cancer immunotherapy drug development” by Anthony O. Omole, Hannah S. Newton, Edward Cedrone, Kimia Nematpour, Shaojun Xie, Yongmei Zhao, Bao Tran, Marina A. Dobrovolskaia and Nicole F. Steinmetz, 22 May 2025, Cell Biomaterials.
DOI: 10.1016/j.celbio.2025.100095

This work was supported in part by the National Institutes of Health (NIH grants R01 CA224605, R01 CA253615 and R01 CA274640); the American Cancer Society, F.M. Kirby Foundation Inc., Mission Boost Grant (MBGI-23-1030244-01-MBG); the Shaughnessy Family Fund for Nano-ImmunoEngineering (nanoIE) at UC San Diego; San Diego Fellowship Fund; the Alfred P. Sloan Foundation’s Minority PhD (MPhD) Program (G-2020-14067); and the Frederick National Laboratory for Cancer Research funded by the National Cancer Institute, part of the NIH (under contract 75N91010D00024).

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