"Cowpea mosaic" a plant virus that fights cancer with "broad-spectrum effectiveness"

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University of California San Diego researchers reported that a virus that infects black-eyed bean plants (cowpea) has been shown to be highly effective in preventing a group of metastatic cancers in mice.

Nanoparticles in the cowpea mosaic virus enhanced survival rates, while systematically suppressing tumor growth in mice with various types of cancer, including breast, colon and ovarian cancer.

The research team found that mice that underwent surgical removal of tumors also showed similar improvements after treatment.

The cowpea mosaic virus is known as a plant pathogen that specializes in cowpea (Vigna unguiculata), a type of legume that includes the subspecies known as black-eyed beans.

The virus does not directly attack cancer cells in mice, but rather acts as a form of immunotherapy, helping the body's immune system find and destroy cancer.

The new study comes as part of ongoing research led by the laboratory of Nicole Steinmetz, a nanoengineer at the University of California San Diego.

Steinmetz and her colleagues have spent years testing cowpea mosaic virus nanoparticles as immunomodulators - substances that either suppress the immune system or, in this case, stimulate it.

Previously, nanoparticles have shown promising results in enhancing the immune response when injected directly into the tumor, and the results indicate that this treatment could help prevent the spread and recurrence of cancer.

The researchers explain: “Because it is a plant virus, cowpea mosaic cannot infect mammals. However, the immune systems of mice still tend to recognize it as a foreign body, and this provokes a violent reaction from the immune system, which is stimulated.” "Also to attack a nearby tumor, as well as any tumors that may develop in the future."

The study suggests that nanoparticles do not have to be injected directly into tumors to achieve success, but they can also be delivered systemically to halt metastasis growth and increase survival rates for a wide range of cancers.

“Here, we do not treat existing tumors or metastatic disease, but rather prevent them from forming,” Steinmetz says. “We provide systemic therapy to awaken the body’s immune system to eliminate the disease before metastases form and stabilize.”

The researchers say that future studies will seek to uncover the mechanism that produces the results shown in the new study, and determine the safety of the treatment in other animals, paving the way for eventual clinical trials in humans.

The study was published in the journal Advanced Science.