Plant virus fights cancers in mice with “widespread effectiveness”: ScienceAlert

A virus that infects black-eyed pea plants showed “widespread effectiveness” in helping thwart a range of metastatic cancers in mice, researchers report in a new study, raising hopes that the virus may have similar potential for humans.

Nanoparticles harvested from cowpea mosaic virus increased survival rates and consistently suppressed tumor growth in mice with various cancers, including breast, colon, and ovarian cancer.

Mice whose tumors had been surgically removed also showed comparable improvements after treatment, the team from the University of California, San Diego, found.

Cowpea mosaic virus is a plant pathogen specialized in cowpeas (Unguiculate vine), a species of legume that includes the subspecies commonly known as black-eyed pea.

The virus does not directly attack cancer cells in mice, but acts as a form of immunotherapy – a treatment that helps the body’s immune system detect and destroy cancer.

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

Steinmetz and his colleagues have spent years testing cowpea mosaic virus nanoparticles as immunomodulators – substances that suppress or, as in this case, boost the immune system.

Nanoparticles have already shown promise in promoting an immune response when injected directly into a tumor, with results suggesting this treatment may help prevent the spread and recurrence of cancer.

The researchers explain that because it is a plant virus, the cowpea mosaic virus cannot infect mammals, but the immune system of mice still tends to identify it as foreign.

This triggers a strong response from the immune system, which is also prompted to attack the neighboring tumor – as well as any future tumors that develop, according to their research.

But that’s not all, according to the new study. Nanoparticles do not need to be injected directly into tumors to be successful, the study suggests, but can also be administered systemically to prevent metastasis and increase survival rates for a wide range of cancers.

“Here we don’t treat established tumors or metastatic disease – we prevent them from forming. We provide systemic treatment to wake up the body’s immune system to eliminate disease even before metastases form and are settling in,” says Steinmetz.

Steinmetz and his colleagues began the new study by growing black-eyed pea plants in the laboratory and infecting them with cowpea mosaic virus. The virus went to work replicating itself, creating millions of new copies for researchers to collect.

Steinmetz notes that the resulting nanoparticles could already be administered to mice in the experiments and did not require any modification. These are “potent natural nanoparticles, such as produced in black-eyed pea plants,” she says.

The researchers injected these nanoparticles into mice, then challenged them with metastatic tumors a week later, including breast, colon, and ovarian cancers, as well as melanomas.

Compared to control groups of untreated mice, those that received the nanoparticle treatment showed reduced tumor growth and increased survival rates.

The same was true even a month later, when the mice were again confronted with new tumors. As before, mice given cowpea mosaic virus nanoparticles fared significantly better than their untreated counterparts.

The study also included experiments to test the effectiveness of nanoparticles after surgery to remove tumors. This also showed less tumor growth and higher survival rates in the treated mice, which the authors say is particularly interesting.

“Even if you perform surgery to remove tumors, no surgery is perfect and metastases will develop if additional treatment is not provided,” says Steinmetz.

“Here, we use our plant virus nanoparticles after surgery to boost the immune system to reject any residual disease and prevent metastatic seeding of circulating tumor cells,” she adds. “We found that it worked really well!”

Whether it works as well in humans remains to be seen, but this study is a promising step, and the research team is already planning future ones.

The researchers say future studies will seek to reveal whatever mechanism produces the results seen in the new study and establish the safety of the treatment in other animals, paving the way for possible clinical trials in humans. .

The study was published in Advanced science.