Virus Shell Nanoparticles Vaccinate Cancers in Mice

The magazine Science hailed cancer immunotherapy as the breakthrough of the year two years ago, and the field has been gaining traction since. The idea is to activate the body’s own immune cells to recognize cancer cells as disease-causing, and to train them to attack the cancer. Effectively, instead of delivering toxic chemotherapeutics to the whole body, cancer immunotherapy would allow strategic targeting using the body’s immune cells only. It’s kind of like a vaccine, but for cancer. Many approaches are now in clinical trials to explore this avenue, and are showing much potential.

A new study from the Fiering Lab at Dartmouth’s School of Medicine used an empty cowpea mosaic virus as an adjuvant for stimulating the immune system. (That sore arm you get after a flu shot? That’s your immune system jumping into action.) These viruses lack their core DNA like many vaccines, so are non-infectious, but have surfaces that can be recognized by the immune system.

The researchers discovered that inhaling these 30 nm particles reduced metastatic lung tumours of melanoma and breast cancer in mice. The particles also treated colon metastatic growths in the skin, and a fluid-producing ovarian cancer. The authors acknowledge that the exact mechanism of cancer cell death is unknown, but given the dependency on specific proteins, involves the immune system.

The system is promising overall, and largely avoids the delivery issues that most nanotherapeutics run into by administering the doses straight to the diseased organs. The study is interesting given that neutrophils, innate immune cell, are the responders to this viral infection. Also, it’s unclear why normal tissues were spared and tumours were targeted in this innate immune response, which is typically nonspecific. More studies to understand the mechanisms of the cowpea mosaic virus could lead to improved treatment outcomes and translatability to humans.

Study in Nature Nanotechnology: In situ vaccination with cowpea mosaic virus nanoparticles suppresses metastatic cancer…

Nature Nanotechnology News and Views: Cancer immunotherapy: A vaccine from plant virus proteins…