Inhaled or injected into tumors of several types of cancer, the shell of cowpea mosaic virus with infectious components removed, in blue, turned on the immune system in mice to wipe out tumors and protect against metastases. Credit: Nicole Steinmetz
Scientists the 100yo in-situ vaccination idea. The idea was to put something inside a tumor and disrupt the environment that suppresses the immune system, thus allowing the natural defense system to attack the malignancy. They used the hard coating of cowpea mosaic virus, with no detectible side effects, which are a common problem with traditional therapies and some immunotherapies.
“The cowpea virus-based nanoparticles act like a switch that turns on the immune system to recognize and fight against the tumor – as well as to remember it,” said A/Prof Nicole Steinmetz.
“The particles are shockingly potent,” said Prof. Steven Fiering. “They’re easy to make and don’t need to carry antigens, drugs or other immunostimmulatory agents on their surface or inside.”
The cowpea virus shell, with its infectious components removed, acts as the adjuvant, a substance that triggers and may enhance or prolong antigen-specific immune responses.
The researchers first switched on the immune system in mice to attack B16F10 lung melanoma or skin melanoma, leaving the mice tumor-free. When the treated mice were later injected with B16F10 skin melanoma (to re-challenge the cured mice), four out of five mice were soon cancer free and one had a slow-growing tumor. The nanoparticles proved effective against ovarian,breast and colon tumor models. Most of the tumors deteriorated from the center and collapsed. The systemic response prevented or attacked metastatic disease, which is the deadliest form of cancer.
“It’s not cytotoxic, there’s no RNA involved or lipopolysaccharides that may be used as adjuvants, and it’s not simply an irritant,” Steinmetz said. “We see a specific immune response.” Unlike most other adjuvants, Fiering said, the virus shells stimulate neutrophils. What role that plays is not yet known. They are seeking grants to study whether the shell’s physical traits or something virus-specific causes the immune response, and to test the therapy in animal models that have immune systems closer to humans.
If the virus shell continues to prove effective, the researchers believe it could eventually be used in combination with other therapies tailored to individual patients. http://www.eurekalert.org/pub_releases/2015-12/cwru-sso122215.php
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