Purdue Univ. researchers have successfully eliminated the native infection preferences of a Sindbis virus engineered to target and kill cancer cells, a milestone in the manipulation of this promising viral vector.
“This virus had been known to be a good vector for delivering therapeutic cargo, however it naturally infected all kinds of cells, and these diversions would compete with what we were instructing it to target,” said Richard Kuhn, the Gerald and Edna Mann Director of Purdue’s Bindley Biosciences Center. “We have now overcome a major challenge by not only inserting a targeting molecule of our choice, but also successfully stripping the virus of its native entry preferences. This was a big step in unlocking the potential of developing this virus into a platform for both targeted drug delivery, where it would sneak drugs inside cancer cells, and oncolytic virotherapy, where the virus itself destroys cancer cells.”
The achievement also demonstrates the ability to use methods of manipulation previously only applied to proteins. The team combined the methods of rational design, in which certain portions of the virus were strategically altered based on known information about their structure and function, and directed evolution, in which random mutations were introduced to millions of copies of the virus and the results are then screened for the desired traits, he said.
“These experiments demonstrate that these two methods can be combined and used to create complex molecular machines, like this viral vector with a tailored targeting receptor,” said Kuhn, who also is head of the Department of Biological Sciences. “We’ve now reached the point where we can easily change the virus to carry a variety of cargos and to seek out specific types of cells. We know where and how to add the characteristics we want and eliminate those that we do not.”
A paper detailing the work was published in the October issue of the Journal of Virology and is currently available online. In addition to Kuhn, co-authors include Purdue postdoctoral researcher Zheng Liu, associate professor of biological sciences Wen Jiang and former postdoctoral researcher Hong-Sheng Dai. The National Institutes of Health funded this research.
Through standard rational design procedures the team inserted a human epidermal growth factor, or EGF, targeting sequence into the genome of the virus, and changed some of its amino acids to stabilize the addition, Kuhn said.
Cancer cells have large quantities of this growth factor receptor and it has been studied as a target for cancer therapies for nearly 30 years. When the ESV1 virus binds to the EGF receptor on a cancer cell it triggers a natural signal for the cell to internalize, or consume, the growth factor and the virus is carried in along with it, he said.
“This receptor is found in healthy human cells, however these cells won’t be harmed by the ESV1 virus because they don’t consume the growth factor in anywhere near the quantities cancer cells do,” he said. “A healthy cell will easily be able to manage this virus, but cancer cells will gobble it up in overwhelming and deadly amounts.”