A “Window” Into Infected Cells
An engineered adenovirus that lights up at different stages of infection could give scientists a modern, molecular tool to watch viruses take over cells in real time. In addition to basic virology research, this glowing virus could be used to advance drug and immunotherapy development.
“This is like a window into what’s actually going on in the viral biology,” said Wistar scientist Alex Price, Ph.D., assistant professor in the Genome Regulation and Cell Signaling Program of the Ellen and Ronald Caplan Cancer Center. “You can study what the virus is doing inside cells without having to destroy the cells.”
A Virus—And a Vector for Medicine
Adenoviruses are a large family of DNA viruses that have been studied for decades. They’re also widely used in biotechnology as a vector for immunotherapies, cancer treatments, and gene delivery. But existing tools for tracking adenovirus infections in cells are cumbersome and outdated. It typically takes days to get results, and infected cells are destroyed in the process. The new “reporter” virus engineered by Wistar scientists would allow scientists to watch infections unfold minute by minute.
To build it, Wistar scientists used a modular system called AdenoBuilder to mix and match genetic pieces of the virus like LEGO blocks. They inserted fluorescent proteins that would light up in different colors when certain genes were activated at different stages of infection — green when the virus entered the cell, and red when it completed its life cycle.
This could be useful in drug screening, Price said.
“So, for example, in the presence of a drug that blocks replication, the virus may begin its life cycle and turn green just fine, but it never turns red,” he explained. The researchers also added a gene that causes the virus to secrete a bioluminescent enzyme, allowing researchers to measure infection levels by sampling liquid around the cells, without killing them.
Engineering a Virus to Behave Naturally
Crucially, the team used a “smart map” of the virus’ genome, which Price had previously developed, to guide placement of the new genes without disrupting other functions. This meant the new virus would still replicate and behave exactly like a natural adenovirus.
“It’s very important that we can use this to study how to kill a fully infectious virus,” Price noted.
Beyond antiviral drug screening, the tool could have other applications. For example, adenoviruses are used to deliver DNA-encoded therapies. These vector viruses may be encoded with a trigger that activates when they’re exposed to a second drug. The new reporter virus could be used to test and develop these controlled therapies.
But Price is also excited about the potential for studying adenoviruses themselves. Although incredibly common, adenoviruses still have many mysteries.
“These are very interesting pathogens,” he said. “They’re an excellent model for how DNA viruses take over host cell processes to do the things that they do. So, we want to be able to study these viruses in a way that’s faster and simpler than people could in the past.”
The team’s paper, “Replication-competent adenovirus reporters utilizing endogenous viral expression architecture,” was published in October in the Journal of Virology.