Perspectives Online

Research team ‘accidentally’ finds method of increasing virus’ genetic capacity

Brown (right) and Hernandez, in their Polk Hall lab, have patented their discovery of a way to alter a virus and increase its ability to deliver genetic material to a cell.
Photo by Marc Hall

Oops, another “accident” in the N.C. State University lab of Dr. Dennis Brown and Dr. Raquel Hernandez.

But that’s a good thing. What the husband-wife research team learns by accident — accident in the sense they seem to discover things they weren’t looking for — tends to have great utility.

Most recently, Brown, head of the Department of Molecular and Structural Biochemistry in the College of Agriculture and Life Sciences at N.C. State, and Hernandez, research associate professor, discovered a way to alter a virus to increase its capacity to deliver genetic material to a cell. In other words, they’ve found what appears to be a better way to accomplish genetic engineering. The discovery could benefit anyone suffering from an almost endless list of ailments with genetic components.

The virus in question is called Sindbis, and one of the things that makes it particularly attractive to scientists working to change the genetic makeup of an organism is that, in Brown’s words, “there are no known cells it cannot infect.”

Viruses are popular among genetic engineers because of the way they behave normally. Viruses are opportunistic organisms. They have to be because they don’t have any reproductive machinery of their own.

To reproduce, viruses begin by infecting a host cell. This process exposes the virus’ genetic material to the cell interior. The virus then uses the reproductive machinery of the host cell to replicate itself. This means that if a gene can be packaged in a virus, the virus will then transport that gene into the host cell it infects, and the gene may become part of the host cell’s genetic makeup.

As viruses go, Sindbis is very good at this. As Brown says, it will infect virtually any type of cell. Genetic engineers often want to target their genetic insertions, inserting a gene into, say, liver or skin cells. And when Sindbis infects human cells, it doesn’t cause disease. That would be an argument for using Sindbis for gene therapy, the insertion of genes into people to cure disease.

But Sindbis does have a drawback. It’s small. Brown said that under normal conditions, the size of the virus limits the amount of genetic material that can be packed into it.

What Brown and Hernandez have done is find a way to make a virus that is bigger yet maintains Sindbis’ other characteristics. This discovery was a happy accident, according to Brown. He and Hernandez were not looking for a way to make the virus bigger.

Brown and Hernandez are interested primarily in viral structure, and one way they study structure is by changing viruses — producing mutants — to see how the mutations affect the viral function. The bigger and better version of Sindbis is a mutant, that Brown and Hernandez made in the course of their research. The intended purpose of the mutation was to examine how two viral proteins interacted with each other as the virus was assembled. When the scientists looked at this particular mutant through an electron microscope, they noticed something unusual. Some of the virus particles were two to three times larger than normal.

Brown and Hernandez knew immediately this could be an important discovery. If they could consistently produce large Sindbis particles, they would have an unusually useful genetic cargo transport tool on their hands.

More research followed, and they found they could, indeed, consistently produce unusually large viruses by increasing the size of the RNA incorporated into Sindbis. They have since patented this method of increasing the virus’ genetic capacity, and Brown said a company in India has licensed the technology, while another company in North Carolina is considering a license. Brown added that he’s not sure how the Indian company will use the technology, but much of the company’s research focuses on the polio virus.

The patent is the second related to Sindbis for Brown and Hernandez. Several years ago, Hernandez removed a piece of protein from the Sindbis virus, again producing a mutant. This mutant did not reproduce when it infected mammalian cells, but surprisingly, did reproduce normally in insect cells.

The altered virus appeared to be the perfect candidate for a vaccine. Viral reproduction in insect cells meant it would be possible to produce large amounts of the virus, while the inability of the virus to infect a mammalian host, like a person, meant the virus would cause an immune reaction but not disease when exposed to the host.

While Sindbis does not cause disease in people, viruses similar to Sindbis cause diseases such as dengue and yellow fever. The scientists speculated that using their technology to alter these Sindbis cousins would be an effective way to create vaccines for a range of diseases. The virus alteration technology was licensed to a North Carolina biotechnology startup company called Arbovax, which is now using the technology to develop vaccines for dengue fever, West Nile fever and Chikungunya fever.

—Dave Caldwell