ASM Attends UN General AssemblyASM President, Susan Sharp, Ph.D., joined global leaders at the United Nations General Assembly in New York today in a historical meeting to focus on the commitment to fight AMR.
You develop and test DNA vaccines for a wide range of viruses. How do DNA vaccines work?
We're working on viruses that have RNA genes in them, so first we make a cDNA copy of the virus RNA. Those are cloned into bacterial plasmids, which are circular DNAs in bacteria. When you introduce these DNAs into mammalian cells, they have some elements in them that allow the mammalian enzymes to copy the DNA back into mRNA. The proteins are made in the cytoplasm, and it's just as if the cell is infected with a virus at that point. It's making mRNA and proteins that are the same as those of a virus.
Which vaccines are your lab currently working on?
We're working on vaccines in two different areas: the biothreat area and medical infectious diseases. "Biological warfare defense" focuses on those agents that could be used as weapons. "Medical infectious diseases" refers to natural infections. In the biological warfare defense area, our lead candidates are in Venezuelan, eastern, and western equine encephalitis viruses. In the medical infectious diseases area, our lead candidate vaccine is for hantaviruses that cause hemorrhagic fever with renal syndrome. We are going into a phase one clinical study with that vaccine delivered by gene gun early in 2008.
How does a gene gun work?
You take your DNA vaccine and coat it onto small, micron-size gold beads. They're placed inside a device that has a helium pressure so that when you push the trigger it blasts the gold that's coated with DNA into the skin.
You're basically blasting gold particles into the surface of the skin - that sounds painful.
It doesn't hurt at all. It feels like a puff of air on your arm.
What is the Army's interest in vaccines?
We are trying to develop vaccines [for diseases] that are unique military threats. Things that nobody else would be working on but are still of danger to the troops. We're also interested in developing combination vaccines so that the soldiers have to get fewer vaccinations.
It's said that industry is reluctant to invest in R&D for vaccines for many infectious diseases in third world countries because there wouldn't be a big or lucrative market for the end product. Do you think the Army has had to take up the slack in this regard?
Unfortunately that's true, but the problem now is that the military doesn't have the money to do it either. It's almost critical now that we partner with a company to jointly develop these vaccines. We can get through the basic research and development, but to actually go out and do the huge field studies, it would have to be a huge priority for the Army to bear all of the cost of that.
What does the future of vaccine development look to you?
I just returned from a DNA vaccine conference in Spain last week. There is, as of yet, no licensed human DNA vaccine, but there are licensed veterinary vaccines. There are a lot of clinical studies going on with human DNA vaccines for HIV, for cancer therapy, and several other infectious diseases including influenza. There have already been clinical trials with hepatitis DNA vaccines. I think in the next five years we're likely to see a DNA vaccine for humans licensed. I hope it's ours.
What do you think is the most understudied microbial system?
I think we're not paying enough attention to many of the arthropod-borne viruses in third world countries, especially in Africa. There are viruses that are causing hundreds of thousands of febrile disease cases each year, and it's just a matter of time before one of those is going to emerge to be one of our next big threats here.
What is your favorite microorganism and why?
Hanta virus is my favorite because I was a postdoc when we discovered it and have been with it since it's "birth." I was the first person ever to see those three pieces of RNA and say, "There's only one group of viruses in the world with three pieces of RNA - it's a bunyavirus."
What advice would you give students about life as a microbiologist?
You have to work very hard. You need to pay attention all the time to where you're going, and seek a good mentor because that makes all the difference in the world.
What is something about you that most people don't know?
I love to play tennis. I'm in all kinds of groups, USTA (United States Tennis Association) tennis, I'm in several women's groups, and I play with my husband. We play tennis almost every day.