For most medical researchers in the late 1970s, the adeno-associated virus simply held no interest. While the viruses responsible for influenza, hepatitis and encephalitis could trigger devastating damage, AAV just quietly replicated, infecting most humans but causing no problems.
But AAV intrigued microbiologist Kenneth Berns, who thought he could learn some basic lessons of biology by studying the innocuous creature. And, he suggested to colleague Nicholas Muzyczka, perhaps this harmless virus could actually be used to treat illness by serving as a vehicle to carry "corrective" genes into the cells of someone suffering disease.
Muzyczka was interested, but it wasn’t until a couple of years later, when both men had moved from Johns Hopkins to the University of Florida, that Muzyczka and others began to investigate the concept seriously.
Today, Berns is UF’s vice president for health affairs and dean of the College of Medicine, Muzyczka is director of the university’s Powell Center for Gene Therapy, and AAV has become the carrier of choice for numerous gene therapy studies at UF and across the country.
Spurred by the enormous potential of AAV, a burgeoning contingent of UF researchers using it and other vectors under development are now exploring gene therapy for cystic fibrosis, Parkinson’s disease, hypertension and a host of other conditions.
"Gene therapy is exciting," says Muzyczka. "If it works, we’re looking at something that may be as powerful as organ transplantation, that would become a major medical procedure enabling us to do something about diseases we haven’t been able to touch so far."
Across the campus, scientists united under the umbrella of UF’s new Genetics Institute have been delving into the genetic codes of a host of living things. They are finding surprising links among vastly different species — links that are leading to collaborations among faculty whose fields of interest once seemed mutually exclusive.
They are making discoveries of almost immediate consequence — how, for example, to manipulate crops to be disease-resistant. But they also are learning lessons whose import will take much longer to discern.
Berns says that’s the way it is with science, noting that when he started researching AAV, there was no way to predict how significant the work would prove to be.
"Now suddenly we find that it’s one of the leading contenders to be a vector for gene therapy," he says. "I think this is a very good model for the value of doing basic research where you don’t know what the outcome is liable to be. When we started we had no notion of any of this."
Genes have been around as long as life on Earth, but it wasn’t until Gregor Mendel started crossing garden pea plants in the 1850s that the idea to scientifically scrutinize the mechanisms of heredity grabbed hold. It took another century for DNA to be identified as the key substance involved. And only in the last decade have scientists started to apply this knowledge to specific problems.
DNA research now stands poised to transform biology, agriculture and medicine — not to mention society itself. The nation’s grocery stores already are stocked with produce created by splicing genes from one plant into another to strengthen their resistance to drought, disease or decay. Pharmaceutical firms are exploring genetic modification of animals to produce human proteins for drugs. And hundreds of trials are testing the idea of inserting corrective genes into people to treat an array of ailments.
As this era begins to unfold, UF is stepping up its commitment to the field through the Genetics Institute. Approved by the Florida Board of Regents last year, the institute is designed to foster collaborations among faculty members scattered in departments throughout the university. More than 75 researchers, supported by $20 million in grants, are affiliated with the institute so far, and that number is expected to grow.
They include microbiologists, physicians, chemists, zoologists and agricultural scientists, as well as mathematicians and computer scientists. The institute incorporates existing programs, such as the Gene Therapy Center, the Program in Plant Molecular and Cellular Biology, the Center for Mammalian Genetics and the Program in Medical Ethics, Law and Humanities. It also is expected to spur industry partnerships to help translate UF research into commercial products.
Sharing a drive to investigate the genetic instruction manual to life, the researchers also are sharing resources, including vector production facilities, supercomputing capabilities, and core labs for DNA synthesis and sequencing. In the planning stages is a $40 million, 115,000-square-foot building that will be the institute’s permanent home. It is expected to be completed by 2005.
By that time, scientists should have a complete map of the human genome. But knowing a gene’s location is not the same as knowing its role.
"We have no earthly idea what many of the genes do," says Dr. Terence Flotte, interim director of the Genetics Institute.
Thus, much research focuses on functional genomics —figuring out which gene is assigned to do which job. That task unites many of UF’s scientists, because the investigative process is similar, whether it’s a plant or an animal.
"The actual computer hardware and software we need are the same, whether you’re talking about a human tumor sample or DNA extracted from corn," Flotte says. "So investments can pay off for people throughout the university."
The creation of the Genetics Institute comes at a time when scientists believe they finally have the tools and know-how to truly divine the secrets of the genetic code.
One major development fueling that optimism is DNA chip technology. Recent advances now allow scientists to explore the activity of thousands of genes at once rather than individually. That makes it much more feasible to compare gene expression, for example, in healthy tissues and tumor cells. The first faculty member recruited to the Genetics Institute, Frank Rosenzweig, will lead UF’s efforts with this technology as director of the planned DNA Microarray Facility.
"We’ve been cutting our teeth on diseases that from a genetic standpoint are simple, like cystic fibrosis, which involves just one gene," Flotte says. "But most diseases involve many genes, often affected by a big slice of environmental influence. Many genes interacting in complex networks somehow get thrown out of balance, leading to uncontrolled cell division, such as in a tumor, or to premature cell death, as in the brains of Alzheimer’s patients.
"When we can go in and look at all these genes simultaneously, we’ll be able to understand those diseases much better and design treatments much more effectively and much more rationally."
The advance also eases the comparison of species. In the College of Liberal Arts and Sciences, faculty members are studying the history of life on Earth to understand how plants and animals evolved and how particular genes have aided survival.
"We have a wide variety of mammals on the planet, and we’ve all had to experience the same sorts of epidemics and environmental problems," says Mike Miyamoto, associate chair of zoology, whose research recently demonstrated a surprising link between bats and cattle. "Embedded within gene codes are success stories, examples of how different species have adapted and overcome the same problems."
It has been more than 20 years since Kenneth Berns first mentioned to Nicholas Muzyczka that AAV could be a potential gene therapy vector. While many conversations about science go nowhere or hit unexpected roadblocks, that particular discussion is beginning to bear considerable fruit.
"AAV has all the properties that would be required to treat a chronic disease or a genetic disease, in that it has good efficiency for entering cells, good stability once it gets a gene into the cell, and the gene that gets ‘turned on’ tends to stay activated as long as the cell is around," says Flotte, who was the first to use AAV to deliver a corrective gene to a person. "It also has a tremendous safety advantage over other viral gene transfer vectors."
Unlike some other vectors, AAV has not been linked to any side effects. In fact, an estimated 80 percent of humans live with the virus in their system, with no apparent illness.
Seeing the promise of AAV, UF officials committed $5 million five years ago to the creation of the Vector Core Lab, where technicians could produce a steady stream of purified AAV for use by researchers. That lab has now been supplemented with a larger facility at UF’s Brain Institute that meets strict U.S. Food and Drug Administration rules for production of materials that can be used in people.
The university soon will begin developing a stock of AAV that will serve as the national standard; any organization interested in using AAV as a gene therapy vector will compare its supply to UF’s. Samples of the UF batch will be available through a national repository in Rockville, Md.
"We will be setting the benchmark for the production of this material," Flotte says. "It’s a recognition that we’ve accomplished something here that other centers can learn from."
UF researchers, however, are not stopping with AAV: They are working to add other viral and nonviral carriers to their gene therapy arsenal. While AAV can deliver genes into many kinds of tissue, including nerves, muscle and eyes, other vectors might be more effective in the liver and heart or be more suitable for carrying larger amounts of genetic material.
"Each carrier will find its niche," Muzyczka says.
With solid evidence that the AAV vector can deliver genes safely and effectively, "Now it’s kind of a mad rush to say, ‘Okay, what other genes can we put into it? What other diseases will it work for?’" Muzyczka says.
At UF, physicians are using AAV in a gene therapy trial of cystic fibrosis patients. The first round of the study demonstrated the technique was safe. In a continuation of that research effort, 20 patients have begun receiving a stepped-up dose of the corrective gene at Shands at UF medical center.
The coming years, UF scientists predict, will bring the invention of thousands of genetically engineered pharmaceutical products, with many using the UF-patented AAV vector or other carriers developed here as their base.
"We’re beginning to see the future," says Henry Baker, a UF microbiologist whose research on yeast gene regulation has been able to progress quickly because of DNA chip technology. "The sun is still at the horizon, but it’s coming up very fast."
Vice President for Health Affairs and Dean, College of Medicine
Acting Director, UF Genetics Institute, and Associate Professor, Department of Pediatrics
Director, Powell Center for Gene Therapy, and Professor and Eminent Scholar,
Department of Molecular Genetics & Microbiology
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Retinitis pigmentosa — Alfred S. Lewin, a professor of molecular genetics and microbiology, and William Hauswirth, an eminent scholar and professor of ophthalmology, molecular genetics and microbiology, are using AAV-based gene therapy to fight this common inherited form of blindness by delivering corrected genes to the nervous system.
Spinal Cord Injury — Paul J. Reier, an eminent scholar in neuroscience and neurosurgery, is researching how to modify spinal cord cells to improve the success of spinal cord grafts, or to actually alter spinal cord tissue to induce nerve cells to regenerate and reform the spinal cord.
Hypertension — Scientists Mohan Raizada, Craig Gelband and Mike Katovich used a form of gene therapy to block the action of a harmful hormone, warding off high blood pressure in rats. The approach apparently permanently altered the animals’ DNA blueprint, preventing their offspring from inheriting the disorder.
This represented the first time researchers have been able to protect future generations through gene therapy for any condition. The research could be a first step toward improving the treatment of, or even preventing, high blood pressure and related health problems in humans.
Alpha-1 antitrypsin deficiency — Flotte is working with Mark Brantly to use AAV to transfer a key gene into muscle in mice that are models for alpha-1 antitrypsin deficiency, which is associated with the development of early emphysema and severe liver disease. This method appears to replace a crucial protein that protects the lungs from the destructive action of this often-fatal disease.
Obesity — UF scientists have successfully used gene therapy to control appetite and weight in obese animal models. While testing in humans is years away, the research holds promise that a single injection may someday be a viable option for treating obesity.
Infections — Lyle Moldawer, a professor of surgery, and Richard Moyer, professor and chair of molecular genetics and microbiology, are testing short-acting adenoviral vectors that express anti-inflammatory drugs, with the hope of treating life-threatening infections such as sepsis.
Heart Attack — M. Ian Phillips, professor and chair of physiology, and Jawahar Mehta, a professor of medicine, physiology and cardiology, are using gene therapy in animal studies to block the action of the hormone angiotensin in an effort to protect the heart from the ravages of reduced blood flow. The treatment, the first application of gene therapy to the type of injury associated with a heart attack, also guards against the damage ironically caused when restoration of blood flow ferries a destructive oxygen molecule to the heart muscle.