UF’s Genetics Institute awarded large federal grant to study gene therapy in the liver

In their quest to maximize the safety and effectiveness of gene therapy, University of Florida scientists have set their sites on the liver, the dark-red gland critical to hormone balance, blood sugar regulation and the creation and secretion of proteins.

With its starring role in so many biological processes, the 3-pound liver is vulnerable to attack by many diseases, making it a top candidate for experimental treatment with corrective genes. Yet liver-directed gene therapy was involved in last year’s highly publicized death of a young patient in Pennsylvania.

That’s why UF Genetics Institute researchers, with a new five-year, $5 million grant from the National Institutes of Health, are exploring an alternative method for carrying genes into the organ’s cells, using a molecular means of transportation known as a vector. The goal: Improve gene therapy techniques while simultaneously battling several devastating genetic diseases that affect the liver.

In the Pennsylvania case, scientists packaged the corrective genes into adenovirus, but the vector was then blamed for triggering a fatal inflammatory response. Scientists here are conducting animal experiments using an unrelated and apparently harmless vector called the adeno-associated virus. While AAV has been tried before in the liver, researchers have had limited success in coaxing enough of the organ’s cells to “take up” corrective genes to effectively treat a medical condition.

“We have this problem: On the one hand, the liver is really a prime site for trying to correct genetic and metabolic disorders,” said Dr. Terence R. Flotte, interim director of UF’s Genetics Institute. “On the other hand, it appears to be very sensitive to the toxicities of certain vectors. It’s also been difficult to get therapeutic levels of gene expression there. So it will be a major breakthrough if we can develop a safe and effective gene therapy using AAV directed to the liver.”

In its natural state, AAV dwells problem-free in most people. In contrast, adeno-virus naturally causes colds and other illnesses, though they are often mild. Recognizing the potential of AAV’s apparent innate harmlessness, UF’s Dr. Kenneth I. Berns and Nicholas Muzyczka, pioneered its use as a vector that could be modified to carry corrective genes into the body. In patients with cystic fibrosis treated at Shands medical center at UF, AAV has transported corrective genes into the nasal passages and lungs, with no apparent adverse effects.

In the new round of experiments, the researchers will use AAV in animal models of several genetic disorders that can damage liver function and cause a host of other problems.

The targeted diseases are alpha-1-antitrypsin deficiency, which can cause pulmonary emphysema and in some cases liver failure; phenylketonuria, more commonly known as PKU, which can lead to abnormal brain development and mental retardation; and Pompe’s disease, a fatal disorder caused by deficiency of a specific enzyme. Pompe’s is known as a glycogen storage disease because it results from excess accumulation of the carbohydrate glycogen in the liver.

“For alpha-1 and glycogen storage disease, we already have been working on gene therapy directed to other organs,” said Flotte, who is principal investigator on the grant and an associate professor in the College of Medicine’s departments of pediatrics, and molecular genetics and microbiology. “But we think we can get a more comprehensive effect against the problems of the disease by directing the therapy to the liver. For PKU, there simply isn’t any organ but the liver in which it makes sense to deliver gene therapy.”

One key part of the research is to continue efforts to tweak the AAV vector so that a higher percentage of liver cells incorporate the corrective genes. Past studies have shown that no more than 5 percent of liver cells begin following the inserted genes’ orders. But in preliminary research, UF microbiologists are beginning to see the potential for a much higher response rate, giving them hope that they can overcome the limits to successful gene therapy in the liver.

In addition to Flotte, other major players in this program include Berns, UF’s vice president for health affairs and College of Medicine dean; Muzyczka, director of UF’s Powell Gene Therapy Center; Mark Atkinson, associate professor of pathology; Dr. Barry J. Byrne, associate professor of pediatrics; Dr. James M. Crawford, chairman of the department of pathology, immunology and laboratory medicine; and Philip Laipis, professor of biochemistry and molecular biology.

The new NIH funding further bolsters the efforts of UF’s Genetics Institute, which was formed last year to foster collaborative research across many scientific disciplines at the university campus.

“We built our institute on the strength of our having national leaders in gene therapy and plant genomics,” Flotte said. “Our continued success in attracting grant money for these two lines of research will help all the related programs, because the funds contribute to equipment that can be shared, lifting all institute efforts.”