By Rebecca Skloot
Cynthia Dunafon knows that taking part in a beginning trial of gene therapy for cystic fibrosis won't cure her. What she's hoping is that it will help her escape a lung transplant.
n a room full of painted butterflies, Dalmatians and paw prints, Cynthia Dunafon sits at a table with a steady stream of clear liquid dripping from her nose into a towel. Dunafon stares into the vanishing puddle, then blows on the drips so they slide off her nose rather than into her mouth. Meanwhile, an ABC camerawoman shifts her weight from one foot to the other, a reminder that this awkward moment is being captured for the world to see as “Fighting for Breath,” part of a series on the Discovery Health Channel that takes viewers inside Johns Hopkins.
Dunafon, a doctoral student at the University of Chicago, is one of six volunteers in a new gene therapy clinical trial for cystic fibrosis. The liquid running from her nose is being pumped through a catheter into her nasal canal because 21 days ago particles from a virus—it’s called an adeno-associated virus (AAV)—were inserted into Dunafon’s nose and lungs by Pamela Zeitlin, an associate professor of pediatrics at Hopkins, and a team of researchers. The scientists are hoping this will become the first step in a pace-setting approach to helping patients born with the treacherous lung disease that afflicts Cynthia Dunafon.
The AAV, the researchers explained to Dunafon, would act as a “viral vector” for the gene therapy. But Dunafon is famous as the patient who asks questions–-she interviews her interviewers and corners doctors with queries—and she wanted to understand what that meant. Viruses, she learned, have the unique ability to enter a cell and integrate into a host’s DNA. They therefore offer a splendid transportation system for delivering therapeutic genes into a patient’s body. In Dunafon’s case, the gene the virus would transport would be a cystic fibrosis transmembrane regulator called CFTR.
All humans have the CFTR gene, and when it’s functioning normally it’s a marvel. It creates cellular chloride channels that regulate salt concentrations in the lungs. But Dunafon, like everyone else with cystic fibrosis, inherited mutated copies of the CFTR gene, so her channels don’t work correctly. The regulation of the sodium and chloride in her body is faulty. And since chloride movement is indirectly tied to water flow, if there’s no chloride, there’s no water. Thus the lack of moisture in the air passages of her CF-infected lungs. The result is that in people like Dunafon who have this disease, mucus is thick, more like rubber cement. Instead of working to protect their bodies, as mucus was designed to do, it clogs their airways and glands. And because their mucus-dependent organs face continual problems, they battle chronic infections. In people with CF, their bowels stop, their lungs become infected and obstructed, and in many cases, they don’t live beyond their teens or twenties. This is something Hopkins gene therapists hope to change by using AAV to transport a healthy CFTR gene into the bodies of these patients. And that is why Cynthia Dunafon just this morning caught a plane from Chicago to Baltimore and is now undergoing this wet procedure at Johns Hopkins.
Dunafon is fascinated by what’s happening to her, and she’ll talk to you about it for hours. She speaks with lightning speed. Her voice is naturally soft and congested from the mucus that comes with CF, and it quivers slightly when she speaks. She sounds like she’s bursting with more ideas than language will let her convey, which has something to do with her schooling and the intensity with which she’s been taught to question the world.
She is working on her Ph.D. in the Committee on Social Thought at Chicago. “We craft our own program,” she explains. Hers deals with a combination of issues in biblical interpretation, hermeneutics and the impact of psychoanalysis on literary criticism. Aside from the fact that she spends at least an hour each day inhaling medications and sitting in a vibrating vest to loosen mucus, she is a typical graduate student. She has an apartment, a cat, a boyfriend and a dissertation to write. Her life is full of stress. She doesn’t get nearly as much sleep as she should or find time to exercise and she dreams of finishing school and teaching at a small liberal arts college.
The difference between Dunafon and other grad students is that when summertime comes, against her boyfriend’s urges to stay home where she can safely work on her dissertation, she hops on a plane every week and flies to Baltimore. And unlike students who volunteer as “normals” in clinical trials for money, Dunafon is not a normal.
"I watch evidence of my disease come out on a graph that’s completely divorced from the mucus I feel in my lungs, and my mind says, oh yeah, I have a disease. It’s living confirmation of my disease in a way that’s different from a DNA test. There I give some blood and get back a sheet of paper saying, you have this mutation in your genes, but to actually see a graphical representation of your disease as it’s happening in your body is a powerful reminder that you’re not normal.” The first time Dunafon saw a printout from a test and heard this is within CF range, she was jolted into reality.
“It was an awakening experience,” she says, “it was worth doing the entire trial for me.” But having her disease crystallized wasn’t the reason Dunafon volunteered.
When Cynthia Dunafon arrived at the Hopkins Pediatric Research Unit so ABC could film the trial, she stepped onto a scale with a giant smiley face across its front. Pamela Zeitlin examined her in a room decorated with bright multicolored handprints that attract the young patients who come here. Cartoon characters giggled on a waiting-room television. This is probably the most time Dunafon will spend in a pediatric ward. She decided she will never have children.
Her lungs had been damaged after two bouts with pneumonia when she was 12. At the time, the doctor’s initial response had been disbelief. Those things only happened to old people, he told her. The day she learned she had CF, Dunafon’s parents stood grim in the corner of the exam room as she raised her hand to eye level and stared. “I just stood there,” she remembers, “looking at my hand and thinking, every cell is wrong.”
Cystic fibrosis is a recessive disorder. To actually have the disease, a child must inherit one copy of the mutated CFTR gene from both her mother and father. If both parents are carriers like 10 million Americans are, they have one normal and one mutated CFTR gene, but no signs of disease. There’s a 25 percent chance they will have a child with CF. If a child inherits the gene from only one parent, she too is a carrier.
“I learned about carriers and recessives the year after my diagnosis, about estimated carrier rates in the population,” Dunafon remembers. “During that year, I made the decision that I would never bear any children. I wasn’t willing to risk even having carriers.” As far as anyone knows, Cynthia is the only one in her family with CF. Her grandfather had CF-like problems, a fragile life filled with respiratory and digestive problems, but no one knows for sure. “I hold my breath when cousins and other relatives are born, because I’m always wondering, when is it going to show up again?”
Questions like this drive some CFers to volunteer for clinical trials where they don’t stand to benefit from the results. “Often times,” says Lois Brass-Ernst, clinical research coordinator for the study, “they do it to make a contribution to others. Many know they might not live to see the long-term benefit of it, but most have a niece, brother or cousin with CF who will. Some do it for a sense of hope, others for a sense of community.” Dunafon is motivated by a quest for knowledge. She doesn’t own a television and is generally against them, but she will probably go to a friend’s house to watch herself on Discovery Health. “More than anything,” she says, “I want to watch the final result, sit back and think, ‘Okay, what can a relatively educated layman with CF say from the inside out that isn’t being said by the media.’”
Before the trial began, Dunafon was annoyed with all the media coverage gene therapy has received. “I’ve been continually frustrated by the lack of informative reporting—it’s either extremely simple, extremely broad, or it’s too technical. I want to know more, and I think other CFers do too.” So she volunteered for a gene therapy trial. “I wanted to get underneath the media,” she says. “I wanted to be able to ask questions to the people on the cutting edge of research.”
AAV, the viral vector that’s being used to transport the healthy CFTR gene into Dunafon’s body, borders on being undetectable by the human immune system. In its natural state, it doesn’t cause disease in humans and requires a “helper virus” to reproduce itself. Because of this, and the fact that all viral genes are removed from AAV before it’s used as a vector, William B. Guggino, the professor of physiology who directs the CF Gene Therapy Program, says the potential for toxic reactions in patients is minimal. Guggino fashioned this CF gene therapy trial that Zeitlin is conducting on Dunafon after years of work in the laboratory. “Even when researchers tried to induce toxicity in the laboratory, they couldn’t do it,” he says. Any kind of drug, if taken in an overdose, can be toxic. But with this virus, we never could find a toxic level.” Guggino is pretty sure that, if he and his colleagues can deliver normal copies of CFTR into the cells of patients with CF, they will effectively repair their faulty chloride channel function.
Until they succeed, however, if you were to lick Dunafon’s arm, it would taste saltier than most people’s. It’s one way to determine how well someone’s CFTR channels are transporting salt throughout the body. A more socially acceptable way is through a nasal potential difference (NPD) test. Because sodium and chloride are both negatively charged molecules, their concentrations can be determined by measuring the electrical charge within a patient’s nasal canal. This is the test that’s being performed on Dunafon now as she sits patiently with liquid streaming from her nose.
At the moment, Dunafon is in the first stages of her weekly NPD test. Her sodium and chloride channels are being blocked and unblocked while a machine registers the charge in her nose. Brass-Ernst, who’s responsible for orchestrating this clinical trial, straightens out the plastic tubing to make sure the liquid flows smoothly. She sits across from Dunafon, the two so close their foreheads almost touch. Brass-Ernst looks over her shoulder at the camerawoman in the corner, who asks her to explain each step of the test to Dunafon for the benefit of the camera.
“Can I explain it to Cynthia?” Brass-Ernst laughs, “She’s an old pro at nasal PDs. She taught me how to do it years ago. Okay,” says Brass-Ernst in a perky I’m-on-camera tone, “What we need to do today, Cynthia, is take a measurement of the chloride channel activity across your nasal mucosa. It’s a way of looking at the effectiveness of the gene vector that we put into your nose.” She wipes Dunafon’s arm with an alcohol swab and continues. “To do this procedure, I drip certain solutions onto your nasal mucosa and measure how much electrical activity your nose puts off.” With a quick jab, Brass-Ernst slides a needle into Dunafon’s arm and says, “I make a circuit from your arm, back to your nose, and read your electrical activity.”
Brass-Ernst slides a pair of goggles over Dunafon’s eyes. “I’m putting these on your eyes because, when I’m sure the catheter is placed correctly, I’m going to secure it to the glasses.” Dunafon coughs and nods, and the two women exchange a mischievous glance. There was a day not long ago, before they thought of the goggles, when Brass-Ernst herself used to hold the catheter stock-still in the air through the several-hour procedure. This was back when the test could take five hours, when doctors sometimes sat in the patient’s chair with tubes in their noses, trying to figure out why the machine wasn’t working.
The attention surrounding the CF trial at Hopkins comes at the tail end of a solid year of intense debate over gene therapy. Starting in September 1999, with the death of young Jesse Gelsinger, a volunteer in a gene therapy trial at Penn, gene therapy and its proponents have been thrown into a media spotlight. But just as the debates grew more heated, gene therapy began to show its first hints of promise. Within one year of Gelsinger’s death, gene therapists reported their first success.
In a trial for infants with severe combined immunodeficiency, a disorder that’s deadly unless patients are confined to germ-free environments for life, two children who received gene therapy led normal lives following treatment. In other trials, gene therapy showed promise for treating hemophilia and certain cancers. “In the history of developing therapies, this is how things progress,” says Guggino. “There’s a lot of learning that goes on, so progression often goes in spurts.” Burgeoning therapies face highs and lows. Right now, Guggino says, gene therapy is at a junction between down and up. He’s pretty sure it will continue for the better.
“I’m very positive about gene therapy. I think it’s going to work because the idea is really sound, and the potential benefit is tremendous.”
Guggino, who is vice chairman for gene therapy in Hopkins’ Institute for Medical Genetics, has been using cell culture and animals to develop the ideas behind this trial since about 1989, the year the CFTR gene was identified. Through this work, he knows that, by loading AAV vectors with copies of normal CFTR genes, he can deliver them directly to cells. Once delivered, the vector and the functioning CFTR gene integrate themselves into the host’s DNA, allowing sodium and chloride to pass through the cell membranes at a normal rate.
“The difference between current treatments for cystic fibrosis and what we want to do with gene therapy is that current therapies treat the symptoms. Gene therapy would go right to the cause, the mutated gene.” Guggino knows the potential is there. But before he can determine its effectiveness in humans, he and his colleagues must prove their methods safe, which is where volunteers like Dunafon come in.
The two things volunteers in this trial have in common are that they all have CF, and none will be cured, or even helped, by this study. Each patient received only one dose of the vector in small areas within their noses and lungs, so even if the therapeutic gene successfully replaced faulty CFTR channels, it would do so only locally. “We’re primarily looking to make sure there are no side effects in the areas that got the virus,” says Zeitlin. “At the same time, we’re looking at function with the hope that we might see a hint of change with even a single dose of the vector. But realistically speaking, when you only get one dose of a drug in a Phase I trial, you don’t expect to see a change.” Phase I clinical trials are designed solely to establish the protocol’s safety. And the patients know this.
“I’ve read enough about the lives of people with CF to know that the future always holds a wild card,” says Dunafon. “It’s possible to be mild for life and then pick up a virulent bug and find that life is completely turned around. I’m hoping I receive enough medicine so that I can avoid a transplant permanently.”
In the end, those who most stand to benefit from this trial are CFers not yet born. “We hope to correct CF in children very early,” says Guggino, “because they are born with normal lungs.” For CF patients, the damage doesn’t start until thick airway mucus traps bacteria and begins what will become a lifelong struggle with lung infections.
“It’s not like a headache,” says Guggino, “where you take a pill and the problem goes away. With CF, you get a lung infection and you have reduced lung function. You can treat with antibiotics to get rid of the infection, but you never recover that lost functioning.” If a child loses, say, 2 percent of her lung’s strength with her first infection, her overall lung function will drop from 100 to 98 percent. “Ninety-eight percent is fine,” he says, “but the next time, maybe it drops to 96, then 90, then 88. It just keeps dropping. You can never reverse the destruction of the airways and that’s usually the cause of death.” Because of this, a CFer’s average lifespan is only 32 years. Dunafon is 36.