| |
Experimental Stem Cell Study in HIV+
|
| |
| |
High hopes for AIDS research
Experimental treatment fortifies the body's own stem cells with an enzyme that may block the relentless advance of the virus<
Sabin Russell, San Francisco Chronicle Medical Writer
Friday, April 7, 2006
Michael DeLane is about to celebrate a rare anniversary. On Saturday, it will be one year since he stopped taking all his drugs for AIDS.
Many patients have experimented with breaks from their AIDS medications, and a few of these have been able to keep their virus levels in check for a year or more.
What makes DeLane's case important is that he is among a small group of HIV-infected men and women participating in an unusual experiment. Half of them have had their own blood cells modified with a gene that blocks the virus.
Today, the 41-year-old San Francisco man is in good health and fine spirits.
If the experimental therapy is proved successful, it could raise the prospect that infected individuals could control the virus and maintain their health without having to spend a lifetime taking costly and potentially toxic drugs.
"It's possible that the stars are lining up on this one,'' said Dr. Jay Lalezari, a UCSF researcher who conducts clinical trials for drugmakers and has enrolled patients in this study. But he cautioned that the experience of a single patient has little scientific meaning. "The technology has proven itself in various ways, but we won't know the results of this trial until February,'' he said.
The goal of this experiment -- which combines elements of genetic engineering, gene therapy and stem cell science -- is to create a kind of parallel immune system that is fortified against the AIDS virus.
Like the 73 other participants in the clinical study, DeLane does not know for certain whether he was among the half who received the modified gene or was given a placebo. What he does know is that his T-cell count -- a measure of infection-fighting white blood cells -- has more than doubled.
Although he remains HIV-positive, the level of virus in his bloodstream is currently undetectable.
"It was such a burden to be lifted, to be no longer connected to the pills,'' said DeLane, a former Greenpeace activist now working as an administrator for the UCSF Medical Group.
DeLane was among the first to participate in the experiment, which he learned about because he has closely monitored HIV science since he became infected in August 2002.
Similar experiments are being carried out at UCLA and in Sydney, where the technique was developed by a small research company owned by Johnson & Johnson, the New Brunswick, N.J., medical giant.
Although DeLane was among the first to participate, the researchers have only recently performed the treatment on the last of their volunteers. Preliminary results of the trial won't be ready until February.
Johnson & Johnson spokesman Marc Monseau declined to discuss the treatment. "The trial is ongoing, and we prefer not to comment about ongoing trials,'' he said.
The secret of this new gene-therapy approach to controlling HIV is an enzyme called a ribozyme. It is a custom-built chemical "scissors," designed by Australian researchers, that cuts up one of HIV's nine genes just as the virus tries to replicate itself. Certain types of white blood cells are the natural target of HIV. But researchers believe that if these same cells are equipped with this man-made enzyme, they cannot be infected.
Because the body does not naturally produce this ribozyme, researchers had to come up with a way to cause blood cells to manufacture it. The answer was found in the emerging science of stem cells.
The stem cells chosen for this experiment are not the controversial kind found in human embryos, but grow naturally in bone marrow and float about in the bloodstream. They are literally the mother of all blood cells -- they morph into the many kinds of white cells that fight infection -- and are the favorite target of HIV.
Participants in the gene therapy experiment follow a procedure developed by the Australian scientists, led by Johnson & Johnson researcher Geoff Symonds.
First, the volunteers spend two eight-hour shifts hooked to a machine that filters out stem cells and returns the rest of their blood to their arm.
Next, the harvested stem cells are infected in the laboratory with a harmless mouse virus engineered to carry the ribozyme gene. The genes are a blueprint that tell the cell how to make the enzyme. Three days after the gene is transferred to the stem cells, they are returned to the patient's bloodstream. In subsequent weeks, these stem cells produce a variety of infection-fighting white blood cells, each containing the ribozyme that can ward off HIV.
(In the experiment, only half the subjects receive stem cells containing the gene. The rest receive unaltered stem cells as a placebo.)
The hope is that when HIV attempts to infect these fortified blood cells, the virus will be destroyed. As time goes by, these fortified blood cells would eventually outlive the natural blood cells -- and the patient would be left with a rebuilt immune system resistant to HIV.
DeLane was infused with either the treated blood cells or a placebo at a Stanford University Medical Center clinic in June 2004. He strongly believes that he received the treated cells, because for several months after the procedure his blood counts fluctuated wildly, as if a battle were going on in his immune system. Forty weeks after the infusion, he stopped taking antiviral drugs.
The Chronicle has learned that DeLane is not the only patient in the stem cell study to maintain undetectably low levels of virus, although the number is a closely guarded secret.
Word that some participants were doing well has been circulating among AIDS activists for several months. DeLane's experience with the Stanford trial is the first to be publicized -- but only because he chose to share the test results with reporters.
Perhaps the most intriguing development in his case was in February when the level of virus in his bloodstream jumped into the detectable range -- the first sign that perhaps the therapy was failing. But in March, the so-called "viral load" test slipped back into the undetectable range -- suggesting that DeLane's immune system, newly fortified or not, beat back the infection without any help from AIDS drugs.
"It's a fascinating case,'' said Dr. Steve Deeks, a UCSF researcher. Deeks was not involved in the clinical trial, but is an expert on the reaction of the immune system in HIV patients who stop taking their medications.
Deeks said it is possible that DeLane is one of those patients who can naturally control the virus without drugs, and his encouraging results may have nothing to do with the therapy. "Long-term control of the virus in the absence of treatment is rare, but it does happen,'' said Deeks.
Scientists involved in the study remain cautiously optimistic. Dr. Ronald Mitsuyasu, director of the UCLA Center for Clinical AIDS Research, is running the study in Los Angeles and collaborated with the Australian team on the first pilot test of the new therapy. It showed that the procedure was safe, and that the anti-HIV ribozyme installed in stem cells turned up in the many white blood cells that derived from them.
Researchers have improved the technique of transferring the gene to stem cells so that 90 percent of the harvested stem cells are returned carrying the ribozyme.
The AIDS scientist said he does not believe this type of therapy will ever fully replace effective antiviral drugs. However, "if we are intelligent in how we use the drugs with these immune therapy approaches, it could lead to extremely effective control of HIV,'' Mitsuyasu said.
|
|
| |
| |
|
|
|
