Rejection hurts, but for organ transplant patients, it is more a question emotional it can be a matter of life and the death. Having waited for months, sometimes years, for a donor and survived a major surgery, transplant patients face a difficult battle to prevent their immune systems from rejecting their new organ. Now a new test in which the blood of a transplant patient is analyzed for DNA of the donor organ can alert doctors if a serious rejection began, allowing them to try to stop the process.
Approximately 40% of patients experience less transplant acute rejection episode in the first year after receiving an organ. Catch all major immunological reaction is early key to minimizing its effects, especially because most rejection episodes are reversible with a large dose of immunosuppressive drugs. But patients must typically undergo regular biopsies of their new body to monitor his condition; the procedure is both painful and expensive biopsies and also can damage the body, says Hannah Valantine cardiologist at Stanford University School of Medicine in Palo Alto, California. In 09, Valantine developed a noninvasive rejection test based on monitoring the immune system of a patient. AlloMap test became the first U.S. Food and Drug Administration-approved for heart transplants, but it still fails to catch about half of rejection events.
To capture the rest, Valantine recently headed back to the drawing board. This time, she enlists the help of biophysicist Stephen Quake of Stanford. Together they have developed a test which is based on the fact that the genome of a transplanted organ is distinct from its new host. The test monitors the DNA fragments released by the body in the blood when the cells of the tissue graft are naturally ventilated. To validate this strategy, the researchers tried their test stored blood plasma of organ transplant patients, some of whom had had rejection episodes confirmed. During a discharge event, the levels of circulating DNA of the donor organ rise, which represents on average 3% of free DNA in the blood of the recipient, rather than the typical 1%, the researchers report online today in Proceedings of the National Academy of sciences
Valantine hope this test can eliminate the need for regular biopsies as rejection control means. patients often have each month during the first year after transplantation. Instead, doctors would conduct confirmatory biopsy if the results of DNA tests were positive. The new test can detect "very low levels of DNA to predict the rejection," said Valantine, making this more sensible approach than the AlloMap test. If the test can alert doctors to a release earlier, she notes, they can "tinker" with the levels of immunosuppressive drugs rather than going with a "big-gun approach" that lowers the patient's immune system to the point they are at risk of infection and cancer.
Bruce Rosengard, surgical director of the heart transplant program at Massachusetts General Hospital in Boston, is cautiously optimistic about the new test. "Rejection of organs remains one of the main obstacles to successful transplantation," says -it. "Anything we can do to reduce the number of heart biopsies is a very positive development. ... I think this approach will gain ground quickly enough. "
Valantine hopes to have the new test available to doctors time of year, adding that she sees no reason it can not be used to detect the rejection of other transplanted organs.
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