It turns out there's a silver lining to having hepatitis C (HCV), an infection that can badly damage the liver. According to a new study in Science Translational Medicine, the hepatitis C virus can suppress the immune response that causes the body to reject transplanted organs as foreign invaders.
Usually, transplant patients with viral infections are not included in clinical trials because their infection is thought to hamper the success of the transplant.
Felix Bohne, Ph.D., a researcher at the Helmholtz Zentrum München center for environmental health research in Germany, studied 34 patients with HCV who had recently had a liver transplant. Bohne showed that the patients could stop taking immunosuppressive drugs to prevent rejection.
His team found that the mechanism viruses typically use to avoid being detected by the immune system actually creates an environment that encourages transplant tolerance. In effect, the virus acts like an immunosuppressive medication. However, the same results have not been seen in animal studies of HCV.
The researchers say they are not sure if this protective effect occurs in transplanted organs in other parts of the body, but the results explain more about how chronic viral infections affect transplant patients. The findings could also change the way clinical trials are designed in the future.
“The main option now is to find out exactly how the virus can favor the immunologic tolerance and try to mimic this, in order to get a therapy which can induce transplant tolerance without the need for the virus,” Bohne said.
Can Other Viruses Do the Same Thing?
Bohne said that studies have shown the Epstein-Barr virus, for one, can make the outcome of an organ transplant much worse.
Many viruses have ways to get around our body's immune response, but on the other hand, most viruses are not as narrowly focused as hepatitis C, which only attacks the liver.
Another candidate could be the hepatitis B virus (HBV), but this virus has very effective camouflage, resulting in a very weak activation of the immune system, Bohne said. Chronic HBV infection also exhausts the body's protective T-cells, he explained. The team wants to see whether HBV can also create an immunosuppressed environment in the liver.
Is This the End of Hepatitis C?
Dr. Thomas Schiano, the medical director of adult liver transplantation and director of clinical hepatology at Mount Sinai Hospital in New York, is intrigued by the new research on weaning transplant patients off of immunosuppressive drugs. He is also excited by a range of new oral medications designed to treat hepatitis C, including Sovaldi, which, though expensive, boasts a cure rate higher than 90 percent.
“I suspect that more HCV patients will be considered for immunosuppression tapering now because of this article, but more likely because more patients will be able to be treated and cured of their HCV with the new generation of HCV oral agents,” Schiano said. “Once the HCV is cured, either before or after transplant, transplant physicians will feel a lot more comfortable in tapering immunosuppression, as if a rejection were to occur it would be somewhat easier to manage.”
He added that increasing immunosuppression in patients with active HCV infections could lead to an acceleration of the disease.
Dr. Melanie Ott, a professor at the University of California, San Francisco, said the new findings, if confirmed in future studies, could reshape the clinical management of HCV-infected liver transplant patients.
"It definitely raises interesting questions about the role of [immunosuppressive drugs] in [transplanted organ or tissue] tolerance and rejection," she said.