Virus infection supports organ acceptance

Chronic hepatitis C virus infections are among the most common reasons for liver transplants. Because existing viruses also infect the new liver, the immune system is highly active there. Despite this, the new organ is not rejected, as scientists from the Helmholtz Zentrum München and the Technische Universität München (TUM) have now discovered. The long-term stimulation of the innate immune system by the virus actually increases the probability of tolerance.

Over 150 million people throughout the world suffer from chronic infection with the hepatitis C virus (HCV), which causes massive damage to the liver. Advanced liver diseases often necessitate liver transplants. In the new clinical study Dr. Felix Bohne and his colleagues studied together with Prof. Alberto Sánchez-Fueyo from King’s College London 34 hepatitis C patients at the Liver Unit of the University Hospital Clínic de Barcelona who had received new livers.

The researchers had two objectives here: first, they wanted to gain a better understanding of the mechanisms that enable the body’s own immune system to tolerate the new organ despite the HCV infection; second, they were looking for factors that could act as biomarkers for tolerance in the patients.

“If tolerance could be reliably predicted based on certain markers, many patients could stop taking immunosuppressants after a certain period of time,” explains Dr. Felix Bohne, lead scientist of the study. Patients must take these strong drugs after transplants. They suppress the immune system so that the body does not identify the new organ as foreign and reject it. For patients with hepatitis C, this is a particular burden, as they need a stable immune system after the transplant to control their chronic HCV infection.

Markers for tolerance
During the study, the patients stopped taking the immunosuppressants. They were observed for twelve months to see which of them could also tolerate the new organ without the drugs, and which of them did not. The scientists took liver and blood samples from the patients prior to and after the cessation of the drugs. Detailed immunological tests on these patient samples were carried out under the leadership of Prof. Ulrike Protzer of the “Immunmonitoring Platform” at the Institute of Virology. The scientists compared the patients with each other and looked for any differences that arose in tolerant patients only.

How is hepatitis C virus spread, is it contagious, and how can transmission be prevented?

HCV is spread (transmitted) most efficiently through exposure to infected blood.

The most common route of transmission is needles shared among users of illicit drugs.

Accidental needle-sticks in health care workers also have transmitted the virus. The average risk of getting HCV infection from a stick with a contaminated needle is 1.8% (range 0% to 10%)