More insight into the efficacy of a vaccine against Hepatitis C
7 May 2014
A vaccine to protect against a (life-threatening) infectious disease, aims to train the immune system in order to acquire the right weapons to combat an infection. It is becoming increasingly clear that the genetic background of the patient plays an important role in the efficacy of a vaccine. The immune system must not only attack the right part of the virus but it also needs to have access to the tools that are needed to do so. BPRC researchers have obtained new evidence for this in a study with stored cells from chimpanzees that were earlier vaccinated against Hepatitis C.
The Hepatitis C virus (HCV) causes irreversible liver damage in humans, and in most cases, it is not spontaneously removed by the immune system. Because the virus initially causes little or no clinical symptoms, patients are often late, sometimes after 30 years, faced with the fact that they are carriers of HCV. In the mean time, the virus can have caused (sometimes fatal) damage to the liver.
To date, there is no vaccine available that can protect people against HCV infection. Besides humans, chimpanzees are the only animals that can be infected with HCV in a natural way and therefore, ten years ago, the BPRC has tested a promising vaccine in these animals. Only one of the four chimpanzees that had received the vaccine was protected from prolonged infection. In humans this kind of protection would probably be sufficient to prevent liver damage and therefore it was important to examine why this single animal reacted differently than the other three. Experiments with apes are not longer allowed in the Netherlands, but using cells that had been stored in the freezer prior to the ban, still valuable experiments can be done. These experiments have shown that the immune systems of all four of the animals had been successfully trained to control the virus. However, the so-called cytotoxic T-cells from the protected animal were better equipped to attack the virus. This better equipment could be linked to a very small part of the genetic material of the individual chimpanzee, the MHC molecule called Patr-A* 0301. The importance of this finding, published in PlosOne, is underlined by the fact that HCV patients with a better prognosis contain a similar MHC molecule. This is the first time that the two genetic factors are connected with each other in the context of an HCV vaccine. Possibly it may be a step towards towards the development of an effective vaccine to protect people from the effects of an HCV infection.