Some 3 percent of the world’s population is estimated to be chronically infected with hepatitis C virus (HCV). Unlike hepatitis A or B viruses, there’s currently no approved vaccine for HCV, meaning it represents a huge burden on global health. But a team of researchers based at Oxford University has been on the case, and promising results from their new human trial suggest an effective vaccine could finally be well within our grasp.
As described in the journal Science Translational Medicine, the vaccine induced strong and broad immune responses against hepatitis C virus, and was well tolerated in the volunteers. Moving forward, the vaccine is now being tested for effectiveness in intravenous drug users in the U.S., which is the furthest stage that a hepatitis C vaccine has reached in clinical trials so far.
Hepatitis simply means inflammation of the liver, and it can be caused by a variety of things such as drugs, alcohol and bacterial infections. Numerous viruses are also able to cause hepatitis, but the most common are hepatitis A, B, C, D and E viruses. Of these 5 viruses, A, B and C are responsible for the majority of infections worldwide. Although HAV infections are usually cleared from the body without treatment, HBV and HCV can establish chronic infections that can cause long-term liver problems, liver scarring and even liver cancer.
As mentioned, effective vaccines against hepatitis A and B viruses already exist, but scientists have struggled to achieve the same for HCV. That’s because HCV changes itself, or mutates, frequently, making it difficult to target individual viral components. However, the fact that 1 in 4 people infected for the first time are able to naturally clear the virus suggests that effective immune responses can indeed be mounted against it.
Further examination of these individuals revealed that a particular group of cells in the immune system, called T cells, play a big role in controlling the virus. Oxford University researchers therefore endeavored to develop a vaccine that is capable of eliciting a similar immune response against the virus in people.
To do this, they developed two different vaccines that were produced by adding genes for various HCV components to two different viruses. The viruses used are replication defective, so they can’t cause disease. The idea is that the genetic material is injected into host cells, which then produce viral proteins that stimulate the immune system.
The first vaccine was designed to prime the immune system, ready for attack, whereas the second acted as a booster to enhance the immune response.
The researchers tested their vaccines on 15 healthy volunteers, and they were found to induce strong and broad T cell responses that were sustained over a 6 month period. The T cells produced after vaccination, which were comparable to those seen in individuals that are naturally able to clear infection, targeted numerous different parts of the virus, which is very promising. However, it’s unclear at this stage whether the vaccine will be effective at preventing infection. Efficacy trials are already underway, which will provide some answers.