A novel approach offers hope for an HCV vaccine

An HCV vaccine is needed, but hard to develop. A structural mimic may be the key to enhancing our immune response

Globally, more than 70 million people were struggling with a chronic hepatitis C virus (HCV) infection in 2015. Although effective drugs are available to treat chronic infections, only 13% of cases received curative treatment. The fact that only 20% have been diagnosed is of even greater concern. Although a minority of newly-infected individuals (10–40%) manage to overcome the disease, most develop a chronic infection. Most acute cases of HCV are asymptomatic, leading to undetected virus transmission. Left untreated chronic HCV can lead to serious liver damage and an increased risk of liver cancer. As curative therapies alone cannot eliminate the virus, a vaccine is required. However, because HCV is very diverse and evolves rapidly to evade the immune system, developing an effective vaccine is challenging. In work recently published in npj Vaccines, scientists from the MRC-University of Glasgow Centre for Virus Research, the University of St. Andrews and Imperial College London describe an alternative strategy that uses a structural mimic to encourage the immune system to make antibodies that can recognise multiple strains of the virus i.e. broadly-neutralising antibodies (bNAbs) against HCV.

A moving target

With its high genetic diversity and an envelope of ever-changing glycoproteins, HCV is challenging for the human immune system to detect and counteract. The minority of cases in which the virus is successfully cleared from the body show a broad, strong T-cell response and neutralising antibodies during the early phase of infection. Individuals who have previously cleared an HCV infection have an 80% chance of successfully fighting off reinfection, indicating that a protective immune response has been induced and that vaccination is a realistic goal. However, with seven distinct genotypes and more than 60 subtypes, the genetic variation makes it challenging to produce a vaccine that would protect against all infections.