Hepatitis C Virus: Genetic Characteristics, Advances and Current Challenges for Vaccine Development

Abstract

Hepatitis C virus (HCV) can escape immune response and has a high risk of chronicity due to its high replication rate, genetic heterogeneity (antigenic diversity), direct cell-to-cell transmission and lipoviroparticular masking. Nowadays, it is thought that HCV can be eradicated with new generation treatment strategies with success rate of 95%. However, the infection continues to spread via patients who are unaware of their illness or exhibit risky behaviors. In addition, treatment cannot completely eliminate HCV-related sequelae and only 10% of infected people have access to treatment. These realities show that treatment strategies alone will not be sufficient to prevent the spread of the virus. Although 20 years have passed since the discovery of HCV, there are still significant obstacles to the development of a protective vaccine. The leading challenges include; structural and genetic characteristics of the virus (high antigenic heterogeneity), the highly posttranslational modification of envelope glycoproteins, the inability to develop a suitable cell culture system until recently, the lack of immunocompetent small animal models, the difficulties in planning experimental models and clinical trials for the evaluation of vaccine efficacy, optimistic view that successful treatment can eradicate the virus, some technical difficulties and limited financial support. Despite all these limitations, there have also been promising improvements in the development of an effective preventive vaccine, which is the most cost-effective strategy to reduce mortality and morbidity associated with HCV infections worldwide. Some of these include; clearance of acute HCV infections in some of the infected individuals with immune response, new cell culture systems and small animal models, successful results in vaccine studies with chimpanzees, some vaccines have come to clinical trial stages, new opportunities offered by advances in vaccine technology and strategies. In this review article, it is aimed to emphasize the importance of a protective vaccine could be developed to prevent the spread of HCV infections. In addition, the current situation in vaccine development studies, the obstacles encountered and alternative strategies to overcome these obstacles are mentioned.