Question
What is the prospect of a vaccine against the hepatitis C virus?
Response From the Expert
Adrian M. Di Bisceglie, MD, FACP
Professor of Internal Medicine and Interim Chairman, Saint Louis University School of Medicine, St. Louis, Missouri; Chief of Hepatology, Co-Director, St. Louis University Liver Center, St. Louis University Hospital, St. Louis, Missouri
In the past 2 decades, we have seen enormous progress regarding the development of vaccines against viral hepatitis. More specifically, safe and effective vaccines against hepatitis B have been available for about 20 years and universal infant vaccination is routine in many countries. A similarly safe and effective vaccine against hepatitis A has also become available and, although it is not recommended for universal infant vaccination, it is widely used among travelers and other individuals at risk for infection with the hepatitis A virus. More recently, very promising results have been announced for a prospective vaccine against hepatitis E. This form of viral hepatitis is responsible for epidemics of severe and sometimes fatal illness in less developed countries.
Over the same period, there has been a dramatic decrease in the number of new cases of viral hepatitis (hepatitis A, B, and C) in the United States, thought to be due to broad public health measures, including vaccination. However, certain populations in the United States and in other countries remain at risk of hepatitis C virus (HCV) infection, providing the impetus for development of a preventive vaccine against HCV. Some of the challenges to development of a vaccine have been that HCV seems to elicit a weak immune response in general; the fact that characteristics of protective immune response have been difficult to determine; and the considerable variability that exists between isolates of HCV, at both the nucleotide and protein level.
Nevertheless, some progress has been made and HCV vaccine candidates are being tested in humans. One of these consists of a recombinant form of the HCV envelope proteins (E1 and E2) expressed in mammalian cells. This vaccine elicits production of antibodies to HCV envelope proteins and offers partial protection to chimpanzees. More specifically, this vaccine seems to have the ability to protect experimental animals from becoming chronically infected, although it may not elicit sterilizing immunity. Some other vaccine candidates are composed of proteins from the nonstructural region of the HCV genome, which appears more capable of stimulating a cellular rather than humoral immune response. Finally, some vaccines are being tested for a potential role in the treatment of chronic HCV infection in addition to being preventive.
In summary, although progress has been made in developing a vaccine to prevent HCV infection, it still appears to be a considerable way off.