A vaccine against the hepatitis C virus (HCV) may be on the market by 2010, a leading hepatitis C researcher told the Eleventh International Symposium on Viral Hepatitis and Liver Disease in Sydney, Australia, this week.
Dr Michael Houghton, Vice President of Hepatitis C research at Chiron and a co-discoverer of the hepatitis C virus in 1987, announced that an HCV vaccine developed by Chiron was entering clinical trials following positive results in animal studies. A vaccine for hepatitis E has also been developed and is being tested in human studies.
Hepatitis C vaccine
An estimated 120-180 million people are infected with HCV worldwide, and chronic hepatitis C is a major cause of illness and death in HIV-infected people. Available therapies for hepatitis C have limited efficacy and often cause severe side-effects.
As with HIV, efforts to make a vaccine have been thwarted by the ability of HCV to escape the body’s immune response by mutating during the course of infection.
“Recent developments, however, allow a much more optimistic view, “ Dr Houghton said. “The development of natural immunity following acute, resolving infection has now been demonstrated in humans and in the experimental chimpanzee model against both homologous [similar] and heterologous [different] viral strains. Furthermore, vaccination of chimpanzees has been shown to protect against the development of persistent infection,” Houghton said.
By triggering antibodies to HCV proteins (gpE1 and gpE2), the vaccine protected the chimpanzees from infection with a similar form of HCV.
However, the experiment involving different strains of HCV was not as successful. One of ten vaccinated chimpanzees did develop chronic hepatitis C after rechallenge.
In the latter study, the presence of antibodies did not necessarily correlate with protection. Instead, HCV-specific T cell responses were important in protecting against HCV.
Researchers have developed DNA and polypeptide vaccines which can induce the required HCV-specific CD4 and CD8 responses in chimpanzees. According to Dr Houghton, these cellular immune responses are broad and strong.
A vaccine which combines these technologies is due to enter phase I safety studies in the United States this year.
A Belgian company, Innogenetics, has already reported details of a phase I study of a vaccine on its website, but full details of the study have still to be published.
Hepatitis E vaccine in development
A vaccine against the hepatitis E virus (HEV) is at a similar stage of development. Hepatitis E affects about 25% of people in Asia, the Middle East, North Africa and Mexico. It causes an acute illness, with death occurring in less than 1% of all cases and in 20% of cases in pregnant women.
Dr R. Purcell reported that an HEV vaccine has stimulated strong immune responses in monkeys. When vaccinated monkeys were exposed to HEV, most did not become infected and none developed acute hepatitis. Clinical trials of the vaccine are now being conducted in Nepal.
Further information on this website
Houghton M et al. Prospects for vaccination against the hepatitis C virus. Eleventh International Symposium on Viral Hepatitis and Liver Disease, Sydney, symposium 4, 2003.
Purcell R et al. Hepatitis E vaccine: pre-clinical tests of immunogenicity, efficacy and safety in a primate model. Eleventh International Symposium on Viral Hepatitis and Liver Disease, Sydney, symposium 4, 2003.