Novel Hepatitis C Vaccine Shows Some Early Promise
But any clinically valuable treatment is years away, researchers say
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Wednesday, January 4, 2012
There is currently no vaccine for hepatitis C, which afflicts an estimated 170 million people worldwide.
Like HIV, the hepatitis C virus mutates easily and has always been considered a difficult pathogen to immunize against because it's constantly changing. However, preliminary research by British and Italian scientists suggests that the virus might one day be beatable due to a novel approach.
The researchers treated 41 healthy volunteers with a vaccine designed to generate a response by T cells (infection-fighting cells) against the virus' internal proteins, instead of aiming to create an antibody attack on the ever-changing outer coat of the virus. Study lead author Dr. Paul Klenerman, a senior research fellow at Oxford University's Nuffield Department of Clinical Medicine, said the new vaccine is based on research by a biotech company in Italy. The researchers are calling it the first clinical trial of a hepatitis C vaccine in humans.
The inside of the virus is much more stable than its outer coat, Klenerman explained, and it's also headquarters for "crucial pieces of machinery." He said the researchers used a chimpanzee-based adenovirus (similar to the common cold virus) as a method of vaccine transmission, and were able to prime a large cellular immune response against hepatitis C that lasted for a year -- the length of the study.
But many questions remain to be answered, Klenerman said. "At the moment the trial is just Phase 1 and it looked at safety and an appropriate dose. It needs to go through at least a Phase 2 trial to show whether it's protective. That trial would probably take two or three years," he said.
Klenerman added that even if the researchers do develop a safe, effective vaccine, it's not certain whether it would protect against different strains of hepatitis C.
"This vaccine is based around one particular genotype -- or strain. The virus itself is very variable. So there's a chance that even if it works well against one strain, it could be less effective against other strains. Viral variation is really a big challenge," he said.
The study is published in the Jan. 4 issue of Science Translational Medicine.
Commenting on the trial, Dr. Andrew Muir, director of gastroenterology and hepatology research at the Duke Clinical Research Institute, said: "It's a novel approach toward a vaccine we've never had much enthusiasm for. We'd been told it's unlikely there would be a hepatitis C vaccine."
Muir said that, while many questions remain, if a hepatitis C vaccine were developed, it would be a boon. "Treatment is incredibly expensive," he said, with the current cost ranging from about $50,000 to $100,000.
Dr. Bruce Bacon, professor of internal medicine in the division of gastroenterology and hepatology at St. Louis University School of Medicine, said the payoff from such a vaccine is likely years away. "It's early yet and a lot has to be done to prove efficacy. If you can develop a vaccine that's effective, you can significantly reduce the burden of disease, but maybe the burden of disease 20 years from now."
Prevention and screening efforts, and developing effective medications may be more practical areas of focus for now, Bacon said.
People are risk of hepatitis C infection include those on long-term kidney dialysis; have regular contact with blood at work (such as health-care workers); and those who use injectable street drugs, according to the U.S. National Institutes of Health.
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