* Vaccine primes immune system to attack viruses
* Uses same science as Ebola shot being tested
By Kate Kelland
LONDON, Nov 5 (Reuters) - A new hepatitis C vaccine from GlaxoSmithKline based on the same technology as an experimental Ebola shot being fast-tracked through human trials has shown promise in early clinical tests, prompting strong and broad immune responses.
Researchers testing the vaccine -- the first hepatitis C vaccine to reach second stage clinical trials -- said their results in a group of 15 healthy human volunteers showed it was very safe and well tolerated, and generated immune responses of a strength never seen before in a vaccine against this disease.
"This is as good at it could be for a first go, and I'm optimistic that it will work (in second stage trials)," said Ellie Barnes, a professor at Britain's Oxford University who led the initial human tests.
She said results also bode well for GSK's experimental Ebola vaccine currently being tested in healthy volunteers in Britain, Africa and the United States, as well as another experimental Ebola shot from Johnson & Johnson.
The vaccines are based on similar science, using a common cold virus called an adenovirus to take the key ingredient into the cells.
The idea is that the adenovirus infects cells in a vaccinated person, causing them to take up genes from the target virus - be it Ebola or hepatitis C - and produce their proteins.
This primes the immune system to attack the proteins of the pathogenic viruses when an infection occurs.
"What's special about adenovirus vaccines is that they are trying to induce a totally separate part of the immune response -- the T-cells," Barnes explained in a telephone interview. "And T-cells target the inner machinery of a pathogen."
Publishing their results in the journal Science Translational Medicine on Wednesday, Barnes' team explained that the hepatitis C vaccine uses a "prime-boost" strategy with two separate vaccine formulations.
CLEAR THE VIRUS
The first, or prime, vaccine is based on a chimpanzee adenovirus called ChAd3 developed by the Italian biotech firm Okairos -- now owned by GSK -- to which genes encoding four proteins from hepatitis C are added.
The second, or boost, vaccine adds the same four hepatitis C genes to a different viral vaccine base -- a so-called modified vaccininia Ankara (MVA) virus.
Neither the adenovirus nor MVA is able to replicate, so they cannot cause infection. The four genes packaged up inside cannot cause a hepatitis C infection either.
An estimated 180 million people worldwide are infected with hepatitis C, a chronic infection where the virus stays in the body for many years. It is a leading cause of liver cirrhosis and can in some cases lead to liver failure and liver cancer.
However, around a quarter of people infected are naturally able to clear the virus from their body. This suggests it is possible for the body to mount an immune response to fight off the infection.
"In our lab we spent a lot of time looking at the immune response of people who are able to clear the virus," Barnes said. "We know from that work that you need a strong immune response that targets multiple parts of the virus and that is sustained over time -- and those are the characteristics that we've been able to reproduce in this vaccine trial."
Leading drugmakers said last month they will work together to speed the development of an Ebola vaccine designed to help beat a vast epidemic of the disease which has killed more than 5,000 people, mainly in Guinea, Sierra Leone and Liberia.
Clinical tests on GSK's vaccine and another from NewLink Genetics are under way, while human tests on J&J's vaccine will start in January. (Reporting by Kate Kelland; Editing by Tom Heneghan)
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