* 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 fromGlaxoSmithKline based on the same technology as anexperimental Ebola shot being fast-tracked through human trialshas shown promise in early clinical tests, prompting strong andbroad immune responses.
Researchers testing the vaccine -- the first hepatitis Cvaccine to reach second stage clinical trials -- said theirresults in a group of 15 healthy human volunteers showed it wasvery safe and well tolerated, and generated immune responses ofa strength never seen before in a vaccine against this disease.
"This is as good at it could be for a first go, and I'moptimistic that it will work (in second stage trials)," saidEllie Barnes, a professor at Britain's Oxford University who ledthe initial human tests.
She said results also bode well for GSK's experimental Ebolavaccine currently being tested in healthy volunteers in Britain,Africa and the United States, as well as another experimentalEbola shot from Johnson & Johnson.
The vaccines are based on similar science, using a commoncold virus called an adenovirus to take the key ingredient intothe cells.
The idea is that the adenovirus infects cells in avaccinated person, causing them to take up genes from the targetvirus - be it Ebola or hepatitis C - and produce their proteins.
This primes the immune system to attack the proteins of thepathogenic viruses when an infection occurs.
"What's special about adenovirus vaccines is that they aretrying to induce a totally separate part of the immune response-- the T-cells," Barnes explained in a telephone interview. "AndT-cells target the inner machinery of a pathogen."
Publishing their results in the journal ScienceTranslational Medicine on Wednesday, Barnes' team explained thatthe hepatitis C vaccine uses a "prime-boost" strategy with twoseparate vaccine formulations.
CLEAR THE VIRUS
The first, or prime, vaccine is based on a chimpanzeeadenovirus called ChAd3 developed by the Italian biotech firmOkairos -- now owned by GSK -- to which genes encoding fourproteins from hepatitis C are added.
The second, or boost, vaccine adds the same four hepatitis Cgenes to a different viral vaccine base -- a so-called modifiedvaccininia Ankara (MVA) virus.
Neither the adenovirus nor MVA is able to replicate, so theycannot cause infection. The four genes packaged up inside cannotcause a hepatitis C infection either.
An estimated 180 million people worldwide are infected withhepatitis C, a chronic infection where the virus stays in thebody for many years. It is a leading cause of liver cirrhosisand can in some cases lead to liver failure and liver cancer.
However, around a quarter of people infected are naturallyable to clear the virus from their body. This suggests it ispossible for the body to mount an immune response to fight offthe infection.
"In our lab we spent a lot of time looking at the immuneresponse of people who are able to clear the virus," Barnessaid. "We know from that work that you need a strong immuneresponse that targets multiple parts of the virus and that issustained over time -- and those are the characteristics thatwe've been able to reproduce in this vaccine trial."
Leading drugmakers said last month they will work togetherto speed the development of an Ebola vaccine designed to helpbeat a vast epidemic of the disease which has killed more than5,000 people, mainly in Guinea, Sierra Leone and Liberia.
Clinical tests on GSK's vaccine and another from NewLinkGenetics are under way, while human tests on J&J'svaccine will start in January. (Reporting by Kate Kelland; Editing by Tom Heneghan)
Glaxosmithkline (GSK)
