HCV affects 284,000 Australians, with up to 15,000 new infections every year. Up to 20 per cent of people with chronic hepatitis C develop cirrhosis of the liver.
Despite public health programs and anti-viral therapy, hepatitis C remains one of the most prevalent blood-borne infections in Australia.
Although 30 per cent of individuals can naturally clear the virus, the majority fail to eliminate HCV completely.
This discrepancy intrigues researchers.
“HCV may be amenable to a protective vaccine, since natural immunity does exist in the population,” says researcher Silvana Gaudieri.
“In fact, there are individuals who have been exposed to different HCV strains multiple times but who remain virus-free. These individuals may hold the key to unlocking the secret to obtaining a vaccine.”
By comparing individuals who have cleared the virus and those who have developed chronic hepatitis C, researchers hope to identify virus-specific T-cell responses.
However, the task is made more complicated by the fact that at least six strains of HCV exist. These strains, in turn, have different genetic profiles, with separate genotype variations.
“T-cell responses against one genotype may not be effective against another,” says Prof Gaudieri.
And then there is the added issue of viral adaptation.
T-cells recognise infected cells via a beacon comprised of part of the virus that has been digested in the cell and the human leucocyte antigen (HLA).
However, HCV is a highly mutable virus and can escape T-cell responses by mutating in the areas presented by the HLA molecule. In a sense the virus adapts to its host.
“Previous attempts to create a vaccine have been limited because like HIV, hepatitis C virus escapes our immune system by rapid changes of its genome and shape,” says researcher Michaela Lucas.
“Our project is using genetics to identify these escape patterns so we can create vaccines that take this ability of the virus to change, into account. That should mean a higher chance of success.”
(Source: Science Network Western Australia)