The findings give hope to the 500,000 UK sufferers of the virus, which can infect the liver, and leads to permanent liver damage. About 20 percent of people infected with hepatitis C somehow clear the virus from their bodies without treatment. But about 3 million Americans remain chronically infected, at risk of eventually developing liver cancer or failure. The virus claims 10,000 to 12,000 U.S. lives annually.
The findings revealed that natural killer (NK) cells, a part of the human immune system, provide a central defence against HCV infection and this mechanism is mediated by inhibitory receptors expressed on NK cells and the partners or ligands for these receptors on liver cells.
Researchers identified a specific combination of genes Researchers identified a specific combination of genes in these individuals that directly confers protection against HCV. The genes are killer cell immunoglobulin-like receptors (KIR) and HLA class I genes and the favourable genes identified in the study are KIR2DL3 and group 1 HLA-C alleles.
Dr Salim Khakoo, lead researcher in this study commented: "These favourable genes control the functions of NK cells. NK cells are part of the innate immune system, a branch of immunity that has not been well-studied in HCV to date."
"KIR2DL3 on NK cells binds group 1 HLA-C alleles on liver cells and our worksuggests that this interaction is more easily disturbed in HCV infectionthan other KIR-HLA interactions."
The findings also suggest the amount of virus received is a factor. The mechanism that researchers have discovered is more important in people receiving lower infectious amounts of HCV. The protective effect of genes on the virus was observed in Caucasians and African Americans with expected low infectious doses of HCV, but not in those with high-dose exposure, in whom the innate immune response could be overwhelmed..
The findings could eventually lead to new treatment strategies for HCV based around NK cells in general and KIR2DL3/HLA-C in particular.
Dr Khakoo continued: "We believe that this study is a significant advance in the understanding of hepatitis C virus infection. There are other interesting outcomes from our research. It implicates NK cells, and the innate immune system in general, in clearing HCV infection and this has not previously been clearly documented. It also suggests that the more NK cells of the protective type that an individual has the more likely they are to clear HCV."
Their findings are set out in a paper published in August 6 edition of Science magazine.