The mechanism by which variations in the genetic sequence near the gene encoding human interferon lambda (IFNL) are associated with clearance of the hepatitis C virus (HCV) is revealed in a report published online this week in Nature Immunology.

Ram Savan and colleagues found that one particular genetic variant produces more stable IFN-lambda messenger RNA and this leads to increased production of this anti-viral factor. The authors also find HCV tries to ‘escape’ the immune response by aiding in IFN-lambda degradation. Again, the ‘protective’ IFN-lambda variant is more resistant to this degradation process.

The identification of this resistant IFN-lambda variant may explain why certain patients successfully clear HCV following drug treatment whereas a significant minority remain chronically infected.