Several clinical studies have found that hepatitis C virus (HCV) infection is associated with increased PCSK9 serum levels.562–564 PCSK9 negatively regulates the hepatocyte surface proteins (LDLR, SR-BI, VLDLR) involved in HCV entry in vitro.565 Meanwhile, HCV infection upregulates PCSK9 expression.566 This indicated a complex interaction between PCSK9 and HCV. This evidence concerns the gene PCSK9 and hepatitis A virus infection.