Tandem repeats of lactoferrin-derived anti-hepatitis C virus peptide enhance antiviral activity in cultured human hepatocytes

Previously, we found that bovine and human lactoferrin (LF) specifically inhibited hepatitis C virus (HCV) infection in cultured non-neoplastic human hepatocyte-derived PH5CH8 cells, and we identified 33 amino acid residues (termed C-s3-33; amino acid 600-632) from human LF that were primarily responsible for the binding activity to the HCV E2 envelope protein and for the inhibiting activity against HCV infection. Since the anti-HCV activity of C-s3-33 was weaker than that of human LF, we speculated that an increase of E2 protein-binding activity might contribute to the enhancement of anti-HCV activity. To test this possibility, we made two repeats [(C-s3-33)₂] and three repeats [(C-s3-33)₃] of C-s3-33 and characterized them. Far-Western blot analysis revealed that the E2 protein-binding activities of (C-s3-33)₂ and (C-s3-33)₃ became stronger than that of the C-s3-33, and that the binding activity of (C-s3-33)₃ was stronger than that of (C-s3-33)₂. Using an HCV infection system in PH5CH8 cells, we demonstrated that the anti-HCV activities of (C-s3-33)₂ and (C-s3-33)₃ became stronger than that of the C-s3-33. Furthermore, using a recently developed infection system with a VSV pseudotype harboring the green fluorescent protein gene and the native E1 and E2 genes, we demonstrated that the antiviral activities of (C-s3-33)₂ and (C-s3-33)₃ were stronger than that of C-s3-33. These results suggest that tandem repeats of LF-derived anti-HCV peptide are useful as anti-HCV reagents.