Lupus autoantigen peptide (LAP), a derivative of the autoantigen La found in systemic lupus erythematosus (SLE) patients, spans amino acids 11-28 of La and functions as an antiviral peptide. It primarily blocks the hepatitis C virus (HCV) from interacting with internal ribosome entry site (IRES) trans-acting factors (ITAFs), notably the polypyrimidine tract-binding protein (PTB) and poly(rC)-binding protein 2 (PCBP2). In a Huh7 cell-based reporter assay, LAP at a concentration of 60 µM effectively hampers HCV IRES-mediated translation, a process reversible by adding recombinant forms of PTB and PCBP2.