CLDN-1, a protein previously reported to be an HCV entry factor mediating infection of hepatic cells, as it has been determined by examining interactions between HCVpp and HCVcc preparations and Huh7.5 cells [14], was expressed only by hepatoma cells and by lymphoma-derived PM1 T cells, which are resistant to HCV infection unless activated [25]. The gene discussed is CLDN1; the disease is infection.