The anti-HCV properties of Spn4A.RRLL(s) were confirmed and extended by further virological studies on cells pre-treated with our serpin-based inhibitors for 48 hours prior to 72 hours of HCV infection ( Figure 5B and 5C). First, quantitative Western blot analysis revealed a 64% reduction in the expression of intracellular HCV core protein in Spn4A.RRLL(s)-expressing cells compared to the control ( Figure 5B ). Similarly, Spn4A.RRLL(s) treatment was found to reduce extracellular infectious HCV titers by 76% ( Figure 5B) . A 65% reduction in intracellular HCV RNA levels was also observed using quantitative PCR (QPCR analysis ( Figure 5C ). Spn4A.RRLL(r) expression did not significantly impact any aspect of the HCV lifecycle examined ( Figure 5A , 5B and 5C). These results demonstrate that inhibition of SKI-1/ S1P-mediated proteolytic activation of SREBP molecules using secretory pathway protein-based inhibitors is an effective antiviral strategy to robustly block HCV infection in Huh-7.5.1 cells.