Peripheral immunization induces functional intrahepatic Hepatitis C specific immunity following selective retention of vaccine-specific CD8 T cells by the liver: Immunization induced intrahepatic HCV-specific immunity

It is believed that an effective HCV vaccine must induce strong HCV-specific cytotoxic IFNγ ⁺ CD8 ⁺ T cells able to migrate into and become fully activated within the liver, an organ known to suppress T-cell responses and induce tolerance. Given the importance of intrahepatic HCV-specific T cells in the clearance of acute infection, the goal of this present study was to determine if peripheral immunization was able to induce functional intrahepatic HCV-specific T cell-based immunity both in the presence and absence of HCV antigen expression within the liver. Using a novel HCV NS3/NS4A DNA vaccine, we show that peripheral immunization of C57BL/6 mice results in the formation of a large pool of fully functional HCV-specific cytotoxic IFNγ ⁺ CD8 ⁺ T cells within the liver and that these cells were highly enriched within the liver as compared with the spleen. Following hepatic expression of cognate HCV antigen using a previously described liver transfection method, we show that this pool of vaccine-induced HCV-specific CD8 ⁺ T cells retained its ability to become highly activated as shown by the upregulation of IFNγ and CC R5 expression, as well as by the clearance of HCV NS3 expressing hepatocytes. Taken together, these findings suggest that T-cell effector function is preserved within the liver and that selective recruitment of antigen-specific T cells to the liver may play a previously unappreciated role in the process of immune surveillance, which may be exploited for future T cell-based HCV vaccines.