EXPRESSION AND IMMUNE-RESPONSE TO HEPATITIS-C VIRUS CORE DNA-BASED VACCINE CONSTRUCTS

Hepatitis C virus (HCV) is a major worldwide cause of acute and chroni c hepatitis, cirrhosis, and hepatocellular carcinoma, The development of vaccines against HCV have been complicated by the high variability of the envelope region, and it is Likely that the cellular immune resp onses to viral structural proteins may be important for eradicating pe rsistent viral infection. Recently, it was reported that the injection into muscle cells of plasmids encoding viral genes resulted in the ge neration of strong cellular immune responses, We constructed vectors t hat express the highly conserved HCV core gene, hn this regard, the pH CV 2-2 construct contained the entire HCV core region and pHCV 4-2 con tained both the 5' noncoding region and the core gene. Cellular expres sion of HCV core protein was assessed following transfection into huma n and murine cell lines, and higher intracellular levels of the 21-kd core protein were observed with pHCV 2-2, These HCV core DNA construct s were used to immunize BALB/c mice and produced low-level anti-HCV co re humoral immune responses, To assess cytotoxic T-lymphocyte (CTL) ac tivity generated in vivo a cloned syngeneic SP2/O myeloma cell line co nstitutively expressing HCV core protein was established and inoculate d into BALB/c mice to produce growth of plasmacytomas. Strong CTL acti vity was generated because the tumor size and weight in pHCV 2-2-immun ized mice were remarkably reduced compared with mice injected with moc k DNA. Spontaneous CTL activity was also exhibited by splenocytes in a n in vitro cytotoxicity assay. These investigations demonstrate that p lasmid constructs expressing HCV core protein generate strong CTL acti vity, as assessed both in vivo and in vitro, and are promising candida tes as antiviral agents.