| Hepatitis C Virus (HCV) is a major cause of chronic liver disease, cirrhosis, hepatocellular carcinoma and death from end-stage liver disease. Approximately 170 million people suffered from this infectious disease, about 1-3% of total population worldwide. 55-85% of acute infections become persistent. In the less affluent, developing countries, the prevalence of HCV infection is often above the estimated global figure of 3% and may exceed 20% in some areas.HCV genome was first successfully cloned in 1989, which leads to great progress in the study of HCV. Now it is clear that HCV is a blood-borne enveloped RNA-containing member of the Flavivirus family, approximately 9.6 kb in length. It contains a single large open reading frame (ORF). The HCV ORF encodes a polypeptide of about 3010 amino acid residues. This polypeptide has been suggested to be proteolyticaly processed into 10 viral proteins. Among these proteins, C,E1,E2 and P7 were considered to be structure proteins, and NS2,NS3,NS4A,NS4B,NS5A,NS5B non-structure (NS) proteins. Though rapid progress had been obtained in molecular structure study of HCV, unfortunately, there is no preventive vaccine to date. Today's therapies based on IFN-α coupling with ribavirin can induce a sustained virological and biochemical response in less than 50% of treated patients, depending on the infecting genotype, the virus load and the age of the patient. So the development of a preventiveor therapeutic vaccine is very desirable.It has been suggested that T helper 1 (Thl) CD4+ T cell response to thenon-structural 3 (NS3) protein is present in acute infection patients who cleared HCV, whereas those who progress to chronic infection lack these responses. In established chronic HCV infections, CD4+ T cell responses to the NS3 protein are almost totally absent, whereas antiviral therapy appears to activate these responses. The N terminus of NS3 protein contains a protease domain that forms a tight non-covalent complex with the cofactor NS4A. The C-terminal two-thirds of the NS3 protein possess helicase and NTPase activity. These vital enzymatic functions may explain the limited sequence variation within the NS3 region and suggest that the NS3 protein may constitute a potential therapeutic vaccine candidate.In present study, we constructed a HCV-NS3 Thl epitope vaccine based on BALB/c mouse invariant chain (Ii) CLIP substitution. The CLIP segment of Ii was substituted by HCV-NS3 1248-1261 epitope, which was considered to be a epitope that has a wide specificity in MHCII binding characteristic. At the same time, antigen presenting molecules of BALB/c mouse were cloned. Binding characteristic of vaccine epitope to antigen presenting molecules was observed in eukaryotic cells. Then humoral and cellular immune responses of BALB/c mice were evaluated after inoculation of constructed vaccine candidates. At last, tumorgenesis mice expressing HCV-NS3 were established by inoculating SP2/0 cells which stably expressed HCV-NS3 protein. The efficiency of constructed vaccine was evaluated by inhibition of tumorgenesis. The results demonstrated:...
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