HCV-NS3Th1 minigene vaccine based on invariant chain CLIP genetic substitution enhances CD4+ Th1 cell responses in vivo

Background: HCV is a major cause of chronic liver disease, cirrhosis, hepatocellular carcinoma and death of end-stage liver disease worldwide. Therapy regimen based on IFN-alpha combined with ribavirin can induce a sustained virological and biochemical response in 20-60% of treated patients depending on the HCV genotype, the virus load and the age of the patients. So the development of a preventive or a therapeutic vaccine is very desirable. Methods: Thirty female BALB/c mice of 6-8 weeks old were randomly divided into five groups of six each to receive injection with experimental vaccine (pHCV-NS3, pHCV-NS3-Th1) and experimental controls (saline, pCI-neo, pCI-neo-Ii), respectively. After the fifth immunization, humoral and cellular immune responses were estimated. The therapeutic efficacy was also evaluated with BALB/c mice carried tumor cells expressing HCV-NS3 protein. Results: Specific antibodies to HCV-NS3 could be detected only in pHCV-NS3 immunized group. The antibody titers reach up to 1/1024. For CD4(+) Th cell proliferation assay, only the pHCV-NS3 and pHCV-NS3-Th1 treated groups were positive according to absorbance assayed at 450nm. The absorbance of the pHCV-NS3-Th1 treated group was significant higher than that of pHCV-NS3 treated group (P < 0.01, 0.002). Only the pHCV-NS3-Th1 immunized group produced detectable IFN-gamma, the concentration was 33.65 pg/ml. For IL-4 detection, only pHCV-NS3 immunized group produced tiny IL-4 cytokine, the concentration was 4.55 pg/ml. pHCV-NS3 and pHCV-NS3-Th1 immunized mice showed significantly lower tumorigenesis rate and higher survival rate compared to experimental controls, but no significant differences were observed in our experiment between the two vaccine immunized groups. Conclusions: Minigene vaccine based on invariant chain CLIP genetic substitution might be a potential candidate for HCV therapeutic vaccine development. The results might also have some inspiring significance for the therapeutic vaccine development against other chronic infectious diseases and tumor. (c) 2006 Elsevier Ltd. All rights reserved.