DNA immunization with fusion genes encoding different regions of hepatitis C virus E2 fused to the gene for hepatitis B surface antigen elicits immune responses to both HCV and HBV

AIM: Both Hepatitis B virus (HBV) and Hepatitis C virus(HCV) are major causative agents of transfusion-associatedand community-acquired hepatitis worldwide. Developmentof a HCV vaccine as well as more effective HBV vaccines isan urgent task. DNA immunization provides a promisingapproach to elicit protective humoral and cellular immuneresponses against viral infection. The aim of this study is toachieve immune responses against both HCV and HBV by DNAimmunization with fusion constructs comprising various HCVE2 gene fragments fused to HBsAg gane of HBV.METHODS: C57BL/6 mice were immunized with plasmid DNAexpressing five fragments of HCV E2 fused to the gene forHBsAg respectively. After one primary and one boostingimmunizations, antibodies against HCV E2 and HBsAg weretested and subtyped in ELISA. Splenic cytokine expressionof IFN-γ and IL-10 was analyzed using an RT-PCR assay.Post-immune mouse antisera also were tested for theirability to capture HCV viruses in the serum of a hepatitis Cpatient in vitro.RESUTLTS: After immunization, antibodies against bothHBsAg and HCV E2 were detected in mouse sera, withIgG2a being the dominant immunoglobulin sub-class. High-level expression of INF-γ was deuetected in cultured splenic cells.Mouse antisera against three of the five fusion constructs wereable to capture HCV viruses in an in vitro assay.CONCLUSION: The results indicate that these fusionconstructs could efficiently elicit humoral and Th1 dominantcellular immune responses against both HBV S and HCV E2antigens in DNA-immunized mice. They thus could serve ascandidates for a bivalent vaccine against HBV and HCVinfection. In addition, the capacity of mouse antisera againstthree of the five fusion constnucts to capture HCV virusses invitro suggested that neutralizing epitopes may be present inother regions of E2 besides the hypervariable region 1.

Comparison of Immune Responses against FMD by a DNA Vaccine Encoding the FMDV/O/IRN/2007 VP1 Gene and the Conventional Inactivated Vaccine in an Animal Model

Foot-and-mouth disease virus （FMDV） is highly contagious and responsible for huge outbreaks among cloven hoofed animals. The aim of the present study is to evaluate a plasmid DNA immunization system that expresses the FMDV/OflRN/2007 VP1 gene and compare it with the conventional inactivated vaccine in an animal model. The VP1 gene was sub-cloned into the unique Kpn I and BamH I cloning sites of the peDNA3.1＋ and pEGFP-N1 vectors to construct the VPI gene cassettes. The transfected BHKT7 cells with sub-cloned pEGFP-N1-VP1 vector expressed GFP-VP1 fusion protein and displayed more green fluorescence spots than the transfected BHKT7 cells with pEGFP-N1 vector, which solely expressed the GFP protein. Six mice groups were respectively immunized by the sub-cloned pcDNA3.1＋-VP1 gene cassette as the DNA vaccine, DNA vaccine and PCMV-SPORT-GMCSF vector （as molecular adjuvant） together, conventional vaccine, PBS （as negative control）, pcDNA3.1＋ vector （as control group） and PCMV-SPORT vector that contained the GMCSF gene （as control group）. Significant neutralizing antibody responses were induced in the mice which were immunized using plasmid vectors expressing the VP1 and GMCSF genes together, the DNA vaccine alone and the conventional inactivated vaccine （P〈0.05）. Co-administration of DNA vaccine and GMCSF gene improved neutralizing antibody response in comparison with administration of the DNA vaccine alone, but this response was the most for the conventional vaccine group. However, induction of humeral immunity response in the conventional vaccine group was more protective than for the DNA vaccine, but T-cell proliferation and IFN-？ concentration were the most in DNA vaccine with the GMCSF gene. Therefore the group that was vaccinated by DNA vaccine with the GMCSF gene, showed protective neutralizing antibody response and the most Thl cellular immunity.