Development and improvement of hepatitis B virus DNA vaccine by codelivery of various cytokine genes

• Main Authors: Chow,Yen-Hung, 周彥宏
• Other Authors: Tao Mi-Hua, Yang Wen-Kuang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/78623275183616691177

博士 === 國防醫學院 === 生命科學研究所 === 85 === DNA vaccines encoding a viral protein can result in the induction of anti-viral immune responses and in protective immunity in viral challenge. In this study, we shown that efficacy of a DNA vaccine can be significantly improved by simultaneous expression of murine interleukin-2 (IL-2) or granulocytes-macrophage colony-stimulating factor (GM-CSF) or by coinjection with plasmid vecotors encoding a variety of cytokines. Plamsid vectors encoding the major (S) or middle (pre-S2 plus S) envelope proteins of hepa titis B virus (HBV) were constructed and compared for their potential to induce hepatitis B surface antigen (HBsAg)-specific immune responses with a bicistronic vector separately encoding the middle envelop protein and IL-2 or with a vector encoding the middle envelope and IL-2 or GM-CSF fusion protein. Following transfection of cells in culture with these HBV plasmid vectors, we found that the encoded major protein was secreted while the middle protein and the fusion protens were retained on the cell membr ane. Despite difference in localization of the encoded antigens, plasmids encoding the major or middle proteins gave similar antibody and T-cell proliferative responses in the vaccinated animals. The use of plamsids coexpressing IL-2 or GM-CSF and the envelope protein in the fusion or nonfusion context resulted in enhanced humoral and cellular immune responses. In addition, the vaccine efficacy in terms of dosage used in immunization was increased at least 100-fold by coexpression of IL-2 or GM-CSF. We als o found that DNA vaccines coexpressing IL-2 help overcome major histocompatibility complex-linked nonresponsivness to HBsAg vaccination. During an immune, differential cytokine production by CD4+ T helper(Th) cells response plays an crucial role in regulating the nature of that response and thus determines the outcome of many infectious and autoimmune diseases. In addition, the polization of the immune response induced by a DNA vaccine into Th1 or Th2-cell type can also be altered by coexpression of cytokin es. Mice immunized with a plasmid vector encoding the major envelope protein of HBV and cytokine genes encoding IL-12 or IFN-r show a significant enhancement of IFN-r and IL-2-producing Th1 cells and an increased production of anti-HBs IgG2a antibodies, as well as a marked inhibition of IL-4-secreting Th2 cells and decreased production of IgG1 antibodies. In contrast, coinjection of the HBV DNA vaccine with a plasmid expressing IL-4 significantly enhanced the development of HBsAg-specific Th2 cells and incr eased production of IgG1 antibodies, whereas Th1 differentiation and IgG2a production were suppressed, while coinjection with plasmids encoding IL-2 or GM-CSF enhanced the development of Th1 cells, the development of Th2 cells was not significant affected and titers of both IgG1 and IgG2a anti-HBs antibodies were increased. The CTL activity induced by HBV DNA vaccination was also strongly influenced by coinjection with plasmids encoding different cytokines. Coexpression of IL-12, IFN-r, IL-2 or GM-CSF incre ased the HBsAg-specific CTL activity, whereas coexpression of IL-4 suppressed the CTL activity. Take together, these results demonstrate that the development of Th1/Th2 cells and the nature of the immune response to a DNA vaccine can be modulated by coexpression of a particular cytokine protein. To evaluate the utility of DNA-based immunization as a potential cancer treatment strategy, we employed an experimental murine tumor, CT-26, expressing the model tumor-associated Ag, HBsAg, designated CT-26/S. Immun ization with this HBV DNA vaccine attenuated tumor growth. DNA immunization alone had little impact on the growth of tumor. To enhance the function of DNA immunization for anti-tumor effect, a panel of plasmid encoded cytokines were added as adjuvants following DNA administration. Significant reduction in the tumor size was observed when mouse IL-2, GM-CSF, IFN-r or IL-12 were given after DNA coinjection; IL-12 as an adjuvant had the most profound effect. In contrast, coinjection of the HBV DNA vaccine wit h a plasmid expressing IL-4 reduced the ability of antitumor effect. The antitumor effector cells were both of CD4+ and CD8+ T cells. These findings suggest that the cytokines involved in the activation and expansion of lymphocyte populations may improve the prophylactic and therapeutic efficacy of DNA vaccine. Given the ease with which plasmid DNA can be prepared to high purity for safe use in humans with infectious diseases and cancers, coinjection of the HBV DNA vaccine with plasmids expressing cytokines may be an attractive alternative to recombinant viral vaccine.