Enhancement of autophagy as a strategy for development of new DNA vaccine candidates against Japanese encephalitis

Abstract

For decades, an on-going concerted effort has been made to develop a universal DNA vaccine to combat the looming threat of a potential outbreak of the emerging Japanese encephalitis virus (JEV) infection. However, effective strategies are urgently required to counter poor immunogenicity and insufficient long-term protection. Recent reports have confirmed the critical role of autophagy in antigen presentation, long-term immune memory and immune responses against JEV. In this study, JEV prM and E protein with strong immunogenicity were fused with microtubule-associated protein 1 light chain 3 (LC3) encoding gene to construct an autophagy-mediated pJME-LC3 DNA vaccine. Researches indicated significant increase of autophagosomes or LC3 Ⅱ expression in pJME-LC3 transfected cells. Furthermore, prME-LC3 fused protein was observed co-localized with GFP-LC3 to autophagosomes, which means it was successfully targeted to autophagosomes. After immunizing with pJME-LC3, mice were detected highest proportion of CD3⁺CD8⁺ T lymphocytes, CD8⁺ effector memory T cells (TEMs) and JEV specific cytotoxic T lymphocyte (CTL) activity to eliminate JEV. pJME-LC3 also enhanced IgG2a antibody in serum and cytokines IFN-γ, IL-12 produced by splenocytes, thus skew toward Th1 type immune response by activating the JAK2/STAT1 signaling pathway and upregulating expression of transcription factor T-bet. Notably, mice immunized with pJME-LC3 showed highest survival rate and long-lasting neutralizing antibody when challenged with virulent JEV, which were consistent with augment in percentage of CD4⁺ central memory T cells (TCMs). In brief, our studies suggested that autophagy can be used as a optimization strategy to enhance JEV specific immune response and long-term immune memory. Our attempt will contribute towards future efforts to develop an efficacious JEV vaccine.

Keywords: Autophagy; DNA vaccine; Immune response; Japanese encephalitis virus; LC3; Long-term immune memory.