Alphavirus Replicon DNA Vectors Expressing Ebola GP and VP40 Antigens Induce Humoral and Cellular Immune Responses in Mice.

Shoufeng Ren,Wenquan Liu,Qimei Wei,Shaohui Liang,Feng Tan,Liya Cai,Cuicui Xing,Xuejing Yang,Jianmei W Leavenworth

doi:10.3389/fmicb.2017.02662

Abstract

Ebola virus (EBOV) causes severe hemorrhagic fevers in humans, and no approved therapeutics or vaccine is currently available. Glycoprotein (GP) is the major protective antigen of EBOV, and can generate virus-like particles (VLPs) by co-expression with matrix protein (VP40). In this study, we constructed a recombinant Alphavirus Semliki Forest virus (SFV) replicon vector DREP to express EBOV GP and matrix viral protein (VP40). EBOV VLPs were successfully generated and achieved budding from 293 cells after co-transfection with DREP-based GP and VP40 vectors (DREP-GP+DREP-VP40). Vaccination of BALB/c mice with DREP-GP, DREP-VP40, or DREP-GP+DREP-VP40 vectors, followed by immediate electroporation resulted in a mixed IgG subclass production, which recognized EBOV GP and/or VP40 proteins. This vaccination regimen also led to the generation of both Th1 and Th2 cellular immune responses in mice. Notably, vaccination with DREP-GP and DREP-VP40, which produces both GP and VP40 antigens, induced a significantly higher level of anti-GP IgG2a antibody and increased IFN-γ secreting CD8+ T-cell responses relative to vaccination with DREP-GP or DREP-VP40 vector alone. Our study indicates that co-expression of GP and VP40 antigens based on the SFV replicon vector generates EBOV VLPs in vitro, and vaccination with recombinant DREP vectors containing GP and VP40 antigens induces Ebola antigen-specific humoral and cellular immune responses in mice. This novel approach provides a simple and efficient vaccine platform for Ebola disease prevention.

Highlights

Ebola virus (EBOV), an enveloped RNA virus, belongs to the genus Ebolavirus in the Filoviridae family (Holmes et al, 2016)
These results indicated that GP and VP40. EBOV matrix protein (VP40) could be efficiently expressed in mammalian cells using the Semliki Forest virus (SFV)-based replicon DNAlaunched replicons (DREP) vector
Neither GP- nor VP40specific IFNγ secreting CD8+ T-cell responses were generated in the DREP-eGFP control group. These results demonstrated that co-vaccination with DREP-based GP and VP40 antigens elicited EBOV-specific CD8+ T lymphocyte responses, which were superior to vaccination with DREP-GP or DREP-VP40 alone

Summary

Introduction

Ebola virus (EBOV), an enveloped RNA virus, belongs to the genus Ebolavirus in the Filoviridae family (Holmes et al, 2016). There are five species of EBOV, including Zaire virus (ZEBOV), Sudan virus (SEBOV), Taï Forest virus (TEBOV), Bundibugyo virus (BEBOV), and Reston virus (REBOV). The former four EBOV are known to cause severe hemorrhagic fever in humans, with case fatality rates of up to 90% (Feldmann et al, 2003; Holmes et al, 2016). Induction of anti-GP antibodies by the recombinant EBOV vaccine is necessary to provide protection against EBOV infection in nonhuman primates (Blaney et al, 2013; Pyankov et al, 2015). GP protein (alone or in combination with VP40) is chosen as the primary immunogen in the majority of vaccine candidates against EBOV infection, such as attenuated recombinant EBOV vaccines (Papaneri et al, 2012), DNA vaccines (Martin et al, 2006), and virus-like particles (VLPs) vaccines (Warfield et al, 2003, 2007; Sun et al, 2009)

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Conclusion