Induction of Protective Immunity against Toxoplasma gondii in Mice by Nucleoside Triphosphate Hydrolase-II (NTPase-II) Self-amplifying RNA Vaccine Encapsulated in Lipid Nanoparticle (LNP).

Fangjun Luo,Yue Hu,Zhongkui Xiong,Feng Tan,Yan Wang,Shuxian Liu,Xin Hu,Lina Zheng

doi:10.3389/fmicb.2017.00605

Abstract

RNA-based vaccine represents an irresistible and safe immunization strategy with decreasing theoretical risks of genomic integration and malignant cell transformation. To our knowledge, however, there is no report about development of RNA vaccine against Toxoplasma gondii infection. We have previously demonstrated that the recombinant T. gondii nucleoside triphosphate hydrolase-II (NTPase-II) protein is able to provide protective Th1 cell-mediated immunity against T. gondii. Herein, we evaluated the immunogenic potential of a self-amplifying RNA vaccine-encoding T. gondii NTPase-II gene, RREP-NTPase-II, delivered by a synthetic lipid nanoparticle (LNP). Immunization of mice with naked RREP-NTPase-II induced a strong cellular and humoral immune response with high-IgG antibody titers and IFN-γ production. The immunized mice displayed significantly prolonged survival time and reduction in brain parasite load (46.4%) compared with control group. Furthermore, mice vaccinated with RREP-NTPase-II-encapsulated LNP displayed significantly enhanced protection against acute infection as well as chronic infection with PRU cyst, which shows 62.1% reduction in brain cyst burden in comparison to control group. These results suggest that the combination of self-amplifying RNA and LNP ion would be beneficial to the development of a safe and long-acting vaccine against toxoplasmosis.

Highlights

Toxoplasma gondii, the pathogen of toxoplasmosis, is an obligate intracellular parasitic protozoan, which has a wide range of hosts including humans and warm-blooded animals (Cenci-Goga et al, 2011)
We found that RREP-NTPaseII elicited both humoral and cellular immune responses that could be enhanced by lipid nanoparticle (LNP) encapsulation, indicating that the combination of self-amplifying RNA vaccine and LNP delivery system is a promising approach with an improved safety and immunogenicity profile
The fluorescence was observed in the cells transfected with self-amplifying RNA, whereas no fluorescent signal was observed in the negative control (Figure 1B), demonstrating that nucleoside triphosphate hydrolase (NTPase)-II protein could be expressed in mammalian cells

Summary

Introduction

Toxoplasma gondii, the pathogen of toxoplasmosis, is an obligate intracellular parasitic protozoan, which has a wide range of hosts including humans and warm-blooded animals (Cenci-Goga et al, 2011). It is unlikely to be applied to humans because of limitations of reduced efficacy as well as biosafety concerns (Zhang et al, 2013) To surmount this defect, current development trials of vaccines against T. gondii infection have been focused mainly on the subunit, recombinant, and nucleic acid vaccines (Jongert et al, 2009; Zhang et al, 2013). Current development trials of vaccines against T. gondii infection have been focused mainly on the subunit, recombinant, and nucleic acid vaccines (Jongert et al, 2009; Zhang et al, 2013) Among these different approaches, development of nucleic acid-based vaccine is a promising approach due to less expense, easiness to handle, as well as its ability to induce both humoral and cellular immune responses with low dose (Tang et al, 1992). The non-amplifying mRNA vaccines have been utilized in experimental animals for elicitation of humoral and cellular immune responses against tumor (Pascolo, 2008; Fotin-Mleczek et al, 2011), allergy (Weiss et al, 2012), and infectious disease (Lorenzi et al, 2010)

Methods

Results

Conclusion