Dongdong Li,1 Lijun Bian,1 Lili Cui,2 Jingying Zhou,1 Gaotian Li,1 Xiaoyan Zhao,1 Liao Xing,1 Jiaxing Cui,1 Bo Sun,1 Chunlai Jiang,1,3,4 Wei Kong,1,3,4 Yong Zhang,1,3,4 Yan Chen1,3,4 

1National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, People’s Republic of China; 2Beijing Institute of Drug Metabolism, Beijing, People’s Republic of China; 3Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun, People’s Republic of China; 4NMPA Key Laboratory of Humanized Animal Models for Evaluation of Vaccines and Cell Therapy Products, Jilin University, Changchun, People’s Republic of China

Correspondence: Yan Chen; Yong Zhang, National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, 130012, People’s Republic of China, Tel +86-431-85167751, Fax +86-431-85167674, Email chen_yan0417@126.com; zhypharm@jlu.edu.cn

Purpose: Heterologous immunization using different vaccine platforms has been demonstrated as an efficient strategy to enhance antigen-specific immune responses. In this study, we performed a head-to-head comparison of both humoral and cellular immune response induced by different prime-boost immunization regimens of mRNA vaccine and adjuvanted protein subunit vaccine against varicella-zoster virus (VZV) in middle-aged mice, aiming to get a better understanding of the influence of vaccination schedule on immune response.
Methods: VZV glycoprotein (gE) mRNA was synthesized and encapsulated into SM-102-based lipid nanoparticles (LNPs). VZV-primed middle-aged C57BL/6 mice were then subjected to homologous and heterologous prime-boost immunization strategies using VZV gE mRNA vaccine (RNA-gE) and protein subunit vaccine (PS-gE). The antigen-specific antibodies were evaluated using enzyme-linked immunosorbent assay (ELISA) analysis. Additionally, cell-mediated immunity (CMI) was detected using ELISPOT assay and flow cytometry. Besides, in vivo safety profiles were also evaluated and compared.
Results: The mRNA-loaded lipid nanoparticles had a hydrodynamic diameter of approximately 130 nm and a polydispersity index of 0.156. Total IgG antibody levels exhibited no significant differences among different immunization strategies. However, mice received 2×RNA-gE or RNA-gE>PS-gE showed a lower IgG1/IgG2c ratio than those received 2×PS-gE and PS-gE> RNA-gE. The CMI response induced by 2×RNA-gE or RNA-gE>PS-gE was significantly stronger than that induced by 2×PS-gE and PS-gE> RNA-gE. The safety evaluation indicated that both mRNA vaccine and protein vaccine induced a transient body weight loss in mice. Furthermore, the protein vaccine produced a notable inflammatory response at the injection sites, while the mRNA vaccine showed no observable inflammation.
Conclusion: The heterologous prime-boost strategy has demonstrated that an mRNA-primed immunization regimen can induce a better cell-mediated immune response than a protein subunit-primed regimen in middle-aged mice. These findings provide valuable insights into the design and optimization of VZV vaccines with the potentials to broaden varicella vaccination strategies in the future.

Keywords: varicella-zoster Virus, mRNA vaccine, glycoprotein E, lipid nanoparticles, heterologous prime-boost, cell-mediated immunity