The DNA Vaccines for the Gn and Gc Heterologous Polymer of Severe Fever with Thrombocytopenia Syndrome Virus Induce Potent Immunogenicity in Mice.

INTRODUCTION/

BACKGROUND

Severe fever with thrombocytopenia syndrome virus (SFTSV) poses a threat to global public health with a mortality rate of up to 30%. However, there is currently no commercialized SFTSV vaccine. This study focused on the construction of DNA vaccines with different structures based on the surface glycoproteins Gn and Gc to identify the immunodominant conformations.

METHODS

The DNA vaccines encoding secretory proteins including Gn or Gc monomer, heterodimer of Gn and Gc (dimer), two forms of hexamer composed of the Gn and Gc heterodimer (hexamer-1 and hexamer-2) or ferritin nanoparticles of Gn, and non-secretory proteins including Gn (Gn-TM) and Gc (Gc-TM) were constructed. Western blot confirmed the expression level and the specificity of those DNA vaccines. After vaccinating mice with those DNA vaccines, its induced humoral and cellular immunity were comprehensively evaluated.

RESULTS

The DNA vaccines were constructed successfully. The DNA vaccines of Gn and polymers including dimer, hexamer-2, and ferritin nanoparticles inducing stronger binding antibody, neutralizing antibody, and antibody-dependent cellular cytotoxicity (ADCC) activity. The neutralizing antibody induced by these constructs was also cross-recognized by other five SFTSV pseudovirus strains. However, the T cell response induced by Gc, dimer or hexamer-2 DNA vaccines were significantly higher than those in most other groups, including Gn.

CONCLUSION

The DNA vaccines encoding dimer or hexamer-2 demonstrated superior immunogenicity over other conformations, after taking the results of humoral and cellular responses into account. This study revealed the advantages of using polymer conformations in SFTSV vaccine design and provided new targets in SFTSV vaccine development.