Construction and immunogenicity of recombinant rabies virus expressing S gene of SARS-CoV-2

ABSTRACT

[Background] The coronavirus disease 2019（COVID-19） pandemic has lasted for nearly three years in the globe, which has not only caused serious harm to humans but also affected companion animals. The COVID-19 vaccines for human have been used globally, while those for animals are rarely reported. [Objective] To develop a bivalent vaccine against both severe acute respiratory syndrome coronavirus 2（SARS-CoV-2） and rabies virus（RABV） for animal use. [Methods] We cloned the S and S1 genes of SARS-CoV-2 into the region between G and L genes of the attenuated RABV vaccine strain rHEP-Flury to construct the recombinant plasmids pHEP-nCOV-S and pHEP-nCOV-S1, respectively.The two plasmids were respectively co-transfected into BHK-21 cells with the helper plasmids and finally the recombinant viruses rHEP-nCOV-S and rHEP-nCOV-S1 were rescued. The recombinant viruses were confirmed by RT-PCR and direct fluorescent antibody staining against RABV N protein.Western blotting was employed to detect the expression of S and S1 proteins in the cells infected with the recombinant viruses. The growth curves, pathogenicity, and immunogenicity of recombinant viruses were confirmed in NA cells and mice. [Results] The rescued recombinant viruses rHEP-nCOV-S and rHEP-nCOV-S1 respectively carrying the S and S1 genes of SARS-CoV-2 were confirmed by direct fluorescent antibody assay based on the green fluorescence from the supernatants 7 days post infection.rHEP-nCOV-S1 rather than rHEP-nCOV-S showed stronger proliferation and diffusion abilities than the parental virus rHEP-Flury in NA cells. The specific bands at 72 kDa and 144 kDa in the Western blotting confirmed the efficient expression of S and S1 in the recombinant viruses, respectively. The mice vaccinated with the recombinant viruses did not show significant changes in the body weight compared with those vaccinated with rHEP-Flury, and the recombinant viruses induced the production of neutralizing antibody against RABV in mice. [Conclusion] The production of the recombinant RABV carrying the S/S1 gene of SARS-CoV-2 provides a foundation for the development of the bivalent vaccine against both SARS-CoV-2 and rabies virus for animal use.