Chimeric Virus-like Particles of Universal Antigen Epitopes of Coron-avirus and Phage Q beta Coat Protein Trigger the Production of Neutralizing Antibodies

Background: Virus-like Particles (VLPs) are non-genetic multimeric nanoparticles syn-thesized through in vitro or in vivo self-assembly of one or more viral structural proteins. Immuno-genicity and safety of VLPs make them ideal candidates for vaccine development and efficient nanocarriers for foreign antigens or adjuvants to activate the immune system. Aims: The present study aimed to design and synthesize a chimeric VLP vaccine of the phage Qbe-ta (QI3) coat protein presenting the universal epitope of the coronavirus. Methods: The RNA phage QI3 coat protein was designed and synthesized, denoted as Qbeta. The CoV epitope, a universal epitope of coronavirus, was inserted into the C-terminal of Qbeta using genetic recombination, designated as Qbeta-CoV. The N-terminal of Qbeta-CoV was successively inserted into the TEV restriction site using mCherry red fluorescent label and modified affinity puri-fied histidine label 6xHE, which was denoted as HE-Qbeta-CoV. Isopropyl I3-D-1-thiogalactopy-ranoside (IPTG) assessment revealed the expression of Qbeta, Qbeta-CoV, and HE-Qbeta-CoV in the BL21 (DE3) cells. The fusion protein was purified by salting out using ammonium sulfate and affinity chromatography. The morphology of particles was observed using electron microscopy. The female BALB/C mice were immunized intraperitoneally with the Qbeta-CoV and HE-Qbeta--CoV chimeric VLPs vaccines and their sera were collected for the detection of antibody level and antibody titer using ELISA. The serum is used for the neutralization test of the three viruses of MHV, PEDV, and PDCoV. Results: The results revealed that the fusion proteins Qbeta, Qbeta-CoV, and HE-Qbeta-CoV could all obtain successful expression. Particles with high purity were obtained after purification; the chimeric particles of Qbeta-CoV and HE-Qbeta-CoV were found to be similar to Qbeta particles in morphology and formed chimeric VLPs. In addition, two chimeric VLP vaccines induced specific antibody responses in mice and the antibodies showed certain neutralizing activity. Conclusion: The successful construction of the chimeric VLPs of the phage QI3 coat protein pre -senting the universal epitope of coronavirus provides a vaccine form with potential clinical applica-tions for the treatment of coronavirus disease.

Automated summary

The study successfully designed and synthesized a chimeric VLP vaccine of the phage QI3 coat protein presenting the universal epitope of the coronavirus. Mouse experiments confirmed specific antibody responses and neutralizing activity induced by the chimeric VLP vaccines.