Recombinant Protein Antigen Immune Effect Research For Variant And Predicted Strains Of SARS-CoV-2

Objective This study analyzed the pathogenicity and mutation potential of the mutation sites of novel coronavirus,based on a large number of existing research data,combined with viral evolution and molecular dynamics and other means to predict the mutation sites of vaccine strains with potential broad-spectrum protection.We design the eukaryotic expression vector of recombinant protein for the prototype strain,mutant strain and predictive strain.We express its in CHO-K1 cells to evaluate its immunogenicity to explore if it has the potential to become a vaccine,and then compatibility of adjuvant and antigen was optimized to continuously improve the immune induction effect of antigen.In order to lay a foundation for the subsequent development of specific vaccines against various variants and the screening of candidate vaccines.Methods In this study,we combined with the virus genome sequence,the mutation sites can be predicted for their infectivity by considering both the binding affinity to ACE2 and the expression level in a weighted model.By incorporating the mutation rate and amino acid codon redundancy,a model containing all variables can predict the overall impact of base mutations on the virus in the target region,and the predicted strain is named "pre".Then,corresponding predicted mutant strains are designed by incorporating mutation sites based on Omicron BA.2 and other mutation sites such as L452R and R158G that appear in delta,and named "Decron".we construct UCOE-WuS1,UCOE-Delta-S1,UCOE-Omi-S1,UCOE-Pre-S1 and UCOE-Decron-S 1 eukaryotic expression plasmids and transfected its into CHO-K1 cells for expression.Then we used Elisa,pseudovirus neutralization test and flow cytometry to study the immunogenicity of the mutant and the predicted strain.Results The recombinant SARS-CoV-2 S1 protein of mutated strains and predicted strains were rapidly prepared using a eukaryotic expression system and proved can sustainably and effectively induce immune responses in BALB/c mice.The"Pre" strain can induce stronger cellular immunity,combination of multiple variant sites will help boost the broad-spectrum nature of the vaccine,which will help future research on the cross-protection of emerging viral strains.In addition,we explore the suitable range of adjuvant action and antigen dosage.We find that t PolyⅠ:C adjuvant,aluminum combined with PolyⅠ:C adjuvant,aluminum combined with CPG1018 adjuvant all could induce stronger humoral immunity and stronger cellular immunity.Conclusion The two predictive strains constructed in this study(UCOE-Decron-S1 and UCOE-Pre-S1)had good immunogenicity of S1 recombinant protein.In addition,the adjuvant of this study to carry out a preliminary study to explore the role of adjuvant and the appropriate range of antigen dose.These findings will contribute to future studies on the cross-protective effect of emerging virus strains and the safety and efficacy of novel adjuvants,and provide more experimental data and clues for the development of recombinant protein candidate vaccines of SARS-CoV-2 mutant strains.