DNA Prime-Protein Boost Targeting Conformational Non-RBD Region for Broad Cross-Neutralization

The preservation of antigen spatial conformation is crucial for inducing the high-quality neutralizing responses. Although the receptor-binding domain (RBD) antigen in SARS-CoV-2 vaccines shows satisfactory conformation preservation, it remains susceptible to the immune escape. Therefore, exploring conformational epitopes beyond the RBD region to achieve cross-neutralization becomes an attractive topic. In this study, we used a DNA prime-protein boost regimen to obtain potent humoral responses. Further analysis revealed that boosting antibody responses targeting conformational non-RBD region is crucial for enhancing cross-neutralization against the Wuhan-01, Delta and Omicron subvariants. Via analyzing the distribution of conformational epitopes, and quantifying epitope-specific binding antibodies, we verified a positive correlation between the proportion of binding antibodies against the N-terminal domain (NTD) supersite (a conformational non-RBD epitope) and SARS-CoV-2 neutralization potency. The current work highlights the importance of conformational non-RBD-specific binding antibodies in mediating viral cross-neutralization and provides a new insight in overcoming the immune escape of SARS-CoV-2 variants. ### Competing Interest Statement The authors have declared no competing interest.