Common cold embecovirus imprinting primes broadly neutralizing antibody responses to SARS-CoV-2 S2.

Summary

This mechanistic study shows that immune imprinting by common cold embecovirus OC43 back-boosts antibody-secreting cells to generate broadly cross-reactive, neutralizing, and protective antibodies to conserved S2 epitopes. It proposes a vaccine strategy using OC43 priming followed by SARS-CoV-2 boosting to enhance pan-coronavirus protection.

Key Findings

• Convalescent S2-targeting antibodies were largely non-neutralizing and restricted to closely related sarbecoviruses.
• First-exposure severe COVID-19 patients mounted OC43-imprinted, back-boosted ASC responses yielding broadly cross-reactive, neutralizing, and protective antibodies across up to five betacoronavirus subgenera.
• Two S2 antigenic sites were defined: a stem-helix–competitive site and a distinct apex epitope; controlled OC43 priming followed by SARS-CoV-2 boosting is proposed to improve S2 vaccine breadth.

Clinical Implications

Although preclinical, the findings support evaluating controlled OC43 priming and SARS-CoV-2 boosting to broaden protection, informing next-generation vaccine trials aiming at cross-lineage and pan-betacoronavirus coverage.

Limitations

• Observational human immunology with limited sample sizes and potential selection bias
• Vaccine priming/boosting strategy not yet validated in clinical trials

Future Directions

Test OC43 priming/SARS-CoV-2 boosting regimens in controlled trials; structural vaccinology to optimize S2 immunogen presentation at the stem-helix and apex epitopes; assess durability and breadth across variants.