Rational design of an optimized ferritin nanoparticle vaccine targeting both SARS-CoV-2 and MERS-CoV.

BACKGROUND

Coronaviruses including SARS-CoV-2 and MERS-CoV remain threats to global health. Ferritin nanoparticle-based vaccines are promising platforms for coronaviral multivalent antigen display. However, their development is often constrained by limited stability and homogeneity, which hinders scale-up manufacturing and long-term storage.

RESULTS

Here, we employed artificial intelligence (AI)-guided structural modeling and optimization to introduce disulfide bonds into Helicobacter pylori ferritin (HPF). Cryo-EM at 2.2 Å confirmed the formation of inter-subunit disulfide bonds in the most promising variant HPF (I69C), resulting in a more homogeneous nanoparticle with enhanced thermal and pH stability, as well as improved solubility in physiological conditions. We utilized the ST003/SC003 molecular glue system to covalently conjugate receptor-binding domains (RBDs) of both SARS-CoV-2 and MERS-CoV, either as a mixture of individual RBD-HPF (I69C) particles or as a dimeric RBD displayed on a single HPF (I69C). Both bivalent nanoparticle vaccines elicited significantly higher titers of RBD-specific antibodies and neutralizing antibodies compared to monomeric and dimeric vaccines. Vaccination also increased frequencies of antigen-specific B cells and polyfunctional CD4+ and CD8+ T cells. No vaccine-related systemic abnormalities were observed. In both hACE2 and hDPP4 transgenic mice, two doses of bivalent nanoparticle vaccines provided protection against authentic SARS-CoV-2 and MERS-CoV challenges.

CONCLUSIONS

Our study demonstrated that rationally engineered HPF (I69C) produced highly stable and efficiently functionalized nanoparticle vaccines capable of eliciting potent humoral and cellular immune responses against both SARS-CoV-2 and MERS-CoV infection, thereby supporting the further development of bivalent nanoparticle vaccine platforms.