Spike‑only targeting bottleneck and blind spot of conserved epitopes First‑generation COVID‑19 mRNA vaccines targeted only the viral Spike (S) protein as a single antigen, inducing precise neutralizing antibodies. However, continuous SARS‑CoV‑2 evolution has accumulated extensive amino‑acid substitutions across the S protein, especially the receptor‑binding domain (RBD), eroding the binding affinity of vaccine‑elicited antibodies and creating a technical bottleneck of humoral immune escape. Structurally conserved regions outside S—namely the Membrane (M) and Nucleocapsid (N) proteins—contain immunodominant epitopes that, when fused as multiple modules to awaken a T‑cell immune backbone, represent a high‑resolution antigen design that has long been a blind spot in pandemic defense.

CoV2‑BMEPu multi‑target architecture: soluble trimeric secreted LNP engineering In May, this study launched the next‑generation multi‑epitope mRNA vaccine platform CoV2‑BMEPu, designed by retro‑tracking immunological profiles from convalescent cohorts to overcome antigenic distance of variants. The team precisely bound not only the broadly neutralizing RBD fragment of S but also conserved core segments of M and N at the sequence level. Crucially, the expressed antigen was engineered into a soluble trimeric structure that is secreted rather than retained intracellularly, then packaged into a lipid nanoparticle (LNP) backbone. This engineering triggers rapid innate immune activation by stimulating pattern‑recognition receptors on human macrophages.

Polyfunctional CD8⁺ T‑cell and T‑follicular helper (Tfh) responses conferring complete protection against lethal infection Preclinical kinetic analysis in C57BL/6 mice showed that the mRNA‑BMEPu group maintained high cross‑neutralizing antibody titers against the original Wuhan strain and highly evolved Omicron sub‑variants. At the cellular level, polyfunctional CD8⁺ T cells co‑producing IFN‑γ and TNF‑α and robust Tfh differentiation supporting B‑cell maturation were sustained, preserving long‑term memory immunity. In lethal challenge studies using K18‑hACE2 transgenic mice, 100 % complete protection was demonstrated, with full suppression of viral replication kinetics in lung tissue and mitigation of inflammatory cytokine storms.

Establishing a post‑spike universal vaccine specification and reducing variant response lead time The immunogenicity and structural synthetic biology dataset generated by this work provides a unique impact on global nucleic‑acid vaccine R&D and next‑generation LNP pipelines. It shifts vaccine design standards from simple S‑protein sequence updates to a “structured‑and‑unstructured protein‑linked multi‑epitope modular backbone.” The soluble trimeric secretion design serves as a filtration engine that pre‑calculates effective concentration thresholds for gRNA/mRNA sequence optimization upon variant emergence. By preemptively blocking the chronic neutralization‑loss risk observed in preclinical stages through a dual humoral‑cellular immune backbone, this asset will serve as a master reference for establishing regulatory guidelines for next‑generation universal COVID‑19 vaccine platforms.