Signal peptide-mediated endoplasmic reticulum targeting enhances antigen expression and secretion to improve mRNA vaccine efficacy.

The expression and secretion levels of antigenic proteins are critical determinants of mRNA vaccine efficacy. Signal peptides, which direct protein translocation into the endoplasmic reticulum (ER), have the potential to significantly enhance protein expression and immunogenicity, highlighting their value as engineering tools for mRNA vaccine design. This study adopts the SARS-CoV-2 RBD as a model antigen to screen a panel of signal peptides derived from common secretory proteins. The signal peptides from C3, IL-12, and IL-20 are identified as candidates capable of significantly promoting antigen expression and secretion. Fluorescence confocal microscopy reveals that these signal peptides enhance the targeting of mRNA to the ER at the subcellular level. In vivo experiments demonstrate that mRNA vaccines incorporating these engineered signal peptides induce stronger humoral and cellular immune responses. This study confirms that signal peptide replacement can enhance antigen expression, offering a potential strategy for improving the efficacy of mRNA vaccines.