Rational Combination of Dominant and Subdominant Antigens with Nanoadjuvant Elicits Durable Immunity Against Staphylococcus aureus

Objectives: In response to the challenge that Staphylococcus aureus (S. aureus) vaccines fail to induce durable protective immunity, this study aims to develop a novel antigen-adjuvant co-design strategy. Specifically, we rationally combined the immunodominant toxin antigen LukS-PV with the immunologically subdominant adhesin antigen ClfA, co-delivered via the PLGA-PEG nanoadjuvant system, to elicit synergistic, durable, and balanced humoral and cellular immune responses. Methods: Firstly, recombinant antigens LukS-PV and ClfA were individually covalently conjugated to PLGA-PEG 25% nanoparticles (25% NPs) using EDC/NHS chemical coupling to construct a combined nanovaccine, followed by systemic safety verification in a mouse model. Subsequently, specific antibody titers were detected by ELISA, and the secretion levels of IL-4, IFN-γ, and IL-17A were measured by ELISPOT assay to comprehensively evaluate the humoral and cellular immune responses induced by the vaccine. Finally, the protective efficacy of the vaccine was assessed through acute and long-term (up to 180 days) lethal challenge experiments, thereby verifying the effectiveness of this co-design strategy based on rational antigen selection. Results: The combined vaccine group (25% NPs-rClfA + 25% NPs-rLukS-PV) not only elicited high levels of specific antibodies but, more importantly, induced robust cellular immune responses dominated by Th1 and Th17 cells. Challenge experiments confirmed that the protective efficacy of the combined vaccine was significantly superior to that of any single-antigen vaccine and provided complete protection for up to 180 days. Crucially, the same antigen combination formulated with a traditional aluminum adjuvant failed to confer this durable protection, underscoring the essential role of adjuvant synergy. Conclusions: This study demonstrates that rational combination of immunodominant and subdominant antigens with a compatible nanoadjuvant induces synergistic and durable immunity against S. aureus. This co-design strategy addresses key limitations of previous vaccines and provides a promising foundation for future clinical development.