A Self‐Assembled RSV‐DS2 Based Nanovaccine Elicits a Strong Immune Response Against Respiratory Syncytial Virus Infection

Abstract Human respiratory syncytial virus (RSV) is a leading global cause of severe respiratory infections in infants, substantial morbidity in adults, and elevated mortality among elderly individuals. While recently, the Food and Drug Administration (FDA)‐approved subunit and mRNA‐based RSV vaccines have demonstrated clinical efficacy, next‐generation platforms capable of eliciting synergistic humoral and cellular immunity remain critical. Here, a self‐assembled nanovaccine platform incorporating either prefusion‐stabilized F protein variants (DS‐Cav1, DS2) or post‐fusion F (PF) conjugated to the PC7A polymer and co‐adsorbed with the TLR9 agonist CpG is developed. Comparative immunogenicity analyses in C57BL/6J and BALB/c mice demonstrated that the RSV F protein‐PC7A/CpG combinatorial nanovaccine platform outperformed individual adjuvant formulations (CpG‐alone or PC7A‐alone) in eliciting neutralizing antibody titers against both the RSV A and B subtypes. BALB/c models further revealed comprehensive cellular immune activation, characterized by significant expansion of antigen‐specific TNF‐α ⁺ CD4 ⁺ /CD8 ⁺ T cells, IL‐4 ⁺ T helper subsets, and Granzyme B ⁺ cytotoxic T lymphocytes. During the live RSV challenge, the vaccinated groups, especially the DS2‐PC7A/CpG nanovaccine cohort, exhibited a significant reduction in pulmonary viral loads and attenuated airway inflammation. These findings highlight the DS2‐PC7A/CpG nanovaccine as a potent dual‐adjuvanted candidate and immune synergy to advance clinical RSV vaccine development.