An Orthogonal Nanoadjuvant-Based RSV Subunit Vaccine Unlocks Potent Immunity through a High-Entropy-like Immunostimulatory Effect.

Respiratory syncytial virus (RSV) is one of the primary contributors to lower respiratory tract infections, especially in infants, children, and the elderly. The quest for a clinically acceptable and potent RSV vaccine constitutes a long-standing hurdle in clinical practice. Herein, we propose an orthogonal nanoadjuvant-based nanovaccine platform that addresses the long-standing challenge of insufficient cellular immunity in RSV F subunit vaccination. The vaccine is constructed based on Mn/Al-layered double hydroxide (Mn/Al-LDH) nanosheet functionalized with RSV F antigen and poly-CpG motifs. In this system, Al acts as a humoral immunity adjuvant promoting potent antibody responses, while Mn and CpG can enhance cellular immunity through activation of the cGAS-STING pathway and Toll-like receptor (TLR), respectively. The orchestrated activation of multiple immune pathways synergistically produces a "high-entropy" immunostimulatory effect, which facilitates the recruitment and subsequent activation of potent CD4+ and CD8+ T cells, thus leading to more rapid antigen-specific immune activation and fostering the establishment of robust long-term T cell memory. Furthermore, an expanded CD134-positive subset within central memory T cells (TCM) is observed, demonstrating that the immune system is primed for robust clonal proliferation and differentiation into effector and memory cell lineages. This immunological setup ensures that any subsequent encounter with the specific antigen will trigger an immediate and vigorous secondary response. In murine challenge models, the nanovaccine outperforms traditional aluminum (Al)-based vaccines by significantly reducing viral load and mitigating lung pathology. This study establishes a new paradigm for developing efficacious RSV vaccines, and the underlying strategy is broadly applicable to vaccine development against other intractable pathogens.