Mucosal-Penetrating Nanovaccine Enhances Mucosal and Systemic Immunity against Respiratory Syncytial Virus Infection.

Eliciting mucosal immunity is crucial for protecting against respiratory pathogen infections. However, the intricate structure of mucosal tissues and their immune tolerance environment pose great challenges for the development of mucosal vaccines. To avoid being expelled by the ciliary clearance system, mucosal adhesion materials, such as chitosan, have been applied to efficiently deliver antigens to the immune system. However, the antigen showed poor mucus penetration due to chitosan's strong adhesion to mucin. Herein, we applied hyaluronic acid (HA)-coated nanoparticulate vaccine, named NHCF, containing Pre-F protein of respiratory syncytial virus (RSV) formulated with chitosan. Compared with the vaccine without HA coating (NC), NHC by intranasal administration (I.N.) to mice exhibited an enhanced penetration of the mucus layer, which was confirmed by a respiratory organoid chip. Moreover, when agonists were cofabricated with Pre-F in NHC, compared to CpG or cholera toxin B (CTB), the vaccines with 2,3-cGAMP (NHCF-GAMP) can overcome the mucosal immune tolerance microenvironment and produce the highest titer of IgA in mucosal and IgG in serum. Aside from the arousing humoral immunity, NHCF-GAMP can recruit the most abundant immune cells to nasal-associated lymphoid tissue from circulation. Notably, the mice that received NHCF-GAMP significantly reduced mucosal damage and viral load upon RSV challenge from mucus. Thus, this study demonstrates that a rational design delivery system of antigen and agonist can effectively enhance mucosal vaccine efficacy.