Liposomal simvastatin potentiates intranasal H1N1 influenza subunit vaccine via increasing transcytosis of antigen and submucosal dendritic cell recruitment

Intranasal vaccines specifically eliciting mucosal immunity in the upper respiratory tract have shown advantages in protecting against respiratory virus invasion. Yet, no clinically licensed intranasal adjuvant remains a major hurdle for the development of intranasal vaccines with low immunogenic antigens like subunit vaccines. Here, we show that liposomes loading simvastatin (Lipo-SV) serve as potent mucosal adjuvants for the intranasal liposomal subunit vaccine encapsulating the hemagglutinin 1 (HA1) glycoprotein of A/PR/8/34 (PR8) H1N1 influenza (Lipo-HA1), providing robust protection against the lethal PR8 H1N1 infection. Compared to cholera toxin subunit B (CTB), the only mucosal adjuvant used in humans, the Lipo-SV substantiate intranasal Lipo-HA1 vaccines to elicit robust systemic and local mucosal immune responses. The underlying mechanism of the adjuvanticity of Lipo-SV involves the increased transcytosis of antigens by inhibiting the geranylgeranylation of RAB5 and RAB7B GTPases in nasal epithelial cells. Moreover, Lipo-SV enhance the submucosal recruitment of dendritic cell for antigen uptake via the Toll-like receptor 4-dependent pathway. Unlike CTB, intranasal Lipo-SV do not induce inflammation in the lung or the inflammatory cytokines in the central nervous system. Our results present a paradigm of design of mucosal adjuvant to target the mucosal epithelial cells in addition to the antigen-presenting cells.