Tough and waterproof microneedles overcome mucosal immunotolerance by modulating antigen release patterns.

Mucosal vaccines are considered an ideal choice for combating mucosal pathogens due to their ability to neutralize pathogens at the first line of defense. However, the development of mucosal subunit vaccines is constricted by rigorous challenges, such as low immunogenicity, poor antigen delivery efficiency, and mucosal tolerance. Here, a buccal microneedle patch incorporated with engineered nanoparticles loaded with urease B subunit (rUreB) was developed to overcome the above challenges. Specifically, an engineered nanocarrier was developed to protect the antigen and modulate its release profile. Then, the nanoparticles were enriched to form microneedle tips with superior mechanical and waterproof properties, allowing effective penetration of the buccal mucosa and resistance to salivary washout. Besides, the microneedles demonstrated an S-curve antigen release pattern which was crucial for the recruitment of antigen presenting cells (APCs) and the downregulation of mucosal tolerogenic DCs and Treg cells. The buccal microneedle vaccine without any immune stimulators induced potent systemic and mucosal immune responses, resulting in superior protection of mice from the oral challenge of Helicobacter pylori. These results suggested that the rationally designed buccal microneedle vaccine can effectively overcome mucosal delivery barriers and mucosal tolerance, providing a promising alternative strategy for mucosal vaccination of subunit antigens.