Micronanoparticled risedronate exhibits potent vaccine adjuvant effects [scRNA-Seq]

Nanoparticles and microparticles are widely used as vaccine adjuvants to enhance the immune response and improve the stability of antigens. While aluminum salt is one of the most common adjuvants approved for human use, its immunostimulatory capacity is suboptimal. In this study, we modified risedronate, an immunostimulant and anti‐osteoporotic drug, to create the zinc salt particle-based risedronate (Zn-RS), also termed particulate risedronate. Compared to soluble risedronate, the Zn-RS adjuvant demonstrated increased recruitment of innate cells, enhanced antigen uptake locally, and a similar antigen depot effect as aluminum salt. Furthermore, the Zn-RS adjuvant directly and quickly stimulated immune cells, accelerated the formulation of germinal centers in the lymph nodes, and facilitated the rapid production of antibodies. Importantly, the Zn-RS adjuvant exhibited superior performance in both young and aged mice, effectively protecting against respiratory diseases such as SARS-CoV-2 infection. Consequently, particulate risedronate showed great potential as a universal vaccine adjuvant, particularly beneficial for vaccines targeting the susceptible elderly.