Polyethyleneimine-modified Laminarin nanoparticles enhance antigen delivery to lymph nodes by inducing transient inflammatory responses at the injection site.

Functionalized nanoparticles hold great potential as vaccine adjuvants. In our previous study, we demonstrated that polyethyleneimine-modified Laminarin nanoparticles (CLam/OVA) exhibit potent adjuvant effects. However, it is still unclear how the administration of CLam/OVA affects cell mobilization, the interactions between immune cells in the body, and the transportation of draining lymph nodes. Therefore, the present study aimed to investigate how CLam/OVA enhanced and modulated vaccine-induced immune responses. Results indicate that following CLam/OVA injection, the injection site secretes IL-6, TNF-α, and IFN-γ, forming a transient, adjuvant-induced inflammatory microenvironment. Concurrently, macrophages and dendritic cells are recruited and activated at the site of injection. Subsequently, antigen-loaded dendritic cells homing to lymph nodes drive follicular helper T cells differentiation, germinal center responses, and memory B cell generation, establishing robust and durable adaptive immunity. In summary, this study not only elucidates the immune adjuvant of CLam/OVA but also provides robust support for the design of novel vaccine adjuvants.