Engineered bacteriophage nanoassemblies in vivo stabilize DC-T cell immune synapse for high-performance influenza vaccination.

T cell activation by dendritic cells (DCs) requires the formation of a stable immune synapse (IS). The objective of this study was to develop a vaccination approach by targetedly regulating DC-T cell synaptic interactions in vivo. We constructed bacteriophage nanoassemblies to deliver antigen-encoding sequences into DC cytoplasm and enhance DC-T cell IS stability in vivo, thereby boosting vaccine potency. Specifically, influenza hemagglutinin stem gene was inserted into the genome and DC-targeting peptide was fused to the sidewall of bacteriophages. Then, bacteriophages acted as surfactants to cover hydrophobic particles, within which sodium/proton pump inhibitors were encapsulated to regulate intercellular adhesion molecule 1 (ICAM-1) membrane positioning for stabilizing IS. The size-controlled nanoassemblies inhibited internalization of ICAM-1 via activating the NF-κB, PI3K-AKT, and RhoA-ROCK signaling pathways. Immunization with the nanoassemblies triggered robust T cell and antibody responses against influenza virus, leading to complete protection and long-term immune memory in infected mice. In sum, our results highlight the feasibility for improving vaccine protective potency via targeted enhancement of the IS stability between DCs and T cells in vivo. Given their flexibility and commonality, the bacteriophage nanoassemblies can be readily tailored for the development of various vaccine formulations against other pathogens.