Flagellate bacteria-mediated tumour antigen delivery: A novel approach to enhance dendritic cell activation for in situ cancer vaccination.

In situ vaccination is a therapeutic approach aimed at exploiting tumour antigens available at a tumour site to induce tumour-specific adaptive immune responses. Antigens released from dying tumour cells are assumed to be taken up by activated dendritic cells and presented to T cells that seek out and destroy tumour cells. This process is significantly impeded in the immunosuppressive microenvironment of tumours. There is a growing trend in in situ vaccine strategies that utilize bacteria as natural adjuvants or as factories for cytokines, aiming to enhance the presentation of in situ antigens by antigen-presenting cells. Recently, a novel approach using flagellate bacteria-mediated antigen delivery to activate dendritic cells has been proposed. This method actively facilitates the delivery of intratumoral antigens, improving their presentation for in situ cancer vaccination. Here, we highlight how flagellate bacteria-mediated antigen delivery enhances the immune activation capabilities of in situ vaccines. Meanwhile, we provide perspectives and outlooks on these promising antigen delivery technologies.