Liposome induction of CD8+ T cell responses depends on CD169+ macrophages and Batf3-dependent dendritic cells and is enhanced by GM3 inclusion

Cancer vaccines aim to efficiently prime cytotoxic CD8(+) T cell responses which can be achieved by vaccine targeting to dendritic cells. CD169(+) macrophages have been shown to transfer antigen to dendritic cells and could act as an alternative target for cancer vaccines. Here, we evaluated liposomes containing the CD169/ Siglec-1 binding ligand, ganglioside GM3, and the non-binding ligand, ganglioside GM1, for their capacity to target antigens to CD169(+) macrophages and to induce immune responses. CD169(+) macrophages demonstrated specific uptake of GM3 liposomes in vitro and in vivo that was dependent on a functional CD169 receptor. Robust antigen-specific CD8(+) and CD4(+) T and B cell responses were observed upon intravenous administration of GM3 liposomes containing the model antigen ovalbumin in the presence of adjuvant. Immunization of B16-OVA tumor bearing mice with all liposomes resulted in delayed tumor growth and improved survival. The absence of CD169(+) macrophages, functional CD169 molecules, and cross-presenting Batf3-dependent dendritic cells (cDC1s) significantly impaired CD8(+) T cell responses, while B cell responses were less affected. In conclusion, we demonstrate that inclusion of GM3 in liposomes enhance immune responses and that splenic CD169(+) macrophages and cDC1s are required for induction of CD8(+) T cell immunity after liposomal vaccination.

Automated summary

In this study, liposomes containing GM3 were shown to efficiently target CD169(+) macrophages, inducing specific immune responses including antigen-specific CD8(+) and CD4(+) T cell as well as B cell responses. Administration of GM3 liposomes containing ovalbumin resulted in delayed tumor growth and improved survival in B16-OVA tumor bearing mice. The study also highlighted the essential role of CD169(+) macrophages and cDC1s in inducing CD8(+) T cell immunity through liposomal vaccination.