Achieving dendritic cell subset-specific targeting in vivo by site-directed conjugation of targeting antibodies and nanobodies to nanocarriers
FICHTER M. 1, JUNG C. 3, SIMON J. 3, KUHN G. 2, BRÜCKNER M. 3, SCHUNKE J. 2, GRABBE S. 2, LANDFESTER K. 3, MAILÄNDER V. 1
1 University Medical Center of the Johannes Gutenberg University / Max Planck Institute for Polymer Research, Mainz, Germany; 2 University Medical Center of the Johannes Gutenberg University, Mainz, Germany; 3 Max Planck Institute for Polymer Research, Mainz, Germany
The major challenge of nanocarrier-based anti-cancer vaccination approaches is their targeted delivery of antigens and immunostimulatory agents to cells of interest, such as specific subtypes of dendritic cells (DCs), in order to induce robust antigen-specific anti-tumor responses. An undirected cell and body distribution of nanocarriers can lead to unwanted delivery to other immune cell types like macrophages reducing the vaccine efficacy. An often-used approach to overcome this issue is the surface functionalization of nanocarriers with targeting moieties, such as antibodies and nanobodies, mediating cell type-specific interaction. Numerous studies could successfully prove the targeting efficiency of antibody-conjugated carrier systems in vitro, however, most of them failed in vivo when targeting DCs that is partly due to cells of the reticuloendothelial system unspecifically clearing nanocarriers from the blood stream via Fc receptor ligation.
Therefore, this study shows a surface functionalization strategy to site-specifically attach antibodies and nanobodies in an orientated direction onto the nanocarrier surface. Different DC-targeting antibodies were conjugated to the nanocarrier surface at their Fc domains and DC-specific nanobodies were coupled via maleimide/thiol chemistry. Anti-mouse CD11c antibody-conjugated nanocarriers specifically accumulated in the targeted organ (spleen) over time. Additionally, antibodies against CD11c and CLEC9A proved to specifically direct nanocarriers to the targeted DC subtype, conventional DCs type 1. CD11c-specific nanobodies led to an even higher uptake of nanocarriers in plasmacytoid DCs and conventional DCs type 1 in vivo.
In conclusion, site-directed conjugation of antibodies and nanobodies to nanocarriers is essential in order to avoid unspecific uptake by non-target cells while achieving specific targeting of DC subsets. These functionalization techniques pave the way for the development of functionalized nanocarriers for DC-based vaccination approaches in the field of cancer immunotherapy.