Nanobody-mediated SPECT/CT imaging reveals the spatiotemporal expression of programmed death-ligand 1 in response to a CD8<sup>+</sup> T cell and iNKT cell activating mRNA vaccine
Thomas Ertveldt, Sofie Meulewaeter, Yannick De Vlaeminck, Oscar Olarte, Katrijn Broos, Serge Van Calenbergh, Stephanie Bourgeois, Joke Deprez, Yves Heremans, Cleo Goyvaerts, Willem Staels, Stefaan C. De Smedt, Heleen Dewitte, Nick Devoogdt, Marleen Keyaerts, Rein Verbeke, Kurt Barbé, Ine Lentacker, Karine Breckpot
Abstract
Tc-labeled anti-PD-L1 nanobodies allows to document the dynamic nature of PD-L1 expression upon vaccination. Galsome vaccination rapidly induced systemic upregulation of PD-L1 expression with the most pronounced upregulation in lungs and liver while flow cytometry analysis showed upregulation of PD-L1 in the tumor microenvironment. This study shows that imaging using nanobodies may be useful for monitoring vaccine-mediated PD-L1 modulation in patients and could provide a rationale for combination therapy. To the best of our knowledge, this is the first report that visualizes PD-L1 expression upon cancer vaccination.