P8: Targeted induction of T-cell activation through optimized aptamer-antigen conjugates 

Aptamers are valuable diagnostic and therapeutic reagents, but also of value for biomarker discovery. The Mayer group identified aptamers, among them aptamer D#7, binding to murine bone marrow-derived dendritic cells (BM-DCs). These aptamers are taken up by BM-DC through endocytosis and enable the targeted delivery of cargo molecules. In this regard, the induction of immune responses using aptamer-antigen conjugates were demonstrated in vitro and in vivo.

However, less is known on the impact of the linkers and on optimization of the aptamer itself. Thus, the aim of the proposed project is to optimize D#7’s performance and to evaluate the impact of the linker‘s nature on uptake and cellular fate of the aptamer-antigen conjugates. To achieve this, a series of different linker molecules will be synthesized, e.g., extended and shortened variants, flexible and rigid linkers, cathepsin-cleavable linkers, and combined with different bioconjugate coupling chemistries, e.g., maleimide (used in previous experiments), N-hydroxysuccinimide (NHS) and click chemistry for D#7 conjugation.

Likewise, D#7 will be optimized by SAR studies, i.e. determination of the minimal binding motif and identification of D#7 variants with increased affinity and uptake properties. The D#7 variants and conjugates will be examined by flow cytometry, confocal fluorescence microscopy, colocalization studies and for their potential to activate T-cells (CD4+ and CD8+). Collaborations are planned with P1 (application of PROTACs), P5 (investigation of activities on immune cells) and P9 (drug-aptamer conjugates).