E. coli ssDNA/LyoVec™ is a Toll-like receptor 9 (TLR9) ligand. It comprises E. coli ssDNA an ultrapure, endotoxin-free preparation of bacterial single‑stranded DNA (ssDNA) which is complexed with the cationic lipid-based transfection reagent LyoVec™. This allows for a better internalization of the immunostimulatory DNA to the acidic endosomal compartment where TLR9 is expressed.TLR9 specifically recognizes CpG DNA that is unmethylated and single-stranded (ss). Upon recognition, it initiates a signaling cascade leading to the activation of the transcription factors NF-κB, AP-1, and interferon regulatory factor 7 (IRF7) with the subsequent production of pro‑inflammatory cytokines. Methylation of the cytosine within the CpG motif strongly reduces the affinity of TLR9 [1, 2]. In addition, double‑stranded (ds) CpG DNA is a much weaker stimulator of TLR9 compared to its ss counterpart [1]. Unlike mammalian DNA, bacterial DNA is rich in unme