Delivery of the TLR ligand poly(I:C) to liver cells in vitro and in vivo by calcium phosphate nanoparticles leads to a pronounced immunostimulation.

The selective activation of the immune system is a concurrent problem in the treatment of persistent diseases like viral infections (e.g. hepatitis). For the delivery of the toll-like receptor ligand poly(I:C), an immunostimulatory action was discovered earlier by hydrodynamic injection. However, this technique is not clinically transferable to human patients. A modular system where the immunoactive toll-like-receptor ligand 3 (TLR-3) poly(I:C) was incorporated into calcium phosphate nanoparticles was developed. The nanoparticles had a hydrodynamic diameter of 275nm and a zeta potential of +20mV, measured by dynamic light scattering. The diameter of the solid core was 120nm by scanning electron microscopy. In vitro, the nanoparticle uptake was investigated after 1 and 24h of incubation of THP-1 cells (macrophages) with nanoparticles by fluorescence microscopy. After intravenous injection into BALB/c and C57BL/6J mice, respectively, the in vivo uptake was especially prominent in lung and liver, 1 and 3h after the injection. Pronounced immunostimulatory effects of the nanoparticles were found in vitro with primary liver cells, i.e. Kupffer cells (KC) and liver sinusoidal endothelial cells (LSEC) from wild-type C57BL/6J mice. Thus, they represent a suitable alternative to hydrodynamic injection treatments for future vaccination concepts. STATEMENT OF SIGNIFICANCE: The selective activation of the immune system is a concurrent problem in the treatment of persistent diseases like viral infections (e.g. hepatitis). For the delivery of the toll-like receptor ligand poly(I:C), an immunostimulatory action has been discovered earlier by hydrodynamic injection. However, this technique is not clinically transferable to human patients. We have developed a modular system where poly(I:C) was incorporated into calcium phosphate nanoparticles. The uptake into relevant liver cells was studied both in vitro and in vivo. After intravenous injection into mice, the in vivo uptake was especially prominent in lung and liver, 1 and 3h after the injection. The corresponding strong immune reaction proves their high potential to turn up the immune system, e.g. against viral infections, without adverse side reactions.