English: Figure 1. Modifying the surfaces of viral vectors for different purposes. Shielding viral vectors with polymers and lipidic vesicles typically results in the reduced immunogenicity and increased persistence of the vectors in the blood stream. Biomaterials and polymers represent a physical barrier that not only prevents neutralization from antibodies but also impairs the uptake of the vector by macrophages and antigen presenting cells (APC). Polymers can also be linked with peptides and ligands that target a specific receptor, changing the vector tropism and allowing efficient re-targeting.