Cell-Penetrating Peptides in infection and immunization.

Bacteria and viruses pose significant threats to human health, as drug molecules and therapeutic agents are often hindered by cell membranes and tissue barriers from reaching intracellular targets. Cell-penetrating peptides (CPPs), composed of 5-30 amino acids, function as molecular shuttles that facilitate the translocation of therapeutic agents across biological barriers. Despite their therapeutic potential, CPPs exhibit limitations, such as insufficient cell specificity, low in vivo stability, reduced delivery efficiency, and limited tolerance under serum conditions. However, intelligent design and chemical modifications can enhance their cell penetration, stability, and selectivity. These advancements could significantly improve CPP-based drug delivery strategies, facilitating both infection treatment and immunization against bacterial and viral diseases. This review provides an overview of the applications of CPPs in various infections and immune diseases, summarizing their mechanisms and the challenges encountered during their application.