Exosome engineering and molecular tools for targeted therapy of brain-infecting pathogens: delivery systems, signaling pathways, and therapeutic applications

Brain infections, caused by various pathogens (such as viruses, bacteria, fungi, or parasites), have proven challenging to treat due to limited drug diffusion through the blood-brain barrier and the presence of intracellular reservoirs. As biologically derived nanocarriers, exosomes have emerged as viable candidates for crossing physiological barriers and effectively delivering target molecules into the central nervous system. This review aims to summarize what is currently known about exosome biogenesis, cargo sorting, and immunological function in relation to infectious disease. In addition, it provides information on how different pathogens have taken advantage of exosomal pathways to increase their virulence and modulate the immune response, while also suggesting options for the therapeutic engineering of exosomes. It critically evaluates technological advances made in exosome engineering, such as CRISPR/Cas9-based cargo loading, ligand-directed surface modification of exosomes, targeted delivery of nucleic acids, and creation of stimuli-responsive release systems for exosome cargo for their potential application as precision therapies against pathogens that infect the brain. Pharmacokinetic data and biodistribution studies, along with studies examining how route of administration, inflammatory status, and receptor mediated uptake affect CNS targeting efficacy reflect that exosome engineering offers a novel platform for creating precision therapeutics against pathogens that infect the brain.