Neprilysin gene transfer: A promising therapeutic approach for Alzheimer's disease

Alzheimer's disease (AD) is characterized by widespread neurodegeneration throughout the association cortex and limbic system, deposition of amyloid-β (Aβ) in the neuropil and around blood vessels, and formation of neurofibrillary tangles. Aβ accumulation is considered the major pathological change in AD progression. In recent years, several therapeutic strategies for treating AD have focused on reducing the Aβ burden in the brain. Among these approaches, the expression of Aβ-degrading enzymes in the brain has been effective but, so far, impractical for treating patients. Neprilysin (NEP), the most prominent of the Aβ-degrading enzymes in vivo, has been successfully delivered intracranially by viral vectors and is a promising therapeutic approach for reducing Aβ accumulation and treating AD. However, some challenges are associated with the use of viral and nonviral vectors, including secondary toxicity, activation of the immune response, and low efficiency. Therefore, safe and efficient NEP delivery systems that could avoid the viral problems with minor injury and high transfection efficiency are required to deliver AD medical applications. This Mini-Review summarizes NEP gene transfer technologies that use viral and nonviral vectors and discusses the rationale and benefits of these delivery systems for AD treatment trials, providing a reference for basic and clinical studies on AD.