An AAV-Based Therapy Approach for Neurological Phenotypes of X-Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a monogenic progressive neurodegenerative disorder, being simultaneously a systemic metabolic disease and demonstrating severe neurological manifestations with effects to the brain and spinal cord. The objective of the current review is to provide a detailed approach to adeno-associated virus (AAV)-based gene therapy for neurological manifestations of X-ALD. The development of a successful AAV-mediated gene therapy hinges on its ability to deliver ABCD1 cDNA effectively to the relevant organs and cell types, induce therapeutic levels of protein expression, and ultimately, restore normal very-long chain fatty acids (VLCFA) metabolic function. Thus, several key considerations should be addressed when designing AAV-based gene therapy for X-ALD, including the genetic background of the disease and requisite transgene expression levels, the biochemical function of the adrenoleukodystrophy protein (ALDP), the identification of target cells and their role in pathogenesis, the regulation of expression within the genetic construct, the route of administration, the selection of an AAV serotype with high tropism for the central and peripheral nervous systems, and the development of robust in vitro and in vivo models.