Development of an adeno-associated virus-based gene therapy for the treatment of amyotrophic lateral sclerosis: A focus on the gene delivery to the central nervous system

Abstract

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disorder that is invariably fatal typically within 2-5 years of diagnosis. Although 10% of ALS cases are classified as familial (fALS), the remaining 90% of patients are considered sporadic (sALS) as they have no family history of the disease. Despite the elusive onset of the disease, common molecular mechanisms have been identified among the cells of the CNS in patients with varying classifications of onset. Gene therapy targeting these dysregulated pathways holds promise for long-term treatment, or even a cure. However, effective delivery to the CNS remains a key challenge, particularly due to the protective feature of the BBB which stringently controls entry to the CNS, protecting from invading pathogens, toxins, and viruses. While some variants of AAV have demonstrated the ability to cross the BBB and deliver genetic cargo to cells of the CNS when injected intravenously in higher-order mammals, the efficiency and specificity of CNS entry is very low.

This thesis had two primary aims. The first aim was to develop an enhanced gene delivery method to the CNS using AAV vectors. To accomplish this, the thesis explored various approaches, including i) searching for naturally occurring AAV variants in human brain tissue that exhibit superior capsid efficiency and specificity for the CNS; ii) employing AAV engineering to select for novel AAV capsid(s) with these desired attributes; and iii) comparing the efficiency of existing AAV vectors at transducing the CNS when injected directly via CSF administration. The second aim of this thesis was to identify and investigate a novel gene therapy target for the treatment of ALS, with a focus on a therapeutic target that could benefit both fALS and sALS patients. Overall, this thesis aimed to provide an improved method for CNS gene delivery for the advancement of all gene therapy for neurological disorders, whilst also contributing to ALS treatment research.