Adenoassociated Virus Serotype 9-Mediated Gene Therapy for X-Linked Adrenoleukodystrophy

Abstract

X-linked adrenoleukodystrophy (X-ALD) is a devastating neurological disorder caused by mutations in the ABCD1 gene that encodes a peroxisomal ATP-binding cassette transporter (ABCD1) responsible for transport of CoA-activated very long-chain fatty acids (VLCFA) into the peroxisome for degradation. We used recombinant adenoassociated virus serotype 9 (rAAV9) vector for delivery of the human ABCD1 gene (ABCD1) to mouse central nervous system (CNS). In vitro, efficient delivery of ABCD1 gene was achieved in primary mixed brain glial cells from Abcd1-/- mice as well as X-ALD patient fibroblasts. Importantly, human ABCD1 localized to the peroxisome, and AAV-ABCD1 transduction showed a dose-dependent effect in reducing VLCFA. In vivo, AAV9-ABCD1 was delivered to Abcd1-/- mouse CNS by either stereotactic intracerebroventricular (ICV) or intravenous (IV) injections. Astrocytes, microglia and neurons were the major target cell types following ICV injection, while IV injection also delivered to microvascular endothelial cells and oligodendrocytes. IV injection also yielded high transduction of the adrenal gland. Importantly, IV injection of AAV9-ABCD1 reduced VLCFA in mouse brain and spinal cord. We conclude that AAV9-mediated ABCD1 gene transfer is able to reach target cells in the nervous system and adrenal gland as well as reduce VLCFA in culture and a mouse model of X-ALD.

Microglial dysfunction as a key pathological change in adrenomyeloneuropathy

“…Neither human nor mouse AMN spinal cord displays cell death despite accumulation of LPC C26:0 42. For some time, it has been known that excess VLCFA (40 µM and above) affects membrane function and causes toxicity to adrenocortical cells, oligodendrocytes, astrocytes, and neurons 43, 44.…”

“…For some time, it has been known that excess VLCFA (40 µM and above) affects membrane function and causes toxicity to adrenocortical cells, oligodendrocytes, astrocytes, and neurons 43, 44. For example, excess free VLCFA induces depolarization of mitochondria and deregulation of the intracellular calcium homeostasis,42 and in the brain, this can cause activation and apoptosis of microglia 4. However, more relevant than these supraphysiological doses are the lower doses that we used, which in isolation do not cause cell death.…”

Oxidative stress, mitochondrial and proteostasis malfunction in adrenoleukodystrophy: A paradigm for axonal degeneration

“…This alternative treatment has the same indications as bone marrow transplantation, meaning that it can be applied only to a small subset of patients with few to no symptoms [29]. A novel gene therapy strategy uses adenoassociated virus serotype 9 to express human ABCD1, which has yielded promising results in a mouse model of X-ALD [30]. However, a recent report suggests that allogeneic bone marrow transplant in cALD does arrest inflammatory progression and death, but does not prevent the adult AMN phenotype from developing AMN in adulthood [31].…”

“…Both Abcd1 -and Abcd1 -/Abcd2 -/-mice are bona fide models of mild, late-onset axonopathy exhibited by AMN patients. These models are instrumental in dissecting pathomechanisms of AMN [49][50][51][52][53] and importantly, in pinpointing and evaluating tailored therapies [30,[33][34][35][36]54].…”

Extra-adrenal induction of <i>Cyp21a1</i> ameliorates systemic steroid metabolism in a mouse model of congenital adrenal hyperplasia

“…Thus, AAV vectors are good candidates as tools for Cyp21a1/CYP21A2 induction in extra-adrenal tissues. Moreover, AAV vectors may suffice to deliver Cyp21a1/CYP21A2 to adrenal glands, because Gong et al successfully transferred ABCD1 gene into adrenal glands of X-linked adrenoleukodystrophy model mice by intravenous injection of an AAV9 vector [18]. Thus, intravenous administration of AAV9 vectors containing Cyp21a1/CYP21A2 may be a promising therapeutic option for 21-OHD.…”