Treatment of Congenital Neurotransmitter Deficiencies by Intracerebral Ventricular Injection of an Adeno-Associated Virus Serotype 9 Vector

Abstract

Dopamine and serotonin are produced by distinct groups of neurons in the brain, and gene therapies other than direct injection have not been attempted to correct congenital deficiencies in such neurotransmitters. In this study, we performed gene therapy to treat knock-in mice with dopamine and serotonin deficiencies caused by a mutation in the aromatic l-amino acid decarboxylase (AADC) gene (Ddc KI mice). Intracerebral ventricular injection of neonatal mice with an adeno-associated virus (AAV) serotype 9 (AAV9) vector expressing the human AADC gene (AAV9-hAADC) resulted in widespread AADC expression in the brain. Without treatment, 4-week-old Ddc KI mice exhibited whole-brain homogenate dopamine and serotonin levels of 25% and 15% of normal, respectively. After gene therapy, the levels rose to 100% and 40% of normal, respectively. The gene therapy improved the growth rate and survival of Ddc KI mice and normalized their hindlimb clasping and cardiovascular dysfunctions. The behavioral abnormalities of the Ddc KI mice were partially corrected, and the treated Ddc KI mice were slightly more active than normal mice. No immune reactions resulted from the treatment. Therefore, a congenital neurotransmitter deficiency can be treated safely through inducing widespread expression of the deficient gene in neonatal mice.

Antisense oligonucleotides modulate dopa decarboxylase function in aromatic l -amino acid decarboxylase deficiency

“…However, only modest improvement of motor symptoms was obtained in the treated patients (San et al., ). For gene therapy of DDC , spatial and temporal effects need to be considered; in addition, issues of safety and vector types remain as challenges when invasive AAV virus‐based gene therapy is used in human patients with AADCD or in ddc mutant mouse models (Hwu et al, ; Lee et al, ; Lee et al., ; Lee, Lee, Chen, Byrne, & Hwu, ; Samaranch et al., ). Conversely, morpholino ASOs have been demonstrated to exhibit a high degree of safety for gene therapy use in various animal model studies (Arora et al., ; Iversen, Arora, Acker, Mason, & Devi, ; Kinali et al., ) and clinical trials (Mendell et al., ; Lu, Cirak, & Partridge, ).…”

Benefits of Neuronal Preferential Systemic Gene Therapy for Neurotransmitter Deficiency

“…The AAV9 vector was constructed as previously reported. 10 Briefly, the expression cassette consisted of a cytomegalovirus immediate-early promoter followed by the first intron of the human growth hormone gene, human AADC cDNA (NM_000790), and the simian virus 40 polyadenylation signal sequence. 4 The expression cassette was then cloned into a plasmid with AAV type 2 inverted terminal repeats and then packaged into an AAV type 9 capsid (i.e., AAV9-CMVhAADC; AAV9-AADC).…”

“…For open-field analysis, the total activity and number of rears were recorded for 10 min using an automated locomotor activity analysis system (PAS-Open Field, San Diego Instruments, San Diego, CA, USA). 10 Mice were tested in the open-field analysis with or without apomorphine (1.0 mg/kg, i.p.). A forced swimming test was performed as previously described.…”

“…9 Although intracerebroventricular (ICV) injection of AAV9-CMV-hAADC (AAV9-AADC) in neonatal Ddc KI mice resulted in widespread expansion of AADC expression in the mouse brain and improvements in body weight gain, survival and behavior, the treated mice became hyperactive. 10 Moreover, the translation of brain-targeted therapy in neonatal mice to larger animals or humans remains challenging because the maturation level of the blood-brain barrier (BBB) in neonatal mice corresponds to that of the fetal stage in humans. In this A c c e p t e d m a n u s c r i p t study, we extended the treatment model of AADC deficiency to systemic treatment in young mice by employing vectors containing either a ubiquitous promoter (i.e., AAV9-AADC) or a promoter for preferential neuronal expression (i.e., yfAAV9/3-Syn-I-hAADC, AAVN-AADC).…”

Recombinant adeno-associated virus vectors in the treatment of rare diseases

“…In neonatal mice, following intracerebroventricular injection of rAAV9 encoding human ADDC, dopamine and serotonin levels rose from 25% and 15% to 100% and 40%, respectively, with improved growth rate and survival as well as partially corrected behavioral abnormalities 92 . Currently one clinical trial is exploring the use of rAAV2 encoding AADC for AADC therapy.…”