Aromatic L-amino Acid Decarboxylase Gene Research Articles

REVEAL-CP: Selective Screening of Pediatric Patients for Aromatic L-Amino Acid Decarboxylase Deficiency with a Guthrie Card and In Silico Structural Modeling of One Index Case.

Background: The main objective of this prospective, multicenter study (REVEAL-CP) was to test children with cerebral palsy-like signs and symptoms for raised 3-O-methyldopa (3-OMD) blood levels, a biomarker for aromatic L-amino acid decarboxylase deficiency (AADCd). A secondary objective was to characterize the molecular basis for the defective aromatic L-amino acid decarboxylase (AADC) gene product. Methods: Patients were identified in pediatric secondary and tertiary care hospitals through database searches and personal communication. 3-OMD concentrations from Guthrie card tests were determined using liquid chromatography/mass spectrometry. If 3-OMD was raised, cerebrospinal fluid analysis and dopa decarboxylase (DDC) gene sequencing were performed. An in-silico mutagenesis analysis was carried out to model altered AADC enzymes. Results: In total, 166 patients were enrolled in this study. The median age was 8 years. Sixty-six patients (39.8%) had a diagnosis of cerebral palsy, with the most common type being "mixed" (n = 42; 25.3%). One patient (0.6%), an 11-month-old boy from Italy, was diagnosed with AADCd caused by a homozygous, pathogenic DDC variant (c.749C>T; p.Ser250Phe). Three-dimensional modeling of the Ser250Phe AADC enzyme variant revealed its destabilization. Conclusions: A Guthrie card test for 3-OMD is a recognized screening technique for AADCd. If universal newborn screening for this metabolic disease is not available, children with signs and symptoms of a movement disorder should be investigated for AADCd.

Analysis of gene therapy encoding aromatic L-amino acid decarboxylase (AADC) enzyme in the treatment of Parkinson’s disease

Parkinson's Disease (PD), a progressive neurodegenerative disorder characterized by dopaminergic neuron degeneration, leads to motor and non-motor symptoms that significantly impair quality of life. Conventional treatments, such as levodopa, provide symptom relief but are associated with long-term complications and do not halt disease progression. This review systematically evaluates the efficacy and safety of gene therapy targeting the aromatic L-amino acid decarboxylase (AADC) enzyme in treating PD and AADC deficiency, focusing on sustained dopamine production and motor function improvement. A systematic literature review was conducted using databases like PubMed, Scopus, and Embase, covering studies published over the past 32 years. Out of 52 articles identified, 25 met inclusion criteria, providing data on motor outcomes, dopamine production, and safety profiles. Findings suggest that AADC gene therapy may offer a durable therapeutic approach, reducing reliance on conventional dopamine replacement therapies and mitigating related complications. This review highlights gene therapy's potential in clinical practice, emphasizing a shift towards targeted treatment strategies for dopamine-deficient neurodegenerative disorders. Further research should address long-term efficacy and safety across diverse patient groups. Limitations include potential selection bias and language restrictions.

P.037 Refractory status dystonicus and hypotension after cardiac arrest in a child with AADC deficiency post gene therapy: a case report

Background: Aromatic l-amino acid decarboxylase (AADC) deficiency is a metabolic disorder that causes deficient serotonin, dopamine, and catecholamine synthesis. How children respond to neurological insult post intracranial gene therapy remains underreported. We present a 10 year old girl with profound neurological injury after a brief in-hospital cardiac arrest, secondary to viral infection-induced respiratory failure, 4 years after gene therapy. Methods: Patient’s chart review included brain imaging, clinical notes, laboratory results, and treatment. Results: MRI showed symmetric abnormalities in the basal ganglia, thalami, cortex, and cerebellar hemispheres. CSF analysis showed homovanillic acid 27 nmol/L (reference range 167-563) and 5-hydroxyindoleacetic acid 7 nmol/L (reference range 67-189). She developed generalized dystonia and oculogyric crises which were not seen since before gene therapy. There was poor catecholamine production causing refractory hypotension. She required a one-month stay in ICU for hypotension and status dystonicus. Dystonia was controlled with high doses of 6 agents. Conclusions: We describe a patient with AADC deficiency post gene therapy who experienced disproportionately severe neurological injury and decreased AADC activity after hypoxic neurological insult. There may be unique considerations of dopaminergic neuron integrity, AADC gene promoter sensitivity, and cerebrovascular autoregulation in children with AADC deficiency post gene therapy.

Author Response: Safety of AADC Gene Therapy for Moderately Advanced Parkinson Disease: Three-Year Outcomes From the PD-1101 Trial.

We appreciate the comment by Kang et al. on our research.1 While we acknowledge findings of toxicity in a mouse model of elevated cellular dopamine due to overexpression of the dopamine transporter,2 such toxicity has not been observed in rodent or primate models of Parkinson disease (PD) in which the aromatic L-amino acid decarboxylase (AADC) gene therapy was tested.3,4 Moreover, in our observations of these participants 3 years after AADC therapy,1 we did not see evidence of significant clinical worsening, which would be expected if the AADC gene therapy was causing injury to medium spiny neurons.

Reader Response: Safety of AADC Gene Therapy for Moderately Advanced Parkinson Disease: Three-Year Outcomes From the PD-1101 Trial.

In a recent gene therapy trial, delivery of aromatic l-amino acid decarboxylase (AADC) to striatal cells reduced the levodopa dose required and improved global impression measures, with no apparent serious adverse effects.1 This study builds on previous research that gene therapy to enhance dopamine production in specific target areas has the potential to enhance the motor benefits of levodopa.2

Long-term efficacy and safety of eladocagene exuparvovec in patients with AADC deficiency

Aromatic L-amino acid decarboxylase deficiency results in decreased neurotransmitter levels and severe motor dysfunction. Twenty-six patients without head control received bilateral intraputaminal infusions of a recombinant adeno-associated virus type 2 vector containing the human aromatic L-amino acid decarboxylase gene (eladocagene exuparvovec) and have completed 1-year evaluations. Rapid improvements in motor and cognitive function occurred within 12months after gene therapy and were sustained during follow-up for>5 years. An increase in dopamine production was demonstrated by positron emission tomography and neurotransmitter analysis. Patient symptoms (mood, sweating, temperature, and oculogyric crises), patient growth, and patient caretaker quality of life improved. Although improvements were observed in all treated participants, younger age was associated with greater improvement. There were no treatment-associated brain injuries, and most adverse events were related to underlying disease. Post-surgery complications such as cerebrospinal fluid leakage were managed with standard of care. Most patients experienced mild to moderate dyskinesia that resolved in a few months. These observations suggest that eladocagene exuparvovec treatment for aromatic L-amino acid decarboxylase deficiency provides durable and meaningful benefits with a favorable safety profile.

Safety of AADC Gene Therapy for Moderately Advanced Parkinson Disease: Three-Year Outcomes From the PD-1101 Trial.

Background and ObjectivesTo report final, 36-month safety and clinical outcomes from the PD-1101 trial of NBIb-1817 (VY-AADC01) in participants with moderately advanced Parkinson disease (PD) and motor fluctuations.MethodsPD-1101 was a phase 1b, open-label, dose escalation trial of VY-AADC01, an experimental AAV2 gene therapy encoding the human aromatic l-amino acid decarboxylase (AADC) enzyme. VY-AADC01 was delivered via bilateral, intraoperative MRI-guided putaminal infusions to 3 cohorts (n = 5 participants per cohort): cohort 1, ≤7.5 × 1011 vector genomes (vg); cohort 2, ≤1.5 × 1012 vg; cohort 3, ≤4.7 × 1012 vg.ResultsNo serious adverse events (SAEs) attributed to VY-AADC01 were reported. All 4 non-vector–related SAEs (atrial fibrillation and pulmonary embolism in 1 participant and 2 events of small bowel obstruction in another participant) resolved. Requirements for PD medications were reduced by 21%–30% in the 2 highest dose cohorts at 36 months. Standard measures of motor function (PD diary, Unified Parkinson's Disease Rating Scale III “off”-medication and “on”-medication scores), global impressions of improvement (Clinical Global Impression of Improvement, Patient Global Impression of Improvement), and quality of life (39-item Parkinson's Disease Questionnaire) were stable or improved compared with baseline at 12, 24, and 36 months following VY-AADC01 administration across cohorts.DiscussionsVY-AADC01 and the surgical administration procedure were well-tolerated and resulted in stable or improved motor function and quality of life across cohorts, as well as reduced PD medication requirements in cohorts 2 and 3 over 3 years.Trial Registration InformationNCT01973543.Classification of EvidenceThis study provides Class IV evidence that, in patients with moderately advanced PD and motor fluctuations, putaminal infusion of VY-AADC01 is well tolerated and may improve motor function.

Use of a novel ball-joint guide array for magnetic resonance imaging-guided cannula placement and convective delivery: technical note.

The objective of this study was to assess the feasibility, accuracy, effectiveness, and safety of an MRI-compatible frameless stereotactic ball-joint guide array (BJGA) as a platform for cannula placement and convection-enhanced delivery (CED). The authors analyzed the clinical and imaging data from consecutive patients with aromatic l-amino acid decarboxylase (AADC) deficiency who underwent infusion of adeno-associated virus (AAV) containing the AADC gene (AAV2-AADC). Eleven patients (7 females, 4 males) underwent bilateral MRI-guided BJGA cannula placement and CED of AAV2-AADC (22 brainstem infusions). The mean age at infusion was 10.5 ± 5.2 years (range 4-19 years). MRI allowed for accurate real-time planning, confirmed precise cannula placement after single-pass placement, and permitted on-the-fly adjustment. Overall, the mean bilateral depth to the target was 137.0 ± 5.2 mm (range 124.0-145.5 mm). The mean bilateral depth error was 0.9 ± 0.7 mm (range 0-2.2 mm), and the bilateral radial error was 0.9 ± 0.6 mm (range 0.1-2.3 mm). The bilateral absolute tip error was 1.4 ± 0.8 mm (range 0.4-3.0 mm). Target depth and absolute tip error were not correlated (Pearson product-moment correlation coefficient, r = 0.01). Use of the BJGA is feasible, accurate, effective, and safe for cannula placement, infusion MRI monitoring, and cannula adjustment during CED. The low-profile universal applicability of the BJGA streamlines and facilitates MRI-guided CED.

Anesthetic Care of Children With Gene Therapy for the Treatment of Aromatic L-Amino Acid Decarboxylase (AADC) Deficiency

AADC deficiency is a rare autosomal recessive disease that may lead to movement disorder and/or autonomic dysfunction. The prognosis of AADC deficiency patients is poor, and most die in childhood. Gene therapy is the only method currently available to help alleviate related symptoms. Gene therapy involves the injection of adeno-associated viral (AV) vector into the basal ganglia of patients, helping transfer the AADC gene and leading to improved AADC production and higher numbers of neurotransmitters in the brain. Moreover, as patients are unable to produce catecholamine, they may also suffer from a disorder affecting the regulatory control of the autonomic nervous system, resulting in hypoglycemia, which often causes imbalances in thermoregulation and hemodynamic and functional adjustments during surgery. Furthermore, the use of analgesics and inhalational anesthetics increase the risks of hypotension and bradycardia. Thus, in addition to assessing cardiac and respiratory system functions, it is important to evaluate the patient's airway before administering anesthesia, as structural anomalies or other situations may be present that lead to difficulties in tracheal intubation. Various airway tools, anesthesia equipment, and alternative plans should thus be prepared to protect the airway and maintain vital signs. All of the abovementioned issues increase the risks of AADC deficiency patients undergoing general anesthesia. The development of gene transfection for genetic diseases is a future trend. This paper identifies possible problems and related responses in perioperative patient care during gene therapy. The authors hope that these experiences provide references for the administration of AADC and similar gene therapies in the future.

Efficacy and safety of AAV2 gene therapy in children with aromatic L-amino acid decarboxylase deficiency: an open-label, phase 1/2 trial

Aromatic l-amino acid decarboxylase (AADC) deficiency is an inherited disease that causes depletion of neurotransmitters and severe motor dysfunction in infants and children. We previously reported compassionate use of an adeno-associated virus (AAV) vector containing the human AADC gene (AAV2-hAADC) in four children with AADC deficiency (aged 4-6 years). In this study, we aimed to establish the efficacy and safety of this treatment. We did an open-label, phase 1/2 trial at the National Taiwan University Hospital (Taipei, Taiwan). We included patients who had a definitive diagnosis and clinical symptoms of AADC deficiency (hypotonia, dystonia, and oculogyric crisis), who were older than 24 months or had skull bones suitable for stereotactic surgery, and who had an anti-AAV2 antibody titre lower than 1·0 optical density. All patients received bilateral intraputaminal injections of AAV2-hAADC (1·81 × 1011 vg in total) through stereotactic brain surgery. Primary efficacy outcomes were an increase in the Peabody Developmental Motor Scales (second edition; PDMS-2) score of greater than 10 points and an increase in homovanillic acid (HVA) or 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the cerebrospinal fluid 12 months after gene therapy. We assessed patients at baseline and at 3, 6, 9, and 12 months after gene therapy, and every 6 months thereafter for one further year; all patients who received the treatment were included in the analysis. We assessed for surgical complications (cerebrospinal fluid leakage and intracerebral haemorrhage) at days 3-7 after AAV2 gene therapy, and we assessed adverse events during the follow-up evaluations for 12 months. This study is registered with ClinicalTrials.gov, number NCT01395641. Ten patients (median age 2·71 years, IQR 2·46-6·35) were enrolled from Oct 1, 2014, to Dec 2, 2015. All patients tolerated the surgeries and vector injections. One patient died from influenza B encephalitis during an endemic outbreak 10 months after treatment; therefore, 9 months of data were included in the analyses for this patient. All patients met the primary efficacy endpoint: 12 months after gene therapy, PDMS-2 scores were increased by a median of 62 points (IQR 39-93; p=0·005) and HVA concentrations by a median of 25 nmol/L (IQR 11-48; p=0·012); however, there was no significant change in 5-HIAA concentrations (median difference 0, IQR 0-5; p=0·20). In total, 101 adverse events were reported, with the most common being pyrexia (16 [16%] of 101 events) and orofacial dyskinesia (ten [10%]). 12 serious adverse events occurred in six patients, including one death (treatment-unrelated encephalitis due to influenza B infection), one life-threatening pyrexia, and ten events that led to hospital admission. Transient post-gene therapy dyskinesia occurred in all patients but was resolved with risperidone. Of 31 treatment-related adverse events, only one (patient 1) was severe in intensity, and none led to hospital admission or death. Our findings suggest that intraputaminal injection of AAV2-hAADC is well tolerated and might improve motor development in children with AADC deficiency. AADC Research Fund at National Taiwan University Hospital and the National Research Programme for Biopharmaceuticals.

Parkinson’s disease

Adeno-associated virus (AAV) vectors are derived from the non-pathogenic parvovirus. The genome of AAV vector does not integrate into the host chromosome and persists as an episome in the nucleus of host cells. Although their small packaging capacity (about 3 kb) can limit the use of AAV vectors, most therapeutic genes fall within this size range. Use of multiple vectors and simultaneous expression of the respective genes into the target cell can overcome this drawback. AAV vectors transduce neurons efficiently and can express therapeutic genes or miRNA for prolonged periods without causing any toxic effects. To date, AAV vectors have been used in more than 183 clinical trials conducted for various diseases such as retinal degeneration, hemophilia, and Parkinson disease, and have shown no adverse effects. The expression of dopamine-synthesizing enzymes persisted 15 years after gene transfer in a primate model of Parkinson’s disease. In clinical studies, intraputaminal delivery of AAV vectors that contain aromatic l-amino acid decarboxylase (AADC) gene show the beneficial effects in patients with either advanced Parkinson’s disease or AADC deficiency. Some AAV vectors can cross the blood or cerebrospinal fluid-brain barrier and transduce neurons of the central nervous system after systemic injection. Use of these AAV vectors in proof-of-principle investigations of animal models for various metabolic and neurologic diseases such as lysosomal storage disease, Alzheimer’s disease, spinocerebellar ataxia, and motor neuron disease has yielded favorable results. Various advantages of AAV vector-based gene therapy compared to ordinary drugs necessitate the development of more manufacturing systems that can optimize large-scale production of GMP-grade AAV vectors.

A pathogenic S250F missense mutation results in a mouse model of mild aromatic l-amino acid decarboxylase (AADC) deficiency.

Homozygous mutations in the aromatic l-amino acid decarboxylase (AADC) gene result in a severe depletion of its namesake protein, triggering a debilitating and often fatal form of infantile Parkinsonism known as AADC deficiency. AADC deficient patients fail to produce normal levels of the monoamine neurotransmitters dopamine and serotonin, and suffer a multi-systemic disorder characterized by movement abnormalities, developmental delay and autonomic dysfunction; an absolute loss of dopamine is generally considered incompatible with life. There is no optimal treatment for AADC deficiency and few truly good models in which to investigate disease mechanisms or develop and refine therapeutic strategies. In this study, we introduced a relatively frequently reported but mildly pathogenic S250F missense mutation into the murine Aadc gene. We show that mutants homozygous for the mutation are viable and express a stable but minimally active form of the AADC protein. Although the low enzymatic activity of the protein resulted in only modestly reduced concentrations of brain dopamine, serotonin levels were markedly diminished, and this perturbed behavior as well as autonomic function in mutant mice. Still, we found no evidence of morphologic abnormalities of the dopaminergic cells in mutant brains. The striatum as well as substantia nigra appeared normal and no loss of dopamine expressing cells in the latter was detected. We conclude that even minute levels of active AADC are sufficient to allow for substantial amounts of dopamine to be produced in model mice harboring the S250F mutation. Such mutants represent a novel, mild model of human AADC deficiency.

Aromatic amino acid decarboxylase is involved in volatile phenylacetaldehyde production in loquat (Eriobotrya japonica) flowers.

Post anthesis, loquat flowers emit volatile benzenoids, including phenylacetaldehyde, phenylethyl alcohol, and 2-phenethyl benzoate. Previous studies have shown that pyridoxal phosphate-dependent aromatic L-amino acid decarboxylase (AADC) produces phenylacetaldehyde from L-phenylalanine. Here, two AADC genes (EjAADC1 and EjAADC2) were isolated from loquat (Eriobotrya japonica) flowers. The EjAADC1 and EjAADC2 proteins showed approximately 72% and 55% identity, respectively, to a rose AADC homolog that has phenylacetaldehyde synthase activity. Transcript analyses indicated that EjAADC1 was specifically expressed in petals, with the highest level of expression in fully opened flowers; the petals showed high levels of volatile benzenoids, including phenylacetaldehyde. In contrast, EjAADC2 was expressed at a lower level than EjAADC1 in all tested tissues, including leaves and developing flowers. Functional characterization of a recombinant EjAADC1 protein expressed in Escherichia coli showed that it catalyzes the formation of phenylacetaldehyde from L-phenylalanine in a pyridoxal phosphate-dependent manner. Our results suggest that EjAADC1 is mainly responsible for the biosynthesis of volatile benzenoids in loquat flowers.

C-11. An Update on Gene Therapy for the Treatment of Aromatic L-Amino Acid Decarboxylase (AADC) Deficiency

Aromatic L-amino acid decarboxylase (AADC) is an enzyme responsible for the final step of the synthesis of neurotransmitters dopamine and serotonin. AADC deficiency is a rare genetic disorder causing motor and autonomic dysfunction and early death in children. Taiwanese carry a high prevalence of AADC deficiency due to a founder mutation (IVS6+4A>T) in the AADC gene. A gene therapy with recombinant adeno-associated virus (AAV) serotype 2 CMV promoter-driven human AADC (AAV2-hAADC) was conducted in children with AADC deficiency since 2010. Clinical grade vector was manufactured. Two target points were determined in each putamen and a total of 1.7×1011 vg vector was injected. Eight patients have been treated at a mean age of 4.9 years (2-8 years), and the mean follow up period was 3.8 years (3-4.5 years). All patients, except one, had homozygous IVS6+4A>T mutations. Before gene therapy, these patients didn't have head control, and could not sit or stand, and they all had regular and severe oculogyric crisis (OGC) attacks. The stereotaxic surgeries were performed smoothly and there was no intracerebral bleeding. At the most recently follow-up visits after gene therapy, one patient was learning walking, two stood with support, one sat without assist, and three had better head control. The severity of OGC decreased and emotion stabilized in all patients.[18F]fluoro-dopa positron emission tomography (PET) signal intensity over putamen increased and cerebrospinal fluid neurotransmitter levels rose in all treated patients. Post gene therapy transient (orofacial) dyskinesia was the main adverse event of the treatment, and one patient experienced a hypovolemic shock due to dyskinesia and he remained bed-ridden. There is no virus-associated side effect, and currently no patient reveals a loss of treatment effect.

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

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.

Aromatic L-Amino acid decarboxylase deficiency: A new case from Turkey with a novel mutation

Aromatic L-amino acid decarboxylase (AADC), a vitamin B6-requiring enzyme that converts L-dopa to dopamine and 5-hydroxytryptophan to serotonin. Deficiency of this enzyme results in developmental delay, muscular hypotonia, dystonia, involuntary movements, autonomic dysfunction, and oculogyric crises. We now report a 2-year-old Turkish boy with AADC deficiency confirmed by greatly reduced AADC activity in the plasma and by genetic studies. Mutation analysis revealed a homozygous mutation c.208C > T (p. His70Tyr) in exon 3 of the AADC gene which has not been described to date.

Regulation of the dopaminergic system in a murine model of aromatic l-amino acid decarboxylase deficiency

Aromatic l-amino acid decarboxylase (AADC) is responsible for the syntheses of dopamine and serotonin. Children with AADC deficiency exhibit compromised development, particularly with regard to their motor functions. Currently, no animal model of AADC deficiency exists. We inserted an AADC gene mutation (IVS6+4A>T) and a neomycin-resistance gene into intron 6 of the mouse AADC (Ddc) gene. In the brains of homozygous knock-in (KI) mice (DdcIVS6/IVS6), AADC mRNA lacked exon 6, and AADC activity was <0.3% of that in wild-type mice. Half of the KI mice were born alive but grew poorly and exhibited severe dyskinesia and hindlimb clasping after birth. Two-thirds of the live-born KI mice survived the weaning period, with subsequent improvements in their growth and motor functions; however, these mice still displayed cardiovascular dysfunction and behavioral problems due to serotonin deficiencies. The brain dopamine levels in the KI mice increased from 9.39% of the levels in wild-type mice at 2weeks of age to 37.86% of the levels in wild-type mice at 8weeks of age. Adult KI mice also exhibited an exaggerated response to apomorphine and an elevation of striatal c-Fos expression, suggesting post-synaptic adaptations. Therefore, we generated an AADC deficient mouse model, in which compensatory regulation allowed the mice to survive to adulthood. This mouse model will be useful both for developing gene therapies for AADC deficiency and for designing treatments for diseases associated with neurotransmitter deficiency.

Qualitative Imaging of Adeno-Associated Virus Serotype 2–Human Aromatic L-Amino Acid Decarboxylase Gene Therapy in a Phase I Study for the Treatment of Parkinson Disease

Putaminal convection-enhanced delivery (CED) of an adeno-associated virus serotype 2 (AAV2) vector, containing the human aromatic L-amino acid decarboxylase (hAADC) gene for the treatment of Parkinson disease (PD), has completed a phase I clinical trial. To retrospectively analyze magnetic resonance imaging (MRI) and positron emission tomography (PET) data from the phase I trial, correlate those data with similar nonhuman primate (NHP) data, and present how such information may improve future PD gene therapy trials in preparation for the initiation of the phase II trial. Ten patients with PD had been treated with bilateral MRI-guided putaminal infusions of AAV2-hAADC. MRI and PET scans were obtained at baseline (before vector administration) and at various intervals after treatment. Three normal adult NHPs received similar infusions into the thalamus. Imaging studies for both groups are presented, as well as hAADC immunohistochemistry for the NHPs. Early post-CED MRI confirmed the stereotactic targeting accuracy and revealed T2 hyperintensity around the distal cannula tracts, best seen within 4 hours of surgery. Coregistration of post-CED MRI and PET scans revealed increased PET uptake at the sites of T2 hyperintensity. Similar T2 hyperintensities in NHP MRI correlated with hAADC immunohistochemistry. Our analysis confirms the correct targeting of the CED cannula tracts within the target human putamen. Coregistration of MRI and PET confirms colocalization of T2 hyperintensities and increased PET uptake around the distal cannula tracts. Because PET uptake closely correlates with hAADC transgene expression and NHP data confirm this relationship between T2 hyperintensity and hAADC immunohistochemistry, we believe that T2-weighted MRI allows visualization of a significant part of the distribution volume of the hAADC gene therapy. Recommendations for future protocols based on these data are presented.

An Unusual Case of Feeding Intolerance in a 7 Month Old Female

Purpose: Background: Aromatic L-amino acid decarboxylase deficiency (AADC) is an inborn error in neurotransmitter metabolism caused by mutations in the dopa decarboxylase (aromatic L-amino acid decarboxylase) gene, which leads to combined serotonin and catecholamine deficiency. Symptoms include severe developmental delay, hypotonia, muscle stiffness, athetosis, lethargy, feeding intolerance, sleep disturbances, oculogyric crises, extreme irritability, pain, muscle spasms, and uncontrolled movements. Patient: A 7 month old Caucasian female with a history of hypotonia and developmental motor delay presented with excessive irritability and feeding intolerance. Clinical Course: She was well until 3-4 months of age, when she became inconsolable, had non-bilious, non-bloody emesis, and irritability with feeds. Symptoms worsened over the last 3 months. She had decreased activity, poor eye tracking, and hypotonia. Initial workup showed normal gastric emptying scan, MBS revealing frank aspiration, and pH probe showed copious reflux, so a Nissen fundoplication with gastric feeding tube was placed. Lorazepam and phenobarbital did not have a perceived effect. Additional workup included an EEG, head CT scan, head MRI, karyotype, serum lactate level, serum ammonia level, and plasma amino acids which were all within normal limits except for a low cysteine level. Urine organic acids showed minimal dicarboxylic acids and acetylcarnitine profile showed a mildly elevated C4OH due to diet or a ketotic state. Magnetic resonance spectroscopy (MRS) was notable for nonspecific lactate spikes. Because of suspicion of a possible mitochondrial or neurotransmitter disorder, a lumbar puncture was performed. Neurotransmitter analysis and plasma enzymology confirmed the diagnosis of AADC. Pyridoxal-5-phosphate (coenzyme B6) and ropinirole (a dopamine agonist) were added, in addition to hyoscyamine, pantoprazole, and sucralfate. Two months after diagnosis, she has been tolerating feeds with less irritability. Conclusion: Children with feeding disorder, developmental delay and hypotonia should have a work-up for inborn errors of metabolism. Initial laboratory workup should include CBC, electrolytes, LFTs, urine organic acids, blood amino acids and acylcarnitine profile, total and free carnitine levels, as well as an MRI and MRS.

GENE THERAPY FOR PARKINSON'S DISEASE: STRATEGIES FOR THE LOCAL PRODUCTION OF DOPAMINE

The cardinal motor symptoms of Parkinson's disease (PD) are associated with the profound depletion of dopamine in the striatum. The replacement of dopamine is the most straightforward strategy to improve motor performance in PD. Researchers have been developing gene therapy aimed at local production of dopamine via the introduction of dopamine-synthesizing enzyme genes into the putamen. Two phase I clinical studies have used recombinant adeno-associated virus (AAV) vectors to transfer the aromatic L-amino acid decarboxylase (AADC) gene into the putamen to restore efficient conversion of orally administered L-3,4-dihydroxyphenylalanine (L-dopa). The initial results of these studies have not only confirmed the safety of AAV vectors, but have also demonstrated the alleviation of motor symptoms associated with PD. Interestingly motor performance in the off medication state was improved after gene therapy, suggesting long-term modulation of dopaminergic signals in the striatal neurons was induced by gene transfer. Gene delivery of tyrosine hydroxylase (TH) and guanosine triphosphate cyclohydrolase I (GCH) in addition to AADC may help to avoid motor fluctuations associated with intermittent intake of L-dopa by continuously supplying dopamine in the putamen. A clinical study of such triple gene transfer is presently underway using equine infectious anemia virus (EIAV) vector.