Characterizing and testing the efficacy of AAV-mediated gene therapy in a sheep model of CLN1 disease.

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Project Summary/Abstract: CLN1 disease or Infantile Neuronal Ceroid Lipofuscinosis (INCL or Infantile Batten disease) is one of the earliest onset and most rapidly progressing forms of neuronal ceroid lipofuscinosis (NCL or Batten disease). CLN1 disease is caused by deficiency in the lysosomal enzyme palmitoyl protein thioesterase-1 (PPT1). This deficiency has a devastating and rapidly progressing effect upon affected children that starts within the first year of life, and because there is no effective therapy available CLN1 disease is always fatal. We have been able to dramatically improve therapeutic outcomes in PPT1-deficient mice by targeting adeno-associated viral (AAV)-mediated gene therapy to the central nervous system (CNS) regions that are most affected, including the spinal cord. However, unlike other forms of NCL, such therapeutic effects are limited to the CNS regions that are transduced. As such, successfully translating gene therapy for CLN1 disease into the clinic will be a significant challenge in the much larger and more complex brain of a child. To overcome this obstacle, we shall use a novel CRISPR/Cas9 generated CLN1 R151X sheep model to refine our therapeutic strategy, assessing the delivery, dosing, safety and efficacy of gene therapy in a larger species that is ideally suited for translating these advances. We recently published that these CLN1 R151X sheep display pronounced CLN1 disease-relevant phenotypes. Our preliminary data extend these observations, revealing an earlier onset of neurologic disease, and widespread histologically and radiologically detectable pathology that is more pronounced than in PPT1-deficient mice. We have also shown that an intracranial injection of an AAV9 vector expressing PPT1 raises expression of this enzyme in the brain of sheep to supraphysiological levels. We believe CLN1 R151X sheep not only more accurately model human CLN1 disease, but also provide an ideal testing ground for optimizing the dosing and delivery of gene therapy in a fashion that is not possible in mice. We now propose to characterize the progression of these disease phenotypes in CLN1 R151X sheep, in order to provide detailed landmarks of disease progression using cognitive and neurologic testing, and MRI imaging, correlating these data with histological findings (Aim 1). We will also define the parameters of vector dosing and delivery routes to achieve widespread transduction of the sheep brain and spinal cord, and elevate PPT1 activity to levels predicted to be capable of producing therapeutic benefit (Aim 2). Finally, we shall determine the therapeutic efficacy, minimum effective dose, safety and clinical response to this optimized delivery of scAAV9-CCAG-PPT1 to the brain and spinal cord of CLN1 R151X sheep (Aim 3). These data will allow us to refine our gene therapy approach, and position us for entry into the CREATE-Bio development program towards clinical translation of the first effective treatment of this devastating disease.