Niemann-Pick Disease Type C (NPC) is a rare lysosomal storage disease with an estimated incidence of 1:100,000 to 1:120,000. 95% of NPC cases are caused by autosomal recessive mutations in Intracellular Cholesterol Transporter 1 (NPC1). NPC1 is a transmembrane protein and functions as a trans-lysosomal lipid transporter.1,2 Adeno-associated virus (AAV) gene therapy’s recent success offers a unique opportunity for treating neurogenetic diseases such as NPC that has not been previously explored.3 All cells continuously release extracellular vesicles (EVs) that carry large biological molecules, as intercellular communication mediators. 4 We hypothesize that incorporating EV-mRNA signal in AAV vector expressing NPC1 may facilitate by-stander-effects and enhance the efficacy.5 To test our hypothesis, we constructed pucIDT-hNPC1 plasmids with/without an EV-mRNA packaging ZC signal and tested it in human NPC skin fibroblasts. The hNPC1ZC plasmid increased hNPC1 mRNA expression and mediated the release of EVs-hNPC1-mRNA. Furthermore, human NPC cells excrete significantly more EVs than normal human cells, which were reduced to normal levels after transfection with the pucIDT-hNPC1zc plasmid. These data support our hypothesis that the incorporation of ZC signal in the hNPC1 vector directs packaging of hNPC1-mRNA in EVs. In future studies, we will determine if EV-hNPC1 mRNA can be transported to NPC cells and translated into functional NPC1 protein. We will then clone the hNPC1zc into rAAV-hNPC1zc vector and test the rAAV vector in vivo in NPC mice. This study supports the therapeutic potential of using the EV-mRNA cargo signal in rAAV-hNPC1 vector, allowing optimal benefits for treating NPC with relatively low dose, without having to transduce every individual cell.
Kendall Diaz (Sat,) studied this question.