AAV9-mediated targeting of natural antisense transcript as a novel treatment for Dravet syndrome.

Dravet syndrome (DS) is a severe childhood developmental and epileptic encephalopathy. Symptoms usually manifest in the first year of life and include prolonged severe seizures, developmental delay, severe intellectual disability, and increased mortality. Approximately, 90% of patients carry a heterozygous loss-of-function mutation in SCN1A, encoding a voltage-gated sodium ion channel, NaV1.1. NaV1.1 is expressed in the brain and at a lower level, in the heart. Previous studies have identified a long non-coding RNA (lncRNA), which specifically downregulates SCN1A expression. This natural antisense transcript (NAT) can be modulated by AntagoNATs, small synthetic oligonucleotides. AntagoNATs have shown to improve seizure frequency in DS mice after repeated administration. Here, we have developed new AntagoNATs and incorporated these into an adeno-associated virus serotype 9 (AAV9) gene therapy vector. We administered two new AAV9-AntagoNAT-H and AntagoNAT-K vectors to newborn Scn1a +/- mice via intracerebroventricular (i.c.v.) and intravenous (i.v.) injection to deliver vector to the brain and heart. AAV9-AntagoNAT-H significantly increased survival, decreased the frequency of febrile and spontaneous seizures. In this proof-of-concept study, we have demonstrated for the first time the delivery of AntagoNAT via an AAV9 vector. Thus, offering the possibility of a one-time treatment for DS patients.