In patients with SMA1, a single intravenous infusion of adeno-associated viral vector containing DNA coding for SMN resulted in longer survival, superior achievement of motor milestones, and better motor function than in historical cohorts. Further studies are necessary to confirm the safety and efficacy of this gene therapy. (Funded by AveXis and others; ClinicalTrials.gov number, NCT02122952 .).

Delivery of therapeutics to the brain and spinal cord remains a challenge for neurodegenerative diseases, such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). The blood-brain-barrier (BBB) hampers delivery of therapeutics to neurons, glia, and surrounding cell types of the central nervous system (CNS) that may be involved in disease progression. Here, we describe an intravenous injection of adeno-associated-virus-9 (AAV-9) in mouse that efficiently targets brain, dorsal root ganglia and spinal cord motor neurons in neonatal animals and astrocytes in adult mouse brain and spinal cords, offering a new therapeutic delivery approach to deliver genes to widespread regions within the CNS.

Amyotrophic Lateral Sclerosis (ALS) is a fatal motor neuron (MN) disease with astrocytes implicated as a significant contributor to MN death in familial ALS (fALS)1–5. However, these conclusions, in part, derive from rodent models of fALS based upon dominant mutations within the superoxide dismutase 1 (SOD1) gene which account for less than 2% of all ALS cases2, 4, 5. Here, we generated astrocytes from post-mortem tissue from both fALS and sporadic ALS (sALS) patients, and show that astrocytes derived from both patient groups are similarly toxic to MNs. In addition, we show that SOD1 is a viable target for sALS, as its knockdown significantly attenuates astrocyte-mediated toxicity towards MNs. Our data highlight astrocytes as a non-cell autonomous component in sALS and provide the first in vitro model system to investigate common disease mechanisms and evaluate potential therapies for sALS and fALS.

Spinal muscular atrophy (SMA), the most common autosomal recessive neurodegenerative disease affecting children, results in impaired motor neuron function1. Despite knowledge of the pathogenic role of decreased survival motor neuron (SMN) protein levels, efforts to increase SMN have not resulted in a treatment for patients. We recently demonstrated that self-complementary adeno-associated virus 9 (scAAV9) can infect ~60% of motor neurons when injected intravenously into neonatal mice2–4. Here we use scAAV9-mediated postnatal day 1 vascular gene delivery to replace SMN in SMA pups and rescue motor function, neuromuscular physiology and life span. Treatment on postnatal day 5 results in partial correction, whereas postnatal day 10 treatment has little effect, suggesting a developmental period in which scAAV9 therapy has maximal benefit. Notably, we also show extensive scAAV9-mediated motor neuron transduction after injection into a newborn cynomolgus macaque. This demonstration that scAAV9 traverses the blood-brain barrier in a nonhuman primate emphasizes the clinical potential of scAAV9 gene therapy for SMA.

SUMMARY Neuroinflammation is one of the most striking hallmarks of amyotrophic lateral sclerosis (ALS). Nuclear Factor-kappa B (NF-κB), a master regulator of inflammation, is upregulated in spinal cords of ALS patients and SOD1-G93A mice. In this study, we show that selective NF-κB inhibition in ALS astrocytes is not sufficient to rescue motor neuron (MN) death. However, the localization of NF-κB activity and subsequent deletion of NF-κB signaling in microglia rescued MNs from microglial-mediated death in vitro and extended survival in ALS mice by impairing pro-inflammatory microglial activation. Conversely, constitutive activation of NF-κB selectively in wild-type microglia induced gliosis and MN death in vitro and in vivo. Taken together, these data provide a mechanism by which microglia induce MN death in ALS, and suggest a novel therapeutic target that can be modulated to slow the progression of ALS and possibly other neurodegenerative diseases by which microglial activation plays a role.