AAV1.NT-3 gene therapy attenuates spontaneous autoimmune peripheral polyneuropathy.

The spontaneous autoimmune peripheral polyneuropathy (SAPP) model in B7-2 knockout non-obese diabetic mice shares clinical and histological features with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Secondary axonal loss is prominent in the progressive phase of this neuropathy. Neurotrophin 3 (NT-3) is an important autocrine factor supporting Schwann cell survival and differentiation and stimulates neurite outgrowth and myelination. The anti-inflammatory and immunomodulatory effects of NT-3 raised considerations of potential efficacy in the SAPP model that could be applicable to CIDP. For this study, scAAV1.tMCK.NT-3 was delivered to the gastrocnemius muscle of 25-week-old SAPP mice. Measurable NT-3 levels were found in the serum at 7-week postgene delivery. The outcome measures included functional, electrophysiological and histological assessments. At week 32, NT-3-treated mice showed increased hind limb grip strength that correlated with improved compound muscle action potential amplitude. Myelinated fiber density was 1.9 times higher in the NT-3-treated group compared with controls and the number of demyelinated axons was significantly lower. The remyelinated nerve fiber population was significantly increased. These improved histopathological parameters from scAAV1.tMCK.NT-3 treatment occurred in the setting of reduced sciatic nerve inflammation. Collectively, these findings suggest a translational application to CIDP.