Efficacy of AAV serotypes to target Schwann cells after intrathecal and intravenous delivery

Abstract

To optimize gene delivery to myelinating Schwann cells we compared clinically relevant AAV serotypes and injection routes. AAV9 and AAVrh10 vectors expressing either EGFP or the neuropathy-associated gene GJB1/Connexin32 (Cx32) under a myelin specific promoter were injected intrathecally or intravenously in wild type and Gjb1-null mice, respectively. Vector biodistribution in lumbar roots and sciatic nerves was higher in AAVrh10 injected mice while EGFP and Cx32 expression rates and levels were similar between the two serotypes. A gradient of biodistribution away from the injection site was seen with both intrathecal and intravenous delivery, while similar expression rates were achieved despite higher vector amounts injected intravenously. Quantified immune cells in relevant tissues were similar to non-injected littermates. Overall, AAV9 and AAVrh10 efficiently transduce Schwann cells throughout the peripheral nervous system with both clinically relevant routes of administration, although AAV9 and intrathecal injection may offer a more efficient approach for treating demyelinating neuropathies.

A translatable RNAi-driven gene therapy silences PMP22/Pmp22 genes and improves neuropathy in CMT1A mice

“…Another route of administration that could be easily translated to the clinic is intravenous injections. However, our studies in mice showed that intrathecal injection provides adequate biodistribution throughout the PNS, with much lower vector amounts injected compared with intravenous delivery (84). Intraneural injections of AAV.…”

“…Another question we considered, regarding translation, was the necessity to restrict miR871 expression to SCs alone. In our previous studies (84), we demonstrated that an AAV9 vector expressing a transgene through the SC-specific Mpz promoter efficiently transduced myelinating SCs throughout the PNS following a single lumbar intrathecal injection. In the current study, we used AAV9 to deliver a U6.miR.CMV.EGFP construct, in which both sequences (EGFP and miR871) were driven by ubiquitous promoters (CMV and U6, respectively) (Figure 1D).…”

“…In contrast, the lumbar intrathecal injection used in our study is considered a routine procedure that can be easily applied in the clinic, providing widespread biodistribution in the PNS. Compared with intravenous delivery, intrathecal delivery also requires a much lower viral volume to provide beneficial effects and hence results in lower toxicity (84,97). It remains to be shown that adequate biodistribution can also be achieved in larger animals before clinical translation.…”

Recent advances in the treatment of Charcot‐Marie‐Tooth neuropathies

“…11,12,68 Of note, intrathecal and intravenous routes of administration have been recently compared in adult mice using AAV9 carrying an Mpz (myelin protein zero) Schwann cellspecific promoter and similar efficiency of Schwann cell transduction has been observed. 69 However, intraneural injection has been found to be the most efficient route of administration to specifically target Schwann cells in the demyelinating CMT1A. 10 For axonal forms, AAV9 vectors have been delivered by intracerebroventricular (i.c.v.)…”

Pharmacologic Targeting of the C-Terminus of Heat Shock Protein 90 Improves Neuromuscular Function in Animal Models of Charcot Marie Tooth X1 Disease

“…Since CMTX1 is a single gene disorder due to the loss of Cx32 function, somatic cell gene therapy provides a potential gold standard treatment. Indeed, utilizing adeno-associated virus 9 to deliver wild-type Cx32 has proven beneficial in improving nerve electrophysiology and myelin deficits in Cx32def mice. , However, the clinical path forward for gene therapy has many hurdles and patients contraindicated for this treatment may still benefit from a small molecule therapy.…”