Gene Transfer with AAV9-PHP.B Rescues Hearing in a Mouse Model of Usher Syndrome 3A and Transduces Hair Cells in a Non-human Primate

Abstract

Hereditary hearing loss often results from mutation of genes expressed by cochlear hair cells. Gene addition using AAV vectors has shown some efficacy in mouse models, but clinical application requires two additional advances. First, new AAV capsids must mediate efficient transgene expression in both inner and outer hair cells of the cochlea. Second, to have the best chance of clinical translation, these new vectors must also transduce hair cells in non-human primates. Here, we show that an AAV9 capsid variant, PHP.B, produces efficient transgene expression of a GFP reporter in both inner and outer hair cells of neonatal mice. We show also that AAV9-PHP.B mediates almost complete transduction of inner and outer HCs in a non-human primate. In a mouse model of Usher syndrome type 3A deafness (gene CLRN1), we use AAV9-PHP.B encoding Clrn1 to partially rescue hearing. Thus, we have identified a vector with promise for clinical treatment of hereditary hearing disorders, and we demonstrate, for the first time, viral transduction of the inner ear of a primate with an AAV vector.

Development of the Mouse and Human Cochlea at Single Cell Resolution

“…Furthermore, the distinct cellular tropism of hearing loss gene expression needs to be accounted for when selecting viral vectors and appropriate promoters for gene therapy. Although some currently available viral vectors appear relatively efficient at transducing hair cells (György et al, 2019; Landegger et al, 2017; Yoshimura et al, 2018), we will likely need to identify additional viral vectors capable of efficiently transducing other distinct cell types within the cochlea for those genes expressed within other cell populations.…”

Historical Aspects of Gene Therapy and Stem Cell Therapy in the Treatment of Hearing and Balance Disorder

“…This treatment with the Anc80L65 ush1c vector restored both hearing and balance functions to near wild type (control) levels (Pan et al, ). Here is an example of another variant of an AAV gene therapy vector (i.e., AAV9‐PHP.B) used to deliver a therapeutic gene to a mouse model for Usher's syndrome 3A (György et al, ). A unique quality of the AAV9‐PHP.B vector is its ability to transduce nearly all of the inner and outer hair cells in a non‐human primate.…”

“…A unique quality of the AAV9‐PHP.B vector is its ability to transduce nearly all of the inner and outer hair cells in a non‐human primate. Treatment of the Usher's syndrome 3A mice with the vector containing a wild type clrn1 gene (i.e., AAV9‐PHP.B clrn1 ) resulted in a partial rescue of hearing (György et al, ). These results from the treatment of Usher's syndrome mice (Emptoz et al, ; Isgrig et al, ; Pan et al, ; György et al, ) are very encouraging toward future clinical application of gene therapy for the treatment of inner ear disorders where mutations in stereociliary structural proteins are involved.…”

“…Treatment of the Usher's syndrome 3A mice with the vector containing a wild type clrn1 gene (i.e., AAV9‐PHP.B clrn1 ) resulted in a partial rescue of hearing (György et al, ). These results from the treatment of Usher's syndrome mice (Emptoz et al, ; Isgrig et al, ; Pan et al, ; György et al, ) are very encouraging toward future clinical application of gene therapy for the treatment of inner ear disorders where mutations in stereociliary structural proteins are involved. The vector of choice for the delivery of therapeutic genes appears to be modified AAV vectors (Suzuki et al, ; Kim et al, ) because of their ability to transduce both auditory and vestibular hair cells and not to evoke a protective foreign body response from the host avoiding the need for the use of immunosuppressive drugs.…”

“…A good example of this would be a mutation of a structural protein causing a defect that could be corrected by expression of a gene that encodes a correct form (i.e., wild type) of the mutated protein (e.g., sans protein; Emptoz et al, ). Other important factors are having a safe delivery method such as a viral vector that will not initiate a host immune response (e.g., a selected AAV vector; György et al, ; Akil and Lustig, ) and also a safe route for delivery into the perilymphatic spaces of a patient's cochlea (e.g., via the round window membrane injection route into the scala tympani). When using AAV vectors to deliver a therapeutic gene, the size available for insertion of the therapeutic gene is an important factor.…”