Comparative analysis of RNA versus protein splicing in dual AAV-mediated gene therapy in a mouse model of DFNB9 deafness.

Pathological mutations in the OTOF gene cause autosomal recessive deafness 9 (DFNB9). Although dual-adeno-associated virus (AAV) gene replacement therapy has been shown to partially rescue the hearing of patients with DFNB9, the therapeutic effects still need further exploration. To investigate the impact of different recombination strategies on the efficacy of OTOF gene therapy, we constructed five dual-AAV1 therapeutic agents using RNA or protein splicing principles. Based on the recombination strategy using RNA splicing, the AAV1-AK system rescued the hearing of Otof-/- mice to 55-70 dB, which outperformed the AAV1-AP and AAV1-TS systems. Based on protein splicing, the AAV1-intein system rescued the hearing of Otof-/- mice to 35-70 dB, which outperformed that of AAV1-AK, and the effects lasted up to 12 months after injection in both newborn and adult mice. The efficacy of otoferlin re-expression and the number and functional restoration of ribbon synapses in the AAV1-intein system were also better than the AAV1-AK system. These results show that protein recombination is more efficient than nucleic acid recombination for gene therapy in DFNB9. Therefore, this work provides not only data for optimization of DFNB9 gene therapy but also a reference for the delivery of other large genes.