Screened AAV Variants Permit Efficient Transduction Access to Supporting Cells and Hair Cells

By June 7, 2019

Shu, Yilai1,2; Wang, Jinghan1,2; Hu, Xinde3; Yang, Hui3; Li, Huawei1,2 
1 ENT Institute and Otorhinolaryngology Department, Affiliated Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China;
2 NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China;
3 Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of
Primate Neurobiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.

Lack of efficient delivery system into mammalian inner ear remains a major barrier for  gene therapy. Adeno-associated viral (AAV) vectors have become the vector of choice for gene delivery. We report the screen of pseudoserotype vectors including AAV-PHP.eB, AAV-DJ and AAV-8, AAV-9  delivery into mammalian inner ear in vivo.

To screen AAV vectors that target hair cells (HCs) and supporting cells ( SCs), we packaged different AAVs (AAV-8, AAV-9, AAV-DJ and AAV-PHP.eB, AAV-DJ) that expressing tdTomato and injected them in mice. Three weeks after injection, we performed immunofluorescence analysis in the cochlea. Auditory brainstem response (ABR) thresholds of the inner ear were measured.

AAV-PHP.eB, AAV-8 and AAV-9 achieved infection efficiencies at 100.00%, 98.94% and 98.41% in the apical turn of IHCs respectively, while AAV-DJ showed very rare infection. In the middle and basal turn of IHCs, AAV-PHP.eB also achieved very high efficiency (99.07% and 100.00%), while AAV-8 and AAV-9 achieved relatively low efficiencies. For infection efficiencies of OHCs, AAV-PHP.eB and AAV-9 had  97.48% and 33.62%, respectively. Interestingly, we found that AAV-DJ showed much higher efficiency (52.51%) of SC infection. We also found that both IHCs and OHCs were infected efficiently with only a dose of 3 x 109 vg AAV- PHP.eB and SCs were infected at up to 50% with a dose of 1 x 1010 vg. Hearing was preserved well after infection.

AAV-PHP.B showed the extremely high transduction efficacy on HCs. AAV-DJ demonstrated a high ratio to infect SCs. They are potent viral vectors to achieve genetic agent delivery, holding a great promise for gene therapy approaches to deafness.