Less than a month after getting a new gene therapy treatment, a young girl named Li “Yiyi” Xincheng heard sounds without her cochlear implant for the first time.  Born deaf, Yiyi is one of five children in a study that used two viruses to replace parts of a defective gene that caused her deafness.    

Most of the mutations in a gene called OTOF cause profound deafness in people. They disrupt signaling inside the ear’s inner hair cells.  Hairs called IHCs sit inside the cochlea, a structure in the inner ear. Sound waves stimulate and bend the hair in ways that become electrical impulses carried by the auditory nerve to the brain.  

Mutations in the OTOF gene prevent the IHCs from sending signals to the auditory nerve.  In the study, five children with OTOF mutations were treated. The two engineered viruses used were versions of Adeno-Associated Virus and aren’t big enough to carry OTOF which is why different parts of it were carried by the two viruses.   

The scientists grew millions of copies of these two viruses and injected them into the children’s cochlea. The viruses then started infecting the IHCs and the genes carried by the engineered viruses began exchanging with the defective ones in the IHCs. Enough of the mutated genes were restored to allow four of the five children to hear on their own for the first time. If the results are permanent, the treatment will change the lives of these children and others after them.  

We are Drs. David Niesel and Norbert Herzog, at UTMB and Quinnipiac University, where biomedical discoveries shape the future of medicine.   For much more and our disclaimer go to medicaldiscoverynews.com or subscribe to our podcast. Sign up for expanded print episodes at www.illuminascicom.com or our podcasts at:  Medical Discovery News (buzzsprout.com)