Combined AAV-mediated gene replacement therapy improves auditory function in a mouse model of human DFNB42 deafness.

Hearing loss is a common disorder affecting nearly 20% of the world's population. Recently, studies have shown that inner ear gene therapy can improve auditory function in several mouse models of hereditary hearing loss. In most of these studies, the underlying mutations affect only a small number of cell types of the inner ear (e.g., sensory hair cells). Here, we applied inner ear gene therapy to the Ildr1Gt(D178D03)Wrst (Ildr1w-/-) mouse, a model of human DFNB42, non-syndromic autosomal recessive hereditary hearing loss associated with ILDR1 variants. ILDR1 is an integral protein of the tricellular tight junction complex and is expressed by diverse inner ear cell types in the organ of Corti and the cochlear lateral wall. We simultaneously applied two synthetic adeno-associated viruses (AAVs) with different tropism to deliver Ildr1 cDNA to the Ildr1w-/- mouse inner ear: one targeting the organ of Corti (AAV2.7m8) and the other targeting the cochlear lateral wall (AAV8BP2). We showed that combined AAV2.7m8/AAV8BP2 gene therapy improves cochlear structural integrity and auditory function in Ildr1w-/- mice.

Timing, number, and type of sexual partners associated with risk of oropharyngeal cancer.

BACKGROUND: Case-control studies from the early 2000s demonstrated that human papillomavirus-related oropharyngeal cancer (HPV-OPC) is a distinct entity associated with number of oral sex partners. Using contemporary data, we investigated novel risk factors (sexual debut behaviors, exposure intensity, and relationship dynamics) and serological markers on odds of HPV-OPC. METHODS: HPV-OPC patients and frequency-matched controls were enrolled in a multicenter study from 2013 to 2018. Participants completed a behavioral survey. Characteristics were compared using a chi-square test for categorical variables and a t test for continuous variables. Adjusted odds ratios (aOR) were calculated using logistic regression. RESULTS: A total of 163 HPV-OPC patients and 345 controls were included. Lifetime number of oral sex partners was associated with significantly increased odds of HPV-OPC (>10 partners: odds ratio [OR], 4.3 [95% CI, 2.8-6.7]). After adjustment for number of oral sex partners and smoking, younger age at first oral sex (<18 vs >20 years: aOR, 1.8 [95% CI, 1.1-3.2]) and oral sex intensity (>5 sex-years: aOR, 2.8 [95% CI, 1.1-7.5]) remained associated with significantly increased odds of HPV-OPC. Type of sexual partner such as older partners when a case was younger (OR, 1.7 [95% CI, 1.1-2.6]) or having a partner who had extramarital sex (OR, 1.6 [95% CI, 1.1-2.4]) was associated with HPV-OPC. Seropositivity for antibodies to HPV16 E6 (OR, 286 [95% CI, 122-670]) and any HPV16 E protein (E1, E2, E6, E7; OR, 163 [95% CI, 70-378]) was associated with increased odds of HPV-OPC. CONCLUSION: Number of oral sex partners remains a strong risk factor for HPV-OPC; however, timing and intensity of oral sex are novel independent risk factors. These behaviors suggest additional nuances of how and why some individuals develop HPV-OPC.

SLC26A4-linked CEVA haplotype correlates with phenotype in patients with enlargement of the vestibular aqueduct.

BACKGROUND: Recessive mutations of coding regions and splice sites of the SLC26A4 gene cause hearing loss with enlargement of the vestibular aqueduct (EVA). Some patients also have a thyroid iodination defect that can lead to multinodular goiter as part of Pendred syndrome. A haplotype of variants upstream of SLC26A4, called CEVA, acts as a pathogenic recessive allele in trans to mutations affecting the coding regions or splice sites of SLC26A4. Our first hypothesis is that CEVA, acting as a pathogenic recessive allele, is correlated with a less severe phenotype than mutations affecting the coding regions and splice sites of SLC26A4. Our second hypothesis is that CEVA acts as a modifier of the phenotype in patients with EVA caused by mutations affecting the coding regions or splice sites of both alleles of SLC26A4 or EVA caused by other factors. METHODS: This was a prospective cohort study of 114 individuals and 202 ears with EVA. To test our first hypothesis, we compared the thyroid and auditory phenotypes of subjects with mutations affecting coding regions of both alleles of SLC26A4 with those of subjects carrying CEVA in trans to mutations affecting the coding regions. To test our second hypothesis, we compared the phenotypes associated with the presence versus absence of CEVA among subjects with no coding region mutations, as well as among subjects with mutations affecting coding regions of both alleles. RESULTS: Subjects carrying CEVA in trans to a mutation of SLC26A4 have a normal thyroid phenotype and less severe hearing loss in comparison to individuals with mutations affecting coding regions of both alleles of SLC26A4. In subjects with no mutant alleles of SLC26A4, hearing loss was more severe in subjects who carry the CEVA haplotype in comparison to non-carriers. There was no correlation of CEVA with the phenotype of subjects with mutations affecting coding regions of both alleles. CONCLUSIONS: CEVA, acting as a likely pathogenic recessive allele, is associated with a less severe phenotype than alleles with a mutation affecting the coding regions or splice sites of SLC26A4. CEVA may act as a genetic modifier in patients with EVA caused by other factors.

Gene Therapy Restores Balance and Auditory Functions in a Mouse Model of Usher Syndrome.

Dizziness and hearing loss are among the most common disabilities. Many forms of hereditary balance and hearing disorders are caused by abnormal development of stereocilia, mechanosensory organelles on the apical surface of hair cells in the inner ear. The deaf whirler mouse, a model of human Usher syndrome (manifested by hearing loss, dizziness, and blindness), has a recessive mutation in the whirlin gene, which renders hair cell stereocilia short and dysfunctional. In this study, wild-type whirlin cDNA was delivered to the inner ears of neonatal whirler mice using adeno-associated virus serotype 2/8 (AAV8-whirlin) by injection into the posterior semicircular canal. Unilateral whirlin gene therapy injection was able to restore balance function as well as improve hearing in whirler mice for at least 4 months. Our data indicate that gene therapy is likely to become a treatment option for hereditary disorders of balance and hearing.

Gene Therapy Restores Hair Cell Stereocilia Morphology in Inner Ears of Deaf Whirler Mice.

Hereditary deafness is one of the most common disabilities affecting newborns. Many forms of hereditary deafness are caused by morphological defects of the stereocilia bundles on the apical surfaces of inner ear hair cells, which are responsible for sound detection. We explored the effectiveness of gene therapy in restoring the hair cell stereocilia architecture in the whirlin mouse model of human deafness, which is deaf due to dysmorphic, short stereocilia. Wild-type whirlin cDNA was delivered via adeno-associated virus (AAV8) by injection through the round window of the cochleas in neonatal whirler mice. Subsequently, whirlin expression was detected in infected hair cells (IHCs), and normal stereocilia length and bundle architecture were restored. Whirlin gene therapy also increased inner hair cell survival in the treated ears compared to the contralateral nontreated ears. These results indicate that a form of inherited deafness due to structural defects in cochlear hair cells is amenable to restoration through gene therapy.

Hearing Loss after Round Window Surgery in Mice Is due to Middle Ear Effusion.

BACKGROUND: Delivery of therapeutic agents directly through the round window (RW) offers promise for treating sensorineural hearing loss. However, hearing loss can result from the surgical approach itself, and the reasons for this are poorly understood. We examined the hearing loss following the 3 major steps involved with the RW approach to access the mouse cochlea: bullostomy, RW puncture, and RW injection. METHODS: Twenty-one adult CBA/J mice underwent bullostomy alone, 10 underwent RW puncture, and 8 underwent RW injection with PBS with 5% glycerol. Auditory brainstem responses (ABR) and otoscopy were performed preoperatively and up to 6 weeks postoperatively. Hair cells were stained, and survival was assessed using immunofluorescence. RESULTS: One week postoperatively, mice in all groups showed significant threshold shifts. Otoscopy revealed approximately half of all mice had middle ear effusion (MEE), with a higher incidence of effusion in the RW puncture and RW injection groups. Those with MEE had significant ABR threshold shifts, whereas those without MEE had minimal hearing loss. MEE persisted through 6 weeks in a majority of cases, but in those mice with MEE resolution, there was at least partial improvement in hearing. Immunohistochemistry showed minimal loss of hair cells in all animals. CONCLUSION: MEE is highly correlated with hearing loss in mice undergoing RW surgery. Otoscopy is an important adjunct to consider after ear surgery in mice, as MEE may contribute to postsurgical hearing loss.

Gene therapy for sensorineural hearing loss.

Gene therapy is a promising treatment modality that is being explored for several inherited disorders. Multiple human gene therapy clinical trials are currently ongoing, but few are directed at hearing loss. Hearing loss is one of the most prevalent sensory disabilities in the world, and genetics play an important role in the pathophysiology of hearing loss. Gene therapy offers the possibility of restoring hearing by overcoming the functional deficits created by the underlying genetic mutations. In addition, gene therapy could potentially be used to induce hair cell regeneration by delivering genes that are critical to hair cell differentiation into the cochlea. In this review, we examine the promises and challenges of applying gene therapy to the cochlea. We also summarize recent studies that have applied gene therapy to animal models of hearing loss.

Early-Onset Hearing Loss in Mouse Models of Alzheimer's Disease and Increased DNA Damage in the Cochlea.

There is considerable interest in whether sensory deficiency is associated with the development of Alzheimer's disease (AD). Notably, the relationship between hearing impairment and AD is of high relevance but still poorly understood. In this study, we found early-onset hearing loss in two AD mouse models, 3xTgAD and 3xTgAD/Polß+/-. The 3xTgAD/Polß+/- mouse is DNA repair deficient and has more humanized AD features than the 3xTgAD. Both AD mouse models showed increased auditory brainstem response (ABR) thresholds between 16 and 32 kHz at 4 weeks of age, much earlier than any AD cognitive and behavioral changes. The ABR thresholds were significantly higher in 3xTgAD/Polß+/- mice than in 3xTgAD mice at 16 kHz, and distortion product otoacoustic emission signals were reduced, indicating that DNA damage may be a factor underlying early hearing impairment in AD. Poly ADP-ribosylation and protein expression levels of DNA damage markers increased significantly in the cochlea of the AD mice but not in the adjacent auditory cortex. Phosphoglycerate mutase 2 levels and the number of synaptic ribbons in the presynaptic zones of inner hair cells were decreased in the cochlea of the AD mice. Furthermore, the activity of sirtuin 3 was downregulated in the cochlea of these mice, indicative of impaired mitochondrial function. Taken together, these findings provide new insights into potential mechanisms for hearing dysfunction in AD and suggest that DNA damage in the cochlea might contribute to the development of early hearing loss in AD.

Immune responses in the mammalian inner ear and their implications for AAV-mediated inner ear gene therapy.

Adeno-associated virus (AAV)-mediated inner ear gene therapy is a promising treatment option for hearing loss and dizziness. Several studies have shown that AAV-mediated inner ear gene therapy can be applied to various mouse models of hereditary hearing loss to improve their auditory function. Despite the increase in AAV-based animal and clinical studies aiming to rescue auditory and vestibular functions, little is currently known about the host immune responses to AAV in the mammalian inner ear. It has been reported that the host immune response plays an important role in the safety and efficacy of viral-mediated gene therapy. Therefore, in order for AAV-mediated gene therapy to be successfully and safely translated into patients with hearing loss and dizziness, a better understanding of the host immune responses to AAV in the inner ear is critical. In this review, we summarize the current knowledge on host immune responses to AAV-mediated gene therapy in the mammalian inner ear and other organ systems. We also outline the areas of research that are critical for ensuring the safety and efficacy of AAV-mediated inner ear gene therapy in future clinical and translational studies.

Engineering olivocochlear inhibition to reduce acoustic trauma.

Efferent brain-stem neurons release acetylcholine to desensitize cochlear hair cells and can protect the inner ear from acoustic trauma. That protection is absent from knockout mice lacking efferent inhibition and is stronger in mice with a gain-of-function point mutation of the hair cell-specific nicotinic acetylcholine receptor. The present work uses viral transduction of gain-of-function receptors to restore acoustic prophylaxis to the knockout mice. Widespread postsynaptic expression of the transgene was visualized in excised tissue with a fluorophore-conjugated peptide toxin that binds selectively to hair cell acetylcholine receptors. Viral transduction into efferent knockout mice reduced the temporary hearing loss measured 1 day post acoustic trauma. The acoustic evoked-response waveform (auditory brain-stem response) recovered more rapidly in treated mice than in control mice. Thus, both cochlear amplification by outer hair cells (threshold shift) and afferent signaling (evoked-response amplitude) in knockout mice were protected by viral transduction of hair cell acetylcholine receptors. Gene therapy to strengthen efferent cochlear feedback could be complementary to existing and future therapies to prevent hearing loss, including ear coverings, hearing aids, single-gene repair, or small-molecule therapies.

Dual-AAV vector-mediated expression of MYO7A improves vestibular function in a mouse model of Usher syndrome 1B.

Usher syndrome is the most common cause of deafness-blindness in the world. Usher syndrome type 1B (USH1B) is associated with mutations in MYO7A. Patients with USH1B experience deafness, blindness, and vestibular dysfunction. In this study, we applied adeno-associated virus (AAV)-mediated gene therapy to the shaker-1 (Myo7a4626SB/4626SB) mouse, a model of USH1B. The shaker-1 mouse has a nonsense mutation in Myo7a, is profoundly deaf throughout life, and has significant vestibular dysfunction. Because of the ∼6.7-kb size of the MYO7A cDNA, a dual-AAV approach was used for gene delivery, which involves splitting human MYO7A cDNA into 5' and 3' halves and cloning them into two separate AAV8(Y733F) vectors. When MYO7A cDNA was delivered to shaker-1 inner ears using the dual-AAV approach, cochlear hair cell survival was improved. However, stereocilium organization and auditory function were not improved. In contrast, in the vestibular system, dual-AAV-mediated MYO7A delivery significantly rescued hair cell stereocilium morphology and improved vestibular function, as reflected in a reduction of circling behavior and improved vestibular sensory-evoked potential (VsEP) thresholds. Our data indicate that dual-AAV-mediated MYO7A expression improves vestibular function in shaker-1 mice and supports further development of this approach for the treatment of disabling dizziness from vestibular dysfunction in USH1B patients.

AAV8BP2 and AAV8 transduce the mammalian cochlear lateral wall and endolymphatic sac with high efficiency.

Inner ear gene therapy using adeno-associated viruses (AAVs) has been successfully applied to several mouse models of hereditary hearing loss to improve their auditory function. While most inner ear gene therapy studies have focused on the mechanosensory hair cells and supporting cells in the organ of Corti, the cochlear lateral wall and the endolymphatic sac have not garnered much attention. The cochlear lateral wall and the endolymphatic sac play critical roles in inner ear ionic and fluid homeostasis. Mutations in genes expressed in the cochlear lateral wall and the endolymphatic sac are present in a large percentage of patients with hereditary hearing loss. In this study, we examine the transduction patterns and efficiencies of conventional (AAV2 and AAV8) and synthetic (AAV2.7m8, AAV8BP2, and Anc80L65) AAVs in the mouse inner ear. We found that AAV8BP2 and AAV8 are capable of transducing the marginal cells and intermediate cells in the stria vascularis. These two AAVs can also transduce the epithelial cells of the endolymphatic sac. Our data suggest that AAV8BP2 and AAV8 are highly useful viral vectors for gene therapy studies targeting the cochlear lateral wall and the endolymphatic sac.

Pediatric Bilateral Sensorineural Hearing Loss: Minimum Test Battery and Referral Criteria for Cochlear Implant Candidacy Evaluation.

Among the various cochlear implant systems approved by the Food and Drug Administration, current labeling for pediatric usage encompasses (1) bilateral profound bilateral sensorineural hearing loss in children aged 9 to 24 months and bilateral severe to profound sensorineural hearing loss in children older than 2 years; (2) use of appropriately fitted hearing aids for 3 months (this can be waived if there is evidence of ossification); and (3) demonstration of limited progress with auditory, speech, and language development. Pediatric guidelines require children to have significantly worse speech understanding before qualifying for cochlear implantation. The early years of life have been shown to be critical for speech and language development, and auditory deprivation is especially detrimental during this crucial time.Level of evidence: 2.

Assessment of Sudden Sensorineural Hearing Loss After COVID-19 Vaccination.

IMPORTANCE: Emerging reports of sudden sensorineural hearing loss (SSNHL) after COVID-19 vaccination within the otolaryngological community and the public have raised concern about a possible association between COVID-19 vaccination and the development of SSNHL. OBJECTIVE: To examine the potential association between COVID-19 vaccination and SSNHL. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study and case series involved an up-to-date population-based analysis of 555 incident reports of probable SSNHL in the Centers for Disease Control and Prevention Vaccine Adverse Events Reporting System (VAERS) over the first 7 months of the US vaccination campaign (December 14, 2020, through July 16, 2021). In addition, data from a multi-institutional retrospective case series of 21 patients who developed SSNHL after COVID-19 vaccination were analyzed. The study included all adults experiencing SSNHL within 3 weeks of COVID-19 vaccination who submitted reports to VAERS and consecutive adult patients presenting to 2 tertiary care centers and 1 community practice in the US who were diagnosed with SSNHL within 3 weeks of COVID-19 vaccination. EXPOSURES: Receipt of a COVID-19 vaccine produced by any of the 3 vaccine manufacturers (Pfizer-BioNTech, Moderna, or Janssen/Johnson & Johnson) used in the US. MAIN OUTCOMES AND MEASURES: Incidence of reports of SSNHL after COVID-19 vaccination recorded in VAERS and clinical characteristics of adult patients presenting with SSNHL after COVID-19 vaccination. RESULTS: A total of 555 incident reports in VAERS (mean patient age, 54 years [range, 15-93 years]; 305 women [55.0%]; data on race and ethnicity not available in VAERS) met the definition of probable SSNHL (mean time to onset, 6 days [range, 0-21 days]) over the period investigated, representing an annualized incidence estimate of 0.6 to 28.0 cases of SSNHL per 100 000 people per year. The rate of incident reports of SSNHL was similar across all 3 vaccine manufacturers (0.16 cases per 100 000 doses for both Pfizer-BioNTech and Moderna vaccines, and 0.22 cases per 100 000 doses for Janssen/Johnson & Johnson vaccine). The case series included 21 patients (mean age, 61 years [range, 23-92 years]; 13 women [61.9%]) with SSNHL, with a mean time to onset of 6 days (range, 0-15 days). Patients were heterogeneous with respect to clinical and demographic characteristics. Preexisting autoimmune disease was present in 6 patients (28.6%). Of the 14 patients with posttreatment audiometric data, 8 (57.1%) experienced improvement after receiving treatment. One patient experienced SSNHL 14 days after receiving each dose of the Pfizer-BioNTech vaccine. CONCLUSIONS AND RELEVANCE: In this cross-sectional study, findings from an updated analysis of VAERS data and a case series of patients who experienced SSNHL after COVID-19 vaccination did not suggest an association between COVID-19 vaccination and an increased incidence of hearing loss compared with the expected incidence in the general population.

Canal dehiscence.

PURPOSE OF REVIEW: The aim is to review canal dehiscence involving the superior, lateral, and posterior semicircular canals. The main focus will be on superior semicircular canal dehiscence. RECENT FINDINGS: Canal dehiscence involving the superior, lateral, and posterior semicircular canal can have different etiologies, including developmental abnormality, congenital defect, chronic otitis media with cholesteatoma, and high-riding jugular bulb. However, their clinical presentation can be very similar, with patients complaining of vertigo, oscillopsia, and sometimes hearing loss. Canal dehiscence causes an abnormal communication between the inner ear and the surrounding structures. This creates a third mobile window within the inner ear, disrupting its normal mechanics and causing symptoms. SUMMARY: Superior semicircular canal dehiscence is now a well-established entity in the medical literature. Surgical repair is effective at relieving patients' vestibular symptoms. Lateral semicircular canal dehiscence is usually associated with chronic otitis media. Posterior semicircular canal dehiscence is a rare entity, with similar clinical presentations and treatment options as the other canal dehiscences.

Validation of a 3D-printed human temporal bone model for otology surgical skill training.

HYPOTHESIS: Three-dimensional (3D) printed temporal bones are comparable to cadaveric temporal bones as a training tool for otologic surgery. BACKGROUND: Cadaveric temporal bone dissection is an integral part of otology surgical training. Unfortunately, availability of cadaveric temporal bones is becoming much more limited and concern regarding chemical and biological risks persist. In this study, we examine the validity of 3D-printed temporal bone model as an alternative training tool for otologic surgery. METHODS: Seventeen otolaryngology trainees participated in the study. They were asked to complete a series of otologic procedures using 3D-printed temporal bones. A semi-structured questionnaire was used to evaluate their dissection experience on the 3D-printed temporal bones. RESULTS: Participants found that the 3D-printed temporal bones were anatomically realistic compared to cadaveric temporal bones. They found that the 3D-printed temporal bones were useful as a surgical training tool in general and also for specific otologic procedures. Overall, participants were enthusiastic about incorporation of 3D-printed temporal bones in temporal bone dissection training courses and would recommend them to other trainees. CONCLUSION: 3D-printed temporal bone model is a viable alternative to human cadaveric temporal bones as a teaching tool for otologic surgery.

Refining surgical techniques for efficient posterior semicircular canal gene delivery in the adult mammalian inner ear with minimal hearing loss.

Hearing loss is a common disability affecting the world's population today. While several studies have shown that inner ear gene therapy can be successfully applied to mouse models of hereditary hearing loss to improve hearing, most of these studies rely on inner ear gene delivery in the neonatal age, when mouse inner ear has not fully developed. However, the human inner ear is fully developed at birth. Therefore, in order for inner ear gene therapy to be successfully applied in patients with hearing loss, one must demonstrate that gene delivery can be safely and reliably performed in the mature mammalian inner ear. In this study, we examine the steps involved in posterior semicircular canal gene delivery in the adult mouse inner ear. We find that the duration of perilymphatic leakage and injection rate have a significant effect on the post-surgical hearing outcome. Our results show that although AAV2.7m8 has a lower hair cell transduction rate in adult mice compared to neonatal mice at equivalent viral load, AAV2.7m8 is capable of transducing the adult mouse inner and outer hair cells with high efficiency in a dose-dependent manner.