Cytomegalovirus (CMV) Infection Causes Degeneration of Cochlear Vasculature and Hearing Loss in a Mouse Model

The Effects of Viral Infections on the Molecular and Signaling Pathways Involved in the Development of the PAOs

Cytomegalovirus infection contributes to 10-30% of congenital hearing loss in children. Vertebrate peripheral auditory organs include the outer, middle, and inner ear. Their development is regulated by multiple signaling pathways. However, most ear diseases due to viral infections are due to congenital infections and reactivation and affect healthy adults to a lesser extent. This may be due to the fact that viral infections affect signaling pathways that are important for the development of peripheral hearing organs. Therefore, an in-depth understanding of the relationship between viral infections and the signaling pathways involved in the development of peripheral hearing organs is important for the prevention and treatment of ear diseases. In this review, we summarize the effects of viruses on signaling pathways and signaling molecules in the development of peripheral auditory organs.

Advances in the Study of Etiology and Molecular Mechanisms of Sensorineural Hearing Loss

Sensorineural hearing loss (SNHL), a multifactorial progressive disorder, results from a complex interplay of genetic and environmental factors, with its underlying mechanisms remaining unclear. Several pathological factors are believed to contribute to SNHL, including genetic factors, ion homeostasis, cell apoptosis, immune inflammatory responses, oxidative stress, hormones, metabolic syndrome, human cytomegalovirus infection, mitochondrial damage, and impaired autophagy. These factors collectively interact and play significant roles in the onset and progression of SNHL. The present review offers a comprehensive overview of the various factors that contribute to SNHL, emphasizes recent developments in understanding its etiology, and explores relevant preventive and intervention measures.

The Stria Vascularis: Renewed Attention on a Key Player in Age-Related Hearing Loss

Age-related hearing loss (HL), or presbycusis, is a complex and heterogeneous condition, affecting a significant portion of older adults and involving various interacting mechanisms. Metabolic presbycusis, a type of age-related HL, is characterized by the dysfunction of the stria vascularis, which is crucial for maintaining the endocochlear potential necessary for hearing. Although attention on metabolic presbycusis has waned in recent years, research continues to identify strial pathology as a key factor in age-related HL. This narrative review integrates past and recent research, bridging findings from animal models and human studies, to examine the contributions of the stria vascularis to age-related HL. It provides a brief overview of the structure and function of the stria vascularis and then examines mechanisms contributing to age-related strial dysfunction, including altered ion transport, changes in pigmentation, inflammatory responses, and vascular atrophy. Importantly, this review outlines the contribution of metabolic mechanisms to age-related HL, highlighting areas for future research. It emphasizes the complex interdependence of metabolic and sensorineural mechanisms in the pathology of age-related HL and highlights the importance of animal models in understanding the underlying mechanisms. The comprehensive and mechanistic investigation of all factors contributing to age-related HL, including cochlear metabolic dysfunction, remains crucial to identifying the underlying mechanisms and developing personalized, protective, and restorative treatments.

The Pathogenesis of Cytomegalovirus and Other Viruses Associated with Hearing Loss: Recent Updates

Virus infection is one of the most common etiologies of hearing loss. Hearing loss associated with viral infection can be unilateral or bilateral, mild or severe, sudden or progressive, and permanent or recoverable. Many viruses cause hearing loss in adults and children; however, the pathogenesis of hearing loss caused by viral infection is not fully understood. This review describes cytomegalovirus, the most common virus causing hearing loss, and other reported hearing loss-related viruses. We hope to provide a detailed description of pathogenic characteristics and research progress on pathology, hearing phenotypes, possible associated mechanisms, treatment, and prevention measures. This review aims to provide diagnostic and treatment assistance to clinical workers.

The role of the stria vascularis in neglected otologic disease

The stria vascularis (SV) has been shown to play a critical role in the pathogenesis of many diseases associated with sensorineural hearing loss (SNHL), including age-related hearing loss (ARHL), noise-induced hearing loss (NIHL), hereditary hearing loss (HHL), and drug-induced hearing loss (DIHL), among others. There are a number of other disorders of hearing loss that may be relatively neglected due to being underrecognized, poorly understood, lacking robust diagnostic criteria or effective treatments. A few examples of these diseases include autoimmune inner ear disease (AIED) and/or autoinflammatory inner ear disease (AID), Meniere's disease (MD), sudden sensorineural hearing loss (SSNHL), and cytomegalovirus (CMV)-related hearing loss (CRHL). Although these diseases may often differ in etiology, there have been recent studies that support the involvement of the SV in the pathogenesis of many of these disorders. We strive to highlight a few prominent examples of these frequently neglected otologic diseases and illustrate the relevance of understanding SV composition, structure and function with regards to these disease processes. In this study, we review the physiology of the SV, lay out the importance of these neglected otologic diseases, highlight the current literature regarding the role of the SV in these disorders, and discuss the current strategies, both approved and investigational, for management of these disorders.

Hearing outcomes in children with Congenital Cytomegalovirus: A multi-center, single-enterprise experience

BACKGROUND

Cytomegalovirus (CMV) is the most common cause of non-genetic sensorineural hearing loss (SNHL) in the United States; yet screening for congenital CMV (cCMV) remains controversial. CMV related SNHL can be present at birth, or develop in a delayed manner, and it is a consistent feature in children with either symptomatic or asymptomatic disease. A retrospective chart review was performed to determine the characteristics of patients diagnosed with cCMV and SNHL.

METHODS

The electronic database warehouse of the Nemours Children's Health System (NCHS) was queried from 01/01/2004 to 10/05/2019. ICD 9 (771.1) and ICD 10 (B25.9, P35.1) diagnostic codes were used to identify patients throughout the system with a diagnosis of cCMV infection. Patient demographics including gender, race/ethnicity, age of diagnosis, results of newborn hearing screening (NBHS), detection and progression of hearing loss, presence of antiviral therapy, and frequency of monitoring were collected, and descriptive statistics performed.

RESULTS

Of the 170 patients confirmed to have cCMV, 153 (90%) were symptomatic and 17 (10%) were asymptomatic. CNS involvement (63.5%), radiographic evidence of disease present (69.4%), and SNHL (50.6%) were the most common manifestations of the disease. Of these 170 patients, 83 (48.8%) were determined to have SNHL eligible for evaluation. For these patients with SNHL, the average time of hearing monitoring was 50.6 months. At the time of initial reported detection 63 of 83 (76%) had bilateral hearing loss and 20 (24%) had unilateral loss. Over the study period 3 (15%) progressed from unilateral to bilateral involvement, and 32 (47%) had a deterioration in hearing, with severe to profound SNHL in at least one ear identified at the last visit in 53 (64%) patients. Newborn hearing testing results were available for 69 (83%) of those with hearing loss and 26 patients passed initial testing. However, of the 26 patients who passed, 22 (85%) eventually developed SNHL by their last visit. Within our cohort, females with cCMV were significantly more likely to have SNHL than males with cCMV (62.3% versus 37.6%; p < 0.01).

CONCLUSION

In the absence of targeted or universal cCMV screening, the majority of children identified with this condition present symptomatically. Approximately one half of children with symptomatic cCMV failed NBHS at birth while at least 25% develop SNHL later in life. Children with cCMV are at high risk of delayed onset loss and such children, particularly females, should be monitored closely.

Congenital Nonprofound Bilateral Sensorineural Hearing Loss in Children: Comprehensive Characterization of Auditory Function and Hearing Aid Benefit

A prospective cross-sectional design was used to characterize congenital bilateral sensorineural hearing loss (SNHL). The underlying material of >30,000 consecutively screened newborns comprised 11 subjects with nonprofound, alleged nonsyndromic, SNHL. Comprehensive audiological testing was performed at ≈11 years of age. Results showed symmetrical sigmoid-like median pure-tone thresholds (PTTs) reaching 50−60 dB HL. The congenital SNHL revealed recruitment, increased upward spread of masking, distortion product otoacoustic emission (DPOAE) dependent on PTT (≤60 dB HL), reduced auditory brainstem response (ABR) amplitude, and normal magnetic resonance imaging. Unaided recognition of speech in spatially separate competing speech (SCS) deteriorated with increasing uncomfortable loudness level (UCL), plausibly linked to reduced afferent signals. Most subjects demonstrated hearing aid (HA) benefit in a demanding laboratory listening situation. Questionnaires revealed HA benefit in real-world listening situations. This functional characterization should be important for the outline of clinical guidelines. The distinct relationship between DPOAE and PTT, up to the theoretical limit of cochlear amplification, and the low ABR amplitude remain to be elucidated. The significant relation between UCL and SCS has implications for HA-fitting. The fitting of HAs based on causes, mechanisms, and functional characterization of the SNHL may be an individualized intervention approach and deserves future research.

Emerging Concepts in Congenital Cytomegalovirus

Over a century of research has focused on improving our understanding of congenital cytomegalovirus (cCMV), yet it remains the most common congenital infection in the United States, affecting 3 to 6 per 1000 live born infants each year. Pregnancies affected by cCMV are at a heightened risk of spontaneous abortion and intrauterine fetal demise. Neonates born with cCMV are also at substantial risk for long-term neurodevelopmental sequelae and disability, including sensorineural hearing loss, even those born without clinically apparent disease. Considerable progress has been made in recent years in study of the epidemiology and transmission of cCMV, developing better diagnostic strategies, implementing newborn screening programs, improving therapeutics, and launching vaccine trials. In this article, we review recent developments in the understanding of the virology and immunobiology of cytomegalovirus. We further discuss how this knowledge informs our understanding of the pathophysiology of cCMV and directs strategies aimed at improving outcomes and quality of life for congenitally infected children. We also provide an update on the epidemiology of cCMV in the United States, evolving scientific understanding of maternal-fetal transmission, enhanced screening approaches, and recognition of neonatal and long-term sequelae. Finally, we review the current landscape of pediatric cCMV research and provide recommendations for novel and high-priority areas for future investigation.

CD4 T-cell depletion prevents Lassa fever associated hearing loss in the mouse model

Lassa virus (LASV) is the causative agent of Lassa fever (LF), which presents as a lethal hemorrhagic disease in severe cases. LASV-induced hearing loss in survivors is a huge socioeconomic burden, however, the mechanism(s) leading to hearing loss is unknown. In this study, we evaluate in a mouse LF model the auditory function using auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) to determine the mechanisms underlying LASV-induced hearing loss. In the process, we pioneered measures of ABR and DPOAE tests in rodents in biosafety level 4 (BSL-4) facilities. Our T cell depletion studies demonstrated that CD4 T-cells play an important role in LASV-induced hearing loss, while CD8 T-cells are critical for the pathogenicity in the acute phase of LASV infection. Results presented in this study may help to develop future countermeasures against acute disease and LASV-induced hearing loss.

Congenital Cytomegalovirus Infection and Advances in Murine Models of Neuropathogenesis

•

Congenital human cytomegalovirus (CMV) infection causes severe neuropathogenesis.

•

Murine CMV failed to break through the placental barrier to transmit to fetus.

•

Zhou et al. established a novel mouse system to model congenital HCMV infection.

•

The mouse CMV system by Zhou et al can be used for drug screening.

Change to Hearing Loss-Related Risks and Screening in Preterm Infants

Hearing loss is one of the most common congenital defects in infancy; it increases speech and language delays and adversely affects academic achievement and socialemotional development. The risk of hearing loss in premature infants is higher than that in normal newborns, and because of the fragility of the auditory nervous system, it is more vulnerable to different risk factors. The hearing screening guidelines in current use were proposed by the American Academy of Pediatrics and updated in 2007, but there are no uniform guidelines for hearing screening in preterm infants. This review focuses on the risk factors related to hearing loss in premature infants, hearing screening strategies, and reasons for failure. The aim is to provide a more comprehensive understanding of hearing development in preterm infants to achieve early detection and early intervention. At the same time, attention should be paid to delayed auditory maturation in preterm infants to avoid excessive intervention. KEY POINTS: · Hearing loss is very common in infancy, especially in premature infants.. · Genetic factors, infection, hyperbilirubinemia, drugs, and noise are the main causes.. · We should pay attention to the delayed hearing maturity of premature infants and avoid excessive intervention..

Hearing Instability in Children with Congenital Cytomegalovirus: Evidence and Neural Consequences

OBJECTIVE/HYPOTHESIS

Sensorineural hearing loss (SNHL) is a common sequela of congenital cytomegalovirus (cCMV), potentially exacerbating neurocognitive delay. The objectives of this study were to assess: (1) age at which SNHL in children with cCMV; (2) stimulability of the auditory system in children with cCMV following cochlear implantation (CI); and (3) whether features of magnetic resonance imaging (MRI) potentially are predictive of hearing outcomes.

METHODS

In this retrospective study of a prospectively acquired cohort, 123 children with cCMV who were referred for hearing loss at a single tertiary referral hospital over 20 years were compared with an unmatched comparative group of 90 children with GJB2-related deafness. Outcome measures were results of newborn hearing screening (NHS), behavioral audiograms, and, in a subgroup of cochlear implant (CI) users, responses from the auditory nerve and brainstem evoked by CI at initial activation, as well as lesional volume of FLAIR-hyperintense signal alterations on MRI.

RESULTS

All but 3 of 123 children with cCMV had confirmed and persistent SNHL. At birth, 113 children with cCMV underwent NHS, 31 (27%) passed in both ears and 23 (20%) passed in one ear (no NHS data in 10 children). At the first audiologic assessment, 32 of 123 (26%) had normal hearing bilaterally; 35 of 123 (28%) had unilateral SNHL; and 57 of 123 (46%) had bilateral SNHL. More than half (67 of 123, 54%) experienced hearing deterioration in at least one ear. Survival analyses suggested that 60% of children who developed SNHL did so by 2.5 years and 80% by 5 years. In the children who passed NHS in one or both ears, 50% developed hearing loss by 3.5 years in the ear, which passed unilaterally (n = 23 ears), and 50% by 5 years in bilateral passes (n = 62 ears). Hearing loss was significant enough in all but one child with isolated high-frequency loss for rehabilitation to be indicated. Hearing thresholds in individual ears were in the CI range in 83% (102 of 123), although duration of deafness was sufficient to preclude implantation at our center in 13 children with unilateral SNHL. Hearing aids were indicated in 16% (20 of 123). Responses from the auditory nerve and brainstem to initial CI stimulation were similar in children with cCMV-related SNHL compared with GJB2-related SNHL. Characteristic white matter changes on MRI were seen in all children with cCMV-related SNHL (n = 91), but the lesion volume in each cortical hemisphere did not predict degree of SNHL.

CONCLUSIONS

cCMV-related SNHL is often not detected by NHS but occurs with high prevalence in early childhood. Electrophysiological measures suggest equivalent stimulability of the auditory nerve and brainstem with CI in children with cCMV and GJB2-related SNHL. Hyperintense white matter lesions on FLAIR MRI are consistently present in children with cCMV-related SNHL but cannot be used to predict its time course or degree. Combined, the data show early and rapid deterioration of hearing in children with cCMV-related SNHL with potential for good CI outcomes if SNHL is identified and managed without delay. Findings support universal newborn screening for cCMV followed by careful audiological monitoring.

LEVEL OF EVIDENCE

3 Laryngoscope, 2022.

Hearing Function, Degeneration, and Disease: Spotlight on the Stria Vascularis

The stria vascularis (SV) is a highly vascularized tissue lining the lateral wall of the cochlea. The SV maintains cochlear fluid homeostasis, generating the endocochlear potential that is required for sound transduction. In addition, the SV acts as an important blood-labyrinth barrier, tightly regulating the passage of molecules from the blood into the cochlea. A healthy SV is therefore vital for hearing function. Degeneration of the SV is a leading cause of age-related hearing loss, and has been associated with several hearing disorders, including Norrie disease, Meniere's disease, Alport syndrome, Waardenburg syndrome, and Cytomegalovirus-induced hearing loss. Despite the SV's important role in hearing, there is still much that remains to be discovered, including cell-specific function within the SV, mechanisms of SV degeneration, and potential protective or regenerative therapies. In this review, we discuss recent discoveries elucidating the molecular regulatory networks of SV function, mechanisms underlying degeneration of the SV, and otoprotective strategies for preventing drug-induced SV damage. We also highlight recent clinical developments for treating SV-related hearing loss and discuss future research trajectories in the field.

Labyrinthine lesions in presumed inner ear hemorrhage-related sudden deafness

PURPOSE

Inner ear hemorrhage (IEH) is a rare cause of sudden sensorineural hearing loss (SSNHL). This study aimed to evaluate the lesional patterns in patients with presumed IEH from morphological and functional aspects.

METHODS

Seventeen patients with SSNHL and presumed IEH who completed audio-vestibular tests were included. The main outcome measures included clinical characteristics, radiology, and functional test results.

RESULTS

The morphological findings and functional tests revealed differences in locations and lesional spectrums. The magnetic resonance imaging (MRI) hyperintensity was likely to involve the vestibule (88.2%), the cochlea (76.5%), and the posterior and lateral semicircular canals (76.5% and 70.6%, respectively). Furthermore, 70.6% of cases showed abnormality in the entire labyrinth, and abnormalities in the vestibule/semicircular canals were observed in 17.6% of cases. Meanwhile, dysfunction was sequentially detected in the cochlea (100%), semicircular canals (94.1%), and vestibule (70.6%); 64.7% of cases showed combined deficit in the entire labyrinth, and 29.4% of cases showed combined deficit in the cochlea/semicircular canals. Although lesions in the labyrinth were frequently detected, the results of the radiological and functional tests did not always match and significantly differed in either cochlear or superior semicircular canal damage detection (p < 0.05 each).

CONCLUSIONS

In this cohort, IEH preferentially caused sudden audio-vestibular impairment, which was well demonstrated by a combination of MRI and functional tests. The specific lesional configurations revealed in this study may suggest a possible pathomechanism that could be further explored as a therapeutic target.

Cytomegalovirus Seropositivity as a Potential Risk Factor for Increased Noise Trauma Susceptibility

CONTEXT

Cytomegalovirus (CMV) represents the leading congenital viral infection in humans. Although congenital CMV due to vertically transmitted infections is the main cause of CMV-related diseases, adult CMV infections might still be of clinical significance. It is still discussed how far CMV seropositivity, due to horizontal infection in immunocompetent adults, is able to induce significant dysfunction. The present study investigates in how far CMV seropositivity is an additional risk factor for an increasing susceptibility to sensorineural hearing loss induced by acoustic injury during adulthood in a guinea pig CMV (GPCMV) model of noise-induced hearing loss (NIHL).

METHODS

Two groups (GPCMV seropositive vs. seronegative) of normal hearing adult guinea pigs were exposed to a broadband noise (5-20 kHz) for 2 hours at 115 dB sound pressure level. Frequency-specific auditory brainstem response recordings for determination of auditory threshold shift were carried out and the number of missing outer hair cells was counted 2 weeks after the noise exposure.

RESULTS

The data show a slightly increased shift in auditory thresholds in seropositive animals compared to the seronegative control group in response to noise trauma. However, the observed difference was significant at least at high frequencies. The differences in threshold shift are not correlated with outer hair cell loss between the experimental groups.

CONCLUSION

The results point to potential additional pathologies in a guinea pig NIHL model in correlation to GPCMV seropositivity, which should be taken into account when assessing risks of latent/reactivated CMV infection. Due to the relatively slight effect in the present data, the aim of future studies should be a more detailed consideration (e.g., larger sample size) and to localize possible target structures as well as the significance of the infection route.

Early Life Inflammation and the Developing Hematopoietic and Immune Systems: The Cochlea as a Sensitive Indicator of Disruption

Emerging evidence indicates that perinatal infection and inflammation can influence the developing immune system and may ultimately affect long-term health and disease outcomes in offspring by perturbing tissue and immune homeostasis. We posit that perinatal inflammation influences immune outcomes in offspring by perturbing (1) the development and function of fetal-derived immune cells that regulate tissue development and homeostasis, and (2) the establishment and function of developing hematopoietic stem cells (HSCs) that continually generate immune cells across the lifespan. To disentangle the complexities of these interlinked systems, we propose the cochlea as an ideal model tissue to investigate how perinatal infection affects immune, tissue, and stem cell development. The cochlea contains complex tissue architecture and a rich immune milieu that is established during early life. A wide range of congenital infections cause cochlea dysfunction and sensorineural hearing loss (SNHL), likely attributable to early life inflammation. Furthermore, we show that both immune cells and bone marrow hematopoietic progenitors can be simultaneously analyzed within neonatal cochlear samples. Future work investigating the pathogenesis of SNHL in the context of congenital infection will therefore provide critical information on how perinatal inflammation drives disease susceptibility in offspring.

Role of the Stria Vascularis in the Pathogenesis of Sensorineural Hearing Loss: A Narrative Review

Sensorineural hearing loss is a common sensory impairment in humans caused by abnormalities in the inner ear. The stria vascularis is regarded as a major cochlear structure that can independently degenerate and influence the degree of hearing loss. This review summarizes the current literature on the role of the stria vascularis in the pathogenesis of sensorineural hearing loss resulting from different etiologies, focusing on both molecular events and signaling pathways, and further attempts to explore the underlying mechanisms at the cellular and molecular biological levels. In addition, the deficiencies and limitations of this field are discussed. With the rapid progress in scientific technology, new opportunities are arising to fully understand the role of the stria vascularis in the pathogenesis of sensorineural hearing loss, which, in the future, will hopefully lead to the prevention, early diagnosis, and improved treatment of sensorineural hearing loss.

Association between Congenital Cytomegalovirus Infection and Brain Injury in Neonates: A Meta-analysis of Cohort Studies

Objective

To assess association between congenital cytomegalovirus (CMV) infection and brain injury in neonates.

Methods

The literatures from inception to November 4, 2020, were searched through PubMed, Embase, Cochrane Library, and Web of Science. Heterogeneity test was conducted for each indicator and measured by I ² statistics. If I ² ≥ 50%, the random effects model was applied; otherwise, the fixed effects model was used. Sensitivity analysis was performed for all models. Weighed mean difference (WMD) was used as the effect size for measurement data, and risk ratio (RR) was as the effect indicator.

Results

A total of 13 studies, including 4,262 congenital CMV infection neonates, were enrolled in this study. Our results showed that the rate of hearing impairment (RR: 2.105, 95% CI: (1.115, 3.971), P = 0.002), sensorineural hearing loss (SNHL) (RR: 17.051, 95% CI: (6.201, 46.886), P < 0.001), and microcephaly (RR: 2.283, 95% CI: (1.325, 3.935), P =0.003) in neonates infected congenital CMV was higher than that in control group.

Conclusion

The risks of hearing impairment, SNHL, and microcephaly in neonates during childhood may be associated with congenital CMV infection. It is necessary to establish neonatal screening programs and comprehensive diagnostic tests for patients to reduce the risk of adverse brain damage to the congenital CMV infection as early as possible and to improve the prognosis of the newborn.

Hierarchical imaging and computational analysis of three-dimensional vascular network architecture in the entire postnatal and adult mouse brain

The formation of new blood vessels and the establishment of vascular networks are crucial during brain development, in the adult healthy brain, as well as in various diseases of the central nervous system. Here, we describe a step-by-step protocol for our recently developed method that enables hierarchical imaging and computational analysis of vascular networks in postnatal and adult mouse brains. The different stages of the procedure include resin-based vascular corrosion casting, scanning electron microscopy, synchrotron radiation and desktop microcomputed tomography imaging, and computational network analysis. Combining these methods enables detailed visualization and quantification of the 3D brain vasculature. Network features such as vascular volume fraction, branch point density, vessel diameter, length, tortuosity and directionality as well as extravascular distance can be obtained at any developmental stage from the early postnatal to the adult brain. This approach can be used to provide a detailed morphological atlas of the entire mouse brain vasculature at both the postnatal and the adult stage of development. Our protocol allows the characterization of brain vascular networks separately for capillaries and noncapillaries. The entire protocol, from mouse perfusion to vessel network analysis, takes ~10 d.

Murine Models of Central Nervous System Disease following Congenital Human Cytomegalovirus Infections

Human cytomegalovirus infection of the developing fetus is a leading cause of neurodevelopmental disorders in infants and children, leading to long-term neurological sequela in a significant number of infected children. Current understanding of the neuropathogenesis of this intrauterine infection is limited because of the complexity of this infection, which includes maternal immunological responses that are overlaid on virus replication in the CNS during neurodevelopment. Furthermore, available data from human cases are observational, and tissues from autopsy studies have been derived from only the most severe infections. Animal models of this human infection are also limited by the strict species specificity of cytomegaloviruses. However, informative models including non-human primates and small animal models have been developed. These include several different murine models of congenital HCMV infection for the study of CMV neuropathogenesis. Although individual murine models do not completely recapitulate all aspects of the human infection, each model has provided significant information that has extended current understanding of the neuropathogenesis of this human infection. This review will compare and contrast different murine models in the context of available information from human studies of CNS disease following congenital HCMV infections.

Congenital Deafness and Recent Advances Towards Restoring Hearing Loss

Congenital hearing loss is the most common birth defect, estimated to affect 2-3 in every 1000 births. Currently there is no cure for hearing loss. Treatment options are limited to hearing aids for mild and moderate cases, and cochlear implants for severe and profound hearing loss. Here we provide a literature overview of the environmental and genetic causes of congenital hearing loss, common animal models and methods used for hearing research, as well as recent advances towards developing therapies to treat congenital deafness. © 2021 The Authors.

VEGFA165 gene therapy ameliorates blood-labyrinth barrier breakdown and hearing loss

Millions of people are affected by hearing loss. Hearing loss is frequently caused by noise or aging and often associated with loss of pericytes. Pericytes populate the small vessels in the adult cochlea. However, their role in different types of hearing loss is largely unknown. Using an inducible and conditional pericyte depletion mouse model and noise-exposed mouse model, we show that loss of pericytes leads to marked changes in vascular structure, in turn leading to vascular degeneration and hearing loss. In vitro, using advanced tissue explants from pericyte fluorescence reporter models combined with exogenous donor pericytes, we show that pericytes, signaled by VEGF isoform A165 (VEGFA165), vigorously drive new vessel growth in both adult and neonatal mouse inner ear tissue. In vivo, the delivery of an adeno-associated virus serotype 1-mediated (AAV1-mediated) VEGFA165 viral vector to pericyte-depleted or noise-exposed animals prevented and regenerated lost pericytes, improved blood supply, and attenuated hearing loss. These studies provide the first clear-cut evidence that pericytes are critical for vascular regeneration, vascular stability, and hearing in adults. The restoration of vascular function in the damaged cochlea, including in noise-exposed animals, suggests that VEGFA165 gene therapy could be a new strategy for ameliorating vascular associated hearing disorders.

Congenital Human Cytomegalovirus Infection Inducing Sensorineural Hearing Loss

Human cytomegalovirus (HCMV) is the primary cause of congenital infections. Despite its clinical significance, congenital HCMV infection is frequently overlooked clinically since most affected infants are asymptomatic. Sensorineural hearing loss (SNHL) is one of the most widely known disorders caused by congenital HCMV infection. The potential mechanism, however, remains unknown to date. The mechanism by which congenital HCMV infection induces sensorineural deafness has been partly characterized, leading to advancements in diagnosis, therapy, and prevention strategies. HCMV-induced hearing loss primarily involves immune responses, the release of inflammatory factors by natural killer (NK) cells, apoptosis of cochlear spiral ganglion, and potential changes due to vascular dysfunction. The diagnosis of HCMV induced SNHL includes serological examination to mothers, imaging, and amniotic fluid examination. Ganciclovir, mainly used for antiviral therapy and behavioral prevention, can, to some degree, prevent congenital HCMV infection. The role of HCMV infection in hearing loss needs further investigation since the mechanism of hearing loss caused by cytomegalovirus infection is not well understood. Although some advancement has been made in diagnosing and treating SNHL, more improvement is needed. A comprehensive understanding of cytomegalovirus’s pathogenesis is of key importance for preventing, diagnosing, and treating SNHL.

Hearing Loss Caused by HCMV Infection through Regulating the Wnt and Notch Signaling Pathways

Hearing loss is one of the most prevalent sensory disabilities worldwide with huge social and economic burdens. The leading cause of sensorineural hearing loss (SNHL) in children is congenital cytomegalovirus (CMV) infection. Though the implementation of universal screening and early intervention such as antiviral or anti-inflammatory ameliorate the severity of CMV-associated diseases, direct and targeted therapeutics is still seriously lacking. The major hurdle for it is that the mechanism of CMV induced SNHL has not yet been well understood. In this review, we focus on the impact of CMV infection on the key players in inner ear development including the Wnt and Notch signaling pathways. Investigations on these interactions may gain new insights into viral pathogenesis and reveal novel targets for therapy.

Rodent Models of Congenital Cytomegalovirus Infection

Human cytomegalovirus (HCMV) is a leading viral cause of congenital infections in the central nervous system (CNS) and may result in severe long-term sequelae. High rates of sequelae following congenital HCMV infection and insufficient antiviral therapy in the perinatal period makes the development of an HCMV-specific vaccine a high priority of modern medicine. Due to the species specificity of HCMV, animal models are frequently used to study CMV pathogenesis. Studies of murine cytomegalovirus (MCMV) infections of adult mice have played a significant role as a model of CMV biology and pathogenesis, while MCMV infection of newborn mice has been successfully used as a model of perinatal CMV infection. Newborn mice infected with MCMV have high levels of viremia during which the virus establishes a productive infection in most organs, coupled with a robust inflammatory response. Productive infection in the brain parenchyma during early postnatal period leads to an extensive nonnecrotizing multifocal widespread encephalitis characterized by infiltration of components of both innate and adaptive immunity. As a result, impairment in postnatal development of mouse cerebellum leads to long-term motor and sensor disabilities. This chapter summarizes current findings of rodent models of perinatal CMV infection and describes methods for analysis of perinatal MCMV infection in newborn mice.

Ultrasonic bone removal from the ossicular chain affects cochlear structure and function

INTRODUCTION

Ultrasonic bone removal devices (UBD) are capable of cutting through bony tissue without injury to adjacent soft tissue. The feasibility and safety of using this technology for removal of bone from an intact ossicular chain (as might be required for otosclerosis or congenital fixation) was investigated in an animal model.

METHODS

This was a prospective animal study conducted on seven anesthetised adult chinchillas. An UBD was used to remove bone from the malleus head in situ. Pre and post-operative distortion product otoacoustic emission (DPOAE) levels and auditory brainstem response (ABR) thresholds were recorded. Scanning electron microscopy (SEM) was used to assess cochlear haircell integrity.

RESULTS

Precise removal of a small quantity of bone from the malleus head was achieved by a 30s application of UBD without disruption of the ossicular chain or tympanic membrane. DPOAEs became undetectable after the intervention with signal-to-noise ratios (SNR) < 5 dB SPL in all ears. Furthermore, ABR thresholds were elevated > 85 dB SPL in 13 ears. SEM showed significant disruption of structural integrity of the organ of Corti, specifically loss and damage of outer haircells.

CONCLUSIONS

Although UBD can be used to reshape an ossicle without middle ear injury, prolonged contact with the ossicular chain can cause structural and functional injury to the cochlea. Extensive cochlea pathology was found, but we did not investigate for recovery from any temporary threshold shift. In the authors' opinion, further study should be undertaken before consideration is given to use of the device for release of ossicular fixation.

Airborne Aerosolized Mouse Cytomegalovirus From Common Otolaryngology Procedures: Implications for COVID-19 Infection

OBJECTIVES

To determine whether common otolaryngology procedures generate viable aerosolized virus through a murine cytomegalovirus (mCMV) model for infection.

STUDY DESIGN

mCMV model of infection.

SETTING

University of Utah laboratory.

METHODS

Three-day-old BALB/c mice were inoculated with mCMV or saline. Five days later, each mouse underwent drilling, microdebrider, coblation, and electrocautery procedures. Particle size distribution and PM2.5 (particulate matter <2.5 µm) concentration were determined with a scanning mobility particle sizer and an aerosol particle sizer in the range of 15 nm to 32 µm. Aerosolized samples from these procedures were collected with an Aerosol Devices BioSpot sampler for viral titer based on polymerase chain reaction and for viable virus through viral culture.

RESULTS

As compared with the background aerosol concentrations, coblation and electrocautery showed statistically significant increases in airborne aerosols (Tukey-adjusted P value <.040), while microdebrider and drilling at 30,000 rpm did not (.870 < Tukey-adjusted P value < .930). We identified viral DNA in samples from coblation and drilling procedures, although we did not identify viable viruses in aerosol samples from any of the 4 procedures.

CONCLUSION

Coblation and electrocautery procedures generate >100-fold increases in aerosol concentrations over background; only coblation and drilling produce aerosolized viral DNA. The high concentration of aerosols from coblation and electrocautery suggests the need for appropriate safeguards against particle exposure to health care workers. The presence of viral DNA from drilling and coblation procedures warrants the need for appropriate protection against droplet and aerosol exposure.

Identical twins affected by congenital cytomegalovirus infections showed different audio-vestibular profiles

This study explored whether there were long‐term hearing and vestibular outcome differences between five pairs of identical twins who had been infected with the congenital cytomegalovirus (CMV) infection before birth. Data were collected from the medical records at the Audiological Clinic, Karolinska University Hospital, Stockholm. The congenital CMV infection resulted in high variations in vestibular and hearing function within, and between, the genetically identical twin pairs. Clinicians need to be aware that treatment and interventions may need to differ substantially when identical twins have hearing issues related to the congenital CMV infection.

A Systematic Review on the Association of Acquired Human Cytomegalovirus Infection with Hearing Loss

Congenital cytomegalovirus (CMV) infection induces a clinical syndrome usually associated with hearing loss. However, the effect of acquired CVM infection in adults and children has not been clearly defined. The objective of this review is to critically appraise scientific evidence regarding the association of acquired CMV infection with postnatal hearing loss or tinnitus. A systematic review of records reporting sensorineural hearing loss (SNHL) or tinnitus and acquired CMV infection including articles published in English was performed. Search strategy was limited to human studies with acquired CMV infection. After screening and quality assessment, nine studies involving 1528 individuals fulfilled the inclusion criteria. A total of 14% of patients with SNHL showed evidence of previous exposure to CMV, while in individuals without SNHL (controls) the percentage rose up to 19.3%. SNHL was reported as unilateral or bilateral in 15.3%, and not specified in 84.7% of cases. The degree of SNHL ranged from mild to profound for both children and adults. None of the records reported tinnitus. The prevalence of children or adults with acquired SNHL with a confirmed acquired CMV infection by Polymerase Chain Reaction (PCR) or IgM anti-CMV antibodies is low. Phenotyping of patients with acquired CMV infection was limited to hearing loss by pure tone audiometry and no additional audiological testing was performed in most of the studies. Additional symptoms deserve more attention, including episodic vertigo or tinnitus, since some patients with the clinical spectrum of Meniere Disease could result from a CMV latent infection.

Advances in Inner Ear Therapeutics for Hearing Loss in Children

Purpose of review

Hearing loss is a common congenital sensory disorder with various underlying causes. Here, we review and focus on genetic, infectious, and ototoxic causes and recent advances in inner ear therapeutics.

Recent findings

While hearing aids and cochlear implantation are the mainstay of treatment for pediatric hearing loss, novel biological therapeutics are being explored. Recent preclinical studies report positive results in viral-mediated gene transfer techniques and surgical approaches to the inner ear for genetic hearing loss. Novel pharmacologic agents, on the other hand, show promising results in reducing aminoglycoside and cisplatin ototoxicity. Clinical trials are underway to evaluate the efficacy of antivirals for cytomegalovirus-related hearing loss, and its pathogenesis and other potential therapeutics are currently under investigation.

Summary

Individualized therapies for genetic and infectious causes of sensorineural hearing loss in animal models as well as pediatric patients show promising results, with their potential efficacy being active areas of research.

Modiolar Proximity of Slim Modiolar Electrodes and Cochlear Duct Length: Correlation for Potential Basis of Customized Cochlear Implantation With Perimodiolar Electrodes

OBJECTIVES

Recent studies have shown that cochlear duct length (CDL) varies among individuals and could significantly influence the final position of the electrode and its trajectory in the cochlea. Given this, we hypothesized that the degree of modiolar proximity of novel slim modiolar electrodes, such as CI532 and CI632, can also be affected by CDL. To test this hypothesis, we retrospectively evaluated individual CDL to determine if there is any significant correlation of CDL with degree of modiolar proximity.

METHODS

Fifty-one ears from 38 subjects implanted with slim modiolar electrodes by a single surgeon through the round window approach using the pull-back technique were included. Our cohort was classified according to the deafness onset (congenital versus postlingual) and the degree of modiolar proximity (less versus tight) with reference to the spiral diameter made by the slim modiolar electrodes in situ on transorbital x ray. We then analyzed the CDL and its metrics using a readily available surgical preplanning tool (OTOPLAN) to obtain comparable data.

RESULTS

Among 30 ears associated with congenital deafness, 9 ears (30%) showed less modiolar proximity, while none of the 21 ears from 19 subjects with postlingual deafness exhibited "less modiolar proximity" based on our criteria. In this study, CDL showed significant variation among subjects. Importantly, a significant inverse correlation between spiral diameter and CDL (ρ = -0.581, p < 0.001) was found, showing that shorter CDLs have longer spiral diameter and less modiolar proximity. Moreover, further pull-back technique characterized by pulling out the electrode a little bit more in cases with shorter CDL, if not always, exhibited tighter modiolar proximity.

CONCLUSION

A preponderance of less modiolar proximity of the electrode was observed exclusively among congenital deafness cases, demonstrated by a less tight spiral configuration even under the pull-back technique. Our data suggest that shorter CDL is associated with a less tight spiral configuration of slim modiolar electrodes postoperatively. Depending on the insertion technique, the differential degree of modiolar proximity of slim modiolar electrodes can be alleviated in cases with short CDL, which justifies cochlear duct length-based customized insertion of slim modiolar electrodes.

Zika virus infection causes widespread damage to the inner ear

Zika virus (ZIKV) has been recently recognized as a causative agent of newborn microcephaly, as well as other neurological consequences. A less well recognized comorbidity of prenatal ZIKV infection is hearing loss, but cases of hearing impairment following adult ZIKV infection have also been recognized. Diminished hearing following prenatal ZIKV infection in a mouse model has been reported, but no cellular consequences were observed. We examined the effects of ZIKV infection on inner ear cellular integrity and expression levels of various proteins important for cochlear function in type I interferon receptor null (Ifnar1^-/-) mice following infection at 5-6 weeks of age. We show that ZIKV antigens are present in cells within the cochlear epithelium, lateral wall, spiral limbus and spiral ganglion. Here we show that ZIKV infection alters cochlear expression of genes that signal cell damage (S100B), transport fluids (AQP1), are gaseous transmitters (eNOs) and modulate immune response (F4/80). Morphological analyses shows that not only are cochlear structures compromised by ZIKV infection, but damage also occurs in vestibular end organs. ZIKV produces a graded distribution of cellular damage in the cochlea, with greatest damage in the apex similar to that reported for cytomegalovirus (CMV) infection. The graded distribution of damage may indicate a differential susceptibility to ZIKV along the cochlear tonotopic axis. Collectively, these data are the first to show the molecular and morphological damage to the inner ear induced by ZIKV infection in adults and suggests multiple mechanisms contributing to the hearing loss reported in the human population.

Virus-induced cochlear inflammation in newborn mice alters auditory function

Although human cytomegalovirus (HCMV) is a known cause of sensorineural hearing loss in infants with congenital HCMV (cCMV) infections, mechanisms that contribute to sensorineural hearing loss (SNHL) in infants with cCMV infection are not well defined. Using a murine model of CMV infection during auditory development, we have shown that peripheral infection of newborn mice with murine CMV (MCMV) results in focal infection of the cochlea and virus-induced cochlear inflammation. Approximately 50%-60% of infected mice exhibited increased auditory brainstem response (ABR) thresholds across a range of sound frequencies. Histological analyses of the cochlea in MCMV-infected mice with elevated ABR thresholds revealed preservation of hair cell (HC) number and morphology in the organ of Corti. In contrast, the number of spiral ganglion neurons (SGN), synapses, and neurites connecting the cochlear HC and SGN nerve terminals were decreased. Decreasing cochlear inflammation by corticosteroid treatment of MCMV-infected mice resulted in preservation of SGN and improved auditory function. These findings show that virus-induced cochlear inflammation during early auditory development, rather than direct virus-mediated damage, could contribute to histopathology in the cochlea and altered auditory function without significant loss of HCs in the sensory epithelium.

Prediction of the Outcome of Cochlear Implantation in the Patients with Congenital Cytomegalovirus Infection based on Magnetic Resonance Imaging Characteristics

The goal of this study was to elucidate radiologic biomarker that can predict the outcome of cochlear implantation (CI) in congenital cytomegalovirus (cCMV) related deafness. A retrospective survey of speech perception after CI and an evaluation of brain magnetic resonance imaging (MRI) findings were performed in 10 cochlear implantees with cCMV-related prelingual deafness. Specifically, a special attention was paid to the degree of white matter (WM) abnormality shown in brain MRI, which was used to divide our cohort into two groups: The mild and severe pathology groups. Age-matched prelingual deaf patients with idiopathic sensorineural hearing loss were selected as controls. Subjects in mild pathology groups showed higher a Category of Auditory Performance (CAP) score (5.2 ± 0.8) than those with severe pathologies (3.4 ± 1.5) (P = 0.041). Importantly, speech performance from subjects with mild pathology was comparable to that of the control group (mean CAP score of 5.2 ± 0.8 vs. 5.1 ± 1.2) (P = 0.898). Mild pathologies related to the limited WM lesion in MRI not accompanied by severe MRI pathologies, such as diffuse WM abnormality, myelination delay, ventriculomegaly, migration abnormality, and cerebellar hypoplasia, can be tolerated and do not adversely affect the CI outcome in cCMV deafness.

Cochlear Implants and Children with Vestibular Impairments

Sensorineural hearing loss (SNHL) in children occurs in 1 to 3% of live births and acquired hearing loss can additionally occur. This sensory deficit has far reaching consequences that have been shown to extend beyond speech and language development. Thankfully there are many therapeutic options that exist for these children with the aim of decreasing the morbidity of their hearing impairment. Of late, focus has shifted beyond speech and language outcomes to the overall performance of children with SNHL in real-world environments. To account for their residual deficits in such environments, clinicians must understand the extent of their sensory impairments. SNHL commonly coexists with other sensory deficits such as vestibular loss. Vestibular impairment is exceedingly common in children with SNHL with nearly half of children exhibiting vestibular end-organ dysfunction. These deficits naturally lead to impairments in balance and delay in motor milestones. However, this additional sensory deficit likely leads to further impairment in the performance of these children. This article focuses on the following: 1. Defining the coexistence of vestibular impairment in children with SNHL and cochlear implants. 2. Describing screening methods aimed at identifying vestibular dysfunction in children with SNHL. 3. Understanding the functional implications of this dual-sensory impairment. 4. Exploring possible rehabilitative strategies to minimize the impact of vestibular impairment in children with SNHL.

Lassa fever-induced sensorineural hearing loss: A neglected public health and social burden

Although an association between Lassa fever (LF) and sudden-onset sensorineural hearing loss (SNHL) was confirmed clinically in 1990, the prevalence of LF-induced SNHL in endemic countries is still underestimated. LF, a viral hemorrhagic fever disease caused by Lassa virus (LASV), is endemic in West Africa, causing an estimated 500,000 cases and 5,000 deaths per year. Sudden-onset SNHL, one complication of LF, occurs in approximately one-third of survivors and constitutes a neglected public health and social burden. In the endemic countries, where access to hearing aids is limited, SNHL results in a decline of the quality of life for those affected. In addition, hearing loss costs Nigeria approximately 43 million dollars per year. The epidemiology of LF-induced SNHL has not been characterized well. The complication of LF induced by SNHL is also an important consideration for vaccine development and treatments. However, research into the mechanism has been hindered by the lack of autopsy samples and relevant small animal models. Recently, the first animal model that mimics the symptoms of SNHL associated with LF was developed. Preliminary data from the new animal model as well as the clinical case studies support the mechanism of immune-mediated injury that causes SNHL in LF patients. This article summarizes clinical findings of hearing loss in LF patients highlighting the association between LASV infection and SNHL as well as the potential mechanism(s) for LF-induced SNHL. Further research is necessary to identify the mechanism and the epidemiology of LF-induced SNHL.

Evaluation and management of cytomegalovirus-associated congenital hearing loss

PURPOSE OF REVIEW

The current article reviews the current literature related to congenital cytomegalovirus (CMV)-related hearing loss. The discussion will focus on the epidemiology, pathogenesis, and clinical presentation of human CMV infection as it pertains to hearing loss. Current methods of CMV diagnosis with a focus on the evolving trend toward broader neonatal screening protocols will also be explored. Discussion of medical, surgical, and audiologic management of the condition will also be addressed.

RECENT FINDINGS

Much of the current research on this topic is focused on improving detection of CMV through screening programs. Some advances in understanding cochlear pathogenesis have also been made.

SUMMARY

Congenital CMV infection remains an important cause of hearing loss in infants and children. Early detection of CMV infection can broaden treatment options and allow for improved hearing and language outcome for patients with CMV-associated sensorineural hearing loss.