Radiopathologic predictors of 1- and 2-year frontal sinusotomy outcomes in a southeast Asian chronic rhinosinusitis population.

BACKGROUND: The frontal sinus and its drainage pathway are difficult spaces to navigate surgically. The complexity of the frontal recess anatomy as well as inflammatory factors may influence outcomes of endoscopic frontal sinusotomy. It is not clear which factors are more important in determining post-operative frontal ostium patency. OBJECTIVE: The objective is to investigate whether the distribution of fronto-ethmoidal cells, frontal recess dimensions and sinonasal inflammation predict frontal ostium patency at 1- and 2-years after endoscopic frontal sinusotomy. METHODS: A retrospective review of 94 chronic rhinosinusitis patients (185 sides) who had undergone endoscopic frontal sinusotomies between 2015 and 2019 was conducted. Computed tomography was used to evaluate the type of fronto-ethmoidal cells present and determine the dimensions of the frontal recess. The International Classification of the Radiological Complexity of frontal recess and frontal sinus was used to grade the complexity of frontal recess anatomy. Mucosal inflammation was graded according to a structured histopathology report. Frontal ostium patency at 1- and 2-years post-operatively was recorded. RESULTS: The frontal ostium patency rates were 80.9% and 73.4% at 1- and 2-years respectively. Eosinophilic predominance (adjusted OR 3.5, 95% CI 1.6-8.0, p = 0.003) and mucosal ulceration on histology (adjusted OR 4.5, 95% CI 1.1-17.9, p = 0.033) predicted ostial stenosis at 1 year. Smoking (adjusted OR 7.6, 95% CI 2.4-24.7, p = 0.001), aspirin exacerbated respiratory disease (AERD) (adjusted OR 7.6, 95% CI 1.9-30.1, p = 0.004) and histological findings of severe inflammation (adjusted OR 8.9, 95% CI 1.9-41.2, p = 0.005) were independent predictors of ostial stenosis at 2 years. Frontal cell patterns, frontal recess dimensions and frontal recess complexity did not predict frontal ostium stenosis at both 1- and 2-years post-operatively. CONCLUSION: Post-operative control of sinonasal inflammation is important in maintaining frontal ostium patency, regardless of frontal cell patterns or frontal recess dimensions.

Infection of human Nasal Epithelial Cells with SARS-CoV-2 and a 382-nt deletion isolate lacking ORF8 reveals similar viral kinetics and host transcriptional profiles.

The novel coronavirus SARS-CoV-2 is the causative agent of Coronavirus Disease 2019 (COVID-19), a global healthcare and economic catastrophe. Understanding of the host immune response to SARS-CoV-2 is still in its infancy. A 382-nt deletion strain lacking ORF8 (Δ382 herein) was isolated in Singapore in March 2020. Infection with Δ382 was associated with less severe disease in patients, compared to infection with wild-type SARS-CoV-2. Here, we established Nasal Epithelial cells (NECs) differentiated from healthy nasal-tissue derived stem cells as a suitable model for the ex-vivo study of SARS-CoV-2 mediated pathogenesis. Infection of NECs with either SARS-CoV-2 or Δ382 resulted in virus particles released exclusively from the apical side, with similar replication kinetics. Screening of a panel of 49 cytokines for basolateral secretion from infected NECs identified CXCL10 as the only cytokine significantly induced upon infection, at comparable levels in both wild-type and Δ382 infected cells. Transcriptome analysis revealed the temporal up-regulation of distinct gene subsets during infection, with anti-viral signaling pathways only detected at late time-points (72 hours post-infection, hpi). This immune response to SARS-CoV-2 was significantly attenuated when compared to infection with an influenza strain, H3N2, which elicited an inflammatory response within 8 hpi, and a greater magnitude of anti-viral gene up-regulation at late time-points. Remarkably, Δ382 induced a host transcriptional response nearly identical to that of wild-type SARS-CoV-2 at every post-infection time-point examined. In accordance with previous results, Δ382 infected cells showed an absence of transcripts mapping to ORF8, and conserved expression of other SARS-CoV-2 genes. Our findings shed light on the airway epithelial response to SARS-CoV-2 infection, and demonstrate a non-essential role for ORF8 in modulating host gene expression and cytokine production from infected cells.

Transcriptomics of rhinovirus persistence reveals sustained expression of RIG-I and interferon-stimulated genes in nasal epithelial cells in vitro.

BACKGROUND: Human rhinoviruses (HRVs) are frequently associated with asthma exacerbations, and have been found in the airways of asthmatic patients. While HRV-induced acute infection is well-documented, it is less clear whether the nasal epithelium sustains prolonged HRV infections along with the associated activation of host immune responses. OBJECTIVE: To investigate sustainably regulated host responses of human nasal epithelial cells (hNECs) during HRV persistence. METHODS: Using a time-course study, HRV16 persistence and viral replication dynamics were established using an in vitro infection model of hNECs. RNA sequencing was performed on hNECs in the early and late stages of infection at 3 and 14 days post-infection (dpi), respectively. The functional enrichment of differentially expressed genes (DEGs) was evaluated using gene ontology (GO) and Ingenuity pathway analysis. RESULTS: HRV RNA and protein expression persisted throughout prolonged infections, even after decreased production of infectious virus progeny. GO analysis of unique DEGs indicated altered regulation of pathways related to ciliary function and airway remodeling at 3 dpi and serine-type endopeptidase activity at 14 dpi. The functional enrichment of shared DEGs between the two time-points was related to interferon (IFN) and cytoplasmic pattern recognition receptor (PRR) signaling pathways. Validation of the sustained regulation of candidate genes confirmed the persistent expression of RIG-I and revealed its close co-regulation with interferon-stimulated genes (ISGs) during HRV persistence. CONCLUSIONS: The persistence of HRV RNA does not necessarily indicate an active infection during prolonged infection. The sustained expression of RIG-I and ISGs in response to viral RNA persistence highlights the importance of assessing how immune-activating host factors can change during active HRV infection and the immune regulation that persists thereafter.

Precision Medicine in Chronic Rhinosinusitis: Where Does Allergy Fit In?

Chronic rhinosinusitis (CRS) is a clinical syndrome stemming from persistent inflammation of the sinonasal mucosa. Phenotypically, it is traditionally and widely described according to the presence or absence of polyps. While this distinction is simple to use, it has little bearing on prognosis and treatment, for CRS is essentially an inflammatory disease resulting from dysregulated interaction between a multitude of host and environmental factors. Allergy is merely one of them and, like many of the proposed aetiologies, has been subject to much debate which will be discussed here. As our understanding of CRS continues to evolve, previous so-called conventional wisdom about phenotypes (e.g. CRS with nasal polyps is associated with Type 2 inflammation) is being challenged, and new phenotypes are also emerging. In addition, there is growing interest in defining the endotypes of CRS to deliver precise and personalised treatment, especially pertaining to the development of biologics for the group of severe, difficult-to-treat CRS patients. A proposed model of precision medicine tailored to management of CRS will also be introduced to readers, which can be continually modified to adapt to new discoveries about this exciting condition.

Endovascular embolisation of external carotid artery system haemorrhage in radiated nasopharyngeal carcinoma.

PURPOSE: To review the effectiveness and safety of embolisation in managing haemorrhage from the external carotid artery (ECA) system in radiated nasopharyngeal carcinoma (NPC) patients. METHODS: Radiated NPC patients who presented with severe oronasal bleeding and underwent digital subtraction angiography that excluded blowouts from the internal carotid artery from 2011 to 2021 were reviewed. Those who subsequently underwent embolisation of the ECA system were analysed for technical success rate, post-embolisation re-bleeding rate and complications. RESULTS: Seventeen embolisations were performed in fifteen patients during the 10-year period. The technical success rate was 100%, however the early haemostatic rate (no re-bleed within 7 days of embolisation) was 70.6% (12/17) and the overall long-term haemostatic rate was 58.8% (10/17). The re-bleed rates of targeted and empiric embolisations were 33.3% (3/9) and 50.0% (4/8), respectively. The re-bleed rates with liquid agents, coils and particles were 0% (0/7), 33.3% (1/3) and 85.7% (6/7), respectively. Amongst the embolisations utilising liquid agents, 71.4% (5/7) were targeted, distal embolisations. All re-bleeds underwent surgical ligation or repeat embolisation; half of them further experienced recurrent bleeding. There were no significant complications with embolisation. CONCLUSION: Although embolisation of the ECA system in NPC has a high technical success rate and is safe, re-bleeding appears to be common. Targeted, distal embolisation with liquid embolics appear to have good haemostatic effect. Clinicians should be aware that patients may need repeated procedures to secure haemostasis.

Novel findings in immunopathophysiology of chronic rhinosinusitis and their role in a model of precision medicine.

Our understanding of the pathophysiology of chronic rhinosinusitis (CRS) is continuously evolving. The traditional description of CRS in terms of two phenotypes based on the presence or absence of nasal polyps belies the underlying intricate immunopathophysiological processes responsible for this condition. CRS is being increasingly recognized as a disease spectrum encompassing a range of inflammatory states in the sinonasal cavity, with non-type 2 inflammatory disease on one end, type 2 inflammatory, eosinophil-heavy disease on the other and an overlap of both in different proportions in between. Abundance in research on the immune mechanisms of CRS has revealed various new endotypes that hold promise as biomarkers for the development of targeted therapies in severe, uncontrolled CRS. The introduction of precision medicine to manage this chronic, complex condition is a step forward in providing individualized care for all patients with CRS. In this review, the latest research on the pathophysiology of CRS with a focus on potential novel biomarkers and treatment options over the last 2 years are summarized and integrated into a suggested model of precision medicine in CRS.

Upregulation of cell-surface mucin MUC15 in human nasal epithelial cells upon influenza A virus infection.

BACKGROUND: Cell-surface mucins are expressed in apical epithelial cells of the respiratory tract, and contribute a crucial part of the innate immune system. Despite anti-inflammatory or antiviral functions being revealed for certain cell-surface mucins such as MUC1, the roles of other mucins are still poorly understood, especially in viral infections. METHODS: To further identify mucins significant in influenza infection, we screened the expression of mucins in human nasal epithelial cells infected by H3N2 influenza A virus. RESULTS: We found that the expression of MUC15 was significantly upregulated upon infection, and specific only to active infection. While MUC15 did not interact with virus particles or reduce viral replication directly, positive correlations were observed between MUC15 and inflammatory factors in response to viral infection. Given that the upregulation of MUC15 was only triggered late into infection when immune factors (including cytokines, chemokines, EGFR and phosphorylated ERK) started to peak and plateau, MUC15 may potentially serve an immunomodulatory function later during influenza viral infection. CONCLUSIONS: Our study revealed that MUC15 was one of the few cell-surface mucins induced during influenza infection. While MUC15 did not interact directly with influenza virus, we showed that its increase coincides with the peak of immune activation and thus MUC15 may serve an immunomodulatory role during influenza infection.

H3N2 influenza virus infection enhances oncostatin M expression in human nasal epithelium.

Tight junctions (TJs) alteration is commonly seen in airway inflammatory diseases. Oncostatin M (OSM) is an inflammatory mediator associated with chronic rhinosinusitis with nasal polyps (CRSwNP). We have previously shown that human nasal epithelial cells (hNECs) are highly permissive cells for influenza A virus (IAV). However, its role in TJs alteration and the effects of IAV on inducing OSM expression in nasal epithelium remains to be further investigated. In this study, OSM and TJs expression was measured and compared between inferior turbinate from healthy controls and nasal polyps from CRSwNP. Additionally, hNECs cultured at air-liquid interface (ALI) were infected with H3N2 influenza virus to study the role of influenza virus in inducing epithelial OSM expression as a possible means of exacerbation. The expression of ZO-1, claudin-1, and occludin was markedly decreased and correlated negatively with that of OSM in CRSwNP. By using the in vitro hNEC model, H3N2 infection resulted in significantly increased OSM expression (2.2-, 4.7- and 3.9-fold higher at 8, 24, and 48 h post-infection vs. mock infection). Furthermore, OSM is found to co-localize with ciliated and goblet cells in hNECs infected with H3N2 influenza virus. Our findings demonstrated that increased OSM expression is implicated in CRSwNP as a possible mechanism of TJs' impairment, which can be further augmented following influenza infection via epithelial OSM expression, possibly contributing to exacerbations.

Sino-orbital desmoid tumor in a pediatric patient - Case report with review of literature.

We report a case of a 2-year-old female who presented with bilateral progressive proptosis, visual loss, nasal obstruction, and breathing difficulty. Magnetic resonance imaging revealed a large sino-orbital mass that was extending to the orbital apex and skull base. An initial diagnosis of rhabdomyosarcoma was made elsewhere on the basis of the presence of round and spindle cell tumor. Subsequent biopsy with immunohistochemical staining was positive for nuclear staining with ß-catenin, shifting the diagnosis to a myofibroblastic tumor, favoring desmoid-type fibromatosis. With image guidance, near complete excision of tumor was performed by a multidisciplinary team, while respecting danger zones such as the skull base and the optic nerve. Following a recurrence over 2 months, additional excision was performed with a 6-month treatment of methotrexate and vinblastine. Desmoid tumor is a rare form of soft tissue tumor uncommonly seen in the orbital area. Although benign, it is known to be recurrent and infiltrative. Few data are known and further information will aid in the management of these tumors.

In Vitro Model of Fully Differentiated Human Nasal Epithelial Cells Infected With Rhinovirus Reveals Epithelium-Initiated Immune Responses.

Human rhinoviruses (HRVs) are the commonest cause of the common cold. While HRV is less pathogenic than other respiratory viruses, it is frequently associated with exacerbation of chronic respiratory diseases such as rhinosinusitis and asthma. Nasal epithelial cells are the first sites of viral contact, immune initiation, and airway interconnectivity, but there are limited studies on HRV infection of nasal epithelial cells. Hence, we established a model of HRV infection of in vitro-differentiated human nasal epithelial cells (hNECs) derived from multiple individuals. Through HRV infection of hNECs, we found that HRV mainly targeted ciliated cells and preferentially induced type I and III interferon antiviral pathways. Quantitative polymerase chain reaction analysis of inflammatory genes suggested predominant type 1 immunity signaling and recruitment, with secreted CXCL9, IP-10, CXCL11, and RANTES as likely initiators of airway inflammatory responses. Additionally, we further explored HRV bidirectional release from the hNECs and identified 11 associated genes. Other HRV interactions were also identified through a systematic comparison with influenza A virus infection of hNECs. Overall, this in vitro hNEC HRV infection model provides a platform for repeatable and controlled studies of different individuals, thus providing novel insights into the roles of human nasal epithelium in HRV interaction and immune initiation.

Downregulation and Aberrant Localization of Forkhead Box J1 in Allergic Nasal Mucosa.

BACKGROUND: Forkhead box J1 (FOXJ1) plays pivotal roles in motile cilia formation. However, it remains unclear whether abnormal expression or localization of FOXJ1 in nasal mucosa tissues is associated with allergic rhinitis (AR), in which impaired mucociliary clearance is implicated. OBJECTIVE: We sought to investigate the expression and localization of FOXJ1 in inferior turbinate from patients with AR and controls. METHODS: We assayed mRNA levels of FOXJ1, DNAI1, DNALI1, and DNAH9 by using whole-genome expression array and quantitative real-time polymerase chain reaction. We elucidated the localization of FOXJ1 by using immunofluorescence assays in paraffin sections and primary single cells. Four patterns of FOXJ1 localization (normal, N; intermediate, I; mislocalization, M; absence, A) were defined. We developed a semiquantitative scoring system to elucidate their localization in 5 areas per paraffin section, with individual sections being assigned a score between 0 and 2. RESULTS: The mRNA levels of FOXJ1, DNAI1, DNALI1, and DNAH9 were significantly reduced in patients with AR compared with controls (all p < 0.05). The median (1st and 3rd quartile) of the FOXJ1 score was 0.4 (0.0 and 0.85) in patients with AR, and 0.2 (0.0 and 0.4) in controls (p < 0.05). For primary cytospin samples, the mean percentages of FOXJ1 localization patterns N, I, M, and A were 46.7, 10.0, 30.0, and 26.7% in patients with AR, and 82.5, 5.0, 5.0, and 7.5% in controls, respectively (p < 0.05). CONCLUSION: Downregulation and aberrant localization of FOXJ1 may be crucial characteristics of the allergic nasal mucosa.

Flow-diverter in radiation-induced skull base carotid blowout syndrome: do not write it off!

Post-radiotherapy carotid blowout syndrome (CBS) of the skull base is a rare but often catastrophic complication of head and neck malignancies. The existing literature on the treatment of this condition with flow-diverting devices (FDD) is extremely limited and disappointing. We present a case of impending CBS in a patient previously irradiated for nasopharyngeal cancer that was successfully treated with use of multiple FDDs, adjunctive endonasal packing and delayed reinforcement with pedicled naso-septal flap, yielding an excellent outcome at 14-months follow-up. Notwithstanding the discouraging results in literature, our anecdotal experience suggests that endovascular reconstruction using FDD could be an option with long-term viability in post-radiotherapy CBS involving the skull base when reinforced with a vascularised naso-septal flap.

Delayed Breakdown of an Onlay Pericranial Flap Following Endoscopic Craniofacial Resection.

The pericranial flap is a well-vascularized, robust flap that is used to reconstruct anterior skull base defects following resection of skull base tumors. Failure of this flap is uncommon. However when it occurs, the consequences are potentially disastrous and it poses a challenge to further reconstruction. The authors report the first patient of onlay pericranial flap breakdown following endoscopic craniofacial resection. Possible contributing factors are identified and further management is discussed. With the endoscopic approach being increasingly utilized for craniofacial resection, it is imperative to be mindful of these factors to minimize the risks of onlay pericranial flap failure.

IgG4-positive extranodal marginal zone lymphoma arising in Hashimoto's thyroiditis: clinicopathological and cytogenetic features of a hitherto undescribed condition.

AIMS: Hashimoto's thyroiditis was recently divided into IgG4-plasma cell-rich and IgG4-plasma cell-poor subtypes. The former, also known as IgG4 thyroiditis, is associated with clinical, serological, sonographic and morphological features that are distinctive from those of the non-IgG4 subgroup. We describe an interesting case of IgG4-positive mucosa-associated lymphoid tissue (MALT) lymphoma arising in a background of IgG4 thyroiditis. METHODS AND RESULTS: The thyroid gland showed typical features of IgG4 thyroiditis, including characteristic patterns of fibrosis. A dense lymphoplasmacytic infiltrate diffusely involved the entire gland without formation of a destructive tumour mass. Lymphoepithelial lesions were prominent. There were abundant IgG4-positive plasma cells, with the IgG4/IgG ratio exceeding 40%. The IgG4-positive plasma cells were monotypic for kappa light chain, and there was monoclonal IGH rearrangement. Fluorescence in-situ hybridization revealed IGH translocation without translocation of MALT1, bcl-10, or FOXP1. CONCLUSIONS: This represents the first case of IgG4-producing MALT lymphoma associated with IgG4 thyroiditis. IGH translocation with an unknown partner gene was identified. We suggest the performance of serum and immunohistochemical investigations for IgG and IgG4 in all cases of Hashimoto's thyroiditis to diagnose IgG4 thyroiditis. In addition, clonality assays and light chain studies are useful to exclude a low-grade lymphoma arising in this context.

Endoscopic Endonasal Resection of Recurrent Nasopharyngeal Mucoepidermoid Carcinoma.

Nasopharyngeal mucoepidermoid carcinoma is a rare entity, for which surgical resection is the treatment of choice. The open technique is considered the standard approach, but this often results in significant morbidities such as trismus, dysphagia, and neurologic deficits. The advent of endoscopic endonasal techniques has made endoscopic resection a viable alternative to the open approach in terms of access, adequacy of resection, and lesser surgical morbidity. The authors describe a patient of recurrent nasopharyngeal mucoepidermoid carcinoma that was resected entirely endoscopically. The authors also present a literature review of this little-known disease and a comparison between the endoscopic and open approach.

Endoscopic and Radiologic Central Compartment Disease as Predictors of Perennial Inhalant Allergen Sensitization in Chronic Rhinosinusitis.

BACKGROUND: Central compartment atopic disease (CCAD) is a recently described variant of chronic rhinosinusitis (CRS) strongly associated with atopy. The association between central compartment disease (CCD) and inhalant allergy is not well established in South-East Asia, where perennial allergic rhinitis is common. OBJECTIVES: The primary objective was to evaluate endoscopic and radiologic CCD as predictors of perennial allergen sensitization in primary CRS. The secondary objective was to compare clinical characteristics of CCAD with other CRS subtypes (CRSwNP and CRSsNP). METHODS: A retrospective study of consecutive patients with primary CRS who underwent endoscopic sinus surgery at our institution was performed. Allergen sensitization was confirmed by skin or serum testing. Endoscopy records and computed tomography scans of paranasal sinuses were reviewed for CCD. The diagnostic accuracy of endoscopic and radiologic CCD in predicting atopy was calculated. RESULTS: There were 104 patients (43 CCAD, 30 CRSwNP and 31 CRSsNP). Endoscopic CCD was significantly associated with aeroallergen sensitization (odds ratio (OR) 3.99, 95% confidence interval (CI) 1.65-9.67, P = 0.002). Endoscopic CCD predicted atopy with 57% sensitivity, 72% specificity, 69% positive predictive value and positive likelihood ratio of 2.05. Radiologic CCD was not associated with aeroallergen sensitization (OR 0.728, 95%CI 0.292-1.82, P = 0.496). There were more CCAD patients who reported hyposmia (86% vs 42%, P < 0.001) and had anosmia on olfactory testing than CRSsNP (65% vs 14%, P = 0.015). The prevalence of atopy was significantly higher in CCAD than CRSwNP and CRSsNP (70% vs 37% and 42%, P = 0.015 and P = 0.05, respectively). Median serum total immunoglobulin E was higher in CCAD (283 IU/ml) and CRSwNP (127 IU/ml) than CRSsNP (27 IU/ml, P = 0.006 and P = 0.042, respectively). CONCLUSIONS: Endoscopic CCD was a better predictor of inhalant allergy than radiologic CCD in primary CRS, in a locale of perennial allergic rhinitis.

Outcomes of SWI/SNF complex-deficient sinonasal carcinomas in a Southeast Asian cohort.

BACKGROUND: SWI/SNF complex-deficient sinonasal carcinomas are rare, genetically distinct, and aggressive entities. METHODS: SMARCB1 and SMARCA4 immunohistochemistry was retrospectively performed on a cohort of undifferentiated, poorly differentiated, and poorly defined sinonasal carcinomas. Survival outcomes were compared between SMARCB1/SMARCA4 (SWI/SNF complex)-deficient and -retained groups. RESULTS: Eight SWI/SNF complex-deficient (six SMARCB1-deficient, two SMARCA4-deficient) cases were identified among 47 patients over 12 years. Triple-modality treatment was more frequently utilized in SWI/SNF complex-deficient carcinomas than in SWI/SNF complex-retained carcinomas (71.4% vs. 11.8%, p = 0.001). After a median follow-up of 21.3 (IQR 9.9-56.0) months, SWI/SNF complex-deficient sinonasal carcinomas showed comparable recurrence rates (57.1% vs. 52.9%, p = 0.839), time-to-recurrence (7.3 [IQR 6.6-8.3] vs. 9.1 [IQR 3.9-17.4] months, p = 0.531), and overall survival (17.7 [IQR 11.8-67.0] vs. 21.6 [IQR 8.9-56.0] months, p = 0.835) compared to SWI/SNF complex-retained sinonasal carcinomas. CONCLUSION: Triple-modality treatment may improve survival in SWI/SNF complex-deficient sinonasal carcinomas.

Deconstructive versus reconstructive approach to internal carotid artery blowout in radiated nasopharyngeal carcinoma: A tertiary center experience and systematic review.

The objective of this study was to compare the outcomes of parent artery occlusion (PAO) versus stent-assisted reconstruction in radiated nasopharyngeal carcinoma (NPC) patients with internal carotid artery (ICA) blowouts. A retrospective review from our institution (2011-2021) and systematic review of Pubmed and Embase (1995-2022) was performed. Twenty-eight eligible studies were identified. Eighty-six PAOs and 37 stent-assisted reconstructions were analyzed, including 11 PAOs and 5 stents from our institution. Stents were associated with significantly higher incidence of overall re-bleeding (16.2% [95% CI 7.4-31.9] vs. 4.6% [95% CI 1.3-13.5], p = 0.047), delayed stroke (5.4% [95% CI 1.3-19.4] vs. 0%, p = 0.034) and reduced median survival (7.1 [95% CI 3.8-14.0] months vs. 29.0 [95% CI 9.4-63.4] months, p = 0.017) compared to PAO. There were no significant differences in terms of overall stroke, infection, extruded/migrated foreign body, and peri-procedure death. PAO is preferred over reconstructive treatment in patients with adequate collateral circulation.

Human Nasal Epithelial Cells Sustain Persistent SARS-CoV-2 Infection In Vitro, despite Eliciting a Prolonged Antiviral Response.

The dynamics of SARS-CoV-2 infection in COVID-19 patients are highly variable, with a subset of patients demonstrating prolonged virus shedding, which poses a significant challenge for disease management and transmission control. In this study, the long-term dynamics of SARS-CoV-2 infection were investigated using a human well-differentiated nasal epithelial cell (NEC) model of infection. NECs were observed to release SARS-CoV-2 virus onto the apical surface for up to 28 days postinfection (dpi), further corroborated by viral antigen staining. Single-cell transcriptome sequencing (sc-seq) was utilized to explore the host response from infected NECs after short-term (3-dpi) and long-term (28-dpi) infection. We identified a unique population of cells harboring high viral loads present at both 3 and 28 dpi, characterized by expression of cell stress-related genes DDIT3 and ATF3 and enriched for genes involved in tumor necrosis factor alpha (TNF-α) signaling and apoptosis. Remarkably, this sc-seq analysis revealed an antiviral gene signature within all NEC cell types even at 28 dpi. We demonstrate increased replication of basal cells, absence of widespread cell death within the epithelial monolayer, and the ability of SARS-CoV-2 to replicate despite a continuous interferon response as factors likely contributing to SARS-CoV-2 persistence. This study provides a model system for development of therapeutics aimed at improving viral clearance in immunocompromised patients and implies a crucial role for immune cells in mediating viral clearance from infected epithelia. IMPORTANCE Increasing medical attention has been drawn to the persistence of symptoms (long-COVID syndrome) or live virus shedding from subsets of COVID-19 patients weeks to months after the initial onset of symptoms. In vitro approaches to model viral or symptom persistence are needed to fully dissect the complex and likely varied mechanisms underlying these clinical observations. We show that in vitro differentiated human NECs are persistently infected with SARS-CoV-2 for up to 28 dpi. This viral replication occurred despite the presence of an antiviral gene signature across all NEC cell types even at 28 dpi. This indicates that epithelial cell intrinsic antiviral responses are insufficient for the clearance of SARS-CoV-2, implying an essential role for tissue-resident and infiltrating immune cells for eventual viral clearance from infected airway tissue in COVID-19 patients.

Magnetic Resonance Imaging Study of the Pericranial Flap and Its Local Effects Following Endoscopic Craniofacial Resection.

OBJECTIVES/HYPOTHESIS: To describe the magnetic resonance imaging (MRI) characteristics of the pericranial flap, changes in the pericranial flap thickness over time, presence of frontal sinus opacification, and presence of frontal lobe herniation into the nasal cavity. STUDY DESIGN: Retrospective case series. METHODS: Seventeen consecutive endoscopic craniofacial resections with pericranial flap reconstruction performed at a tertiary hospital from 2010 to 2019 were reviewed. Sixty-eight serial MRI scans were evaluated. RESULTS: All pericranial flaps consistently featured a homogenous appearance on T1-weighted sequence and enhanced with contrast. On T2-weighted sequence, the skull base reconstruction demonstrated four layers of alternating hypo- and hyperintensity, which corresponded with the inlay synthetic graft or neodura (hypointense), loose areolar tissue (hyperintense), fibrous pericranium (hypointense), and nasal mucosa or granulation tissue (hyperintense). The mean pericranial flap thickness was 9.9 mm. In thicker flaps, the loose areolar layer contributed the bulk of the thickness. Of 13 patients who underwent three or more serial MRI scans, 11 flaps (84.6%) were stable and two (15.4%) had >50% reduction in their original thickness over time. Thirteen of 17 (76.5%) patients had frontal sinus opacification on follow-up. None developed frontal sinus mucoceles or frontal lobe herniation. CONCLUSIONS: The pericranial flap has a distinctive MRI appearance, especially on T2-weighted sequence. The thickness of the flap remains relatively stable over time for most patients even following radiotherapy. It is a sturdy flap that is able to support the frontal lobe. Frontal sinus obstruction is common, although complications from this appear to be rare. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:E90-E97, 2021.