Evolution of nasal and olfactory infection characteristics of SARS-CoV-2 variants.

SARS-CoV-2 infection of the upper airway and the subsequent immune response are early, critical factors in COVID-19 pathogenesis. By studying infection of human biopsies in vitro and in a hamster model in vivo, we demonstrated a transition in nasal tropism from olfactory to respiratory epithelium as the virus evolved. Analyzing each variant revealed that SARS-CoV-2 WA1 or Delta infect a proportion of olfactory neurons in addition to the primary target sustentacular cells. The Delta variant possessed broader cellular invasion capacity into the submucosa, while Omicron displayed enhanced nasal respiratory infection and longer retention in the sinonasal epithelium. The olfactory neuronal infection by WA1 and the subsequent olfactory bulb transport via axon were more pronounced in younger hosts. In addition, the observed viral clearance delay and phagocytic dysfunction in aged olfactory mucosa were accompanied by a decline of phagocytosis-related genes. Further, robust basal stem cell activation contributed to neuroepithelial regeneration and restored ACE2 expression postinfection. Together, our study characterized the nasal tropism of SARS-CoV-2 strains, immune clearance, and regeneration after infection. The shifting characteristics of viral infection at the airway portal provide insight into the variability of COVID-19 clinical features, particularly long COVID, and may suggest differing strategies for early local intervention.

Inflammation-related pathology in the olfactory epithelium: its impact on the olfactory system in psychotic disorders.

Smell deficits and neurobiological changes in the olfactory bulb (OB) and olfactory epithelium (OE) have been observed in schizophrenia and related disorders. The OE is the most peripheral olfactory system located outside the cranium, and is connected with the brain via direct neuronal projections to the OB. Nevertheless, it is unknown whether and how a disturbance of the OE affects the OB in schizophrenia and related disorders. Addressing this gap would be the first step in studying the impact of OE pathology in the disease pathophysiology in the brain. In this cross-species study, we observed that chronic, local OE inflammation with a set of upregulated genes in an inducible olfactory inflammation (IOI) mouse model led to a volume reduction, layer structure changes, and alterations of neuron functionality in the OB. Furthermore, IOI model also displayed behavioral deficits relevant to negative symptoms (avolition) in parallel to smell deficits. In first episode psychosis (FEP) patients, we observed a significant alteration in immune/inflammation-related molecular signatures in olfactory neuronal cells (ONCs) enriched from biopsied OE and a significant reduction in the OB volume, compared with those of healthy controls (HC). The increased expression of immune/inflammation-related molecules in ONCs was significantly correlated to the OB volume reduction in FEP patients, but no correlation was found in HCs. Moreover, the increased expression of human orthologues of the IOI genes in ONCs was significantly correlated with the OB volume reduction in FEP, but not in HCs. Together, our study implies a potential mechanism of the OE-OB pathology in patients with psychotic disorders (schizophrenia and related disorders). We hope that this mechanism may have a cross-disease implication, including COVID-19-elicited mental conditions that include smell deficits.

Reduction in olfactory dysfunction prevalence among patients with diabetes taking metformin.

KEY POINTS: Metformin treatment is associated with reduced olfactory dysfunction (OD) in diabetic patients Metformin may possess potential protective effects on olfaction beyond glycemic control.

Inflammation-related pathology in the olfactory epithelium: its impact on the olfactory system in psychotic disorders.

Smell deficits and neurobiological changes in the olfactory bulb (OB) and olfactory epithelium (OE) have been observed in schizophrenia and related disorders. The OE is the most peripheral olfactory system located outside the cranium, and is connected with the brain via direct neuronal projections to the OB. Nevertheless, it is unknown whether and how a disturbance of the OE affects the OB in schizophrenia and related disorders. Addressing this gap would be the first step in studying the impact of OE pathology in the disease pathophysiology in the brain. In this cross-species study, we observed that chronic, local OE inflammation with a set of upregulated genes in an inducible olfactory inflammation (IOI) mouse model led to a volume reduction, layer structure changes, and alterations of neuron functionality in the OB. Furthermore, IOI model also displayed behavioral deficits relevant to negative symptoms (avolition) in parallel to smell deficits. In first episode psychosis (FEP) patients, we observed a significant alteration in immune/inflammation-related molecular signatures in olfactory neuronal cells (ONCs) enriched from biopsied OE and a significant reduction in the OB volume, compared with those of healthy controls (HC). The increased expression of immune/inflammation-related molecules in ONCs was significantly correlated to the OB volume reduction in FEP patients, but no correlation was found in HCs. Moreover, the increased expression of human orthologues of the IOI genes in ONCs was significantly correlated with the OB volume reduction in FEP, but not in HCs. Together, our study implies a potential mechanism of the OE-OB pathology in patients with psychotic disorders (schizophrenia and related disorders). We hope that this mechanism may have a cross-disease implication, including COVID-19-elicited mental conditions that include smell deficits.

The Association of Multiple Sensory Impairment and Telomere Length: The Health ABC Study.

OBJECTIVES: The objective of this study was to characterize the associations of sensory impairments, including olfaction (OI), vision (VI), hearing (HI), and touch (TI), with telomere length (TL) in a group of community-dwelling older adults who participated in the Health ABC study. METHODS: Across 1603 participants, OI was classified with the Brief Smell Identification Test (<11), HI with pure-tone averages (<25 dB), VI with visual acuity (20/50 or worse), and TI with monofilament testing (inability to detect three of four touches). Shorter TL was defined as the lowest quartile of sample TLs. Adjusted multivariable regressions were used to examine the cross-sectional association between the modality, severity, and number of sensory impairments with TL. RESULTS: Participants had an average age of 77.4 ± 2.84 years, and 89.7% (n = 1438) had at least one or more sensory impairments. Severe OI (odds ratio [OR] = 1.73, 95% confidence interval [CI] = [1.19, 2.6]) was independently associated with increased odds of shorter TL. Additionally, having one (OR = 2.79, 95% CI = [1.69, 4.70]), two (OR = 2.5, 95% CI = [1.51, 4.26]), three (OR = 3.04, 95% CI = [1.79, 5.36]), or four impairments (OR = 3.72, 95% CI = [1.52, 7.33]) was associated with increased odds of shorter TL in a dose-dependent manner. CONCLUSION: Severe OI and TI appear to be particularly robust markers of shortened TL. Additionally, multiple sensory impairment is strongly associated with shortened TL, suggesting that sensory dysfunction may represent a unique biomarker of unhealthy aging. LEVEL OF EVIDENCE: Level II Laryngoscope, 133:3132-3138, 2023.

Biologics for Nasal Polyps: Synthesizing Current Recommendations into a Practical Clinical Algorithm.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) has been traditionally managed with a combination of topical and systemic medical therapy as well as endoscopic sinus surgery. The emergence of biologic therapies that target specific aspects of the inflammatory cascade has ushered in a potentially new paradigm in the management options available for CRSwNP. PURPOSE: To summarize the current literature and recommendations supporting the use of available biologic therapies for CRSwNP and to develop an algorithm to aid clinical decision-making regarding treatment selection. METHODS: A review of available literature and studies that demonstrated the clinical efficacy of biologic agents for the treatment of CRSwNP informing current CRSwNP consensus algorithms. RESULTS: Current biologic medications target immunoglobulin E, interleukins, or interleukin receptors implicated in the Th2 inflammatory cascade. Institution of biologic therapy is now an option for patients who have disease refractory to topical medical therapy and endoscopic sinus surgery, those who cannot tolerate surgery, or patients with other comorbid Th2 diseases. Response to treatment should be monitored at 4-6 months and 1 year after initiating therapy. Across multiple indirect comparisons, dupilumab appears to have the largest therapeutic benefit across multiple subjective and objective outcomes. The choice of therapeutic agent also depends on drug availability, patient tolerance, presence of comorbid illnesses, and cost. CONCLUSIONS: Biologics are emerging as an important option in the management of patients with CRSwNP. While more data is required to fully inform indications, treatment selection, and health economics related to their use, biologics may offer robust symptom relief to patients who have failed other interventions.

Olfaction Now and in the Future in CRSwNP.

BACKGROUND: Chronic rhinosinusitis (CRS) is the leading cause of olfactory dysfunction in the general population. Olfactory dysfunction is more common in patients with CRS with nasal polyposis (CRSwNP) compared to those without polyps. PURPOSE: The present review aims to summarize the current literature on the mechanism behind olfactory dysfunction in CRSwNP and the impact of therapy on olfactory outcomes in this patient population. METHODS: A comprehensive review of the available literature on olfaction in CRSwNP was performed. We evaluated the most recent evidence from studies on the mechanisms behind smell loss in CRSwNP and the impact of medical and surgical therapy for CRS on olfactory outcomes. RESULTS: The mechanism behind olfactory dysfunction in CRSwNP is not completely understood, but evidence from clinical research and animal models suggests both an obstructive component causing conductive olfactory loss and an inflammatory response in the olfactory cleft leading to sensorineural olfactory loss. Oral steroids and endoscopic sinus surgery have both shown efficacy in improving olfactory outcomes in CRSwNP in the short term; however, the long-term response of these treatments remains uncertain. Newer targeted biologic therapies, such as dupilumab, have also shown remarkable and durable improvement in smell loss for CRSwNP patients. CONCLUSION: Olfactory dysfunction is highly prevalent in the CRSwNP population. Although significant advances have been made in our understanding of olfactory dysfunction in the setting of CRS, additional studies are needed to elucidate cellular and molecular changes mediated by type 2-mediated inflammation in the olfactory epithelium with potential downstream effects on the central olfactory system. Further identification of these underlying basic mechanisms will be vital for developing future therapies targeted to improve olfactory dysfunction in patients with CRSwNP.

Chronic interleukin-13 expression in mouse olfactory mucosa results in regional aneuronal epithelium.

BACKGROUND: Olfactory dysfunction is highly associated with chronic rhinosinusitis with nasal polyps (CRSwNP), and the severity of loss has been linked with biomarkers of type 2 inflammation. The ability of dupilumab to rapidly improve the sense of smell prior to improvement in polyp size suggests a direct role of IL-4/IL-13 receptor signaling in the olfactory epithelium (OE). METHODS: We created a transgenic mouse model in which IL-13 is inducibly expressed specifically within the OE. Gene expression analysis and immunohistology were utilized to characterize the effect of IL-13 on the structure of the OE. RESULTS: After induction of olfactory IL-13 expression, there is a time-dependent loss of neurons from OE regions, accompanied by a modest inflammatory infiltrate. Horizontal basal cells undergo morphologic changes consistent with activation and demonstrate proliferation. Mucus production and increased expression of eotaxins is observed, with marked expression of Ym2 by sustentacular cells. DISCUSSION: Chronic IL-13 exposure has several effects on the OE that are likely to affect function. The neuronal loss is in keeping with other models of allergic type 2 nasal inflammation. Future studies are needed to correlate cellular and molecular alterations in olfactory cell populations with findings in human CRSwNP, as well as to assess olfactory function in behavioral model systems.

Olfactory impairment in psychiatric disorders: Does nasal inflammation impact disease psychophysiology?

Olfactory impairments contribute to the psychopathology of mental illnesses such as schizophrenia and depression. Recent neuroscience research has shed light on the previously underappreciated olfactory neural circuits involved in regulation of higher brain functions. Although environmental factors such as air pollutants and respiratory viral infections are known to contribute to the risk for psychiatric disorders, the role of nasal inflammation in neurobehavioral outcomes and disease pathophysiology remains poorly understood. Here, we will first provide an overview of published findings on the impact of nasal inflammation in the olfactory system. We will then summarize clinical studies on olfactory impairments in schizophrenia and depression, followed by preclinical evidence on the neurobehavioral outcomes produced by olfactory dysfunction. Lastly, we will discuss the potential impact of nasal inflammation on brain development and function, as well as how we can address the role of nasal inflammation in the pathophysiological mechanisms underlying psychiatric disorders. Considering the current outbreak of Coronavirus Disease 2019 (COVID-19), which often causes nasal inflammation and serious adverse effects for olfactory function that might result in long-lasting neuropsychiatric sequelae, this line of research is particularly critical to understanding of the potential significance of nasal inflammation in the pathophysiology of psychiatric disorders.

Olfactory Loss and Beyond: A Practical Review of Chemosensory Dysfunction.

BACKGROUND: Our ability to smell and taste is dictated by 3 chemosensory systems with distinct physiologic mechanisms - olfaction, gustation, and chemesthesis. Although often overlooked, dysfunction of these special senses may have broad implications on multiple facets of patients' lives -including safety, nutritional status, quality of life, mental health, and even cognitive function. As "loss of smell or taste" emerged as a common symptom of coronavirus disease 2019 (COVID-19), the importance of intact chemosensory function has been thrust into the spotlight. Despite the growing recognition of chemosensory dysfunction, this already highly prevalent condition will increasingly impact a larger and more diverse population, highlighting the need for improved awareness and care of these patients. METHODS: Comtemporary review of chemosensory function and assessments. CONCLUSIONS: Although patient-reported chemosensory function measures highlight the ease of screening of chemosensory dysfunction, self-reported measures underestimate both the prevalence and degree of chemosensory dysfunction and do not adequately distinguish between olfaction, gustation, and chemesthesis. Meanwhile, psychophysical assessment tools provide opportunities for more accurate, thorough assessment of the chemosenses when appropriate. Primary care providers are uniquely situated to identify patients burdened by chemosensory dysfunction and raise patient and provider awareness about the importance of chemosensory dysfunction. Identification of chemosensory dysfunction, particularly olfactory dysfunction, may raise suspicion for many underlying medical conditions, including early detection of neurodegenerative conditions. Furthermore, identification and awareness of patients with chemosensory dysfunction may help primary care providers to identify those who may benefit from additional therapeutic and safety interventions, or consultations with specialists for more detailed evaluations and management.

Evolution of nasal and olfactory infection characteristics of SARS-CoV-2 variants.

SARS-CoV-2 infection of the upper airway and the subsequent immune response are early, critical factors in COVID-19 pathogenesis. By studying infection of human biopsies in vitro and in a hamster model in vivo, we demonstrated a transition in tropism from olfactory to respiratory epithelium as the virus evolved. Analyzing each variants revealed that SARS-CoV-2 WA1 or Delta infects a proportion of olfactory neurons in addition to the primary target sustentacular cells. The Delta variant possesses broader cellular invasion capacity into the submucosa, while Omicron displays longer retention in the sinonasal epithelium. The olfactory neuronal infection by WA1 and the subsequent olfactory bulb transport via axon is more pronounced in younger hosts. In addition, the observed viral clearance delay and phagocytic dysfunction in aged olfactory mucosa is accompanied by a decline of phagocytosis related genes. Furthermore, robust basal stem cell activation contributes to neuroepithelial regeneration and restores ACE2 expression post-infection. Together, our study characterized the nasal tropism of SARS-CoV-2 strains, immune clearance, and regeneration post infection. The shifting characteristics of viral infection at the airway portal provides insight into the variability of COVID-19 clinical features and may suggest differing strategies for early local intervention.

International consensus statement on allergy and rhinology: Olfaction.

BACKGROUND: The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O). METHODS: Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus. RESULTS: The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies. CONCLUSION: This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

A bacterial extracellular vesicle-based intranasal vaccine against SARS-CoV-2 protects against disease and elicits neutralizing antibodies to wild-type and Delta variants.

Several vaccines have been introduced to combat the coronavirus infectious disease-2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current SARS-CoV-2 vaccines include mRNA-containing lipid nanoparticles or adenoviral vectors that encode the SARS-CoV-2 Spike (S) protein of SARS-CoV-2, inactivated virus, or protein subunits. Despite growing success in worldwide vaccination efforts, additional capabilities may be needed in the future to address issues such as stability and storage requirements, need for vaccine boosters, desirability of different routes of administration, and emergence of SARS-CoV-2 variants such as the Delta variant. Here, we present a novel, well-characterized SARS-CoV-2 vaccine candidate based on extracellular vesicles (EVs) of Salmonella typhimurium that are decorated with the mammalian cell culture-derived Spike receptor-binding domain (RBD). RBD-conjugated outer membrane vesicles (RBD-OMVs) were used to immunize the golden Syrian hamster (Mesocricetus auratus) model of COVID-19. Intranasal immunization resulted in high titres of blood anti-RBD IgG as well as detectable mucosal responses. Neutralizing antibody activity against wild-type and Delta variants was evident in all vaccinated subjects. Upon challenge with live virus, hamsters immunized with RBD-OMV, but not animals immunized with unconjugated OMVs or a vehicle control, avoided body mass loss, had lower virus titres in bronchoalveolar lavage fluid, and experienced less severe lung pathology. Our results emphasize the value and versatility of OMV-based vaccine approaches.

A bacterial extracellular vesicle-based intranasal vaccine against SARS-CoV-2 protects against disease and elicits neutralizing antibodies to wild-type and Delta variants.

Several vaccines have been introduced to combat the coronavirus infectious disease-2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Current SARS-CoV-2 vaccines include mRNA-containing lipid nanoparticles or adenoviral vectors that encode the SARS-CoV-2 Spike (S) protein of SARS-CoV-2, inactivated virus, or protein subunits. Despite growing success in worldwide vaccination efforts, additional capabilities may be needed in the future to address issues such as stability and storage requirements, need for vaccine boosters, desirability of different routes of administration, and emergence of SARS-CoV-2 variants such as the Delta variant. Here, we present a novel, well-characterized SARS-CoV-2 vaccine candidate based on extracellular vesicles (EVs) of Salmonella typhimurium that are decorated with the mammalian cell culture-derived Spike receptor-binding domain (RBD). RBD-conjugated outer membrane vesicles (RBD-OMVs) were used to immunize the golden Syrian hamster ( Mesocricetus auratus ) model of COVID-19. Intranasal immunization resulted in high titers of blood anti-RBD IgG as well as detectable mucosal responses. Neutralizing antibody activity against wild-type and Delta variants was evident in all vaccinated subjects. Upon challenge with live virus, hamsters immunized with RBD-OMV, but not animals immunized with unconjugated OMVs or a vehicle control, avoided body mass loss, had lower virus titers in bronchoalveolar lavage fluid, and experienced less severe lung pathology. Our results emphasize the value and versatility of OMV-based vaccine approaches.

Epigenetic regulation of epithelial dectin-1 through an IL-33-STAT3 axis in allergic disease.

Allergic diseases arise in susceptible individuals in part because of decrements in protective pathways. The mechanism by which these anti-inflammatory molecules become repressed remains unclear. We have previously reported that epithelial dectin-1 prevents aberrant type 2 responses and is downregulated in the epithelium of allergic patients. Here, we report that dectin-1 is constitutively expressed by the respiratory epithelium in humans and that IL-33 specifically acts as a repressor of dectin-1. Mechanistically, this occurs via IL-33-dependent STAT3 activation and the subsequent repression of the dectin-1 gene, CLEC7A. We have identified a novel enhancer region upstream of the proximal promoter of CLEC7A that is only accessible in epithelial cells, but not in hematopoietic cells. Epigenetic repression of CLEC7A through this newly identified locus, downstream of an aberrant IL-33-STAT3 axis, occurs in the epithelium of allergic individuals. Collectively, our data identify a mechanism of epigenetic fine-tuning of dectin-1 expression in epithelial cells that may participate in allergenicity.

Deletion of Arno Reduces Eosinophilic Inflammation and Interleukin-5 Expression in a Murine Model of Rhinitis.

BACKGROUND: ARF nucleotide-binding site opener (ARNO) is a guanine nucleotide-exchange factor for ADP-ribosylation factor proteins. ARF nucleotide-binding site opener also binds MyD88, and small-molecule inhibition of ARNO reduces inflammation in animal models of inflammatory arthritis and acute inflammation. However, whether genetic deletion of Arno in mice reduces pathologic inflammation has not yet been reported. Furthermore, its role in the nasal cavity has yet to be investigated. OBJECTIVE: To generate Arno knockout mice and to determine whether genetic loss of ARNO reduces eosinophilic inflammation in the ovalbumin (OVA) murine model of rhinitis. METHODS: Arno knockout mice were generated and wild type and knockout littermates were subjected to the OVA-induced mouse model of rhinosinutitis. Eosinophilic inflammation was assessed through immunofluorescent quantification of EMBP+ eosinophils in the septal mucosa and cytokine expression was assessed by quantitative polymerase chain reaction. RESULTS: Arno knockout mice are viable and fertile without any noted deficits. Arno wild type and knockout mice subjected to the OVA-induced model of rhinitis demonstrated an average of 314.5 and 153.8 EMBP+ cells per mm2 septal tissue, respectively (P < .05). Goblet cells per mm of basal lamina were assessed via Alcian blue and there was no statistically significant difference between Arno wild type and knockout mice. Ovalbumin-induced expression of interleukin-5 (IL-5) was significantly reduced in Arno knockout mice (P < .05). There was no statistically significant reduction in IL-4, IL-13, or eotaxin-1 expression. CONCLUSIONS: These data demonstrate that deletion of Arno reduces eosinophilic inflammation and IL-5 expression in an OVA-induced model of rhinitis.

Taste receptors in chronic rhinosinusitus, what is the evidence? A systematic review.

BACKGROUND: Bitter and sweet taste receptors (T2Rs and T1Rs), respectively, are involved in the innate immune response of the sinonasal cavity and associated with chronic rhinosinusitis (CRS). Growing evidence suggests extraoral TRs as relevant biomarkers, but the current understanding is incomplete. This systematic review synthesizes current evidence of extraoral taste receptors in CRS. METHODS: PubMed, Embase, Cochrane, Web of Science, and Scopus were reviewed in accordance with Preferred Reporting Items for Systemic Reviews and Meta-Analyses guidelines and included studies of genotypic and phenotypic T2R/T1R status in CRS patients. RESULTS: Twenty-two studies with 3845 patients were included. Seventeen studies evaluated genotype and 10 evaluated taste phenotypes. Four of 6 studies examining the haplotype distribution of the T2R, TAS2R38, demonstrated increased AVI/AVI haplotype ("nontaster") frequency in CRS. Meanwhile, 2 studies demonstrated decreased bitter sensitivity in CRS with nasal polyposis (CRSwNP), whereas 3 other studies reported decreased bitter sensitivity only in CRS without nasal polyposis (CRSsNP). Findings regarding sweet sensitivity were mixed. Three studies with cystic fibrosis patients (n = 1393) were included. Studies investigating the association between clinical outcomes and TAS2R38 alleles were limited, but the nonfunctional combination of AVI/AVI was associated with increased utilization of sinus surgery and, in CRSsNP patients, with poorer improvement of symptoms postoperatively. CONCLUSION: Both genotypic and phenotypic assessments of T2Rs suggest a potential association with CRS, particularly CRSsNP. However, limited evidence and mixed conclusions cloud the role of T2Rs in CRS. Future investigations should aim to increase diverse populations, broaden institutional diversity, examine T1Rs, and utilize uniform assessments.