Serum amyloid A is a soluble pattern recognition receptor that drives type 2 immunity.

The molecular basis for the propensity of a small number of environmental proteins to provoke allergic responses is largely unknown. Herein, we report that mite group 13 allergens of the fatty acid-binding protein (FABP) family are sensed by an evolutionarily conserved acute-phase protein, serum amyloid A1 (SAA1), that promotes pulmonary type 2 immunity. Mechanistically, SAA1 interacted directly with allergenic mite FABPs (Der p 13 and Blo t 13). The interaction between mite FABPs and SAA1 activated the SAA1-binding receptor, formyl peptide receptor 2 (FPR2), which drove the epithelial release of the type-2-promoting cytokine interleukin (IL)-33 in a SAA1-dependent manner. Importantly, the SAA1-FPR2-IL-33 axis was upregulated in nasal epithelial cells from patients with chronic rhinosinusitis. These findings identify an unrecognized role for SAA1 as a soluble pattern recognition receptor for conserved FABPs found in common mite allergens that initiate type 2 immunity at mucosal surfaces.

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.

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.

Benralizumab effect on severe chronic rhinosinusitis with nasal polyps (CRSwNP): A randomized double-blind placebo-controlled trial.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) can be a severe and debilitating disease associated with significant morbidity, loss of smell, sinus pressure and asthma exacerbations. Eosinophils play a role in the majority (85%) of patients. Benralizumab, an afucosylated monoclonal antibody directed against the IL-5 receptor, has powerful apoptotic effects on eosinophils. OBJECTIVE: We sought to investigate the therapeutic benefit of inhibiting the IL-5 receptor using benralizumab to treat severe rhinosinusitis with nasal polyps. METHODS: Patients with severe NP (defined by endoscopic grade 5 or more out of 8) with elevated eosinophils and a history of previous surgical or endoscopic polypectomy met entry criteria and were randomized in a double-blind fashion to receive 30 mg benralizumab SC or placebo. Endoscopic NP score was assessed at baseline and at treatment week 20. CT scan, SNOT-22 survey and UPSIT smell test score changes were also evaluated. RESULTS: Thirty-three patients were screened, and twenty-four (n = 24) were enrolled in the study. Compared with baseline, benralizumab significantly improved NP score (-0.9 ± 0.2, P = 0.004) whereas placebo did not (-0.3 ± 0.3, P = 0.166). Benralizumab induced polyp size reduction compared with placebo did not reach statistical significance (P = 0.103). Five of 12 benralizumab-treated patients (42%) had improvements in all major outcomes (polyp score, CT, SNOT-22 and smell test) versus 2 out of 12 placebo (17%). The ratio of blood eosinophil count to allergen skin test positivity correlated with polyp reduction. CONCLUSION: Benralizumab was well-tolerated and compared with baseline achieved a statistically significant reduction in nasal polyp size, sinus occupancy, symptoms and improved sensation of smell for most patients (83%).

Acute inflammation regulates neuroregeneration through the NF-κB pathway in olfactory epithelium.

Adult neural stem cells/progenitor cells residing in the basal layer of the olfactory epithelium are capable of reconstituting the neuroepithelium even after severe damage. The molecular events underlying this regenerative capacity remain elusive. Here we show that the repair of neuroepithelium after lesioning is accompanied by an acute, but self-limited, inflammatory process. Attenuation of inflammatory cell recruitment and cytokine production by dexamethasone impairs proliferation of progenitor horizontal basal cells (HBCs) and subsequent neuronal differentiation. Using TNF-α receptor-deficient mice, we identify TNF-α signaling as an important contributor to this inflammatory and reparative process, mainly through TNF-α receptor 1. HBC-selective genetic ablation of RelA (p65), the transcriptional activator of the NF-κB pathway, retards inflammation and impedes proliferation at the early stages of regeneration and suggests HBCs directly participate in cross-talk between immune response and neurogenesis. Loss of RelA in the regenerating neuroepithelium perturbs the homeostasis between proliferation and apoptosis while enhancing JNK signaling. Together, our results support a model in which acute inflammation after injury initiates important regenerative signals in part through NF-κB-mediated signaling that activates neural stem cells to reconstitute the olfactory epithelium.

Influenza A Virus M2 Protein Apical Targeting Is Required for Efficient Virus Replication.

The influenza A virus (IAV) M2 protein is a multifunctional protein with critical roles in virion entry, assembly, and budding. M2 is targeted to the apical plasma membrane of polarized epithelial cells, and the interaction of the viral proteins M2, M1, HA, and NA near glycolipid rafts in the apical plasma membrane is hypothesized to coordinate the assembly of infectious virus particles. To determine the role of M2 protein apical targeting in IAV replication, a panel of M2 proteins with basolateral plasma membrane (M2-Baso) or endoplasmic reticulum (M2-ER) targeting sequences was generated. MDCK II cells stably expressing M2-Baso, but not M2-ER, complemented the replication of M2-stop viruses. However, in primary human nasal epithelial cell (hNEC) cultures, viruses encoding M2-Baso and M2-ER replicated to negligible titers compared to those of wild-type virus. M2-Baso replication was negatively correlated with cell polarization. These results demonstrate that M2 apical targeting is essential for IAV replication: targeting M2 to the ER results in a strong, cell type-independent inhibition of virus replication, and targeting M2 to the basolateral membrane has greater effects in hNECs than in MDCK cells.IMPORTANCE Influenza A virus assembly and particle release occur at the apical membrane of polarized epithelial cells. The integral membrane proteins encoded by the virus, HA, NA, and M2, are all targeted to the apical membrane and believed to recruit the other structural proteins to sites of virus assembly. By targeting M2 to the basolateral or endoplasmic reticulum membranes, influenza A virus replication was significantly reduced. Basolateral targeting of M2 reduced the infectious virus titers with minimal effects on virus particle release, while targeting to the endoplasmic reticulum resulted in reduced infectious and total virus particle release. Therefore, altering the expression and the intracellular targeting of M2 has major effects on virus replication.

Temporal instability of the post-surgical maxillary sinus microbiota.

BACKGROUND: Chronic rhinosinusitis is an inflammatory disorder in which the role of bacteria remains uncertain. While sinus outflow obstruction is often an initiating event, mucosal inflammation and dysbiosis may persist or develop in sinuses with widely patent surgical openings. Understanding of the relationship between dysbiosis and chronic sinus inflammation is obfuscated by inter-individual microbiota variability and likely intra-individual temporal variation that has yet to be defined. In this study, long-term microbiota stability is investigated within surgically-opened maxillary sinuses of individuals with and without sinus inflammatory disease. METHODS: Maxillary sinus swabs were performed in 35 subjects with longstanding maxillary antrostomies. Subjects with and without active chronic maxillary sinusitis were included. Repeat swabs were obtained from the same sinuses after a prolonged interval (mean 719 ± 383 days). Patients were categorized based on the inflammatory status of the sinus mucosa at times of sample collection, as assessed by nasal endoscopy. Total DNA from swab eluents was extracted, and the microbiota characterized using 16S rRNA gene sequencing followed by taxonomic classification. Prevalence and abundance of genera were determined by analysis of 16S rRNA gene sequences. Taxa were identified that were stably present between two time points in individual subjects. RESULTS: The overall proportion of stable taxa across time points was 24.5 ± 10.6%. This stability index was consistent across patient groups and not correlated with clinical parameters. Highly prevalent taxa, including Staphylococcus, Corynebacterium, Propionibacterium, and Pseudomonas, were often stably present, but varied in relative abundance. Janthinobacterium, Enterobacter, Lactobacillus, and Acinetobacter were prevalent and moderately abundant taxa in healthy sinuses, but not in inflamed sinuses. Moraxella and Haemophilus were present at low prevalence and proportional abundance in chronically or intermittently inflamed sinuses, but not in healthy sinuses. CONCLUSIONS: A relatively small component of the post-antrostomy maxillary sinus microbiota exhibits long-term stability in individual subjects. Stable bacteria include a limited number of highly prevalent and a larger number of lower prevalence taxa, which vary widely in proportional abundance. The concept of individual-specific core sinus microbiota, durable over time and medical therapy, but fluctuating in proportional abundance, has implications for understanding the role of bacteria in CRS pathogenesis.

Estrogenic compounds reduce influenza A virus replication in primary human nasal epithelial cells derived from female, but not male, donors.

Influenza causes an acute infection characterized by virus replication in respiratory epithelial cells. The severity of influenza and other respiratory diseases changes over the life course and during pregnancy in women, suggesting that sex steroid hormones, such as estrogens, may be involved. Using primary, differentiated human nasal epithelial cell (hNEC) cultures from adult male and female donors, we exposed cultures to the endogenous 17ß-estradiol (E2) or select estrogen receptor modulators (SERMs) and then infected cultures with a seasonal influenza A virus (IAV) to determine whether estrogenic signaling could affect the outcome of IAV infection and whether these effects were sex dependent. Estradiol, raloxifene, and bisphenol A decreased IAV titers in hNECs from female, but not male, donors. The estrogenic decrease in viral titer was dependent on the genomic estrogen receptor-2 (ESR2) as neither genomic ESR1 nor nongenomic GPR30 was expressed in hNEC cultures and addition of the genomic ER antagonist ICI 182,780 reversed the antiviral effects of E2. Treatment of hNECs with E2 had no effect on interferon or chemokine secretion but significantly downregulated cell metabolic processes, including genes that encode for zinc finger proteins, many of which contain estrogen response elements in their promoters. These data provide novel insights into the cellular and molecular mechanisms of how natural and synthetic estrogens impact IAV infection in respiratory epithelial cells derived from humans.

Wnt-responsive Lgr5⁺ globose basal cells function as multipotent olfactory epithelium progenitor cells.

Persistent neurogenesis in the olfactory epithelium provides a unique model to study neural stem cell self-renewal and fate determination. In the olfactory neuroepithelium, globose basal cells (GBCs) are considered to be the direct progenitors of olfactory neurons. However, the study of neurogenesis from GBCs has been impeded by the paucity of GBC-specific markers. Here we report that Lgr5, a recently discovered adult stem cell marker, is exclusively expressed in GBCs in neonatal and adult mice. Lgr5(+) cells display characteristics of cycling stem cells, including Ki67 expression and EdU incorporation. Lineage tracing analysis demonstrates that Lgr5(+) GBCs regenerate multiple cell types under normal turnover condition or after olfactory lesion. Furthermore, upregulation or downregulation of Wnt signaling in vivo indicates a key role of Wnt signaling not only in maintaining Lgr5(+) cell proliferation and promoting neuroregeneration, but also in delaying sensory neuron maturation. Together, our observations provided new insights into the dynamics of neurogenesis in the olfactory epithelium.

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.

The role of revision sinus surgery in the initiation of dupilumab therapy: A real-world study of molecular and cellular features.

KEY POINTS: A persistent type 2 endotype signature exists in recalcitrant chronic rhinosinusitis with nasal polyps mucosa on dupilumab. Revision sinus surgery immediately prior to dupilumab reduces long-term interleukin (IL)-4/IL-13 tissue mRNA. Pre-dupilumab revision surgery is associated with reduced tissue eosinophils and GATA-3+ cells.

Reduced Sense of Smell in Patients with Severe Chronic Rhinosinusitis and its Implications for Diagnosis and Management: A Narrative Review.

Reduced sense of smell is a common symptom in patients with chronic rhinosinusitis (CRS). Although it is often under-diagnosed by healthcare providers, reduced sense of smell can have a substantial negative impact on patient's quality of life as measured by health-related quality of life (HRQoL) assessments and patient-reported outcomes. This narrative review describes current smell loss diagnosis and management guidelines in CRS, and the relationship between smell loss and CRS. Reduced sense of smell can be an indication of CRS disease severity in patients with (CRSwNP) and without nasal polyps (CRSsNP), and recovery of smell can be an indicator of successful CRS treatment. The current first-line therapeutic options for smell loss are intranasal corticosteroids and nasal irrigation, and second-line therapeutic options include systemic steroids and surgery. Shared decision-making between patient, caregiver, and healthcare provider is important when choosing the most appropriate CRS treatment option. Emerging biologic therapies that target type 2 inflammation signaling pathways, such as dupilumab, omalizumab, and mepolizumab, have been shown to improve smell and taste in randomized controlled trials of patients with CRSwNP.A graphical abstract and video abstract are available with this article.

Chronic rhinosinusitis (CRS) is an inflammatory condition often associated with a loss of smell and taste. Patients with CRS and a loss of smell often rate their quality of life as poor and are more likely to also suffer from depression and anxiety than patients without smell loss. Patients with severe smell loss are also more likely to have increased severity of CRS disease by other measures. Standard treatments for smell loss include topical steroids, corticosteroids absorbed into the whole body system (systemic), and/or sinonasal surgery, but the effects may not last, and patients may experience side effects when they use repeated short bursts or long-term treatment with systemic corticosteroids. A newer treatment option for CRS is biologic therapy, which targets the immunologic pathways associated with inflammation. Biologic therapies have been shown to be effective in the treatment of CRS with nasal polyps including improvement in sense of smell. Here, we review the most common diagnostic tests and treatment options for CRS-associated smell loss and show how severity of smell loss is linked to severity of CRS. Supplementary file1 (MP4 60193 kb).

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.

Association Between Smell Loss, Disease Burden, and Dupilumab Efficacy in Chronic Rhinosinusitis with Nasal Polyps.

OBJECTIVE: To evaluate the association between smell loss and other aspects of disease, and evaluate dupilumab efficacy in patients with severe chronic rhinosinusitis with nasal polyps (CRSwNP) and moderate or severe smell loss. METHODS: This post-hoc analysis of the SINUS-24/52 studies (NCT02912468/NCT02898454) analyzed nasal polyp score (NPS, 0-8), nasal congestion/obstruction (NC, 0-3), Lund-Mackay CT-scan score (LMK-CT, 0-24), rhinosinusitis severity visual analog scale (RS-VAS, 0-10), and 22-item Sinonasal Outcome Test (SNOT-22, 0-110) according to baseline monthly average patient-reported loss of smell scores (LoS, 0-3) of >1 to 2 (moderate) or >2 to 3 (severe) in patients randomized to dupilumab 300 mg or placebo every 2 weeks. RESULTS: Of 724 patients randomized, baseline LoS was severe in 601 (83%) and moderate in 106 (15%). At baseline, severe versus moderate LoS was associated with 1-point greater severity of NC (odds ratio [OR] 6.01 [95% confidence interval, (CI) 3.95, 9.15]), 5-point greater severity of LMK-CT (OR 2.19 [1.69, 2.85]), and 8.9-point greater severity of SNOT-22 (OR 1.35 [1.20, 1.49]). At Week 24, least squares mean differences (95% CI) dupilumab versus placebo in change from baseline were: NPS -1.90 (-2.56, -1.25) and -1.95 (-2.20, -1.70) in the moderate and severe baseline LoS subgroups, respectively; NC -.35 (-.64, -.06) and -1.00 (-1.13, -.87); LMK-CT -6.30 (-7.88, -4.72) and -6.22 (-6.82, -5.63); RS-VAS -1.18 (-2.20, -.16) and -3.47 (-3.90, -3.03); and SNOT-22 -7.52 (-14.55, -.48) and -21.72 (-24.63, -18.82); all nominal P < .05 versus placebo. Improvements with dupilumab in NC, RS-VAS, and SNOT-22 were statistically greater in patients with severe versus moderate baseline LoS. CONCLUSION: Significant smell impairment in severe CRSwNP is associated with significant disease (NC, RS-VAS, LMK), health-related quality of life impairment (SNOT-22), asthma, and non-steroidal anti-inflammatory drug-exacerbated respiratory disease. Dupilumab significantly improved NPS, NC, LMK-CT, RS-VAS, and SNOT-22 in subjects with moderate and severe baseline smell loss.

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.