Immunologic response to fungus is not universally associated with rhinosinusitis

Differing rates of fungi in sinonasal cultures from pediatric sinusitis patients

OBJECTIVES

Pediatric chronic rhinosinusitis (PCRS) is a unique clinical entity and the underlying source of inflammation is unknown. Certain subgroups, such as children with nasal polyps and cystic fibrosis (CF) sinusitis are often recalcitrant to standard medical PCRS treatments that target bacterial inflammation. Fungal infection and allergy to fungal proteins drive inflammation in other airway diseases, resulting in chronic inflammation of both the upper and lower airways. However, there is limited understanding of the role of fungi in the pathophysiology of PCRS. The objective of this study is to define the frequency of fungal infection in pediatric CRS patients, hypothesizing that certain subgroups may have more frequent positive fungal sinus cultures than other subgroups of pediatric sinusitis.

METHODS

Retrospective study of patients undergoing sinus surgery at a tertiary care pediatric hospital to determine the period prevalence of positive fungal cultures in subgroups of patients.

RESULTS

400 children from 2012 to 2019 were included. 265 patients had surgical culture results available. Of the 52 patients with CF 11 (21%) had positive fungal sinus cultures. Similarly, 28% of the 25 patients with non-CF nasal polyps had positive cultures. Only 8.2% of 110 CRS without polyps patients had positive cultures, significantly fewer than other subgroups (X² (1, N = 240) = 17.22, p < 0.01).

CONCLUSION

Children with CF and children with nasal polyps had more frequent positive fungal cultures than children without nasal polyps having sinus surgery. This confirms that pediatric CF and pediatric CRS with polyps represent unique populations to study the impact of fungal infection in CRS. Further research is required to determine if these fungi represent colonization or contribute to the inflammatory environment of the airways.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

I.

EXECUTIVE SUMMARY

BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document.

METHODS

ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary.

RESULTS

ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided.

CONCLUSION

This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Chronic Rhinosinusitis and Aspirin-Exacerbated Respiratory Disease

Patients with severe asthma and concomitant chronic rhinosinusitis often have severe, refractory upper and lower airway inflammation. This inflammation has been proposed to be similar throughout the upper and lower airways leading to the unified airways concept. This article reviews chronic rhinosinusitis with and without nasal polyps, and the subgroup with aspirin-exacerbated respiratory disease, while focusing on the relationship with asthma. Additionally, diagnosis and treatment with current and newer therapies are discussed.

Pulmonary and sinus fungal diseases in non-immunocompromised patients

The human respiratory tract is exposed daily to airborne fungi, fungal enzymes, and secondary metabolites. The endemic fungi Histoplasma capsulatum, Coccidioides spp, Blastomyces dermatitidis, and Paracoccidioides brasiliensis, and occasionally Aspergillus fumigatus, are primary pulmonary pathogens of otherwise healthy people. Such infections resolve in most people, and only a few infections lead to disease. However, many fungi are directly allergenic by colonising the respiratory tract or indirectly through contact with cell wall constituents and proteases, causing or exacerbating allergic disease. Increasing evidence implicates high indoor fungal exposures as a precipitant of asthma in children and in worsening asthma symptoms. Lung or airways infection by endemic fungi or aspergillus can be diagnosed with respiratory sample culture or serum IgG testing. Sputum, induced sputum, or bronchial specimens are all suitable specimens for detecting fungi; microscopy, fungal culture, galactomannan antigen, and aspergillus PCR are useful tests. Antifungal treatment is indicated in almost all patients with chronic cavitary pulmonary infections, chronic invasive and granulomatous rhinosinusitis, and aspergillus bronchitis. Most patients with fungal asthma benefit from antifungal therapy. Adverse reactions to oral azoles, drug interactions, and azole resistance in Aspergillus spp limit therapy. Environmental exposures, genetic factors, and structural pulmonary risk factors probably underlie disease but are poorly understood.

Role of tissue eosinophils in chronic rhinosinusitis-associated olfactory loss

BACKGROUND

Olfactory dysfunction is 1 of the hallmark symptoms of chronic rhinosinusitis (CRS). Eosinophilic inflammation has been implicated as a potential causative factor. However, prior studies have been limited by retrospective study designs, concomitant use of systemic corticosteroids, and other confounding factors.

METHODS

CRS and healthy non-CRS control subjects undergoing endoscopic sinus or skull-base surgery were prospectively enrolled and completed olfactory testing utilizing the 40-item Smell Identification Test (SIT) immediately prior to surgery. Histopathological evaluation of tissue excised from the ethmoid bulla was performed by a pathologist in a blinded fashion. Disease severity and patient-reported outcomes were measured via the Lund-Mackay computed tomography (CT) grading system and 22-item Sino-Nasal Outcome Test (SNOT-22), respectively. The associations between olfactory function, tissue eosinophilia, and disease severity were analyzed using Spearman rank order correlation and multiple linear regression.

RESULTS

Twenty-seven (27) subjects with CRS without nasal polyps (CRSsNP), 32 subjects with CRS with nasal polyps (CRSwNP), and 10 healthy non-CRS controls were enrolled. CRSwNP was associated with higher mean tissue eosinophil counts (71.6 vs 28.1 eosinophils/high-power field [HPF], p < 0.05) and lower age/sex-adjusted SIT scores (-17.4 vs -6.2, p < 0.001) when compared to CRSsNP. SIT scores were strongly negatively correlated with tissue eosinophil counts in CRSwNP (r = -0.60, p = 0.0003), but not CRSsNP (r = 0.16, p = 0.42). The correlation between olfactory function and tissue eosinophilia in CRSwNP persisted after adjusting for disease severity.

CONCLUSION

Tissue eosinophilia is associated with olfactory loss in CRSwNP, independent of disease severity. These results suggest a possible role for eosinophils or eosinophil-associated cytokines in CRS-associated olfactory loss.

Drivers of chronic rhinosinusitis: Inflammation versus infection

Studies of the underlying cause or causes of chronic rhinosinusitis (CRS) over the past 20 or more years have expanded from a focus on systemic immune and allergic mechanisms to an intense search for the underlying drivers of mucosal inflammation. These drivers involve mucosal inflammatory pathways that become activated by allergens, microbial stimuli, or poorly understood exogenous or endogenous stimuli. The holy grail in the study of CRS is to identify specific drivers of mucosal inflammation and translate these into more effective treatment for CRS. Certain deficiencies in local innate immunity have been described in patients with CRS that predispose to increased sinus mucosal bacterial colonization/infection, including deficient local production of antimicrobial lactoferrin and deficient functioning of the bitter taste receptor TAS2R38. Conversely, certain innate factors, namely IL-25, IL-33, and thymic stromal lymphopoietin (TSLP), are elaborated by sinus epithelial cells in response to microbial stimulation or airway injury and promote local TH2 inflammation. The precise physiologic role of these factors in innate or adaptive immunity is unclear, although IL-33 might function as an alarmin triggered by damage-associated molecular patterns. The cytokines IL-25 and TSLP, similarly promote proinflammatory tissue responses. Another feature of epithelial dysregulation in patients with CRS is overproduction of eosinophil-promoting C-C chemokines by sinus epithelium, perhaps driven in part through innate stimuli, as well as TH2 cytokines, such as IL-13. Strategies to reduce the microbial stimulation of maladaptive TH2 inflammation or to suppress the local elaboration of TH2-promoting epithelial factors, such as IL-33, have potential therapeutic benefit in patients with CRS, although the extent to which this is realized in patient care remains limited at present. This rostrum will summarize my views on the major microbial drivers of mucosal inflammation and dysregulation of innate TH2-promoting factors in patients with CRS based on recent experimental data.

Pathology of Fungal Rhinosinusitis: A Review

Fungal rhinosinusitis (FRS) comprises a spectrum of disease processes that vary in clinical presentation, histologic appearances, and biological significance. FRS can be acute or chronic and is most commonly classified as non-invasive or invasive based on whether fungi have invaded into tissue. This manuscript will review the pathologic classification of FRS.

The Etiology and Pathogenesis of Chronic Rhinosinusitis: a Review of Current Hypotheses

Chronic rhinosinusitis (CRS) is a broad clinical syndrome that is characterized by prolonged mucosal inflammation of the nose and paranasal sinuses, and is typically divided into two subtypes based on the presence or absence of nasal polyps. The etiology and pathogenesis of both forms remain areas of active research. Over the last 15 years, a number of hypotheses have been proposed to explain all or part of the clinical CRS spectrum. These hypotheses reflect the concept that CRS results from a dysfunctional interplay between individual host characteristics and factors exogenous to the host. Six broad theories on CRS etiology and pathogenesis are discussed as follows: (1) the "fungal hypothesis," (2) the "superantigen hypothesis," (3) the "biofilm hypothesis," and (4) the "microbiome hypothesis," all of which emphasize key environmental factors, and (5) the "eicosanoid hypothesis" and (6) the "immune barrier hypothesis," which describe specific host factors. These theories are reviewed, and the evidence supporting them is critically appraised.

The inflammatory response of eosinophil-related fungal rhinosinusitis varies with inciting fungi

Earlier studies demonstrated immunological response to Alternaria alternata in patients with eosinophil-related fungal rhinosinusitis (FRS). However, Aspergillus flavus rather than A. alternata is predominantly isolated from such patients in Asia. We compared immunological response to A. flavus and A. alternata in our patients with eosinophil related FRS. Total immunoglobulin E, absolute eosinophil count (AEC), cytokine response, and in vitro eosinophil degranulation in the presence of A. flavus/A. alternata were compared among patients with eosinophil-related FRS, non-eosinophilic rhinosinusitis (NECRS), and healthy individuals. Eosinophil-related FRS patients were subgrouped into: Group A - presence of mucin with fungus in tissues and positive immediate hypersensitivity; group B - presence of mucin with fungus in biopsies and no immediate hypersensitivity; and group C - presence of mucin without fungi and hypersensitivity. A. flavus was the predominant (89%) isolate. Significantly higher major basic protein (MBP) was induced by A. flavus in Group A (279.15 ± 32.29 ng/2.5 × 10(5) cells) compared to Group B (254.9 ± 17.14 ng), Group C (238.33 ± 17.56 ng), NECRS (56.96 ± 10.97 ng), and normal subjects (28.73 ± 7.04 ng). A. alternata - eosinophil interaction failed to induce detectable MBP. AEC and serum cytokines, interleukin (IL)- 2, IL-4, IL-5, IL-10, tumor necrosis factor α, and interferon-γ were significantly higher (P < 0.001) in eosinophil-related FRS compared to NECRS and control. Thus a mixed Th1 and Th2 cytokine response was observed in eosinophil-related FRS. In conclusion, immune response in eosinophil-related FRS depends on locally inciting fungi rather than A. alternata in all instances, and the categorization of this group appears to be arbitrary.

ICON: chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a public health problem that has a significant socio-economic impact. Moreover, the complexity of this disease due to its heterogeneous nature based on the underlying pathophysiology - leading to different disease variants - further complicates our understanding and directions for the most appropriate targeted treatment strategies. Several International/national guidelines/position papers and/or consensus documents are available that present the current knowledge and treatment strategies for CRS. Yet there are many challenges to the management of CRS especially in the case of the more severe and refractory forms of disease. Therefore, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), a collaboration between EAACI, AAAAI, ACAAI, and WAO, has decided to propose an International Consensus (ICON) on Chronic Rhinosinusitis. The purpose of this ICON on CRS is to highlight the key common messages from the existing guidelines, the differences in recommendations as well as the gaps in our current knowledge of CRS, thus providing a concise reference. In this document we discuss the definition of the disease, its relevance, pharmacoeconomics, pathophysiology, phenotypes and endotypes, genetics and risk factors, natural history and co-morbidities as well as clinical manifestations and treatment options in both adults and children comprising pharmacotherapy, surgical interventions and more recent biological approaches. Finally, we have also highlighted the unmet needs that wait to be addressed through future research.

The molecular genetics of inflammatory, autoimmune, and infectious diseases of the sinonasal tract: a review

CONTEXT

The sinonasal tract is frequently affected by a variety of nonneoplastic inflammatory disease processes that are often multifactorial in their etiology but commonly have a molecular genetic component.

OBJECTIVE

To review the molecular genetics of a variety of nonneoplastic inflammatory diseases of the sinonasal tract.

DATA SOURCES

Inflammatory lesions of the sinonasal tract can be divided into 3 main categories: (1) chronic rhinosinusitis, (2) infectious diseases, and (3) autoimmune diseases/vasculitides. The molecular diagnosis and pathways of a variety of these inflammatory lesions are currently being elucidated and will shed light on disease pathogenesis and treatment.

CONCLUSIONS

The sinonasal tract is frequently affected by inflammatory lesions that arise through complex interactions of environmental, infectious, and genetic factors. Because these lesions are all inflammatory in nature, the molecular pathology surrounding them is most commonly due to upregulation and down-regulation of genes that affect inflammatory responses and immune regulation.

Fungal extracts detected in eosinophilic chronic rhinosinusitis induced cytokines from the nasal polyp cells

Objectives/Hypothesis

The role of fungi in chronic rhinosinusitis (CRS) is still controversial. The present study was conducted to detect and identify fungal species from the nasal polyp tissues of eosinophilic and noneosinophilic CRS, and to determine the role of fungal antigens in cytokine production.

Study Design

Prospective study.

Methods

Thirty-five specimens of nasal polyps were collected from patients with CRS and examined for fungus using culture, histology, and polymerase chain reaction analysis. The secretion of 14 cytokines stimulated by fungal extracts using dispersed nasal polyp cells (DNPCs) was determined by multiplex immunoassay.

Results

There was no microbiological growth (including fungus) in the cultures of homogenized nasal polyps. Furthermore, Grocott methanamine silver staining for all nasal polyps showed no fungal bodies. Sixteen of 35 samples of the nasal polyps showed amplification of fungal DNA. In none of the mucosa of the sphenoid sinus was fungal DNA detected. The number of eosinophils in the nasal polyps in which fungal DNA was detected was significantly higher than in the nasal polyps in which fungal DNA was not detected (P < .01). The extract of fungus enhanced the secretion of eosinophil-associated cytokines such as interleukine (IL)-5, IL-13, IL-17A, and RANTES (regulated on activation normal T-cell expressed and secreted), and proinflammatory cytokines such as IL-6, IL-8, tumor necrosis factor-α, and granulocyte-macrophage colony-stimulating factor from DNPCs.

Conclusions

The present study offers direct evidence supporting that fungal elements modify the inflammatory response in the nasal polyps of eosinophilic CRS.

Level of Evidence: NA

Host-microbial interactions in patients with chronic rhinosinusitis

There has been considerable investigation of host-microbial interactions in patients with chronic rhinosinusitis (CRS) in hopes of elucidating mechanisms of disease and better treatment. Most attention has been paid to bacterial infection and potential underlying defects in innate immunity. Bacterial biofilm is present in most patients with CRS undergoing surgical intervention, and its presence is associated with more severe disease and worse surgical outcomes. A role for viral or fungal infection in patients with CRS is less clear. There is no evidence for a primary defect in mucociliary clearance in most patients with CRS. Decreased levels of certain antimicrobial proteins, most notably lactoferrin, have been found in sinus secretions, whereas levels of other antimicrobial proteins have been found to be normal. No primary defects in Toll-like receptors have been found in patients with CRS, although a 50% reduced expression of Toll-like receptor 9 was reported in patients with recalcitrant nasal polyps. A polymorphism in a bitter taste receptor was recently associated with refractory CRS and persistent Pseudomonas aeruginosa infection. A downregulation of innate immunity by maladaptive T_H2 tissue inflammation has also been described in patients with recalcitrant nasal polyps, suggesting a link to persistent infection. To date, an effective means of restoring host-microbial balance and mitigating disease in patients with CRS remains elusive.

Role of fungi in the pathophysiology of chronic rhinosinusitis: an update

The pathogenesis of chronic rhinosinusitis (CRS) is multi-factorial with an infectious process likely at least partly involved. While bacteria have been proposed to play a critical role in CRS, fungi have also been implicated by some investigators, although the pathogenesis of fungi in CRS represents a significant controversy among rhinologists. Fungal-associated factors believed to be involved in CRS include the ability of fungi to induce significant inflammatory reactions by different means through inducing localized cytokine production in the sinonasal tract. Despite these observations, randomized, controlled studies on CRS patients using antifungal therapy have not resulted in significant improvement in CRS patients. The role of fungi in the pathogenesis of CRS remains controversial.

Pathophysiology, favoring factors, and associated disorders in otorhinosinusology

The pathogenesis of rhinosinusitis (RS) is related to inflammation, caused by infections in the acute form of the disease but also by other agents in the chronic forms. Cytology allows to evaluate the defensive components, such as hair cells and muciparous cells, while the presence in the nasal mucosa of eosinophils, mast cells, bacteria and/or fungal hyphae, or spores indicates the nasal pathology. The anatomic and physiologic characteristics of the otorhinosinusal system account for the frequent concomitant involvement of the different components. The pivotal pathophysiologic sites are the ostiomeatal complex, the spheno-ethmoidal recess, and the Eustachian tube. The latter is the link with acute otitis media (AOM), which is the most common disease in infants and children and has major medical, social, and economic effects. Moreover, because of the strict relationship between upper and lower airways, nasal sinus disease may contribute to asthma and sinusitis may be considered as an independent factor associated with frequent severe asthma exacerbations. Concerning the role of allergy, the available data do not permit to attribute a central role to atopy in sinusitis and thus allergy testing should not be a routine procedure, while an allergologic evaluation may be indicated in children with OM, especially when they have concomitant rhinitis.

Fungi linking the pathophysiology of chronic rhinosinusitis with nasal polyps and allergic asthma

The immunologic reaction to fungal stimuli has long been thought to be a contributor to the development of sinonasal disease. We aim to review the role of fungi in upper and lower airway inflammatory diseases. The immune response to fungi in the pathogenicity of specific respiratory inflammatory diseases such as allergic bronchopulmonary aspergillosis and a subtype of CRS known as allergic fungal rhinosinusitis has been relatively well described. Fungi are thought to serve both as immunogenic antigens and as adjuncts to inflammation through protease activity. Development of a recent murine mouse model of asthma bypassing the pre-sensitization of allergen further suggests a broader role for fungi in allergic asthma. The literature is lacking in defining a clear presence of fungi within the inflamed sinus cavity of CRS patients and its potential immunologic effects, as well as the utility of antifungal therapy for CRS management. We will review these data and potential common molecular mechanisms activated by fungi in the common pathway toward upper and lower airway inflammatory pathology.

The links between chronic rhinosinusitis and asthma

PURPOSE OF REVIEW

Chronic rhinosinusitis (CRS) and asthma are two leading causes of morbidity with many shared clinical features. Their relationship has initially been linked by the atopic pathway. However, understanding of the true pathophysiology of each of these conditions is still under investigation.

RECENT FINDINGS

Recent studies have described new common pathogens, such as fungi and Staphylococcus aureus, as well as disease biomarkers such as nitric oxide and interleukin (IL)-17A, involved in both asthma and CRS pathophysiology. These new discoveries offer insight into understanding these upper and lower airway diseases and may potentially affect treatment management. In the following review, we intend to provide an overview of the recent developments in the relevant areas of research within the past year.

SUMMARY

Reactions to fungal stimuli and superantigens, as well as biomarkers such as nitric oxide and IL-17A, may play a role in the pathogenesis of asthma and CRS and may explain their historic relationship.

Pathophysiology of Chronic Rhinosinusitis with Nasal Polyp

Background

Chronic rhinosinusitis (CRS) is a common inflammatory condition of the paranasal sinuses and nasal passages. CRS with nasal polyp (CRSwNP) is a subtype of CRS, and the pathogenesis of CRSwNP remains largely unclear.

Methods

This article reviews the literature regarding the pathophysiology of CRSwNP.

Results

Evidence suggests that altered innate immunity, adaptive immunity, tissue remodeling, and/or effects of microorganisms may play a role in the development of CRSwNP. Aberrant arachidonic acid metabolism may also contribute to the pathogenesis of CRSwNP in patients with aspirin-exacerbated respiratory disease.

Conclusion

There have been significant advances in the understanding pathophysiology of CRSwNP. Additional research is needed to elucidate these mechanisms and to determine their relative importance in the pathogenesis of CRSwNP.

Fungus and chronic rhinosinusitis: weighing the evidence

The hypothesis that fungus causes most, if not all, cases of chronic rhinosinusitis (CRS) has been debated for over a decade. Many opinions and interpretations have been rendered, but it is the objective data that speaks the loudest. The debate simply boils down to a core tenet of the scientific method: Can the data be independently replicated? If so, our patients benefit as new treatments are developed. If not, then the hypothesis must be discarded and new lines of research pursued. Initial clinical trials supporting the fungal hypothesis have not been replicated in recent years by independent investigators. An attempt to independently replicate the basic science foundation of this hypothesis has also failed in a more heterogeneous group of CRS patients. The data can be dissected, reanalyzed, and reinterpreted and myriad arguments can be put forth. But an unbiased review of the data demonstrates that nearly every researcher outside of the original proponents of the fungal hypothesis has failed to replicate their work. The weight of the evidence is increasingly tipping the scales away from this theory.

Immunologic response to fungus is not universally associated with chronic rhinosinusitis

In the December 2009 issue of this journal, Orlandi et al presented a study in which peripheral blood mononuclear cells (PBMCs) from chronic rhinosinusitis (CRS) patients (5 from Texas, 5 from Utah) and seven nonhealthy controls were stimulated with fungal extracts. Despite the small numbers, they confirmed important aspects of previous studies: 1) CRS patients' PBMCs react to certain fungal stimuli by producing significantly ( P < 0.05) higher amounts of interleukin (IL)-5 and IL-13 when compared to controls; 2) CRS patients have an enhanced humoral response (significantly elevated immunoglobulin [Ig] G levels to Alternaria); and 3) CRS patients react independently from an IgE-mediated allergy, as evidenced by that fact that nonallergic CRS patients also produced IL-5 in response to fungal stimuli. Unfortunately, the authors chose not to highlight their positive results. They emphasized what they failed to demonstrate, specifically an immune response to fungi above a certain threshold in some patients (Utah) with milder CRS. However, these results are potentially explained by the different methods used, and care should be applied when interpreting their results.

The role of fungus in chronic rhinosinusitis

Fungus has been cited as an etiologic factor (the etiologic factor?) in chronic rhinosinusitis (CRS), and a vigorous debate has ensued. Initial reports of in vitro observations promoted fungus as a potential origin of CRS, yet subsequent clinical trials of topical and systemic antifungal treatments have failed to demonstrate meaningful efficacy. More recent laboratory work has cast significant doubt on the universality of the fungal hypothesis by failing to replicate one of its basic science underpinnings. Combined with clinical data about antifungal therapy's ineffectiveness, these findings appear to tip the scales against fungus as the universal etiology of CRS.