Pathogenesis of chronic rhinosinusitis: role of airborne fungi and bacteria

Rapid Detection and Identification of Antimicrobial Peptide Fingerprints of Nasal Fluid by Mesoporous Silica Particles and MALDI-TOF/TOF Mass Spectrometry: From the Analytical Approach to the Diagnostic Applicability in Precision Medicine

Background: Antimicrobial peptides (AMP) play a pivotal role in innate host defense and in immune response. The delineation of new MS-based profiling tools, which are able to produce panels of AMP of the nasal fluid (NF), may be attractive for the discovery of new potential diagnostic markers of respiratory disorders. Methods: Swabs collected NF from healthy patients and from patients with respiratory disorders. We used a fast procedure based on mesoporous silica particles (MPS) to enrich NF in its AMP component in combination with MALDI-TOF/TOF MS as a key tool for rapidly analyzing clinical samples. Results: Reproducible MS peptide fingerprints were generated for each subject and several AMP were detected including (Human Neutrophil Peptides) HNPs, Statherin, Thymosin-β4, Peptide P-D, II-2, β-MSP, SLPI, Lysozyme-C, and their proteo-forms. In particular, Statherin, Thymosin-β4, and Peptide P-D were accurately identified by direct MS/MS sequencing. Examples of applicability of this tool are shown. AMP fingerprints were obtained before and after a nasal polypectomy as well as before and post-treatment with azelastine/fluticasone in one case of allergic rhinitis. Conclusion: The potential of our platform to be implemented by new mesoporous materials for capturing a wider picture of AMP might offer an amazing opportunity for diagnostic clinical studies on individual and population scales.

Functional outcome after long-term low-dose trimethoprim/sulfamethoxazole in chronic rhinosinusitis with purulence: a prospective study

OBJECTIVE

Trimethoprim/sulfamethoxazole has been suggested as a treatment option for chronic rhinosinusitis with purulence. This study aimed to assess the functional and endoscopic outcomes after a three-month course of low-dose trimethoprim/sulfamethoxazole.

METHODS

A prospective study was performed, comprising patients referred to a tertiary care medical centre with a diagnosis of chronic rhinosinusitis with purulence. Trimethoprim/sulfamethoxazole was prescribed at 960 mg/day for three months. Sinonasal complaints and endoscopic findings were documented, and bacteriological data were compared.

RESULTS

Fifteen patients were included. Staphylococcus aureus was the most common bacterium cultured (86 per cent). Improvement in nasal function, as measured by the 22-item Sino-Nasal Outcome Test, was highly significant at three months (p < 0.0005). This improvement slightly decreased but remained significant at 6, 9 and 12 months. No side effects were noted. Endoscopic scores revealed similar and concordant improvements.

CONCLUSION

Long-term low-dose trimethoprim/sulfamethoxazole therapy seems to be a safe option for selected patients. Additional randomised multicentre studies remain necessary.

Superantigens and Chronic Rhinosinusitis: Skewing of T-Cell Receptor Vβ-Distributions in Polyp-Derived CD4+ and CD8+ T Cells

Background

Recent studies have suggested that Staphylococcus aureus secrete superantigenic toxins that play a role in the etiology of chronic rhinosinusitis with nasal polyposis (CRSwNP). Twenty S. aureus superantigens (SAg's) have been identified, each of which bind the Vβ-region of the T-cell receptor (TCR) outside the peptide-binding site. Approximately 50 distinct Vβ-domains exist in the human repertoire, and distinct SAg's will bind only particular domains generating a pattern of Vβ-enrichment in lymphocytes dependent on the binding characteristics of a given toxin. The aim of this study was to analyze the pattern of Vβ-expression in polyp-derived lymphocytes from CRSwNP patients.

Methods

Polyps were harvested from 20 patients with CRSwNP and 3 patients with antrochoanal polyps. Flow cytometry was used to analyze the Vβ-repertoire of polyp-derived CD4+ and CD8+ lymphocytes. Data were analyzed in light of the known skewing associated with SAg exposure in vivo and in vitro. Skewing was defined as a percentage of Vβ-expression >2 SD of that seen in normal blood.

Results

Seven of 20 subjects exhibited skewing in Vβ-domains with strong associations with S. aureus SAg's. The three antrochoanal polyps failed to show any significant Vβ-skewing.

Conclusion

This study establishes evidence of S. aureus SAg–T-cell interactions in polyp lymphocytes of 35% of CRSwNP patients. Although these results are consistent with intranasal exposure of polyp lymphocytes to SAg's, additional study is necessary to establish the role of these toxins in disease pathogenesis.

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.

Pathogenesis of nasal polyposis

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex inflammatory condition that affects a large proportion of the population world-wide and is associated with high cost of management and significant morbidity. Yet, there is a lack of population-based epidemiologic studies using current definitions of CRSwNP, and the mechanisms that drive pathogenesis in this disease remain unclear. In this review, we summarize the current evidence for the plethora of factors that likely contribute to CRSwNP pathogenesis. Defects in the innate function of the airway epithelial barrier, including diminished expression of antimicrobial products and loss of barrier integrity, combined with colonization by fungi and bacteria likely play a critical role in the development of chronic inflammation in CRSwNP. This chronic inflammation is characterized by elevated expression of many key inflammatory cytokines and chemokines, including IL-5, thymic stromal lymphopoietin and CCL11, that help to initiate and perpetuate this chronic inflammatory response. Together, these factors likely combine to drive the influx of a variety of immune cells, including eosinophils, mast cells, group 2 innate lymphoid cells and lymphocytes, which participate in the chronic inflammatory response within the nasal polyps. Importantly, however, future studies are needed to demonstrate the necessity and sufficiency of these potential drivers of disease in CRSwNP. In addition to the development of new tools and models to aid mechanistic studies, the field of CRSwNP research also needs the type of robust epidemiologic data that has served the asthma community so well. Given the high prevalence, costs and morbidity, there is a great need for continued research into CRS that could facilitate the development of novel therapeutic strategies to improve treatment for patients who suffer from this disease.

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.

Frequency of fungal agents identified in sinus samples from patients with clinically suspected rhinosinusitis

Fungal rhinosinusitis (FRS) is one of the most important rhinosinusoidal disorders, which involves a variety of etiological agents. We carried out a study to determine the frequency of fungal agents in sinus samples from patients with clinically suspected rhinosinusitis (RS). A total of 205 clinical samples were assessed from 174 patients with clinically suspected RS, of which 48 were positive for microscopic examination and culture, 47 were positive for direct examination but negative by culture, 4 were negative for direct examination but positive by culture, and 106 were negative for both methodologies. The main fungal agents isolated were Aspergillus spp. (32.7%), followed by Schizophyllum commune (28.8%). Sensitivity and specificity of the direct examination were 92.3% and 69.3%, respectively, and concordance between the direct examination and culture was 48.4%. This study indicated that both Aspergillus and S. commune appear to be the most important agents involved in the development of FRS.

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.

Medical therapy reduces microbiota diversity and evenness in surgically recalcitrant chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is a highly prevalent and heterogeneous condition frequently treated with antibiotics and corticosteroid therapy. However, the effect of medical therapy on sinus microbiota remains unknown.

METHODS

We enrolled CRS patients (n = 6) with patent maxillary antrostomies and active mucosal inflammation, who had not received antibiotics or corticosteroids in the previous 8 weeks. A pretreatment and posttreatment maxillary sinus swab was collected, from which DNA was extracted, pyrosequenced, and analyzed using a naïve Bayesian classifier and ecological analyses.

RESULTS

Four patients showed significant improvement in endoscopic appearance. The shifts in microbiota in response to therapy were highly individualized. There was no single common microbiota profile among patients with similar clinical outcomes, but overall there was significant decrease in microbiota diversity (t(5) = 2.05, p = 0.10) and evenness (t(5) = 2.28, p = 0.07) after treatment.

CONCLUSION

Our findings strongly correlate with earlier studies that examined the impact of antibiotics on human microbiota. We observed that posttreatment, patients frequently became colonized by taxa that are less susceptible to the prescribed antibiotics. Our findings highlight the challenge in seeking generalizable diagnostic and therapeutic options in CRS, particularly regarding microbiological response and outcomes.

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.

Local IgE-mediated hypersensitivity to Alternaria in pediatric adenoid tissue

OBJECTIVE

Fungus may contribute to the development and exacerbation of allergic airway diseases. Several studies have demonstrated the presence of humoral immune responses to fungi, including Alternaria and Aspergillus, in patients with nasal polyposis, asthma, or rhinitis. The purpose of this study was to evaluate the role of Alternaria- and Aspergillus-specific IgE antibodies in allergic inflammation of adenoid tissue.

METHODS

Thirty-nine atopic subjects who were sensitized to more than one common aeroallergen and 39 non-atopic subjects undergoing adenotonsillectomy were recruited. The Phadia ImmunoCAP was used to quantify total IgE, Alternaria- and Aspergillus-specific IgE, eosinophil cationic protein (ECP), and mast cell tryptase in adenoid tissue homogenates. Alternaria- and Aspergillus-specific IgE were detected in the adenoid tissues from some of the subjects (37.2% and 24.4%, respectively) without systemic sensitization to common airborne fungi.

RESULTS

Both Alternaria- and Aspergillus-specific IgE were more prevalent in adenoid tissues from atopic children (48.7% and 38.5%, respectively) than in tissues from non-atopic children (25.6% and 10.3%, respectively). Subjects with high Alternaria-specific IgE level showed significantly higher serum and adenoid total IgE and adenoid ECP and tryptase than those without specific IgE. Alternaria-specific IgE levels were significantly correlated with serum and adenoid total IgE and with tryptase and ECP levels in adenoid tissue.

CONCLUSIONS

Adenoid tissues from atopic and non-atopic children displayed local IgE-mediated hypersensitivity to fungi in the absence of systemic fungal hypersensitivity. Locally-produced Alternaria-specific IgE may contribute to mast cell and eosinophil activation, especially in the presence of tissue eosinophilia.

Nasal polyposis: current trends

Nasal polyps (NP) are one of the most common inflammatory mass lesions of the nose, affecting up to 4% of the population. They present with nasal obstruction, anosmia, rhinorrhoea, post nasal drip, and less commonly facial pain. Their etiology remains unclear, but they are known to have associations with allergy, asthma, infection, fungus, cystic fibrosis, and aspirin sensitivity. However, the underlying mechanisms interlinking these pathologic conditions to NP formation remain unclear. Also strong genetic factors are implicated in the pathogenesis of NP, but genetic and molecular alterations required for its development and progression are still unclear. Management of NP involves a combination of medical therapy and surgery. There is good evidence for the use of corticosteroids (systemic and topical) both as primary treatment and as postoperative prophylaxis against recurrence, but the prolonged course of the disease and adverse effects of systemic steroids limits their use. Hence several new drugs are under trial. Surgical treatment has been refined significantly over the past 20 years with the advent of endoscopic sinus surgery and, in general, is reserved for cases refractory to medical treatment. Recurrence of the polyposis is common with severe disease recurring in up to 10% of patients. Over the last two decades, increasing insights in the pathophysiology of nasal polyposis opens perspective for new pharmacological treatment options, with eosinophilic inflammation, IgE, fungi and Staphylococcus aureus as potential targets. A better understanding of the pathophysiology underlying the persistent inflammatory state in NP is necessary to ultimately develop novel pharmacotherapeutic approaches. In this paper we present the newer treatment options available for better control and possibly cure of the disease.

Perspectives on the etiology of chronic rhinosinusitis: an immune barrier hypothesis

BACKGROUND

Chronic rhinosinusitis (CRS) has been defined as persistent symptomatic inflammation of the nasal and sinus mucosa resulting from the interaction of multiple host and environmental factors. Recent studies have implicated Alternaria fungi or toxigenic Staphylococcus aureus as critical agents in CRS pathogenesis. The emphasis on environmental agents in CRS etiology has focused interest toward elimination of those agents as the prime mechanism of therapy. This viewpoint is in marked contrast to the current perspective on some other chronic inflammatory epithelial disorders that afflict the skin, lungs, and gut, wherein host factors are believed to predispose to disease expression in the presence of ubiquitous environmental agents.

METHODS

The current review evaluates CRS etiology from this perspective and considers that CRS develops, in part, as an outcome of a dysfunctional host response. Specifically, evidence from our laboratory and others will be reviewed indicating that CRS is associated with a failure of the mechanical and immunologic barriers across the nasal mucosa. The hypothesis would further propose that genetic and epigenetic variation predisposes susceptible individuals to barrier failure in the presence of environmental stress leading to CRS.

RESULTS

From this unifying perspective, bacteria and fungi are seen as disease modifiers rather than primary etiologic agents.

CONCLUSION

The goal is to place concepts of CRS pathophysiology in a framework consistent with a current understanding of chronic inflammation in general and epithelial disease in particular.

Characteristics of recurrent chronic rhinosinusitis after previous surgical therapy

CONCLUSIONS

Our findings emphasize the role of a thorough diagnostic evaluation preoperatively and a targeted long-term medical therapy following any sinonasal surgery for inflammatory disease. Early onset of long-term aspirin desensitization can address a very predominant inflammatory stimulus in a large number of our patients in an effort to prevent recurrent chronic rhinosinusitis (CRS) after successful surgical therapy.

BACKGROUND

Postoperative recurrence of CRS, regardless of the ongoing evolution of diagnostic and surgical techniques, still poses an unsolved problem.

SUBJECTS AND METHODS

This investigation was designed to further characterize the role of aspirin intolerance (AI) and inhalant allergies as persistent inflammatory stimuli in the postoperative period and secondly to analyze the correlation between preoperative computed tomographic (CT) scores and the actual intraoperative findings. A total of 143 patients with recurrent CRS were included in this retrospective analysis, who all underwent revision sinus surgery at our institution after one or multiple previous operations. Charts were analyzed for the incidences of AI and inhalant allergies, CT scores, and intraoperative scores.

RESULTS

In all, 66/143 patients had inhalant allergies and 55/143 were diagnosed with AI. The risk of recurrent CRS was found to be highest in the group with AI, along with the shortest interval between previous surgical interventions and the need for revision. In a subgroup of 34 cases, correlations between CT and intraoperative endoscopy scores were poor in 79%. Interestingly, at the time of recurrence the frontal sinuses were diseased in 17.6% of cases, where they had been healthy at the time of the initial intervention.

Pathogenesis of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a heterogenous disorder and represents a major public health problem. Although insights into the pathophysiology of CRS have largely expanded over the last two decades, the exact etiology and mechanism of persistence is still unrevealed. CRS is a multifactorial disease, and, with variable evidence, impaired ostial patency, mucociliary impairment, allergy, bacterial or fungal infection (or triggering), immunocompromised state, and environmental and genetic factors have been suggested to be associated or risk factors. Pathomechanisms in CRS are better understood currently, allowing us to characterize and differentiate the heterogeneous pathology of chronic sinonasal inflammation based on histopathology, inflammatory pattern, cytokine profile, and remodeling processes. In nasal polyposis (NP), but not CRS without NP, an abundant eosinophilic inflammation and local immunoglobulin E production could be demonstrated, and Staphylococcus-derived superantigens may at least modulate disease severity and expression. These findings question the current assumption that NP is a subgroup of CRS, but suggest that CRS and NP should probably be considered as distinct disease entities.

Fungi in chronic hyperplastic eosinophilic sinusitis: reasonable doubt

Chronic hyperplastic eosinophilic sinusitis (CHES) is a T-helper (Th)2-like, lymphocyteinitiated, eosinophil-rich inflammatory disease. The complex immune interactions required to orchestrate these processes begin with the presentation of antigen by mature dendritic cells to Th lymphocytes that display the appropriate antigen-specific T-cell receptor. The objective of sinus research must be to identify and target that antigen; this will lead to the cure for this condition. This article reviews numerous models that may be responsible for the pathophysiology of this disorder, including putative roles for allergens, bacteria, and bacterial-derived superantigens, as well as recent interest in fungal-derived antigens. Additionally, we speculate that whatever the inciting cause of CHES may be, it is plausible that once initiated, cellular differentiation pathways may lead to the development of an antigen-independent permanent phase. More than one of these may be valid in different subjects and, furthermore, this list almost assuredly does not explain all cases of CHES. The concept that fungal antigens colonizing the sinuses are responsible for CHES represents an intriguing, but unproven, hypothesis. Presently, the case for the fungus remains circumstantial. The case for fungi will be proved only with definitive proof that T-cells within the sinuses are actively responding to fungal antigens present in the sinus and with the further demonstration that removal of those fungal antigens ameliorates the disease.

Chronic rhinosinusitis and superantigens

This article discusses the potential role of bacterial superantigens (SAgs) in chronic rhinosinusitis with nasal polyposis (CRS/NP). First, it briefly describes SAgs, focusing on how they interact with the immune system by binding to T-cell receptors (TCR) and major histocompatibility complex (MHC) class II molecules. Second, it discusses the role of SAgs in other chronic inflammatory diseases.Finally, it presents evidence for the role of SAgs in the pathogenesis and maintenance of CRS/NP focusing on current research and future considerations.

Role of fungus in eosinophilic sinusitis

PURPOSE OF REVIEW

Chronic rhinosinusitis is characterized by a broad diagnostic and etiologic spectrum. It has been postulated that fungal organisms might represent the immunologic target initiating and maintaining the disease process in patients with chronic rhinosinusitis as a common denominator. This review analyzes the available data to describe the current understanding of the role of fungus in the pathophysiology of chronic rhinosinusitis.

RECENT FINDINGS

Recent findings have demonstrated that using highly sensitive methods, the detection rate of fungi in nasal mucin can be increased to approximately 100% in patients and in healthy controls. If this ubiquitous fungal contamination were to be related to a causative mechanism in chronic rhinosinusitis, there would have to be an immunologic sensitization in patients in contrast with healthy individuals, which is yet not fully understood. However, studies were able to demonstrate cytokine production in blood-derived lymphocytes in the presence of fungi in patients, but not in healthy controls. Several questions arise. If this is a relevant finding, in what percentage of chronic rhinosinusitis patients could it be causative? Is chronic rhinosinusitis, then, a systemic disease? How is the extramucosal target in the mucin presented to the immune system? Is intranasal, topical antifungal treatment a successful option?

SUMMARY

The role of fungal organisms in the etiology of eosinophilic rhinosinusitis is reviewed with respect to novel findings, and arising questions are discussed in the light of recent investigations.