Local complement activation in nasal polyposis

The last step to achieve barrier damage control

Heterogeneity characterises inflammatory diseases and different phenotypes and endotypes have been identified. Both innate and adaptive immunity contribute to the immunopathological mechanism of these diseases and barrier damage plays a prominent role triggering type 2 inflammation through the alarmins system, such as anti-Thymic Stromal Lymphopoietin (TSLP). Treatment with anti-TSLP monoclonal antibodies showed efficacy in severe asthma and clinical trials for other eosinophilic diseases are ongoing. The aim of this perspective review is to analyse current advances and future applications of TSLP inhibition to control barrier damage.

Nasal polyp antibody-secreting cells display proliferation signature in aspirin-exacerbated respiratory disease

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) causes nasal obstruction and olfactory dysfunction. Aspirin-exacerbated respiratory disease (AERD) is the triad of CRSwNP, asthma, and respiratory reactions to COX-1 inhibitors. Patients with AERD have elevated nasal IL-5 levels and high numbers of antibody-secreting cells (ASCs), including plasma cells and plasmablasts, in their polyp tissue; in addition, their nasal polyp (NP) IgE levels are correlated with disease severity and recurrence of nasal polyposis.

OBJECTIVE

We sought to explore differences in the transcriptomic profile, activation markers, and IL-5Rα expression and function of NP ASCs from patients with AERD and CRSwNP.

METHODS

NP tissue was collected from patients with AERD and CRSwNP and digested into single-cell suspensions. NP cells were analyzed for protein expression by mass cytometry. For IL-5Rα functional studies, plasma cells were purified and cultured in vitro with or without IL-5 and analyzed by bulk RNA sequencing.

RESULTS

Compared with polyp tissue from patients with CRSwNP, polyp tissue from patients with AERD contained significantly more ASCs and had increased ASC expression of IL-5Rα. ASCs from patients with AERD expressed higher protein levels of B-cell activation and regulatory markers (CD40, CD19, CD32, and CD38) and the proliferation marker Ki-67. ASCs from patients with AERD also expressed more IL5RA, IGHE, and cell cycle- and proliferation-related transcripts (CCND2, MKI67, CDC25A, and CDC25B) than did ASCs from patients with CRSwNP. Stimulation of plasma cells from patients with AERD with IL-5 induced key cell cycle genes (CCND2 and PTP4A3), whereas IL-5 stimulation of ASCs from patients with CRSwNP induced few transcriptomic changes.

CONCLUSION

NP tissue ASCs from patients with AERD express higher levels of functional IL-5Rα and markers associated with cell cycling and proliferation than do ASCs from patients with aspirin-tolerant CRSwNP.

Pathogenesis of Nasal Polyposis: Current Trends

Chronic Rhinosinusitis (CRS) is characterized by edema of the sub-epithelial layers, but, only specific types of CRS are developing polyps. Nasal polyposis may develop under different pathogenetic mechanisms rendering the typical macroscopic classification of CRS, with or without nasal polyps, rather deficient. Currently, we approach nasal polyposis, in terms of diagnosis and treatment, according to its endotype, which means that we focus on the specific cells and cytokines that are participating in its pathogenesis. It appears that the molecular procedures that contribute to polyp formation, initiating with a Th-2 response of the adaptive immune system, are local phenomena occurring in the sub-epithelial layers of the mucosa. Several hypotheses are trying to approach the etiology that drives the immune response towards Th-2 type. Extrinsic factors, like fungi, Staphylococcus superantigens, biofilms, and altered microbiome can contribute to a modified and intense local reaction of the immune system. Some hypotheses based on intrinsic factors like the elimination of Treg lymphocytes, low local vitamin-D levels, high levels of leukotrienes, epithelial to mesenchymal transition (EMT) induced by hypoxia, and altered levels of NO, add pieces to the puzzle of the pathogenesis of nasal polyposis. Currently, the most complete theory is that of epithelial immune barrier dysfunction. Intrinsic and extrinsic conditions can damage the epithelial barrier rendering sub-epithelial layers more vulnerable to invasion by pathogens that trigger a Th-2 response of the adaptive immune system. Th2 cytokines, subsequently, induce the accumulation of eosinophils and IgE together with the remodeling of the stroma in the sub-epithelial layers leading, eventually, to the formation of nasal polyps.

Immunological Aspects of Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is related to persistent inflammation with a dysfunctional relationship between environmental agents and the host immune system. Disturbances in the functioning of the sinus mucosa lead to common clinical symptoms. The major processes involved in the pathogenesis of CRS include airway epithelial dysfunctions that are influenced by external and host-derived factors which activate multiple immunological mechanisms. The molecular bases for CRS remain unclear, although some factors commonly correspond to the disease: bacterial, fungal and viral infections, comorbidity diseases, genetic dysfunctions, and immunodeficiency. Additionally, air pollution leads increased severity of symptoms. CRS is a heterogeneous group of sinus diseases with different clinical courses and response to treatment. Immunological pathways vary depending on the endotype or genotype of the patient. The recent knowledge expansion into mechanisms underlying the pathogenesis of CRS is leading to a steadily increasing significance of precision medicine in the treatment of CRS. The purpose of this review is to summarize the current state of knowledge regarding the immunological aspects of CRS, which are essential for ensuring more effective treatment strategies.

Local Immunoglobulin E in nasal polyps: Role and modulation

In the airway, IgE is traditionally regarded as a key mediator in allergic diseases, such as AR and allergic asthma. However, growing evidence demonstrates the importance of local IgE in airway inflammatory diseases, irrespective of the presence of allergy. In this review, we discuss the most recent evidence for IgE in chronic rhinosinusitis with nasal polyps(CRSwNP), including the local IgE’s characteristics, the modulation of its synthesis, and its function. The levels of local IgE are significantly elevated in polyps independently of IgE serum levels and atopic status. Local IgE, which is correlated with type 2 inflammation, is polyclonal and functional. IgE is produced by active B cells and is dependent on the class switch recombination(CSR). In NPs, this process is triggered by not only allergens but also microbial colonization, especially the superantigen- Staphylococcus aureus. The production of local IgE is modulated by lymphocytes(such as Tfh, ILC2s, iTreg), cytokines(such as IL-4, IL-13, IFN-γ, TGF-β, IL-2, IL-21), transcription factors, and B cell-intrinsic factor. Due to the central role of IgE in NPs, it is regarded as an ideal target for therapy and has been proved to be clinically successful. Based on this knowledge, we believe that exploring the trigger and regulatory factors for the activation of local B cells and CSR to IgE will provide more valuable information for us to recognize the pathological mechanisms of local IgE and offer the possible option for new therapeutic targets of nasal polyps.

Microvessel quantification by fully convolutional neural networks associated with type 2 inflammation in chronic rhinosinusitis

BACKGROUND

The pathogenesis of chronic rhinosinusitis (CRS) is still unclear, and little is known about angiogenesis in this disease. We utilized a fully convolutional network (FCN), which has been extensively used in image processing to study angiogenesis in CRS.

OBJECTIVE

To explore the tissue quantification of microvessels and their potential association with inflammation in CRS by using FCN to reflect the angiogenesis condition in CRS.

METHODS

For endotyping of CRS, tissue homogenates of 79 patients with CRS who had undergone functional endoscopic sinus surgery and 17 control subjects were analyzed for interferon gamma, transforming growth factor beta, interleukin (IL)-1β, IL-5, IL-6, IL-8, IL-10, IL-17, tumor necrosis factor alpha, eosinophilic cationic protein, immunoglobulin E, and Staphylococcus aureus-immunoglobulin E(SE-IgE). A total of 552 hematoxylin and eosin-stained images of 27 CRS tissue samples were used to develop an FCN, going through training, validation, and evaluation processes. An optimized FCN was applied to quantify the microvessels of tissue samples of all subjects. Correlation analysis between microvessel quantification with phenotype, endotype, clinical characteristics, and cytokine expression of CRS was carried out.

RESULTS

Quantification of microvessels in type 2 and non-type 2 CRS demonstrated considerable differences, with a higher expression in type 2 CRS. There was a strong negative correlation between the area ratio of microvessels with tissue tumor necrosis factor alpha and transforming growth factor beta levels and a mildly positive correlation with tissue IL-5 and eosinophilic cationic protein concentration.

CONCLUSION

FCN proved to facilitate the analysis of microvessels in airway tissue samples. This study elucidated the close association of angiogenesis with endotyping, suggesting that treatment aiming at antagonizing angiogenesis may assist to the therapy for the recrudescent and refractory CRS.

Studies of the role of basophils in aspirin-exacerbated respiratory disease pathogenesis

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is characterized by the triad of chronic rhinosinusitis with nasal polyps (CRSwNP), asthma, and intolerance to cyclooxygenase-1 enzyme inhibitors. The underlying mechanisms contributing to AERD pathogenesis are not fully understood, but AERD is characterized by an enhanced type 2 inflammatory phenotype. Basophils are potent type 2 effector cells, but their involvement in AERD pathophysiology remains unclear.

OBJECTIVE

We sought to characterize the systemic and local basophil responses in patients with AERD compared with patients with CRSwNP.

METHODS

Sinonasal tissues including inferior turbinate and/or nasal polyps (NPs) and peripheral blood were collected from controls, patients with AERD, and patients with CRSwNP. Expression of cell surface (CD45, FcεRI, CD203c), activation (CD63), and intracellular (2D7) markers associated with basophils was characterized using flow cytometry. Clinical data including Lund-Mackay scores and pulmonary function were obtained.

RESULTS

The mean number of basophils (CD45⁺CD203c⁺FcεRI⁺CD117^-) detected in AERD NPs (147 ± 28 cells/mg tissue) was significantly elevated compared with that detected in CRSwNP NPs (69 ± 20 cells/mg tissue; P = .01). The number of circulating basophils was significantly elevated in patients with AERD (P = .04). Basophils in NPs had significantly higher CD203c and CD63 mean fluorescence intensity compared with blood in both conditions (P < .01). Basophils from AERD NPs had lower expression of the granule content marker 2D7 compared with those from matched blood (P < .01) or NPs of patients with CRSwNP (P = .06), suggesting ongoing degranulation. Basophil 2D7 mean fluorescence intensity significantly correlated with pulmonary function (r = 0.62; P = .02) and inversely correlated with sinonasal inflammation (r = -0.56; P = .004).

CONCLUSIONS

Increased basophil numbers and extent of ongoing degranulation in NPs of patients with AERD compared with patients with CRSwNP may contribute to the exaggerated disease pathogenesis and severity unique to AERD.

Local immunoglobulin production in nasal tissues: A key to pathogenesis in chronic rhinosinusitis with nasal polyps and aspirin-exacerbated respiratory disease

OBJECTIVE

Local activation of B cells and antibody production are important for protective and pathogenic immune responses. Furthermore, there is evidence that local activation of B cells and antibody production are important for pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) and a severe subset of CRSwNP, aspirin-exacerbated respiratory disease (AERD). This review summarizes these findings and the potential role of B cells and antibodies in disease pathogenesis.

DATA SOURCES

Published literature from PubMed searches.

STUDY SELECTIONS

Studies relevant to B cell development and the roles of B cells and antibodies in the pathogenesis of CRSwNP and AERD.

RESULTS

Formation of tertiary lymphoid structures plays a key role in the local activation of B cells and antibody production. This process is important for fighting infections, but it also contributes to autoimmune disease. Furthermore, there is evidence to support a role for local B cell activation and antibody production in a variety of allergic diseases. Nasal polyp tissues from patients with CRSwNP and AERD have elevated levels of activated B cell subsets and locally produced antibodies. These locally produced antibodies may contribute to disease pathogenesis in a variety of ways, including activation of innate effector cells, whereas locally activated B cells may contribute to pathogenesis through the activation of T cells.

CONCLUSION

More studies are needed to determine the role of B cells and antibodies in driving disease in these patients. However, targeting the processes that drive local B cell activation and antibody production may provide new therapeutic approaches and could help to reduce chronic inflammation.

Linking Complement C3 and B Cells in Nasal Polyposis

Nasal polyposis often is characterized by a persistent inflammation of the sinonasal mucosa, disease recurrence after medical or surgical intervention, and asthma comorbidity. Dysregulated complement activation may contribute to immunologic alterations and disease. To date, there is only scattered knowledge on the source and regulation of the central complement factors in the pathogenesis of nasal polyps. Here, we aim to study complement signatures, especially the C3-C3aR axis, and focus on cellular sources and targets in nasal polyps. Expression of complement factors, including C3, C5, and the anaphylatoxin receptors, was analyzed in nasal polyp tissue samples, the corresponding inferior turbinates, and healthy controls using transcriptomic methods and protein measurements. Distinct patterns of complement expression were found in nasal polyps compared to controls, characterized by an increased C3 activation and an increase in C3aR-bearing cells. In contrast, no difference was shown for epithelial-dependent C3 production. Besides low intracellular C3-expression levels for lymphocytes in general, we could identify an enlarged B lymphocyte population in nasal polyps displaying high amounts of intracellular C3. Our data suggest a prominent role for the C3-C3aR-axis in nasal polyps and, for the first time, describe a B cell population containing high levels of intracellular C3, suggesting a new role of B cells in the maintenance of the inflammation by complement.

Type 2 inflammation in chronic rhinosinusitis without nasal polyps: Another relevant endotype

BACKGROUND

Chronic rhinosinusitis without nasal polyps (CRSsNP) is mainly considered a type 1 mediated disease. The role and clinical significance of type 2 immune responses in CRSsNP have not been addressed sufficiently; a recent cluster analysis for CRS described the existence of a subgroup of patients with CRSsNP with a type 2 inflammation.

OBJECTIVE

We aimed to characterize the underlying type 2 immune response and its clinical significance in patients with CRSsNP.

METHODS

A total of 240 patients with CRSsNP were endotyped and subdivided on the basis of expression of marker cytokines. Clinical data such as recurrence, comorbid asthma and allergy, and numbers of blood eosinophils and neutrophils were collected from all patients. A selection of 15 patients was further characterized for the presence of eosinophils, neutrophils, Charcot-Leyden crystals, and eosinophil extracellular traps in the mucosae.

RESULTS

A type 2 immune response with increased levels of IL-4, IL-5, eosinophil cationic protein, IgE, and Staphylococcus aureus enterotoxin-specific IgE was observed in 49% of patients with CRSsNP. Those patients showed increased numbers of blood and tissue eosinophils, and they displayed a considerable eosinophilic inflammation associated with eosinophil extracellular trap cell death and Charcot-Leyden crystals. A significantly increased prevalence of recurrence and asthma was observed in patients with type 2 CRSsNP compared with in patients with non-type 2 CRSsNP. However, only 4 of 117 patients with type 2 CRSsNP developed nasal polyps within 12 years.

CONCLUSION

This study shows that type 2 immune responses in CRSsNP follow similar patterns but are less pronounced than in chronic rhinosinusitis with nasal polyps. Also CRSsNP with a moderate type 2 immune response showed a considerable eosinophilic inflammation with clinical impact.

IL-5Rα marks nasal polyp IgG4- and IgE-expressing cells in aspirin-exacerbated respiratory disease

BACKGROUND

The cause of severe nasal polyposis in aspirin-exacerbated respiratory disease (AERD) is unknown. Elevated antibody levels have been associated with disease severity in nasal polyps, but upstream drivers of local antibody production in nasal polyps are undetermined.

OBJECTIVE

We sought to identify upstream drivers and phenotypic properties of local antibody-expressing cells in nasal polyps from subjects with AERD.

METHODS

Sinus tissue was obtained from subjects with AERD, chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP), CRS without nasal polyps, and controls without CRS. Tissue antibody levels were quantified via ELISA and immunohistochemistry and were correlated with disease severity. Antibody-expressing cells were profiled with single-cell RNA sequencing, flow cytometry, and immunofluorescence, with IL-5Rα function determined through IL-5 stimulation and subsequent RNA sequencing and quantitative PCR.

RESULTS

Tissue IgE and IgG4 levels were elevated in AERD compared with in controls (P < .01 for IgE and P < .001 for IgG4 vs CRSwNP). Subjects with AERD whose nasal polyps recurred rapidly had higher IgE levels than did subjects with AERD, with slower regrowth (P = .005). Single-cell RNA sequencing revealed increased IL5RA, IGHG4, and IGHE in antibody-expressing cells from patients with AERD compared with antibody-expressing cells from patients with CRSwNP. There were more IL-5Rα⁺ plasma cells in the polyp tissue from those with AERD than in polyp tissue from those with CRSwNP (P = .026). IL-5 stimulation of plasma cells in vitro induced changes in a distinct set of transcripts.

CONCLUSIONS

Our study identifies an increase in antibody-expressing cells in AERD defined by transcript enrichment of IL5RA and IGHG4 or IGHE, with confirmed surface expression of IL-5Rα and functional IL-5 signaling. Tissue IgE and IgG4 levels are elevated in AERD, and higher IgE levels are associated with faster nasal polyp regrowth. Our findings suggest a role for IL-5Rα⁺ antibody-expressing cells in facilitating local antibody production and severe nasal polyps in AERD.

Prognostic Significance of Serum Complement Component 3 in Chronic Rhinosinusitis with Nasal Polyps

OBJECTIVE

The aim of this study was to assess the relationship between serum complement component 3 (C3) levels and disease recurrences in patients with chronic rhinosinusitis with nasal polyps (NPs).

METHODS

Ninety-seven patients with NPs and 30 controls were recruited. Clinical features were collected. Serum concentrations of C3 and C4 were measured before and after endoscopic sinus surgery.

RESULTS

Compared to the controls, increased C3 levels were found in patients with NPs. Patients with polyp recurrences had higher pre- and postoperative serum C3 levels than patients without polyp recurrences. Serum C3 levels dropped after surgery. After polyp regrowth, the mean C3 level in the recurrent group elevated again to the degree similar to that before surgery. When patients were stratified by tissue eosinophilia, no significant difference was seen in pre-/postoperative, absolute change after surgery, and post-recurrent C3 levels between patients without and with eosinophilic NPs in the group with disease recurrences.

CONCLUSION

Serum C3 may be involved in the pathogenesis of NPs. Higher serum C3 levels may pinpoint patients at high risk of recurrence as an independent factor. Furthermore, the change in C3 levels after surgery may have the potential to serve as a predictor for polyp progression. Adding serum C3 measurement to the routine walk-up in the clinical management of NPs is worth further investigation and may help physicians make a more rational diagnostic and/or therapeutic decision regarding this disease.

Multidimensional endotypes of chronic rhinosinusitis and their association with treatment outcomes

BACKGROUND

The expression of chronic rhinosinusitis (CRS) is multidimensional. Disease heterogeneity in patients with CRS remains poorly understood. This study aimed to identify endotypes of CRS using cluster analysis by integrating multidimensional characteristics and to explore their association with treatment outcomes.

METHODS

A total of 28 clinical variables and 39 mucosal cellular and molecular variables were analyzed using principal component analysis. Cluster analysis was performed on 246 prospectively recruited Chinese CRS patients with at least 1-year postoperative follow-up. Difficult-to-treat CRS was characterized in each generated cluster.

RESULTS

Seven subject clusters were identified. Cluster 1 (13.01%) was comparable to the classic well-defined eosinophilic CRS with polyps, having severe disease and the highest proportion of difficult-to-treat CRS. Patients in cluster 2 (16.26%) and cluster 4 (13.82%) had relatively lower proportions of presence of polyps and presented mild inflammation with moderate proportions of difficult-to-treat cases. Subjects in cluster 2 were highly atopic. Cluster 3 (7.31%) and cluster 6 (21.14%) were characterized by severe or moderate neutrophilic inflammation, respectively, and with elevated levels of IL-8 and high proportions of difficult-to-treat CRS. Cluster 5 (4.07%) was a unique group characterized by the highest levels of IL-10 and lacked difficult-to-treat cases. Cluster 7 (24.39%) demonstrated the lowest symptom severity, a low proportion of difficult-to-treat CRS, and low inflammation load. Finally, we found that difficult-to-treat CRS was associated with distinct clinical features and biomarkers in the different clusters.

CONCLUSIONS

Distinct clinicopathobiologic clusters of CRS display differences in clinical response to treatments and characteristics of difficult-to-treat CRS.

A novel multiplex detection array revealed systemic complement activation in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common tumors within the oral cavity. Early diagnosis and prognosis tools are urgently needed. This study aimed to investigate the activation of the complement system in OSCC patients as potential biomarker. Therefore, an innovative complement activation array was developed. Characterized antibodies detecting the complement activation specific epitopes C3a, C5a and sC5b-9 along with control antibodies were implemented into a suspension bead array. Human serum from a healthy (n = 46) and OSCC patient (n = 57) cohort were used to investigate the role of complement activation in oral tumor progression. The novel multiplex assay detected C3a, C5a and sC5b-9 from a minimal sample volume of human tears, aqueous humor and blood samples. Limits of detection were 0.04 ng/mL for C3a, 0.03 ng/mL for C5a and 18.9 ng/mL for sC5b-9, respectively. Biological cut-off levels guaranteed specific detections from serum. The mean serum concentration of a healthy control cohort was 680 ng/mL C3a, 70 ng/mL C5a and 2247 ng/mL sC5b-9, respectively. The assay showed an intra-assay precision of 2.9-6.4% and an inter-assay precision of 9.2-18.2%. Increased systemic C5a (p < 0.0001) and sC5b-9 (p = 0.01) concentrations in OSCC patients were determined using the validated multiplex complement assay. Higher C5a concentrations correlated with tumor differentiation and OSCC extension state. Systemic sC5b-9 determination provided a novel biomarker for infiltrating tumor growth and C3a levels were associated with local tumor spreading. Our study suggests that systemic complement activation levels in OSCC patients may be useful to assess disease progression.

Classical complement pathway activation in the nasal tissue of patients with chronic rhinosinusitis

BACKGROUND

Complement plays a major role in inflammatory diseases, but its involvement and mechanisms of activation in patients with chronic rhinosinusitis (CRS) are not known.

OBJECTIVES

After earlier studies discovering autoantibodies in patients with CRS, we sought to investigate the nature, extent, and location of complement activation in nasal tissue of patients with CRS. Specifically, we were interested in whether antibody-mediated activation through the classical pathway was a major mechanism for complement activation in patients with CRS.

METHODS

Nasal tissue was obtained from patients with CRS and control subjects. Tissue homogenates were analyzed for complement activation products (ELISA-C5b-9, C4d, activated C1, and C5a) and major complement-fixing antibodies (Luminex). Tissue sections were stained for C5b-9, C4d, and laminin. Antibodies were purified with protein A/G columns from nasal polyps (NP), matching patient serum, and control serum and assayed for basement membrane binding by means of ELISA.

RESULTS

C5b-9 levels were significantly increased in NP tissue compared with uncinate tissue (UT) of patients with chronic rhinosinusitis with nasal polyps (CRSwNP) and those with chronic rhinosinusitis without nasal polyps (CRSsNP; P < .01). Similarly, C4d levels were increased in NPs compared with UT of patients with CRSwNP, patients with CRSsNP, and control subjects (P < .05). Activated C1 levels were also increased in NP tissue compared with UT of patients with CRSsNP and control subjects (P < .05) and correlated with levels of C5a (P < .01), local immunoglobulins (especially IgM, P < .0001), and anti-double-stranded DNA IgG (P < .05). Immunofluorescence showed that C5b-9 and C4d deposition occurred linearly along the epithelial basement membrane. NP tissue extracts had significantly more anti-basement membrane antibodies than sera from patients with CRSwNP and control subjects (P < .0001).

CONCLUSION

Levels of C5b-9, C4d, and activated C1 were significantly increased locally in NP tissue. C5b-9 and C4d were almost universally deposited linearly along the basement membrane of NP tissue. Furthermore, activated C1 levels were best correlated with local immunoglobulin and C5a levels. Together, these data suggest that the classical pathway plays a major role in complement activation in patients with CRS.

Neisserial Molecular Adaptations to the Nasopharyngeal Niche

The exclusive reservoir of the genus Neisseria is the human. Of the broad range of species that comprise the Neisseria, only two are frequently pathogenic, and only one of those is a resident of the nasopharynx. Although Neisseria meningitidis can cause severe disease if it invades the bloodstream, the vast majority of interactions between humans and Neisseria are benign, with the bacteria inhabiting its mucosal niche as a non-invasive commensal. Understandably, with the exception of Neisseria gonorrhoeae, which preferentially colonises the urogenital tract, the neisseriae are extremely well adapted to survival in the human nasopharynx, their sole biological niche. The purpose of this review is to provide an overview of the molecular mechanisms evolved by Neisseria to facilitate colonisation and survival within the nasopharynx, focussing on N. meningitidis. The organism has adapted to survive in aerosolised transmission and to attach to mucosal surfaces. It then has to replicate in a nutrition-poor environment and resist immune and competitive pressure within a polymicrobial complex. Temperature and relative gas concentrations (nitric oxide and oxygen) are likely to be potent initial signals of arrival within the nasopharyngeal environment, and this review will focus on how N. meningitidis responds to these to increase the likelihood of its survival.

Outer membrane protein P5 is required for resistance of nontypeable Haemophilus influenzae to both the classical and alternative complement pathways

The complement system is an important first line of defense against the human pathogen Haemophilus influenzae. To survive and propagate in vivo, H. influenzae has evolved mechanisms for subverting this host defense, most of which have been shown to involve outer surface structures, including lipooligosaccharide glycans and outer surface proteins. Bacterial defense against complement acts at multiple steps in the pathway by mechanisms that are not fully understood. Here we identify outer membrane protein P5 as an essential factor in serum resistance of both H. influenzae strain Rd and nontypeable H. influenzae (NTHi) clinical isolate NT127. P5 was essential for resistance of Rd and NT127 to complement in pooled human serum. Further investigation determined that P5 expression decreased cell surface binding of IgM, a potent activator of the classical pathway of complement, to both Rd and NT127. Additionally, P5 expression was required for NT127 to bind factor H (fH), an important inhibitor of alternative pathway (AP) activation. Collectively, the results obtained in this work highlight the ability of H. influenzae to utilize a single protein to perform multiple protective functions for evading host immunity.

Gene expression signatures: a new approach to understanding the pathophysiology of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a complex inflammatory disease with variable disease manifestation. Though external risk factors are associated with development and/or persistence of CRS, the host mucosal response is also important, as nasal epithelium acts as a physical and immune barrier. Under inflammatory stress, the nasal epithelium can undergo injury, followed by a rapid remodeling response ranging from epithelial hyperplasia, to goblet-cell metaplasia, to denudation, loss of cilia, fibrosis, and basement membrane thickening. Identification of gene expression signatures and molecular pathways in CRS pathogenesis have now begun to contribute significantly to a better understanding of the genetic and molecular alterations underlying CRS development and progression. Genetic studies are especially illuminating when multiple gene variants synergize within a permissive environmental context, and are expected to guide development of more effective therapeutic targets for CRS treatment.

Endotypes and phenotypes of chronic rhinosinusitis: a PRACTALL document of the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology

Chronic rhinosinusitis (CRS) is a complex disease consisting of several disease variants with different underlying pathophysiologies. Limited knowledge of the mechanisms of these disease subgroups is possibly the greatest obstacle in understanding the causes of CRS and improving treatment. It is generally agreed that there are clinically relevant CRS phenotypes defined by an observable characteristic or trait, such as the presence or absence of nasal polyps. Defining the phenotype of the patient is useful in making therapeutic decisions. However, clinical phenotypes do not provide full insight into all underlying cellular and molecular pathophysiologic mechanisms of CRS. Recognition of the heterogeneity of CRS has promoted the concept that CRS consists of multiple groups of biological subtypes, or "endotypes," which are defined by distinct pathophysiologic mechanisms that might be identified by corresponding biomarkers. Different CRS endotypes can be characterized by differences in responsiveness to different treatments, including topical intranasal corticosteroids and biological agents, such as anti-IL-5 and anti-IgE mAb, and can be based on different biomarkers that are linked to underlying mechanisms. CRS has been regarded as a single disease entity in clinical and genetic studies in the past, which can explain the failure to identify consistent genetic and environmental correlations. In addition, better identification of endotypes might permit individualization of therapy that can be targeted against the pathophysiologic processes of a patient's endotype, with potential for more effective treatment and better patient outcomes.

Haemophilus influenzae acquires vitronectin via the ubiquitous Protein F to subvert host innate immunity

Acquisition of the complement inhibitor vitronectin (Vn) is important for the respiratory tract pathogen nontypeable Haemophilus influenzae (NTHi) to escape complement-mediated killing. NTHi actively recruits Vn, and we previously showed that this interaction involves Protein E (PE). Here we describe a second Vn-binding protein, a 30 kDa Yersinia YfeA homologue designated as Protein F (PF). An isogenic NTHi 3655Δhpf mutant devoid of PF displayed a reduced binding of Vn, and was consequently more sensitive to killing by human serum compared with the wild type. Surface expression of PF on Escherichia coli conferred binding of Vn that resulted in a serum resistant phenotype. Molecular analyses revealed that the N-terminal of PF (Lys23-Glu48) bound to the C-terminal of Vn (Phe352-Ser374) without disrupting the inhibitory role of Vn on the membrane attack complex. The PF-Vn complex actively delayed C9 deposition on PF-expressing bacteria. Comparative studies of binding affinity and multiple mutants demonstrated that both PE and PF contribute individually to NTHi serum survival. PF was highly conserved and ubiquitously expressed in a series of randomly selected NTHi clinical isolates (n = 18). In conclusion, the multifaceted binding of Vn is beneficial for NTHi survival in serum and may contribute to successful colonization and consequently infection.

Staphylococcus aureus and Chronic Airway Disease

Staphylococcus aureus (S. aureus) is correlated with the development of persistent severe inflammatory disease of the upper airway including chronic rhinosinusitis with nasal polyps. This inflammation of the upper airways is characterized by a T-helper 2-driven disease: interleukin-5 is significantly increased and local production of immunoglobulin E is observed. S. aureus and its enterotoxins are deregulating the tissue inflammation at different levels: structural cells and the innate and adaptive immune system. Knowing the triggers of the pathomechanisms involved will greatly help us to find new therapeutic approaches to resolve this chronic inflammatory process.

Evidence for intranasal antinuclear autoantibodies in patients with chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis (CRS) with nasal polyps is an inflammatory condition of the nasal passage and paranasal sinuses characterized by T(H)2-biased inflammation with increased levels of B-cell activating factor of the TNF family (BAFF), B lymphocytes, and immunoglobulins. Because high levels of BAFF are associated with autoimmune diseases, we assessed for evidence of autoimmunity in patients with CRS.

OBJECTIVES

The objective of this study was to investigate the presence of autoantibodies in sinonasal tissue from patients with CRS.

METHODS

Standardized nasal tissue specimens were collected from patients with CRS and control subjects and assayed for immunoglobulin production, autoantibody levels, tissue distribution of immunoglobulins, and binding potential of antibodies in nasal tissue with a multiplexed autoantibody microarray, ELISA, and immunofluorescence.

RESULTS

Increased levels of several specific autoantibodies were found in nasal polyp tissue in comparison with levels seen in control tissue and inflamed tissue from patients with CRS without nasal polyps (P < .05). In particular, nuclear-targeted autoantibodies, such as anti-dsDNA IgG and IgA antibodies, were found at increased levels in nasal polyps (P < .05) and particularly in nasal polyps from patients requiring revision surgery for recurrence. Direct immunofluorescence staining demonstrated diffuse epithelial and subepithelial deposition of IgG and increased numbers of IgA-secreting plasma cells not seen in control nasal tissue.

CONCLUSIONS

Autoantibodies, particularly those against nuclear antigens, are present at locally increased levels in nasal polyps. The presence of autoantibodies suggests that the microenvironment of a nasal polyp promotes the expansion of self-reactive B-cell clones. Although the pathogenicity of these antibodies remains to be elucidated, the presence of increased anti-dsDNA antibody levels is associated with a clinically more aggressive form of CRS with nasal polyps requiring repeated surgery.

Activation-induced cytidine deaminase (AID)-associated multigene signature to assess impact of AID in etiology of diseases with inflammatory component

Activation-induced cytidine deaminase (AID) is expressed in B cells within germinal centers and is critically involved in class switch recombination and somatic hypermutation of immunoglobulin loci. Functionally active AID can additionally be detected within ectopic follicular structures developed at sites of chronic inflammation. Furthermore, AID may target non-Ig genes in B- and non-B-cell background. Therefore, AID-associated effects are of increasing interest in disease areas such as allergy, inflammation, autoimmunity, and cancer.Pathway- or disease-relevant multigene signatures have attracted substantial attention for therapeutic target proposal, diagnostic tools, and monitoring of therapy response. To delineate the impact of AID in etiology of multifactorial diseases, we designed the AID-associated 25-gene signature. Chronic rhinosinusitis with nasal polyps was used as an inflammation-driven airway disease model; high levels of IgE have been previously shown to be present within polyp tissue. Expression levels of 16 genes were found to be modulated in polyps including AID, IgG and IgE mature transcripts which reflect AID activity; clustering algorithm revealed an AID-specific gene signature for the disease state with nasal polyp. Complementary, AID-positive ectopic lymphoid structures were detected within polyp tissues by in situ immunostaining. Our data demonstrate the class switch recombination and somatic hypermutation events likely taking place locally in the airways and in addition to the previously highlighted markers and/or targets as IL5 and IgE suggest novel candidate genes to be considered for treatment of nasal polyposis including among others IL13 and CD23. Thus, the algorithm presented herein including the multigene signature approach, analysis of co-regularities and creation of AID-associated functional network gives an integrated view of biological processes and might be further applied to assess role of altered AID expression in etiology of other diseases, in particular, aberrant immunity and cancer.

Association analysis of C6 genetic variations and aspirin hypersensitivity in Korean asthmatic patients

There has been increasing evidence that genetic mechanisms contribute to the development of aspirin-intolerant asthma (AIA), a life-threatening disease. The complement component (C6) is a constituent of a biochemical cascade that has been implicated in airway epithelial damage and nasal polyposis, and therefore, may be a risk factor for AIA. To investigate the association between C6 variations and AIA in a Korean asthma cohort, 27 SNPs were selected for genotyping based on previously reported polymorphisms in the HapMap database. Genotyping was carried out using TaqMan assay, and five major haplotypes were obtained in 163 AIA cases and 429 aspirin-tolerant asthma (ATA) controls subjects. Genotype frequency distributions of C6 polymorphisms and haplotypes were analyzed using logistic and regression models. Subsequent analyses revealed a lack of association between C6 genetic variations and AIA. From the initial analyses, marginal associations of rs10512766 (p = 0.04 in co-dominant model) and rs4957374 (p = 0.05 in dominant model) with AIA did not reach the threshold of significance after multiple testing corrections; thus this study failed to find convincing evidence that variations in C6 gene influence the risk of AIA in a Korean population. However, these preliminary results may contribute to the etiology of aspirin hypersensitivity in Korean asthmatic patients.

Haemophilus influenzae and the complement system

The respiratory tract pathogen Haemophilus influenzae is responsible for a variety of infections in humans including septicemia, bronchitis, pneumonia, and acute otitis media. The pathogenesis of H. influenzae relies on its capacity to resist human host defenses including the complement system, and thus H. influenzae has developed several efficient strategies to circumvent complement attack. In addition to attracting specific host complement regulators directly to the bacterial surface, the capsule, lipooligosaccharides, and several outer membrane proteins contribute to resistance against complement-mediated attacks and hence increased bacterial survival. Insights into the mechanisms of complement evasion by H. influenzae are important for understanding pathogenesis and for developing vaccines and new therapies aimed at patients with, for example, chronic obstructive pulmonary disease. Here we overview current knowledge on the different mechanisms by which H. influenzae evades attack by the host complement system.