Role of neutrophils in preventing and resolving acute fungal sinusitis

Murine Model of Sinusitis Infection for Screening Antimicrobial and Immunomodulatory Therapies

The very common condition of sinusitis is characterized by persistent inflammation of the nasal cavity, which contributes to chronic rhinosinusitis and morbidity of cystic fibrosis patients. Colonization by opportunistic pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa triggers inflammation that is exacerbated by defects in the innate immune response. Pathophysiological mechanisms underlying initial colonization of the sinuses are not well established. Despite their extensive use, current murine models of acute bacterial rhinosinusitis have not improved the understanding of early disease stages due to analytical limitations. In this study, a model is described that is technically simple, allows non-invasive tracking of bacterial infection, and screening of host-responses to infection and therapies. The model was modified to investigate longer-term infection and disease progression by using a less virulent, epidemic P. aeruginosa cystic fibrosis clinical isolate LESB65. Tracking of luminescent bacteria was possible after intranasal infections, which were sustained for up to 120 h post-infection, without compromising the overall welfare of the host. Production of reactive oxidative species was associated with neutrophil localization to the site of infection in this model. Further, host-defense peptides administered by Respimat® inhaler or intranasal instillation reduced bacterial burden and impacted disease progression as well as cytokine responses associated with rhinosinusitis. Thus, future studies using this model will improve our understanding of rhinosinusitis etiology and early stage pathogenesis, and can be used to screen for the efficacy of emerging therapies pre-clinically.

Acute Invasive Fungal Rhinosinusitis in Immunocompromised Patients: Role of an Early Diagnosis

Objective

The aims of the present study were to evaluate the clinical significance of the delay for surgical treatment and the prognostic value of other clinical, pathologic, and microbiological variables among hematologic patients affected by acute invasive fungal rhinosinusitis (AIFRS). Furthermore, we propose our early diagnosis and treatment protocol, reporting its 10-year results.

Study Design

Monocentric retrospective analysis.

Setting

The study was conducted from 2001 to 2017 at the University Hospital of Bologna, Italy.

Subjects and Methods

The impact of time to treatment and clinical, pathologic, and microbiological variables were analyzed among patients with histologically and microbiologically proven AIFRS. The outcomes of patients treated before the introduction of the early diagnosis protocol were compared with those treated afterward.

Results

Nineteen patients affected by AIFRS were eligible for the study. Treatment delay >4 days ( P = .002), infection caused by Mucorales ( P = .015), and extension of the disease were negative prognostic variables ( P = .017). The application of our protocol significantly reduced the delay for diagnosis and appropriate treatment by an average of 7.3 days ( P = .02).

Conclusion

The promptness of the diagnosis and surgical treatment may play a significant role in the management of AIFRS, as it appears to be significantly associated with the disease outcome. Our protocol may help to reduce the time required for diagnosis of high-risk hematologic patients.

Invasive fungal rhinosinusitis in adult patients: Our experience in diagnosis and management

BACKGROUND

This paper describes our experience in the management of acute and chronic invasive fungal rhinosinusitis (IFRS) in adults.

METHODS

Medical files of all patients aged >18 years treated in our institutions for IFRS from 2002 to 2013 were retrospectively reviewed.

RESULTS

A total of 18 cases (10 acute and 8 chronic) were recorded. In acute form, haematological malignancies represented the principal comorbidity (100%), while in chronic form this was diabetes mellitus (87.5%). All patients received systemic antifungal agents. Endoscopic sinus surgery was performed in 16/18 patients (88.9%). Among patients with an acute IFRS, 4/10 died of fungal infection (40%), on the other side 2/8 patients with chronic IFRS died of the evolution of the mycosis (25%).

CONCLUSIONS

Acute and chronic IFRS are different entities: in acute form, prognosis is poor, so therapy should be promptly performed, although host immune status and evolution of the haematological disease are key factors for the outcome. In chronic form, a wide surgical excision of the disease is recommended in order to obtain a complete removal of fungal infection. In both forms, early clinical findings are non-specific and ambiguous, so diagnosis depends on a high index of suspicion, taking into account predisposing factors.

A novel fungus concentration-dependent rat model for acute invasive fungal rhinosinusitis: an experimental study

Background

Acute invasive fungal rhinosinusitis is a lethal infectious process afflicting immunocompromised individuals. Knowledge about this disease is still limited due to the scarcity of animal models designed to study the pathogenesis of this infection. Mast cells are tissue-resident immune cells that participate in a variety of allergic and inflammatory conditions. Limited attention has been given to the role of mast cells in acute invasive fungal rhinosinusitis. Therefore, the objectives of this study were to create a rat model of acute invasive fungal rhinosinusitis based on analyzing the impact of different fungal concentrations on establishing infection, and to observe the changes of mast cells in rats with this disease.

Methods

Sprague–Dawley rats were divided randomly into four groups, three of which were experimental and received different concentrations of Aspergillus fumigatus inoculations, and one was a control group (D). The inoculated Aspergillus fumigatus concentrations were 5 × 10⁷ conidia/ml in group A, 10⁷ conidia/ml in group B, and 10⁶ conidia/ml in group C. Before fungal inoculation, rats were immunosuppressed using cyclophosphamide and cortisone acetate, and had Merocel sponges inserted into the right nares. Hematology and histopathology investigations were then performed.

Results

An acute invasive fungal rhinosinusitis rat model was established successfully with an incidence rate of 90% in group A, 50% in group B and 10% in group C. Aspergillus fumigatus invasion was observed in 20% of the lungs in group A, but was not seen in the remaining groups. In addition, no fungi invaded the orbital tissue, brains, livers, spleens or kidneys of any rat. Compared with the control set, the total number of mast cells in the experimental groups was not significantly increased, but mast cell degranulation, on the other hand, was only found in infected nasal cavities.

Conclusions

This investigation illustrates that various fungal concentrations have different effects on the incidence of acute invasive fungal rhinosinusitis, and it also demonstrates the feasibility of using this model to study the process of fungal rhinosinusoidal invasion. In addition, the results suggest that mast cells may play a role in the protection of sinuses against acute Aspergillus fumigatus infection and in the clearance of established hyphal masses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0713-y) contains supplementary material, which is available to authorized users.

Overview of vertebrate animal models of fungal infection

Fungi represent emerging infectious threats to human populations worldwide. Mice and other laboratory animals have proved invaluable in modeling clinical syndromes associated with superficial and life-threatening invasive mycoses. This review outlines salient features of common vertebrate animal model systems to study fungal pathogenesis, host antifungal immune responses, and antifungal compounds.

A Novel Model of Invasive Fungal Rhinosinusitis in Rats

Background

Invasive fungal rhinosinusitis (IFRS) is a life-threatening inflammatory disease that affects immunocompromised patients, but animal models of the disease are scarce. This study aimed to develop an IFRS model in neutropenic rats.

Methods

The model was established in three consecutive steps: unilateral nasal obstruction with Merocel sponges, followed by administration of cyclophosphamide (CPA), and, finally, nasal inoculation with Aspergillus fumigatus. Fifty healthy Wistar rats were randomly divided into five groups, with group I as the controls, group II undergoing unilateral nasal obstruction alone, group III undergoing nasal obstruction with fungal inoculation, group IV undergoing nasal obstruction with administration of CPA, and group V undergoing nasal obstruction with administration of CPA and fungal inoculation. Hematology, histology, and mycology investigations were performed.

Results

The changes in the rat absolute neutrophil counts (ANCs) were statistically different across the groups. The administration of CPA decreased the ANCs, whereas nasal obstruction with fungal inoculation increased the ANCs, and nasal obstruction did not change them. Histological examination of the rats in group V revealed the hyphal invasion of sinus mucosa and bone, thrombosis, and tissue infarction. No pathology indicative of IFRS was observed in the remaining groups. Positive rates of fungal culture in tissue homogenates from the maxillary sinus (62.5%) and lung (25%) were found in group V, whereas groups I, II, III, and IV showed no fungal culture in the homogenates.

Conclusion

A rat IFRS model was successfully developed through nasal obstruction, CPA-induced neutropenia, and fungal inoculation. The disease model closely mimics the pathophysiology of anthropic IFRS.

Tracing conidial fate and measuring host cell antifungal activity using a reporter of microbial viability in the lung

Fluorescence can be harnessed to monitor microbial fate and to investigate functional outcomes of individual microbial cell-host cell encounters at portals of entry in native tissue environments. We illustrate this concept by introducing fluorescent Aspergillus reporter (FLARE) conidia that simultaneously report phagocytic uptake and fungal viability during cellular interactions with the murine respiratory innate immune system. Our studies using FLARE conidia reveal stepwise and cell-type-specific requirements for CARD9 and Syk, transducers of C-type lectin receptor and integrin signals, in neutrophil recruitment, conidial uptake, and conidial killing in the lung. By achieving single-event resolution in defined leukocyte populations, the FLARE method enables host cell profiling on the basis of pathogen uptake and killing and may be extended to other pathogens in diverse model host organisms to query molecular, cellular, and pharmacologic mechanisms that shape host-microbe interactions.

Olaryngologic manifestations in children with chronic neutropenia

OBJECTIVE

Chronic neutropenia of childhood (CNC) is a rare disorder in which the absolute neutrophil count is below 1500/μL over an extended period of time. The objective of this study is to describe the otolaryngolgic manifestations associated with CNC to facilitate diagnosis and treatment of this condition.

METHODS AND MATERIALS

We performed a retrospective chart review of patients with the diagnosis of CNC between 1970 and 2005 at a tertiary pediatric hematology center. After Institutional Review Board approval, 43 patients were evaluated. The average age at hematologic diagnosis was 49 months (range: 1 month - 15 years with 35% <1 year, 44% 1-10 years, 21% >10 years). A total of 2049 encounters were analyzed from the hospital charts.

RESULTS

Twenty four subjects (56%) presented with recurrent otitis media (ROM), sinusitis or pharyngo-tonsillitis, while 11% presented with oral mucosal lesions. After diagnosis, otolaryngologic problems persisted, including ROM (81%), viral upper respiratory tract infection (67%), oral ulcers or gingivitis (53%), tonsillitis (39%) and sinusitis (37%) and were more common than other systemic infections. Myringotomy tube placement, endoscopic sinus debridement, adeno-tonsillectomy or tracheostomy were required in 42% of patients. After G-CSF (granulocyte colony-stimulating factor) became available in the early 1990s, the infection rate markedly decreased. Five deaths occurred (12% mortality) including one due to sepsis from otolaryngologic infection.

CONCLUSION

The majority of children with CNC had otolaryngologic problems at presentation and these continued after diagnosis. While managing common otolaryngologic infections in children, a high index of suspicion for chronic neutropenia is necessary. An otolaryngologist is frequently one of the first physicians to encounter children with this condition. Awareness of CNC and its management will enhance earlier diagnosis and more effective treatment for these children.

Coevolution of TH1, TH2, and TH17 responses during repeated pulmonary exposure to Aspergillus fumigatus conidia

Aspergillus fumigatus, a ubiquitous airborne fungus, can cause invasive infection in immunocompromised individuals but also triggers allergic bronchopulmonary aspergillosis in a subset of otherwise healthy individuals repeatedly exposed to the organism. This study addresses a critical gap in our understanding of the immunoregulation in response to repeated exposure to A. fumigatus conidia. C57BL/6 mice were challenged intranasally with A. fumigatus conidia weekly, and leukocyte composition, activation, and cytokine production were examined after two, four, and eight challenges. Approximately 99% of A. fumigatus conidia were cleared within 24 h after inoculation, and repeated exposure to A. fumigatus conidia did not result in hyphal growth or accumulation of conidia with time. After 2 challenges, there was an early influx of neutrophils and regulatory T (T(reg)) cells into the lungs but minimal inflammation. Repeated exposure promoted sustained expansion of the draining lymph nodes, while the influx of eosinophils and other myeloid cells into the lungs peaked after four exposures and then decreased despite continued A. fumigatus challenges. Goblet cell metaplasia and low-level fibrosis were evident during the response. Repeated exposure to A. fumigatus conidia induced T cell activation in the lungs and the codevelopment by four exposures of T(H)1, T(H)2, and T(H)17 responses in the lungs, which were maintained through eight exposures. Changes in CD4 T cell polarization or T(reg) numbers did not account for the reduction in myeloid cell numbers later in the response, suggesting a non-T-cell regulatory pathway involved in dampening inflammation during repeated exposure to A. fumigatus conidia.

Gr-1 antibody induces STAT signaling, macrophage marker expression and abrogation of myeloid-derived suppressor cell activity in BM cells

The Gr-1 (RB6-8C5) Ab binds with high affinity to mouse Ly-6G molecules and to a lower extent to Ly-6C and has been widely used for cell depletion in infected or tumor-bearing mice. Here we found that Gr-1 treatment of BM cells in vitro and in vivo showed no depleting effects. The epitope recognized by the Gr-1 Ab overlapped with Ly-6G (1A8 Ab) but not Ly-6C (ER-MP20 Ab). In vitro the Gr-1 Ab transmitted signals via STAT-1, STAT-3 and STAT-5 into BM cells, similar to GM-CSF. In healthy mice injected with the Gr-1 Ab, the Ab remained attached to the surface of myeloid cells for at least four days. Gr-1 Ab induced myeloid cell expansion, upregulation of macrophage markers, but not the DC marker CD11c. Suppressor activity of two distinct Gr-1(high) and Gr-1(low) expressing BM-myeloid-derived suppressor cell subsets was transiently ablated by Gr-1 Ab injection. Depleting effects of Gr-1 Ab could only be observed on inflammatory Ly-6C(int)Ly-6G(high) neutrophils from the peritoneal cavity, which occurred via apoptosis and was associated with the absence of Mcl-1 expression. Together, Gr-1 Ab induces signals leading to myelopoiesis and affects myeloid-derived suppressor cell activity, suggesting functional roles for Ly-6C/G molecules in macrophage differentiation and neutrophil apoptosis.

Technical advances in rhinologic basic science research

Chronic rhinosinusitis (CRS) is the single most common self-reported chronic health condition in the United States and is estimated to affect 16% of the adult population annually. Despite the prevalence of this disease, there still exists an incomplete understanding of CRS pathophysiology. In this review, the authors highlight technological advances in rhinology: real-time polymerase chain reaction, epithelial cell culture, flow cytometry, genomics/single-nucleotide polymorphism detection, microarrays, and genetic/nongenetic animal models of sinusitis. The purpose of this review is to describe these methodologies and their contributions toward achieving a better understanding of CRS.

Three-dimensional analysis of rodent paranasal sinus cavities from X-ray computed tomography (CT) scans

Continuous isometric microfocal X-ray computed tomography (CT) scans were acquired from an AKR/J mouse, Brown-Norway rat, and Hartley guinea pig. The anatomy and volume of the paranasal sinus cavities were defined from 2-dimensional (2-D) and 3-dimensional (3-D) CT images. Realistic 3-D images were reconstructed and used to determine the anterior maxillary, posterior maxillary, and ethmoid sinus cavity airspace volumes (mouse: 0.6, 0.7, and 0.7 mm(3), rat: 8.6, 7.7, and 7.0 mm(3), guinea pig: 63.5, 46.6 mm(3), and no ethmoid cavity, respectively). The mouse paranasal sinus cavities are similar to the corresponding rat cavities, with a reduction in size, while the corresponding maxillary sinus cavities in the guinea pig are different in size, location, and architecture. Also, the ethmoid sinus cavity is connected by a common drainage pathway to the posterior maxillary sinus in mouse and rat while a similar ethmoid sinus was not present in the guinea pig. We conclude that paranasal sinus cavity airspace opacity (2-D) or volume (3-D) determined by micro-CT scanning may be used to conduct longitudinal studies on the patency of the maxillary sinus cavities of rodents. This represents a potentially useful endpoint for developing and testing drugs in a small animal model of sinusitis.