Inhaled Cryptococcus neoformans elicits allergic airway inflammation independent of Nuclear Factor Kappa B signalling in lung epithelial cells

Abstract

Pulmonary challenge with the ubiquitous fungus Cryptococcus neoformans results in allergic airway inflammation (AAI) characterized by robust recruitment of eosinophils and T cells producing type 2 cytokines to the lungs. Previous studies have demonstrated a critical role for Nuclear Factor Kappa B (NF-κB) activation within lung epithelial cells (LECs) in driving AAI in response to protein allergens, yet the role of LEC-intrinsic NF-κB in promoting AAI following exposure to C. neoformans is poorly understood. To investigate the role of LEC-intrinsic NF-κB in promoting AAI following C. neoformans challenge, we used IKK mice, which lack canonical NF-κB activation specifically within LECs. IKK and littermate control mice were intranasally challenged with 10 CFU of C. neoformans strain 52D, and lung tissues were collected at 7, 14 and 21 days post infection to assess the development of AAI. Notably, the absence of epithelial NF-κB signalling did not affect the magnitude or kinetics of lung eosinophilia when compared with the response in wild-type control mice. The total numbers of lung T cells producing the type 2 cytokines interleukin-5 and interleukin-13 were also unchanged in IKK mice. Furthermore, IKK mice showed no defect in the recruitment of protective interferon-γ-producing CD4 T cells to the lungs, fungal clearance, or host survival compared with control mice. Immunofluorescence imaging surprisingly revealed no evidence of nuclear localization of NF-κB in LECs in response to C. neoformans challenge, indicating that NF-κB is not activated within these cells. Taken together, these data strongly suggest that NF-κB signalling within LECs does not promote AAI observed in response to C. neoformans.

Infectious particle identity determines dissemination and disease outcome for the inhaled human fungal pathogen Cryptococcus

“…A protocol of surface staining for flow cytometric analysis was carried out as described previously [43,44,46,47] with minor modifications. Single cell suspensions were first stained with 1:250 fixable Live/Dead (near IR), then incubated with unlabeled FcRIII/II to block Fc receptors and subsequently stained with 1:200 dilutions of fluorescently labeled antibodies (CD45, SiglecF, CD11b, CD11c, Ly6G, Ly6C, MHCII) for 30 minutes at 4°C, resuspended in 2% paraformaldehyde and stored at 4°C protected from light until acquisition.…”

Helper T‐cell responses and pulmonary fungal infections

“…Monocyte‐derived macrophages and dendritic cells are often recruited into the airway . Likewise, other myeloid cell populations, including neutrophils, monocytes and eosinophils, infiltrate the airways in an effort to combat the infection. In almost all cases of pulmonary fungal infection, the development of adaptive immunity and the engagement of CD4 T‐cell help is a key determinant of the outcome on infection.…”

Pulmonary Fibrosis and Hypereosinophilia in TLR9-/- Mice Infected by Cryptococcus gattii

“…[24,25,29,30]. Pulmonary eosinophilia caused by cryptococcal infection has been associated with inefficiency in controlling or resolving the pulmonary infection, culminating in a Th2 allergic response [29][30][31]. Although C. gattii-infected WT mice had chronic cryptococcal pneumonia and pulmonary eosinophilia 21 days after inoculum, we found hypereosinophilia in TLR9 -/pulmonary mixed infiltrate.…”

“…Many works have demonstrated that cryptococcal pneumonia leads to an intense and prolonged pulmonary Th2 inflammatory response. The "allergy" response is like other chronicle inflammatory diseases, such as asthma and allergic bronchopulmonary mycosis (ABPM) [29][30][31][32].…”