Interleukin 18 participates in the early inflammatory response and bacterial clearance during pneumonia caused by nontypeable Haemophilus influenzae

A rapid triage test for active pulmonary tuberculosis in adult patients with persistent cough

Improved tuberculosis (TB) prevention and control depend critically on the development of a simple, readily accessible rapid triage test to stratify TB risk. We hypothesized that a blood protein-based host response signature for active TB (ATB) could distinguish it from other TB-like disease (OTD) in adult patients with persistent cough, thereby providing a foundation for a point-of-care (POC) triage test for ATB. Three adult cohorts consisting of ATB suspects were recruited. A bead-based immunoassay and machine learning algorithms identified a panel of four host blood proteins, interleukin-6 (IL-6), IL-8, IL-18, and vascular endothelial growth factor (VEGF), that distinguished ATB from OTD. An ultrasensitive POC-amenable single-molecule array (Simoa) panel was configured, and the ATB diagnostic algorithm underwent blind validation in an independent, multinational cohort in which ATB was distinguished from OTD with receiver operator characteristic-area under the curve (ROC-AUC) of 0.80 [95% confidence interval (CI), 0.75 to 0.85], 80% sensitivity (95% CI, 73 to 85%), and 65% specificity (95% CI, 57 to 71%). When host antibodies against TB antigen Ag85B were added to the panel, performance improved to 86% sensitivity and 69% specificity. A blood-based host response panel consisting of four proteins and antibodies to one TB antigen can help to differentiate ATB from other causes of persistent cough in patients with and without HIV infection from Africa, Asia, and South America. Performance characteristics approach World Health Organization (WHO) target product profile accuracy requirements and may provide the foundation for an urgently needed blood-based POC TB triage test.

Cytokine responses to two common respiratory pathogens in children are dependent on interleukin-1β

Protracted bacterial bronchitis (PBB) in young children is a common cause of prolonged wet cough and may be a precursor to bronchiectasis in some children. Although PBB and bronchiectasis are both characterised by neutrophilic airway inflammation and a prominent interleukin (IL)-1β signature, the contribution of the IL-1β pathway to host defence is not clear. This study aimed to compare systemic immune responses against common pathogens in children with PBB, bronchiectasis and control children and to determine the importance of the IL-1β pathway. Non-typeable Haemophilus influenzae (NTHi) stimulation of peripheral blood mononuclear cells (PBMCs) from control subjects (n=20), those with recurrent PBB (n=20) and bronchiectasis (n=20) induced high concentrations of IL-1β, IL-6, interferon (IFN)-γ and IL-10. Blocking with an IL-1 receptor antagonist (IL-1Ra) modified the cellular response to pathogens, inhibiting cytokine synthesis by NTHi-stimulated PBMCs and rhinovirus-stimulated PBMCs (in a separate PBB cohort). Inhibition of IFN-γ production by IL-1Ra was observed across multiple cell types, including CD3⁺ T cells and CD56⁺ NK cells. Our findings highlight the extent to which IL-1β regulates the cellular immune response against two common respiratory pathogens. While blocking the IL-1β pathway has the potential to reduce inflammation, this may come at the cost of protective immunity against NTHi and rhinovirus.

Treating neutrophilic inflammation in COPD by targeting ALX/FPR2 resolution pathways

Neutrophilic inflammation persists in COPD despite best current therapies and it is particularly resistant to inhaled glucocorticosteroids. Persistent neutrophil activation not only contributes to matrix breakdown, but can maintain inflammation through the release of endogenous damage associated molecule patterns (DAMPs). Inhibiting excessive neutrophilic inflammation is challenging as many pathogen recognition receptors can initiate migration and the targeting of downstream signaling molecules may compromise essential host defense mechanisms. Here, we discuss new strategies to combat this inflammation in COPD by focusing on the anti-inflammatory role of ALX/FPR2 receptors. ALX/FPR2 is a promiscuous G-protein coupled receptor (GPCR) responding to lipid and peptide agonists that can either switch on acute inflammation or promote resolution of inflammation. We highlight this receptor as an emerging target in the pathogenesis of COPD because known ALX/FPR2 endogenous agonists are enriched in COPD. Serum Amyloid A (SAA) has recently been discovered to be abundantly expressed in COPD and is a potent ALX/FPR2 agonist that unlike almost all other inflammatory chemoattractants, is induced by glucocorticosteroids. SAA not only initiates lung inflammation via ALX/FPR2 but can allosterically modify this receptor so that it no longer transduces pro-resolving signals from endogenous lipoxins that would otherwise promote tissue healing. We propose that there is an imbalance in endogenous and microbial ALX/FPR2 receptor agonists in the inflamed COPD lung environment that oppose protective anti-inflammatory and pro-resolution pathways. These insights open the possibility of targeting ALX/FPR2 receptors using synthetic agonists to resolve persistent neutrophilic inflammation without compromising essential host defense mechanisms.

Interleukin-18 is up-regulated in infectious pleural effusions

The aim of this study was to investigate the pleural and systemic expression of interleukin-18 (IL-18) in patients with pleural effusions (PEs), and the effects of the cytokine in mouse pleural space. One hundred and sixty patients, 23 with pleural effusions (PEs) due to heart failure, 60 malignant, 25 parapneumonic/empyemas, 15 tuberculous and 37 with exudates of miscellaneous etiologies were included in the study. Pleural fluid (PF) and serum IL-18 content was determined using ELISA. IL-18 was injected intrapleurally in mice and pleural inflammation was assessed using pleural lavage. The highest PF IL-18 levels were observed in parapneumonic PEs and the lowest PF IL-18 levels in patients with exudates of miscellaneous aetiologies and transudates. PF IL-18 levels were significantly higher in patients with empyemas compared to those with uncomplicated (p=0.009) or complicated (p=0.028) parapneumonic effusions, while serum levels did not differ significantly among the three groups. Pleural IL-18 content was higher than that of blood only in patients with empyemas. In patients with pleural exudates of all etiologies and in those with parapneumonic PEs/empyema, PF IL-18 levels were correlated with markers of acute pleural inflammation such as the percentage of PF neutrophils, PF LDH and PF/serum LDH ratio, low PF glucose and PF/serum glucose ratio and low PF pH. In mice, intrapleural IL-18 caused neutrophil-predominant pleural inflammation. In conclusion, IL-18 is linked to the intensity of neutrophilic pleural inflammation in patients with PEs, it is up-regulated in the pleural space of patients with empyema and it stimulates the accumulation of neutrophils in mouse pleura.

Decreased interleukin-18 response in asthmatic children with severe Mycoplasma pneumoniae pneumonia

Purpose

Mycoplasma pneumoniae (M. pneumoniae) is a common causative agent of pneumonia in children. The aim of this study is to determine whether there is any difference in selected cytokine or chemokines response in asthmatic children compared to non-asthmatic children during acute M. pneumoniae pneumonia.

Methods

Seventy-five children, 6–12 years of age, admitted with M. pneumoniae pneumonia were enrolled. Two patient groups were defined: the children with known asthma (N = 40) and non-asthmatic children (N = 35). Interleukin (IL)-18 and selected chemokines, IL-8, CXCL9, CXCL10, and regulation upon activation normal T-cell expressed and secreted (RANTES) were measured by means of ELISA in the plasma samples of the patients collected on admission. We investigated the values of these mediators in relation to the asthma status and symptom severity of the patients. Twenty age-matched, non-infected controls were also studied.

Results

Plasma levels of IL-18 and the chemokines increased significantly in the patients with M. pneumoniae pneumonia compared to non-infected, age-matched controls (P < 0.01). However, the asthmatic patients showed significantly reduced IL-18 and CXCL10 responses (P < 0.01, <0.05, respectively) and had more severe pneumonia symptoms (P < 0.01) compared to non-asthmatic patients. IL-18 was significantly lower in severe pneumonia group than in non-severe group (P < 0.05).

Conclusions

Our study suggests that IL-18 and the chemokines are importantly involved in the pathogenesis of M. pneumoniae pneumonia. It also indicates that some asthmatic children have deficient IL-18 response when affected by M. pneumoniae pneumonia, which might be associated with more severe pneumonia observed in this group of patients.

Toll-like receptor 9 is not important for host defense against Haemophilus influenzae

Non-typeable Haemophilus influenzae (NTHi) is a common Gram-negative respiratory pathogen. We demonstrated previously that myeloid differentiation primary-response protein 88 (MyD88) is of utmost importance in host defense against NTHi. All TLRs except for TLR3 depend on MyD88 for signaling. TLR9, the TLR for detecting pathogen DNA depends on MyD88 signaling. Here, we investigate the role of TLR9 during NTHi pneumonia. Alveolar macrophages (AM) from normal wild-type (WT) and TLR9 knock-out (KO) mice were harvested and stimulated with growth-arrested NTHi or CPG DNA. WT and TLR9 KO mice were infected intranasally with NTHi: cytokine and chemokine responses were measured 16h later. Despite significant reduced TNF production by TLR9 KO AM in response to CPG DNA, no difference was detected in TNF production after NTHi stimulation by isolated alveolar macrophages from WT and TLR9 KO mice. Moreover, we found similar pulmonary bacterial loads, similar cytokine and chemokine levels in WT and TLR9 KO mice, and no differences in histopathology. In conclusion, we were not able to demonstrate a role for TLR9 in the recognition of and host defense against NTHi.

Global and gene-specific translational regulation in rat lung development

During the peripartum period, the lung must respond to dramatic changes in circulating hormones, nutritional factors, and physiologic signals during its transition to becoming the organ of gas exchange. Protein synthesis consumes a significant proportion of metabolic resources and is inhibited by many environmental stresses. We hypothesized that translational control mechanisms play a role in the perinatal lung. Immunoblots of late-gestation (Fetal Day [FD] 17-22) rat lung extracts revealed gradual decreases in phosphorylated forms of the mammalian target of rapamycin effectors, eukaryotic initiation factor (eIF) 4E-binding protein, p70 S6 kinase, and ribosomal protein S6, followed by sharp increases on Postnatal Day 1 (P1). Immunohistochemistry showed phospho-S6 staining was most prominent in epithelial cells of the large and small airways. m(7)GTP-sepharose pulldown experiments showed a decrease in association of translation initiation factor, eIF4E, with its inhibitor, eIF4E-binding protein, and a concomitant increase in eIF4E association with eIF4G immediately after birth, and polysome profiles confirmed a decrease in abundance of large polysomes between FD19 and FD22, which was reversed on P1. Microarray analysis of polysomal versus total RNA from FD19, FD22, and P1 lungs was used to identify specific genes, the association of which with large polysomes changed either pre- or postnatally. RT-PCR and Northern blotting were used to confirm translational changes in selected candidate genes, including a prenatal increase in IL-18 and a postnatal decrease in regulatory subunit 2 of protein phosphatase 1. Translational regulation of IL-18 and protein phosphatase 1 regulatory (inhibitor) subunit 2 is gene-specific, as these changes contrast with the corresponding global changes in polysome abundance.