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Chemerin is an atypical chemokine first described as a chemoattractant agent for monocytes, natural killer cells, plasmacytoid and myeloid dendritic cells, through interaction with its main receptor, the G protein-coupled receptor chemokine-like receptor 1 (CMKLR1). Chemerin has been studied in various lung disease models, showing both pro- and anti-inflammatory properties. Given the incidence and burden of inflammatory lung diseases from diverse origins (infectious, autoimmune, age-related, etc.), chemerin has emerged as an interesting therapeutical target due to its immunomodulatory role. However, as highlighted by this review, further research efforts to elucidate the mechanisms governing chemerin’s dual pro- and anti-inflammatory characteristics are urgently needed. Moreover, although a growing body of evidence suggests chemerin as a potential biomarker for the diagnosis and/or prognosis of inflammatory lung diseases, this review underscores the necessity for standardizing both sampling types and measurement techniques before drawing definitive conclusions.

Background With the increasing use of low dose CT scans, numerous pulmonary nodules are detected. As majority of them are benign, development of efficient non-surgical diagnostic intervention is mandatory. Electromagnetic navigation bronchoscopy (ENB) has been developed to reach difficult to access lesions. The aim of the present study was to compare the diagnostic yield of ENB procedures performed in a classical endoscopy suite or in a hybrid room equipped by a cone beam CT (CBCT). Methods A monocentric randomized study was performed in the Erasme Hospital between January 2020 and December 2021. Lung nodules of maximum 30 mm of diameter were eligible. In both arms (endoscopy or CBCT suites), ENB, fluoroscopic guidance and a radial endobronchial ultrasound were used to reach the lesion. Then six trans-bronchial biopsies (TBB) and one trans-bronchial lung cryobiopsy (TBLC) were performed. Primary outcomes were the diagnostic yield and diagnostic accuracy of the procedure. Results Forty-nine patients were randomized (24 in the endoscopy and 25 in the CBCT arms). The lesion size was 15,9 ± 4,6 mm and 16,6 ± 6,0 mm respectively (mean ± SD, p  = NS). The diagnostic yield of ENB performed under CBCT guidance was 80% compared to 42% when performed in the endoscopy suite under standard fluoroscopic guidance ( p  < 0,05). Similarly, the diagnostic accuracy in the CBCT group was 87% compared to 54% for the endoscopy group ( p  < 0,05). Duration of the procedure in the CBCT and endoscopy arms was 80 ± 23 and 61 ± 13 min respectively (mean ± SD, p  < 0,01). Performing TBLC in addition to TBB increased the diagnostic yield by 14% (17 and 12,5% in CBCT and endoscopy suites respectively, p  = NS). Conclusion This study highlighted the additional value to perform ENB procedure under CBCT guidance for small size (less than 2 cm of diameter) pulmonary nodules. Trial registration Clinical trial registration number: NCT05257382.

Idiopathic pulmonary fibrosis (IPF) is a rare, chronic, and progressive interstitial lung disease with an average survival of approximately 3 years. The evolution of IPF is unpredictable, with some patients presenting a relatively stable condition with limited progression over time, whereas others deteriorate rapidly. In addition to IPF, other interstitial lung diseases can lead to pulmonary fibrosis, and up to a third have a progressive phenotype with the same prognosis as IPF. Clinical, biological, and radiological risk factors of progression were identified, but no specific biomarkers of fibrogenesis are currently available. A recent interest in the fibroblast activation protein alpha (FAPα) has emerged. FAPα is a transmembrane serine protease with extracellular activity. It can also be found in a soluble form, also named anti-plasmin cleaving enzyme (APCE). FAPα is specifically expressed by activated fibroblasts, and quinoline-based specific inhibitors (FAPI) were developed, allowing us to visualize its distribution in vivo by imaging techniques. In this review, we discuss the use of FAPα as a useful biomarker for the progression of lung fibrosis, by both its assessment in human fluids and/or its detection by imaging techniques and immunohistochemistry.

Background Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive and irreversible respiratory failure. Non-invasive markers of disease activity are essential for prognosis and evaluation of early response to anti-fibrotic treatments. Objectives The aims of this study were to determine whether fluorodeoxyglucose ([18F]-FDG) lung uptake is reduced after initiation of pirfenidone or nintedanib and to assess its possible use as a prognostic factor. Methods [18F]-FDG PET/CT was performed in IPF patients and in a murine model of pulmonary fibrosis. PET/CTs were performed at day 8 and day 15 post-instillation of bleomycin in pirfenidone- or vehicule-treated mice. In IPF patients, PET-CT was performed before and 3 months after the initiation of pirfenidone or nintedanib. Results In bleomycin-treated mice, pirfenidone significantly reduced the [18F]-FDG uptake compared to vehicule-treated mice at day 15 ( p  < 0.001), whereas no difference was observed at day 8 after bleomycin administration. In IPF patients, [18F]-FDG lung uptake before and after 3 months of treatment by nintedanib ( n  = 11) or pirfenidone ( n  = 14) showed no significant difference regardless the antifibrotic treatment. Moreover, no difference was noticed between patients with progressive or non-progressive disease at one year of follow up. Conclusions Pirfenidone significantly reduces the lung [18F]-FDG uptake during the fibrotic phase in a mouse model of IPF. However, these preclinical data were not confirmed in IPF patients 3 months after the initiation of antifibrotic therapy. [18F]-FDG seems therefore not useful in clinical practice to assess the early response of IPF patients to nintedanib or pirfenidone.

Background Fibroblast activation protein-α (FAPα) is a marker of activated fibroblasts that can be selectively targeted by an inhibitor (FAPI) and visualised by PET/CT imaging. We evaluated whether the measurement of FAPα in bronchoalveolar lavage fluids (BALF) and the uptake of FAPI by PET/CT could be used as biomarkers of fibrogenesis. Methods The dynamics of lung uptake of 18 F-labeled FAPI ([ 18 F]FAPI-74) was assessed in the bleomycin mouse model at various time points and using different concentrations of bleomycin by PET/CT. FAPα was measured in BALFs from these bleomycin-treated and control mice. FAPα levels were also assessed in BALFs from controls and patients with idiopathic pulmonary fibrosis (IPF). Results Bleomycin-treated mice presented a significantly higher uptake of [ 18 F]FAPI-74 during lung fibrinogenesis (days 10 and 16 after instillation) compared to control mice. No significant difference was observed at initial inflammatory phase (3 days) and when fibrosis was already established (28 days). [ 18 F]FAPI-74 tracer was unable to show a dose-response to bleomycin treatment. On the other hand, BALF FAPα levels were steeply higher in bleomycin-treated mice at day 10 and a significant dose-response effect was observed. Moreover, FAPα levels were strongly correlated with lung fibrosis as measured by the modified Aschroft histological analysis, hydroxyproline and the percentage of weight loss. Importantly, higher levels of FAPα were observed in IPF patients where the disease was progressing as compared to stable patients and controls. Moreover, patients with FAPα BALF levels higher than 192.5 pg/mL presented a higher risk of progression, transplantation or death compared to patients with lower levels. Conclusions Our preclinical data highlight a specific increase of [ 18 F]FAPI-74 lung uptake during the fibrotic phase of the bleomycin murine model. The measurement of FAPα in BALF appears to be a promising marker of the fibrotic activity in preclinical models of lung fibrosis and in IPF patients. Further studies are required to confirm the role of FAPα in BALF as biomarker of IPF activity and assess the relationship between FAPα levels in BALF and [ 18 F]FAPI-74 uptake on PET/CT in patients with fibrotic lung disease.

Background Although increasing data supports the use of transbronchial lung cryobiopsies (TBLCs) for the diagnosis of diffuse parenchymal lung diseases (DPLDs), its role as an alternative to surgical lung biopsy (SLB) is still under debate. The aim of this study was to assess the benefit of additional SLBs performed in selected patients after TBLCs. Method We conducted a multicentric Belgian prospective trial in which SLBs were performed after TBLCs when the pathological diagnosis was uncertain or if a nonspecific interstitial pneumonia (NSIP) pattern was observed hypothesizing that SLB could provide additional information and that a co-existent UIP pattern could be missed. Results Eighty-one patients with TBLCs performed for a DPLD were included in the study between April 2015 and December 2019. A specific histological diagnosis was obtained in 52 patients (64%) whereas no pathological diagnosis following TBLCs was obtained in 13 patients (16%) and a pattern suggestive of a NSIP was observed in 16 patients (20%). Fourteen out of these 29 patients had SLBs after TBLCs. SLBs showed a UIP pattern in 11 (79%), a pattern suggestive of a hypersensitivity pneumonitis in two (14%) and a NSIP pattern in one patient (7%). Among the 16 patients with pathological NSIP following TBLCs, six underwent a SLBs showing a UIP in five and confirming a NSIP in one patient only. A retrospective pathological analysis of patients having both procedures showed a lower diagnostic confidence and agreement among pathologists for TBLCs compared to SLBs. Major factors underlying the added value of SLBs were the bigger size of the sample as well as the subpleural localization of the biopsies. Conclusions TBLCs are useful in the setting of DPLDs with a good diagnostic yield. However, our study suggests that SLB provides critical additional information in case TBLCs are inconclusive or show a pattern suggestive of a NSIP, questioning the accuracy of TBLC to adequately identify this histological pattern.

Hypereosinophilia is uncommon in ASS and this presentation makes diagnosis more challenging. Anti‐PL12's role in the severity of ILD is controversial but its association with anti‐Ro52 seems to give a more serious disease phenotype. African ethnicity could be a negative prognostic factor, associated with lung disease severity.

Background The PROOF registry is an observational study initiated in October 2013 with the aim to monitor disease progression in a real-world population of patients with idiopathic pulmonary fibrosis (IPF). Here, we present longitudinal clinical outcomes from the PROOF registry. Methods Patients with IPF were enrolled across eight centers in Belgium and Luxembourg. For all patients, clinical outcomes data were collected, including mortality, lung transplant, acute exacerbations, and pulmonary hypertension. For patients treated with pirfenidone at any time during follow-up (2013–2017), for any duration of treatment (the pirfenidone-treated population): pirfenidone treatment patterns were collected; changes in pulmonary function (forced vital capacity [FVC] and carbon monoxide diffusing capacity [DLco]) were reviewed up to 24 months post-inclusion; and time-to-event analyses from the time of registry inclusion were performed. Results The PROOF registry enrolled a total of 277 patients. During follow-up, 23.1% of patients died, 5.1% received a lung transplant, 5.4% experienced an acute exacerbation, and 6.1% had comorbid pulmonary hypertension. In the pirfenidone-treated population ( N  = 233, 84.1%), 12.9% of patients had a temporary dose discontinuation and 31.8% had a temporary dose reduction; 4.3% of patients permanently discontinued pirfenidone due to an adverse drug reaction. Mean percent predicted FVC was 81.2% (standard deviation [SD] 19.0) at Month 0 and 78.3% (SD 25.0) at Month 24, and mean percent predicted DLco was 47.0% (SD 13.2) and 45.0% (SD 16.5), respectively. Rates of ≥ 10% absolute decline in percent predicted FVC and ≥ 15% absolute decline in percent predicted DLco over 24 months were 31.0% and 23.2%, respectively. Mean times from registry inclusion to categorical absolute decline in percent predicted FVC and percent predicted DLco were 20.1 (standard error [SE] 0.6) months and 23.4 (SE 0.5) months, respectively; mean time from registry inclusion to death was 31.0 (SE 0.9) months. Conclusions The PROOF registry is a source of European data characterizing longitudinal clinical outcomes of patients with IPF. Over 12 months of follow-up, pulmonary function remained largely stable in patients with IPF who received pirfenidone for any duration of treatment. Pulmonary function remained similar at 24 months of follow-up, although patient numbers were lower. Trial registration PROOF is registered with the relevant authorities in Belgium and Luxembourg, with registration to Comité National d’Éthique et de Recherche (CNER) N201309/03–12 September 2013 and a notification to Comité National de Protection des Données (CNDP) for Luxembourg.

Background The surgical lung biopsy (SLB) is the recommended sampling technique when the pathological analysis of the lung is required in the work-up of an interstitial lung disease (ILD) but trans-bronchial lung cryobiopsy (TBLC) is increasingly recognized as an alternative approach. As TBLCs have lower mortality and morbidity risks than SLB, this study aimed to investigate the safety of TBLCs in patients at higher risk of complications and for whom SLB was not considered as an alternative. Method This prospective study was conducted in two hospitals in which TBLCs were performed in patients with body mass index (BMI) > 35, and/or older than 75 years, and/or with severely impaired lung function (FVC < 50% or DLCO < 30%), and/or systolic pulmonary artery pressure > 45 mmHg, and/or a clinically significant cardiac disease. Patients with any of these risk factors constituted the high-risk group. Clinical outcomes were compared with those obtained in patients without these risk factors (low-risk group). Results Ninety-six patients were included between April 2015 and April 2020, respectively 38 and 58 in the high-risk or the low-risk group. No statistically significant difference was observed between both groups in terms of severity and rate of bleeding, pneumothorax, or duration of hospital stay ( p value ranging from 0.419 to 0.914). Conclusion This preliminary study on a limited number of patients suggests that TBLC appears safe in those in whom lung biopsy is at high-risk of complications according to their age, BMI, lung impairment, and cardiac comorbidities.

The new pandemic virus SARS-CoV-2 is characterized by uncontrolled hyper-inflammation in severe cases. As the IL-22/IL-22R1 axis was reported to be involved in inflammation during viral infections, we characterized the expression of IL-22 receptor1, IL-22 and IL-22 binding protein in COVID-19 patients. Blood samples were collected from 19 non-severe and 14 severe patients on the day they presented (D0), at D14, and six months later, and from 6 non-infected controls. The IL-22R1 expression was characterized by flow cytometry. Results were related to HLA-DR expression of myeloid cells, to plasma concentrations of different cytokines and chemokines and NK cells and T lymphocytes functions characterized by their IFN-γ, IL-22, IL-17A, granzyme B and perforin content. The numbers of IL-22R1 + classical, intermediate, and non-classical monocytes and the proportions of IL-22R1 + plasmacytoid DC (pDC), myeloid DC1 and DC2 (mDC1, mDC2) were higher in patients than controls at D0. The proportions of IL-22R1 + classical and intermediate monocytes, and pDC and mDC2 remained high for six months. High proportions of IL-22R1 + non-classical monocytes and mDC2 displayed HLA-DR high expression and were thus activated. Multivariate analysis for all IL-22R1 + myeloid cells discriminated the severity of the disease (AUC=0.9023). However, correlation analysis between IL-22R1 + cell subsets and plasma chemokine concentrations suggested pro-inflammatory effects of some subsets and protective effects of others. The numbers of IL-22R1 + classical monocytes and pDC were positively correlated with pro-inflammatory chemokines MCP-1 and IP-10 in severe infections, whereas IL-22R1 + intermediate monocytes were negatively correlated with IL-6, IFN-α and CRP in non-severe infections. Moreover, in the absence of in vitro stimulation, NK and CD4 + T cells produced IFN-γ and IL-22, and CD4 + and CD8 + T cells produced IL-17A. CD4 + T lymphocytes also expressed IL-22R1, the density of its expression defining two different functional subsets. In conclusion, we provide the first evidence that SARS-CoV-2 infection is characterized by an abnormal expression of IL22R1 on blood myeloid cells and CD4 + T lymphocytes. Our results suggest that the involvement of the IL-22R1/IL-22 axis could be protective at the beginning of SARS-CoV-2 infection but could shift to a detrimental response over time.