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Pneumocystis pneumonia (PcP) remains life-threatening in kidney transplant recipients (KTR). Our study investigated risk factors one-year before PcP. We conducted a monocentric, case-control study including all KTR at the Dijon University Hospital (France) with a diagnosis of PcP between 2005 and 2022 (cases), and matched control KTR with no history of PcP (3 controls/case). Among all 1,135 KTR, 57 cases (5%) and 169 matched-controls were included. PcP was associated with 18% mortality. Compared to controls, cases were older, with a higher immunological risk, and CMV infection was more frequent in the year preceding the occurrence of PcP (23% vs. 4%; p < 0.001). As early as 1 year before PcP, lymphocyte counts were lower and serum creatinine levels were higher in cases, but immunosuppressive regimens were not significantly different. Multivariable analysis identified lymphocyte count, serum creatinine level, being treated by immunosuppressive therapy other than anti-rejection drugs, and CMV infection in the year preceding the time PcP as independently associated with the occurrence of PcP. PcP was associated with an increased risk of subsequent chronic rejection (27% vs. 3%; p = 0.001) and return to dialysis (20% vs. 3%; p = 0.002). The occurrence of CMV infection and a low lymphocyte count could redefine the indications for continuation or reinitiation of anti- Pneumocystis prophylaxis.

Background COVID-19-related ARDS has unique features when compared with ARDS from other origins, suggesting a distinctive inflammatory pathogenesis. Data regarding the host response within the lung are sparse. The objective is to compare alveolar and systemic inflammation response patterns, mitochondrial alarmin release, and outcomes according to ARDS etiology (i.e., COVID-19 vs. non-COVID-19). Methods Bronchoalveolar lavage fluid and plasma were obtained from 7 control, 7 non-COVID-19 ARDS, and 14 COVID-19 ARDS patients. Clinical data, plasma, and epithelial lining fluid (ELF) concentrations of 45 inflammatory mediators and cell-free mitochondrial DNA were measured and compared. Results COVID-19 ARDS patients required mechanical ventilation (MV) for significantly longer, even after adjustment for potential confounders. There was a trend toward higher concentrations of plasma CCL5, CXCL2, CXCL10, CD40 ligand, IL-10, and GM-CSF, and ELF concentrations of CXCL1, CXCL10, granzyme B, TRAIL, and EGF in the COVID-19 ARDS group compared with the non-COVID-19 ARDS group. Plasma and ELF CXCL10 concentrations were independently associated with the number of ventilator-free days, without correlation between ELF CXCL-10 and viral load. Mitochondrial DNA plasma and ELF concentrations were elevated in all ARDS patients, with no differences between the two groups. ELF concentrations of mitochondrial DNA were correlated with alveolar cell counts, as well as IL-8 and IL-1β concentrations. Conclusion CXCL10 could be one key mediator involved in the dysregulated immune response. It should be evaluated as a candidate biomarker that may predict the duration of MV in COVID-19 ARDS patients. Targeting the CXCL10-CXCR3 axis could also be considered as a new therapeutic approach. Trial registration ClinicalTrials.gov, NCT03955887

Background Actinotignum schaalii is an emerging urogenital pathogen rarely reported as a cause of endocarditis. Case presentation A 54-year-old man developed recurrent embolic strokes seven and eight years post-Bentall procedure with mechanical aortic valve. Blood cultures grew Gram-positive bacilli, initially misidentified as Corynebacterium spp. , later confirmed as Actinotignum schaalii . Cardiac CT revealed a 12 mm × 15 mm × 20 mm perivalvular abscess fistulizing into the sinus of Valsalva and prosthetic graft. 18 F-FDG PET/CT confirmed intense hypermetabolism around the prosthesis. Despite targeted amoxicillin therapy, intraoperative exploration revealed complete Bentall conduit dehiscence from extensive aorto-mitral trigone destruction. Reconstruction was deemed unfeasible, and the patient died following multidisciplinary decision to limit interventions. No urological source was identified. Conclusions Actinotignum schaalii can cause indolent prosthetic valve endocarditis with devastating perivalvular complications. Prolonged blood culture incubation is crucial for early diagnosis in patients with prosthetic material and unexplained embolic events. Clinical trial Not applicable.

Lipopolysaccharide (LPS) is a major virulence factor during both meningococcal and Haemophilus influenzae meningitis. Pneumococcus does not produce LPS but could be responsible for bacterial digestive translocation as a consequence of sepsis. We addressed this question in the context of pneumococcal meningitis. A cross-sectional study on 24 patients with pneumococcal meningitis (20 (83%) admitted in intensive care unit, 4 (17%) with septic shock) and 34 prospectively-enrolled healthy volunteers. Interleukin 6 and C-reactive proteins plasma concentrations were measured as markers of systemic inflammation. Endotoxemia was measured using mass spectrometry (LC-MS/MS) for detection of molecules bound to the lipid A, namely 3-OH fatty acids. Meningitis patients had significantly higher levels of plasma C-reactive protein (237 (74-373) vs. 2 (2-2) mg/l, p < 0.001 and interleukin 6 (43 (13-128) vs. 4.6 (4.6-16.6) pg/ml; p < 0.001) than healthy volunteers. However, we observed no significant difference in plasma lipopolysaccharide concentrations between patients and healthy volunteers (674 (554-896) vs. 668 (623-777) pmol/ml; p = 0.546). Our results suggest that LPS is not a key determinant of the excessive inflammation associated with severe forms of pneumococcal meningitis.

Background Although immune modulation is a promising therapeutic avenue in coronavirus disease 2019 (COVID-19), the most relevant targets remain to be found. COVID-19 has peculiar characteristics and outcomes, suggesting a unique immunopathogenesis. Methods Thirty-six immunocompetent non-COVID-19 and 27 COVID-19 patients with severe pneumonia were prospectively enrolled in a single center, most requiring intensive care. Clinical and biological characteristics (including T cell phenotype and function and plasma concentrations of 30 cytokines) and outcomes were compared. Results At similar baseline respiratory severity, COVID-19 patients required mechanical ventilation for significantly longer than non-COVID-19 patients (15 [7–22] vs. 4 (0–15) days; p = 0.0049). COVID-19 patients had lower levels of most classical inflammatory cytokines (G-CSF, CCL20, IL-1β, IL-2, IL-6, IL-8, IL-15, TNF-α, TGF-β), but higher plasma concentrations of CXCL10, GM-CSF and CCL5, compared to non-COVID-19 patients. COVID-19 patients displayed similar T-cell exhaustion to non-COVID-19 patients, but with a more unbalanced inflammatory/anti-inflammatory cytokine response (IL-6/IL-10 and TNF-α/IL-10 ratios). Principal component analysis identified two main patterns, with a clear distinction between non-COVID-19 and COVID-19 patients. Multivariate regression analysis confirmed that GM-CSF, CXCL10 and IL-10 levels were independently associated with the duration of mechanical ventilation. Conclusion We identified a unique cytokine response, with higher plasma GM-CSF and CXCL10 in COVID-19 patients that were independently associated with the longer duration of mechanical ventilation. These cytokines could represent the dysregulated immune response in severe COVID-19, as well as promising therapeutic targets. ClinicalTrials.gov: NCT03505281.

Background Although mesenchymal stromal cells (MSCs) have shown promising effects in preclinical pneumonia models, their ability to improve outcomes in ventilator-associated pneumonia (VAP) remains poorly explored, despite VAP being a frequent and severe complication in critically ill patients. This study investigated whether MSCs could enhance outcomes in a rabbit VAP model. Methods Male rabbits were ventilated and received lipopolysaccharide (LPS, 3 ng/kg) to mimic sepsis-induced immune dysfunction. After 24 h, animals were inoculated intratracheally with Enterobacter aerogenes to induce VAP. In experiment 1, rabbits ( n  = 10/group) were randomized to receive human umbilical cord-derived MSCs (3 × 10^6/kg, intravenous) or saline, 4 h after bacterial challenge. In experiment 2, all rabbits received cefepime, with or without MSCs. Outcomes included lung bacterial load (primary), systemic dissemination, 24 h survival, lung injury, and markers of immune and mitochondrial dysfunction. Results MSC infusion alone did not improve survival (8/10 vs. 9/10; p  = .46), lung bacterial load (median [IQR] 6.67 [5.64–7.60] vs. 6.08 [5.72–6.82] log10 CFU/ml; p  = .37), systemic dissemination, or lung inflammation. Similarly, lung pathology scores, alveolar neutrophils, and systemic cytokines were unaffected. In contrast, when combined with cefepime, MSCs showed a non-significant trend toward improved survival (10/10 vs. 7/10; p  = .067), significantly reduced lung bacterial burden (5.23 [5.05–5.56] vs. 5.47 [5.18–7.01] log10 CFU/ml; p  = .049), improved macroscopic lung scores ( p  = .008), and lowered IL-6 levels ( p  = .037). However, MSCs did not correct systemic immune dysfunction. Conclusion MSCs alone did not improve lung bacterial clearance or inflammation resolution in this rabbit VAP model. However, the combination of MSCs with cefepime enhanced lung bacterial clearance and reduced lung IL-6 concentrations, compared with cefepime alone. Further studies are required to elucidate the mechanisms underlying the combined effects of antibiotics and MSCs.

Community-acquired pneumonia (CAP) is a leading cause of death, with mortality linked to an unbalanced host response. Sirtuin (Sirt)1, a histone deacetylase, regulating metabolism and epigenetics, may be fundamental in activating the innate immune response. Sirt1 mRNA expression was significantly reduced in monocytes from CAP patients (n = 76) upon admission compared to healthy controls (n = 42), with levels returning to normal after 30 days. Pharmacological activation of Sirt1 with SRT1720 decreased LPS- and K. pneumoniae-induced IL-6 release in primary human monocytes and decreased NF-κB activation in THP1 cells. In a mouse K. pneumoniae pneumosepsis model, SRT1720 strongly reduced neutrophil influx and degranulation markers in bronchoalveolar lavage fluid, lowered pulmonary concentrations of IL-6 and TNF-α, and reduced lung pathology scores. Simultaneously, it reduced neutrophil content in liver tissue and plasma transaminase levels, alongside a trend toward reduced liver necrosis. Plasma IL-6 and TNF-α were significantly lower in SRT1720-treated mice at 42 h. Finally, while SRT1720 did not impact bacterial loads in the lungs, it reduced bacterial burden in blood, with a similar trend observed in liver homogenates. In conclusion, the Sirt1 activator SRT1720 exerts anti-inflammatory effects on human monocytes, reduces local and systemic inflammation and organ injury, and diminishes bacterial dissemination in murine pneumosepsis.

Background While not traditionally included in the conceptual understanding of circulation, the interstitium plays a critical role in maintaining fluid homeostasis. Fluid balance regulation is a critical aspect of septic shock, with a well-known association between fluid balance and outcome. The regulation of transcapillary flow is the first key to understand fluid homeostasis during sepsis. Main text Capillary permeability is increased during sepsis, and was classically considered to be necessary and sufficient to explain the increase of capillary filtration during inflammation. However, on the other side of the endothelial wall, the interstitium may play an even greater role to drive capillary leak. Indeed, the interstitial extracellular matrix forms a complex gel-like structure embedded in a collagen skeleton, and has the ability to directly attract intravascular fluid by decreasing its hydrostatic pressure. Thus, interstitium is not a mere passive reservoir, as was long thought, but is probably major determinant of fluid balance regulation during sepsis. Up to this date though, the role of the interstitium during sepsis and septic shock has been largely overlooked. A comprehensive vision of the interstitium may enlight our understanding of septic shock pathophysiology. Overall, we have identified five potential intersections between septic shock pathophysiology and the interstitium: 1. increase of oedema formation, interacting with organ function and metabolites diffusion; 2. interstitial pressure regulation, increasing transcapillary flow; 3. alteration of the extracellular matrix; 4. interstitial secretion of inflammatory mediators; 5. decrease of lymphatic outflow. Conclusions We aimed at reviewing the literature and summarizing the current knowledge along these specific axes, as well as methodological aspects related to interstitium exploration.

Endogenous tissue mediators inducing lung inflammation in the context of ventilator-induced lung injury (VILI) and acute respiratory distress syndrome (ARDS) are ill-defined. To test whether mitochondrial alarmins are released during VILI, and are associated with lung inflammation. Release of mitochondrial DNA, adenosine triphosphate (ATP), and formyl-Met-Leu-Phe (fMLP) peptide-dependent neutrophil chemotaxis were measured in conditioned supernatants from human alveolar type II-like (A549) epithelial cells submitted to cyclic stretch in vitro. Similar measurements were performed in bronchoalveolar lavage fluids from rabbits submitted to an injurious ventilatory regimen, and from patients with ARDS. Mitochondrial DNA was released by A549 cells during cell stretching, and was found elevated in BAL fluids from rabbits during VILI, and from ARDS patients. Cyclic stretch-induced interleukin-8 (IL-8) of A549 cells could be inhibited by Toll-like receptor 9 (TLR9) blockade. ATP concentrations were increased in conditioned supernatants from A549 cells, and in rabbit BAL fluids during VILI. Neutrophil chemotaxis induced by A549 cells conditioned supernatants was essentially dependent on fMLP rather than IL-8. A synergy between cyclic stretch-induced alarmins and lipopolysaccharide (LPS) was found in monocyte-derived macrophages in the production of IL-1ß. Mitochondrial alarmins are released during cyclic stretch of human epithelial cells, as well as in BAL fluids from rabbits ventilated with an injurious ventilatory regimen, and found in BAL fluids from ARDS patients, particularly in those with high alveolar inflammation. These alarmins are likely to represent the proximal endogenous mediators of VILI and ARDS, released by injured pulmonary cells.

IntroductionObesity is commonly reported in COVID-19 patients and is associated with poorer outcomes. It is suggested that leptin could be the missing link between obesity and severe COVID-19. Our study aimed to unravel the link between adipokines, COVID-19 status, immune response, and outcomes in severe pneumonia.MethodsIn this prospective observational single-center study, 63 immunocompetent patients with severe pneumonia (36 non-COVID-19 and 27 COVID-19) were enrolled, most required intensive care. Clinical and biological characteristics (glucose metabolism, plasma adipokines, and cytokine concentrations) and outcomes were compared.ResultsAt similar baseline severity, COVID-19 patients required mechanical ventilation for significantly longer than non-COVID-19 patients (p = 0.0049). Plasma concentrations of leptin and adiponectin were respectively positively and negatively correlated with BMI and glucose metabolism (glycemia and insulinemia), but not significantly different between the two groups. Leptin levels were negatively correlated with IL-1β and IL-6, but the adipokines were not correlated with most other inflammatory mediators, baseline severity (SOFA score), or the duration of mechanical ventilation.ConclusionAdipokine levels were correlated with BMI but not with most inflammatory mediators, severity, or outcomes in severe pneumonia, regardless of the origin. The link between obesity, dysregulated immune response, and life-threatening COVID-19 requires further investigation.Clinical trialClinicalTrials.gov: NCT03505281.