Frédéric Pène

Dendritic Cells Modulate Lung Response to Pseudomonas aeruginosa in a Murine Model of Sepsis-Induced Immune Dysfunction

Host infection by pathogens triggers an innate immune response leading to a systemic inflammatory response, often followed by an immune dysfunction which can favor the emergence of secondary infections. Dendritic cells (DCs) link innate and adaptive immunity and may be centrally involved in the regulation of sepsis-induced immune dysfunction. We assessed the contribution of DCs to lung defense in a murine model of sublethal polymicrobial sepsis (cecal ligature and puncture, CLP). In this model, bone marrow-derived DCs (BMDCs) retained an immature phenotype, associated with decreased capacity of IL-12p70 release and impaired priming of T cell lymphocytes. Eight days after CLP surgery, we induced a secondary pulmonary infection through intratracheal instillation of 5 × 106 CFUs of Pseudomonas aeruginosa. Whereas all sham-operated mice survived, 80% of post-CLP mice died after secondary pneumonia. Post-CLP mice exhibited marked lung damage with early recruitment of neutrophils, cytokine imbalance with decreased IL-12p70 production, and increased IL-10 release, but no defective bacterial lung clearance, while systemic bacterial dissemination was almost constant. Concomitant intrapulmonary administration of exogenous BMDCs into post-CLP mice challenged with P. aeruginosa dramatically improved survival. BMDCs did not improve bacterial lung clearance, but delayed neutrophil recruitment, strongly attenuated the early peak of TNF-α and restored an adequate Il-12p70/IL-10 balance in post-CLP mice. Thus, adoptive transfer of BMDCs reversed sepsis-induced immune dysfunction in a relevant model of secondary P. aeruginosa pneumonia. Unexpectedly, the mechanism of action of BMDCs did not involve enhanced antibacterial activity, but occurred by dampening the pulmonary inflammatory response.

Epidemiology and outcome of severe pneumococcal pneumonia admitted to intensive care unit: a multicenter study

IntroductionCommunity-acquired pneumonia (CAP) account for a high proportion of ICU admissions, with Streptococcus pneumoniae being the main pathogen responsible for these infections. However, little is known on the clinical features and outcomes of ICU patients with pneumococcal pneumonia. The aims of this study were to provide epidemiological data and to determine risk factors of mortality in patients admitted to ICU for severe S. pneumoniae CAP.MethodsWe performed a retrospective review of two prospectively-acquired multicentre ICU databases (2001-2008). Patients admitted for management of severe pneumococcal CAP were enrolled if they met the 2001 American Thoracic Society criteria for severe pneumonia, had life-threatening organ failure and had a positive microbiological sample for S. pneumoniae. Patients with bronchitis, aspiration pneumonia or with non-pulmonary pneumococcal infections were excluded.ResultsTwo hundred and twenty two patients were included, with a median SAPS II score reaching 47 [36-64]. Acute respiratory failure (n = 154) and septic shock (n = 54) were their most frequent causes of ICU admission. Septic shock occurred in 170 patients (77%) and mechanical ventilation was required in 186 patients (84%); renal replacement therapy was initiated in 70 patients (32%). Bacteraemia was diagnosed in 101 patients. The prevalence of S. pneumoniae strains with decreased susceptibility to penicillin was 39.7%. Although antibiotherapy was adequate in 92.3% of cases, hospital mortality reached 28.8%. In multivariate analysis, independent risk factors for mortality were age (OR 1.05 (95% CI: 1.02-1.08)), male sex (OR 2.83 (95% CI: 1.16-6.91)) and renal replacement therapy (OR 3.78 (95% CI: 1.71-8.36)). Co-morbidities, macrolide administration, concomitant bacteremia or penicillin susceptibility did not influence outcome.ConclusionsIn ICU, mortality of pneumococcal CAP remains high despite adequate antimicrobial treatment. Baseline demographic data and renal replacement therapy have a major impact on adverse outcome.

Markers of intestinal injury are associated with endotoxemia in successfully resuscitated patients

AIMS Gut dysfunction is suspected to play a major role in the pathophysiology of post-resuscitation disease through an increase in intestinal permeability and endotoxin release. However this dysfunction often remains occult and is poorly investigated. The aim of this pilot study was to explore intestinal failure biomarkers in post-cardiac arrest patients and to correlate them with endotoxemia. METHODS Following resuscitation after cardiac arrest, 21 patients were prospectively studied. Urinary intestinal fatty acid-binding protein (IFABP), which marks intestinal permeability, plasma citrulline, which reflects the functional enterocyte mass, and whole blood endotoxin were measured at admission, days 1-3 and 6. We explored the kinetics of release and the relationship between IFABP, citrulline and endotoxin values. RESULTS IFABP was extremely high at admission and normalized at D3 (6668 pg/mL vs 39 pg/mL, p=0.01). Lowest median of citrulline (N=20-40 μmol/L) was attained at D2 (11 μmol/L at D2 vs 24 μmol/L at admission, p=0.01) and tended to normalize at D6 (21 μmol/L). During ICU stay, 86% of patients presented a detectable endotoxemia. Highest endotoxin level was positively correlated with highest IFABP level (R(2)=0.31, p=0.01) and was inversely correlated with lowest plasma citrulline levels (R(2)=0.55, p<0.001). Endotoxin levels increased between admission and D2 in patients with post-resuscitation shock, whereas it decreases in patients with no shock (median +0.33 EU vs -0.19 EU, p=0.03). Highest endotoxin level was positively correlated with D3 SOFA score (R(2)=0.45, p=0.004). CONCLUSION Biomarkers of intestinal injury are altered after cardiac arrest and are associated with endotoxemia. This could worsen post-resuscitation shock and organ failure.

Increased survival of cirrhotic patients with septic shock

IntroductionThe overall outcome of septic shock has been recently improved. We sought to determine whether this survival gain extends to the high-risk subgroup of patients with cirrhosis.MethodsCirrhotic patients with septic shock admitted to a medical intensive care unit (ICU) during two consecutive periods (1997-2004 and 2005-2010) were retrospectively studied.ResultsForty-seven and 42 cirrhotic patients presented with septic shock in 1997-2004 and 2005-2010, respectively. The recent period differed from the previous one by implementation of adjuvant treatments of septic shock including albumin infusion as fluid volume therapy, low-dose glucocorticoids, and intensive insulin therapy. ICU and hospital survival markedly improved over time (40% in 2005-2010 vs. 17% in 1997-2004, P = 0.02 and 29% in 2005-2010 vs. 6% in 1997-2004, P = 0.009, respectively). Furthermore, this survival gain in the latter period was sustained for 6 months (survival rate 24% in 2005-2010 vs. 6% in 1997-2004, P = 0.06). After adjustment with age, the liver disease stage (Child-Pugh score), and the critical illness severity score (SOFA score), ICU admission between 2005 and 2010 remained an independent favorable prognostic factor (odds ratio (OR) 0.09, 95% confidence interval (CI) 0.02-0.4, P = 0.004). The stage of the underlying liver disease was also independently associated with hospital mortality (Child-Pugh score: OR 1.42 per point, 95% CI 1.06-1.9, P = 0.018).ConclusionsIn the light of advances in management of both cirrhosis and septic shock, survival of such patients substantially increased over recent years. The stage of the underlying liver disease and the related therapeutic options should be included in the decision-making process for ICU admission.

Src-family-tyrosine kinase Lyn is critical for TLR2-mediated NF-κB activation through the PI 3-kinase signaling pathway.

TLR2 has a prominent role in host defense against a wide variety of pathogens. Stimulation of TLR2 triggers MyD88-dependent signaling to induce NF-κB translocation, and activates a Rac1-PI 3-kinase dependent pathway that leads to transactivation of NF-κB through phosphorylation of the P65 NF-κB subunit. This transactivation pathway involves tyrosine phosphorylations. The role of the tyrosine kinases in TLR signaling is controversial, with discrepancies between studies using only chemical inhibitors and knockout mice. Here, we show the involvement of the tyrosine-kinase Lyn in TLR2-dependent activation of NF-κB in human cellular models, by using complementary inhibition strategies. Stimulation of TLR2 induces the formation of an activation cluster involving TLR2, CD14, PI 3-kinase and Lyn, and leads to the activation of AKT. Lyn-dependent phosphorylation of the p110 catalytic subunit of PI 3-kinase is essential to the control of PI 3-kinase biological activity upstream of AKT and thereby to the transactivation of NF-κB. Thus, Lyn kinase activity is crucial in TLR2-mediated activation of the innate immune response in human mononuclear cells.

Protective Effects of FCGR2A Polymorphism in Invasive Pneumococcal Diseases

BACKGROUND Streptococcus pneumoniae is a major cause of pneumonia and meningitis. Several genetic polymorphisms have been described to explain differences in susceptibility and severity of encapsulated pathogen-related diseases. Among them, a functional FCGR2A polymorphism leading to amino acid change of histidine (H) to arginine (R) at position 131 appears to be a major candidate in adult invasive pneumococcal diseases (IPDs). However, previous reports need confirmation in a large, well-defined population. METHODS This prospective genetic association study was carried out in a 24-bed medical ICU of a tertiary teaching hospital over 7 years. DNA from all white patients with IPD (pneumonia or meningitis) was genotyped for the FcγRIIa-R/H131 polymorphism. RESULTS A total of 243 patients with IPD were enrolled; 202 (82%) had pneumonia, and 55 (22%) had meningitis. Mean age was 61 years, and mean Simplified Acute Physiology Score II was 50.4. One-half of the patients had bacteremia, and 84% of the cohort received mechanical ventilation. The hospital mortality rate was 31%. In the IPD group, the distribution of the FcγRIIa-R/H131 genotypes (H/H, 25%; H/R, 53%; R/R, 22%) was comparable with that in the white control group. Comparison of the FcγRIIa-R/R131 and the FcγRIIa-R/H131 + FcγRIIa-H/H131 groups did not demonstrate any difference for age, Simplified Acute Physiology Score II, origin of sepsis, and other comorbid conditions. However, the variant FcγRIIa-R/R131 genotype was independently associated with decreased hospital mortality (OR, 0.251; 95% CI, 0.098-0.645; P = .004). CONCLUSIONS In a well-defined population of patients with IPD, the frequency of the variant FcγRIIa-R131 does not differ from that of other critically ill patients. However, the FcγRIIa-R/R131 genotype was independently associated with increased survival, regardless of site of infection.

Sepsis‐induced expansion of granulocytic myeloid‐derived suppressor cells promotes tumour growth through Toll‐like receptor 4

Severe sepsis remains a frequent and dreaded complication in cancer patients. Beyond the often fatal short‐term outcome, the long‐term sequelae of severe sepsis may also impact directly on the prognosis of the underlying malignancy in survivors. The immune system is involved in all stages of tumour development, in the detection of transforming and dying cells and in the prevention of tumour growth and dissemination. In fact, the profound and sustained immune defects induced by sepsis may constitute a privileged environment likely to favour tumour growth. We investigated the impact of sepsis on malignant tumour growth in a double‐hit animal model of polymicrobial peritonitis, followed by subcutaneous inoculation of MCA205 fibrosarcoma cells. As compared to their sham‐operated counterparts, post‐septic mice exhibited accelerated tumour growth. This was associated with intratumoural accumulation of CD11b+Ly6Ghigh polymorphonuclear cells (PMNs) that could be characterized as granulocytic myeloid‐derived suppressor cells (G‐MDSCs). Depletion of granulocytic cells in post‐septic mice inhibited the sepsis‐enhanced tumour growth. Toll‐like receptor (TLR)‐4 (Tlr4) and Myd88 deficiencies prevented sepsis‐induced expansion of G‐MDSCs and tumour growth. Our results demonstrate that the myelosuppressive environment induced by severe bacterial infections promotes malignant tumour growth, and highlight a critical role of CD11b+Ly6Ghigh G‐MDSCs under the control of TLR‐dependent signalling. Copyright