Alain Lepape

Marked alterations of neutrophil functions during sepsis-induced immunosuppression.

Severe septic syndromes deeply impair innate and adaptive immunity and are responsible for sepsis‐induced immunosuppression. Although neutrophils represent the first line of defense against infection, little is known about their phenotype and functions a few days after sepsis, when the immunosuppressive phase is maximal (i.e., between d 3 and 8). The objective of the present study was to perform, for the first time, a global evaluation of neutrophil alterations in immunosuppressed septic patients (at d 3–4 and d 6–8) using phenotypic and functional studies. In addition, the potential association of these parameters and deleterious outcomes was assessed. Peripheral blood was collected from 43 septic shock patients and compared with that of 23 healthy controls. In the septic patients, our results highlight a markedly altered neutrophil chemotaxis (functional and chemokine receptor expressions), oxidative burst, and lactoferrin content and an increased number of circulating immature granulocytes (i.e., CD10dimCD16dim). These aspects were associated with an increased risk of death after septic shock. In contrast, phagocytosis and activation capacities were conserved. To conclude, circulating neutrophils present with phenotypic, functional, and morphologic alterations a few days after sepsis onset. These dysfunctions might participate in the deleterious role of sepsis‐induced immunosuppression. The present results open new perspectives in the mechanisms favoring nosocomial infections after septic shock. They deserve to be further investigated in a larger clinical study and in animal models recapitulating these alterations.

Decreased HLA-DR antigen-associated invariant chain (CD74) mRNA expression predicts mortality after septic shock

IntroductionSeptic syndromes remain the leading cause of mortality in intensive care units (ICU). Septic patients rapidly develop immune dysfunctions, the intensity and duration of which have been linked with deleterious outcomes. Decreased mRNA expressions of major histocompatibility complex (MHC) class II-related genes have been reported after sepsis. We investigated whether their mRNA levels in whole blood could predict mortality in septic shock patients.MethodsA total of 93 septic shock patients were included. On the third day after shock, the mRNA expressions of five MHC class II-related genes (CD74, HLA-DRA, HLA-DMB, HLA-DMA, CIITA) were measured by qRT-PCR and monocyte human leukocyte antigen-DR (mHLA-DR) by flow cytometry.ResultsA significant correlation was found among MHC class II related gene expressions. Among mRNA markers, the best prognostic value was obtained for CD74 (HLA-DR antigen-associated invariant chain). For this parameter, the area under the receiver operating characteristic curve (AUC) was calculated (AUCu2009=u20090.67, 95% confidence interval (CI)u2009=u20090.55 to 0.79; Pu2009=u20090.01) as well as the optimal cut-off value. After stratification based on this threshold, survival curves showed that a decreased CD74 mRNA level was associated with increased mortality after septic shock (Log rank test, Pu2009=u20090.0043, Hazard Ratiou2009=u20093.0, 95% CI: 1.4 to 6.5). Importantly, this association remained significant after multivariate logistic regression analysis including usual clinical confounders (that is, severity scores, Pu2009=u20090.026, Odds Ratiou2009=u20093.4, 95% CI: 1.2 to 9.8).ConclusionDecreased CD74 mRNA expression significantly predicts 28-day mortality after septic shock. After validation in a larger multicentric study, this biomarker could become a robust predictor of death in septic patients.

S100A8/A9 mRNA Induction in an Ex Vivo Model of Endotoxin Tolerance: Roles of IL-10 and IFNγ

Objectives Septic syndromes are the leading cause of death in intensive care units. They are characterized by the development of immune dysfunctions such as endotoxin tolerance (ET), whose intensity and duration are associated with increased risk of nosocomial infections and mortality. Alarmins S100A8 and S100A9 have been shown to be increased after septic shock. Importantly, a delayed S100A9 mRNA increase predicts hospital-acquired infection in patients. The aim of this study was to investigate the regulation of S100A8 and S100A9 mRNA expression in an ex vivo model of ET. Subjects and Measurements ET was reproduced ex vivo by priming healthy peripheral blood mononuclear cells (number of donors u200a=u200a9 to 10) with low-dose endotoxin (2 ng/ml) before stimulation with high dose endotoxin (100 ng/ml). S100A8 and S100A9 mRNA levels were measured by quantitative real-time polymerase chain reactions. Main Results ET was established by observing decreased TNFα and increased IL-10 transcriptomic responses to two subsequent endotoxin challenges. Interestingly, ET was associated with increased S100A8 and S100A9 mRNA expression ex vivo. We showed that IL-10 played a role in this process, since S100A8 and S100A9 mRNA increases were significantly abrogated by IL-10 blockade in the model. Conversely, treatment with rIFN-γ, a pro-inflammatory and immunostimulating molecule known to block ET induction, was able to restore normal S100A8 and S100A9 mRNA in this model. Conclusions In this ex vivo model, we observed that S100A8 and S100A9 mRNA expression was significantly increased during ET. This reproduced ex vivo the observations we had previously made in septic shock patients. Interestingly, IL-10 blockade and rIFN-γ treatment partially abrogated S100A8/A9 mRNA increases in this model. Pending confirmation in larger, independent clinical studies, these preliminary results suggest that S100A8 and S100A9 mRNA levels might be used as surrogate markers of ET and as stratification tools for personalized immunotherapy in septic shock patients.

Delayed increased S100A9 mRNA predicts hospital-acquired infection after septic shock

Septic shock (SS) remains a serious disease with high mortality and increased risk of hospital-acquired infection (HAI). Access to biomarkers assessing prognosis of these outcomes is of utmost importance in order to select patients for future therapeutic strategies. Alarmins are normal cell constituents that can be released into the extracellular milieu during states of cellular stress and subsequently activate the innate immune system. Several alarmins of the S100 family are released by phagocytes in response to cell stress, recognized by RAGE and/or TLR4 on monocytes and therefore highlight as relevant mediators in sepsis pathophysiology. Among them, S100A8 and S100A9 exist mainly as a heterodimer called calprotectin. However, several studies suggest independent functioning of S100A9, making it an interesting candidate biomarker in septic syndromes.