Mj O'Dwyer

The perioperative immune response.

Purpose of reviewA host of immune modulators are now available in clinical practice. The perioperative period is characterized by profound alterations in host immunity, which can result in poor outcomes, which include infection, cancer recurrence and organ failure. Manipulation of the perioperative immune response has the potential to improve outcomes. A complete understanding of the mechanisms and clinical consequences of altered immune function in this setting is therefore imperative. Recent findingsRecent in-vivo data have emerged which further our understanding of the interaction between tissue damage, immune modulation and clinical outcomes by utilizing novel laboratory techniques capable of monitoring single-cell immune signatures. Traditional gene expression assays have continued to demonstrate their utility and have been instrumental in defining the host response to perioperative allogeneic blood transfusion. These mechanistic studies are complemented by large clinical studies describing associations between anaesthetic modalities and immune-related outcomes. SummaryLaboratory techniques are now available that can monitor the perioperative immune response and could be further developed to introduce personalized care pathways. Consideration must also be given to anaesthesia techniques and perioperative treatments that, although not immediately harmful, may be associated with poor outcomes temporally distant from the treatment, secondary to induced immunosuppression.

Systemic inflammatory response syndrome after major abdominal surgery predicted by early upregulation of TLR4 and TLR5

Objectives:To study innate immune pathways in patients undergoing hepatopancreaticobiliary surgery to understand mechanisms leading to enhanced inflammatory responses and identifying biomarkers of adverse clinical consequences. Background:Patients undergoing major abdominal surgery are at risk of life-threatening systemic inflammatory response syndrome (SIRS) and sepsis. Early identification of at-risk patients would allow tailored postoperative care and improve survival. Methods:Two separate cohorts of patients undergoing major hepatopancreaticobiliary surgery were studied (combined nu200a=u200a69). Bloods were taken preoperatively, on day 1 and day 2 postoperatively. Peripheral blood mononuclear cells and serum were separated and immune phenotype and function assessed ex vivo. Results:Early innate immune dysfunction was evident in 12 patients who subsequently developed SIRS (postoperative day 6) compared with 27 who did not, when no clinical evidence of SIRS was apparent (preoperatively or days 1 and 2). Serum interleukin (IL)-6 concentration and monocyte Toll-like receptor (TLR)/NF-&kgr;B/IL-6 functional pathways were significantly upregulated and overactive in patients who developed SIRS (Pu200a<u200a0.0001). Interferon &agr;-mediated STAT1 phosphorylation was higher preoperatively in patients who developed SIRS. Increased TLR4 and TLR5 gene expression in whole blood was demonstrated in a separate validation cohort of 30 patients undergoing similar surgery. Expression of TLR4/5 on monocytes, particularly intermediate CD14++CD16+ monocytes, on day 1 or 2 predicted SIRS with accuracy 0.89 to 1.0 (areas under receiver operator curves). Conclusions:These data demonstrate the mechanism for IL-6 overproduction in patients who develop postoperative SIRS and identify markers that predict patients at risk of SIRS 5 days before the onset of clinical signs.

Changes in gene expression following trauma are related to the age of transfused packed red blood cells.

BACKGROUND Transfusion of packed red blood cells (PRBCs) is associated with an increased incidence of nosocomial infections and an increased risk of death. The duration of storage before transfusion may influence these outcomes. Here, we explore the association between the age of transfused PRBCs and specific patterns of inflammatory gene expression in severely injured trauma patients. METHODS Severely injured trauma patients requiring intensive care unit treatment and receiving transfusion of PRBCs within 24 hours of the injury were recruited. Blood samples were obtained within 2 hours of the trauma, at 24 hours, and at 72 hours. Messenger RNA was extracted from whole blood, and gene expression was quantified using quantitative polymerase chain reaction. The median age of the units of PRBCs transfused to each patient was recorded. The primary outcome measure was the change in candidate gene expression over the initial 72 hours. RESULTS Sixty-four patients were studied. Fifty-three patients (83%) were male, and the median age was 40.5 years (interquartile range [IQR], 31–59). Median Injury Severity Score (ISS) was 31.5 (IQR, 23–43), and 55 patients (86%) experienced a blunt injury. Forty-one patients (64%) developed a nosocomial infection, and 15 patients (23%) died before hospital discharge. Each patient received a median of 5 U of PRBCs (IQR, 4–9.8 U) during the first 24 hours of hospital admission. The median age of the units of PRBCs transfused in each patient was 20 days (IQR, 17–22 days). Older blood was associated with greater decreases in interleukin 12 (IL-12), IL-23, and ROR&ggr;t (all p’s < 0.05) gene expression over the initial 24 hours, greater decreases in IL-12 gene expression over 72 hours, and a rise in transforming growth factor &bgr; gene expression over the first 72 hours. A multivariate analysis confirmed the independence of these associations. CONCLUSION Increasing the duration of storage of PRBCs before transfusion is associated with a pattern of gene expression consistent with more severe immunosuppression. LEVEL OF EVIDENCE Epidemiologic study, level III.

Does major surgery induce immune suppression and increase the risk of postoperative infection

Purpose of review Infection is the commonest cause of a postoperative complication. Following major surgery alterations in immune function are commonplace and these may contribute to an enhanced susceptibility to acquire nosocomial infections. This review will discuss postoperative infections in the context of an altered perioperative immune response and the factors influencing this response. Recent findings Up to 10% of patients undergoing elective in-patient surgery may develop a postoperative infection. Laboratory advances now permit systematic monitoring of single-cell immune signatures, which enable a clearer description of the interaction between tissue damage, immune modulation and clinical outcomes. Traditional candidate gene expression has identified pathways that define the detrimental immune modulating effects of perioperative allogeneic blood transfusion. Large clinical studies have demonstrated that the choice of anaesthetic technique may have an impact on postoperative infections through differential immune modulation. Summary Point of care tests are emerging that allow monitoring of the perioperative immune response. These could be further developed to introduce personalised care pathways. Consideration must also be given to anaesthesia techniques and perioperative treatments that may be associated with poor outcomes through immune modulation.

Features of Postoperative Immune Suppression Are Reversible With Interferon Gamma and Independent of Interleukin-6 Pathways.

Objective: The aim of this study was to evaluate the role of interleukin (IL)-6 pathways in postoperative immune suppression and to assess the reversibility of this phenomenon. Background: The postoperative period is characterized by increased IL-6 production and features of immune suppression. In vitro, IL-6 mediates anti-inflammatory effects through inhibition of interferon gamma (IFN-&ggr;) pathways. The significance of the immunomodulatory effects of IL-6 in the clinical setting of postoperative immune suppression remains unclear. Methods: Patients over 45 years old undergoing elective surgery, involving the gastrointestinal tract, were recruited. IL-6 levels were assayed using an enzyme linked immunosorbent assay preoperatively, and at 24 and 48 hours. Peripheral blood mononuclear cells from healthy volunteers were cultured in perioperative serum and CD14+Human Leukocyte Antigen-DR (HLA-DR) [monocyte HLA-DR (mHLA-DR)] geometric mean florescent intensity was measured in the presence and absence of IL-6 neutralizing antibody and recombinant IFN-&ggr;. Results: Of the 108 patients, 41 developed a postoperative infection. The IL-6 levels increased 19-fold from the preoperative sample to 24 hours postoperatively (Pu200a<u200a0.0001). Higher IL-6 levels at 24 (Pu200a=u200a0.0002) and 48 hours (Pu200a=u200a0.003) were associated with subsequent postoperative infectious complications. mHLA-DR mean florescent intensity fell when healthy peripheral blood mononuclear cells were cultured with postoperative serum compared with preoperative serum (Pu200a=u200a0.008). This decrease was prevented by the presence of IFN-&ggr; in the culture media, but not by the presence of IL-6-neutralizing antibody. Conclusions: IL-6 levels increase after a major surgery and are associated with an increased susceptibility to postoperative infections. Serum obtained from postoperative patients induces an immunosuppressive response, reflected in reduced mHLA-DR levels, mediated through IL-6 independent pathways and is reversible with IFN-&ggr;. These data may have therapeutic implications for the prevention of infection in patients undergoing major surgery.

Epigenetic regulatory pathways involving microRNAs may modulate the host immune response following major trauma

BACKGROUND Posttraumatic nosocomial pneumonia is a common complication resulting in significant morbidity. Trauma-induced immunocompromise is associated with an enhanced susceptibility to pneumonia. In this study, we explore the hypothesis that posttranscriptional epigenetic regulation of gene expression may be an important factor in determining this immune phenotype. We describe the pattern of production of microRNAss (miRs) and their association with nosocomial pneumonia following severe trauma. METHODS A convenience sample of 30 ventilated polytrauma patients (UKCRN ID: 5637) and 16 healthy controls were recruited. Messenger RNA and protein levels of key cytokines were quantified within 2 hours of the injury and at 24 hours. Three miRs per cytokine were then selected based on miRBase target prediction scores and quantified using polymerase chain reaction. Nosocomial pneumonia was defined using the Centers for Disease Control and Prevention definitions. RESULTS Median Injury Severity Score (ISS) was 29, and 47% of the patients developed nosocomial pneumonia. miR-125a and miR-202 decreased by 34% and 77%, respectively, immediately following injury, whereas their target, IL-10, increased messenger RNA levels 3-fold and protein levels 180-fold. Tumor necrosis factor &agr; (TNF-&agr;) and IL-12 gene expression decreased by 68% and 43%, respectively, following injury, and this was mirrored by a 10-fold increase in miR-181, an miR predicted to target TNF-&agr; transcripts. Lower levels of miR-125a and miR-374b were associated with the later acquisition of hospital-acquired pneumonia. CONCLUSION Alteration in the expression of miRs with highly predicted complementarity to IL-10 and TNF-&agr; may be an important mechanism regulating the posttraumatic immunosuppressive phenotype in intensive care unit patients. LEVEL OF EVIDENCE Retrospective observational study, level III.

1068. MicroRNA-regulated immunosuppression in severely injured polytrauma patients

We have demonstrated that traumatic injury is associated with an early immunosuppressive response, the extent of which is associated with an increased risk of developing nosocomial infections. In particular, the expression of the immunosuppressive cytokine IL-10 was up-regulated 2 hours following injury [1]. However, the mechanisms involved are unclear. MicroRNAs (miRs) are short non-coding RNA molecules whose main function is to down-regulate gene expression. Although preliminary laboratory data suggest alterations in miR expression may play a role in triggering this immunosuppressive phenotype there is currently a lack of data in trauma patients [2, 3].

MicroRNA-mediated regulation of IL-10, IL-12 and TNFα gene expression in severely injured trauma patients

Background Severe trauma induces a blunted immune response associated with an enhanced susceptibility to nosocomial infections [1]. Within 2 hours of injury, expression of the prototypical anti-inflammatory cytokine, IL-10, increases whilst expression of the pro-inflammatory cytokines, TNFa and IL-12, decreases [1]. We hypothesise that microRNAs (miRs) may exacerbate this immunosuppressive gene expression pattern.

Long-Term Follow-Up of Sepsis Induced Immunoparalysis

Severe sepsis induces a state of immunoparalysis.[1] Animal models have demonstrated this to be secondary to microbial-induced host epigenetic alterations, which persist and are associated with long-term immunoparalysis.[2] Whilst human sepsis is associated with poor long-term outcomes in conjunction with recurrent infections,[3] it is not clear if the immunoparalysed state persists following recovery from the initial septic insult.

The Role of Micrornas in The Development of Hospital Acquired Infection in Polytrauma Patients

Introduction n nTraumatic injury is associated with immunosuppression and an increased risk of developing nosocomial infections. However, the immune regulatory mechanisms involved remain unclear. n nObjectives n n1) To describe genome-wide alterations in micro RNA (miRNA) expression following severe trauma. n n2) To explore the potential role of miRNAs in mediating the post-traumatic immunosuppressive phenotype and their potential role in enhancing the risk of nosocomial infections. n nMethods n nPatients requiring ICU care following traumatic injury were recruited. Whole blood was collected within 2 hours of injury and 24 hours later. Total RNA (containing miRNAs) was isolated utilising PAX Gene and RNA extraction kits (Qiagen). miRNA-sequencing was performed with the Illumina HiSeq2500, and sequences were aligned to the human GRCh37 reference genome. Data analysis was carried out using the DESEQ2 package in R, and miRNAs were considered significantly altered with an adjusted p value of < 0.05. Functional enrichment analysis was performed using Ingenuity Pathway Analysis (IPA) on all miRNAs reaching an adjusted p value of < 0.1. mRNA targets of interest were identified using miRBase and TargetScan (http://www.mirbase.org, http://www.targetscan.org). n nResults n n49 patients were recruited and 25 patients developed nosocomial infections. Expression of 139 miRNAs was significantly altered between 2 hours and 24 hours following injury, with miR-146b, a key inhibitor of pro-inflammatory pathways[1], upregulated to the greatest degree. Figure 1 presents miRNAs that differ between those patients who developed nosocomial infections and those who did not. miR-144-5p was significantly different between the two groups at both time points. a large percentage of mRNA targets for miR-144 are involved the Cell-mediated Immune Response (Figure 2), including the B-cell receptor complex, p38MAPK, GATA3, IgG, BCL6 and the T-cell receptor. in addition, we have previously shown that the miR-374 family of miRNAs is linked to increased IL-10 expression in trauma patients[2]. IPA highlights Cancer, Haematological Disease, Immunological and Inflammatory Disease and Organismal Injury and Abnormalities as important pathways altered between infected and non-infected patients. n nConclusions n nThese data provide a miRNA signature of severely injured trauma patients who develop hospital acquired infection compared to those who do not, and identify the miR-144 and miR-374b families as being of particular interest for future studies of trauma-induced immune dysfunction.