Aikaterini Spyridaki

Early alterations of the innate and adaptive immune statuses in sepsis according to the type of underlying infection

IntroductionAlthough major changes of the immune system have been described in sepsis, it has never been studied whether these may differ in relation to the type of underlying infection or not. This was studied for the first time.MethodsThe statuses of the innate and adaptive immune systems were prospectively compared in 505 patients. Whole blood was sampled within less than 24 hours of advent of sepsis; white blood cells were stained with monoclonal antibodies and analyzed though a flow cytometer.ResultsExpression of HLA-DR was significantly decreased among patients with severe sepsis/shock due to acute pyelonephritis and intraabdominal infections compared with sepsis. The rate of apoptosis of natural killer (NK) cells differed significantly among patients with severe sepsis/shock due to ventilator-associated pneumonia (VAP) and hospital-acquired pneumonia (HAP) compared with sepsis. The rate of apoptosis of NKT cells differed significantly among patients with severe sepsis/shock due to acute pyelonephritis, primary bacteremia and VAP/HAP compared with sepsis. Regarding adaptive immunity, absolute counts of CD4-lymphocytes were significantly decreased among patients with severe sepsis/shock due to community-acquired pneumonia (CAP) and intraabdominal infections compared with sepsis. Absolute counts of B-lymphocytes were significantly decreased among patients with severe sepsis/shock due to CAP compared with sepsis.ConclusionsMajor differences of the early statuses of the innate and adaptive immune systems exist between sepsis and severe sepsis/shock in relation to the underlying type of infection. These results may have a major impact on therapeutics.

Effect of Clarithromycin in Inflammatory Markers of Patients with Ventilator-Associated Pneumonia and Sepsis Caused by Gram-Negative Bacteria: Results from a Randomized Clinical Study

ABSTRACT One recent, double-blind, randomized clinical trial with 200 patients showed that clarithromycin administered intravenously for 3 days in patients with ventilator-associated pneumonia (VAP) accelerated the resolution of pneumonia and decreased the risk of death from septic shock and multiple organ dysfunctions (MODS). The present study focused on the effect of clarithromycin on markers of inflammation in these patients. Blood was drawn immediately before the administration of the allocated treatment and on six consecutive days after the start of treatment. The concentrations of circulating markers were measured. Monocytes and neutrophils were isolated for immunophenotyping analysis and for cytokine stimulation. The ratio of serum interleukin-10 (IL-10) to serum tumor necrosis factor alpha (TNF-α) was decreased in the clarithromycin group compared with the results in the placebo group. Apoptosis of monocytes was significantly increased on day 4 in the clarithromycin group compared with the rate of apoptosis in the placebo group. On the same day, the expression of CD86 was increased and the ratio of soluble CD40 ligand (sCD40L) to CD86 in serum was unchanged. The release of TNF-α, IL-6, and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) by circulating monocytes after stimulation was greater in the clarithromycin group than in the placebo group. The expression of TREM-1 on monocytes was also increased in the former group. These effects were pronounced in patients with septic shock and MODS. These results suggest that the administration of clarithromycin restored the balance between proinflammatory versus anti-inflammatory mediators in patients with sepsis; this was accompanied by more efficient antigen presentation and increased apoptosis. These effects render new perspectives for the immunotherapy of sepsis.

Role of tumor necrosis factor gene single nucleotide polymorphisms in the natural course of 2009 influenza A H1N1 virus infection

OBJECTIVES To identify the role of single nucleotide polymorphisms (SNPs) of the tumor necrosis factor (TNF) gene in the natural course of 2009 influenza A H1N1 virus infection. METHODS Genomic DNA was isolated from 109 patients with an H1N1 infection and from 108 healthy volunteers. SNPs of the TNF gene were assessed after electrophoresis of the digested PCR products by restriction enzymes. RESULTS The frequency of the -238 A allele was significantly greater among patients than among controls. Viral pneumonia developed in 20 of 96 non-carriers of at least one -238 A allele (20.8%) and in seven of 13 carriers of at least one -238 A allele (53.8%, p=0.016). Logistic regression analysis showed that the most important factors associated with the development of pneumonia were the presence of an underlying disease (p=0.021, odds ratio (OR) 3.08) and the carriage of at least one -238 A allele (p=0.041, OR 3.74). Gene transcripts of the TNF gene were greater among non-carriers of the -238 A allele than among carriers of the -238 A allele. CONCLUSIONS The -238 A SNP allele of the TNF gene imposes on the course of 2009 H1N1 virus infection and is an independent risk factor for pneumonia.

An early circulating factor in severe sepsis modulates apoptosis of monocytes and lymphocytes

We hypothesized that a factor may circulate in serum early during sepsis, modulating apoptosis of monocytes and lymphocytes. Serum was collected from 20 healthy volunteers and from 48 patients with severe sepsis/shock within 12 h from signs of the first failing organ. PBMCs were isolated from 20 healthy volunteers and incubated with collected sera. Apoptosis and expression of CD95 were determined by flow cytometry; experiments were run in the presence of caspase‐8 and caspase‐9 inhibitors and of CaCl2. Activity of caspase‐3 was determined in cell lysates by a chromogenic kinetic assay. Incubation with serum of patients induced apoptosis of CD4 lymphocytes and inhibited apoptosis of CD14 monocytes. This was attenuated after diluting serum or mixing with healthy serum. Activity of caspase‐3 was consistent with these findings. Induced apoptosis of CD4 lymphocytes was greater among nonsurvivors, and it was inhibited in the presence of caspase inhibitors. Inhibitors did not modify the effect of patientsˈ serum on apoptosis of CD14 monocytes. CaCl2 reversed the inhibitory effect on apoptosis of CD14 moncytes. The above findings support the hypothesis for the existence of an early circulating factor in severe sepsis/shock, modulating apoptosis of CD4 lymphocytes and of CD14 monocytes by interaction with the two apoptotic pathways.

Effect of clarithromycin in patients with suspected Gram-negative sepsis: results of a randomized controlled trial

BACKGROUND A previous randomized study showed that clarithromycin decreases the risk of death due to ventilator-associated pneumonia and shortens the time until infection resolution. The efficacy of clarithromycin was tested in a larger population with sepsis. METHODS Six hundred patients with systemic inflammatory response syndrome due to acute pyelonephritis, acute intra-abdominal infections or primary Gram-negative bacteraemia were enrolled in a double-blind, randomized, multicentre trial. Clarithromycin (1 g) was administered intravenously once daily for 4 days consecutively in 302 patients; another 298 patients were treated with placebo. Mortality was the primary outcome; resolution of infection and hospitalization costs were the secondary outcomes. RESULTS The groups were well matched for demographics, disease severity, microbiology and appropriateness of the administered antimicrobials. Overall 28 day mortality was 17.1% (51 deaths) in the placebo arm and 18.5% (56 deaths) in the clarithromycin arm (P = 0.671). Nineteen out of 26 placebo-treated patients with septic shock and multiple organ dysfunctions died (73.1%) compared with 15 out of 28 clarithromycin-treated patients (53.6%, P = 0.020). The median time until resolution of infection was 5 days in both arms. In the subgroup with severe sepsis/shock, this was 10 days in the placebo arm and 6 days in the clarithromycin arm (P = 0.037). The cost of hospitalization was lower after treatment with clarithromycin (P = 0.044). Serious adverse events were observed in 1.3% and 0.7% of placebo- and clarithromycin-treated patients, respectively (P = 0.502). CONCLUSIONS Intravenous clarithromycin did not affect overall mortality; however, administration shortened the time to resolution of infection and decreased the hospitalization costs.

TREM-1 expression on neutrophils and monocytes of septic patients: relation to the underlying infection and the implicated pathogen

BackgroundCurrent knowledge on the exact ligand causing expression of TREM-1 on neutrophils and monocytes is limited. The present study aimed at the role of underlying infection and of the causative pathogen in the expression of TREM-1 in sepsis.MethodsPeripheral venous blood was sampled from 125 patients with sepsis and 88 with severe sepsis/septic shock. The causative pathogen was isolated in 91 patients. Patients were suffering from acute pyelonephritis, community-acquired pneumonia (CAP), intra-abdominal infections (IAIs), primary bacteremia and ventilator-associated pneumonia or hospital-acquired pneumonia (VAP/HAP). Blood monocytes and neutrophils were isolated. Flow cytometry was used to estimate the TREM-1 expression from septic patients.ResultsWithin patients bearing intrabdominal infections, expression of TREM-1 was significantly lower on neutrophils and on monocytes at severe sepsis/shock than at sepsis. That was also the case for severe sepsis/shock developed in the field of VAP/HAP. Among patients who suffered infections by Gram-negative community-acquired pathogens or among patients who suffered polymicrobial infections, expression of TREM-1 on monocytes was significantly lower at the stage of severe sepsis/shock than at the stage of sepsis.ConclusionsDecrease of the expression of TREM-1 on the membrane of monocytes and neutrophils upon transition from sepsis to severe sepsis/septic shock depends on the underlying type of infection and the causative pathogen.

Impact of Multidrug Resistance on Experimental Empyema by Pseudomonas aeruginosa

Background:Pseudomonas aeruginosa is a cause of infections of the lower respiratory tract among patients with chronic lung disorders. It is questionable whether virulence of this species may be influenced by multidrug resistance (MDR). Objectives: To define the impact of MDR in experimental lung infection. Methods: Experimental empyema was induced in rabbits by MDR (group A, n = 16) and by susceptible isolates (group B, n = 10). Pleural fluid was sampled for quantitative culture and estimation of cell apoptosis and of tumor necrosis factor-alpha (TNFα) and malondialdehyde (MDA). Survival was recorded. Cytokine production was stimulated in U937 monocytes by samples of pleural fluid. Whole blood of rabbits was incubated with the isolates; induction of apoptosis was assessed. Results: Survival of group A was prolonged compared to group B. This was accompanied by lower bacterial counts of the inoculated pathogens in pleural fluid and in the lungs of group A compared with group B. Early apoptosis of neutrophils of pleural fluid of group A was lower compared with group B. Pleural fluid concentrations of TNFα and MDA did not differ between the groups. Cytokine production by U937 monocytes after stimulation with pleural fluid was greater in group B than in group A. The susceptible isolate induced apoptosis of neutrophils in vitro at a greater rate than the MDR isolate. Conclusions: Experimental empyema by susceptible P. aeruginosa is accompanied by greater mortality compared with MDR P. aeruginosa. This phenomenon may be attributed to the different growth pattern of the pathogens or to their interaction with the innate immune system.

Indication for a role of regulatory T cells for the advent of influenza A (H1N1)-related pneumonia.

Regulatory T cells (Tregs) have an anti‐inflammatory role. A former study in a limited number of patients found that absolute counts of Tregs increase when infection by the new influenza H1N1 virus is complicated with pneumonia. These results generate the question if H1N1‐related pneumonia is associated with a state of hypo‐inflammation. A total of 135 patients were enrolled with blood sampling within less than 24 h from diagnosis; 23 with flu‐like syndrome; 69 with uncomplicated H1N1‐infection; seven with bacterial pneumonia; and 36 with H1N1‐related pneumonia. Tregs and CD14/HLA‐DR co‐expression were estimated by flow cytometry; concentrations of tumour necrosis factor‐alpha (TNF‐α), of interleukin (IL)‐6 and of soluble triggering receptor expressed on myeloid cells‐1 (sTREM‐1) by an enzyme immunoassay; those of procalcitonin (PCT) by immuno‐time‐resolved amplified cryptate technology assay. Expression of human leucocyte antigen D‐related (HLA‐DR) on monocytes was similar between groups; absolute Treg counts were greater among patients with H1N1‐related pneumonia than flu‐like syndrome or H1N1‐uncomplicated infection. Serum TNF‐α of patients with bacterial pneumonia was greater than those of other groups, but IL‐10 was similar between groups. Serum PCT was greater among patients with H1N1‐related pneumonia and sTREM‐1 among those with H1N1‐related pneumonia. Regression analysis revealed that the most important factors related with the advent of pneumonia were the existence of underlying illnesses (P = 0·006) and of Tregs equal to or above 16 mm3 (P = 0·013). It is concluded that the advent of H1N1‐related pneumonia is related to an early increase of the absolute Treg counts. This increase is probably not part of a hypo‐inflammatory state of the host.

Effect of clarithromycin in experimental empyema by multidrug‐resistant Pseudomonas aeruginosa

Evidence from a recent randomized study of our group suggests that intravenous clarithromycin resulted in earlier resolution of ventilator‐associated pneumonia. The need to understand the mechanism of action of clarithromycin guided to the study of a model of experimental empyema by multidrug‐resistant Pseudomonas aeruginosa in 40 rabbits. Animals were randomized into controls (group A); treatment with clarithromycin (group B); treatment with piperacillin/tazobactam (group C); and treatment with both agents (group D). Pleural fluid was collected at regular time intervals for quantitative culture, estimation of cell apoptosis and of concentrations of tumour necrosis factor‐alpha (TNFα). After 7 days, animals were euthanized for estimation of tissue growth. Bacterial growth in the pleural fluid of group D was significantly decreased compared with the other groups on day 5. Lung growth of group D was lower than group A. That was also the case of cytokine stimulation by pleural fluid samples on U937 monocytes. It is concluded that administration of clarithromycin enhanced the antimicrobial efficacy of piperacillin/tazobactam and decreased bacterial growth in the pleural fluid and in tissues. It also attenuated the pro‐inflammatory phenomena induced by the β‐lactam.

Dexamethasone Down-Regulates Expression of Triggering Receptor Expressed on Myeloid Cells-1: Evidence for a TNFα-Related Effect.

Objectives: To investigate the effect of dexamethasone on triggering receptor expressed on myeloid cells-1 (TREM-1). Methods: Wild-type and tumor necrosis factor (TNF−/−) mice were pre-treated with saline, dexamethasone, or hydrocortisone and exposed to a lethal infection of Pseudomonas aeruginosa. Mortality and TREM-1 on neutrophil membranes was measured after sacrifice. U937 human monocytic cells were stimulated with lipopolysaccharide (LPS) or heat-killed P. aeruginosa without or with dexamethasone or hydrocortisone, and cell-surface TREM-1 and soluble TREM-1 (sTREM-1) were quantified. Expression of TREM-1 and sTREM-1 was also studied in LPS-stimulated U937 cells incubated in the absence or presence of TNFα or anti-TNFα antibody. Results: Pre-treatment with dexamethasone, but not hydrocortisone, prolonged animal survival. Mice pre-treated with dexamethasone showed decreased expression of TREM-1 on neutrophils. In U937 cells, LPS or heat-killed P. aeruginosa induced the expression of TREM-1 and the release of sTREM-1. U937 TREM-1 and sTREM-1 were decreased upon addition of dexamethasone but not hydrocortisone. The suppressive effect of dexamethasone was enhanced in the presence of exogenous TNFα and lost in the presence of anti-TNFα antibody. In TNF−/− mice, dexamethasone suppression of mortality and TREM-1 neutrophil expression was lost. Gene expression of TREM-1 in U937 monocytes was decreased after treatment with dexamethasone. Conclusion: TREM-1/sTREM-1 is a novel site of action of dexamethasone. This action is associated with down-regulation of gene expression and is mediated by TNFα.