Jens Altrichter

The clinical value of neutrophil extracellular traps

Neutrophil extracellular traps (NETs) have recently been discovered as a central part of antimicrobial innate immunity. In the meanwhile, evidence accumulated that NETs are also generated upon non-infectious stimuli in various clinical settings. In acute or chronic inflammatory disorders aberrantly enhanced NET formation and/or decreased NET degradation seems to correlate with disease outcome. This review summarizes current knowledge about the relation of NETs in a broad spectrum of clinical settings. Specifically, we focus on the importance of NETs as a predictive marker in severely ill patients and further, we speculate about the potential pathophysiology of NETs.

Diagnostic accuracy of neutrophil‐derived circulating free DNA (cf‐DNA/NETs) for septic arthritis

The release of “neutrophil extracellular traps” (NETs) has been identified as a novel immune response in innate immunity. NETs are composed of neutrophil‐derived circulating free DNA (cf‐DNA) and neutrophil cytoplasm‐derived proteins such as proteases. In this study, we analyzed the putative diagnostic value of synovial cf‐DNA/NETs for identification of septic arthritis. Forty‐two patients with a joint effusion who had undergone arthrocentesis were included. From synovial fluid, cf‐DNA/NETs (j‐cf‐DNA) levels were directly quantified. Diagnostic value of j‐cf‐DNA was compared with white blood cells (WBC), synovial white blood cells (j‐WBC), C‐reactive protein (CRP), j‐IL‐6, j‐TNF alpha, j‐IL‐1 beta, and myeloperoxidase (j‐MPO). Sensitivity, specificity, positive and negative predictive value, as well as ROC‐curves for each parameter were calculated. Synovial fluid cf‐DNA/NETs values from patients with septic arthritis (3,286 ± 386 ng/ml, n = 9) were significantly increased compared to patients with noninfectious joint inflammation (1,040 ± 208 ng/ml, n = 17) or osteoarthritis (278 ± 34 ng/ml, n = 16, p < 0.01). In conjunction with j‐cf‐DNA, j‐IL‐6 and j‐IL‐1 beta were significantly elevated (p < 0.01), but WBC, CRP, and j‐WBC were not. At a cut‐off of 300 ng/ml, j‐cf‐DNA had a sensitivity of 0.89, a specificity of 1.0, a positive predictive value of 1.0, and a negative predictive value of 0.97. Receiver operation curves revealed largest areas under the curve for cf‐DNA/NETs (0.933) and j‐IL‐6 (0.951). cf‐DNA/NETs seem to be a valuable additional marker for the diagnosis of septic arthritis or periprosthetic infections. However, this result should be confirmed in a large clinical trial.

Increased plasma kynurenine values and kynurenine-tryptophan ratios after major trauma are early indicators for the development of sepsis.

Kynurenine, the major degradation product of tryptophan has been shown to directly damage tissues, but its possible contribution to posttraumatic morbidity is unknown. Here, we studied the kinetics of kynurenine in patients after major trauma and whether this correlates with the development of posttraumatic sepsis. Kynurenine and tryptophan levels of 60 multiple-injured patients with Injury Severity Score of more than 16 were quantified prospectively by high-performance liquid chromatography. Blood samples were obtained daily from admission until day 10 after admission. Significantly increased kynurenine values were detectable already at day 1 after admission in blood from patients who later developed sepsis, regardless of injury pattern (P < 0.01). In contrast, kynurenine values of nonsepsis patients remained low throughout the observation period. However, all patients exhibited significantly decreased tryptophan values versus healthy controls (P < 0.01). Moreover, significantly increased kynurenine-tryptophan ratios rapidly predicted subsequent sepsis, multiple organ failure, and death (P < 0.01). Both increased kynurenine values and kynurenine-tryptophan ratios predicted posttraumatic development of sepsis and organ failure. This ought to be validated in subsequent studies.

Mcl-1-Mediated Impairment of the Intrinsic Apoptosis Pathway in Circulating Neutrophils from Critically Ill Patients Can Be Overcome by Fas Stimulation

The systemic inflammatory response syndrome and subsequent organ failure are mainly driven by activated neutrophils with prolonged life span, which is believed to be due to apoptosis resistance. However, detailed underlying mechanisms leading to neutrophil apoptosis resistance are largely unknown, and possible therapeutic options to overcome this resistance do not exist. Here we report that activated neutrophils from severely injured patients exhibit cell death resistance due to impaired activation of the intrinsic apoptosis pathway, as evidenced by limited staurosporine-induced mitochondrial membrane depolarization and decreased caspase-9 activity. Moreover, we found that these neutrophils express high levels of antiapoptotic Mcl-1 and low levels of proapoptotic Bax protein. Mcl-1 up-regulation was dependent on elevated concentrations of GM-CSF in patient serum. Accordingly, increased Mcl-1 protein stability and GM-CSF serum concentrations were shown to correlate with staurosporine-induced apoptosis resistance. However, cross-linking of neutrophil Fas by immobilized agonistic anti-Fas IgM resulted in caspase-dependent mitochondrial membrane depolarization and apoptosis induction. In conclusion, the observed impairment of the intrinsic pathway and the resulting apoptosis resistance may be overcome by immobilized agonistic anti-Fas IgM. Targeting of neutrophil Fas by immobilized agonistic effector molecules may represent a new therapeutic tool to limit neutrophil hyperactivation and its sequelae in patients with severe immune disorders.

Extracorporeal cell therapy with granulocytes in a pig model of Gram-positive sepsis.

Objectives:Granulocyte transfusions have been used to treat immune cell dysfunction in sepsis. As granulocyte transfusions can trigger tissue injury via local effects of neutrophils, we hypothesized that extracorporeal treatment of plasma using granulocytes would prove beneficial while having less side effects. Design:Prospective controlled three-armed animal study. Setting:Research laboratory. Subjects:Twenty-one female immature pigs (7.5–12 kg, 7–9 weeks old). Interventions:Three groups of spontaneously breathing, sedated pigs (n = 7 each) received an intravenous lethal dose of live Staphylococcus aureus over 1 hour. Although group I had no specific treatment (control), group II and III were subsequently treated for 4 hours with an extracorporeal device containing either no cells (sham control, group II) or human cell line-derived granulocytic cells (group III). Survival time and physiologic, biochemical, and hematologic parameters were monitored for 7 days. Measurements and Main Results:All animals of group I died during the observation time (mean survival time: 70 hours). In group II, two of seven and in group III, six of seven animals survived the observation time (mean survival: 75 and 168 hours, respectively). Survival differences were significant between group I and III (p < 0.001) and between group II and III (p < 0.05) but not between group I and II (p = 0.43). Furthermore, group differences in bacterial blood concentrations, differential blood count, blood gases, lactate, and interleukins were observed. The extracorporeal cell treatment was well tolerated by the animals. Conclusions:Extracorporeal therapy with granulocytic cells significantly improved survival in a pig model of sepsis. Further studies with this approach are encouraged.

Nano-coating protects biofunctional materials

The demand to develop convergent technology platforms, such as bio-functionalized medical devices, is rapidly increasing. However, the loss of biological function of the effector molecules during sterilization represents a significant and general problem. Therefore, we have developed and characterized a nano-coating (NC) formulation capable of maintaining the functionality of proteins on biological-device combination products. As a proof of concept, the NC preserved the structural and functional integrity of an otherwise highly fragile antibody immobilized on polyurethane during deleterious sterilizing irradiation (≥ 25 kGy). The NC procedure enables straight-forward terminal sterilization of bio-functionalized materials while preserving optimal conditioning of the bioactive surface.

Induction of protective immunity against H1N1 influenza A(H1N1)pdm09 with spray-dried and electron-beam sterilised vaccines in non-human primates

Currently, the need for cooled storage and the impossibility of terminal sterilisation are major drawbacks in vaccine manufacturing and distribution. To overcome current restrictions a preclinical safety and efficacy study was conducted to evaluate new influenza A vaccine formulations regarding thermal resistance, resistance against irradiation-mediated damage and storage stability. We evaluated the efficacy of novel antigen stabilizing and protecting solutions (SPS) to protect influenza A(H1N1)pdm09 split virus antigen under experimental conditions in vitro and in vivo. Original or SPS re-buffered vaccine (Pandemrix) was spray-dried and terminally sterilised by irradiation with 25 kGy (e-beam). Antigen integrity was monitored by SDS-PAGE, dynamic light scattering, size exclusion chromatography and functional haemagglutination assays. In vitro screening experiments revealed a number of highly stable compositions containing glycyrrhizinic acid (GA) and/or chitosan. The most stable composition was selected for storage tests and in vivo assessment of seroconversion in non-human primates (Macaca fascicularis) using a prime-boost strategy. Redispersed formulations with original adjuvant were administered intramuscularly. Storage data revealed high stability of protected vaccines at 4°C and 25°C, 60% relative humidity, for at least three months. Animals receiving original Pandemrix exhibited expected levels of seroconversion after 21 days (prime) and 48 days (boost) as assessed by haemagglutination inhibition and microneutralisation assays. Animals vaccinated with spray-dried and irradiated Pandemrix failed to exhibit seroconversion after 21 days whereas spray-dried and irradiated, SPS-protected vaccines elicited similar seroconversion levels to those vaccinated with original Pandemrix. Boost immunisation with SPS-protected vaccine resulted in a strong increase in seroconversion but had only minor effects in animals treated with non SPS-protected vaccine. In conclusion, utilising the SPS formulation technology, spray-drying and terminal sterilisation of influenza A(H1N1)pdm09 split virus vaccine is feasible. Findings indicate the potential utility of such formulated vaccines e.g. for needle-free vaccination routes and delivery to countries with uncertain cold chain facilities.

Selection of proangiogenic ascorbate derivatives and their exploitation in a novel drug‐releasing system for wound healing

The pathophysiology leading to delayed wound healing is complex and efficient therapeutic approaches for accelerated wound healing currently do not exist. We developed a novel drug‐eluting platform for the potential use in wound dressings. Here, we report on the potential of eluting ascorbic acid‐2‐phosphate (ASC‐2P), a highly stable variant of ascorbic acid, to induce angiogenesis and to promote collagen synthesis by fibroblasts. The drug‐eluting platform device (DEPD) consists of biocompatible polymeric layers comprising polyethylene terephtalate, polyvinyl alcohol (PVA), and polyurethane with PVA as the solvent for ASC‐2P. The angiogenic potential of ASC‐2P was evaluated in the endothelial cell tube formation assay (TFA) and in the chorion allantoic membrane (CAM) model. Collagen synthesis by ASC‐2P‐stimulated fibroblasts was determined by Sirius Red staining. ASC‐2P significantly induced angiogenesis in five independent TFA and CAM assays and induced collagen synthesis in two different fibroblast cell lines. The eluting kinetics of ASC‐2P was determined by the ultraviolet NanoDrop method and the functional 2,2′‐Azinobis‐(3‐ethylbenzthiazolin‐6‐sulfonic acid) method. Eluting profiles showed a continuous release in the range of biologically effective concentrations >10 days. This is the first report showing the proangiogenic‐ and collagen‐promoting features of ASC‐2P. DEPD loaded with ASC‐2P ought to be further evaluated as wound dressings or as supplementary pads for topical treatment of delayed wound healing in preclinical studies.

Stimulation of Fas signaling down-regulates activity of neutrophils from major trauma patients with SIRS

Posttrauma apoptosis resistance of neutrophils (PMN) is related to overshooting immune responses, systemic inflammatory response syndrome (SIRS) and multiple organ failure (MOF). Recently, we have shown that the apoptosis resistance in circulating PMN from severely injured patients which is known to be mediated by high serum levels of pro-inflammatory cytokines can be overcome by the activation of Fas death receptor. Here, we aimed to study whether stimulation of surface Fas leads to the inactivation of hyperactivated PMN from critically ill patients with SIRS. PMN from 23 multiple trauma patients (mean injury severity score (ISS) 34±1.9) were isolated at day 1 after admission to the trauma center. PMN from 17 volunteer blood donors served as controls. Neutrophil activity has been determined after ex vivo short (1 h) and long-term (4 h) stimulation of freshly isolated PMN with immobilized agonistic anti-Fas antibodies. We found neutrophil chemotactic migration in response to IL-8, phagocytosis and oxidative burst to be significantly inhibited in control cells already after short-term (1 h) Fas stimulation. In contrast, inactivation of trauma PMN by agonistic anti-Fas antibodies was found to be efficient only after long-term (4 h) incubation of cells with agonistic antibodies. Thus, in trauma PMN down-regulation of neutrophil activity seems to be delayed when compared to cells isolated from healthy controls, suggesting impaired susceptibility for Fas stimulation in these cells. Interestingly, whereas Fas-mediated inhibition of phagocytosis and oxidative burst could be prevented by the broad range caspase inhibitor t-butoxycarbonyl-aspartyl(O-methyl)-fluoromethyl ketone (BocD-fmk), the chemotactic activity in response to IL-8 was unaffected. In conclusion, we demonstrate that stimulation of neutrophil Fas does not only initiate apoptosis but also induces inhibition of neutrophil functions, partially by non-apoptotic signaling.

Plasma separation by centrifugation and subsequent plasma filtration: impact on survival in a pig model of sepsis.

The impact on survival of a combination of plasma separation by centrifugation and subsequent plasma filtration was tested in a bacterial sepsis model in pigs. In this animal study 19 pigs were included. Groups II and III received an intravenous lethal dose of live Staphylococcus aureus over 1 h; group I received saline (non‐septic control—NC). Groups I and II were treated by an extracorporeal circuit consisting of online centrifugation and subsequent plasma filtration (group II: treated group—TG) for 4 h; group III had no specific treatment (septic control, SC). The observation time was 7 days. All animals of group I (NC) and group II (TG) survived, while all animals of group III (SC) died during the observation time. Extracorporeal therapy with online centrifugation and plasma filtration significantly improved survival in a pig model of sepsis. Further studies with this approach are encouraged.