• Age-related susceptibility to Streptococcus pyogenes infection in mice: underlying immune dysfunction and strategy to enhance immunity.

      Goldmann, Oliver; Lehne, Sabine; Medina, Eva; Infection Immunology Research Group, Department of Microbial Pathogenesis, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany. (2010-04)
      Epidemiological studies have shown that the elderly are at higher risk of severe Streptococcus pyogenes infections. In this study, we used a mouse model that displays the age-related loss of resistance to S. pyogenes infection seen in humans to investigate the impaired immune mechanism underlying the age-associated susceptibility to this pathogen. Young (2-3 months old) and aged (>20 months old) BALB/c mice were subcutaneously or intravenously inoculated with S. pyogenes and their capacity to control infection was compared. Aged mice showed faster progression of disease, earlier morbidity, and increased mortality when compared with young animals. Since macrophages are critical for host defence against S. pyogenes, we investigated whether susceptibility of aged mice may be due to an age-associated decline in the functionality of these cells. Our results showed that macrophages from aged mice were as capable as those from young animals to uptake and kill S. pyogenes, but the number of resident tissue macrophages was significantly reduced in the aged host. Treatment of aged mice with macrophage colony-stimulating factor (M-CSF) significantly increased the number of resident macrophages and improved their response to infection. Our results indicate that treatment with M-CSF can restore, at least in part, the mechanisms affected by immunosenescence and enhance the natural resistance of aged mice to infection with S. pyogenes.
    • Changed Expression of Cytoskeleton Proteins During Lung Injury in a Mouse Model of Infection.

      Ferrer-Navarro, Mario; Strehlitz, Anja; Medina, Eva; Vila, Jordi
      Infections by are a major cause of morbidity and mortality worldwide, often causing community-acquired pneumonia, otitis media and also bacteremia and meningitis. Studies on are mainly focused on its virulence or capacity to evade the host immune system, but little is known about the injury caused in lungs during a pneumococcal infection. Herein we investigated this issue comparing the proteome profile of lungs from infected mice with control mice by means of difference gel electrophoresis (DIGE) technology. In order to obtain reliable results three biological replicas were used, and four technical replicas were carried out in each biological replica. Proteomic comparison was performed at two time points: 24 and 48 h post infection. A total of 91 proteins were identified with different abundance. We found important changes in the protein profiles during pneumococcal infection mainly associated with regulation of vesicle-mediated transport, wound healing, and cytoskeleton organization. In conclusion, the results obtained show that the cytoskeleton of the host cell is modified in infection.
    • Contribution of interleukin-6/gp 130 signaling in hepatocytes to the inflammatory response in mice infected with Streptococcus pyogenes.

      Klein, Christian; Medina, Eva; Sander, Leif; Dierssen, Uta; Roskams, Tania; Mueller, Werner; Trautwein, Christian; Goldmann, Oliver; Medizinische Klinik III, University Hospital Aachen, Rheinisch-Westfalisch Techniche Hochschule Aachen, Aachen, Germany. christian.klein@dife.de (2007-09-01)
      BACKGROUND: Sepsis and septic shock caused by gram-positive bacteria have become increasingly frequent clinical problems. These conditions are accompanied by an overwhelming inflammation in which the liver plays a central role as a source and target of inflammatory mediators. Sepsis is still associated with high mortality rates, and new intervention strategies directed at ameliorating the extent of the inflammatory reaction are strongly needed. Here, we investigated whether blockage of the transducer gp130, a receptor involved in the regulation of the inflammatory response, might be useful in the treatment of experimental gram-positive sepsis. METHODS: An experimental model of gram-positive sepsis was used in which liver-specific gp130-deficient mice (FVB/n alfpCre+ gp130(LoxP/LoxP)) and wild-type mice (FVB/n gp130(LoxP/LoxP)) were intravenously infected with Streptococcus pyogenes. The following parameters were monitored: mortality, bacterial loads in systemic organs, serum inflammatory cytokine levels, and organ damage. RESULTS: We show that infected gp130-deficient mice survived significantly longer, had lower bacterial loads, and developed organ damage more slowly than infected wild-type mice. Furthermore, levels of interferon- gamma , interleukin-6, and the chemokine cytokine-induced neutrophil chemoattractant were significantly lower in gp130-deficient mice than in wild-type mice. Histopathological examination of livers showed lower amounts of neutrophil infiltration, apoptosis, and tissue damage in infected gp130-deficient mice than in wild-type mice. CONCLUSION: Our results demonstrate that the gp130 receptor is involved in the regulation of inflammation during gram-positive sepsis and that blockage of gp130 signaling in hepatocytes could constitute a novel target for adjunctive therapy in patients with sepsis.
    • Differential Contributions of the Complement Anaphylotoxin Receptors C5aR1 and C5aR2 to the Early Innate Immune Response against Staphylococcus aureus Infection.

      Horst, Sarah A; Itzek, Andreas; Klos, Andreas; Beineke, Andreas; Medina, Eva; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015)
      The complement anaphylatoxin C5a contributes to host defense against Staphylococcus aureus. In this study, we investigated the functional role of the two known C5a receptors, C5aR1 and C5aR2, in the host response to S. aureus. We found that C5aR1(-/)(-) mice exhibited greater susceptibility to S. aureus bloodstream infection than wild type and C5aR2(-/)(-) mice, as demonstrated by the significantly higher bacterial loads in the kidneys and heart at 24 h of infection, and by the higher levels of inflammatory IL-6 in serum. Histological and immunohistochemistry investigation of infected kidneys at 24 h after bacterial inoculation revealed a discrete infiltration of neutrophils in wild type mice but already well-developed abscesses consisting of bacterial clusters surrounded by a large number of neutrophils in both C5aR1(-/)(-) and C5aR2(-/)(-) mice. Furthermore, blood neutrophils from C5aR1(-/)(-) mice were less efficient than those from wild type or C5aR2(-/)(-) mice at killing S. aureus. The requirement of C5aR1 for efficient killing of S. aureus was also demonstrated in human blood after disrupting C5a-C5aR1 signaling using specific inhibitors. These results demonstrated a role for C5aR1 in S. aureus clearance as well as a role for both C5aR1 and C5aR2 in the orchestration of the inflammatory response during infection.
    • Disruption of Coronin 1 Signaling in T Cells Promotes Allograft Tolerance while Maintaining Anti-Pathogen Immunity.

      Jayachandran, Rajesh; Gumienny, Aleksandra; Bolinger, Beatrice; Ruehl, Sebastian; Lang, Mathias Jakob; Fucile, Geoffrey; Mazumder, Saumyabrata; Tchang, Vincent; Woischnig, Anne-Kathrin; Stiess, Michael; et al. (Elsevier (Cell Press), 2019-01-15)
      The ability of the immune system to discriminate self from non-self is essential for eradicating microbial pathogens but is also responsible for allograft rejection. Whether it is possible to selectively suppress alloresponses while maintaining anti-pathogen immunity remains unknown. We found that mice deficient in coronin 1, a regulator of naive T cell homeostasis, fully retained allografts while maintaining T cell-specific responses against microbial pathogens. Mechanistically, coronin 1-deficiency increased cyclic adenosine monophosphate (cAMP) concentrations to suppress allo-specific T cell responses. Costimulation induced on microbe-infected antigen presenting cells was able to overcome cAMP-mediated immunosuppression to maintain anti-pathogen immunity. In vivo pharmacological modulation of this pathway or a prior transfer of coronin 1-deficient T cells actively suppressed allograft rejection. These results define a coronin 1-dependent regulatory axis in T cells important for allograft rejection and suggest that modulation of this pathway may be a promising approach to achieve long-term acceptance of mismatched allografts.
    • Diversity of Bacteria Exhibiting Bile Acid-inducible 7α-dehydroxylation Genes in the Human Gut.

      Vital, Marius; Rud, Tatjana; Rath, Silke; Pieper, Dietmar H; Schlüter, Dirk; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2019-01-01)
      The secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA), formed by gut microbiota from primary bile acids via a multi-step 7α-dehydroxylation reaction, have wide-ranging effects on host metabolism and play an important role in health and disease. A few 7α-dehydroxylating strains have been isolated, where bile acid-inducible (bai) genes were organized in a gene cluster and encoded major enzymes involved. However, only little is known on diversity and abundance of intestinal bacteria catalysing DCA/LCA formation in the human gut in situ. In this study, we took the opportunity to screen metagenome-assembled genomes (MAGs) from sequence data of stool samples provided by two recent studies along with newly available gut-derived isolates for the presence of the bai gene cluster. We revealed in total 765 and 620 MAGs encoding the potential to form DCA/LCA that grouped into 21 and 26 metagenomic species, respectively. The majority of MAGs (92.4 and 90.3%) were associated with a Ruminococcaceae clade that still lacks an isolate, whereas less MAGs belonged to Lachnospiraceae along with eight new isolates (n total = 11) that contained the bai genes. Only a few MAGs were linked to Peptostreptococcaceae. Signatures for horizontal transfer of bai genes were observed. This study gives a comprehensive overview of the diversity of bai-exhibiting bacteria in the human gut highlighting the application of metagenomics to unravel potential functions hidden from current isolates. Eventually, isolates of the identified main MAG clade are required in order to prove their capability of 7α-dehydroxylating primary bile acids.
    • The expanding world of extracellular traps: not only neutrophils but much more.

      Goldmann, Oliver; Medina, Eva; Infection Immunology Research Group, Helmholtz Centre for Infection Research Braunschweig, Germany. (2012)
      The release of extracellular traps (ETs) is a recently described mechanism of innate immune response to infection. Although ETs have been intensely investigated in the context of neutrophil antimicrobial effector mechanisms, other immune cells such as mast cells, eosinophils, and macrophages can also release these structures. The different ETs have several features in common, regardless of the type of cells from which they originated, including a DNA backbone with embedded antimicrobial peptides, proteases, and histones. However, they also exhibit remarkable individual differences such as the type of sub-cellular compartments from where the DNA backbone originates (e.g., nucleus or mitochondria), the proportion of responding cells within the pool, and/or the molecular mechanism/s underlying the ETs formation. This review summarizes the knowledge accumulated in recent years regarding the complex and expanding world of ETs and their role in immune function with particular emphasis on the role of other immune cells rather than on neutrophils exclusively.
    • Fluorescent Inorganic-Organic Hybrid Nanoparticles

      Neumeier, B. Lilli; Khorenko, Mikhail; Alves, Frauke; Goldmann, Oliver; Napp, Joanna; Schepers, Ute; Reichardt, Holger M.; Feldmann, Claus; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany.
      Inorganic‐organic hybrid nanoparticles (IOH‐NPs) with a general composition [ZrO]2+[RDyeOPO3]2−, [Ln]3+n/3[RDye(SO3)n]n−, [Ln(OH)]2+n/2[RDye(SO3)n]n−, or [LnO]+n[RDye(SO3)n]n− (Ln: lanthanide) are a novel class of nanomaterials for fluorescence detection and optical imaging. IOH‐NPs are characterized by an extremely high load of the fluorescent dye (70–85 wt‐%), high photochemical stability, straightforward aqueous synthesis, low material complexity, intense emission and high cell uptake at low toxicity. Besides full‐color emission, IOH‐NPs are suitable for multimodal imaging, singlet‐oxygen generation as well as drug delivery and drug release. This focus review presents the material concept of the IOH‐NPs as well as their synthesis and characterization. Their characteristic features are illustrated by selected in vitro and in vivo studies to initiate application in biology and medicine.
    • Genome sequence of the pink-pigmented marine bacterium Loktanella hongkongensis type strain (UST950701-009P(T)), a representative of the Roseobacter group.

      Lau, Stanley Ck; Riedel, Thomas; Fiebig, Anne; Han, James; Huntemann, Marcel; Petersen, Jörn; Ivanova, Natalia N; Markowitz, Victor; Woyke, Tanja; Göker, Markus; et al. (2015)
      Loktanella hongkongensis UST950701-009P(T) is a Gram-negative, non-motile and rod-shaped bacterium isolated from a marine biofilm in the subtropical seawater of Hong Kong. When growing as a monospecies biofilm on polystyrene surfaces, this bacterium is able to induce larval settlement and metamorphosis of a ubiquitous polychaete tubeworm Hydroides elegans. The inductive cues are low-molecular weight compounds bound to the exopolymeric matrix of the bacterial cells. In the present study we describe the features of L. hongkongensis strain DSM 17492(T) together with its genome sequence and annotation and novel aspects of its phenotype. The 3,198,444 bp long genome sequence encodes 3104 protein-coding genes and 57 RNA genes. The two unambiguously identified extrachromosomal replicons contain replication modules of the RepB and the Rhodobacteraceae-specific DnaA-like type, respectively.
    • Global Regulation of Gene Expression by the MafR Protein of Enterococcus faecalis.

      Ruiz-Cruz, Sofía; Espinosa, Manuel; Goldmann, Oliver; Bravo, Alicia; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2015)
      Enterococcus faecalis is a natural inhabitant of the human gastrointestinal tract. However, as an opportunistic pathogen, it is able to colonize other host niches and cause life-threatening infections. Its adaptation to new environments involves global changes in gene expression. The EF3013 gene (here named mafR) of E. faecalis strain V583 encodes a protein (MafR, 482 residues) that has sequence similarity to global response regulators of the Mga/AtxA family. The enterococcal OG1RF genome also encodes the MafR protein (gene OG1RF_12293). In this work, we have identified the promoter of the mafR gene using several in vivo approaches. Moreover, we show that MafR influences positively the transcription of many genes on a genome-wide scale. The most significant target genes encode components of PTS-type membrane transporters, components of ABC-type membrane transporters, and proteins involved in the metabolism of carbon sources. Some of these genes were previously reported to be up-regulated during the growth of E. faecalis in blood and/or in human urine. Furthermore, we show that a mafR deletion mutant strain induces a significant lower degree of inflammation in the peritoneal cavity of mice, suggesting that enterococcal cells deficient in MafR are less virulent. Our work indicates that MafR is a global transcriptional regulator. It might facilitate the adaptation of E. faecalis to particular host niches and, therefore, contribute to its potential virulence.
    • Global transcriptome analysis in influenza-infected mouse lungs reveals the kinetics of innate and adaptive host immune responses.

      Pommerenke, Claudia; Wilk, Esther; Srivastava, Barkha; Schulze, Annika; Novoselova, Natalia; Geffers, Robert; Schughart, Klaus; Department of Infection Genetics, Helmholtz Centre for Infection Research and University of Veterinary Medicine Hannover, Braunschweig, Germany. (2012)
      An infection represents a highly dynamic process involving complex biological responses of the host at many levels. To describe such processes at a global level, we recorded gene expression changes in mouse lungs after a non-lethal infection with influenza A virus over a period of 60 days. Global analysis of the large data set identified distinct phases of the host response. The increase in interferon genes and up-regulation of a defined NK-specific gene set revealed the initiation of the early innate immune response phase. Subsequently, infiltration and activation of T and B cells could be observed by an augmentation of T and B cell specific signature gene expression. The changes in B cell gene expression and preceding chemokine subsets were associated with the formation of bronchus-associated lymphoid tissue. In addition, we compared the gene expression profiles from wild type mice with Rag2 mutant mice. This analysis readily demonstrated that the deficiency in the T and B cell responses in Rag2 mutants could be detected by changes in the global gene expression patterns of the whole lung. In conclusion, our comprehensive gene expression study describes for the first time the entire host response and its kinetics to an acute influenza A infection at the transcriptome level.
    • High-resolution transcriptomic analysis of the adaptive response of Staphylococcus aureus during acute and chronic phases of osteomyelitis.

      Szafranska, Anna K; Oxley, Andrew P A; Chaves-Moreno, Diego; Horst, Sarah A; Roßlenbroich, Steffen; Peters, Georg; Goldmann, Oliver; Rohde, Manfred; Sinha, Bhanu; Pieper, Dietmar H; et al. (2014)
      Osteomyelitis is a difficult-to-eradicate bone infection typically caused by Staphylococcus aureus. In this study, we investigated the in vivo transcriptional adaptation of S. aureus during bone infection. To this end, we determined the transcriptome of S. aureus during the acute (day 7) and chronic (day 28) phases of experimental murine osteomyelitis using RNA sequencing (RNA-Seq). We identified a total of 180 genes significantly more highly expressed by S. aureus during acute or chronic in vivo infection than under in vitro growth conditions. These genes encoded proteins involved in gluconeogenesis, proteolysis of host proteins, iron acquisition, evasion of host immune defenses, and stress responses. At the regulatory level, sarA and -R and saeR and -S as well as the small RNA RsaC were predominantly expressed by S. aureus during in vivo infection. Only nine genes, including the genes encoding the arginine deiminase (ADI) pathway and those involved in the stringent response, were significantly more highly expressed by S. aureus during the chronic than the acute stage of infection. Analysis by quantitative reverse transcription-PCR (qRT-PCR) of a subset of these in vivo-expressed genes in clinical specimens yielded the same results as those observed in the murine system. Collectively, our results show that during acute osteomyelitis, S. aureus induced the transcription of genes that mediate metabolic adaptation, immune evasion, and replication. During the chronic phase, however, S. aureus switched its transcriptional response from a proliferative to a persistence mode, probably driven by the severe deficiency in nutrient supplies. Interfering with the survival strategies of S. aureus during chronic infection could lead to more effective treatments.
    • Host-inherent variability influences the transcriptional response of Staphylococcus aureus during in vivo infection

      Thänert, Robert; Goldmann, Oliver; Beineke, Andreas; Medina, Eva; Helmholtz Centre for infection research. Inhoffenstr. 7. 38124 Braunschweig, Germany. (2017-02-03)
    • Host-inherent variability influences the transcriptional response of Staphylococcus aureus during in vivo infection.

      Thänert, Robert; Goldmann, Oliver; Beineke, Andreas; Medina, Eva; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-02-03)
      The rise of antibiotic resistance calls for alternative strategies to treat bacterial infections. One attractive strategy is to directly target bacterial virulence factors with anti-virulence drugs. The expression of virulence traits by pathogens is, however, not constitutive but rather induced by the level of stress encountered within the host. Here we use dual RNA sequencing (RNA-seq) to show that intrinsic variability in the level of host resistance greatly affects the pathogen's transcriptome in vivo. Through analysis of the transcriptional profiles of host and pathogen during Staphylococcus aureus infection of two mouse strains, shown to be susceptible (A/J) or resistant (C57BL/6) to the pathogen, we demonstrate that the expression of virulence factors is dependent on the encountered host resistance. We furthermore provide evidence that this dependence strongly influences the efficacy of anti-virulence strategies, highlighting a potential limitation for the implementation of these strategies.
    • Identification of a novel subset of myeloid-derived suppressor cells during chronic staphylococcal infection that resembles immature eosinophils.

      Goldmann, Oliver; Beineke, Andreas; Medina, Eva; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunchweig, Germany. (2017-09-23)
      We have previously reported that myeloid-derived suppressor cells (MDSC), which are a heterogeneous population of immunosuppressive immature myeloid cells, expanded during chronic Staphylococcus aureus infection and promoted bacterial persistence by inhibiting effector T cells. Two major MDSC subsets including monocytic MDSCs (M-MDSC) and granulocytic MDSCs (G-MDSC) have been described to date. Here, we identified a new subset of MDSC (Eo-MDSC) in S. aureus-infected mice that phenotypically resembles eosinophils. Eo-MDSC exhibit eosinophilic cytoplasmic granules and express CD11b, the eosinophil marker Syglec-F, variable levels of CCR3 and low levels of IL-5R. Furthermore, Eo-MDSC accumulated at the site of infection and exerted a potent immunosuppressive effect on T cell responses that was mediated by nitric oxide-dependent depletion of L-arginine. Increased in the number of Eo-MDSC by adoptive transfer caused a significant exacerbation of infection in S. aureus-infected mice. This study sheds new light on the heterogeneity and complexity of MDSC during chronic infection.
    • IL-10 Plays Opposing Roles during Staphylococcus aureus Systemic and Localized Infections.

      Leech, John M; Lacey, Keenan A; Mulcahy, Michelle E; Medina, Eva; McLoughlin, Rachel M (2017-03-15)
      IL-10 is a potent anti-inflammatory mediator that plays a crucial role in limiting host immunopathology during bacterial infections by controlling effector T cell activation. Staphylococcus aureus has previously been shown to manipulate the IL-10 response as a mechanism of immune evasion during chronic systemic and biofilm models of infection. In the present study, we demonstrate divergent roles for IL-10 depending on the site of infection. During acute systemic S. aureus infection, IL-10 plays an important protective role and is required to prevent bacterial dissemination and host morbidity by controlling effector T cells and the associated downstream hyperactivation of inflammatory phagocytes, which are capable of host tissue damage. CD19(+)CD11b(+)CD5(+) B1a regulatory cells were shown to rapidly express IL-10 in a TLR2-dependent manner in response to S. aureus, and adoptive transfer of B1a cells was protective during acute systemic infection in IL-10-deficient hosts. In contrast, during localized s.c. infection, IL-10 production plays a detrimental role by facilitating bacterial persistence via the same mechanism of controlling proinflammatory T cell responses. Our findings demonstrate that induction of IL-10 has a major influence on disease outcome during acute S. aureus infection. Too much IL-10 at one end of the scale may suppress otherwise protective T cell responses, thus facilitating persistence of the bacteria, and at the other end, too little IL-10 may tend toward fatal host-mediated pathology through excessive activation of T cells and associated phagocyte-mediated damage.
    • Immune recognition of Streptococcus pyogenes by dendritic cells.

      Loof, Torsten G; Goldmann, Oliver; Medina, Eva; Infection Immunology Research Group, Department of Microbial Pathogenesis, Helmholtz Center for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2008-06)
      Streptococcus pyogenes is one of the most frequent human pathogens. Recent studies have identified dendritic cells (DCs) as important contributors to host defense against S. pyogenes. The objective of this study was to identify the receptors involved in immune recognition of S. pyogenes by DCs. To determine whether Toll-like receptors (TLRs) were involved in DC sensing of S. pyogenes, we evaluated the response of bone marrow-derived DCs obtained from mice deficient in MyD88, an adapter molecule used by almost all TLRs, following S. pyogenes stimulation. Despite the fact that MyD88(-/-) DCs did not differ from wild-type DCs in the ability to internalize and kill S. pyogenes, the up-regulation of maturation markers, such as CD40, CD80, and CD86, and the production of inflammatory cytokines, such as interleukin-12 (IL-12), IL-6, and tumor necrosis factor alpha, were dramatically impaired in S. pyogenes-stimulated MyD88(-/-) DCs. These results suggest that signaling through TLRs is the principal pathway by which DCs sense S. pyogenes and become activated. Surprisingly, DCs deficient in signaling through each of the TLRs reported as potential receptors for gram-positive cell components, such as TLR1, TLR2, TLR4, TLR9, and TLR2/6, were not impaired in the secretion of proinflammatory cytokines and the up-regulation of costimulatory molecules after S. pyogenes stimulation. In conclusion, our results exclude a major involvement of a single TLR or the heterodimer TLR2/6 in S. pyogenes sensing by DCs and argue for a multimodal recognition in which a combination of several different TLR-mediated signals is essential for a rapid and effective response to the pathogen.
    • An Interferon Signature Discriminates Pneumococcal From Staphylococcal Pneumonia.

      Strehlitz, Anja; Goldmann, Oliver; Pils, Marina C; Pessler, Frank; Medina, Eva; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany.; TWINCORE, Zentrum für experimentelle und klinische Infektionsforschung GmbH,Feodor-Lynen Str. 7, 30625 Hannover, Germany. (Frontiers, 2018-01-01)
      Streptococcus pneumoniae is the most common cause of community-acquired pneumonia (CAP). Despite the low prevalence of CAP caused by methicillin-resistant Staphylococcus aureus (MRSA), CAP patients often receive empirical antibiotic therapy providing coverage for MRSA such as vancomycin or linezolid. An early differentiation between S. pneumoniae and S. aureus pneumonia can help to reduce the use of unnecessary antibiotics. The objective of this study was to identify candidate biomarkers that can discriminate pneumococcal from staphylococcal pneumonia. A genome-wide transcriptional analysis of lung and peripheral blood performed in murine models of S. pneumoniae and S. aureus lung infection identified an interferon signature specifically associated with S. pneumoniae infection. Prediction models built using a support vector machine and Monte Carlo cross-validation, identified the combination of the interferon-induced chemokines CXCL9 and CXCL10 serum concentrations as the set of biomarkers with best sensitivity, specificity, and predictive power that enabled an accurate discrimination between S. pneumoniae and S. aureus pneumonia. The predictive performance of these biomarkers was further validated in an independent cohort of mice. This study highlights the potential of serum CXCL9 and CXCL10 biomarkers as an adjunctive diagnostic tool that could facilitate prompt and correct pathogen-targeted therapy in CAP patients.
    • Iron-chelating agent desferrioxamine stimulates formation of neutrophil extracellular traps (NETs) in human blood-derived neutrophils.

      Völlger, Lena; Akong-Moore, Kathryn; Cox, Linda; Goldmann, Oliver; Wang, Yanming; Schäfer, Simon T; Naim, Hassan Y; Nizet, Victor; von Köckritz-Blickwede, Maren; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-07)
      Neutrophil extracellular trap (NET) formation is a significant innate immune defense mechanism against microbial infection that complements other neutrophil functions including phagocytosis and degranulation of antimicrobial peptides. NETs are decondensed chromatin structures in which antimicrobial components (histones, antimicrobial peptides and proteases) are deployed and mediate immobilization of microbes. Here we describe an effect of iron chelation on the phenotype of NET formation. Iron-chelating agent desferrioxamine (DFO) showed a modest but significant induction of NETs by freshly isolated human neutrophils as visualized and quantified by immunocytochemistry against histone-DNA complexes. Further analyses revealed that NET induction by iron chelation required NADPH-dependent production of reactive oxygen species (ROS) as well as protease and peptidyl-arginine-deiminase 4 (PAD4) activities, three key mechanistic pathways previously linked to NET formation. Our results demonstrate that iron chelation by DFO contributes to the formation of NETs and suggest a target for pharmacological manipulation of NET activity.
    • Longitudinal proliferation mapping in vivo reveals NADPH oxidase-mediated dampening of Staphylococcus aureus growth rates within neutrophils.

      Seiß, Elena A; Krone, Anna; Formaglio, Pauline; Goldmann, Oliver; Engelmann, Susanne; Schraven, Burkhart; Medina, Eva; Müller, Andreas J; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Nature publishing group, 2019-04-05)
      Upon the onset of inflammatory responses, bacterial pathogens are confronted with altered tissue microenvironments which can critically impact on their metabolic activity and growth. Changes in these parameters have however remained difficult to analyze over time, which would be critical to dissect the interplay between the host immune response and pathogen physiology. Here, we established an in vivo biosensor for measuring the growth rates of Staphylococcus aureus (S. aureus) on a single cell-level over days in an ongoing cutaneous infection. Using intravital 2-photon imaging and quantitative fluorescence microscopy, we show that upon neutrophil recruitment to the infection site and bacterial uptake, non-lethal dampening of S. aureus proliferation occurred. This inhibition was supported by NADPH oxidase activity. Therefore, reactive oxygen production contributes to pathogen containment within neutrophils not only by killing S. aureus, but also by restricting the growth rate of the bacterium.