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Highlights • IFN-γ reduces the phagocytosis of E. coli by LPS-stimulated peritoneal macrophages. • IFN-γ differentially modulates macrophage release of the TNF-α, IL-6, and KC. • IFN-γ reduces KC release by macrophages stimulated by agonists of TLR2, 4, and 9. • Elevated levels of IFN-γ might lead to reduced E. coli clearance during infections., Introduction Interferon-γ levels are increased upon viral infections and during inflamm-aging. Resistance to infections due to Escherichia coli (E. coli), a major cause of bacteriaemia and sepsis, is impaired in aged individuals, partly due to altered phagocytic capacity and cytokine release of immune cells. Here, we analyzed the effect of IFN-γ on phagocytosis of E. coli K1 and release of proinflammatory cytokines by macrophages in resting condition and upon stimulation with different bacterial Toll-like receptor (TLR) agonists. Methods Primary peritoneal macrophages from C57BL/6 mice were exposed to medium or stimulated with agonists of TLR4 (LPS), 1/2 (Pam3CSK4), and 9 (CpG-DNA) in the presence and absence of IFN-γ (100 U/ml) for 24 h. TNF-α, IL-6, and KC were measured in the cell culture supernatant by ELISA. Macrophages were exposed to viable E. coli K1. After 90 min, intracellular phagozytosed bacteria were quantified by quantitative plating. Results Macrophages treated with LPS 1 µg/ml in the presence of IFN-γ ingested more than 10-fold lower numbers of E. coli than macrophages treated with LPS alone. Phagocytosis of E. coli by macrophages in resting condition or upon stimulation with Pam3CSK4 or CpG was not significantly affected by IFN-γ. Cytokine release was differentially modulated by IFN-γ, with reduced KC release by TLR-stimulated macrophages in the presence of IFN-γ being the most striking effect. Conclusions In vitro, IFN-γ reduces the phagocytosis of E. coli by LPS-stimulated macrophages and differentially modulates cytokine release of macrophages activated by different bacterial TLR agonists. Elevated levels of IFN-γ might lead to reduced bacterial clearance and worse outcome of bacterial infections, e.g., in aged individuals and after viral infections and other inflammatory events.

Introduction Interferon-γ levels are increased upon viral infections and during inflamm-aging. Resistance to infections due to Escherichia coli (E. coli), a major cause of bacteriaemia and sepsis, is impaired in aged individuals, partly due to altered phagocytic capacity and cytokine release of immune cells. Here, we analyzed the effect of IFN-γ on phagocytosis of E. coli K1 and release of proinflammatory cytokines by macrophages in resting condition and upon stimulation with different bacterial Toll-like receptor (TLR) agonists. Methods Primary peritoneal macrophages from C57BL/6 mice were exposed to medium or stimulated with agonists of TLR4 (LPS), 1/2 (Pam3CSK4), and 9 (CpG-DNA) in the presence and absence of IFN-γ (100 U/ml) for 24 h. TNF-α, IL-6, and KC were measured in the cell culture supernatant by ELISA. Macrophages were exposed to viable E. coli K1. After 90 min, intracellular phagozytosed bacteria were quantified by quantitative plating. Results Macrophages treated with LPS 1 µg/ml in the presence of IFN-γ ingested more than 10-fold lower numbers of E. coli than macrophages treated with LPS alone. Phagocytosis of E. coli by macrophages in resting condition or upon stimulation with Pam3CSK4 or CpG was not significantly affected by IFN-γ. Cytokine release was differentially modulated by IFN-γ, with reduced KC release by TLR-stimulated macrophages in the presence of IFN-γ being the most striking effect. Conclusions In vitro, IFN-γ reduces the phagocytosis of E. coli by LPS-stimulated macrophages and differentially modulates cytokine release of macrophages activated by different bacterial TLR agonists. Elevated levels of IFN-γ might lead to reduced bacterial clearance and worse outcome of bacterial infections, e.g., in aged individuals and after viral infections and other inflammatory events.

BACKGROUND AND PURPOSE Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults and is characterised by high lethality and substantial cognitive disabilities in survivors. Here, we study the capacity of an established therapeutic agent, magnesium, to improve survival in pneumococcal meningitis by modulating the neurological effects of the major pneumococcal pathogenic factor pneumolysin. EXPERIMENTAL APPROACH We used mixed primary glial and acute brain slice cultures, pneumolysin injection in infant rats, a mouse meningitis model, and complementary approaches such as Western blot, a black lipid bilayer conductance assay and live imaging of primary glial cells. KEY RESULTS Treatment with therapeutic concentrations of magnesium chloride (500 mg/kg in animals and 2 mM in cultures) prevented pneumolysin-induced brain swelling and tissue remodelling both in brain slices and in animal models. In contrast to other divalent ions, which diminish the membrane binding of pneumolysin in non-therapeutic concentrations, magnesium delayed toxin-driven pore formation without affecting its membrane binding or the conductance profile of its pores. Finally, magnesium prolonged the survival and improved clinical condition of mice with pneumococcal meningitis in the absence of antibiotic treatment. CONCLUSIONS AND IMPLICATIONS Magnesium is a well-established and safe therapeutic agent that has demonstrated capacity for attenuating pneumolysin-triggered pathogenic effects on the brain. The improved animal survival and clinical condition in the meningitis model points to magnesium as a promising candidate for adjunctive treatment of pneumococcal meningitis together with antibiotic therapy.

Background. The adaptive immune system has been considered to play a minimal role in the early host response during bacterial meningitis. Methods. We investigated the progression and outcome of pneumococcal meningitis in Rag1(-/-) mice lacking functional B and T cells by assessing overall and symptom-free survival, bacteriological and histological studies, as well as flow cytometry and measurements of proinflammatory mediators. Results. The intracerebral injection of S. pneumoniae D39 induced the recruitment of B and T cells (CD4+, gamma delta and natural killer) into the brain of wild-type mice. Mice with no functional B and T cells developed clinical symptoms and succumbed to the infection earlier than the wild-type group. In the CNS, Rag1(-/-) mice showed lower levels of interleukin 1 beta, reduced microglial proliferation, and impaired granulocyte recruitment with an earlier spread of pneumococci into the bloodstream, compared with wild-type mice. Lack of B and T cells resulted in a severe impairment of bacterial clearance in blood, spleen, and liver and an exaggerated systemic inflammatory response. Conclusions. B and T cells are important effector cells delaying the spread of pneumococci from the brain to the systemic circulation and shaping the immune response, thereby prolonging the survival of the host in the absence of antibiotic treatment.

Geriatric animal models are crucial for a better understanding and an improved therapy of age-related diseases. We observed a high mortality of aged mice after anesthesia with a standard dose of ketamine/xylazine, an anesthetic regimen frequently used in laboratory veterinary medicine. C57BL/6-N mice at the age of 2.14 ± 0.23 months (young mice) and 26.31 ± 2.15 months (aged mice) were anesthetized by intraperitoneal injection of 2 mg ketamine and 0.2 mg xylazine. 4 of 26 aged mice (15.4%) but none of 26 young mice died within 15 min after injection of the anesthetics. The weight of aged mice was significantly higher than that of young mice (32.8 ± 5.4 g versus 23.2 ± 3.4 g, p

Microglia, innate immune cells of the CNS, sense infection and damage through overlapping receptor sets. Toll-like receptor (TLR) 4 recognizes bacterial lipopolysaccharide (LPS) and multiple injury-associated factors. We show that its co-receptor CD14 serves three non-redundant functions in microglia. First, it confers an up to 100-fold higher LPS sensitivity compared to peripheral macrophages to enable efficient proinflammatory cytokine induction. Second, CD14 prevents excessive responses to massive LPS challenges via an interferon β-mediated feedback. Third, CD14 is mandatory for microglial reactions to tissue damage-associated signals. In mice, these functions are essential for balanced CNS responses to bacterial infection, traumatic and ischemic injuries, since CD14 deficiency causes either hypo- or hyperinflammation, insufficient or exaggerated immune cell recruitment or worsened stroke outcomes. While CD14 orchestrates functions of TLR4 and related immune receptors, it is itself regulated by TLR and non-TLR systems to thereby fine-tune microglial damage-sensing capacity upon infectious and non-infectious CNS challenges.

The outcome of bacterial meningitis critically depends on the rapid initiation of bactericidal antibiotic therapy and adequate management of septic shock. In community-acquired meningitis, the choice of an optimum initial empirical antibiotic regimen depends on the regional resistance patterns. Pathogens resistant to antibacterials prevail in nosocomial bacterial meningitis. Dexamethasone is recommended as adjunctive therapy for community-acquired meningitis in developed countries. In comatose patients, aggressive measures to lower intracranial pressure

The putative protein tyrosine kinase (PTK) inhibitor tyrphostin AG126 has proven beneficial in various models of inflammatory disease. Yet molecular targets and cellular mechanisms remained enigmatic. We demonstrate here that AG126 treatment has beneficial effects in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. AG126 alleviates the clinical symptoms, diminishes encephalitogenic Th17 differentiation, reduces inflammatory CNS infiltration as well as microglia activation and attenuates myelin damage. We show that AG126 directly inhibits Bruton's tyrosine kinase (BTK), a PTK associated with B cell receptor and Toll-like receptor (TLR) signaling. However, BTK inhibition cannot account for the entire activity spectrum. Effects on TLR-induced proinflammatory cytokine expression in microglia involve AG126 hydrolysis and conversion of its dinitrile side chain to malononitrile (MN). Notably, while liberated MN can subsequently mediate critical AG126 features, full protection in EAE still requires delivery of intact AG126. Its anti-inflammatory potential and especially interference with TLR signaling thus rely on a dual mechanism encompassing BTK and a novel MN-sensitive target. Both principles bear great potential for the therapeutic management of disturbed innate and adaptive immune functions.

Despite the development of new antibiotic agents, mortality of pneumococcal meningitis remains high. In addition, meningitis results in severe long-term morbidity, most prominently cognitive deficits. Granulocyte colony-stimulating factor (G-CSF) stimulates proliferation and differentiation of hematopoietic progenitor cells and increases the number of circulating neutrophil granulocytes. This study investigated the effect of adjuvant G-CSF treatment on cognitive function after pneumococcal meningitis. C57BL/6 mice were infected by subarachnoid injection of Streptococcus pneumoniae serotype 3 and treated with ceftriaxone and G-CSF subcutaneously or ceftriaxone alone for 5 days. Clinical scores, motor performance, and mortality during bacterial meningitis were unaffected by adjuvant G-CSF treatment. No effect of G-CSF treatment on production of proinflammatory cytokines or activation of microglia or astrocytes was observed. The G-CSF treatment did, however, result in hippocampal neurogenesis and improved spatial learning performance 6 weeks after meningitis. These results suggest that G-CSF might offer a new adjuvant therapeutic approach in bacterial meningitis to reduce long-term cognitive deficits.

Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults and is characterized by high lethality and substantial cognitive disabilities in survivors. Here, we have studied the capacity of an established therapeutic agent, magnesium, to improve survival in pneumococcal meningitis by modulating the neurological effects of the major pneumococcal pathogenic factor, pneumolysin.We used mixed primary glial and acute brain slice cultures, pneumolysin injection in infant rats, a mouse meningitis model and complementary approaches such as Western blot, a black lipid bilayer conductance assay and live imaging of primary glial cells.Treatment with therapeutic concentrations of magnesium chloride (500 mg·kgMagnesium is a well-established and safe therapeutic agent that has demonstrated capacity for attenuating pneumolysin-triggered pathogenic effects on the brain. The improved animal survival and clinical condition in the meningitis model identifies magnesium as a promising candidate for adjunctive treatment of pneumococcal meningitis, together with antibiotic therapy.

Meningitis and meningoencephalitis caused by Escherichia coli are associated with high rates of mortality and neurological sequelae. A high prevalence of neurological disorders has been observed in geriatric populations at risk of hypovitaminosis D. Vitamin D has potent effects on human immunity, including induction of antimicrobial peptides (AMPs) and suppression of T-cell proliferation, but its influence on microglial cells is unknown. The purpose of the present study was to determine the effects of vitamin D deficiency on the phagocytosis rate, intracellular killing, and immune response of murine microglial cultures after stimulation with the Toll-like receptor (TLR) agonists tripalmitoyl- S -glyceryl-cysteine (TLR1/2), poly(I·C) (TLR3), lipopolysaccharide (TLR4), and CpG oligodeoxynucleotide (TLR9). Upon stimulation with high concentrations of TLR agonists, the release of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) was decreased in vitamin D-deficient compared to that in vitamin D-sufficient microglial cultures. Phagocytosis of E. coli K1 after stimulation of microglial cells with high concentrations of TLR3, -4, and -9 agonists and intracellular killing of E. coli K1 after stimulation with high concentrations of all TLR agonists were lower in vitamin D-deficient microglial cells than in the respective control cells. Our observations suggest that vitamin D deficiency may impair the resistance of the brain against bacterial infections.

Background: Pneumococcal virulence factors common to all serotypes, such as choline-binding proteins (CBPs), are promising therapeutic targets in pneumococcal infections. We studied the effect of a choline dendrimer with maximized binding affinity/specificity for CBPs on microglia-mediated pneumococcal phagocytosis. Methods: Pneumoccocal cultures were exposed to dendrimers containing 8 choline end groups or amino groups as controls, either from the beginning of bacterial growth or at the late exponential phase. The effect of long/short co-incubation was assessed in terms of bacterial morphological changes and increase in bacterial uptake by primary microglial cultures. Results: Inhibiting CBPs by micromolar concentrations of a choline dendrimer caused the formation of long pneumococcal chains that were readily phagocytosed by microglia. Enhanced phagocytosis was dendrimer dose-dependent. Long bacteria-dendrimer co-incubation (14 h) resulted in a higher bacterial uptake than short co-incubation (2 h; p < 0.001). Conclusions: Multivalent dendrimers containing choline end groups are promising antimicrobial agents for the management of pneumococcal diseases.

Follistatin (FS) is the binding protein of activin A and inhibits its actions. The activin/FS system participates in the fine tuning of the immune response, and concentrations of activin A and FS are elevated in serum of patients with sepsis. Intraperitoneal injection of FS markedly reduced mortality after lipopolysaccharide-induced inflammation in a mouse model. Here, we investigated whether FS also influences the disease course in a mouse model of sepsis induced by intraperitoneal injection of Escherichia coli K1, a gram-negative bacterium frequently causing septic bacterial infections. Intraperitoneal injection of 10 μg/mL FS 30 min before infection did not influence survival, weight, motor performance, or bacterial titers of the infected mice. Thus, we could not confirm the protective effect of FS observed during lipopolysaccharide-induced inflammation in our mouse model of E. coli sepsis. Although it is a promising therapeutic tool in chronic or acute inflammatory conditions not caused by virulent pathogens, FS does not seem to increase the resistance to bacterial infections.

Stimulation of murine primary microglia with Toll-like receptor (TLR) agonists enhances their ability to phagocytose and kill bacteria. Here we show that the viral TLR3 agonist poly(I:C) stimulates the release of cyto-/chemokines and nitric oxide by microglia. Poly(I:C) increases microglial phagocytosis and intracellular killing of Escherichia coli K1, a pathogenic encapsulated bacterial strain, after 30 and 90 min of co-incubation. Stimulation with a viral epitope may strengthen the resistance of the brain to bacterial infections in vivo. Our data encourage animal experiments with poly(I:C) derivatives to assess whether this approach can increase the resistance of the CNS against bacterial infections.

Meropenem is a broad-spectrum carbapenem antibiotic that is highly active against the pathogens causing meningitis. The aims of this study was to determine the efficacies of meropenem alone and combined with rifampin against two Streptococcus pneumoniae strains with different susceptibility to beta-lactams using the guinea pig meningitis model and compare them with the standard ceftriaxone plus vancomycin therapy. All treatments except rifampin were bactericidal from 6 h. The addition of rifampin did not improve the activity of meropenem alone. Our results provide good evidence of the efficacy of meropenem in the treatment of penicillin- and cephalosporin-susceptible and -resistant pneumococcal meningitis similar to that of ceftriaxone plus vancomycin, suggesting that meropenem might be a good option in the management of this infection.

Toll-like receptors (TLRs) are crucial pattern recognition receptors in innate immunity that are expressed in microglia, the resident macrophages of the brain. TLR2, -4, and -9 are important in the responses againstStreptococcus pneumoniae, the most common agent causing bacterial meningitis beyond the neonatal period. Murine microglial cultures were stimulated with agonists for TLR1/2 (Pam3CSK4), TLR4 (lipopolysaccharide), and TLR9 (CpG oligodeoxynucleotide) for 24 h and then exposed to either the encapsulated D39 (serotype 2) or the nonencapsulated R6 strain ofS. pneumoniae. After stimulation, the levels of interleukin-6 and CCL5 (RANTES [regulated upon activation normal T-cell expressed and secreted]) were increased, confirming microglial activation. The TLR1/2, -4, and -9 agonist-stimulated microglia ingested significantly more bacteria than unstimulated cells (P< 0.05). The presence of cytochalasin D, an inhibitor of actin polymerizaton, blocked >90% of phagocytosis. Along with an increased phagocytic activity, the intracellular bacterial killing was also increased in TLR-stimulated cells compared to unstimulated cells. Together, our data suggest that microglial stimulation by these TLRs may increase the resistance of the brain against pneumococcal infections.

Meropenem is a carbapenem antibiotic that is highly active against the pathogens causing meningitis. Results with meropenem in the experimental rabbit model of penumococcal meningitis have been controversial, and the possible role of renal dehydropeptidase I in meropenem efficacy has been suggested. The aim of this study was to determine the efficacy of meropenem in two meningitis models and the possible influence of the animal model over results. Two strains of Streptococcus pneumoniae with different susceptibility to beta-lactams have been used in a guinea pig model and the classical rabbit meningitis model. Meropenem was bactericidal at 6 h in the guinea pig model against both strains with a reduction of >4 log ufc/ml. In the rabbit model it was bactericidal at 6 h against the susceptible strain, but against the resistant 3/8 therapeutical failures were recorded at 6 h, being bactericidal at 24 h. In conclusion, meropenem has shown bactericidal activity in both experimental models. This work emphasises the importance of an adequate election of the animal model for the appropriate development of studies of antimicrobial efficacy. We believe that guinea pig should be considered the best choice among laboratory animal species when assessing meropenem efficacy.

We used a rabbit model to assess the effects of capsular serotype, genetic background and beta-lactam resistance on the course and severity of experimental meningitis. Meningitis was induced by five pneumococcal strains belonging to five different clones with known invasive potential: two serotype 3 strains (ST260(3) and Netherlands(3)-31 clones) and three serotype 23F strains with different beta-lactam susceptibility patterns (Spain(23F)-1 clone, Tennessee(23F)-4 clone and a double locus variant of the Tennessee(23F)-4 clone). Major differences in secondary bacteremia and mortality rates were observed between serotypes 3 and 23F, as were divergences in the CSF lactate, protein and lipoteichoic-teichoic acid concentrations. Minor differences in the CSF-induced inflammatory response were found among strains belonging to the same serotype. Our results suggest that capsular serotype might be the main factor determining the course and severity of pneumococcal meningitis and genetic background contributes to a lesser extent. The acquisition of beta-lactam resistance does not reduce the virulence of the invasive clones. Since five strains belonging to two serotypes were studied, our findings have to be confirmed with other pneumococcal serotypes.

To compare the efficacy of meropenem, ceftazidime, tobramycin and ceftazidime+tobramycin in a guinea-pig model of P. aeruginosa meningitis. After anesthesia, the atlanto-occipital membrane was punctured with a butterfly needle and 100 microl of a solution containing 10(6)CFU/ml of P. aeruginosa were injected directly into the cisterna magna. Four h later, therapy was initiated with saline or antibiotics given im for 48 h in doses that obtained CSF levels as in human meningitis: ceftazidime 200 mg/kg/8h, meropenem 200 mg/kg/8h, tobramycin 30 mg/kg/24h. Tobramycin was also given intracisternally. Animals were sacrificed at different time points. CSF and blood samples were collected and a meningeal swab was performed. Four hours after inoculation, bacterial concentration in CSF was 4 to 5log10CFU and mean WBC was 16,000/-l. All control animals died in 24h with a 12% increase in cerebral edema. All blood-cultures were negative. Ceftazidime, ceftazidime+tobramycin and meropenem reduced the CSF bacterial concentration at 8h by 2.5log10. At 48 h all CSF cultures were sterile but meningeal swab cultures remained positive in 30%. Our results suggest that meropenem may be at least as effective as ceftazidime and that the addition of tobramycin to ceftazidime may improve its efficacy.

BACKGROUND Pneumococcal proteins involved in the resistance against oxidative stress are present in all strains and therefore are potential antigens that could be suitable for new therapies and/or vaccines. Their role in the pathogenesis of pneumococcal meningitis has not been addressed. METHODS We investigated the individual contributions of extracellular thioredoxin lipoproteins (Etrx1 and Etrx2) and the intracellular and extracellular methionine sulfoxide reductases (SpMsrAB1 and SpMsrAB2, respectively) in the progression and outcome of pneumococcal meningitis, using Kaplan-Meier survival curves, bacteriological and histological studies, and measurements of proinflammatory mediators. RESULTS The absence of Etrx1, Etrx2, or SpMsrAB1 moderately attenuated virulence as compared to the wild-type strain but did not significantly affect bacterial growth in the brain and bloodstream. Loss of function of SpMsrAB2 alone, both Etrx proteins, or both SpMsrAB proteins resulted in a less severe course of infection, with low numbers of animals dying of infection, a lower risk of associated meningeal inflammation, and reduced bacterial densities in the cerebellum, blood, and spleen. CONCLUSIONS Our data support the importance of the extracellular redox repair system in virulence and its potential as a target for the design of new antimicrobials and vaccine formulations against Streptococcus pneumoniae.

Objectives The aim of the study was to determine the efficacy of teicoplanin, alone and in combination with ceftriaxone, in a rabbit model of cephalosporin-resistant pneumococcal meningitis, and to assess the effect of concomitant therapy with dexamethasone. Methods In vitro killing curves of teicoplanin, with and without ceftriaxone, were performed. Groups of eight animals per treatment were inoculated with a cephalosporin-resistant pneumococcal strain (penicillin MIC, 4 mg/L; ceftriaxone MIC, 2 mg/L; teicoplanin MIC, 0.03 mg/L) and treated over a 26 h period. Teicoplanin was administered at a dose of 15 mg/kg, alone and in combination with ceftriaxone at 100 mg/kg with or without dexamethasone at 0.25 mg/kg. CSF samples were collected at different time-points, and bacterial titres, white blood cell counts, lactate and protein concentrations and bacteriostatic/bactericidal titres were determined. Blood and CSF teicoplanin pharmacokinetic and pharmacodynamic parameters were determined. Results Teicoplanin alone promoted a decrease in bacterial counts at 6 h of -2.66 log cfu/mL and was bactericidal at 24 h, without therapeutic failures. Similar good results were obtained when dexamethasone was used simultaneously, in spite of the penetration of teicoplanin into the CSF being significantly reduced, from 2.31% to 0.71%. Teicoplanin and ceftriaxone combinations were synergic in vitro, but not in the meningitis model. Conclusions Teicoplanin alone was very effective in this model of cephalosporin-resistant pneumococcal meningitis. The use of concomitant dexamethasone resulted in lower CSF teicoplanin levels, but not in therapeutic failures. The combination of teicoplanin plus ceftriaxone and dexamethasone might be a good alternative for the empirical therapy of pneumococcal meningitis. Additional data should confirm our experiments, in advance of clinical trials to assess efficacy in humans.

Introduccion El aumento de cepas de Streptococcus pneumoniae con elevada resistencia a cefalosporinas supondria un problema en el tratamiento de las infecciones graves como la meningitis. Existen interrogantes sobre las caracteristicas de estas cepas, como su capacidad para producir infecciones o la respuesta inflamatoria que generan en el liquido cefalorraquideo Metodos Utilizando el modelo de meningitis neumococica en conejo, se estudio la patogenicidad y las posibles diferencias en determinados parametros inflamatorios de dos cepas de S. pneumoniae del serotipo 23F con distinta sensibilidad a betalactamicos. Las concentraciones inhibitorias minimas fueron: cepa A (penicilina, 4=g/ml; ceftriaxona/cefotaxima, 2μg/ml); y cepa B (penicilina, 0,12μg/ml; ceftriaxona/cefotaxima, 32μg/ml) Resultados La cepa A mostro una mayor presencia de bacteriemia secundaria y parametros inflamatorios superiores en las primeras etapas de la infeccion. La cepa B produjo edema cerebral, y mayor mortalidad y actividad inflamatoria a la hora 24 Conclusiones Ambas cepas generaron meningitis en el modelo animal. Las diferencias en la respuesta inflamatoria producida por las dos cepas podrian estar relacionadas con las variaciones que determinan el grado de resistencia a betalactamicos

The ability of microglial cells to phagocytose bacteria after stimulation with the endocannabinoid palmitoylethanolamide (PEA) was studied in vitro. PEA increased the phagocytosis of unencapsulated Streptococcus pneumoniae R6 and encapsulated Escherichia coli K1 by murine microglial cells significantly after 30 min of microglial stimulation. This suggested that stimulation of microglial cells by PEA can increase the resistance of the brain against CNS infections.

// Sandra Schutze 1, 2 , Sandra Ribes 1 , Annika Kaufmann 1 , Anja Manig 1 , Jorg Scheffel 1 , Sandra Redlich 1 , Stephanie Bunkowski 1 , Uwe-Karsten Hanisch 1 , Wolfgang Bruck 1 , Roland Nau 1, 3 1 Institute of Neuropathology, University Medical Center Gottingen, 37075 Gottingen, Germany 2 Department of Geriatrics, Agaplesion Diakonissen Krankenhaus, 60322 Frankfurt am Main, Germany 3 Department of Geriatrics, Evangelisches Krankenhaus Gottingen-Weende, 37075 Gottingen, Germany Correspondence to: Sandra Schutze, e-mail: sebert1@gwdg.de Keywords: aging, bacterial CNS infection, E. coli , microglia, macrophages, phagocytosis, innate immunity Received: October 21, 2014 Accepted: November 10, 2014 Published: November 26, 2014 ABSTRACT Incidence and mortality of bacterial meningitis are strongly increased in aged compared to younger adults demanding new strategies to improve prevention and therapy of bacterial central nervous system (CNS) infections the elderly. Here, we established a geriatric mouse model for an intracerebral E. coli infection which reflects the clinical situation in aged patients: After intracerebral challenge with E. coli K1, aged mice showed a higher mortality, a faster development of clinical symptoms, and a more pronounced weight loss. Elimination of bacteria and systemic inflammatory response were impaired in aged mice, however, the number of infiltrating leukocytes and microglial cells in the CNS of aged and young mice did not differ substantially. In vitro , primary microglial cells and peritoneal macrophages from aged mice phagocytosed less E. coli and released less NO and cyto-/chemokines compared to cells from young mice both without activation and after stimulation by agonists of TLR 2, 4, and 9. Our results suggest that the age-related decline of microglia and macrophage functions plays an essential role for the higher susceptibility of aged mice to intracerebral infections. Strategies to improve the phagocytic potential of aged microglial cells and macrophages appear promising for prevention and treatment of CNS infections in elderly patients.

The putative protein tyrosine kinase (PTK) inhibitor tyrphostin AG126 has proven beneficial in various models of inflammatory disease. Yet molecular targets and cellular mechanisms remained enigmatic. We demonstrate here that AG126 treatment has beneficial effects in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. AG126 alleviates the clinical symptoms, diminishes encephalitogenic Th17 differentiation, reduces inflammatory CNS infiltration as well as microglia activation and attenuates myelin damage. We show that AG126 directly inhibits Bruton's tyrosine kinase (BTK), a PTK associated with B cell receptor and Toll-like receptor (TLR) signaling. However, BTK inhibition cannot account for the entire activity spectrum. Effects on TLR-induced proinflammatory cytokine expression in microglia involve AG126 hydrolysis and conversion of its dinitrile side chain to malononitrile (MN). Notably, while liberated MN can subsequently mediate critical AG126 features, full protection in EAE still requires delivery of intact AG126. Its anti-inflammatory potential and especially interference with TLR signaling thus rely on a dual mechanism encompassing BTK and a novel MN-sensitive target. Both principles bear great potential for the therapeutic management of disturbed innate and adaptive immune functions.

An study on the influence of steric and electronic effects of a function attached at C-2 of furans in the yield and diastereoselectivity of [4 + 3] cycloaddition reactions with oxyallyl cations is presented. In almost all studied furans a cis diastereospecificity and a high endo diastereoselectivity is observed. Increasing bulkyness of the function attached at C-2 of furans, the endo diastereoselectivity increases, but yield decreases. Increasing the electronic density of the furan system, by an electron donating group at C-2, both yield and diastereoselectivity increase.

Pneumococcal virulence factors common to all serotypes, such as choline-binding proteins (CBPs), are promising therapeutic targets in pneumococcal infections. We studied the effect of a choline dendrimer with maximized binding affinity/specificity for CBPs on microglia-mediated pneumococcal phagocytosis.Pneumoccocal cultures were exposed to dendrimers containing 8 choline end groups or amino groups as controls, either from the beginning of bacterial growth or at the late exponential phase. The effect of long/short co-incubation was assessed in terms of bacterial morphological changes and increase in bacterial uptake by primary microglial cultures.Inhibiting CBPs by micromolar concentrations of a choline dendrimer caused the formation of long pneumococcal chains that were readily phagocytosed by microglia. Enhanced phagocytosis was dendrimer dose-dependent. Long bacteria-dendrimer co-incubation (14 h) resulted in a higher bacterial uptake than short co-incubation (2 h; p0.001).Multivalent dendrimers containing choline end groups are promising antimicrobial agents for the management of pneumococcal diseases.

The sentinel and immune functions of microglia require rapid and appropriate reactions to infection and damage. Their Toll-like receptors (TLRs) sense both as threats. However, whether activated microglia mount uniform responses or whether subsets conduct selective tasks is unknown. We demonstrate that murine microglia reorganize their responses to TLR activations postnatally and that this process comes with a maturation of TLR4-organized functions. Although induction of MHCI for antigen presentation remains as a pan-populational feature, synthesis of TNFα becomes restricted to a subset, even within adult central nervous system regions. Response heterogeneity is evident ex vivo, in situ, and in vivo, but is not limited to TNFα production or to TLR-triggered functions. Also, clearance activities for myelin under physiological and pathophysiological conditions, IFNγ-enforced upregulation of MHCII, or challenged inductions of other proinflammatory factors reveal dissimilar microglial contributions. Notably, response heterogeneity is also confirmed in human brain tissue. Our findings suggest that microglia divide by constitutive and inducible capacities. Privileged production of inflammatory mediators assigns a master control to subsets. Sequestration of clearance of endogenous material versus antigen presentation in exclusive compartments can separate potentially interfering functions. Finally, subsets rather than a uniform population of microglia may assemble the reactive phenotypes in responses during infection, injury, and rebuilding, warranting consideration in experimental manipulation and therapeutic strategies.

Activated microglia is considered to be involved in the progression of Alzheimer's disease (AD). We investigated the effect of amyloid-β(1-40) (Aβ(40) and exogenous agonists of Toll-like receptor (TLR) 1/2 (Pam(3)CSK(4)) and TLR4 (LPS) on neurons in primary murine neuron-microglia co-cultures. Neuronal viability, assessed by quantifying the number of intact neuronal extensions and their crossings using a newly developed Definiens Cognition Network Technology-based method, was significantly decreased after treatment with Pam(3)CSK(4), LPS, and Aβ(40). Combined treatment with Aβ(40) and Pam(3)CSK(4) or LPS had an additive effect. Hence, in patients with AD, synergistic microglial activation by Aβ and bacterial products during infections might contribute to disease progression.

Increasing the phagocytic activity of microglia could improve the resistance of immunocompromised patients to CNS infections. We studied the microglial responses upon stimulation with the Nod2 ligand muramyl dipeptide (MDP) alone or in combination with a TLR1/2, 3 or 4 agonist. MDP caused a mild release of NO, but induced neither a significant release of pro-inflammatory cytokines nor an expression of molecules associated with professional antigen presentation. Using the Escherichia coli K1 model, microglial pre-stimulation with MDP enhanced bacterial phagocytosis which was strengthened on TLR-pre-stimulated cells. Dual pre-stimulation of Nod2 and TLR1/2 or 4 caused maximal phagocytosis and intracellular killing.

Background: Neuronal injury in pneumococcal meningitis is a consequence of microglial activation and direct toxicity by bacterial products and systemic inflammation. Methods: The treatment effect of the TEPC-15 antibody recognizing teichoic and lipoteichoic acids was investigated in murine microglial cells and in a rabbit model of pneumococcal meningitis. Results: In vitro, the TEPC-15 antibody recognizing teichoic and lipoteichoic acids increased Streptococcus pneumoniae phagocytosis by murine microglial cells. In rabbit ceftriaxone-treated S. pneumoniae meningitis, intracisternal TEPC-15 reduced the density of apoptotic neurons in the hippocampal dentate gyrus (116 ± 70 vs. 221 ± 132/mm2; p = 0.03). Cerebrospinal fluid inflammatory parameters (protein, lactate, leukocytes, prostaglandins) were not reduced in TEPC-15-treated rabbits. Conclusion: Intracisternal treatment with the TEPC-15 antibody reduced neuronal damage probably by promoting rapid phagocytosis of bacterial products.

Lyme neuroborreliosis (LNB) is the most frequent tick-borne infectious disease of the central nervous system. In acute LNB and the rare chronic state of infection, patients can experience cognitive deficits such as attention and memory disturbances. During LNB, single compounds of Borrelia burgdorferi sensu lato are released into the subarachnoid space. To investigate the pathogenesis of neurologic dysfunction in LNB, we determined that the outer surface protein C (OspC), a major virulence factor of B. burgdorferi , stimulated mouse microglial cells in a dose-dependent manner to release nitric oxide (EC50 = 0.24 mg/L) in vitro. To mimic pathophysiologic conditions of long-term release of this bacterial component in vivo, we treated C57BL/6 mice with recombinant OspC from Borrelia garinii or buffer by intraventricular infusion and tested them for behavioral deficits. After 4weeks, brains were examined by routine histology and immunohistochemistry. Assessment of spatial learning and memory of treated mice during OspC exposure did not reveal significant differences from controls. Continuous exposure to intrathecal B. burgdorferi OspC led to activation of microglia and axonal damage without demonstrable cognitive impairment in experimental mice. These results suggest that long-term intrathecal exposure to OspC resulted in axonal damage that may underlie the neurologic manifestations in chronic LNB.

A study on the influence of steric and electronic effects of a function attached at C-2 of furans in the yield and diastereoselectivity of [4+3] cycloaddition reactions with oxyallyl cations is presented. In almost all studied furans a cis diastereospecificity and a high endo diastereoselectivity is observed. Increasing bulkyness of the function attached at C-2 of furans, increases the endo diastereoselectivity, but decreases yield. Increasing the electronic density of the furan system, by an electron donating group attached at C-2, increases yield and diastereoselectivity.

An study on the influence of steric and electronic effects of a function attached at C-2 of furans in the yield and diastereoselectivity of [4 + 3] cycloaddition reactions with oxyallyl cations is presented. In almost all studied furans a cis diastereospecificity and a high endo diastereoselectivity is observed. Increasing bulkyness of the function attached at C-2 of furans, the endo diastereoselectivity increases, but yield decreases. Increasing the electronic density of the furan system, by an electron donating group at C-2, both yield and diastereoselectivity increase.

The objective of this study was to evaluate the in vitro and in vivo efficacies of therapies including fosfomycin against clinical Staphylococcus aureus isolates with reduced susceptibility to vancomycin (hGISA). Time-kill curves were performed over 24 h. Peritonitis in C57BL/6 mice was induced by intraperitoneal inoculation of 10(8) CFU/ml. Four hours later (0 h), therapy was started and the treatment groups were: control (not treated), fosfomycin (100 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), fosfomycin plus linezolid, fosfomycin plus vancomycin and fosfomycin plus imipenem, receiving subcutaneous therapy over 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. In vitro, fosfomycin showed a synergistic effect when combined with the other antimicrobials tested. In the animal model, fosfomycin combinations were effective and significantly reduced the bacteraemia rates achieved in the control, imipenem and vancomycin groups (p 0.05). The best combination in vivo was fosfomycin plus imipenem. Also, fosfomycin plus linezolid was significantly better than vancomycin alone, reducing the bacterial concentration in the peritoneal fluid. In conclusion, in vitro and in vivo, fosfomycin in combination with linezolid, vancomycin or imipenem exerted a good activity. Fosfomycin plus imipenem was the most active combination, decreasing 3 log CFU/ml, and appears to be a promising combination for clinical practice.

Microglia express Toll-like receptors (TLRs) that recognize invading pathogens as well as endogenous proteins such as fibronectin under nonphysiological conditions. Here, we demonstrated that fibronectin stimulates murine microglia in culture in a dose-dependent manner: microglial cells secreted proinflammatory cytokines and chemokines and increased phagocytosis of Escherichia coli DH5alpha and E. coli K1 strains. Low levels of fibronectin exerted a synergistic effect on the release of proinflammatory compounds by microglia co-stimulated with agonists for TLR1/2 (Pam(3)CSK(4)) or TLR9 (CpG DNA), but not in combination with the TLR4 agonist lipopolysaccharide (LPS). Phagocytosis of bacterial strains was moderately enhanced when microglia was co-stimulated with high concentrations of fibronectin and one pathogen-derived TLR agonist. In conclusion, fibronectin increased proinflammatory and phagocytotic functions in microglia and partially synergized with microbial TLR agonists.

Meningitis and meningoencephalitis caused byEscherichia coliare associated with high rates of mortality. When an infection occurs, Toll-like receptors (TLRs) expressed by microglial cells can recognize pathogen-associated molecular patterns and activate multiple steps in the inflammatory response that coordinate the brain's local defense, such as phagocytosis of invading pathogens. An upregulation of the phagocytic ability of reactive microglia could improve the host defense in immunocompromised patients against pathogens such asE. coli. Here, murine microglial cultures were stimulated with the TLR agonists Pam3CSK4(TLR1/TLR2), lipopolysaccharide (TLR4), and CpG oligodeoxynucleotide (TLR9) for 24 h. Upon stimulation, levels of tumor necrosis factor alpha and the neutrophil chemoattractant CXCL1 were increased, indicating microglial activation. Phagocytic activity was studied after adding eitherE. coliDH5α orE. coliK1 strains. After 60 and 90 min of bacterial exposure, the number of ingested bacteria was significantly higher in cells prestimulated with TLR agonists than in unstimulated controls (P< 0.01). Addition of cytochalasin D, an inhibitor of actin polymerization, blocked >90% of phagocytosis. We also analyzed the ability of microglia to kill the ingestedE. colistrains. Intracellularly surviving bacteria were quantified at different time points (90, 150, 240, and 360 min) after 90 min of phagocytosis. The number of bacteria killed intracellularly after 6 h was higher in cells primed with the different TLR agonists than in unstimulated microglia. Our data suggest that microglial stimulation by the TLR system can increase bacterial phagocytosis and killing. This approach could improve central nervous system resistance to infections in immunocompromised patients.

Methods Primary cultures of mouse microglia were exposed to TLR agonists: tripalmitoyl-S-glyceryl-cysteine (Pam3CSK4 at 0.1 μg/ml; TLR2), endotoxin (LPS at 0.01 μg/ml; TLR4) and oligonucleotides containing unmethylated cytosinguanosin motifs (CpG at 1 μg/ml; TLR9) for 24 h. TLR agonists were used at the lowest concentrations inducing the maximum stimulation of microglia cells in terms of NO release. After stimulation, cultures were challenged with two S. pneumoniae strains: the encapsulated D39 or the unencapsulated R6 strains were added at a ratio of 100 bacteria per cell. Phagocytosis was left to proceed for 30 and 90 min at 37°C + 5% CO2. For phagocytosis inhibition studies, 10 μM cytochalasin D (CD) was used. After washing, the microglial cultures were incubated in medium containing gentamicin (200 μg/ml) for 1 h to kill extracellular bacteria. Thereafter, cells were washed and lysed with distilled water. Viable intracellular bacteria were enumerated by quantitative plating of serial 10-fold dilutions. To monitor intracellular survival, microglia cells were allowed to ingest bacteria for 30 min. Then, incubation in medium with gentamicin was performed for 1 h. Thereafter, viable intracellular bacteria were determined at various time points by quantitative plating after cell lysis. Kruskall-Wallis test followed by Dunn's multiple comparisons test was performed to compare phagocytosis between groups (n ≥ 10); p < 0.05 was considered statistically significant.