Fanny N. Lauw

Proinflammatory Effects of IL-10 During Human Endotoxemia

IL-10 is considered a potent antiinflammatory cytokine that strongly inhibits the production of proinflammatory cytokines. Recent studies have suggested that IL-10 also has immunostimulatory properties on CD4+, CD8+ T cells, and/or NK cells, resulting in increased IFN-γ production. To determine the effect of IL-10 on IFN-γ production and related inflammatory responses in humans, 16 healthy subjects received a bolus i.v. injection of LPS (4 ng/kg) in combination with either placebo or recombinant human IL-10 (25 μg/kg), administered just before or 1 h after LPS. IL-10 treatment, particularly when administered after LPS, enhanced LPS-induced IFN-γ release, as well as the release of the IFN-γ-dependent chemokines IFN-γ-inducible protein-10 and monokine induced by IFN-γ, while inhibiting or not influencing the production of IFN-γ-inducing cytokines. In addition, IL-10 treatment enhanced activation of CTLs and NK cells after LPS injection, as reflected by increased levels of soluble granzymes. These data indicate that high-dose IL-10 treatment in patients with inflammatory disorders can be associated with undesired proinflammatory effects.

Elevated Plasma Concentrations of Interferon (IFN)-γ and the IFN-γ—Inducing Cytokines Interleukin (IL)-18, IL-12, and IL-15 in Severe Melioidosis

Interferon (IFN)-gamma plays an important role in the pathogenesis of sepsis. Production of IFN-gamma is stimulated by synergistic effects of interleukin (IL)-18, IL-12, and IL-15. To investigate the regulation of IFN-gamma production during severe gram-negative infection, the plasma concentrations of IFN-gamma, IL-18, IL-12, and IL-15 were measured in 83 patients with suspected melioidosis. The diagnosis was confirmed in 62 patients, 31 of whom had blood cultures positive for Burkholderia pseudomallei, of whom 12 died. Compared with healthy controls, patients had elevated levels of IFN-gamma, IL-18, IL-12p40, and IL-15 on admission, with significantly higher levels in blood culture-positive patients, and these levels remained elevated during the 72-h study period. In whole blood stimulated with heat-killed B. pseudomallei, anti-IL-12 had a stronger inhibitory effect than anti-IL-18 and anti-IL-15 on IFN-gamma production. This effect of anti-IL-12 was further enhanced by anti-IL-18. These data suggest that during gram-negative sepsis, IFN-gamma production is controlled at least in part by endogenous IL-18, IL-12, and IL-15.

IL-18 Improves the Early Antimicrobial Host Response to Pneumococcal Pneumonia

To determine the role of endogenous IL-18 during pneumonia, IL-18 gene-deficient (IL-18−/−) mice and wild-type (WT) mice were intranasally inoculated with Streptococcus pneumoniae, the most common causative agent of community-acquired pneumonia. Infection with S. pneumoniae increased the expression of IL-18 mRNA and was associated with elevated concentrations of both precursor and mature IL-18 protein within the lungs. IL-18−/− mice had significantly more bacteria in their lungs and were more susceptible for progressing to systemic infection at 24 and 48 h postinoculation. Similarly, treatment of WT mice with anti-IL-18 was associated with enhanced outgrowth of pneumococci. In contrast, the clearance of pneumococci from lungs of IL-12−/− mice was unaltered when compared with WT mice. Furthermore, anti-IL-12 did not influence bacterial clearance in either IL-18−/− or WT mice. These data suggest that endogenous IL-18, but not IL-12, plays an important role in the early antibacterial host response during pneumococcal pneumonia.

Soluble Granzymes Are Released during Human Endotoxemia and in Patients with Severe Infection Due to Gram-Negative Bacteria

Extracellular release of granzymes is considered to reflect the involvement of cytotoxic T lymphocytes and NK cells in various disease states. To obtain insight into granzyme release during bacterial infection, granzyme levels were measured during experimental human endotoxemia and in patients with melioidosis, a severe infection due to gram-negative bacteria. Plasma concentrations of granzyme A (GrA) and GrB increased transiently after endotoxin administration, peaking after 2-6 h. In patients with bacteremic melioidosis, GrA and GrB levels were elevated on admission and remained high during the 72-h study period. In whole blood stimulated with heat-killed Burkholderia pseudomallei, neutralization of tumor necrosis factor, interleukin-12, or interleukin-18 inhibited granzyme secretion, which was independent of interferon-gamma. Stimulation with endotoxin and other gram-negative and gram-positive bacteria also strongly induced the secretion of granzymes, suggesting that granzyme release is a general immune response during bacterial infection. The interaction between the cytokine network and granzymes may play an important immunoregulatory role during bacterial infections.

Interleukin-12 Induces Sustained Activation of Multiple Host Inflammatory Mediator Systems in Chimpanzees

To determine in vivo effects of interleukin (IL)-12 on host inflammatory mediator systems, 4 healthy chimpanzees received recombinant human IL-12 (1 microg/kg) by intravenous injection. IL-12 induced increases in plasma concentrations of IL-15, IL-18, and interferon-gamma (IFN-gamma), plus a marked antiinflammatory cytokine response (IL-10, soluble tumor necrosis factor [TNF] receptors, IL-1 receptor antagonist) and secretion of alpha-chemokines (IL-8, IFN-gamma-inducible protein 10) and beta-chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-1beta). In addition, IL-12 elicited neutrophilic leukocytosis, neutrophil degranulation (elastase-alpha1-antitrypsin complexes), coagulation activation (F1 + 2 prothrombin fragment, thrombin-antithrombin III complexes), and fibrinolytic activation (tissue-type plasminogen activator, plasmin-alpha2-antiplasmin complexes). IL-12-induced activation of multiple host mediator systems was found only after 8-24 h, remained detectable until the end of the 48-h observation period, and occurred in the absence of detectable TNF and IL-1beta. These data may contribute to understanding the role of IL-12 in the pathogenesis of sepsis syndrome and the toxicity found after repeated injections of IL-12.

The CXC Chemokines Gamma Interferon (IFN-γ)-Inducible Protein 10 and Monokine Induced by IFN-γ Are Released during Severe Melioidosis

ABSTRACT Gamma interferon (IFN-γ)-inducible protein 10 (IP-10) and monokine induced by IFN-γ (Mig) are related CXC chemokines which bind to the CXCR3 receptor and specifically target activated T lymphocytes and natural killer (NK) cells. The production of IP-10 and Mig by various cell types in vitro is strongly dependent on IFN-γ. To determine whether IP-10 and Mig are released during bacterial infection in humans, we measured plasma levels of IP-10 and Mig in patients with melioidosis, a severe gram-negative infection caused byBurkholderia pseudomallei. IP-10 and Mig were markedly elevated in patients with melioidosis on admission, particularly in blood culture-positive patients, and remained elevated during the 72-h study period. Levels of IP-10 and Mig showed a positive correlation with IFN-γ concentrations and also correlated with clinical outcome. In whole blood stimulated with heat-killed B. pseudomallei, neutralization of IFN-γ and tumor necrosis factor alpha (TNF-α) partly attenuated IP-10 and Mig release, while anti-interleukin-12 (IL-12) and anti-IL-18 had a synergistic effect. Stimulation with other bacteria or endotoxin also induced strong secretion of IP-10 and Mig. These data suggest that IP-10 and Mig are part of the innate immune response to bacterial infection. IP-10 and Mig may contribute to host defense in Th1-mediated host defense during infections by attracting CXCR3+ Th1 cells to the site of inflammation.

The Role of Interferon-γ in Murine Pneumococcal Pneumonia

mice. In contrast, mice treated with anti–I FN-g did not demonstrate a consistently altered bacterial outgrowth, compared with mice treated with a control antibody. These data suggest that endogenous IFN-g, despite its protective role in defense against intracellular pathogens, does not serve a protective role during pneumococcal pneumonia. Streptococcus pneumoniae is a gram-positive bacterium responsible for .50% of the cases of community-acquired pneumonia. Pneumococcal pneumonia is the fifth leading cause of death worldwide, and, among patients with communityacquired pneumonia who require hospitalization, the mortality rate is as high as 25% [1, 2]. Against this background, and because of the growing resistance of the pneumococcus to antimicrobial therapy, it is important to gain insight into the pathogenesis of pneumococcal pneumonia [3]. Innate defense mechanisms play an important role in the elimination of bacteria from the alveolus. Phagocytic cells, as well as residential NK cells and T cells, participate in this response via the elaboration of chemotactic and regulatory cytokines [4]. Interferon (IFN)‐g is a potent proinflammatory cytokine, produced mainly by antigen-activated T and NK cells. IFN-g exerts several immune regulatory activities, including activation of phagocytes, stimulation of antigen presentation by increasing the expression of class I and II major histocompatibility complex molecules on antigen-presenting cells, orchestration of leukocyteendothelium interactions, and stimulation of the respiratory

Reduced Th1, but Not Th2, Cytokine Production by Lymphocytes after In Vivo Exposure of Healthy Subjects to Endotoxin

ABSTRACT Endotoxin (lipopolysaccharide [LPS]) tolerance is characterized by a reduced capacity of monocytes to produce proinflammatory cytokines upon restimulation in vitro. To determine whether LPS exposure induces a change in lymphocyte cytokine production and whether this results in a shift in the T-helper 1 (Th1)/Th2 balance, whole blood obtained from seven healthy subjects before and after an intravenous injection of LPS (4 ng/kg) was stimulated in vitro with the T-cell stimulus anti-CD3/CD28 or staphylococcal enterotoxin B. Whole-blood production of the Th1 cytokines gamma interferon (IFN-γ) and interleukin-2 (IL-2) was markedly reduced at 3 and 6 h, while the production of the Th2 cytokines IL-4 and IL-5 was not influenced or was slightly increased. The IFN-γ/IL-4 ratio was strongly decreased at 6 h. Serum obtained after LPS exposure could slightly inhibit the release of IFN-γ but increased IL-4 production during stimulation of blood drawn from subjects not previously exposed to LPS. Normal serum also inhibited IFN-γ production, albeit to a lesser extent. LPS exposure influences lymphocyte cytokine production, resulting in a shift toward a Th2 cytokine response, an effect that may be mediated in part by soluble factors present in serum after LPS administration in vivo.

Interleukin 10 Inhibits the Release of CC Chemokines during Human Endotoxemia

Sixteen healthy subjects were intravenously injected with lipopolysaccharide (LPS), once with placebo and once with recombinant human interleukin (IL)-10 (25 microgram/kg), to determine the effect of IL-10 on LPS-induced production of macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and monocyte chemoattractant protein (MCP)-1. LPS induced transient increases in serum MIP-1alpha, MIP-1beta, and MCP-1. Pretreatment with IL-10 inhibited LPS-induced release of MIP-1alpha, MIP-1beta, and MCP-1. In whole blood in vitro, the IL-10-induced inhibition of MIP-1alpha and MIP-1beta release was equally potent in the presence or absence of an anti-tumor necrosis factor (TNF) antibody. Although isolated peripheral blood mononuclear cells produced more MIP-1alpha and MIP-1beta than neutrophils, the latter cells were more sensitive to the inhibiting effect of IL-10. IL-10 attenuates LPS-induced production of CC chemokines in human endotoxemia, whereby in vitro experiments suggest that, in the case of MIP-1alpha and MIP-1beta release, this effect is independent from an inhibitory effect on TNF production.

Risk Factors for Sexual Transmission of Hepatitis C Virus Among Human Immunodeficiency Virus-Infected Men Who Have Sex With Men: A Case-Control Study

Background. Since 2000, incidence of sexually acquired hepatitis C virus (HCV)-infection has increased among human immunodeficiency virus (HIV)-infected men who have sex with men (MSM). To date, few case-control and cohort studies evaluating HCV transmission risk factors were conducted in this population, and most of these studies were initially designed to study HIV-related risk behavior and characteristics. Methods. From 2009 onwards, HIV-infected MSM with acute HCV infection and controls (HIV-monoinfected MSM) were prospectively included in the MOSAIC (MSM Observational Study of Acute Infection with hepatitis C) study at 5 large HIV outpatient clinics in the Netherlands. Written questionnaires were administered, covering sociodemographics, bloodborne risk factors for HCV infection, sexual behavior, and drug use. Clinical data were acquired through linkage with databases from the Dutch HIV Monitoring Foundation. For this study, determinants of HCV acquisition collected at the inclusion visit were analyzed using logistic regression. Results. Two hundred thirteen HIV-infected MSM (82 MSM with acute HCV infection and 131 MSM without) were included with a median age of 45.7 years (interquartile range [IQR], 41.0–52.2). Receptive unprotected anal intercourse (adjusted odds ratio [aOR], 5.01; 95% confidence interval [CI], 1.63–15.4), sharing sex toys (aOR, 3.62; 95% CI, 1.04–12.5), unprotected fisting (aOR, 2.57; 95% CI, 1.02–6.44), injecting drugs (aOR, 15.62; 95% CI, 1.27–192.6), sharing straws when snorting drugs (aOR, 3.40; 95% CI, 1.39–8.32), lower CD4 cell count (aOR, 1.75 per cubic root; 95% CI, 1.19–2.58), and recent diagnosis of ulcerative sexually transmitted infection (aOR, 4.82; 95% CI, 1.60–14.53) had significant effects on HCV acquisition. Conclusions. In this study, both sexual behavior and biological factors appear to independently increase the risk of HCV acquisition among HIV-infected MSM.