Systemic neutralization of interleukin-8 markedly reduces neutrophilic pleocytosis during experimental lipopolysaccharide-induced meningitis in rabbits

Bovine neutrophil chemotaxis to Listeria monocytogenes in neurolisteriosis depends on microglia-released rather than bacterial factors

BACKGROUND

Listeria monocytogenes (Lm) is a bacterial pathogen of major concern for humans and ruminants due to its neuroinvasive potential and its ability to cause deadly encephalitis (neurolisteriosis). On one hand, polymorphonuclear neutrophils (PMN) are key players in the defense against Lm, but on the other hand intracerebral infiltration with PMN is associated with significant neural tissue damage. Lm-PMN interactions in neurolisteriosis are poorly investigated, and factors inducing PMN chemotaxis to infectious foci containing Lm in the central nervous system (CNS) remain unidentified.

METHODS

In this study, we assessed bovine PMN chemotaxis towards Lm and supernatants of infected endogenous brain cell populations in ex vivo chemotaxis assays, to identify chemotactic stimuli for PMN chemotaxis towards Lm in the brain. In addition, microglial secretion of IL-8 was assessed both ex vivo and in situ.

RESULTS

Our data show that neither Lm cell wall components nor intact bacteria elicit chemotaxis of bovine PMN ex vivo. Moreover, astrocytes and neural cells fail to induce bovine PMN chemotaxis upon infection. In contrast, supernatant from Lm infected microglia readily induced chemotaxis of bovine PMN. Microglial expression and secretion of IL-8 was identified during early Lm infection in vitro and in situ, although IL-8 blocking with a specific antibody could not abrogate PMN chemotaxis towards Lm infected microglial supernatant.

CONCLUSIONS

These data provide evidence that host-derived rather than bacterial factors trigger PMN chemotaxis to bacterial foci in the CNS, that microglia have a primary role as initiators of bovine PMN chemotaxis into the brain during neurolisteriosis and that blockade of these factors could be a therapeutic target to limit intrathecal PMN chemotaxis and PMN associated damage in neurolisteriosis.

The Emerging Role of Pericyte-Derived Extracellular Vesicles in Vascular and Neurological Health

Pericytes (PCs), as a central component of the neurovascular unit, contribute to the regenerative potential of the central nervous system (CNS) and peripheral nervous system (PNS) by virtue of their role in blood flow regulation, angiogenesis, maintenance of the BBB, neurogenesis, and neuroprotection. Emerging evidence indicates that PCs also have a role in mediating cell-to-cell communication through the secretion of extracellular vesicles (EVs). Extracellular vesicles are cell-derived, micro- to nano-sized vesicles that transport cell constituents such as proteins, nucleic acids, and lipids from a parent originating cell to a recipient cell. PC-derived EVs (PC-EVs) play a crucial homeostatic role in neurovascular disease, as they promote angiogenesis, maintain the integrity of the blood-tissue barrier, and provide neuroprotection. The cargo carried by PC-EVs includes growth factors such as endothelial growth factor (VEGF), connecting tissue growth factors (CTGFs), fibroblast growth factors, angiopoietin 1, and neurotrophic growth factors such as brain-derived neurotrophic growth factor (BDNF), neuron growth factor (NGF), and glial-derived neurotrophic factor (GDNF), as well as cytokines such as interleukin (IL)-6, IL-8, IL-10, and MCP-1. The PC-EVs also carry miRNA and circular RNA linked to neurovascular health and the progression of several vascular and neuronal diseases. Therapeutic strategies employing PC-EVs have potential in the treatment of vascular and neurodegenerative diseases. This review discusses current research on the characteristic features of EVs secreted by PCs and their role in neuronal and vascular health and disease.

Toll-like receptor-induced cytokines as immunotherapeutic targets in cancers and autoimmune diseases

Immune cells of the myeloid and lymphoid lineages express Toll-like receptors (TLRs) to recognize pathogenic components or cellular debris and activate the immune system through the secretion of cytokines. Cytokines are signaling molecules that are structurally and functionally distinct from one another, although their secretion profiles and signaling cascades often overlap. This situation gives rise to pleiotropic cell-to-cell communication pathways essential for protection from infections as well as cancers. Nonetheless, deregulated signaling can have detrimental effects on the host, in the form of inflammatory or autoimmune diseases. Because cytokines are associated with numerous autoimmune and cancerous conditions, therapeutic strategies to modulate these molecules or their biological responses have been immensely beneficial over the years. There are still challenges in the regulation of cytokine function in patients, even in those who take approved biological therapeutics. In this review, our purpose is to discuss the differential expression patterns of TLR-regulated cytokines and their cell type specificity that is associated with cancers and immune-system-related diseases. In addition, we highlight key structural features and molecular recognition of cytokines by receptors; these data have facilitated the development and approval of several biologics for the treatment of autoimmune diseases and cancers.

Therapeutic inhibition of CXC chemokine receptor 2 by SB225002 attenuates LPS-induced acute lung injury in mice

INTRODUCTION

Sustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury (ALI). CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. The purpose of this study was to investigate the functional relevance of the CXCR2 inhibitor SB225002 in LPS-induced acute lung injury.

MATERIAL AND METHODS

Male C57BL/6 mice were randomly divided into the following four experimental groups (n = 10 per group): untreated group (control group, Ctr); LPS-treated ALI group (LPS group, LPS); LPS + PBS-treated group (LPS + PBS); and SB225002-treated ALI group (LPS + SB225002). Twenty-four hours after treatment, the blood, bronchoalveolar lavage fluid (BALF), and lung tissue were collected and wet/dry ratio, protein concentration, myeloperoxidase (MPO) activity, neutrophil infiltration, and inflammatory cytokine secretion in lung tissue were measured. The pathologic changes in the lungs were examined using optical microscopy. Survival rates were recorded at 120 h in all four groups, in other experiments.

RESULTS

Histology findings revealed that the SB225002-treated group had significantly milder lung injury compared to the LPS-induced ALI and the PBS-treated control groups. Treatment with SB225002 significantly attenuated LPS-induced lung injury and suppressed the inflammatory responses in damaged lung tissue. Compared to the PBS-treated control group, treatment with SB225002 dramatically decreased the lung wet/dry ratio, protein concentration, and infiltration of neutrophils in lung tissue. Therefore, SB225002 treatment appeared to inhibit the production of inflammatory cytokines and increase survival time compared to the PBS-treated control group.

CONCLUSIONS

Together, these data demonstrated that inhibition of CXCR2 signaling by SB225002 could ameliorate LPS-induced acute lung injury, by reducing neutrophil recruitment and vascular permeability. SB225002 may be further developed as a potential novel treatment for LPS-induced ALI.

Cytokines and chemokines at the crossroads of neuroinflammation, neurodegeneration, and neuropathic pain

Cytokines and chemokines are proteins that coordinate the immune response throughout the body. The dysregulation of cytokines and chemokines is a central feature in the development of neuroinflammation, neurodegeneration, and demyelination both in the central and peripheral nervous systems and in conditions of neuropathic pain. Pathological states within the nervous system can lead to activation of microglia. The latter may mediate neuronal and glial cell injury and death through production of proinflammatory factors such as cytokines and chemokines. These then help to mobilize the adaptive immune response. Although inflammation may induce beneficial effects such as pathogen clearance and phagocytosis of apoptotic cells, uncontrolled inflammation can result in detrimental outcomes via the production of neurotoxic factors that exacerbate neurodegenerative pathology. In states of prolonged inflammation, continual activation and recruitment of effector cells can establish a feedback loop that perpetuates inflammation and ultimately results in neuronal injury. A critical balance between repair and proinflammatory factors determines the outcome of a neurodegenerative process. This review will focus on how cytokines and chemokines affect neuroinflammation and disease pathogenesis in bacterial meningitis and brain abscesses, Lyme neuroborreliosis, human immunodeficiency virus encephalitis, and neuropathic pain.

Cerebrospinal-fluid cytokine and chemokine profile in patients with pneumococcal and meningococcal meningitis

Background

Bacterial meningitis is characterized by an intense inflammatory reaction contributing to neuronal damage. The aim of this study was to obtain a comparative analysis of cytokines and chemokines in patients with pneumococcal (PM) and meningococcal meningitis (MM) considering that a clear difference between the immune response induced by these pathogens remains unclear.

Methods

The cyto/chemokines, IL-1β, IL-2, IL-6, TNF-α, IFN-γ, IL-10, IL-1Ra, CXCL8/IL-8, CCL2/MCP-1, CLL3/MIP-1α, CCL4/MIP-1γ and G-CSF, were measured in cerebrospinal fluid (CSF) samples from patients with PM and MM. Additionally, a literature review about the expression of cytokines in CSF samples of patients with MB was made.

Results

Concerning cytokines levels, only IFN-γ was significantly higher in patients with Streptococcus pneumoniae compared to those with Neisseria meningitidis, regardless of the time when the lumbar puncture (LP) was made. Furthermore, when samples were compared considering the timing of the LP, higher levels of TNF-α (P <0.05) were observed in MM patients whose LP was made within 48 h from the initial symptoms of disease. We also observed that the index of release of cyto/chemokines per cell was significantly higher in PM. From the literature review, it was observed that TNF-α, IL-1β and IL-6 are the best studied cytokines, while reports describing the concentration of the cytokine IL-2, IL-1Ra, G-CSF and CCL4/MIP-1β in CSF samples of patients with bacterial meningitis were not found.

Conclusion

The data obtained in this study and the previously published data show a similar profile of cytokine expression during PM and MM. Nevertheless, the high levels of IFN-γ and the ability to release high levels of cytokines with a low number of cells are important factors to be considered in the pathogenesis of PM and thereby should be further investigated. Moreover, differences in the early response induced by the pathogens were observed. However, the differences observed are not sufficient to trigger changes in the current therapy of corticosteroids adopted in both the PM and MM.

A possible role for inflammation in mediating apoptosis of oligodendrocytes as induced by the Lyme disease spirochete Borrelia burgdorferi

Background

Inflammation caused by the Lyme disease spirochete B. burgdorferi is an important factor in the pathogenesis of Lyme neuroborreliosis. Our central hypothesis is that B. burgdorferi can cause disease via the induction of inflammatory mediators such as cytokines and chemokines in glial and neuronal cells. Earlier we demonstrated that interaction of B. burgdorferi with brain parenchyma induces inflammatory mediators in glial cells as well as glial (oligodendrocyte) and neuronal apoptosis using ex vivo and in vivo models of experimentation.

Methods

In this study we evaluated the ability of live B. burgdorferi to elicit inflammation in vitro in differentiated human MO3.13 oligodendrocytes and in differentiated primary human oligodendrocytes, by measuring the concentration of immune mediators in culture supernatants using Multiplex ELISA assays. Concomitant apoptosis was quantified in these cultures by the in situ terminal deoxynucleotidyl transferase mediated UTP nick end labeling (TUNEL) assay and by quantifying active caspase-3 by flow cytometry. The above phenomena were also evaluated after 48 h of stimulation with B. burgdorferi in the presence and absence of various concentrations of the anti-inflammatory drug dexamethasone.

Results

B. burgdorferi induced enhanced levels of the cytokine IL-6 and the chemokines IL-8 and CCL2 in MO3.13 cells as compared to basal levels, and IL-8 and CCL2 in primary human oligodendrocytes, in a dose-dependent manner. These cultures also showed significantly elevated levels of apoptosis when compared with medium controls. Dexamethasone reduced both the levels of immune mediators and apoptosis, also in a manner that was dose dependent.

Conclusions

This finding supports our hypothesis that the inflammatory response elicited by the Lyme disease spirochete in glial cells contributes to neural cell damage. As oligodendrocytes are vital for the functioning and survival of neurons, the inflammation and subsequent apoptosis of oligodendrocytes induced by B. burgdorferi could contribute to the pathogenesis of Lyme neuroborreliosis.

Oxidative stress in cerebrospinal fluid of patients with aseptic and bacterial meningitis

This study aimed to determine whether patients with aseptic and bacterial meningitis presented alterations in oxidative stress parameters of cerebrospinal fluid (CSF). A total of 30 patients were used in the research. The CSF oxidative stress status has been evaluated through many parameters, such as lipid peroxidation through thiobarbituric acid reactive substances (TBARS) and antioxidant defense systems such as superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and ascorbic acid. TBARS levels, SOD and GST activity increase in aseptic meningitis and in bacterial meningitis. The ascorbic acid concentration increased significantly in patients with both meningitis types. The reduced glutathione levels were reduced in CSF of patients with aseptic and bacterial meningitis. In present study we may conclude that oxidative stress contributes at least in part to the severe neurological dysfunction found in meningitis.

Immune and Inflammatory Responses in GERD and Lansoprazole

The exact pathophysiological mechanisms responsible for gastroesophageal reflux disease (GERD) remain unclear. Recent studies have shown that mucosal immune and inflammatory responses, characterized by specific cytokine and chemokine profiles, may underlie the diverse esophageal phenotypes of GERD. Interleukin 8 (IL-8), a representative chemokine, mediates neutrophil trafficking via its receptors, mainly CXCR-1. The IL-8 mRNA and protein levels are increased in the esophageal mucosa, not only in reflux esophagitis (RE), but also in endoscopy-negative GERD (NERD), through activation of nuclear factor-kappaB (NF-kappaB), which is a pivotal transcription factor. Mucosal IL-8 concentrations have been found to parallel the endoscopic severity of RE, implying that this cytokine is a key player in the development of GERD. The mucosal levels of the C-C chemokines, macrophage chemoattractant protein 1 (MCP-1) and regulated on activation normal T-cell-expressed and presumably secreted (RANTES), which primarily attract monocytes and lymphocytes to the site of inflammation, respectively, are also elevated in RE. The secreted levels of IL-8 and IL-1beta, a prototype of proinflammatory cytokine, are maximal at the proximal segment within Barrett esophagus (BE) tissue. The expression of the two pleiotrophic proinflammatory cytokines, IL-6 and tumor necrosis factor alpha, is enhanced in the intestinal epithelium of BE, which places this epithelium at a higher risk for developing malignancy. BE is characterized by a distinct Th-2 predominant cytokine profile (IL-4 and -10), compared to the proinflammatory nature of RE (interferone-gamma). Treatment with a proton pump inhibitor, lansoprazole reduces the mucosal levels of IL-8 mRNA and protein in GERD, including RE and NERD. This may occur in part through an anti-inflammatory action of proton pump inhibitors beyond gastric acid inhibition.

Lipopolysaccharide binding protein is a potential marker for invasive bacterial infections in children

BACKGROUND

The aim of this study was to test the hypothesis that elevated lipopolysaccharide binding protein (LBP) serum concentration is a useful marker in the early diagnosis of invasive bacterial infection in children. We measured LBP in serum and cerebrospinal fluid (CSF) of children with proven invasive infection caused by Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis.

PATIENTS AND METHODS

Samples were collected from 39 children (aged 2 months to 17 years) with bacterial sepsis (n = 19) or meningitis (n = 20). Bacterial infection was diagnosed when a blood or CSF culture was positive and clinical signs of invasive infection were present. The control group consisted of serum (n = 60) and CSF (n = 19) samples from children with neurologic disease, juvenile idiopathic arthritis or viral infection. In 10 patients with bacterial infection, follow-up samples (24 and 48 hours) were available. LBP values were measured by an immunochemiluminescence analyzer (IMMULITE; DPC Biermann, Bad Nauheim, Germany) and compared with tumor necrosis factor-alpha and interleukin-8 concentrations.

RESULTS

The median LBP serum concentrations in patients with bacterial infection were markedly elevated compared with the control groups (45.0 [33.1-55.2] versus 8.3 [6.8-10.1] microg/mL [median and 5-95% confidence interval]; P < 0.0001). Follow-up serum values of LBP were persistently elevated despite adequate antibiotic treatment, whereas tumor necrosis factor-alpha and interleukin-8 concentrations decreased. In contrast, LBP concentrations in the CSF were below the detection limit of 0.5 microg/mL in 67% of patients with bacterial meningitis (median <0.5 microg/mL), whereas tumor necrosis factor-alpha and interleukin-8 levels were highly elevated.

CONCLUSION

LBP serum concentration is elevated in serum of children with invasive bacterial infection and could be a promising diagnostic marker.

Oxidative stress in pneumococcal meningitis: A future target for adjunctive therapy?

Despite antibiotic therapy and supportive intensive care, the morbidity and mortality of pneumococcal meningitis remain unacceptably high. During the last years, reactive oxygen (ROS) and nitrogen species (RNS), and peroxynitrite, were found to be produced in large amounts during pneumococcal meningitis. Although most likely intended to fight the invasive pathogens, they seem to lead to substantial collateral damage instead. This is because ROS and RNS can exert a vast variety of toxic actions, e.g., through lipid peroxidation, DNA strand breakage followed by PARP activation and subsequent cellular energy depletion, production of inflammatory cytokines, and activation of matrix metalloproteinases. Animal models of pneumococcal meningitis have shown that these interactions contribute to massive meningeal inflammation, disruption of the blood-brain barrier, alterations of the cerebral autoregulation, neuronal cell death, and cochlear destruction. Thus, the production of ROS and RNS seems at least in part to be responsible for the poor outcome of patients with pneumococcal meningitis. In consequence, reactive oxygen and nitrogen species such as peroxynitrite have been investigated as potential targets for adjunctive therapy in pneumococcal meningitis. Among the multiple agents tested, one promising drug is N-acetyl-l-cysteine (NAC), which significantly reduced cerebral and cochlear complications in animal models of experimental pneumococcal meningitis.

Influence of the blood bacterial load on the meningeal inflammatory response in Streptococcus pneumoniae meningitis

Background

Despite bacteraemia is present in the majority of patients with pneumococcal, little is known about the influence of the systemic infection on the meningeal inflammatory response.

Methods

To explore the role of systemic infection on the meningeal inflammation, experimental meningitis was induced by intracisternal injection of ~1 × 10⁶ CFU Streptococcus pneumoniae, type 3, and the 26 rabbits were either provided with ~1 × 10⁶ CFU S. pneumoniae intravenously at 0 hour ("bacteraemic" rabbits, n = 9), immunized with paraformaldehyde-killed S. pneumoniae for 5 weeks prior to the experiment ("immunized" rabbits", n = 8), or not treated further ("control" rabbits, n = 9). WBC and bacterial concentrations were determined in CSF and blood every second hour during a 16 hours study period together with CSF IL-8 and protein levels. We also studied CSF and blood WBC levels in 153 pneumococcal meningitis patients with and without presence of bacteraemia.

Results

As designed, blood bacterial concentrations were significantly different among three experimental groups during the 16 hours study period (Kruskal Wallis test, P < 0.05), whereas no differences in CSF bacterial levels were observed (P > 0.05). Blood WBC decreased in bacteraemic rabbits between ~10–16 hours after the bacterial inoculation in contrast to an increase for both the immunized rabbits and controls (P < 0.05). The CSF pleocytosis was attenuated in bacteraemic rabbits as compared to the two other groups between 12–16 hours from time of infection (P < 0.017), despite accelerated CSF IL-8 levels in bacteraemic rabbits.

In patients with pneumococcal meningitis, no significant difference in CSF WBC was observed between patients with or without bacteraemia at admission (n = 103, 1740 cells/μL (123–4032) vs. n = 50, 1961 cells/μL (673–5182), respectively, P = 0.18), but there was a significant correlation between CSF and blood WBC (n = 127, Spearman rho = 0.234, P = 0.008).

Conclusion

Our results suggest that a decrease in peripheral WBC induced by enhanced bacteraemia in pneumococcal meningitis results in an attenuated CSF pleocytosis.

Expression of CXC receptor 1 and 2 in esophageal mucosa of patients with reflux esophagitis

AIM: Interleukin 8 (IL-8) mediates neutrophil trafficking via its receptors. Recent studies have shown that IL-8 is likely involved in the development and progression of erosive reflux esophagitis (RE), yet little is known about the two distinct receptors, CXC receptor (CXCR)-1 and -2. The purpose of this study was to determine CXCR-1 and -2 messenger RNA expression levels in RE.

METHODS: We studied 26 patients with RE and 15 asymptomatic controls. Paired biopsy samples were taken from the esophagus 3 cm above the gastroesophageal junction; one biopsy was snap frozen for measurement of CXCR-1 and -2 mRNA levels by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), and another was formalin-fixed for histopathological evaluation. We also examined the association of the expression levels of CXCR-1 and -2 mRNA with histopathological hallmarks of RE.

RESULTS: The relative CXCR-1 and -2 mRNA expression levels were rather decreased in esophageal mucosa of patients with RE, compared to those in normal esophagus of controls. There were no significant difference in the relative mRNA expression levels of CXCR-1 and -2 among endoscopic grades of RE based on the Los Angeles classification. Each histopathological hallmark of GERD was not associated with the expression levels of CXCR-1 and -2 mRNA.

CONCLUSION: Apart from overexpression of IL-8, the relative expression levels of CXCR-1 and -2 mRNA were rather lower than expected in the affected esophageal mucosa of patients with RE.

[Chemokine--possible new options for the treatment of multiple sclerosis]

Accumulation and activation of mononuclear cells (lymphocytes and monocytes) in the CNS is one of the crucial steps in the pathogenesis of multiple sclerosis (MS). Chemokines and their receptors govern physiological and pathological leukocyte trafficking and may also be pertinent in hematogenous leukocyte infiltration of the CNS. Due to broad pharmacological interest in the chemokine system, peptide antagonists and small molecular antagonists are now available for clinical therapeutic trials. For the treatment of MS in particular, the chemokine receptors CCR1, CCR2, CCR5, and CXCR3 are possible targets in a chemokine-based therapeutic approach. In this review, we summarize current knowledge of the roles of chemokines and chemokine receptors in the pathogenesis of MS. Furthermore, options for possible therapeutic intervention through the chemokine system are outlined. Clinical studies in MS patients applying this knowledge are expected soon.

Interferon-beta prevents cytokine-induced neutrophil infiltration and attenuates blood-brain barrier disruption

Inflammation can contribute to brain injury, such as that resulting from ischemia or trauma. The authors have previously shown that the cytokine interferon-beta (IFN-beta) affords protection against ischemic brain injury, which was associated with a diminished infiltration of neutrophils and a reduction in blood-brain barrier (BBB) disruption. The goal of the current study was to directly assess the effects of IFN-beta on neutrophil infiltration, with the use of an in vivo assay of neutrophil infiltration with relevance to ischemic brain injury. Intrastriatal injection of recombinant rat cytokine-induced neutrophil chemoattractant-1, a member of the interleukin-8 family (1 microg in 1 microl), triggered massive infiltration of neutrophils and extensive BBB disruption 6 hours later, as measured using immunofluorescence microscopy and magnetic resonance imaging in the rat, respectively. Depleting the animals of neutrophils before interleukin-8 injection prevented BBB disruption. Treatment with IFN-beta (5 x 106 U/kg) almost completely prevented neutrophil infiltration and attenuated BBB damage. Gelatinase zymography showed matrix metalloproteinase-9 expression in the ipsilateral striatum after interleukin-8 injection. Both neutrophil depletion and IFN-beta treatment downregulated matrix metalloproteinase-9. IFN-beta has already been approved for human use as a treatment for the chronic inflammatory disorder multiple sclerosis. The potential value of IFN-beta as a treatment that can attenuate acute brain inflammation is considered.

Reprogramming the host response in bacterial meningitis: how best to improve outcome?

Despite effective antibiotic therapy, bacterial meningitis is still associated with high morbidity and mortality in both children and adults. Animal studies have shown that the host inflammatory response induced by bacterial products in the subarachnoid space is associated with central nervous system injury. Thus, attenuation of inflammation early in the disease process might improve the outcome. The feasibility of such an approach is demonstrated by the reduction in neurologic sequelae achieved with adjuvant dexamethasone therapy. Increased understanding of the pathways of inflammation and neuronal damage has suggested rational new targets to modulate the host response in bacterial meningitis, but prediction of which agents would be optimal has been difficult. This review compares the future promise of benefit from the use of diverse adjuvant agents. It appears unlikely that inhibition of a single proinflammatory mediator will prove useful in clinical practice, but several avenues to reprogram a wider array of mediators simultaneously are encouraging. Particularly promising are efforts to adjust combinations of cytokines, to inhibit neuronal apoptosis and to enhance brain repair.

Absolute neutrophil count in aseptic and bacterial meningitis related to time of lumbar puncture

Previous studies have demonstrated that during the first 24 hours of illness caused by aseptic meningitis, polymorphonuclear cells predominate in cerebrospinal fluid and decline afterward. To test the hypothesis that the absolute neutrophil count and percentage of polymorphonuclear cells in cerebrospinal fluid of bacterial meningitis patients are elevated and sustained after 24 hours compared with that of patients with aseptic meningitis. Seventy-two patients with aseptic meningitis and 13 with bacterial meningitis participated. All patients with aseptic meningitis and four patients with bacterial meningitis were followed-up prospectively. The patients were enrolled in four groups according to the interval between onset of symptoms and performance of the lumbar puncture (<12 hours, 12-24 hours, 24-36 hours, and >36 hours). In aseptic meningitis the mean absolute neutrophil count was 182, 164, 79, and 68 cells/mm(3), respectively (P = 0.025). In bacterial meningitis the absolute neutrophil count was 28, 1,466, 5,853, and 235 cells/mm(3), respectively. The mean percentage of polymorphonuclear cells in aseptic meningitis was 49%, 46%, 40%, and 26%, respectively (P = 0.038); in bacterial meningitis, 70%, 83%, 81%, and 58%, respectively. The findings suggest that the absolute neutrophil count and the polymorphonuclear cell percentage in cerebrospinal fluid have different kinetics in aseptic vs. bacterial meningitis.

Role and regulation of CXC-chemokines in acute experimental keratitis

The aim of this study was to elucidate the expression of chemokines, their role and regulation in bacterial corneal infection using three bacterial strains (Pseudomonas. aeruginosa- invasive, cytotoxic and contact lens induced acute red eye strains) which have been shown to produce three distinct patterns of corneal disease in the mouse. The predominant chemokine expressed in response to all three strains was MIP-2. Prolonged expression of high levels of MIP-2 was associated with increased severity of corneal inflammation. Significantly reduced disease severity upon administration of anti-MIP-2 antibodies suggested that MIP-2 may play an important role in the pathogenesis of Pseudomonas keratitis at least in part by being a major chemoattractant for polymorphonuclear leukocytes (PMN) recruitment. Interestingly, the numbers of bacteria in eyes with neutralized MIP-2 activity did not decrease even though the severity of the disease was decreased. This implies PMNs as the major destructive factor in microbial keratitis. Further, neutralization of IL-1beta activity alone using monoclonal antibodies resulted in significant reduction of both MIP-2 and KC activity indicating that chemokine levels were regulated by IL-1beta. These studies demonstrate that the regulation of MIP-2 activity may be beneficial in reducing corneal damage during microbial keratitis in rodents and perhaps that regulation of the human homologue of MIP-2, IL-8, may be useful for controlling keratitis in humans.

Expression of matrix metalloproteinases, sICAM-1 and IL-8 in CSF from children with meningitis

The combined expression of the inflammatory mediators, matrix metalloproteinases (MMPs), soluble form of intracellular adhesion molecule ICAM-1 (sICAM-1) and interleukin (IL)-8, was evaluated in children infected with bacterial or viral meningitis. MMP-2 and IL-8 were detected in all CSF samples and were enhanced in both bacterial and viral infected samples, compared to those from control children. The expression of MMP-9 as well as sICAM-1 was not detected in control CSF while observed in viral infected and further elevated in bacterial infected samples. This pilot study supports a role for MMPs, IL-8 and sICAM in infectious meningitis and suggests further research to determine their possible use as biomarkers for various forms of meningeal infection as well as the use of their specific antagonists as potential therapeutic agents for central nervous system (CNS) inflammatory processes.

A monoclonal antibody and an enzyme immunoassay for human Ala-IL-8(77)

Interleukin-8 (IL-8) plays a central role in neutrophil chemotaxis and exerts a wide range of effects on various cells, ranging from tumor angiogenesis to impairment of neuronal signaling. Two main forms of IL-8 exist, one containing 77 amino acids (Ala-IL-8(77)) and a second containing 72 amino acids (Ser-IL-8(72)), which comprise more than 90% of IL-8 protein in cell cultures. IL-8(77) was reported to be produced predominantly by endothelial cells and is known as "endothelial" IL-8. IL-8(72) predominates in monocyte cultures and is known as "leukocyte" IL-8. While both forms have equal chemotactic activity in vivo, recent data suggest that their biological activities might be different. Here we describe the generation of a mouse monoclonal antibody (mAb) specific for IL-8(77) and the development of a corresponding immunoassay. Various immunization protocols were investigated. Immunization with conjugates of a peptide from the N-terminus of IL-8(77) (NTP(77)) resulted in the production of an IgG1 mAb (N11) that recognizes human IL-8(77) and neutralizes its chemotactic activity. A sensitive ELISA specific for IL-8(77) was developed using N11 for capture and a biotinylated mAb to IL-8(72) for detection. Using this immunoassay it was shown that the only form of IL-8 secreted in cell culture was IL-8(77) and that the IL-8(72) present was the result of proteolysis of IL-8(77). IL-8(77) was detected in plasma and cerebrospinal fluid (CSF) from patients with sepsis and meningitis.

Phagocytosing neutrophils down-regulate the expression of chemokine receptors CXCR1 and CXCR2

CXC chemokines play a central role in regulation of neutrophil activation and chemotaxis. Because the chemotactic responses of neutrophils are impaired after phagocytosis, we explored the effect of phagocytic stimuli on the expression of interleukin-8 (IL-8) receptors, CXCR1 and CXCR2, in human neutrophils. After phagocytosis of opsonized yeast, the expression of CXCR1 and CXCR2 was substantially down-regulated and was accompanied by reduced Ca(++) responses to corresponding ligands, IL-8 and neutrophil-activating peptide-2 (NAP-2). The levels of CXCR1 and CXCR2 mRNA were constant during phagocytic stimulation of neutrophils. Confocal microscopy revealed that CXCR reduction was not via internalization. Metalloproteinase inhibitor, 1,10-phenantroline, prevented the reduction of CXCRs induced by phagocytosis, indicating that proteolytic degradation may be responsible for down-regulation. These observations suggest that down-regulation of CXCR expression may substantially reduce the responsiveness of phagocytosing neutrophils to CXC chemokines.

The bacterial peptide N-formyl-Met-Leu-Phe inhibits killing of Staphylococcus epidermidis by human neutrophils in fibrin gels

To study human neutrophil (polymorphonuclear leukocyte (PMN)) migration and killing of bacteria in an environment similar to that found in inflamed tissues in vivo, we have used fibrin gels. Fibrin gels (1500 microm thick) containing Staphylococcus epidermidis were formed in Boyden-type chemotaxis chambers. PMN migrated < 300 microm into these gels in 6 h and did not kill S. epidermidis when the gels contained heat-inactivated serum, C5-deficient serum, a streptococcal peptidase specific for a fragment of cleaved C5 (C5a), or anti-C5aR IgG. In contrast, in gels containing normal human serum, PMN migrated approximately 1000 microm into the gels in 4 h and into the full thickness of the gels in 6 h, and killed 90% of S. epidermidis in 6 h. fMLP reduced PMN migration into fibrin gels and allowed S. epidermidis to increase by approximately 300% in 4 h, whereas leukotriene B(4) stimulated PMN to migrate the full thickness of the gels and to kill 80% of S. epidermidis in 4 h. We conclude that both complement opsonization and C5a-stimulated chemotaxis are required for PMN bacterial killing in fibrin gels, and that fMLP inhibits PMN bactericidal activity in fibrin gels. The latter finding is surprising and suggests that in the presence of fibrin fMLP promotes bacterial virulence.