CXCL11 is involved in leucocyte recruitment to the central nervous system in neuroborreliosis

Obesity-induced neuroinflammation and cognitive impairment in young adult versus middle-aged mice

BACKGROUND

Obesity rates are increasing worldwide. Obesity leads to many complications, including predisposing individuals to the development of cognitive impairment as they age. Immune dysregulation, including inflammaging (e.g., increased circulating cytokines) and immunosenescence (declining immune system function), commonly occur in obesity and aging and may impact cognitive impairment. As such, immune system changes across the lifespan may impact the effects of obesity on neuroinflammation and associated cognitive impairment. However, the role of age in obesity-induced neuroinflammation and cognitive impairment is unclear. To further define this putative relationship, the current study examined metabolic and inflammatory profiles, along with cognitive changes using a high-fat diet (HFD) mouse model of obesity.

RESULTS

First, HFD promoted age-related changes in hippocampal gene expression. Given this early HFD-induced aging phenotype, we fed HFD to young adult and middle-aged mice to determine the effect of age on inflammatory responses, metabolic profile, and cognitive function. As anticipated, HFD caused a dysmetabolic phenotype in both age groups. However, older age exacerbated HFD cognitive and neuroinflammatory changes, with a bi-directional regulation of hippocampal inflammatory gene expression.

CONCLUSIONS

Collectively, these data indicate that HFD promotes an early aging phenotype in the brain, which is suggestive of inflammaging and immunosenescence. Furthermore, age significantly compounded the impact of HFD on cognitive outcomes and on the regulation of neuroinflammatory programs in the brain.

Modular network mechanism of CCN1-associated resistance to HSV-1-derived oncolytic immunovirotherapies for glioblastomas

Glioblastomas (GBMs) are the most common and lethal primary brain malignancy in adults. Oncolytic virus (OV) immunotherapies selectively kill GBM cells in a manner that elicits antitumor immunity. Cellular communication network factor 1 (CCN1), a protein found in most GBM microenvironments, expression predicts resistance to OVs, particularly herpes simplex virus type 1 (HSV-1). This study aims to understand how extracellular CCN1 alters the GBM intracellular state to confer OV resistance. Protein-protein interaction network information flow analyses of LN229 human GBM transcriptomes identified 39 novel nodes and 12 binary edges dominating flow in CCN1high cells versus controls. Virus response programs, notably against HSV-1, and cytokine-mediated signaling pathways are highly enriched. Our results suggest that CCN1high states exploit IDH1 and TP53, and increase dependency on RPL6, HUWE1, and COPS5. To validate, we reproduce our findings in 65 other GBM cell line (CCLE) and 174 clinical GBM patient sample (TCGA) datasets. We conclude through our generalized network modeling and system level analysis that CCN1 signals via several innate immune pathways in GBM to inhibit HSV-1 OVs before transduction. Interventions disrupting this network may overcome immunovirotherapy resistance.

Novel insights into neuroinflammation: bacterial lipopolysaccharide, tumor necrosis factor α, and Ureaplasma species differentially modulate atypical chemokine receptor 3 responses in human brain microvascular endothelial cells

BACKGROUND

Atypical chemokine receptor 3 (ACKR3, synonym CXCR7) is increasingly considered relevant in neuroinflammatory conditions, in which its upregulation contributes to compromised endothelial barrier function and may ultimately allow inflammatory brain injury. While an impact of ACKR3 has been recognized in several neurological autoimmune diseases, neuroinflammation may also result from infectious agents, including Ureaplasma species (spp.). Although commonly regarded as commensals of the adult urogenital tract, Ureaplasma spp. may cause invasive infections in immunocompromised adults as well as in neonates and appear to be relevant pathogens in neonatal meningitis. Nonetheless, clinical and in vitro data on Ureaplasma-induced inflammation are scarce.

METHODS

We established a cell culture model of Ureaplasma meningitis, aiming to analyze ACKR3 variances as a possible pathomechanism in Ureaplasma-associated neuroinflammation. Non-immortalized human brain microvascular endothelial cells (HBMEC) were exposed to bacterial lipopolysaccharide (LPS) or tumor necrosis factor-α (TNF-α), and native as well as LPS-primed HBMEC were cultured with Ureaplasma urealyticum serovar 8 (Uu8) and U. parvum serovar 3 (Up3). ACKR3 responses were assessed via qRT-PCR, RNA sequencing, flow cytometry, and immunocytochemistry.

RESULTS

LPS, TNF-α, and Ureaplasma spp. influenced ACKR3 expression in HBMEC. LPS and TNF-α significantly induced ACKR3 mRNA expression (p < 0.001, vs. control), whereas Ureaplasma spp. enhanced ACKR3 protein expression in HBMEC (p < 0.01, vs. broth control). Co-stimulation with LPS and either Ureaplasma isolate intensified ACKR3 responses (p < 0.05, vs. LPS). Furthermore, stimulation wielded a differential influence on the receptor's ligands.

CONCLUSIONS

We introduce an in vitro model of Ureaplasma meningitis. We are able to demonstrate a pro-inflammatory capacity of Ureaplasma spp. in native and, even more so, in LPS-primed HBMEC, underlining their clinical relevance particularly in a setting of co-infection. Furthermore, our data may indicate a novel role for ACKR3, with an impact not limited to auto-inflammatory diseases, but extending to infection-related neuroinflammation as well. AKCR3-induced blood-brain barrier breakdown might constitute a potential common pathomechanism.

Plasma and cerebrospinal fluid levels of cytokines as disease markers of neurologic manifestation in long-term HTLV-1 infected individuals

AIM

The aim of this study is to evaluate the presence of a particular immunological profile in individuals long-term infected with HTLV-1, followed presenting different clinical courses.

MATERIALS & METHODS

Forty-eight individuals were evaluated for 19 cytokines analyzed in cerebrospinal fluid and plasma of patients with HTLV-1 presenting with and without neurological symptoms.

RESULTS

Proinflammatory cytokines and the chemokine ligand 11 (ITAC/CXCL11) were increased in individuals with HTLV-1 coursing with neurological symptoms.

CONCLUSION

Different cytokines' expression profile in the presence of neurological symptoms may help to understand and characterize the progression for severe clinical presentations.

CXCL9 concentrations in cerebrospinal fluid and serum of patients with tick-borne encephalitis

INTRODUCTION

The aim of our current study was to evaluate cerebrospinal fluid (CSF) and serum CXCL9 concentrations and diagnostic usefulness of this molecule in tick-borne encephalitis (TBE). The study included TBE patients in the acute phase (TBE I) and after 2 weeks of follow-up (TBE II). The control group consisted of patients investigated for suspected central nervous system (CNS) infection, but with normal CSF findings.

MATERIAL AND METHODS

Concentrations of CXCL9 were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Cerebrospinal fluid and serum concentrations of CXCL9 in patients with TBE were significantly higher than in controls (p < 0.001). This alteration was also observed in the case of the CXCL9 index (I_CXCL9; CSF CXCL9 concentration divided by serum CXCL9 concentration) (p < 0.001); moreover, I_CXCL9 significantly decreased after 2 weeks (p < 0.001). This is the first study to evaluate the CSF and serum levels of CXCL9 in subjects with TBE.

CONCLUSIONS

CXCL9 is a ligand for CXCR3, which was found on all Th1 memory lymphocytes present in the peripheral blood; therefore the elevated concentrations of CXCL9 in TBE patients as compared to the controls might indicate that this chemokine perhaps takes part in the trafficking of Th₁ cells into the CNS. The results presented here support the hypothesis that CXCL9 may play a role in TBE. However, further studies are required to determine whether this protein might be used as a potential tool for the diagnosis and monitoring of inflammation in TBE.

Chemokines CXCL10, CXCL11, and CXCL13 in acute disseminated encephalomyelitis, non-polio enterovirus aseptic meningitis, and neuroborreliosis: CXCL10 as initial discriminator in diagnostic algorithm?

We investigated potential diagnostic usefulness of serum and cerebrospinal fluid (CSF) concentrations of chemokines CXCL10, CXCL11, and CXCL13 in pediatric patients with acute disseminated encephalomyelitis (ADEM) (n = 23), non-polio enterovirus aseptic meningitis (NPEV AM) (n = 20), and neuroborreliosis (NB) (n = 21) and children with acute infectious diseases with neurological symptoms but with excluded neuroinfection/neuroinflammation (controls, n = 20). CSF levels of CXCL10 and CXCL11 were higher in patients with NPEV AM than those in other children, and CXCL10 levels showed a high discriminative potential (area under the receiver operating characteristic curve, ROC, 0.982) with high specificity and sensitivity (both 95%). CSF levels of CXCL13 were higher in NB patients than those in other children; however, discriminative potential (area under ROC curve 0.814) and diagnostic properties were moderate (sensitivity 67%, specificity 97%). Data suggest usefulness of chemokine quantification as a diagnostic aid in children with suspected ADEM, NPEV AM, or NB.

IFNγ Enhances CD64-Potentiated Phagocytosis of Treponema pallidum Opsonized with Human Syphilitic Serum by Human Macrophages

Syphilis is a multi-stage, sexually transmitted disease caused by the spirochete Treponema pallidum (Tp). Considered broadly, syphilis can be conceptualized as a dualistic process in which spirochete-driven inflammation, the cause of clinical manifestations, coexists to varying extents with bacterial persistence. Inflammation is elicited in the tissues, along with the persistence of spirochetes to keep driving a robust immune response while evading host defenses; this duality is best exemplified during the florid, disseminated stage called secondary syphilis (SS). SS lesions typically contain copious amounts of spirochetes along with a mixed cellular infiltrate consisting of CD4⁺ T cells, CD8⁺ T cells, NK cells, plasma cells, and macrophages. In the rabbit model, Tp are cleared by macrophages via antibody-mediated opsonophagocytosis. Previously, we demonstrated that human syphilitic serum (HSS) promotes efficient uptake of Tp by human monocytes and that opsonophagocytosis of Tp markedly enhances cytokine production. Herein, we used monocyte-derived macrophages to study Tp–macrophage interactions ex vivo. In the absence of HSS, monocyte-derived macrophages internalized low numbers of Tp and secreted little cytokine (e.g., TNF). By contrast, these same macrophages internalized large numbers of unopsonized Borrelia burgdorferi and secreted robust levels of cytokines. Maturation of macrophages with M-CSF and IFNγ resulted in a macrophage phenotype with increased expression of HLA-DR, CD14, inducible nitric oxide synthase, TLR2, TLR8, and the Fcγ receptors (FcγR) CD64 and CD16, even in the absence of LPS. Importantly, IFNγ-polarized macrophages resulted in a statistically significant increase in opsonophagocytosis of Tp accompanied by enhanced production of cytokines, macrophage activation markers (CD40, CD80), TLRs (TLR2, TLR7, TLR8), chemokines (CCL19, CXCL10, CXCL11), and T_H1-promoting cytokines (IL-12, IL-15). Finally, the blockade of FcγRs, primarily CD64, significantly diminished spirochetal uptake and proinflammatory cytokine secretion by IFNγ-stimulated macrophages. Our ex vivo studies demonstrate the importance of CD64-potentiated uptake of opsonized Tp and suggest that IFNγ-activated macrophages have an important role in the context of early syphilis. Our study results also provide an ex vivo surrogate system for use in future syphilis vaccine studies.

CXCL11 production in cerebrospinal fluid distinguishes herpes simplex meningitis from herpes simplex encephalitis

Background

The closely related herpes simplex viruses 1 and 2 can cause inflammations of the central nervous system (CNS), where type 1 most often manifest as encephalitis (HSE), and type 2 as meningitis (HSM). HSE is associated with severe neurological complications, while HSM is benign in adults. We proposed that studying the chemokine and cytokine production in cerebrospinal fluid (CSF) and serum could indicate why two closely related viruses exhibit different severity of their accompanied CNS inflammation.

Methods

Secretion patterns of 30 chemokines and 10 cytokines in CSF of adult patients with acute HSE (n = 14) and HSM (n = 20) in the initial stage of disease were analyzed and compared to control subjects without viral central nervous system infections and to levels in serum.

Results

Most measured chemokines and cytokines increased in CSF of HSE and HSM patients. Overall, the CSF chemokine levels were higher in CSF of HSM patients compared to HSE patients. However, only five chemokines reached levels in the CSF that exceeded those in serum facilitating a positive CSF-serum chemokine gradient. Of these, CXCL8, CXCL9, and CXCL10 were present at high levels both in HSE and HSM whereas CXCL11 and CCL8 were present in HSM alone. Several chemokines were also elevated in serum of HSE patients but only one in HSM patients. No chemokine in- or efflux between CSF and serum was indicated as the levels of chemokines in CSF and serum did not correlate.

Conclusions

We show that HSM is associated with a stronger and more diverse inflammatory response in the CNS compared to HSE in the initial stage of disease. The chemokine patterns were distinguished by the exclusive local CNS production of CXCL11 and CCL8 in HSM. Inflammation in HSM appears to be restricted to the CNS whereas HSE also was associated with systemic inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0907-5) contains supplementary material, which is available to authorized users.

CXCR3 modulates glial accumulation and activation in cuprizone-induced demyelination of the central nervous system

Background

The functional state of glial cells, like astrocytes and microglia, critically modulates the course of neuroinflammatory and neurodegenerative diseases and can have both detrimental and beneficial effects. Glial cell function is tightly controlled by cellular interactions in which cytokines are important messengers. Recent studies provide evidence that in particular chemokines are important modulators of glial cell function. During the course of CNS diseases like multiple sclerosis or Alzheimer’s disease, and in the corresponding animal models, the chemokines CXCL9 and CXCL10 are abundantly expressed at sites of glial activation, arguing for an important role of these chemokines and their corresponding receptor CXCR3 in glial activation. To clarify the role of this chemokine system in glial cell activation, we characterized the impact of CXCR3 on glial activation in a model of toxic demyelination in which glial activation without a prominent influx of hematogenous cells is prototypical.

Methods

We investigated the impact of CXCR3 on cuprizone-induced demyelination, comparing CXCR3-deficient mice with wild type controls. The clinical course during cuprizone feeding was documented for five weeks and for the subsequent four days withdrawal of the cuprizone diet (5.5 weeks). Glial activation was characterized using histological, histomorphometric and phenotypic analysis. Molecular analysis for (de)myelination and neuroinflammation was applied to characterize the effect of cuprizone on CXCR3-deficient mice and control animals.

Results

CXCR3-deficient mice displayed a milder clinical course during cuprizone feeding and a more rapid body weight recovery after offset of diet. In the CNS, CXCR3 deficiency significantly attenuated the accumulation and activation of microglia and astrocytes. Moreover, a deficiency of CXCR3 reduced the expression of the microglial activation markers CD45 and CD11b. Compared to controls, we observed a vast reduction of RNA levels for proinflammatory cytokines and chemokines like Ccl2, Cxcl10, Tnf and Il6 within the CNS of cuprizone-treated mice. Lastly, CXCR3 deficiency had no major effects on the course of demyelination during cuprizone feeding.

Conclusions

The CXCR3 chemokine system is critically involved in the intrinsic glial activation during cuprizone-induced demyelination, which significantly modulates the distribution of glial cells and the local cytokine milieu.

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 proteome of patients with acute Lyme disease

During acute Lyme disease, bacteria can disseminate to the central nervous system (CNS), leading to the development of meningitis and other neurologic symptoms. Here we have analyzed pooled cerebrospinal fluid (CSF) allowing a deep view into the proteome for patients diagnosed with early disseminated Lyme disease and CSF inflammation. Additionally, we analyzed individual patient samples and quantified differences in protein abundance employing label-free quantitative mass spectrometry-based methods. We identified 108 proteins that differ significantly in abundance in patients with acute Lyme disease from controls. Comparison between infected patients and control subjects revealed differences in proteins in the CSF associated with cell death localized to brain synapses and others that likely originate from brain parenchyma.

Concentration gradient of CXCL10 and CXCL11 between the cerebrospinal fluid and plasma in children with enteroviral aseptic meningitis

BACKGROUND

Lymphocyte migration from the blood into the CNS is mediated by chemokines and chemokine receptors. Chemokines CXCL10 and CXCL11 are important for the recruitment of CXCR3-expressing Th1 lymphocytes to the site of inflammation.

AIMS

To determine the concentrations of CXCL10 and CXCL11 in the CSF and plasma of children with enteroviral aseptic meningitis (EV AM) and controls and the contribution of these chemokines to the chemokine concentration gradient between the periphery and the CNS.

METHODS

The study included 26 pediatric patients with EV AM and 16 controls in whom CNS infection is excluded by negative CSF examination. Chemokines were quantified by using enzyme immunoassay. Etiological diagnosis of EV AM was based on the detection of enteroviral RNA in the CSF using real-time PCR.

RESULTS

CXCL10 (median 12 725 pg/ml) and CXCL11 (median 187 pg/ml) concentrations in CSF of patients with meningitis were significantly higher compared to plasma (median 173 pg/ml and median 110 pg/ml; p < 0.001, p = 0.026 respectively). CXCL10 concentrations in the CSF (median 198 pg/ml) and plasma of controls (median 124 pg/ml) were not significantly different (p = 0.642). CXCL11 concentrations in the CSF of controls (median 89 pg/ml) were significantly lower compared with plasma (median 139 pg/ml, p = 0.004). Chemokine concentration gradient was not influenced by pleocytosis, nor dependent on cytologic CSF formula or the presence of proteinorrachia.

CONCLUSION

CXCL10 and CXCL11 concentration gradient between the CSF and plasma in children with EV AM suggests an important role of these chemokines in the T-cells recruitment into the CNS and local immunoreaction.

Opposing roles for CXCR3 signaling in central nervous system versus ocular inflammation mediated by the astrocyte-targeted production of IL-12

CXCR3 and its ligands are important for the trafficking of activated CD4(+) T(H)1 T cells, CD8(+) T cells, and natural killer cells during inflammation. Recent functional studies demonstrate a more diverse role of CXCR3 in inflammatory diseases of the central nervous system (CNS). We examined the impact of CXCR3 on a less complex interferon-γ-dependent, type 1 cell-mediated immune response in the CNS, induced in mice by the transgenic production of glial fibrillary acidic protein IL-12 (GF-IL12) by astrocytes and retinal Müller cells. GF-IL12 mice develop ataxia because of severe cerebellar inflammation but have little overt ocular disease. Surprisingly, CXCR3-deficient GF-IL12 mice (GF-IL12/CXCR3KO) have drastically reduced ataxia but developed cataracts, severe ocular inflammation, and eye atrophy. Most GF-IL12/CXCR3KO mice had minimal cerebellar inflammation but severe retinal disorganization, loss of photoreceptors, and lens destruction in the eye. The number of CD3(+), CD11b(+), and natural killer 1.1(+) cells were reduced in the CNS but highly increased in the eyes of GF-IL12/CXCR3KO compared with GF-IL12 mice. High levels of interferon-γ, IL-1, tumor necrosis factor α, CXCL9, CXCL10, and CCL5 were found in GF-IL12 cerebelli and GF-IL12/CXCR3KO eyes. Our findings demonstrate key but paradoxical functions for CXCR3 in IL-12-induced immune disease in the CNS, promoting inflammation in the brain yet restricting it in the eye. We conclude that the function of CXCR3 in cellular immune disease is driven by a common trigger and is controlled by tissue-specific factors.

Neuroborreliosis: pathogenesis, symptoms, diagnosis and treatment

Lyme disease is the most common human tick-borne disease in the northern hemisphere. This article describes the current knowledge of several aspects of Lyme neuroborreliosis. The epidemiology is reviewed first, with special respect to the difference between European and American disease. Then, the current knowledge about the pathogenesis of Lyme neuroborreliosis is presented, with emphasis on immune evasion strategies. Furthermore, the clinical picture of acute Lyme neuroborreliosis and the frequently discussed post-Lyme disease syndrome are critically discussed. The commonly used diagnostic strategies, as well as the relevance of the lymphocyte transformation test, CD57+/CD3- cell count and CXCL13, are presented. Finally, the therapeutic options are described to give a balanced overview of all aspects of this disease.

Neutralizing endogenous chemokines with small molecules. Principles and potential therapeutic applications

Regulation of cellular responses to external stimuli such as hormones, neurotransmitters, or cytokines is achieved through the control of all steps of the complex cascade starting with synthesis, going through maturation steps, release, distribution, degradation and/or uptake of the signalling molecule interacting with the target protein. One possible way of regulation, referred to as scavenging or neutralization of the ligand, has been increasingly studied, especially for small protein ligands. It shows innovative potential in chemical biology approaches as well as in disease treatment. Neutralization of protein ligands, as for example cytokines or chemokines can lead to the validation of signalling pathways under physiological or pathophysiological conditions, and in certain cases, to the development of therapeutic molecules now used in autoimmune diseases, chronic inflammation and cancer treatment. This review explores the field of ligand neutralization and tries to determine to what extent small chemical molecules could substitute for neutralizing antibodies in therapeutic approaches.

The chemokine CXCL13 is a key regulator of B cell recruitment to the cerebrospinal fluid in acute Lyme neuroborreliosis

Background

The chemokine CXCL13 is known to dictate homing and motility of B cells in lymphoid tissue and has been implicated in the formation of ectopic lymphoid tissue in chronic inflammation. Whether it influences B cell trafficking during acute infection, is largely unclear. In previous studies, we showed that (I) CXCL13 levels are markedly increased in the B cell-rich cerebrospinal fluid (CSF) of patients with acute Lyme neuroborreliosis (LNB), and (II) CXCL13 is released by monocytes upon recognition of borrelial outer surface proteins by Toll-like receptor 2. Here, we assessed the role of CXCL13 - in comparison to other chemokines - in the recruitment of B cells to the CSF of patients with acute LNB.

Methods

Measurement of chemokines was done by ELISA. B cells were isolated from whole blood using magnetic cell separation (MACS). For migration experiments, a modified Boyden chamber assay was used and the migrated B cells were further analysed by FACS. The migration was inhibited either by preincubation of the CSF samples with neutralizing antibodies, heating to 60°C, removal of proteins >3 kDa, or by pre-treatment of the B cells with pertussis toxin. The principal statistical tests used were one-way analysis of variance and Bonferroni test (chemokine measurements) as well as paired Student's t-test (migration experiments).

Results

Measurements of chemokine levels revealed an increase in three of the four known major B cell chemoattractants CXCL13, CCL19 and CXCL12 in LNB CSF. The CXCL13 CSF:serum ratio, as a measure of the chemotactic gradient, was substantially higher than that of CCL19 and CXCL12. Moreover, the chemotactic activity of LNB CSF was reduced up to 56% after preincubation with a neutralizing CXCL13 antibody, while combined preincubation with antibodies against CXCL13, CCL19, and CXCL12 did not lead to further reduction. Since treatment with pertussis toxin, heating to 60°C, and removal of proteins >3 kDa abrogated the chemotactic activity, further not yet identified chemokines seem to be involved in B cell recruitment to LNB CSF.

Conclusion

Combined, our study suggests a key role of CXCL13 in B cell migration to sites of infection as shown here for the CSF of LNB patients.

The pathogenesis of lyme neuroborreliosis: from infection to inflammation

This review describes the current knowledge of the pathogenesis of acute Lyme neuroborreliosis (LNB), from invasion to inflammation of the central nervous system. Borrelia burgdorferi (B.b.) enters the host through a tick bite on the skin and may disseminate from there to secondary organs, including the central nervous system. To achieve this, B.b. first has to evade the hostile immune system. In a second step, the borrelia have to reach the central nervous system and cross the blood-brain barrier. Once in the cerebrospinal fluid (CSF), the spirochetes elicit an inflammatory response. We describe current knowledge about the infiltration of leukocytes into the CSF in LNB. In the final section, we discuss the mechanisms by which the spirochetal infection leads to the observed neural dysfunction. To conclude, we construct a stringent concept of the pathogenesis of LNB.

High levels of inflammatory chemokines and cytokines in joint fluid and synovial tissue throughout the course of antibiotic-refractory lyme arthritis

OBJECTIVE

To investigate the possible role of chemokines and cytokines in the pathogenesis of Lyme arthritis.

METHODS

Using cytometric bead array and flow cytometry techniques, chemokine and cytokine levels were determined in 65 synovial fluid (SF) samples and 7 synovial tissue (ST) samples from 17 patients with antibiotic-responsive Lyme arthritis and 35 patients with antibiotic-refractory Lyme arthritis seen during the past 18 years. In the ST samples, expression of chemokine receptors was measured using immunohistochemistry.

RESULTS

Before or during antibiotic therapy, when the majority of patients had positive polymerase chain reaction (PCR) results for Borrelia burgdorferi DNA, SF from patients with antibiotic-refractory arthritis contained exceptionally high levels of Th1 chemoattractants and cytokines, particularly CXCL9 and interferon-gamma (IFNgamma). Compared with the patients whose arthritis was responsive to antibiotic treatment, those with antibiotic-refractory arthritis had significantly higher levels of CXCL9 and CXCL10 (both P<or=0.001) and CCL3, CCL4, CXCL8, IFNgamma, tumor necrosis factor alpha, interleukin-1beta (IL-1beta), and IL-6 (all P<or=0.01). During the post-antibiotic period, when the results of PCR for B burgdorferi DNA in SF and ST were uniformly negative, patients with antibiotic-refractory arthritis continued to exhibit high SF and ST levels of these chemokines and cytokines. In addition, synovial samples showed marked expression of the receptors for T cell or macrophage chemokines, CXCR3 and CCR5.

CONCLUSION

Patients with antibiotic-refractory Lyme arthritis have high synovial fluid levels of proinflammatory chemokines and cytokines, especially CXCL9 and IFNgamma, throughout the illness. Thus, even when antibiotic treatment reduces or completely clears the infection in these patients, the inflammatory response in synovium persists.

IFN-γ Alters the Response ofBorrelia burgdorferi-Activated Endothelium to Favor Chronic Inflammation

Borrelia burgdorferi, the agent of Lyme disease, promotes proinflammatory changes in the endothelium that lead to the recruitment of leukocytes. The host immune response to infection results in increased levels of IFN-gamma in the serum and lesions of Lyme disease patients that correlate with greater severity of disease. Therefore, the effect of IFN-gamma on the gene expression profile of primary human endothelial cells exposed to B. burgdorferi was determined. B. burgdorferi and IFN-gamma synergistically augmented the expression of 34 genes, 7 of which encode chemokines. Six of these (CCL7, CCL8, CX3CL1, CXCL9, CXCL10, and CXCL11) attract T lymphocytes, and one (CXCL2) is specific for neutrophils. Synergistic production of the attractants for T cells was confirmed at the protein level. IL-1beta, TNF-alpha, and LPS also cooperated with IFN-gamma to induce synergistic production of CXCL10 by the endothelium, indicating that IFN-gamma potentiates inflammation in concert with a variety of mediators. An in vitro model of the blood vessel wall revealed that an increased number of human T lymphocytes traversed the endothelium exposed to B. burgdorferi and IFN-gamma, as compared with unstimulated endothelial monolayers. In contrast, addition of IFN-gamma diminished the migration of neutrophils across the B. burgdorferi-activated endothelium. IFN-gamma thus alters gene expression by endothelia exposed to B. burgdorferi in a manner that promotes recruitment of T cells and suppresses that of neutrophils. This modulation may facilitate the development of chronic inflammatory lesions in Lyme disease.

Cerebrospinal fluid-infiltrating CD4+ T cells recognize Borrelia burgdorferi lysine-enriched protein domains and central nervous system autoantigens in early lyme encephalitis

Neurological manifestations of Lyme disease are usually accompanied by inflammatory changes in the cerebrospinal fluid (CSF) and the recruitment of activated T cells into the CSF compartment. In order to characterize the phenotype and identify target antigens of CSF-infiltrating T cells in early neuroborreliosis with central nervous system (CNS) involvement, we combined T-cell cloning, functional testing of T-cell responses with positional scanning synthetic combinatorial peptide libraries, and biometric data analysis. We demonstrate that CD4+ gamma interferon-producing T cells specifically responding to Borrelia burgdorferi lysate were present in the CSF of a patient with acute Lyme encephalitis. Some T-cell clones recognized previously uncharacterized B. burgdorferi epitopes which show a specific enrichment for lysine, such as the heat shock-induced chaperone HSP90. Degenerate T-cell recognition that included T-cell responses to borrelia-specific and CNS-specific autoantigens derived from the myelin protein 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) could be demonstrated for one representative clone. Our results show that spirochetal antigen-specific and Th1-polarized CD4+ lymphocytes infiltrate the CSF during monophasic CNS symptoms of Lyme disease and demonstrate that cross-recognition of CNS antigens by B. burgdorferi-specific T cells is not restricted to chronic and treatment-resistant manifestations.