CC Chemokine Family Members' Modulation as a Novel Approach for Treating Central Nervous System and Peripheral Nervous System Injury-A Review of Clinical and Experimental Findings

Despite significant progress in modern medicine and pharmacology, damage to the nervous system with various etiologies still poses a challenge to doctors and scientists. Injuries lead to neuroimmunological changes in the central nervous system (CNS), which may result in both secondary damage and the development of tactile and thermal hypersensitivity. In our review, based on the analysis of many experimental and clinical studies, we indicate that the mechanisms occurring both at the level of the brain after direct damage and at the level of the spinal cord after peripheral nerve damage have a common immunological basis. This suggests that there are opportunities for similar pharmacological therapeutic interventions in the damage of various etiologies. Experimental data indicate that after CNS/PNS damage, the levels of 16 among the 28 CC-family chemokines, i.e., CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11, CCL12, CCL17, CCL19, CCL20, CCL21, and CCL22, increase in the brain and/or spinal cord and have strong proinflammatory and/or pronociceptive effects. According to the available literature data, further investigation is still needed for understanding the role of the remaining chemokines, especially six of them which were found in humans but not in mice/rats, i.e., CCL13, CCL14, CCL15, CCL16, CCL18, and CCL23. Over the past several years, the results of studies in which available pharmacological tools were used indicated that blocking individual receptors, e.g., CCR1 (J113863 and BX513), CCR2 (RS504393, CCX872, INCB3344, and AZ889), CCR3 (SB328437), CCR4 (C021 and AZD-2098), and CCR5 (maraviroc, AZD-5672, and TAK-220), has beneficial effects after damage to both the CNS and PNS. Recently, experimental data have proved that blockades exerted by double antagonists CCR1/3 (UCB 35625) and CCR2/5 (cenicriviroc) have very good anti-inflammatory and antinociceptive effects. In addition, both single (J113863, RS504393, SB328437, C021, and maraviroc) and dual (cenicriviroc) chemokine receptor antagonists enhanced the analgesic effect of opioid drugs. This review will display the evidence that a multidirectional strategy based on the modulation of neuronal-glial-immune interactions can significantly improve the health of patients after CNS and PNS damage by changing the activity of chemokines belonging to the CC family. Moreover, in the case of pain, the combined administration of such antagonists with opioid drugs could reduce therapeutic doses and minimize the risk of complications.

A biodegradable nanoparticle platform for the induction of antigen-specific immune tolerance for treatment of autoimmune disease

Targeted immune tolerance is a coveted therapy for the treatment of a variety of autoimmune diseases, as current treatment options often involve nonspecific immunosuppression. Intravenous (iv) infusion of apoptotic syngeneic splenocytes linked with peptide or protein autoantigens using ethylene carbodiimide (ECDI) has been demonstrated to be an effective method for inducing peripheral, antigen-specific tolerance for treatment of autoimmune disease. Here, we show the ability of biodegradable poly(lactic-co-glycolic acid) (PLG) nanoparticles to function as a safe, cost-effective, and highly efficient alternative to cellular carriers for the induction of antigen-specific T cell tolerance. We describe the formulation of tolerogenic PLG particles and demonstrate that administration of myelin antigen-coupled particles both prevented and treated relapsing-remitting experimental autoimmune encephalomyelitis (R-EAE), a CD4 T cell-mediated mouse model of multiple sclerosis (MS). PLG particles made on-site with surfactant modifications surpass the efficacy of commercially available particles in their ability to couple peptide and to prevent disease induction. Most importantly, myelin antigen-coupled PLG nanoparticles are able to significantly ameliorate ongoing disease and subsequent relapses when administered at onset or at peak of acute disease, and minimize epitope spreading when administered during disease remission. Therapeutic treatment results in significantly reduced CNS infiltration of encephalitogenic Th1 (IFN-γ) and Th17 (IL-17a) cells as well as inflammatory monocytes/macrophages. Together, these data describe a platform for antigen display that is safe, low-cost, and highly effective at inducing antigen-specific T cell tolerance. The development of such a platform carries broad implications for the treatment of a variety of immune-mediated diseases.

Inflammatory macrophage migration in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a CD4 T cell-mediated demyelinating disease of the central nervous system (CNS) where macrophages are the end-stage effector cell. EAE serves as a model for multiple sclerosis where it has been instructive in delineating the autoimmune cellular response in the CNS for the purpose of developing more effective therapies. Understanding the nature of how cytokine and chemokine networks regulate the migration of leukocytes to the CNS requires the ability to track subpopulations of those cells in vivo. We describe a flow cytometric technique to monitor the migration of macrophages during EAE development.

The Inflammatory Response to Nonfatal Sindbis Virus Infection of the Nervous System Is More Severe in SJL Than in BALB/c Mice and Is Associated with Low Levels of IL-4 mRNA and High Levels of IL-10-Producing CD4+ T Cells

SJL mice are susceptible to inflammatory autoimmune diseases of the central nervous system (CNS), while BALB/c mice are relatively resistant. To understand differences in immune responses that may contribute to autoimmune neurologic disease, we compared the responses of SJL and BALB/c mice to infection with Sindbis virus, a virus that causes acute nonfatal encephalomyelitis in both strains of mice. Clearance of virus was similar, but SJL mice developed a more intense inflammatory response in the brain and spinal cord and inflammation persisted for several weeks. Analysis of lymphocytes isolated from brains early after infection showed an absence of NK cells in SJL mice, while both strains of mice showed CD4+ and CD8+ T cells. During the second week after infection, CD4+ T cells increased in SJL mice and the proportion of CD8+ T cells decreased, while the opposite pattern was seen in BALB/c mice. Expression of IL-10 mRNA was higher and IL-4 mRNA was lower in the brains of infected SJL than in BALB/c mice, while expression of the mRNAs of IL-6, IL-1β, TNFα, and the Th1 cytokines IL-2, IL-12, and IFN-γ was similar. Lymphocytes isolated from the CNS of SJL mice produced large amounts of IL-10. CNS lymphocytes from both strains of mice produced IFN-γ in response to stimulation with Sindbis virus, but not in response to myelin basic protein. These data suggest that IL-10-producing CD4+ T cells are differentially recruited to or regulated within the CNS of SJL mice compared with BALB/c mice infected with Sindbis virus, a characteristic that may be related to low levels of IL-4, and is likely to be involved in susceptibility of SJL mice to CNS inflammatory diseases.

Treatment with Anti-Granulocyte Antibodies Inhibits the Effector Phase of Experimental Autoimmune Encephalomyelitis

Emerging data suggest that polymorphonuclear leukocytes (PMNLs) can play an important role in Ag-dependent immune responses. Therefore, we have assessed the involvement of these cells in the development of an organ-specific autoimmune disease, experimental autoimmune encephalomyelitis (EAE), in the mouse. Depletion of peripheral blood PMNLs beginning day 8 after immunization significantly delayed and in some cases totally prevented the development of clinical EAE in mice. Depletion of PMNLs beginning 1 day before sensitization and continuing until day 7 postimmunization had no effect on the subsequent development of EAE, suggesting that depletion alters the efferent but not the afferent arm of the immune response. In vitro studies showed that lymphoid cells from mice protected from EAE by PMNL depletion beginning on day 8 postsensitization proliferated in response to specific Ag to a level equal to cells from sensitized animals treated with control serum, again indicating that treatment was not affecting the afferent limb of the immune response. Further evidence that PMNL may be necessary in initiating the pathology of EAE was seen in passive transfer experiments where PMNL-depleted recipients of MBP-specific lymphoid effector cells developed EAE much less effectively than did animals treated with control Ab. Taken together, these data indicate that PMNLs play a critical role in the effector phase of the development of the clinicopathologic expression of EAE in mice.

STCP-1 (MDC) CC Chemokine Acts Specifically on Chronically Activated Th2 Lymphocytes and Is Produced by Monocytes on Stimulation with Th2 Cytokines IL-4 and IL-13

STCP-1 stimulated T cell chemoattractant protein-1 (STCP-1) (macrophage-derived chemokine; MDC), a recently described CC chemokine for chronically activated T lymphocytes, was found to act specifically on a subset of memory CD4 lymphocytes that displayed a Th2 cytokine profile. Also, STCP-1, thymus and activation regulated chemokine (TARC), eotaxin, and eotaxin-2 acted specifically on in vitro derived Th2 lymphocytes, while IP-10 (IFN-γ-inducible 10-kDa protein) showed some preference for Th1 lymphocytes. The corresponding receptors for eotaxin, TARC, and IP-10 are also differentially expressed on Th1 and Th2 lymphocytes. In desensitization Ca flux experiments, TARC and STCP-1 bound to a common receptor and therefore at least one chemokine receptor for STCP-1 is CCR4. STCP-1 expression is restricted to immune cells. Dendritic cells, B cells, and macrophages produce STCP-1 constitutively, while NK cells, monocytes, and CD4 lymphocytes produce STCP-1 upon appropriate stimulation. Production of STCP-1 is positively modulated by Th2 cytokines IL-4 and IL-13 but inhibited by IL-10.

Differential Expression of Inflammatory Cytokines Parallels Progression of Central Nervous System Pathology in Two Clinically Distinct Models of Multiple Sclerosis

Multiple sclerosis is an immune-mediated demyelinating disease of unknown etiology that presents with either a chronic-progressive or relapsing-remitting clinical course. Theiler’s murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) and relapsing-remitting experimental autoimmune encephalomyelitis (R-EAE) in the SJL/J mouse are both relevant murine CD4+ T cell-mediated demyelinating models that recapitulate the multiple sclerosis disease phenotypes. To determine the cellular and molecular basis for these observed differences in clinical course, we quantitatively analyzed the temporal expression of pro- and antiinflammatory cytokine mRNA expression in the central nervous system (CNS) and the phenotype of the inflammatory mononuclear infiltrates. TMEV-infected SJL/J mice expressed IFN-γ, TNF-α, IL-10, and IL-4 mRNA during the preclinical phase, and their levels continued to increase throughout the duration of the chronic-progressive disease course. These data correlated with the continued presence of both CD4+ T cells and F4/80+ macrophages within the CNS infiltrates. In contrast, SJL/J mice with PLP139–151-induced R-EAE displayed a biphasic pattern of CNS expression for the proinflammatory cytokines, IFN-γ and TNF-α, with expression peaking at the height of the acute phase and relapse(s). This pattern correlated with dynamic changes in the CD4+ T cell and F4/80+ macrophage populations during relapsing-remitting disease progression. Interestingly, IL-4 message was undetectable until disease remission(s), demonstrating its potential role in the intrinsic regulation of ongoing disease, whereas IL-10 was continuously expressed, arguing against a regulatory role in either disease. These data suggest that the kinetics of cytokine expression together with the nature of the persistent inflammatory infiltrates are major contributors to the differences in clinical course between TMEV-IDD and R-EAE.

Long-Lasting Protective Immunity to Experimental Autoimmune Encephalomyelitis Following Vaccination with Naked DNA Encoding C-C Chemokines

DNA vaccination represents a novel means of expressing Ag in vivo for the generation of both humoral and cellular immune responses. The current study uses this technology to elicit protective immunity against experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease of the central nervous system that serves as an experimental model for multiple sclerosis. RT-PCR verified by Southern blotting and sequencing of PCR products of four different C-C chemokines, macrophage-inflammatory protein-1α (MIP-1α), monocyte-chemotactic protein-1 (MCP-1), MIP-1β, and RANTES, were performed on brain samples from EAE rats to evaluate mRNA transcription at different stages of disease. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1α or MCP-1 DNA vaccines prevented EAE, even if disease was induced 2 mo after administration of naked DNA vaccines. In contrast, administration of the MIP-1β naked DNA significantly aggravated the disease. Generation of in vivo immune response to RANTES naked DNA had no notable effect on EAE. MIP-1α, MCP-1, and MIP-1β mRNA transcription in EAE brains peaked at the onset of disease and declined during its remission, whereas RANTES transcription increased in EAE brains only following recovery. Immunization of CFA without the encephalitogenic epitope did not elicit the anti-C-C chemokine regulatory response in DNA-vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease.

Cutting Edge Commentary: Chemokine Regulation of Experimental Autoimmune Encephalomyelitis: Temporal and Spatial Expression Patterns Govern Disease Pathogenesis

Experimental autoimmune encephalomyelitis (EAE) is a CD4+ Th1-mediated demyelinating disease of the central nervous system that serves as a model for multiple sclerosis (MS). There are several considerations that suggest a role for chemokines in the disease process. First, chemokines are highly expressed in the central nervous system with a tight temporal relationship to disease activity. Second, in vivo neutralization studies showed a distinct role for specific chemokines in the evolution of the process. Third, the selective and differential expression of chemokines in differing models of EAE bears a close relationship to the patterns of inflammatory pathology. Fourth, the spatial distribution of chemokine expression could plausibly contribute to lesion architecture. Finally, preliminary observations in MS material suggest that chemokine expression observed in EAE may provide useful information regarding the pathogenesis of inflammation in MS. We propose that temporal and spatial expression of chemokines are crucial factors, complementing adhesion molecule up-regulation, that regulate EAE disease activity.

Presentation of Proteolipid Protein Epitopes and B7-1-Dependent Activation of Encephalitogenic T Cells by IFN-γ-Activated SJL/J Astrocytes

There is controversy regarding the possible role of glial cells as APCs in the pathogenesis of central nervous system (CNS) demyelinating diseases such as multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). Microglia have been clearly shown to present Ag in the CNS, and due to the proximity of activated astroglial cells to infiltrating T cells and macrophages in demyelinating lesions, it is also possible that astrocytes positively or negatively regulate disease initiation and/or progression. We examined the capacity of IFN-γ-treated astrocytes from EAE-susceptible SJL/J mice to process and present myelin epitopes. IFN-γ activation up-regulated ICAM-1, VCAM-1, MHC class II, invariant chain, H2-M, CD40, and B7-1 as determined by FACS and/or RT-PCR analyses. B7-2 expression was only marginally enhanced on SJL/J astrocytes. Consistent with the expression of these accessory molecules, IFN-γ-treated SJL/J astrocytes induced the B7-1-dependent activation of Th1 lines and lymph node T cells specific for the immunodominant encephalitogenic proteolipid protein (PLP) epitope (PLP139–151) as assessed by proliferation and activation for the adoptive transfer of EAE. Interestingly, IFN-γ-activated astrocytes efficiently processed and presented PLP139–151, but not the subdominant PLP178–191, PLP56–70, or PLP104–117 epitopes, from intact PLP and a recombinant variant fusion protein of PLP (MP4). The data are consistent with the hypothesis that astrocytes in the proinflammatory CNS environment have the capability of activating CNS-infiltrating encephalitogenic T cells specific for immunodominant epitopes on various myelin proteins that may be involved in either the initial or the relapsing stages of EAE.

Impaired Macrophage Function and Enhanced T Cell-Dependent Immune Response in Mice Lacking CCR5, the Mouse Homologue of the Major HIV-1 Coreceptor

The CC-chemokine receptor CCR5 has been shown to be the major coreceptor for HIV-1 entry into cells, and humans with homozygous mutation in the ccr5 gene are highly resistant to HIV-1 infection, despite the existence of many other HIV-1 coreceptors. To investigate the physiologic function of CCR5 and to understand the cellular mechanisms of these clinical observations, we generated a CCR5-deficient mouse model (ccr5−/−) by targeted deletion of the ccr5 gene. We found that although developed normally in a pathogen-free environment, CCR5-deficient mice showed reduced efficiency in clearance of Listeria infection and exsert a protective effect aganist LPS-induced endotoxemia, reflecting a partial defect in macrophage function. In addition, CCR5-deficient mice had an enhanced delayed-type hypersensitivity reaction and increased humoral responses to T cell-dependent antigenic challenge, indicating a novel role of CCR5 in down-modulating T cell-dependent immune response.

Cytokine Induction of MIP-1α and MIP-1β in Human Fetal Microglia

Leukocyte infiltration into the central nervous system (CNS) is a key event in the inflammatory processes of neuroimmunologic diseases. Microglia, resident macrophages of the CNS, may contribute to this process by elaborating chemoattractants that are capable of recruiting leukocytes across the blood-brain barrier. Such factors have been detected in the CNS of animal models of multiple sclerosis and in the brains of human and nonhuman primates with AIDS encephalitis. As the expression of these chemoattractants may play an important role in the initiation and progression of neuroimmunologic diseases, we analyzed expression of the chemokines MIP-1α, MIP-1β, MCP-1, and RANTES in human fetal microglial cultures. Unstimulated microglia expressed minimal levels of MIP-1α, MIP-1β, and MCP-1, while RANTES was undetectable. In response to LPS, TNF-α, or IL-1β, both MIP-1α and MIP-1β were induced at the mRNA and protein levels in a dose- and time-dependent manner. IFN-γ did not significantly induce chemokine expression. MCP-1 was detectable in LPS- and cytokine-treated microglia. TGF-β, a cytokine with down-modulatory effects on other cell types, had little effect on chemokine expression in microglia when used concomitantly before or during treatment with LPS. These results illustrate the ability of certain inflammatory stimuli to induce expression of MIP-1α, MIP-1β, and MCP-1 by human fetal microglia. The expression of these chemoattractants may function to recruit inflammatory cells into the CNS during the course of neuroimmunologic diseases and may modulate the ability of HIV to infect the CNS.

Dynamic Regulation of α- and β-Chemokine Expression in the Central Nervous System During Mouse Hepatitis Virus-Induced Demyelinating Disease

Infection of C57BL/6 mice with the V5A13.1 strain of mouse hepatitis virus (MHV-V5A13.1) results in an acute encephalomyelitis and chronic demyelinating disease with features similar to the human demyelinating disease multiple sclerosis. Chemokines are a family of proinflammatory cytokines associated with inflammatory pathology in various diseases. The kinetics and histologic localization of chemokine production in the central nervous system of MHV-infected mice were examined to identify chemokines that contribute to inflammation and demyelination. Transcripts for the chemokines cytokine-response gene-2 (CRG-2), regulated on activation, normal T cell expressed and secreted (RANTES), macrophage-chemoattractant protein-1 and protein-3 (MCP-1, MCP-3), macrophage-inflammatory protein-1β (MIP-1β), and MIP-2 were detected in the brains of MHV-infected mice at 3 days postinfection (p.i.), and these transcripts were increased markedly in brains and spinal cords at day 7 p.i., which coincides with the occurrence of acute viral encephalomyelitis. By day 35 p.i., RANTES, CRG-2, and MIP-1β were detected in brains and spinal cords of mice with chronic demyelination. CRG-2 mRNA expression colocalized with viral RNA and was associated with demyelinating lesions. Astrocytes were the predominant cell type expressing CRG-2 mRNA. These observations suggest a role for chemokines, notably CRG-2, in the initiation and maintenance of an inflammatory response following infection with MHV, which is important in contributing to demyelination.