Both anti-CD11a (LFA-1) and anti-CD11b (MAC-1) therapy delay the onset and diminish the severity of experimental autoimmune encephalomyelitis

Defective Treg generation and increased type 3 immune response in leukocyte adhesion deficiency 1

In 15 Turkish LAD-1 patients and controls, we assessed the impact of pathogenic ITGB2 mutations on Th17/Treg differentiation and functions, and innate lymphoid cell (ILC) subsets. The percentage of peripheral blood Treg cells, in vitro-generated induced Tregs differentiated from naive CD4⁺ T cells were decreased despite the elevated absolute counts of CD4⁺ cells in LAD1 patients. Serum IL-23 levels were elevated in LAD1 patients. Post-curdlan stimulation, LAD1 patient-derived PBMCs produced more IL-17A. Additionally, the percentages of CD18-deficient Th17 cells expanded from total or naïve CD4⁺ T cells were higher. The blood ILC3 subset was significantly elevated in LAD1. Finally, LAD1 PBMCs showed defects in trans-well migration and proliferation and were more resistant to apoptosis. Defects in de novo generation of Tregs from CD18-deficient naïve T cells and elevated Th17s, and ILC3s in LAD1 patients' peripheral blood suggest a type 3-skewed immunity and may contribute to LAD1-associated autoimmune symptoms.

Exercise training alters autoimmune cell invasion into the brain in autoimmune encephalomyelitis

BACKGROUND

The mechanisms by which exercise training (ET) elicits beneficial effects on the systemic immune system and the central nervous system (CNS) in autoimmune neuroinflammation are not fully understood.

OBJECTIVES

To investigate (1) the systemic effects of high-intensity continuous training (HICT) on the migratory potential of autoimmune cells; (2) the direct effects of HICT on blood-brain-barrier (BBB) properties.

METHODS

Healthy mice were subjected to high-intensity continuous training (HICT) by treadmill running. The proteolipid protein (PLP) transfer EAE model was utilized to examine the immunomodulatory effects of training, where PLP-reactive lymph-node cells (LNCs) from HICT and sedentary donor mice were analyzed in vitro and transferred to naïve recipients that developed EAE. To examine neuroprotection, encephalitogenic LNCs from donor mice were transferred into HICT or sedentary recipient mice and the BBB was analyzed.

RESULTS

Transfer of PLP-reactive LNCs obtained from HICT donor mice attenuated EAE severity and inflammation in recipient mice. HICT markedly inhibited very late antigen (VLA)-4 and lymphocyte function-associated antigen (LFA)-1 expression in LNCs. Transfer of encephalitogenic LNCs into HICT recipients resulted in milder EAE and attenuated CNS inflammation. HICT reduced BBB permeability and the expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 in CNS blood vessels.

INTERPRETATION

HICT attenuates EAE development by both immunomodulatory and neuroprotective effects. The reduction in destructive CNS inflammation in EAE is attributed to systemic inhibition of autoreactive cell migratory potential, as well as reduction in BBB permeability, which are associated with reduced VLA-4/VCAM-1 and LFA-1/ICAM-1 interactions.

CEST MRI and MALDI imaging reveal metabolic alterations in the cervical lymph nodes of EAE mice

BACKGROUND

Multiple sclerosis (MS) is a neurodegenerative disease, wherein aberrant immune cells target myelin-ensheathed nerves. Conventional magnetic resonance imaging (MRI) can be performed to monitor damage to the central nervous system that results from previous inflammation; however, these imaging biomarkers are not necessarily indicative of active, progressive stages of the disease. The immune cells responsible for MS are first activated and sensitized to myelin in lymph nodes (LNs). Here, we present a new strategy for monitoring active disease activity in MS, chemical exchange saturation transfer (CEST) MRI of LNs.

METHODS AND RESULTS

We studied the potential utility of conventional (T2-weighted) and CEST MRI to monitor changes in these LNs during disease progression in an experimental autoimmune encephalomyelitis (EAE) model. We found CEST signal changes corresponded temporally with disease activity. CEST signals at the 3.2 ppm frequency during the active stage of EAE correlated significantly with the cellular (flow cytometry) and metabolic (mass spectrometry imaging) composition of the LNs, as well as immune cell infiltration into brain and spinal cord tissue. Correlating primary metabolites as identified by matrix-assisted laser desorption/ionization (MALDI) imaging included alanine, lactate, leucine, malate, and phenylalanine.

CONCLUSIONS

Taken together, we demonstrate the utility of CEST MRI signal changes in superficial cervical LNs as a complementary imaging biomarker for monitoring disease activity in MS. CEST MRI biomarkers corresponded to disease activity, correlated with immune activation (surface markers, antigen-stimulated proliferation), and correlated with LN metabolite levels.

γδ T Cells Participating in Nervous Systems: A Story of Jekyll and Hyde

γδ T cells are distributed in various lymphoid and nonlymphoid tissues, and act as early responders in many conditions. Previous studies have proven their significant roles in infection, cancer, autoimmune diseases and tissue maintenance. Recently, accumulating researches have highlighted the crosstalk between γδ T cells and nervous systems. In these reports, γδ T cells maintain some physiological functions of central nervous system by secreting interleukin (IL) 17, and neurons like nociceptors can in turn regulate the activity of γδ T cells. Moreover, γδ T cells are involved in neuroinflammation such as stroke and multiple sclerosis. This review illustrates the relationship between γδ T cells and nervous systems in physiological and pathological conditions.

A DARPin targeting activated Mac-1 is a novel diagnostic tool and potential anti-inflammatory agent in myocarditis, sepsis and myocardial infarction

The monocyte β₂-integrin Mac-1 is crucial for leukocyte–endothelium interaction, rendering it an attractive therapeutic target for acute and chronic inflammation. Using phage display, a Designed-Ankyrin-Repeat-Protein (DARPin) was selected as a novel binding protein targeting and blocking the α_M I-domain, an activation-specific epitope of Mac-1. This DARPin, named F7, specifically binds to activated Mac-1 on mouse and human monocytes as determined by flow cytometry. Homology modelling and docking studies defined distinct interaction sites which were verified by mutagenesis. Intravital microscopy showed reduced leukocyte–endothelium adhesion in mice treated with this DARPin. Using mouse models of sepsis, myocarditis and ischaemia/reperfusion injury, we demonstrate therapeutic anti-inflammatory effects. Finally, the activated Mac-1-specific DARPin is established as a tool to detect monocyte activation in patients receiving extra-corporeal membrane oxygenation, as well as suffering from sepsis and ST-elevation myocardial infarction. The activated Mac-1-specific DARPin F7 binds preferentially to activated monocytes, detects inflammation in critically ill patients, and inhibits monocyte and neutrophil function as an efficient new anti-inflammatory agent.

Histone deacetylase 1 controls CD4+ T cell trafficking in autoinflammatory diseases

CD4⁺ T cell trafficking is a fundamental property of adaptive immunity. In this study, we uncover a novel role for histone deacetylase 1 (HDAC1) in controlling effector CD4⁺ T cell migration, thereby providing mechanistic insight into why a T cell-specific deletion of HDAC1 protects against experimental autoimmune encephalomyelitis (EAE). HDAC1-deficient CD4⁺ T cells downregulated genes associated with leukocyte extravasation. In vitro, HDAC1-deficient CD4⁺ T cells displayed aberrant morphology and migration on surfaces coated with integrin LFA-1 ligand ICAM-1 and showed an impaired ability to arrest on and to migrate across a monolayer of primary mouse brain microvascular endothelial cells under physiological flow. Moreover, HDAC1 deficiency reduced homing of CD4⁺ T cells into the intestinal epithelium and lamina propria preventing weight-loss, crypt damage and intestinal inflammation in adoptive CD4⁺ T cell transfer colitis. This correlated with reduced expression levels of LFA-1 integrin chains CD11a and CD18 as well as of selectin ligands CD43, CD44 and CD162 on transferred circulating HDAC1-deficient CD4⁺ T cells. Our data reveal that HDAC1 controls T cell-mediated autoimmunity via the regulation of CD4⁺ T cell trafficking into the CNS and intestinal tissues.

Human Commensal Prevotella histicola Ameliorates Disease as Effectively as Interferon-Beta in the Experimental Autoimmune Encephalomyelitis

Gut microbiota has emerged as an important environmental factor in the pathobiology of multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS). Both genetic and environmental factors have been shown to play an important role in MS. Among genetic factors, the human leukocyte antigen (HLA) class II allele such as HLA-DR2, DR3, DR4, DQ6, and DQ8 show the association with the MS. We have previously used transgenic mice expressing MS susceptible HLA class II allele such as HLA-DR2, DR3, DQ6, and DQ8 to validate significance of HLA alleles in MS. Although environmental factors contribute to 2/3 of MS risk, less is known about them. Gut microbiota is emerging as an imporatnt environmental factor in MS pathogenesis. We and others have shown that MS patients have distinct gut microbiota compared to healthy control (HC) with a lower abundance of Prevotella. Additionally, the abundance of Prevotella increased in patients receiving disease-modifying therapies (DMTs) such as Copaxone and/or Interferon-beta (IFNβ). We have previously identified a specific strain of Prevotella (Prevotella histicola), which can suppress experimental autoimmune encephalomyelitis (EAE) disease in HLA-DR3.DQ8 transgenic mice. Since Interferon-β-1b [IFNβ (Betaseron)] is a major DMTs used in MS patients, we hypothesized that treatment with the combination of P. histicola and IFNβ would have an additive effect on the disease suppression. We observed that treatment with P. histicola suppressed disease as effectively as IFNβ. Surprisingly, the combination of P. histicola and IFNβ was not more effective than either treatment alone. P. histicola alone or in combination with IFNβ increased the frequency and number of CD4+FoxP3+ regulatory T cells in the gut-associated lymphoid tissue (GALT). Treatment with P. histicola alone, IFNβ alone, and in the combination decreased frequency of pro-inflammatory IFN-γ and IL17-producing CD4+ T cells in the CNS. Additionally, P. histicola alone or IFNβ alone or the combination treatments decreased CNS pathology, characterized by reduced microglia and astrocytic activation. In conclusion, our study indicates that the human gut commensal P. histicola can suppress disease as effectively as commonly used MS drug IFNβ and may provide an alternative treatment option for MS patients.

γδ T lymphocytes in the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis

The aim of the current review is to summarize the results of studies on the role of γδ T cells in the pathogenesis of multiple sclerosis and its animal model - the experimental autoimmune encephalomyelitis. Despite the fact that numerous studies have been performed, the role of γδ T is still not fully understood. It seems that there are two distinct subpopulations - one exacerbating the disease (IL-17-producing) and the other playing a protective role (IFN-γ-secreting). Nevertheless, future studies are required for an understanding of γδ T cells role in multiple sclerosis.

Past, Present and Future of Therapeutic Interventions Targeting Leukocyte Trafficking in Inflammatory Bowel Disease

Studies in the 1990s using animal models of intestinal inflammation delineated the crucial molecules involved in leukocyte attraction and retention to the inflamed gut and associated lymphoid tissues. The first drug targeting leukocyte trafficking tested in inflammatory bowel diseases was the anti-ICAM-1 antisense oligonucleotide alicaforsen, showing only modest efficacy. Subsequently, the anti-α4 monoclonal antibody natalizumab proved efficacious for induction and maintenance of remission in Crohn's disease, but was associated with progressive multifocal leukoencephalopathy due to its ability to interfere with both α4β1 and α4β7 function. Later developments in this area took advantage of the fairly selective expression of MAdCAM-1 in the digestive organs, showing that vedolizumab, a more specific monoclonal antibody selectively blocking MAdCAM-1 binding to integrin α4β7, was efficacious for induction and maintenance of remission in ulcerative colitis and Crohn's disease, and it was not associated with neurological complications. Currently, other drugs targeting the β7 subunit, immunoglobulin superfamily molecules expressed on the endothelium, as well as blockade of lymphocyte recirculation in lymph nodes through modulation of sphingosine 1-phosphate receptors are under development. The potential use and risks of combined anti-trafficking therapy will be examined in this review.

Monoclonal Antibodies in Preclinical EAE Models of Multiple Sclerosis: A Systematic Review

Monoclonal antibodies (mAb) are promising therapeutics in multiple sclerosis and multiple new candidates have been developed, hence increasing the need for some agreement for preclinical mAb studies. We systematically analyzed publications of experimental autoimmune encephalomyelitis (EAE) studies showing effects of monoclonal antibodies. A PubMed search retrieved 570 records, out of which 122 studies with 253 experiments were eligible based on experimental design, number of animals and presentation of time courses of EAE scores. Analysis of EAE models, treatment schedules, single and total doses, routes of administration, and onset of treatment from pre-immunization up to 35 days after immunization revealed high heterogeneity. Total doses ranged from 0.1 to 360 mg/kg for observation times of up to 35 days after immunization. About half of experiments (142/253) used total doses of 10-70 mg/kg. Employing this range, we tested anti-Itga4 as a reference mAb at varying schedules and got no, mild or substantial EAE-score reductions, depending on the mouse strain and onset of the treatment. The result agrees with the range of outcomes achieved in 10 reported anti-Itga4 experiments. Studies comparing low and high doses of various mAbs or early vs. late onset of treatment did not reveal dose-effect or timing-effect associations, with a tendency towards better outcomes with preventive treatments starting within the first week after immunization. The systematic comparison allows for extraction of some "common" design characteristics, which may be helpful to further assess the efficacy of mAbs and role of specific targets in preclinical models of multiple sclerosis.

Brain-peripheral cell crosstalk in white matter damage and repair

White matter damage is an important part of cerebrovascular disease and may be a significant contributing factor in vascular mechanisms of cognitive dysfunction and dementia. It is well accepted that white matter homeostasis involves multifactorial interactions between all cells in the axon-glia-vascular unit. But more recently, it has been proposed that beyond cell-cell signaling within the brain per se, dynamic crosstalk between brain and systemic responses such as circulating immune cells and stem/progenitor cells may also be important. In this review, we explore the hypothesis that peripheral cells contribute to damage and repair after white matter damage. Depending on timing, phenotype and context, monocyte/macrophage can possess both detrimental and beneficial effects on oligodendrogenesis and white matter remodeling. Endothelial progenitor cells (EPCs) can be activated after CNS injury and the response may also influence white matter repair process. These emerging findings support the hypothesis that peripheral-derived cells can be both detrimental or beneficial in white matter pathology in cerebrovascular disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia, edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Beneficial effect of chronic Staphylococcus aureus infection in a model of multiple sclerosis is mediated through the secretion of extracellular adherence protein

Background

Bacterial infections have been assumed to worsen multiple sclerosis (MS) disease symptoms and to lead to increased neurodegeneration. However, the underlying biological mechanisms for these effects are complex and poorly understood. Here, we assessed the disease-modulating effects of chronic infection with Staphylococcus aureus, a common human pathogen, on the clinical course and the extent of neurodegeneration in experimental autoimmune encephalomyelitis (EAE), an animal model of MS.

Methods

To conduct this study, we established a persistent chronic infection in female brown Norway rats by inoculating Staphylococcus aureus (S. aureus) bacteria in a subcutaneously implanted tissue cages.

Results

In this study, we observed that the introduction of a localized S. aureus infection during the subclinical phase of EAE induced a chronic systemic inflammatory response, consisting of increased T- and B-cell counts and systemic production of proinflammatory cytokines. Unexpectedly, the S. aureus infection completely prevented the development of clinical EAE, and markedly reduced inflammatory infiltration and demyelination of the optic nerve, while it increased the number of surviving retinal neurons. Using a S. aureus strain that lacked the extracellular adherence protein (Eap), we determined that the extracellular adherence protein is at least partially responsible for the inhibitory effect of S. aureus infection on autoimmune inflammation of the central nervous system.

Conclusions

Our results demonstrate for the first time that chronic infection with S. aureus has a beneficial effect on EAE, indicating a dual role of infection in the pathogenesis of MS. We also showed that secretion of Eap by S. aureus plays a major role in preventing autoimmune inflammation of the CNS. Moreover, we identified Eap as a factor responsible for this protective effect.

Leukocyte integrins: role in leukocyte recruitment and as therapeutic targets in inflammatory disease

Infection or sterile inflammation triggers site-specific attraction of leukocytes. Leukocyte recruitment is a process comprising several steps orchestrated by adhesion molecules, chemokines, cytokines and endogenous regulatory molecules. Distinct adhesive interactions between endothelial cells and leukocytes and signaling mechanisms contribute to the temporal and spatial fine-tuning of the leukocyte adhesion cascade. Central players in the leukocyte adhesion cascade include the leukocyte adhesion receptors of the β2-integrin family, such as the αLβ2 and αMβ2 integrins, or of the β1-integrin family, such as the α4β1-integrin. Given the central involvement of leukocyte recruitment in different inflammatory and autoimmune diseases, the leukocyte adhesion cascade in general, and leukocyte integrins in particular, represent key therapeutic targets. In this context, the present review focuses on the role of leukocyte integrins in the leukocyte adhesion cascade. Experimental evidence that has implicated leukocyte integrins as targets in animal models of inflammatory disorders, such as experimental autoimmune encephalomyelitis, psoriasis, inflammatory bone loss and inflammatory bowel disease as well as preclinical and clinical therapeutic applications of antibodies that target leukocyte integrins in various inflammatory disorders are presented. Finally, we review recent findings on endogenous inhibitors that modify leukocyte integrin function, which could emerge as promising therapeutic targets.

Neuroinvasion by Chandipura virus

Chandipura virus (CHPV) is an arthropod borne rhabdovirus associated with acute encephalitis in children below the age of 15 years in the tropical states of India. Although the entry of the virus into the nervous system is among the crucial events in the pathogenesis of CHPV, the exact mechanism allowing CHPV to invade the central nervous system (CNS) is currently poorly understood. In the present review, based on the knowledge of host interactors previously predicted for CHPV, along with the support from experimental data available for other encephalitic viruses, the authors have speculated the various plausible modes by which CHPV could surpass the blood-brain barrier and invade the CNS to cause encephalitis whilst evading the host immune surveillance. Collectively, this review provides a conservative set of potential interactions that can be employed for future experimental validation with a view to better understand the neuropathogenesis of CHPV.

Long-term impact of neonatal inflammation on demyelination and remyelination in the central nervous system

Perinatal inflammation causes immediate changes of the blood-brain barrier (BBB) and thus may have different consequences in adult life including an impact on neurological diseases such as demyelinating disorders. In order to determine if such a perinatal insult affects the course of demyelination in adulthood as "second hit," we simulated perinatal bacterial inflammation by systemic administration of lipopolysaccharide (LPS) to either pregnant mice or newborn animals. Demyelination was later induced in adult animals by cuprizone [bis(cyclohexylidenehydrazide)], which causes oligodendrocyte death with subsequent demyelination accompanied by strong microgliosis and astrogliosis. A single LPS injection at embryonic day 13.5 did not have an impact on demyelination in adulthood. In contrast, serial postnatal LPS injections (P0-P8) caused an early delay of myelin removal in the corpus callosum, which was paralleled by reduced numbers of activated microglia. During remyelination, postnatal LPS treatment enhanced early remyelination with a concomitant increase of mature oligodendrocytes. Furthermore, the postnatal LPS challenge impacts the phenotype of microglia since an elevated mRNA expression of microglia related genes such as TREM 2, CD11b, TNF-α, TGF-β1, HGF, FGF-2, and IGF-1 was found in these preconditioned mice during early demyelination. These data demonstrate that postnatal inflammation has long-lasting effects on microglia functions and modifies the course of demyelination and remyelination in adulthood.

Inflammatory monocytes and the pathogenesis of viral encephalitis

Monocytes are a heterogeneous population of bone marrow-derived cells that are recruited to sites of infection and inflammation in many models of human diseases, including those of the central nervous system (CNS). Ly6C^hi/CCR2^hi inflammatory monocytes have been identified as the circulating precursors of brain macrophages, dendritic cells and arguably microglia in experimental autoimmune encephalomyelitis; Alzheimer’s disease; stroke; and more recently in CNS infection caused by Herpes simplex virus, murine hepatitis virus, Theiler’s murine encephalomyelitis virus, Japanese encephalitis virus and West Nile virus. The precise differentiation pathways and functions of inflammatory monocyte-derived populations in the inflamed CNS remains a contentious issue, especially in regard to the existence of monocyte-derived microglia. Furthermore, the contributions of monocyte-derived subsets to viral clearance and immunopathology are not well-defined. Thus, understanding the pathways through which inflammatory monocytes migrate to the brain and their functional capacity within the CNS is critical to inform future therapeutic strategies. This review discusses some of the key aspects of inflammatory monocyte trafficking to the brain and addresses the role of these cells in viral encephalitis.

Tolerability, pharmacokinetics and pharmacodynamics of CMAB001, an anti-CD11a antibody, in Chinese healthy volunteers and psoriatic patients

AIM

To evaluate the pharmacokinetics (PK), pharmacodynamics (PD) and primary tolerability of an anti-CD11a monoclonal antibody (CMAB001) in Chinese healthy volunteers and psoriatic patients.

METHODS

Two open-label studies were conducted. One was a parallel-group, single-center, dose-escalation test, including 24 healthy adult volunteers from 18 to 45 years in age. All subjects randomly received a single subcutaneous injection dose of 0.5, 1.0 or 2.0 mg/kg. The other was a multiple-dose study: 10 adult psoriatic patients were administered weekly subcutaneous injections of 1.0 mg/kg for 7 weeks.

RESULTS

CMAB001 was well tolerated in the single- and multiple-dose studies. Slow absorption was observed in both studies. In the single-dose study, the concentration of CMAB001 reached its highest level 2 d later after the injection, and the C(max) increased in an approximate dose-proportionate manner, while the area under curve (AUC) showed much greater than dose-proportionate increase. In the multiple-dose study, the steady-state serum concentration level was attained following the 4th injection.

CONCLUSION

CMAB001 exhibited a nonlinear pharmacokinetic profile over the dose range from 0.5 to 2.0 mg/kg, and was well tolerated in healthy volunteers and psoriatic patients.

Antigen-specific blocking of CD4-specific immunological synapse formation using BPI and current therapies for autoimmune diseases

In this review, we discuss T-cell activation, etiology, and the current therapies of autoimmune diseases (i.e., MS, T1D, and RA). T-cells are activated upon interaction with antigen-presenting cells (APC) followed by a "bull's eye"-like formation of the immunological synapse (IS) at the T-cell-APC interface. Although the various disease-modifying therapies developed so far have been shown to modulate the IS and thus help in the management of these diseases, they are also known to present some undesirable side effects. In this study, we describe a novel and selective way to suppress autoimmunity by using a bifunctional peptide inhibitor (BPI). BPI uses an intercellular adhesion molecule-1 (ICAM-1)-binding peptide to target antigenic peptides (e.g., proteolipid peptide, glutamic acid decarboxylase, and type II collagen) to the APC and therefore modulate the immune response. The central hypothesis is that BPI blocks the IS formation by simultaneously binding to major histocompatibility complex-II and ICAM-1 on the APC and selectively alters the activation of T cells from T(H)1 to T(reg) and/or T(H)2 phenotypes, leading to tolerance.

Progesterone attenuates demyelination and microglial reaction in the lysolecithin-injured spinal cord

Progesterone treatment of mice with experimental autoimmune encephalomyelitis has shown beneficial effects in the spinal cord according to enhanced clinical, myelin and neuronal-related parameters. In the present work, we report progesterone effects in a model of primary demyelination induced by the intraspinal injection of lysophospatidylcholine (LPC). C57Bl6 adult male mice remained steroid-untreated or received a single 100 mg progesterone implant, which increased circulating steroid levels to those of mouse pregnancy. Seven days afterwards mice received a single injection of 1% LPC into the dorsal funiculus of the spinal cord. A week after, anesthetized mice were perfused and paraffin embedded sections of the spinal cord stained for total myelin using Luxol Fast Blue (LFB) histochemistry, for myelin basic protein (MBP) immunohistochemistry and for determination of OX-42+ microglia/macrophages. Cryostat sections were also prepared and stained for oligodendrocyte precursors (NG2+ cells) and mature oligodendrocytes (CC1+ cells). A third batch of spinal cords was prepared for analysis of the microglial marker CD11b mRNA using qPCR. Results showed that progesterone pretreatment of LPC-injected mice decreased by 50% the area of demyelination, evaluated by either LFB staining or MBP immunostaining, increased the density of NG2+ cells and of mature, CC1+ oligodendrocytes and decreased the number of OX-42+ cells, respect of steroid-untreated LPC mice. CD11b mRNA was hyperexpressed in LPC-treated mice, but significantly reduced in LPC-mice receiving progesterone. These results indicated that progesterone antagonized LPC injury, an effect involving (a) increased myelination; (b) stimulation of oligodendrocyte precursors and mature oligodendrocytes, and (c) attenuation of the microglial/macrophage response. Thus, use of a focal demyelination model suggests that progesterone exerts promyelinating and anti-inflammatory effects at the spinal cord level.

Crawling phagocytes recruited in the brain vasculature after pertussis toxin exposure through IL6, ICAM1 and ITGαM

The cerebral vasculature is constantly patrolled by rod-shaped leukocytes crawling on the luminal endothelial surface. These cells are recruited in greater numbers after exposure to bacterial lipopolysaccharide (LPS) by a mechanism involving tumor necrosis factor (TNF), interleukin-1β (IL1β) and angiopoietin-2 (Angpt2). Here, we report that the population of crawling leukocytes, consisting mainly of granulocytes, is also increased in the brains of mice suffering from experimental autoimmune encephalomyelitis (EAE) or injected with pertussis toxin (PTX), which is commonly used to induce EAE. However, this recruitment occurs through an alternative mechanism, independent of Angpt2. In a series of experiments using DNA microarrays, knockout mice and neutralizing antibodies, we found that PTX acts indirectly on the endothelium in part through IL6, which is essential for the post-transcriptional upregulation of intercellular adhesion molecule 1 (ICAM1) in response to PTX but not to LPS. We also found that phagocytes adhere to brain capillaries through the interaction of integrin αM (ITGαM) with ICAM1 and an unidentified ligand. In conclusion, this study supports the concept that PTX promotes EAE, at least in part, by inducing vascular changes necessary for the recruitment of patrolling leukocytes.

MicroRNA-124 promotes microglia quiescence and suppresses EAE by deactivating macrophages via the C/EBP-α-PU.1 pathway

MicroRNAs are a family of regulatory molecules involved in many physiological processes, including differentiation and activation of cells of the immune system. We found that brain-specific miR-124 is expressed in microglia but not in peripheral monocytes or macrophages. When overexpressed in macrophages, miR-124 directly inhibited the transcription factor CCAAT/enhancer-binding protein-α (C/EBP-α) and its downstream target PU.1, resulting in transformation of these cells from an activated phenotype into a quiescent CD45(low), major histocompatibility complex (MHC) class II(low) phenotype resembling resting microglia. During experimental autoimmune encephalomyelitis (EAE), miR-124 was downregulated in activated microglia. Peripheral administration of miR-124 in EAE caused systemic deactivation of macrophages, reduced activation of myelin-specific T cells and marked suppression of disease. Conversely, knockdown of miR-124 in microglia and macrophages resulted in activation of these cells in vitro and in vivo. These findings identify miR-124 both as a key regulator of microglia quiescence in the central nervous system and as a previously unknown modulator of monocyte and macrophage activation.

Reduced Treg frequency in LFA-1-deficient mice allows enhanced T effector differentiation and pathology in EAE

The αLβ2-integrin LFA-1 (CD11a/CD18) is known as an important molecule for leukocyte migration. However, the precise role of LFA-1 in the pathogenesis of EAE has so far remained unclear. We describe here the disease development in LFA-1(-/-) mice compared with WT controls. Ablation of LFA-1 resulted in more severe EAE with increased demyelination and increased numbers of myelin oligodendrocyte glycoprotein-reactive CD4(+) T cells in the CNS. However, the production of the pro-inflammatory cytokines IL-17 and IFN-γ was unchanged on the level of antigen-specific T cells. Interestingly, LFA-1-deficient mice showed a clearly reduced frequency of Treg in the inflamed CNS. Moreover, Treg counts in spleens and thymi of unimmunized LFA-1(-/-) mice were lower in comparison to the WT controls, indicating an impairment of Treg generation. In combination, these results suggest a substantial role of LFA-1 in Treg generation and subsequent expansion of effector T cells and highlight the importance of Treg in limiting EAE.

Binding of recombinant T cell receptor ligands (RTL) to antigen presenting cells prevents upregulation of CD11b and inhibits T cell activation and transfer of experimental autoimmune encephalomyelitis

Recombinant T cell ligands (RTLs) ameliorate experimental autoimmune encephalomyelitis (EAE) in an antigen-specific manner. We evaluated effects of RTL401 (I-A(s) alpha1beta1+PLP-139-151) on splenocytes from SJL/J mice with EAE to study RTL-T cell tolerance-inducing mechanisms. RTLs bound to B, macrophages and DCs, through RTL-MHC-alpha1beta1 moiety. RTL binding reduced CD11b expression on splenic macrophages/DC, and RTL401-conditioned macrophages/DC, not B cells, inhibited T cell activation. Reduced ability of RTL- incubated splenocytes to transfer EAE was likely mediated through macrophages/DC, since B cells were unnecessary for RTL treatment of EAE. These results demonstrate a novel pathway of T cell regulation by RTL-bound APCs.

Haptoglobin deficiency facilitates the development of autoimmune inflammation

Haptoglobin (HP) is an acute phase protein synthesized by liver cells in response to IL-6. HP has been demonstrated to modulate the immune response and to have anti-inflammatory activities. To analyze HP's effect on autoimmune inflammation, we here studied the course of EAE induced by immunization of Hp knockout (Hp(-/-)) and syngeneic WT mice with myelin oligodendrocyte glycoprotein peptide (MOG(35-55)). Hp(-/-)mice suffered from a more severe disease that was associated with increased expression of IL-17A, IL-6, and IFN-gamma mRNA in the CNS and with a denser cellular infiltrate in the spinal cord. During the recovery phase, a significantly higher number of myeloid DC, CD8+ cells, IL-17+ CD4+ and IFN-gamma+ CD4+ cells persisted in the CNS of Hp(-/-) mice. Absence of HP affected the priming and differentiation of T cells after MOG(35-55) immunization, as levels of Th2 cytokines produced in response to MOG stimulation by Hp(-/-) T cells were reduced. These results suggest that HP plays a modulatory and protective role on autoimmune inflammation of the CNS.

beta2-integrins in demyelinating disease: not adhering to the paradigm

The beta(2)-integrins are a subfamily of integrins expressed on leukocytes that play an essential role in leukocyte trafficking, activation, and many other functions. Studies in EAE, the animal model for multiple sclerosis, show differential requirements for beta(2)-integrins in this disease model, ranging from critical in the case of LFA-1 (CD11a/CD18) to unimportant in the case of CD11d/CD18. Importantly, expression of beta(2)-integrins on T cell subsets provides some clues as to the function(s) these adhesion molecules play in disease development. For example, transferred EAE studies have shown that Mac-1 (CD11b/CD18) expression on alphabeta T cells is critical for disease development, and the absence of LFA-1 on Tregs in recipient mice results in exacerbated disease. In this review, we summarize recent findings regarding the role of beta(2)-integrins in demyelinating disease and new information about the role of beta(2)-integrins with respect to alterations in Treg numbers and function. In addition, we discuss the potential for targeting beta(2)-integrins in human demyelinating disease in light of the recent animal model studies.

Extracellular adherence protein of Staphylococcus aureus suppresses disease by inhibiting T-cell recruitment in a mouse model of psoriasis

Psoriasis is a T-cell-mediated inflammatory disease. Previous studies focused on lymphocyte function-associated antigen 1 (LFA-1)-expressing T cells as a molecular target for therapeutic intervention. By contrast, information on therapeutic effects and the underlying mechanism of blocking the LFA-1 counter receptor, ICAM-1 is scarce. Here, we used the CD18 (beta2-integrin) hypomorphic (CD18hypo) mouse model of psoriasis to investigate the therapeutic role of extracellular adherence protein (Eap) of Staphylococcus aureus, which exerts antiinflammatory activities by interacting with the ICAM-1 function. We show that ICAM-1 is predominantly upregulated on endothelial cells in lesional skin of CD18hypo mice. In vitro Eap was found to disrupt cell-cell contacts between T cells and dendritic cells, and inhibit T-cell proliferation. By contrast, in vivo Eap rather blocked transmigration of T cells from vessels to inflamed skin of CD18hypo mice, but did not inhibit their proliferation and activation. Most importantly, Eap successfully suppressed the disease by blocking T-cell extravasation into the inflamed skin. Together, these data indicate that interaction between LFA-1 and ICAM-1 is causally involved in the pathogenesis of psoriasiform skin inflammation, and targeting ICAM-1 to selectively block T-cell extravasation by Eap without immune suppression may represent a potential therapeutic strategy for psoriasis.

Effector and suppressor roles for LFA-1 during the development of experimental autoimmune encephalomyelitis

LFA-1 (CD11a/CD18) is a member of the beta(2)-integrin family of adhesion molecules important in leukocyte trafficking and activation. Although LFA-1 is thought to contribute to the development of experimental autoimmune encephalomyelitis (EAE) primarily through its functions on effector T cells, its importance on other leukocyte populations remains unexplored. To address this question, we performed both adoptive transfer EAE experiments involving CD11a(-/-) mice and trafficking studies using bioluminescent T cells expressing luciferase under the control of a CD2 promoter (T-lux cells). Transfer of encephalitogenic CD11a(-/-) T cells to wild type mice resulted in a significant reduction in overall EAE severity compared to control transfers. We also observed, using in vivo imaging techniques, that CD11a(-/-) T-lux cells readily infiltrated lymph nodes and the CNS of wild type recipients with kinetics comparable to CD11a(+/+) transfers, although their overall numbers in these organs were reduced. Surprisingly, transfer of encephalitogenic wild type T cells to CD11a(-/-) mice induced a severe and sometimes fatal EAE disease course, associated with massive T cell infiltration and proliferation in the CNS. These data indicate that LFA-1 expression on leukocytes in recipient mice plays an important immunomodulatory role in EAE. Thus, LFA-1 acts as a key regulatory adhesion molecule during the development of EAE, serving both pro- and anti-inflammatory roles in disease pathogenesis.

Production of CCL2 by central nervous system cells regulates development of murine experimental autoimmune encephalomyelitis through the recruitment of TNF- and iNOS-expressing macrophages and myeloid dendritic cells

Experimental autoimmune encephalomyelitis is a T cell-mediated demyelinating disease of the CNS that serves as a model for the human disease multiple sclerosis. Increased expression of the chemokine CCL2 in the CNS has been demonstrated to be important in the development of demyelinating disease presumably by attracting inflammatory cells. However, the mechanism of how CCL2 regulates disease pathogenesis has not been fully elucidated. Using radiation bone marrow chimeric mice we demonstrated that optimum disease was achieved when CCL2 was glia derived. Furthermore, CNS production of CCL2 resulted in the accumulation of iNOS-producing CD11b(+)CD11c(+) dendritic cells and TNF-producing macrophages important for demyelination. Lack of glial-derived CCL2 production did not influence experimental autoimmune encephalomyelitis by altering either Th1 or Th17 cells, as there were no differences in these populations in the CNS or periphery between groups. These results demonstrate that the glial-derived CCL2 is important for the attraction of TNF- and iNOS-producing dendritic cells and effector macrophages to the CNS for development of subsequent autoimmune disease.

Structural modifications of ICAM-1 cyclic peptides to improve the activity to inhibit heterotypic adhesion of T cells

Lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1) interaction plays an important role in the formation of the immunological synapse between T cells and antigen-presenting cells. Blocking of LFA-1/ICAM-1 interactions has been shown to suppress the progression of autoimmune diseases. cIBR peptide (cyclo(1,12)PenPRGGSVLVTGC) inhibits ICAM-1/LFA-1 interaction by binding to the I-domain of LFA-1. To increase the bioactivity of cIBR peptide, we systemically modified the structure of the peptide by (i) replacing the Pen residue at the N-terminus with Cys, (ii) cyclization using amide bond formation between Lys-Glu side chains, and (iii) reducing the peptide size by eliminating the C-terminal residue. We found that the activity of cIBR peptide was not affected by replacing Phe with Cys. Peptide cyclization by forming the Lys-Glu amide bond also increased the activity of cIBR peptide, presumably due to the resistance of the amide bond to the reducing nature of glutathione in plasma. We also found that a reduced derivative of cIBR with eight residues (cyclo(1,8)CPRGGSVC) has a bioactivity similar to that of the larger cIBR peptides. Our findings suggest that, by systemically modifying the structure of cIBR peptide, the biological activity of these derivatives can be optimized for future use to inhibit T-cell adhesion in in vivo models of autoimmune diseases.

Effect of therapeutic integrin (CD11a) blockade with efalizumab on immune responses to model antigens in humans: results of a randomized, single blind study

Efalizumab is a humanized monoclonal CD11a antibody approved for treatment of psoriasis. Its immunomodulatory effects led us study how immune responses are modified and the possible consequences for vaccinations in clinical practice. This was a randomized, single-blind, placebo-controlled, parallel-group study of 12 weeks of subcutaneous efalizumab treatment of patients with moderate psoriasis. Bacteriophage phiX174 was used as a model neoantigen to assess T-cell-dependent humoral immunity. Tetanus booster vaccine, pneumococcal vaccine, and intracutaneous skin tests were administered to further evaluate humoral and cellular immune responses. During efalizumab treatment, both primary and secondary antibody responses to phiX174, including IgM/IgG isotype switch, were reduced. There appeared to be naïve T-cell anergy to a neoantigen (phiX174) during active CD11a blockade, without tolerance to the antigen after efalizumab withdrawal. Secondary humoral immune responses to tetanus booster during treatment were reduced, but antibody titer increases led to protective levels. Responses to pneumococcal vaccination 6 weeks after withdrawal from efalizumab were not affected. Cellular immune responses to intracutaneous recall antigens were reduced during treatment and returned to pretreatment conditions after withdrawal. These results expand our knowledge of how immune responses are modulated in humans by CD11a blockade and have implications for vaccinations of patients treated with this agent.

Blockade of CD11a by efalizumab in psoriasis patients induces a unique state of T-cell hyporesponsiveness

Efalizumab (anti-CD11a) interferes with LFA-1/ICAM-1 binding and inhibits several key steps in psoriasis pathogenesis. This study characterizes the effects of efalizumab on T-cell activation responses and expression of surface markers on human circulating psoriatic T cells during a therapeutic trial. Our data suggest that efalizumab may induce a unique type of T-cell hyporesponsiveness, directly induced by LFA-1 binding, which is distinct from conventional anergy described in animal models. Direct activation of T cells through different activating receptors (CD2, CD3, CD3/28) is reduced, despite T cells being fully viable. This hyporesponsiveness was spontaneously reversible after withdrawal of the drug, and by IL-2 in vitro. In contrast to the state of anergy, Ca(+2) release is intact during efalizumab binding. Furthermore, lymphocyte function-associated antigen-1 (LFA-1) blockade resulted in an unexpected downregulation of a broad range of surface molecules, including the T-cell receptor complex, co-stimulatory molecules, and integrins unrelated to LFA-1, both in the peripheral circulation and in diseased skin tissue. These observations provide evidence for the mechanism of action of efalizumab. The nature of this T-cell hyporesponsiveness suggests that T-cell responses may be reduced during efalizumab therapy, but are reversible after ceasing efalizumab treatment.

Differential expression of beta 2-integrins and cytokine production between gammadelta and alphabeta T cells in experimental autoimmune encephalomyelitis

The expression of beta 2-integrins on gammadelta T cells in naïve mice or those with experimental autoimmune encephalomyelitis (EAE) remains poorly characterized. We compared beta 2-integrin expression and cytokine production between gammadelta and alphabeta T cells over the acute course of EAE. We observed that unlike in alphabeta T cells, beta 2-integrin expression on gammadelta T cells increased significantly from baseline, peaked at Day 10, and remained unchanged in the draining lymph nodes or declined in the spleen and CNS by Day 15. In addition, IFN-gamma- and TNF-alpha-producing gammadelta T cells infiltrated the CNS rapidly and produced significantly more of these cytokines than alphabeta T cells throughout the course of EAE. These results suggest unique roles for beta 2-integrins in the trafficking of gammadelta versus alphabeta T cells during EAE and that gammadelta T cells infiltrate the CNS rapidly, producing cytokines, which modulate acute disease.

p150/95 (CD11c/CD18) expression is required for the development of experimental autoimmune encephalomyelitis

p150/95 (CD11c/CD18, CR4) is a member of the beta(2)-integrin family of adhesion molecules and is considered an important phagocytic receptor. The role of p150/95 in the development of central nervous system demyelinating diseases, including multiple sclerosis, remains unexplored. To determine p150/95-mediated mechanisms in experimental autoimmune encephalomyelitis (EAE), we performed EAE using CD11c-deficient (CD11c(-/-)) mice. EAE in CD11c(-/-) mice was significantly attenuated and characterized by markedly reduced spinal cord T-cell infiltration and interferon-gamma production by these cells. Adoptive transfer of antigen-restimulated T cells from wild-type to CD11c(-/-) mice produced significantly attenuated EAE, whereas transfer of CD11c(-/-) antigen-restimulated T cells to control mice induced a very mild, monophasic EAE. T cells from MOG(35-55) peptide-primed CD11c(-/-) mice displayed an unusual cytokine phenotype with elevated levels of interleukin (IL)-2, IL-4, and IL-12 but reduced levels of interferon-gamma, tumor necrosis factor-alpha, IL-10, IL-17, and transforming growth factor-beta compared with control mice. Overall, CD11c(-/-) T cells from primed mice proliferated comparably to that of control T cells on MOG(35-55) restimulation. Our results indicate that expression of p150/95 is critical on both T cells as well as other leukocytes for the development of demyelinating disease and may represent a novel therapeutic target for multiple sclerosis.

[Update on pathophysiologic and immunotherapeutic approaches for the treatment of multiple sclerosis]

Multiple sclerosis (MS) is a chronic disabling disease with significant implications for patients and society. The individual disease course is difficult to predict due to the heterogeneity of clinical presentation and of radiologic and pathologic findings. Although its etiology still remains unknown, the last decade has brought considerable understanding of the underlying pathophysiology of MS. In addition to its acceptance as a prototypic inflammatory autoimmune disorder, recent data reveal the importance of primary and secondary neurodegenerative mechanisms such as oligodendrocyte death, axonal loss, and ion channel dysfunction. The deepened understanding of its immunopathogenesis and the limited effectiveness of currently approved disease-modifying therapies have led to a tremendous number of trials investigating potential new drugs. Emerging treatments take into account the different immunopathological mechanisms and strategies, to protect against axonal damage and promote remyelination. This review provides a compilation of novel immunotherapeutic strategies and recently uncovered aspects of known immunotherapeutic agents. The pathogenetic rationale of these novel drugs for the treatment of MS and accompanying preclinical and clinical data are highlighted.

Importance of IFN-γ-Mediated Expression of Endothelial VCAM-1 on Recruitment of CD8+T Cells into the Brain During Chronic Infection withToxoplasma gondii

Interferon-gamma (IFNgamma) is essential for preventing reactivation of chronic infection with Toxoplasma gondii in the brain. We examined the role of IFNgamma on lymphocyte and endothelial adhesion molecule expression and T cell recruitment into the brain during chronic infection with T. gondii in IFNgamma knockout (IFNgamma(-/-)) and wild-type (WT) mice. Although the number of cerebral vessels expressing intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) increased in both WT and IFNgamma(-/-) mice following infection, there were more VCAM-1(+) vessels in brains of infected WT than of infected IFNgamma(-/-) mice; in contrast, numbers of ICAM-1(+) vessels did not differ between strains. We did not detect endothelial E-selectin, P-selectin, MAdCAM-1, or PNAd in any of the brains. Significantly fewer CD8(+) T cells were recruited into brains of infected IFNgamma(-/-) than WT mice. Treatment of infected IFNgamma(-/-) mice with recombinant IFN-gamma restored the expression of VCAM-1 on their cerebral vessels and recruitment of CD8(+) T cells into their brains, confirming an importance of this cytokine for upregulation of VCAM-1 expression and CD8(+) T cell trafficking. In infected WT and IFNgamma(-/-) animals, almost all cerebral CD8(+) T cells were lymphocyte function-associated antigen-1 (LFA-1)(high), CD44(high), and CD62L(neg), and approximately 38% were alpha4beta1 integrin(+). In adoptive transfer of immune spleen cells, pretreatment of the cells with a monoclonal antibody (mAb) against alpha4 integrin markedly inhibited recruitment of CD8(+) T cells into the brain of chronically infected WT mice. These results indicate that IFN-gamma-induced expression of endothelial VCAM-1 and its binding to alpha4beta1 integrin on CD8(+) T cells is important for recruitment of the T cells into the brain during the chronic stage of T. gondii infection, although LFA-1/ICAM-1 interaction may also be involved in this process.

Disruption of the beta2-integrin CD11d (alphaDbeta2) gene fails to protect against experimental autoimmune encephalomyelitis

The fourth member of the beta(2)-integrin family of adhesion molecules, CD11d (alpha(D)beta(2)), is expressed on a wide variety of immune cells, however its function in autoimmune diseases, including EAE remains unknown. We induced EAE in wild-type and CD11d(-/-) C57BL/6 mice using myelin oligodendrocyte glycoprotein (MOG(35-55)) peptide. The clinical course and histopathology of EAE were identical in both groups of mice throughout the disease course. There were no significant differences in the infiltration of leukocyte subsets into the central nervous system or in the production of cytokines from T cells isolated from the spleen or spinal cord from both groups of mice. Our data demonstrate that CD11d is not required for the development of EAE and, to date, is the only beta(2)-integrin molecule whose deletion does not result in attenuated disease.

Intercellular adhesion molecule-1 expression is required on multiple cell types for the development of experimental autoimmune encephalomyelitis

Many members of the Ig superfamily of adhesion molecules, such as ICAM-1 and VCAM-1, have been implicated in the pathogenesis of multiple sclerosis. Although it is well-established that VCAM-1/VLA-4 interactions can play important roles in mediating CNS inflammatory events in multiple sclerosis patients and during the development of experimental allergic encephalomyelitis (EAE), the contributions of ICAM-1 are poorly understood. This is due in large part to conflicting results from Ab inhibition studies and the observation of exacerbated EAE in ICAM-1 mutant mice that express a restricted set of ICAM-1 isoforms. To determine ICAM-1-mediated mechanisms in EAE, we analyzed ICAM-1 null mutant mice (ICAM-1(null)), which express no ICAM-1 isoforms. ICAM-1(null) mice had significantly attenuated EAE characterized by markedly reduced spinal cord T cell infiltration and IFN-gamma production by these cells. Adoptive transfer of Ag-restimulated T cells from wild-type to ICAM-1(null) mice or transfer of ICAM-1(null) Ag-restimulated T cells to control mice failed to induce EAE. ICAM-1(null) T cells also showed reduced proliferative capacity and substantially reduced levels of IFN-gamma, TNF-alpha, IL-4, IL-10, and IL-12 compared with that of control T cells following myelin oligodendrocyte glycoprotein 35-55 restimulation in vitro. Our results indicate that ICAM-1 expression is critical on T cells and other cell types for the development of demyelinating disease and suggest that expression of VCAM-1 and other adhesion molecules cannot fully compensate for the loss of ICAM-1 during EAE development.

Persistent macrophage/microglial activation and myelin disruption after experimental autoimmune encephalomyelitis in tissue inhibitor of metalloproteinase-1-deficient mice

Increased leukocyte trafficking into the parenchyma during inflammatory responses in the central nervous system (CNS) is facilitated by the extracellular proteolytic activities of matrix metalloproteinases that are regulated, in part, by the endogenous tissue inhibitors of metalloproteinases (TIMPs). In experimental autoimmune encephalomyelitis (EAE), TIMP-1 gene expression is induced in astrocytes surrounding inflammatory lesions in the CNS. The physiological importance of this temporal and spatial relationship is not clear. Herein, we have addressed the functional role of TIMP-1 in a myelin oligodendrocyte glycoprotein (MOG35-55)-induced model of EAE using TIMP-1-deficient (TIMP-1-/-) C57BL/6 mice. Although CD4+ T-cell immune responses to myelin in wild-type (WT) and TIMP-1-/- mice were similar, analysis of CNS tissues from TIMP-1-/- mice after EAE revealed more severe myelin pathology than that of WT mice. This disruption of myelin was associated with both increased lymphocyte infiltration and microglial/macrophage accumulation in the brain parenchyma. These findings suggest that induction of TIMP-1 by astrocytes during EAE in WT mice represents an inherent cytoprotective response that mitigates CNS myelin injury through the regulation of both immune cell infiltration and microglial activation.

A critical role of LFA-1 in the development of Th17 cells and induction of experimental autoimmune encephalomyelytis

The alphaLbeta2 integrin adhesion molecule LFA-1 is believed to be involved in the migration of autoreactive T cells to the central nervous system across the endothelial blood-brain barrier in experimental autoimmune encephalomyelitis (EAE). Here, we demonstrate that the incidence and clinical scores of EAE in LFA-1-/- mice induced by the immunization with the myelin oligodendrocyte glycoprotein (MOG)-peptide antigen were significantly lower than those in wild type mice. Further studies demonstrated that lymphocytes recruitment to the draining lymph nodes (dLN) after the immunization with the MOG-peptide was severely suppressed in LFA-1-/- mice. Moreover, generation of the MOG-specific IL-17-producing helper T (Th17) cells in the dLN was impaired in LFA-1-/- mice. These results suggest that LFA-1 may play an important role for the generation of MOG-specific Th17 cells in the dLN as well as the immigration of MOG-specific naïve CD4+ T cells to the dLN.

The CD11a Binding Site of Efalizumab in Psoriatic Skin Tissue as Analyzed by Multi-Epitope Ligand Cartography Robot Technology

Efalizumab (Raptiva) is an immunomodulating recombinant humanized IgG1 monoclonal antibody that binds to CD11a, the alpha-subunit of leukocyte function antigen-1 (LFA-1). By blocking the binding of LFA-1 to ICAM-1, efalizumab inhibits the adhesion of leukocytes to other cell types and interferes with the migration of T lymphocytes to sites of inflammation (including psoriatic skin plaques). Analysis of the response in patients treated with efalizumab to date shows that distinct groups of responders and nonresponders to the drug exist. It would therefore be of great practical value to be able to predict which patients are most likely to respond to treatment, by identifying key parameters in the mechanism of action of efalizumab. Detailed investigation and detection of multiple epitopes in microcompartments of skin tissue has until recently been restricted by the available technology. However, the newly developed technique of Multi-Epitope Ligand Cartography (MELC) robot technology combines proteomics and biomathematical tools to visualize protein networks at the cellular and subcellular levels in situ, and to decipher cell functions. The MELC technique, which is outlined in this paper, was used to help characterize the binding of efalizumab to affected and unaffected psoriatic skin as compared to normal control skin under ex vivomodel conditions. Efalizumab was labeled with fluorescein isothiocyanate and integrated into a MELC library of more than 40 antibodies. These antibodies were selected for their potential to detect epitopes which may be indicative of (a) various cell types, (b) structural components of the extracellular matrix, or (c) the processes of cell proliferation, activation and adhesion. Efalizumab bound to CD11a in affected psoriatic skin by a factor 15x and 32x higher than in unaffected psoriatic skin and normal control skin, respectively. CD11a and the efalizumab binding site were primarily expressed in the extravascular dermis, whereas CD54 (ICAM-1) as its ligand was most prevalent in the dermal vessels. T lymphocytes (for which the markers were CD3, CD8, CD4, and CD45R0) were the major cellular targets of efalizumab. In contrast, NK cells were only a minor target of efalizumab. Our study demonstrated that efalizumab represents a treatment for psoriasis that primarily targets memory CD4+ and CD8+ T cells and has a high specificity for psoriatic disease activity. Moreover, we hereby introduce the novel principle of a biological drug-binding biochip assay being especially useful for the future monitoring of psoriatic skin lesions under efalizumab treatment conditions.

Antibodies to Complement Receptor 3 Treat Established Inflammation in Murine Models of Colitis and a Novel Model of Psoriasiform Dermatitis

Prior studies indicated the ability of Abs to complement receptor 3 (CR3, CD11b/CD18) to suppress the production of IL-12 from immune cells. Therefore, we tested the ability of an anti-CR3 Ab (clone M1/70) to treat established IL-12-dependent Th1-mediated inflammation in murine models. Systemic administration of anti-CR3 significantly ameliorated established intestinal inflammation following the intrarectal administration of trinitrobenzene sulfonic acid (TNBS-colitis), as well as colitis and skin inflammation in C57BL/10 RAG-2(-/-) mice reconstituted with CD4+CD45RBhigh T cells. The hyperproliferative skin inflammation in this novel murine model demonstrated many characteristics of human psoriasis, and was prevented by the adoptive transfer of CD45RBlow T cells. In vitro and in vivo studies suggest that anti-CR3 treatment may act, at least in part, by directly inhibiting IL-12 production by APCs. Administration of anti-CR3 may be a useful therapeutic approach to consider for the treatment of inflammatory bowel disease and psoriasis in humans.

Differential activation of microglia in neurogenic versus non-neurogenic regions of the forebrain

Proliferation decreases in the neurogenic subventricular zone (SVZ) of mice after aspiration lesions of the cerebral cortex. We hypothesized that microglial activation may contribute to this given microglial activation attenuates neurogenesis in the hippocampus. Using CD45, CD11b, IB4, and IL-6 immunohistochemistry (IHC), BrdU IHC, and fluorescent bead tracking of peripheral monocytes into the brain, we compared microglial activation in the SVZ to non-neurogenic forebrain regions. SVZ microglia exhibited greater constitutive activation and proliferation than did microglia in non-neurogenic regions. In contrast to the SVZ, the dentate gyrus (DG) contained relatively few CD45(+) cells. After aspiration cerebral cortex lesions, microglia became activated in the cerebral cortex, corpus callosum, and striatum. SVZ microglial activation did not increase, and similarly, microglia in the DG were less activated after injury than in adjacent non-neurogenic regions. We next showed that SVZ microglia are not categorically refractory to activation, since deep cortical contusion injuries increased SVZ microglial activation. Macrophages migrate into the brain during development, but it is unclear if this is recapitulated after injury. Infiltration of microbead-labeled macrophages into the brain did not change after injury, but resident SVZ microglia were induced to migrate toward the injury. Our data show that both constitutive and postlesion levels of microglial activation differ between neurogenic and non-neurogenic regions.

Macrophages inhibit neovascularization in a murine model of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 y of age in at least three continents. Choroidal neovascularization (CNV) is the process by which abnormal blood vessels develop underneath the retina. CNV develops in 10% of patients with AMD but accounts for up to 90% of the blindness from AMD. Although the precise etiology of CNV in AMD remains unknown, the macrophage component of the inflammatory response, which has been shown to promote tumor growth and support atherosclerotic plaque formation, is thought to stimulate aberrant angiogenesis in blinding eye diseases. The current theory is that macrophage infiltration promotes the development of neovascularization in CNV.

METHODS AND FINDINGS

We examined the role of macrophages in a mouse model of CNV. IL-10(-/-) mice, which have increased inflammation in response to diverse stimuli, have significantly reduced CNV with increased macrophage infiltrates compared to wild type. Prevention of macrophage entry into the eye promoted neovascularization while direct injection of macrophages significantly inhibited CNV. Inhibition by macrophages was mediated by the TNF family death molecule Fas ligand (CD95-ligand).

CONCLUSIONS

Immune vascular interactions can be highly complex. Normal macrophage function is critical in controlling pathologic neovascularization in the eye. IL-10 regulates macrophage activity in the eye and is an attractive therapeutic target in order to suppress or inhibit CNV in AMD that can otherwise lead to blindness.

Resistance to experimental autoimmune encephalomyelitis and impaired IL-17 production in protein kinase C theta-deficient mice

The protein kinase C theta (PKC theta) serine/threonine kinase has been implicated in signaling of T cell activation, proliferation, and cytokine production. However, the in vivo consequences of ablation of PKC theta on T cell function in inflammatory autoimmune disease have not been thoroughly examined. In this study we used PKC theta-deficient mice to investigate the potential involvement of PKC theta in the development of experimental autoimmune encephalomyelitis, a prototypic T cell-mediated autoimmune disease model of the CNS. We found that PKC theta-/- mice immunized with the myelin oligodendrocyte glycoprotein (MOG) peptide MOG(35-55) were completely resistant to the development of clinical experimental autoimmune encephalomyelitis compared with wild-type control mice. Flow cytometric and histopathological analysis of the CNS revealed profound reduction of both T cell and macrophage infiltration and demyelination. Ex vivo MOG(35-55) stimulation of splenic T lymphocytes from immunized PKC theta-/- mice revealed significantly reduced production of the Th1 cytokine IFN-gamma as well as the T cell effector cytokine IL-17 despite comparable levels of IL-2 and IL-4 and similar cell proliferative responses. Furthermore, IL-17 expression was dramatically reduced in the CNS of PKC theta-/- mice compared with wild-type mice during the disease course. In addition, PKC theta-/- T cells failed to up-regulate LFA-1 expression in response to TCR activation, and LFA-1 expression was also significantly reduced in the spleens of MOG(35-55)-immunized PKC theta-/- mice as well as in in vitro-stimulated CD4+ T cells compared with wild-type mice. These results underscore the importance of PKC theta in the regulation of multiple T cell functions necessary for the development of autoimmune disease.

Suppression of experimental autoimmune encephalomyelitis by extracellular adherence protein of Staphylococcus aureus

Multiple sclerosis (MS) is a devastating inflammatory disorder of the central nervous system (CNS). A major hallmark of MS is the infiltration of T cells reactive against myelin components. T cell infiltration is mediated by the interaction of integrins of the beta1 and beta2 family expressed by lymphocytes with their endothelial counter-receptors, vascular cell adhesion molecule 1 and intercellular adhesion molecule (ICAM)-1, respectively. We have reported previously that extracellular adherence protein (Eap) of Staphylococcus aureus exerts antiinflammatory activities by interacting with ICAM-1 and blocking beta2-integrin-dependent neutrophil recruitment. Here, we report that Eap inhibits experimental autoimmune encephalomyelitis (EAE) in mice. In vitro, Eap reduced adhesion of peripheral blood T cells to immobilized ICAM-1 as well as their adhesion and transmigration of TNF-activated human endothelium under static and shear flow conditions. These inhibitory effects were corroborated in two mouse models of inflammation. In a delayed-type hypersensitivity model, both T cell infiltration and the corresponding tissue edema were significantly reduced by Eap. In addition, Eap administration prevented the development of EAE and markedly decreased infiltration of inflammatory cells into the CNS. Strikingly, intervention with Eap after the onset of EAE suppressed the disease. Collectively, our findings indicate that Eap represents an attractive treatment for autoimmune neuroinflammatory disorders such as MS.

The complement system plays a critical role in the development of experimental autoimmune anterior uveitis

PURPOSE

The role of complement in ocular autoimmunity was explored in a experimental autoimmune anterior uveitis (EAAU) animal model.

METHODS

EAAU was induced in Lewis rats by immunization with bovine melanin-associated antigen. Complement activation in the eye was monitored by Western blot for iC3b. The importance of complement to the development of EAAU was studied by comparing the course of intraocular inflammation in normal Lewis rats (complement-sufficient) with cobra venom factor-treated rats (complement-depleted). Eyes were harvested from both complement-sufficient and complement-depleted rats for mRNA and protein analysis for IFN-gamma, IL-10, and interferon-inducible protein (IP)-10. Intracellular adhesion molecule (ICAM)-1 and leukocyte-endothelial cell adhesion molecule (LECAM)-1 were detected by immunofluorescent staining. OX-42 was used to investigate the importance of iC3b and CR3 interaction in EAAU.

RESULTS

There was a correlation between ocular complement activation and disease progression in EAAU. The incidence, duration, and severity of disease were dramatically reduced after active immunization in complement-depleted rats. Complement depletion also completely suppressed adoptive transfer EAAU. The presence of complement was critical for local production of cytokines (IFN-gamma and IL-10), chemokines (IP-10), and adhesion molecules (ICAM-1 and LECAM-1) during EAAU. Furthermore, intraocular complement activation, specifically iC3b production and engagement of complement receptor 3 (CR3), had a significant impact on disease activity in EAAU.

CONCLUSIONS

The study provided the novel finding that complement activation plays a central role in the pathogenesis of ocular autoimmunity and may serve as a potential target for therapeutic intervention.

Complement and demyelinating disease: no MAC needed?

It has long been accepted that the complement system participates in the onset, evolution, and exacerbation of demyelinating disease, and it is widely suspected that this is accomplished mainly via destruction of nervous tissue by membrane attack complex (MAC)-mediated lysis of oligodendrocytes and neurons. However, recent studies using mutant mice indicate the MAC may not be so important. For example, mice lacking C5 and mice lacking the C5a receptor both develop experimental autoimmune encephalomyelitis (EAE) with the same frequency and intensity as their wild type counterparts. Also, transgenic mice that express C5a exclusively in the central nervous system (CNS) develop EAE that is not remarkably different from that in non-transgenic littermates. Since C5 is required for formation of the MAC, development of fulminant EAE in the absence of this complement protein demonstrates that non-complement-mediated mechanisms of CNS damage are operating. Paradoxically, mice lacking C3, mice lacking the C3a receptor, and mice lacking the complement receptor type 3 develop attenuated EAE, while mice that express C3a exclusively in the CNS develop severe and often fulminant EAE. Based on these newer data, we posit that C3-derived biologically active fragments, rather than C5 and the MAC, are central players in the pathophysiology of complement in EAE.

Critical requirement of CD11b (Mac-1) on T cells and accessory cells for development of experimental autoimmune encephalomyelitis

Mac-1 (CD18/CD11b) is a member of the beta2-integrin family of adhesion molecules and is implicated in the development of many inflammatory diseases. The role of Mac-1 in the development of CNS demyelinating diseases, including multiple sclerosis, is not understood, and Ab inhibition studies in experimental allergic encephalomyelitis (EAE), the animal model for multiple sclerosis, have produced conflicting findings. To clarify these results and to determine Mac-1-mediated mechanisms in EAE, we performed EAE using Mac-1-deficient mice. Mac-1 homozygous-deficient, but not Mac-1 heterozygous-deficient mice, had significantly delayed onset and attenuated EAE. Leukocyte infiltration was similar in both groups of mice in early disease but significantly reduced in spinal cords of receptor-deficient mice in late disease. Adoptive transfer of Ag-restimulated T cells from wild-type to Mac-1-deficient mice produced significantly attenuated EAE, whereas transfer of Mac-1-deficient Ag-restimulated T cells to control mice failed to induce EAE. T cells from myelin oligodendrocyte glycoprotein (MOG)35-55 peptide-primed Mac-1-deficient mice displayed an altered cytokine phenotype with elevated levels of TGF-beta and IL-10, but reduced levels of IL-2, IFN-gamma, TNF-alpha, IL-12, and IL-4 compared with control mice. Mac-1-deficient T cells from primed mice proliferated comparably to that of control T cells on MOG35-55 restimulation in vitro. However, the draining lymph nodes of MAC-1-deficient mice on day 10 after MOG35-55 immunization contained lower frequency of blast T cells than in control mice, suggesting poor priming. Our results indicate that Mac-1 expression is critical on both phagocytic cells and T cells for the development of demyelinating disease.

Targeting integrin structure and function in disease

Initially linked to the pathogenesis of inflammatory and hematologic diseases, integrins have become validated drug targets with the approval of five drugs. Moreover, there are several promising drug candidates in preclinical and clinical stages of development for multiple clinical indications. Integrins are attractive drug targets as their antagonism can block several steps in disease progression or maintenance. Integrin inhibitors can block the proliferation, migration, or tissue localization of inflammatory, angiogenic, and tumor cells, as well as signaling and gene expression contributing to disease. There has been a rapid increase in the elucidation of integrin structure, their allosteric mechanisms of bidirectional signaling, and the structure of complexes with drugs. This information brings greater focus to how integrins support various cellular functions and how they have been and may be targeted to develop novel drugs. Here we review conformational switches, including an internal ligand, which allosterically regulate the transition from low- to high-affinity ligand binding. We address some of the successes, disappointments, and challenges in targeting competitive or allosteric sites to develop therapeutics. We also discuss new opportunities, including a structure-based approach to discover novel drugs to treat inflammatory and other diseases. This approach targets structural relatives of the von Willebrand factor A-domain present in integrins and many functionally diverse proteins.