The role of integrins in immune-mediated diseases of the nervous system

Astroglial Cell-to-Cell Interaction with Autoreactive Immune Cells in Experimental Autoimmune Encephalomyelitis Involves P2X7 Receptor, β3-Integrin, and Connexin-43

In multiple sclerosis (MS), glial cells astrocytes interact with the autoreactive immune cells that attack the central nervous system (CNS), which causes and sustains neuroinflammation. However, little is known about the direct interaction between these cells when they are in close proximity in the inflamed CNS. By using an experimental autoimmune encephalomyelitis (EAE) model of MS, we previously found that in the proximity of autoreactive CNS-infiltrated immune cells (CNS-IICs), astrocytes respond with a rapid calcium increase that is mediated by the autocrine P2X7 receptor (P2X7R) activation. We now reveal that the mechanisms regulating this direct interaction of astrocytes and CNS-IICs involve the coupling between P2X7R, connexin-43, and β3-integrin. We found that P2X7R and astroglial connexin-43 interact and concentrate in the immediate proximity of the CNS-IICs in EAE. P2X7R also interacts with β3-integrin, and the block of astroglial αvβ3-integrin reduces the P2X7R-dependent calcium response of astrocytes upon encountering CNS-IICs. This interaction was dependent on astroglial mitochondrial activity, which regulated the ATP-driven P2X7R activation and facilitated the termination of the astrocytic calcium response evoked by CNS-IICs. By further defining the interactions between the CNS and the immune system, our findings provide a novel perspective toward expanding integrin-targeting therapeutic approaches for MS treatment by controlling the cell-cell interactions between astrocytes and CNS-IICs.

Amyloid precursor protein (APP) and amyloid β (Aβ) interact with cell adhesion molecules: Implications in Alzheimer’s disease and normal physiology

Alzheimer’s disease (AD) is an incurable neurodegenerative disorder in which dysfunction and loss of synapses and neurons lead to cognitive impairment and death. Accumulation and aggregation of neurotoxic amyloid-β (Aβ) peptides generated via amyloidogenic processing of amyloid precursor protein (APP) is considered to play a central role in the disease etiology. APP interacts with cell adhesion molecules, which influence the normal physiological functions of APP, its amyloidogenic and non-amyloidogenic processing, and formation of Aβ aggregates. These cell surface glycoproteins also mediate attachment of Aβ to the neuronal cell surface and induce intracellular signaling contributing to Aβ toxicity. In this review, we discuss the current knowledge surrounding the interactions of cell adhesion molecules with APP and Aβ and analyze the evidence of the critical role these proteins play in regulating the processing and physiological function of APP as well as Aβ toxicity. This is a necessary piece of the complex AD puzzle, which we should understand in order to develop safe and effective therapeutic interventions for AD.

Therapeutic Potential of Astrocyte Purinergic Signalling in Epilepsy and Multiple Sclerosis

Epilepsy and multiple sclerosis (MS), two of the most common neurological diseases, are characterized by the establishment of inflammatory environment in the central nervous system that drives disease progression and impacts on neurodegeneration. Current therapeutic approaches in the treatments of epilepsy and MS are targeting neuronal activity and immune cell response, respectively. However, the lack of fully efficient responses to the available treatments obviously shows the need to search for novel therapeutic candidates that will not exclusively target neurons or immune cells. Accumulating knowledge on epilepsy and MS in humans and analysis of relevant animal models, reveals that astrocytes are promising therapeutic candidates to target as they participate in the modulation of the neuroinflammatory response in both diseases from the initial stages and may play an important role in their development. Indeed, astrocytes respond to reactive immune cells and contribute to the neuronal hyperactivity in the inflamed brain. Mechanistically, these astrocytic cell to cell interactions are fundamentally mediated by the purinergic signalling and involve metabotropic P2Y1 receptors in case of astrocyte interactions with neurons, while ionotropic P2X7 receptors are mainly involved in astrocyte interactions with autoreactive immune cells. Herein, we review the potential of targeting astrocytic purinergic signalling mediated by P2Y1 and P2X7 receptors to develop novel approaches for treatments of epilepsy and MS at very early stages.

Natalizumab therapy in patients with pediatric-onset multiple sclerosis in Greece: clinical and immunological insights of time-long administration and future directions-a single-center retrospective observational study

Pediatric-onset multiple sclerosis (MS, POMS) accounts for 3-5% of all MS cases and is characterized by a highly inflammatory profile, often warranting treatment with high-efficacy agents. Our aim is to present real-world data of a series of 18 Hellenic POMS patients treated with natalizumab (NTZ) either as adolescents or as adults, after high disease activity has efficiently subsided. Clinical and imaging/laboratory data from 18 POMS patients who have received at least one NTZ infusion were selected in this single-center retrospective observational study. Human leukocyte antigen (HLA) genotyping was performed with standard low-resolution sequence-specific oligonucleotide techniques. Eighteen patients with a mean age of disease onset of 15.3 ± 2.4 years were treated with NTZ with a mean of 51.7 ± 46.4 infusions, 6 as adolescents and 12 as adults. 22.2% were treatment naïve. At the end of the observational period, patients of both groups remained relapse-free, with no radiological activity and significantly reduced disability accumulation. No evidence of disease activity (NEDA)-3 status was achieved in 66.7% of all patients, 58.3% in the adult-treated, and 83.3% in the adolescent-treated POMS patients. NTZ was generally well tolerated. Only 5 adverse events were observed, in 3 patients who were carriers of the HLA-DRB1*15 (HLA-DRB1*15/HLA-DRB1*11 and HLA-DRB1*15/HLA-DRB1*13 genotypes), 1 homozygous for the HLA-DRB1*03 allele and 1 heterozygous for HLA-DRB1*04 and HLA-DRB1*16 alleles. NTZ is highly efficacious and mostly safe for POMS patients with high disease activity in all age groups. The role of immunogenetics in personalized patient evaluation and treatment needs to be further investigated.

CX3CR1 But Not CCR2 Expression Is Required for the Development of Autoimmune Peripheral Neuropathy in Mice

One hallmark of Guillain-Barre syndrome (GBS), a prototypic autoimmune peripheral neuropathy (APN) is infiltration of leukocytes (macrophages and T cells) into peripheral nerves, where chemokines and their receptors play major roles. In this study, we aimed to understand the potential contribution of chemokine receptors CCR2 and CX3CR1 in APN by using a well-established mouse model, B7.2 transgenic (L31) mice, which possesses a predisposed inflammatory background. We crossbred respectively CCR2KO and CX3CR1KO mice with L31 mice. The disease was initiated by partial ligation on one of the sciatic nerves. APN pathology and neurological function were evaluated on the other non-ligated sciatic nerve/limb. Our results revealed that L31/CX3CR1KO but not L31/CCR2KO mice were resistant to APN. CX3CR1 is needed for maintaining circulating monocyte and CD8⁺ T cell survival. While migration of a significant number of activated CD8⁺ T cells to peripheral nerves is essential in autoimmune response in nerve, recruitment of monocytes into PNS seems optional. Disease onset is independent of CCR2 mediated blood-derived macrophage recruitment, which can be replaced by compensatory proliferation of resident macrophages in peripheral nerve. CX3CR1 could also contribute to APN via its critical involvement in maintaining nerve macrophage phagocytic ability. We conclude that blockade of CX3CR1 signaling may represent an interesting anti-inflammatory strategy to improve therapeutic management for GBS patients.

The Role of Ninjurin1 and Its Impact beyond the Nervous System

Ninjurin1 (Ninj1) is a double-transmembrane cell surface protein that could promote nerve regeneration in the process of the peripheral nervous system injury and repairment. Nonetheless, the accurate function of Ninj1 in the central nervous system and outside the nervous system is not completely clear. According to the recent studies, we found that Ninj1 is also aberrantly expressed in various pathophysiological processes in vivo, including inflammation, tumorigenesis, and vascular, bone, and muscle homeostasis. These findings suggest that Ninj1 may play an influential role during these pathophysiological processes. Our review summarizes the diverse roles of Ninj1 in multiple pathophysiological processes inside and outside the nervous system. Ninj1 should be considered as an important and novel therapeutic target in certain diseases, such as inflammatory diseases and ischemic diseases. Our study provided a better understanding of Ninj1 in different pathophysiological processes and thereby provided the theoretical support for further research.

Central nervous system-infiltrated immune cells induce calcium increase in astrocytes via astroglial purinergic signaling

Interaction between autoreactive immune cells and astroglia is an important part of the pathologic processes that fuel neurodegeneration in multiple sclerosis. In this inflammatory disease, immune cells enter into the central nervous system (CNS) and they spread through CNS parenchyma, but the impact of these autoreactive immune cells on the activity pattern of astrocytes has not been defined. By exploiting naïve astrocytes in culture and CNS-infiltrated immune cells (CNS IICs) isolated from rat with experimental autoimmune encephalomyelitis (EAE), here we demonstrate previously unrecognized properties of immune cell-astrocyte interaction. We show that CNS IICs but not the peripheral immune cell application, evokes a rapid and vigorous intracellular Ca²⁺ increase in astrocytes by promoting glial release of ATP. ATP propagated Ca²⁺ elevation through glial purinergic P2X7 receptor activation by the hemichannel-dependent nucleotide release mechanism. Astrocyte Ca²⁺ increase is specifically triggered by the autoreactive CD4⁺ T-cell application and these two cell types exhibit close spatial interaction in EAE. Therefore, Ca²⁺ signals may mediate a rapid astroglial response to the autoreactive immune cells in their local environment. This property of immune cell-astrocyte interaction may be important to consider in studies interrogating CNS autoimmune disease.

Targeting the blood-nerve barrier for the management of immune-mediated peripheral neuropathies

Healthy peripheral nerves encounter, with increased frequency, numerous chemical, biological, and biomechanical forces. Over time and with increasing age, these forces collectively contribute to the pathophysiology of a spectrum of traumatic, metabolic, and/or immune-mediated peripheral nerve disorders. The blood-nerve barrier (BNB) serves as a critical first-line defense against chemical and biologic insults while biomechanical forces are continuously buffered by a dense array of longitudinally orientated epineural collagen fibers exhibiting high-tensile strength. As emphasized throughout this Experimental Neurology Special Issue, the BNB is best characterized as a functionally dynamic multicellular vascular unit comprised of not only highly specialized endoneurial endothelial cells, but also associated perineurial cells, pericytes, Schwann cells, basement membrane, and invested axons. The composition of the BNB, while anatomically distinct, is not functionally dissimilar to that of the well characterized neurovascular unit of the central nervous system. While the BNB lacks a glial limitans and an astrocytic endfoot layer, the primary function of both vascular units is to establish, maintain, and protect an optimal endoneurial (PNS) or interstitial (CNS) fluid microenvironment that is vital for proper neuronal function. Altered endoneurial homeostasis as a secondary consequence of BNB dysregulation is considered an early pathological event in the course of a variety of traumatic, immune-mediated, or metabolically acquired peripheral neuropathies. In this review, emerging experimental advancements targeting the endoneurial microvasculature for the therapeutic management of immune-mediated inflammatory peripheral neuropathies, including the AIDP variant of Guillain-Barré syndrome, are discussed.

Direct Binding of the Flexible C-Terminal Segment of Periaxin to β4 Integrin Suggests a Molecular Basis for CMT4F

The process of myelination in the nervous system requires a coordinated formation of both transient and stable supramolecular complexes. Myelin-specific proteins play key roles in these assemblies, which may link membranes to each other or connect the myelinating cell cytoskeleton to the extracellular matrix. The myelin protein periaxin is known to play an important role in linking the Schwann cell cytoskeleton to the basal lamina through membrane receptors, such as the dystroglycan complex. Mutations that truncate periaxin from the C terminus cause demyelinating peripheral neuropathy, Charcot-Marie-Tooth (CMT) disease type 4F, indicating a function for the periaxin C-terminal region in myelination. We identified the cytoplasmic domain of β4 integrin as a specific high-affinity binding partner for periaxin. The C-terminal region of periaxin remains unfolded and flexible when bound to the third fibronectin type III domain of β4 integrin. Our data suggest that periaxin is able to link the Schwann cell cytoplasm to the basal lamina through a two-pronged interaction via different membrane protein complexes, which bind close to the N and C terminus of this elongated, flexible molecule.

Genome-wide pathway-based association analysis identifies risk pathways associated with Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. It is generally believed that it is influenced by both genetic and environmental factors, but the precise pathogenesis of PD is unknown to date. In this study, we performed a pathway analysis based on genome-wide association study (GWAS) to detect risk pathways of PD in three GWAS datasets. We first mapped all SNP markers to autosomal genes in each GWAS dataset. Then, we evaluated gene risk values using the minimum P-value of the tagSNPs. We took a pathway as a unit to identify the risk pathways based on the cumulative risks of the genes in the pathway. Finally, we combine the analysis results of the three datasets to detect the high risk pathways associated with PD. We found there were five same pathways in the three datasets. Besides, we also found there were five pathways which were shared in two datasets. Most of these pathways are associated with nervoussystem. Five pathways had been reported to be PD-related pathways in the previous literature. Our findings also implied that there was a close association between immune response and PD. Continued investigation of these pathways will further help us explain the pathogenesis of PD.

Evaluating Soluble EMMPRIN as a Marker of Disease Activity in Multiple Sclerosis: Studies of Serum and Cerebrospinal Fluid

Extracellular matrix metalloproteinase inducer (EMMPRIN, CD147) is an inducer of matrix metalloproteinases and has roles in leukocyte activation and migration. We reported previously that in MS and its animal model, experimental autoimmune encephalomyelitis, cell surface-associated EMMPRIN was significantly elevated in leukocytes around inflammatory perivascular cuffs in the CNS. In this study we report that activated T-cells can secrete soluble form of EMMPRIN (sEMMPRIN) upon activation. As sEMMPRIN is also present in biological fluids, we determined whether sEMMPRIN is altered in the CSF and sera of MS subjects. Sera from individuals without neurological conditions served as controls, while CSFs collected from subjects undergoing discectomy, and without evidence of CNS pathology, were used as a comparator group. We found that serum levels of sEMMPRIN from clinically stable MS patients or other inflammatory conditions did not differ from control subjects. Paired serum and CSF samples demonstrated poor correlation of sEMMPRIN. Interestingly, sEMMPRIN levels were approximately 60% higher in CSFs compared to sera. sEMMPRIN CSF levels were significantly higher in secondary progressive compared to primary progressive subjects. Thus we conclude that measurement of sEMMPRIN in serum is not informative for disease activity in MS. The differential expression of sEMMPRIN in the CSF of primary and secondary progressive MS invites hypotheses of the still undefined roles of EMMPRIN in the CNS.

Neuroimmunotherapies Targeting T Cells: From Pathophysiology to Therapeutic Applications

Therapeutic options for multiple sclerosis (MS) have significantly increased over the last few years. T lymphocytes are considered to play a central role in initiating and perpetuating the pathological immune response. Currently approved therapies for MS target T lymphocytes, either in an unspecific manner or directly by interference with specific T-cell pathways. While the concept of "T-cell-specific therapy" implies specificity and selectivity, currently approved approaches come from a general shaping of the immune system towards anti-inflammatory immune responses by non-T-cell-selective immune suppression or immune modulation (e.g., interferons-immune modulation approach) to a depletion of immune cell populations involving T cells (e.g., anti-CD52, alemtuzumab-immune selective depletion approach), or a selective inhibition of distinct molecular pathways in order to sequester leucocytes (e.g., natalizumab-leukocyte sequestration approach). This review will highlight the rationale and results of different T-cell-directed therapeutic approaches coming from basic animal experiments to clinical trials. We will first discuss the pathophysiological rationale for targeting T lymphocytes in MS leading to currently approved treatments acting on T lymphocytes. Furthermore, we will disuss previous promising concepts that have failed to show efficacy in clinical trials or were halted as a result of unexpected adverse events. Learning from the discrepancies between expectations and failures in practical outcomes helps to optimize future research approaches and clinical study designs. As our current view of MS pathogenesis and patient needs is rapidly evolving, novel therapeutic approaches targeting T lymphocytes will also be discussed, including specific molecular interventions such as cytokine-directed treatments or strategies enhancing immunoregulatory mechanisms. Based on clinical experience and novel pathophysiological approaches, T-cell-based strategies will remain a pillarstone of MS therapy.

Human mesenchymal stem cells target adhesion molecules and receptors involved in T cell extravasation

Introduction

Systemic delivery of bone marrow-derived mesenchymal stem cells (MSC) seems to be of benefit in the treatment of multiple sclerosis (MS), an autoimmune disease of the central nervous system (CNS) sustained by migration of T cells across the brain blood barrier (BBB) and subsequent induction of inflammatory lesions into CNS. MSC have been found to modulate several effector functions of T cells. In this study, we investigated the effects of MSC on adhesion molecules and receptors on T cell surface that sustain their transendothelial migration.

Methods

We used different co-culture methods combined with real-time PCR and flow cytometry to evaluate the expression both at the mRNA and at the plasma-membrane level of α4 integrin, β2 integrin, ICAM-1 and CXCR3. In parallel, we assessed if MSC are able to modulate expression of adhesion molecules on the endothelial cells that interact with T cells during their transendothelial migration.

Results

Our in vitro analyses revealed that MSC: (i) inhibit proliferation and activation of both peripheral blood mononuclear cells (PBMC) and CD3⁺-selected lymphocytes through the release of soluble factors; (ii) exert suppressive effects on those surface molecules highly expressed by activated lymphocytes and involved in transendothelial migration; (iii) inhibit CXCL10-driven chemotaxis of CD3⁺ cells; (iv) down-regulated expression of adhesion molecules on endothelial cells.

Conclusions

Taken together, these data demonstrate that the immunosuppressive effect of MSC does not exclusively depends on their anti-proliferative activity on T cells, but also on the impairment of leukocyte migratory potential through the inhibition of the adhesion molecules and receptors that are responsible for T cell trafficking across BBB. This could suggest a new mechanism through which MSC modulate T cell responses.

Chronic inflammatory demyelinating polyradiculoneuropathy: from pathology to phenotype

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an inflammatory neuropathy, classically characterised by a slowly progressive onset and symmetrical, sensorimotor involvement. However, there are many phenotypic variants, suggesting that CIDP may not be a discrete disease entity but rather a spectrum of related conditions. While the abiding theory of CIDP pathogenesis is that cell-mediated and humoral mechanisms act together in an aberrant immune response to cause damage to peripheral nerves, the relative contributions of T cell and autoantibody responses remain largely undefined. In animal models of spontaneous inflammatory neuropathy, T cell responses to defined myelin antigens are responsible. In other human inflammatory neuropathies, there is evidence of antibody responses to Schwann cell, compact myelin or nodal antigens. In this review, the roles of the cellular and humoral immune systems in the pathogenesis of CIDP will be discussed. In time, it is anticipated that delineation of clinical phenotypes and the underlying disease mechanisms might help guide diagnostic and individualised treatment strategies for CIDP.

Fibronectin inhibits chronic pain development after spinal cord injury

Chronic pain following spinal cord injury (SCI) is a highly prevalent clinical condition that is difficult to treat. Using both von Frey filaments and radiant infrared heat to assess mechanical allodynia and thermal hyperalgesia, respectively, we have demonstrated that a one-time injection of fibronectin (50 μg/mL) into the spinal dorsal column (1 μL/min each injection for a total of 5 μL) immediately after SCI inhibits the development of mechanical allodynia (but not thermal hyperalgesia) over an 8-month observation period following spinal cord dorsal column crush (DCC). DCC will only induce mechanical Allodynia, but not thermal hyperalgesia or overt motor deficits. By applying various fibronectin fragments as well as competitive inhibitors, these effects were shown to be dependent on the connecting segment-1 (CS-1) motif of fibronectin. Furthermore, we found that acute fibronectin treatment diminished inflammation and blood-spinal cord barrier permeability, which in turn leads to enhanced fiber sparing and sprouting. In particular, the reduction of serotonin (5-HT) in the superficial dorsal horn, an important descending brainstem system in the modulation of pain, was blocked with fibronectin treatment. We conclude that treatment of SCI with fibronectin preserves sensory regulation and prevents the development of chronic allodynia, providing a potential therapeutic intervention to treat chronic pain following SCI.

Natalizumab in pediatric multiple sclerosis patients

Pediatric multiple sclerosis (MS) comprises 2-5% of all cases of MS. Although first-line disease-modifying therapy (DMT) including interferons and glatiramer acetate appear to be well tolerated in this population, recent work has suggested that a growing number of children suffer from disease which is resistant to treatment with these therapies. Natalizumab is a therapy which, although associated with a 1 : 1000 risk for progressive multifocal leukoencephalopathy (PML), has been shown to be well tolerated in the adult population and may lead to disease remission in adults with highly active disease. Reports of use of this therapy in the pediatric population with highly active disease have been published. This paper reviews current experience with the use of natalizumab in the pediatric MS population, with attention to potential risks and possible long-term outcomes in this population.

Rapid identification of fluorochrome modification sites in proteins by LC ESI-Q-TOF mass spectrometry

Conjugation of either a fluorescent dye or a drug molecule to the ε-amino groups of lysine residues of proteins has many applications in biology and medicine. However, this type of conjugation produces a heterogeneous population of protein conjugates. Because conjugation of fluorochrome or drug molecule to a protein may have deleterious effects on protein function, the identification of conjugation sites is necessary. Unfortunately, the identification process can be time-consuming and laborious; therefore, there is a need to develop a rapid and reliable way to determine the conjugation sites of the fluorescent label or drug molecule. In this study, the sites of conjugation of fluorescein-5'-isothiocyanate and rhodamine-B-isothiocyanate to free amino groups on the insert-domain (I-domain) protein derived from the α-subunit of lymphocyte function-associated antigen-1 (LFA-1) were determined by electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF MS) along with peptide mapping using trypsin digestion. A reporter fragment of the fluorochrome moiety that is generated in the collision cell of the Q-TOF without explicit MS/MS precursor selection was used to identify the conjugation site. Selected ion plots of the reporter ion readily mark modified peptides in chromatograms of the complex digest. Interrogation of theses spectra reveals a neutral loss/precursor pair that identifies the modified peptide. The results show that one to seven fluorescein molecules or one to four rhodamine molecules were attached to the lysine residue(s) of the I-domain protein. No modifications were found in the metal ion-dependent adhesion site (MIDAS), which is an important binding region of the I-domain.

Utilization of I-domain of LFA-1 to Target Drug and Marker Molecules to Leukocytes

The long-term objective of this project is to utilize the I-domain protein for the α-subunit of LFA-1 to target drugs to lymphocytes by binding to ICAM receptors on the cell surface. The short-term goal is to provide proof-of-concept that I-domain conjugated to small molecules can still bind to and uptake by ICAM-1 on the surface of lymphocytes (i.e., Raji cells). To accomplish this goal, the I-domain protein was labeled with FITC at several lysine residues to produce the FITC-I-domain and CD spectroscopy showed that the FITC-I-domain has a secondary structure similar to that of the parent I-domain. The FITC-I-domain was taken up by Raji cells via receptor-mediated endocytosis and its uptake can be blocked by anti-I-domain mAb but not by its isotype control. Antibodies to ICAM-1 enhance the binding of I-domain to ICAM-1, suggesting it binds to ICAM-1 at different sites than the antibodies. The results indicate that fluorophore modification does not alter the binding and uptake properties of the I-domain protein. Thus, I-domain could be useful as a carrier of drug to target ICAM-1-expressing lymphocytes.

Temporal pattern of ICAM-I mediated regulatory T cell recruitment to sites of inflammation in adoptive transfer model of multiple sclerosis

Migration of immune cells to the target organ plays a key role in autoimmune disorders like multiple sclerosis (MS). However, the exact underlying mechanisms of this active process during autoimmune lesion pathogenesis remain elusive. To test if pro-inflammatory and regulatory T cells migrate via a similar molecular mechanism, we analyzed the expression of different adhesion molecules, as well as the composition of infiltrating T cells in an in vivo model of MS, adoptive transfer experimental autoimmune encephalomyelitis in rats. We found that the upregulation of ICAM-I and VCAM-I parallels the development of clinical disease onset, but persists on elevated levels also in the phase of clinical remission. However, the composition of infiltrating T cells found in the developing versus resolving lesion phase changed over time, containing increased numbers of regulatory T cells (FoxP3) only in the phase of clinical remission. In order to test the relevance of the expression of cell adhesion molecules, animals were treated with purified antibodies to ICAM-I and VCAM-I either in the phase of active disease or in early remission. Treatment with a blocking ICAM-I antibody in the phase of disease progression led to a milder disease course. However, administration during early clinical remission aggravates clinical symptoms. Treatment with anti-VCAM-I at different timepoints had no significant effect on the disease course. In summary, our results indicate that adhesion molecules are not only important for capture and migration of pro-inflammatory T cells into the central nervous system, but also permit access of anti-inflammatory cells, such as regulatory T cells. Therefore it is likely to assume that intervention at the blood brain barrier is time dependent and could result in different therapeutic outcomes depending on the phase of CNS lesion development.

Adhesion molecules are promising candidates to establish surrogate markers for natalizumab treatment

BACKGROUND

Natalizumab is the first monoclonal antibody therapy approved for multiple sclerosis (MS). Its therapeutic mechanism is the blockade of the α4-integrin subunit of the adhesion molecule (AM) very late activation antigen-4 (VLA-4), which leads to an inhibition of immune cell extravasation into the central nervous system (CNS).

METHODS

We investigated changes in the expression levels of unblocked α4-integrin and further AM (intercellular adhesion molecule-1, -2, -3 (cICAM-1, -2, -3), leukocyte function associated antigen-1 (LFA-1)) on peripheral blood mononuclear cells (PBMC) determined by flow cytometry from 25 patients with MS before the first natalizumab infusion and before the fourth infusion. In 15 MS patients AM expression was evaluated every 3 months over 1 year.

RESULTS

We found a significant decrease (p < 0.0001) of unblocked α4-integrin cell surface expression on all investigated PBMC subsets (T cells -61.7%, B cells -69.1%, monocytes/macrophages -46.4%) in the blood of MS patients after 3 months of natalizumab treatment. Moreover, a continuous decrease (p < 0.05) of unblocked α4-integrin expression levels was seen after 3, 6, 9, and 12 months. As a secondary effect, expression levels of the other investigated AM were differentially affected.

CONCLUSIONS

Results show a sustained decrease of unblocked α4-integrin expression not only in all patients but also in all investigated PBMC subsets. This probably results in a continuously decreasing transmigration of PBMC into the CNS and may explain the improved clinical efficacy in the second treatment year and also the increasing risk of progressive multifocal leukoencephalopathy during long-term natalizumab therapy. We conclude that AM expression profiles are promising candidates for the development of a biomarker system to determine both natalizumab treatment response and patients at risk for opportunistic CNS infections.

Diagnosis and treatment of multiple sclerosis in pediatric and adolescent patients: current status and future therapies

Pediatric-onset multiple sclerosis (MS) comprises approximately 3%-5% of cases of MS in North America. Recent years have seen significant advances in the diagnosis and treatment of this condition, including the introduction of proposed diagnostic criteria for pediatric demyelinating disorders, and a growing body of knowledge regarding treatment options. This article reviews current approaches to the diagnosis and management of pediatric MS.

Immune-mediated CNS damage

Multiple sclerosis (MS) is a demyelinating autoimmune disease. However, the persisting neurological deficits in MS patients result from acute axonal injury and chronic neurodegeneration, which are both triggered by the autoreactive immune response. Innate immunity, mainly mediated by activated microglial cells and invading macrophages, appears to contribute to chronic neurodegeneration. Activated microglia produce several reactive oxygen species and proinflammatory cytokines which affect neuronal function, integrity and survival. Adaptive immunity, particularly in cytotoxic CD8+ T cells, participates in acute demyelination and axonal injury by directly attacking oligodendrocytes and possibly neurons as well. Understanding the mechanisms of immune-mediated neuronal damage might help to design novel therapy strategies for MS.

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.

B cells and monocytes from patients with active multiple sclerosis exhibit increased surface expression of both HERV-H Env and HERV-W Env, accompanied by increased seroreactivity

Background

The etiology of the neurogenerative disease multiple sclerosis (MS) is unknown. The leading hypotheses suggest that MS is the result of exposure of genetically susceptible individuals to certain environmental factor(s). Herpesviruses and human endogenous retroviruses (HERVs) represent potentially important factors in MS development. Herpesviruses can activate HERVs, and HERVs are activated in MS patients.

Results

Using flow cytometry, we have analyzed HERV-H Env and HERV-W Env epitope expression on the surface of PBMCs from MS patients with active and stable disease, and from control individuals. We have also analyzed serum antibody levels to the expressed HERV-H and HERV-W Env epitopes. We found a significantly higher expression of HERV-H and HERV-W Env epitopes on B cells and monocytes from patients with active MS compared with patients with stable MS or control individuals. Furthermore, patients with active disease had relatively higher numbers of B cells in the PBMC population, and higher antibody reactivities towards HERV-H Env and HERV-W Env epitopes. The higher antibody reactivities in sera from patients with active MS correlate with the higher levels of HERV-H Env and HERV-W Env expression on B cells and monocytes. We did not find such correlations for stable MS patients or for controls.

Conclusion

These findings indicate that both HERV-H Env and HERV-W Env are expressed in higher quantities on the surface of B cells and monocytes in patients with active MS, and that the expression of these proteins may be associated with exacerbation of the disease.

Models of autoimmune demyelination in the central nervous system: on the way to translational medicine

Multiple sclerosis (MS) is the most common neurologic disease of young adults. In the recent years, our understanding on disease pathomechanisms has considerably improved and new therapies have emerged. Yet a cure for this devastating disorder is still a far cry away and human resources on ex vivo specimens are limited. More than 70 years after its first description, experimental autoimmune encephalomyelitis (EAE) remains an important tool to understand concepts of T cell mediated autoimmunity as well as the roles of the innate and the humoral immune systems. Some EAE models also well reflect mechanisms of tissue damage including demyelination, axonal injury and also cortical changes. A limitation of the classical EAE model is a neglect of CD8 T cell mediated immune mechanisms. Moreover, well characterized models for primary progressive MS or demyelination patterns involving primary oligodendrocyte dystrophy are still not available. Yet many current therapeutic concepts including glatiramer acetate or natalizumab stem from their successful first application in EAE models. New strategies include the widespread use of conditional knockout mice to understand the cell-type specific function of single genes, innovative approaches to establish models on the roles of B cells and CD8 T cells as well as on the relation of inflammation to primary degeneration. In summary, EAE models continue to play an important role in neuroimmunology thereby also stimulating research in other fields of the neurosciences and immunobiology.

Peripheral sensory axon growth: from receptor binding to cellular signaling

Regeneration following axonal injury of the adult peripheral sensory nervous system is heavily influenced by factors located in a neuron's extracellular environment. These factors include neurotrophins, such as Nerve Growth Factor (NGF) and the extracellular matrix, such as laminin. The presence of these molecules in the peripheral nervous system (PNS) is a major contributing factor for the dichotomy between regenerative capacities of central vs. peripheral neurons. Although PNS neurons are capable of spontaneous regeneration, this response is critically dependent on many different factors including the type, location and severity of the injury. In this article, we will focus on the plasticity of adult dorsal root ganglion (DRG) sensory neurons and how trophic factors and the extracellular environment stimulate the activation of intracellular signaling cascades that promote axonal growth in adult dorsal root ganglion neurons.

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.

Deletion of both ICAM-1 and C3 enhances severity of experimental autoimmune encephalomyelitis compared to C3-deficient mice

Multiple sclerosis (MS) is an autoimmune disease characterized by central nervous system (CNS) inflammation and leukocyte infiltration, demyelination of neurons, and blood-brain barrier breakdown. The development of experimental autoimmune encephalomyelitis (EAE), the animal model for MS is dependent on a number of components of the immune system including complement and adhesion molecules. Previous studies in our lab have examined the role of C3, the central complement component, and intercellular adhesion molecule-1 (ICAM-1) a key cell adhesion molecule involved in leukocyte trafficking to sites of inflammation including the CNS. In these studies we demonstrated that myelin oligodendrocyte glycoprotein (MOG)-induced EAE is markedly attenuated in both ICAM-1(-/-) and C3(-/-) mice. Given the pivotal role that these proteins play in EAE, we hypothesized that EAE in ICAM-1(-/-) and C3(-/-) double mutant mice would likely fail to develop. Unexpectedly, EAE in ICAM-1(-/-)xC3(-/-) mice was only modestly attenuated compared to wild type mice and significantly worse than C3(-/-) mice. Leukocyte infiltration was commensurate with disease severity between the three groups of mice. Spinal cord T cells from ICAM-1(-/-)xC3(-/-) mice produced the highest levels of IFN-gamma and TNF-alpha, despite reduced disease severity compared to wild type mice. The mechanisms behind the elevated EAE severity in ICAM-1(-/-)xC3(-/-) mice may relate to altered homing of leukocytes or processing of self-antigens in the double mutant background.

Celecoxib modulates adhesion of HT29 colon cancer cells to vascular endothelial cells by inhibiting ICAM-1 and VCAM-1 expression

BACKGROUND AND PURPOSE

Cyclooxygenase-2 (COX-2) is highly expressed during inflammation and can promote the progression of colorectal cancer. Interactions between cancer cells and vascular endothelial cells are key events in this process. Recently, the selective COX-2 inhibitor, celecoxib, was shown to inhibit expression of the adhesion molecules, ICAM-1 and VCAM-1, in the human colon cancer cell line HT29 and to inhibit adhesion of HT29 cells to FCS-coated plastic wells. Here, we evaluated the effects of celecoxib on adhesion of HT29 cells to human umbilical vein endothelial cells (HUVEC), mediated by ICAM-1 and VCAM-1, to assess further the potential protective effects of celecoxib on cancer development.

EXPERIMENTAL APPROACH

Celecoxib was incubated for 4 h with HT29 cells and HUVEC and adhesion was quantified by a computerized micro-imaging system. Expression analysis of ICAM-1 and VCAM-1 cell adhesion molecules was performed by western blot.

KEY RESULTS

Celecoxib (1 nM-10 microM) inhibited, with the same potency, adhesion of HT29 cells to resting HUVEC or to HUVEC stimulated by tumour necrosis factor-alpha (TNF-alpha), mimicking inflammatory conditions. Analysis of ICAM-1 and VCAM-1 expression showed that celecoxib inhibited expression of both molecules in TNF-alpha-stimulated HUVEC, but not in resting HUVEC; inhibition was concentration-dependent and maximal (about 50%) at 10 microM celecoxib.

CONCLUSIONS AND IMPLICATIONS

In conclusion, our data show that celecoxib inhibits HT29 cell adhesion to HUVEC and expression of ICAM-1 and VCAM-1, in stimulated endothelial cells. These effects may contribute to the chemopreventive activity of celecoxib in the development of colorectal cancer.

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.

Oral disease-modifying treatments for multiple sclerosis: the story so far

Multiple sclerosis (MS) represents the prototypic inflammatory autoimmune disorder of the CNS. It is the most common cause of neurological disability in young adults and exhibits considerable clinical, radiological and pathological heterogeneity. Increased understanding of the immunopathological processes underlying this disease, advances in biotechnology and the development of powerful magnetic resonance imaging (MRI) technologies, together with improvements in clinical trial design, have led to a variety of valuable therapeutic approaches to MS. Therapy for MS has changed dramatically over the past decade, yielding significant progress in the treatment of relapsing remitting and secondary progressive forms; however, most of the clinically relevant therapeutic approaches are not yet available as oral formulations. A substantial number of preliminary and pivotal reports have provided promising results for oral therapies, and various phase III clinical trials are currently being initiated or are already underway evaluating the efficacy of a variety of orally administered agents, including cladribine, teriflunomide, laquinimod, fingolimod and fumaric acid. It is hoped that these trials will advance the development of oral therapies for MS.

The blood-brain-barrier in multiple sclerosis: functional roles and therapeutic targeting

In most regions of the central nervous system (CNS), the composition of the neuronal microenvironment is maintained by virtue of particular blood-brain-barrier (BBB) characteristics, to which vascular endothelial cells (ECs) contribute an important role. Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS, characterized at tissue level by multifocal perivascular infiltrates, predominantly of lymphocytes and macrophages. Thus, lymphocyte recruitment into the brain across ECs of the BBB represents a critical event in disease pathogenesis, which is highly restricted and carefully regulated. In recent years, different investigations have identified the crucial components involved in leukocyte migration, providing new insights into mechanisms modulating neuroinflammatory reactions. In this review, several topics relating to these events are discussed, namely: (1) cellular and molecular characteristics of the BBB regulating permeability, as well as signals inducing EC differentiation in the brain and specific cell properties; (2) pathogenic mechanisms guiding the migration of different leukocyte populations through the BBB in MS; and (3) current knowledge on how different MS therapies targeting leukocytes migration across the BBB function. Furthermore, because the BBB has proven to be an important retaining wall preventing drug passage into the CNS, novel strategies directed at successful delivery of large molecules for effective treatment of various inflammatory conditions of the brain, both currently available or still under development, are discussed.

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.

TNFR1-induced NF-kappaB, but not ERK, p38MAPK or JNK activation, mediates TNF-induced ICAM-1 and VCAM-1 expression on endothelial cells

Tumour necrosis factor (TNF) is a pro-inflammatory cytokine, whose primary targets include vascular endothelial cells. TNF-mediated adhesion molecule expression has been shown to play a central role in endothelial cells inflammatory responses and disorders such as atherosclerosis. However it is not fully understand how the TNF receptor subtypes, namely TNFR1 and TNFR2, regulate inflammatory responses in endothelial cells. The aim of this study was to elucidate the kinase signalling pathways that TNF receptors activate, and determine the pathways responsible for downstream expression of adhesion molecules, intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human endothelial cells. Using human umbilical vein endothelial cells (HUVEC), we demonstrated that TNF activates a range of mitogen-activated protein kinases (MAPKs), including the extracellular-regulated kinase (ERK) pathway and the p38MAPK and c-Jun N-terminal kinase (JNK) stress kinase pathways. Human endothelial cells express both TNF receptor subtypes at low levels, however using TNFR-specific agonistic agents, we uncovered that TNF acts through its TNFR1 receptor subtype to activate NF-kappaB transcriptional pathways. Further investigation revealed that ICAM-1 and VCAM-1 mRNA and protein are induced by TNFR1 (but not TNFR2) in a wholly NF-kappaB-dependent manner. These findings reveal for the first time that TNF stimulation of adhesion molecules ICAM-1 and VCAM-1 in human endothelial cells occurs through the TNFR1 subtype and is mediated by the NF-kappaB pathway, but not the ERK, p38MAPK or JNK kinase pathways.

Mechanisms of immune regulation in the peripheral nervous system

The peripheral nervous system (PNS) is a target for heterogenous immune attacks mediated by different components of the systemic immune compartment. T cells, B cells, and macrophages can interact with endogenous, partially immune-competent glial cells and contribute to local inflammation. Cellular and humoral immune functions of Schwann cells have been well characterized in vitro. In addition, the interaction of the humoral and cellular immune system with the cellular and extracellular components in the PNS may determine the extent of tissue inflammation and repair processes such as remyelination and neuronal outgrowth. The animal model experimental autoimmune neuritis (EAN) allows direct monitoring of these immune responses in vivo. In EAN contributions to regulate autoimmunity in the PNS are made by adhesion molecules and by cytokines that orchestrate cellular interactions. The PNS has a significant potential to eliminate T cell inflammation via apoptosis, which is almost lacking in other tissues such as muscle and skin. In vitro experiments suggest different scenarios how specific cellular and humoral elements in the PNS may sensitize autoreactive T cells for apoptosis in vivo. Interestingly several conventional and novel immunotherapeutic approaches like glucocorticosteroids and high-dose antigen therapy induce T cell apoptosis in situ in EAN. A better understanding of immune regulation and its failure in the PNS may help to develop improved, more specific immunotherapies.

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.

Activation of cerebral endothelium is required for mononuclear cell recruitment in a novel in vitro model of brain inflammation

Brain inflammation is a common event in the pathogenesis of several neurological diseases. It is unknown whether leukocyte/endothelium interactions are sufficient to promote homing of blood-borne cells into the brain compartment. The role of mononuclear cells and endothelium was analyzed in a new experimental model, the isolated guinea-pig brain maintained in vitro by arterial perfusion. This preparation allows one to investigate early steps of brain inflammation that are impracticable in vivo. We demonstrate by confocal microscopy analysis that in vitro co-perfusion of pro-inflammatory agents and pre-activated fluorescent mononuclear cells induced endothelial expression of selectins and intracellular adhesion molecule-1 in correspondence of arrested mononuclear cells, and correlates with a moderate increase in blood-brain barrier permeability. Separate perfusion of pro-inflammatory agents and mononuclear cells induced neither mononuclear cell adhesion nor adhesion molecule expression. We demonstrate that co-activation of mononuclear cells and cerebral endothelium is an essential requirement for cell arrest and adhesion in the early stages of experimental cerebral inflammation.

In vivo molecular imaging of adhesion molecules in experimental autoimmune encephalomyelitis (EAE)

The infiltration of autoreactive T cells into the central nervous system (CNS) requires a complex molecular interplay between immune cells and the blood-brain barrier (BBB), especially involving adhesion molecules like intercellular adhesion molecule (ICAM)-1. Here we study the molecular expression at the BBB during adoptively transferred (AT) myelin basic protein (MBP)-experimental autoimmune encephalomyelitis (EAE) in vivo by sensitive particle acoustic quantification (SPAQ)-enhanced ultrasound after intravenous application of specific gas-filled MP (MP) targeted against ICAM-1 (ICAM-MP) as contrast agent. Our results reveal a clear periventricular and cerebellar upregulation of ICAM-1 expression at the disease maximum of AT-EAE. Moreover, SPAQ-enhanced ultrasound enables the sensitive quantification of ICAM-1 expression in vivo. This allows to monitor therapeutic changes as shown by suppression of ICAM-1 expression after pretreatment of rats with corticosteroids (P < 0.008). All imaging results were confirmed by parallel immunohistochemistry. In vivo magnetic resonance imaging and albumin staining of rat brains after sonification did not reveal a disturbance of the BBB, thereby proving the safety of the method. Subsequent application of specific MP did not influence follow-up measurements, a prerequisite for sequential measurements in longitudinal studies. Based on these data, quantitative molecular imaging of adhesion molecules by SPAQ-enhanced ultrasound proves to be a safe and reliable technology to monitor changes at the BBB in vivo.

Natalizumab for the treatment of multiple sclerosis and Crohn's disease

OBJECTIVE

To review the pharmacology, pharmacokinetics, safety, and pivotal clinical trials for natalizumab in the treatment of multiple sclerosis (MS) and inflammatory bowel disease.

DATA SOURCES

A PubMed/MEDLINE search was conducted (1966-June 2005), and information was obtained from Iowa Drug Information Services. Additional data sources included meeting abstracts, bibliographies from identified articles, and information from the manufacturer.

STUDY SELECTION AND DATA EXTRACTION

Studies and review articles examining natalizumab were evaluated. All published, randomized clinical trials evaluating natalizumab in MS and IBD were included in this review.

DATA SYNTHESIS

Natalizumab is the first drug in a new class of agents called selective adhesion molecule inhibitors. It has shown promising results in MS and inflammatory bowel disease and appears superior compared with current therapies in reducing relapse rates. However, 3 recent, confirmed case reports of progressive multifocal leukoencephalopathy (PML) create concern about natalizumab's use in combination with existing therapies or in undefined patient subgroups. Natalizumab was voluntarily withdrawn from the market in March 2005 while the drug's safety is further evaluated.

CONCLUSIONS

Although long-term efficacy and safety of natalizumab have not been established, available data indicate that it is a novel drug for patients with MS or inflammatory bowel disease. Analysis of its possible association with PML will determine the risk-benefit evaluation and eventual place in therapy for natalizumab.

PSGL-1 is not required for development of experimental autoimmune encephalomyelitis

Adhesion molecules are essential mediators for lymphocyte trafficking through the blood-brain barrier into the CNS in multiple sclerosis and its animal model experimental autoimmune encephalomyelitis (EAE). However, the role of the selectin molecules and their ligand, P-selectin glycoprotein-1 (PSGL-1) which mediates tethering and rolling of the leukocytes in demyelinating disease remains controversial. This study demonstrates that mice deficient in PSGL-1 are not significantly different in the development and progression of EAE compared to wild type controls. Our observations suggest that PSGL-1-selectin interactions are redundant and not required for the development of EAE. Our data also indicate that other adhesion molecules are necessary for the initial rolling events leading to leukocyte infiltration into the CNS during EAE.

Ultrasound derived imaging and quantification of cell adhesion molecules in experimental autoimmune encephalomyelitis (EAE) by Sensitive Particle Acoustic Quantification (SPAQ)

Molecular imaging requires, not only the identification of an appropriate marker, but also its quantitative analysis. We used the Sensitive Particle Acoustic Quantification (SPAQ) technology - a novel ultrasound technique - for detection and quantification of cell adhesion molecules in isolated tissue and in live animals. By conjugating gas-filled microparticles (MPs) with antibodies to intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), we were able to depict and quantify ICAM-1 and VCAM-1 in isolated brain and spinal cord from rats with autoimmune encephalomyelitis (EAE), an established inflammatory disease model of human multiple sclerosis (MS). Depiction and quantification of specific MPs were also feasible in living animals with AT-EAE with similar results. After treatment with methylprednisolone, the measured number of targeted anti-ICAM-1 and VCAM-1-MPs was significantly lower (P<0.01) compared to untreated animals demonstrating the high sensitivity of this imaging technique. Depending on the antibody linked to the surface of the MPs, the technique can be used to quantify the expression of any accessible antigen expressed on the luminal surface of endothelial cells and is therefore a promising tool for the non-invasive and dynamic assessment of disease-related molecules.