A novel HLA-DRα1-MOG-35-55 construct treats experimental stroke

The CD74 inhibitor DRhQ improves short-term memory and mitochondrial function in 5xFAD mouse model of Aβ accumulation

Neuroinflammation and mitochondrial dysfunction are early events in Alzheimer's disease (AD) and contribute to neurodegeneration and cognitive impairment. Evidence suggests that the inflammatory axis mediated by macrophage migration inhibitory factor (MIF) binding to its receptor, CD74, plays an important role in many central nervous system (CNS) disorders such as AD. Our group has developed DRhQ, a novel CD74 binding construct which competitively inhibits MIF binding, blocks macrophage activation and migration into the CNS, enhances anti-inflammatory microglia cell numbers and reduces pro-inflammatory gene expression. Here, we evaluate its effects in amyloid-β (Aβ) overexpressing mice. 5xFAD mice and their wild type littermates were treated with DRhQ (100 µg) or vehicle for 4 weeks. DRhQ improved cognition and cortical mitochondrial function in both male and female 5xFAD mice. Aβ plaque burden in 5xFAD animals was not robustly impacted by DRhQ treatment in either the hippocampus or the cortex. Cortical microglial activation was similarly not apparently affected by DRhQ treatment, although in the hippocampus there was evidence of a reduction in activated microglia for female 5xFAD mice. Future studies are needed to confirm this possible sex-dependent response on microglial activation, as well as to optimize the dose and timing of DRhQ treatment and gain a better understanding of its mechanism of action in AD.

The unsolved mystery of hippocampal cholinergic neurostimulating peptide: A potent cholinergic regulator

Cholinergic efferent networks located from the medial septal nucleus to the hippocampus play a pivotal role in learning and memory outcomes by generating regular theta rhythms that enhance information retention. Hippocampal cholinergic neurostimulating peptide (HCNP), derived from the N-terminus of HCNP precursor protein (HCNP-pp), promotes the synthesis of acetylcholine in the medial septal nuclei. HCNP-pp deletion significantly reduced theta power in CA1 possibly due to lower levels of choline acetyltransferase-positive axons in CA1 stratum oriens, suggesting cholinergic disruptions in the septo-hippocampal system. This review also explores HCNP as a potent cholinergic regulator in the septo-hippocampal network while also examining the limitations of our understanding of the neurostimulating peptide.

Major histocompatibility complex Class II-based therapy for stroke

This review discusses the potential of major histocompatibility complex (MHC) Class II constructs as stroke therapeutics. We focus on the delivery of MHC Class II construct, DRmQ, as a safe and effective treatment for ischemic stroke. DRmQ was observed to attenuate behavioral deficits and decrease microglia activation and proinflammatory cytokines, illustrating its ability to mitigate the secondary cell death following stroke. Similar anti-neuroinflammation treatments, such as transplantation of mesenchymal stem cells and mitochondrial transfers, are briefly discussed to provide further support that sequestration of inflammation stands as a robust therapeutic target for stroke.

A Novel Partial MHC Class II Construct, DRmQ, Inhibits Central and Peripheral Inflammatory Responses to Promote Neuroprotection in Experimental Stroke

Recognizing that the pathologic progression of stroke is closely associated with aberrant immune responses, in particular the activation of peripheral leukocytes, namely T cells, we hypothesized that finding a treatment designed to inhibit neuroantigen-specific T cells and block cytotoxic monocytes and macrophages may render therapeutic effects in stroke. We previously reported that subcutaneous administration of partial MHC class II constructs promote behavioral and histological effects in stroke mice by centrally promoting a protective M2 macrophage/microglia phenotype in the CNS and peripherally reversing stroke-associated splenic atrophy. Here, we employed a second species using adult Sprague-Dawley rats exposed to the middle cerebral artery occlusion stroke model and observed similar therapeutic effects with a mouse partial MHC class II construct called DRmQ, as evidenced by reductions in stroke-induced motor deficits, infarcts, and peri-infarct cell loss and neuroinflammation. More importantly, we offered further evidence of peripheral sequestration of inflammation at the level of the spleen, which was characterized by attenuation of stroke-induced spleen weight reduction and TNF-ɑ and IL-6 upregulation. Collectively, these results satisfy the Stroke Therapy Academic Industry Roundtable criteria of testing a novel therapeutic in a second species and support the use of partial MHC class II constructs as a stroke therapeutic designed to sequester both central and peripheral inflammation responses in an effort to retard, or even halt, the neuroinflammation that exacerbates the secondary cell death in stroke.

Spleen participation in partial MHC class II construct neuroprotection in stroke

Pathological progression of stroke in the peripheral and central nervous systems (PNS and CNS) is characterized by multiple converging signalling pathways that exacerbate neuroinflammation-mediated secondary cell death. This creates a need for a novel type of immunotherapy capable of simultaneously lowering the synergistic inflammatory responses in the PNS and CNS, specifically the spleen and brain. Previously, we demonstrated that partial major histocompatibility complex (MHC) class II constructs can be administered subcutaneously to promote histological and behavioural effects that alleviate common symptoms found in a murine model of transient stroke. This MHC class II manipulates T cell cytokine expression in both PNS and CNS, resulting in dampened inflammation. In our long-standing efforts towards translational research, we recently demonstrated that a potent next generation mouse-based partial MHC class II construct named DRmQ (DRa1_L50Q -mMOG-35-55) similarly induces neuroprotection in stroke rats, replicating the therapeutic effects of the human homolog as DRhQ (DRa1_L50Q -human (h)MOG-35-55) in stroke mice. Our preclinical studies showed that DRmQ reduces motor deficits, infarct volume and peri-infarct cell loss by targeting inflammation in this second species. Moreover, we provided mechanistic support in both animal studies that partial MHC class II constructs effectively modulate the spleen, an organ which plays a critical role in modulating secondary cell death. Together, these preclinical studies satisfy testing the constructs in two stroke models, which is a major criterion of the Stroke Therapy Academic Industry Roundtable (STAIR) criteria and a key step in effectively translating this drug to the clinic. Additional translational studies, including dose-response and larger animal models may be warranted to bring MHC class II constructs closer to the clinic.

A novel neurotherapeutic for multiple sclerosis, ischemic injury, methamphetamine addiction, and traumatic brain injury

Neurovascular, autoimmune, and traumatic injuries of the central nervous system (CNS) all have in common an initial acute inflammatory response mediated by influx across the blood-brain barrier of activated mononuclear cells followed by chronic and often progressive disability. Although some anti-inflammatory therapies can reduce cellular infiltration into the initial lesions, there are essentially no effective treatments for the progressive phase. We here review the successful treatment of animal models for four separate neuroinflammatory and neurodegenerative CNS conditions using a single partial MHC class II construct called DRa1-hMOG-35-55 or its newest iteration, DRa1(L50Q)-hMOG-35-55 (DRhQ) that can be administered without a need for class II tissue type matching due to the conserved DRα1 moiety of the drug. These constructs antagonize the cognate TCR and bind with high affinity to their cell-bound CD74 receptor on macrophages and dendritic cells, thereby competitively inhibiting downstream signaling and pro-inflammatory effects of macrophage migration inhibitory factor (MIF) and its homolog, d-dopachrome tautomerase (D-DT=MIF-2) that bind to identical residues of CD74 leading to progressive disease. These effects suggest the existence of a common pathogenic mechanism involving a chemokine-driven influx of activated monocytes into the CNS tissue that can be reversed by parenteral injection of the DRa1-MOG-35-55 constructs that also induce anti-inflammatory macrophages and microglia within the CNS. Due to their ability to block this common pathway, these novel drugs appear to be prime candidates for therapy of a wide range of neuroinflammatory and neurodegenerative CNS conditions.

Genome-wide Integration Study of Circulating miRNAs and Peripheral Whole-Blood mRNAs of Male Acute Ischemic Stroke Patients

Several circulating microRNAs (miRNAs) have been proved to serve as stable biomarkers in blood for acute ischemic stroke (AIS). However, the functions of these biomarkers remain elusive. By conducting the integration analysis of circulating miRNAs and peripheral whole-blood mRNAs using bioinformatics methods, we explored the biological role of these circulating markers in peripheral whole blood at the genome-wide level. Stroke-related circulating miRNA profile data (GSE86291) and peripheral whole-blood mRNA expression data (GSE16561) were collected from the Gene Expression Omnibus (GEO) datasets. We selected male patients to avoid any gender differences in stroke pathology. Male stroke-related miRNAs (M-miRNAs) and mRNAs (M-mRNAs) were detected using GEO2R. Nine M-miRNAs (five up- and four down-regulated) were applied to TargetScan to predict the possible target mRNAs. Next, we intersected these targets with the M-mRNAs (38 up- and three down-regulated) to obtain the male stroke-related overlapped mRNAs (Mo-mRNAs). Finally, we analyzed biological functions of Mo-mRNAs using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), and constructed networks among the Mo-mRNAs, overlapped M-miRNAs (Mo-miRNAs), and their functions. The Mo-mRNAs were enriched in functions such as platelet degranulation, immune response, and pathways associated with phagosome biology and Staphylococcus aureus infection. This study provides an integrated view of interactions among circulating miRNAs and peripheral whole-blood mRNAs involved in the pathophysiological processes of male AIS.

Sex differences in the immune response to experimental stroke: Implications for translational research

Ischemic stroke is a leading cause of death and disability in the United States. It is known that males and females respond differently to stroke. Depending on age, the incidence, prevalence, mortality rate, and disability outcome of stroke differ between the sexes. Females generally have strokes at older ages than males and, therefore, have a worse stroke outcome. There are also major differences in how the sexes respond to stroke at the cellular level. Immune response is a critical factor in determining the progress of neurodegeneration after stroke and is fundamentally different for males and females. Additionally, females respond to stroke therapies differently from males, yet they are often left out of the basic research that is focused on developing those therapies. With a resounding failure to translate stroke therapies from the bench to the bedside, it is clearer than ever that inclusion of both sexes in stroke studies is essential for future clinical success. This Mini-Review examines sex differences in the immune response to experimental stroke and its implications for therapy development. © 2016 Wiley Periodicals, Inc.

DRα1-MOG-35-55 treatment reduces lesion volumes and improves neurological deficits after traumatic brain injury

Traumatic brain injury (TBI) results in severe neurological impairments without effective treatments. Inflammation appears to be an important contributor to key pathogenic events such as secondary brain injury following TBI and therefore serves as a promising target for novel therapies. We have recently demonstrated the ability of a molecular construct comprised of the human leukocyte antigen (HLA)-DRα1 domain linked covalently to mouse (m)MOG-35-55 peptide (DRα1-MOG-35-55 construct) to reduce CNS inflammation and tissue injury in animal models of multiple sclerosis and ischemic stroke. The aim of the current study was to determine if DRα1-MOG-35-55 treatment of a fluid percussion injury (FPI) mouse model of TBI could reduce the lesion size and improve disease outcome measures. Neurodeficits, lesion size, and immune responses were determined to evaluate the therapeutic potential and mechanisms of neuroprotection induced by DRα1-MOG-35-55 treatment. The results demonstrated that daily injections of DRα1-MOG-35-55 given after FPI significantly reduced numbers of infiltrating CD74⁺ and CD86⁺ macrophages and increased numbers of CD206⁺ microglia in the brain concomitant with smaller lesion sizes and improvement in neurodeficits. Conversely, DRα1-MOG-35-55 treatment of TBI increased numbers of circulating CD11b⁺ monocytes and their expression of CD74 but had no detectable effect on cell numbers or marker expression in the spleen. These results demonstrate that DRα1-MOG-35-55 therapy can reduce CNS inflammation and significantly improve histological and clinical outcomes after TBI. Future studies will further examine the potential of DRα1-MOG-35-55 for treatment of TBI.

Sex-dependent treatment of chronic EAE with partial MHC class II constructs

Background

One of the main challenges in treating multiple sclerosis (MS) is reversing the effects of accumulated damage in the central nervous system (CNS) of progressive MS subjects. While most of the available drugs for MS subjects are anti-inflammatory and thus are limited to relapsing-remitting MS subjects, it is not clear to what extent their effects are capable of inducing axonal repair and remyelination in subjects with chronic MS.

Methods

A chronic model of experimental autoimmune encephalomyelitis (EAE) was used to evaluate the potency of partial MHC (pMHC) class II constructs in treating progressive EAE.

Results

We demonstrated an estrogen receptor alpha (ERα)-dependent increased dose requirement for effective treatment of female vs. male mice using pMHC. Such treatment using 100-μg doses of RTL342M or DRα1-mMOG-35-55 constructs significantly reversed clinical severity and showed a clear trend for inhibiting ongoing CNS damage, demyelination, and infiltration of inflammatory cells into the CNS in male mice. In contrast, WT female mice required larger 1-mg doses for effective treatment, although lower 100-μg doses were effective in ovariectomized or ERα-deficient mice with EAE.

Conclusions

These findings will assist in the design of future clinical trials using pMHC for treatment of progressive MS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0873-y) contains supplementary material, which is available to authorized users.

DRα1-MOG-35-55 Reduces Permanent Ischemic Brain Injury

Stroke induces a catastrophic immune response that involves the global activation of peripheral leukocytes, especially T cells. The human leukocyte antigen-DRα1 domain linked to MOG-35-55 peptide (DRα1-MOG-35-55) is a partial major histocompatibility complex (MHC) class II construct which can inhibit neuroantigen-specific T cells and block binding of the cytokine/chemokine macrophage migration inhibitory factor (MIF) to its CD74 receptor on monocytes and macrophages. Here, we evaluated the therapeutic effect of DRα1-MOG-35-55 in a mouse model of permanent distal middle cerebral artery occlusion (dMCAO). DRα1-MOG-35-55 was administered to WT C57BL/6 mice by subcutaneous injection starting 4 h after the onset of ischemia followed by three daily injections. We demonstrated that DRα1-MOG-35-55 post treatment significantly reduced brain infarct volume, improved functional outcomes, and inhibited the accumulation of CD4⁺ and CD8⁺ T cells and expression of pro-inflammatory cytokines in the ischemic brain 96 h after dMCAO. In addition, DRα1-MOG-35-55 treatment shifted microglia/macrophages in the ischemic brain to a beneficial M2 phenotype without changing their total numbers in the brain or blood. This study demonstrates for the first time the therapeutic efficacy of the DRα1-MOG-35-55 construct in dMCAO across MHC class II barriers in C57BL/6 mice. This MHC-independent effect obviates the need for tissue typing and will thus greatly expedite treatment with DRα1-MOG-35-55 in human stroke subjects. Taken together, our findings suggest that DRα1-MOG-35-55 treatment may reduce ischemic brain injury by regulating post-stroke immune responses in the brain and the periphery.

Upregulation of CD74 and its potential association with disease severity in subjects with ischemic stroke

Macrophage migration inhibitory factor (MIF) is a key cytokine/chemokine in the activation and recruitment of inflammatory T lymphocytes known to exacerbate experimental stroke severity. MIF effects are mediated through its primary cellular receptor, CD74, the MHC class II invariant chain present on all class II expressing cells, including monocytes, macrophages and dendritic cells (DC). We demonstrated previously that partial MHC class II/peptide constructs (pMHC) can effectively treat mice with experimental stroke, in part through their ability to competitively inhibit MIF/CD74 interactions and downstream signaling. However, the role of MIF and CD74 in human ischemic stroke is not yet well established. To evaluate the therapeutic potential for pMHC, we assessed MIF and CD74 expression levels and their association with disease outcome in subjects with ischemic stroke. MIF levels were assessed in blood plasma by ELISA and CD74 expression was quantified by flow cytometry and qRT-PCR in peripheral blood mononuclear cells (PBMCs) obtained from subjects with ischemic stroke and age and sex-matched healthy controls (HC). MIF levels were increased in plasma and the number of CD74⁺ cells and CD74 mRNA expression levels were significantly increased in PBMC of subjects with ischemic stroke versus HC, mainly on CD4⁺ T cells, monocytes and DC. Greater increases of CD74⁺ cells were seen in subjects with cortical vs. subcortical infarcts and the number of CD74⁺ cells in blood correlated strongly with infarct size and neurological outcomes. However, differences in MIF and CD74 expression were not affected by age, gender or lesion laterality. Increased CD74 expression levels may serve as a useful biomarker for worse stroke severity and predicted outcomes in subjects with ischemic stroke and provide a rationale for potential future treatment with pMHC constructs.

Partial MHC class II constructs as novel immunomodulatory therapy for stroke

The worldwide prevalence of stroke continues to rise despite recent successes in treating acute ischemic stroke. With limited patient eligibility and associated risk of tPA and mechanical thrombectomy, new preventive and therapeutic modalities are needed to stave the rising wave of stroke. Inflammation plays a key role in brain damage after cerebral ischemia, and novel therapies that target pro-inflammatory cells have demonstrated promise for treatment for stroke. Partial MHC class II constructs have been shown to prevent and/or reverse clinical signs of various inflammatory diseases such as experimental autoimmune encephalomyelitis, collagen-induced arthritis and experimental autoimmune uveitis, by reducing the number and frequency of activated cells in the damaged CNS. Herein, we review the use of partial MHC class II constructs as a novel treatment for ischemic stroke. These constructs have been shown to reduce infarct volume and neurological deficit in various cerebral ischemia models in young adult and aging male and female mice. In addition, partial MHC class II constructs were shown to reverse stroke-associated splenic atrophy and promote a protective M2 macrophage/microglia phenotype in the CNS which contributes to tissue repair and recovery after stroke. By addressing remaining STAIR criteria, such as efficacy in large animal models of stroke, these constructs will be prime candidates for clinical trials of acute ischemic stroke.

Solution-Phase Crosstalk and Regulatory Interactions Between Multipotent Adult Progenitor Cells and Peripheral Blood Mononuclear Cells

Multipotent adult progenitor cells (MAPCs) are adult adherent stromal stem cells currently being assessed in clinical trials for acute graft versus host disease with demonstrated immunomodulatory capabilities and the potential to ameliorate detrimental autoimmune and inflammation-related processes. Anti-CD3/anti-CD28 (3/28) activation of T cells within the peripheral blood mononuclear cell (PBMC) compartment was performed in the presence or absence of MAPCs. Liquid chromatography-coupled tandem mass spectrometry was used to characterize the differential secretion of proteins, and transcriptional profiling was used to monitor mRNA expression changes in both cell populations. Overall, 239 secreted and/or ectodomain-shed proteins were detected in the secretomes of PBMCs and MAPCs. In addition, 3/28 activation of PBMCs induced differential expression of 2,925 genes, and 22% of these transcripts were differentially expressed on exposure to MAPCs in Transwell. MAPCs exposed to 3/28-activated PBMCs showed differential expression of 1,247 MAPC genes. Crosstalk was demonstrated by reciprocal transcriptional regulation. Secretome proteins and transcriptional signatures were used to predict molecular activities by which MAPCs could dampen local and systemic inflammatory responses. These data support the hypothesis that MAPCs block PBMC proliferation via cell cycle arrest coupled to metabolic stress in the form of tryptophan depletion, resulting in GCN2 kinase activation, downstream signaling, and inhibition of cyclin D1 translation. These data also provide a plausible explanation for the immune privilege reported with administration of donor MAPCs. Although most components of the major histocompatibility complex class II antigen presentation pathway were markedly transcriptionally upregulated, cell surface expression of human leukocyte antigen-DR is minimal on MAPCs exposed to 3/28-activated PBMCs.

SIGNIFICANCE

This study documents experiments quantifying solution-phase crosstalk between multipotent adult progenitor cells (MAPCs) and peripheral blood mononuclear cells. The secretome and transcriptional changes quantified suggest mechanisms by which MAPCs are hypothesized to provide both local and systemic immunoregulation of inflammation. The potential impact of these studies includes development of a robust experimental framework to be used for preclinical evaluation of the specific mechanisms by which beneficial effects are obtained after treatment of patients with MAPCs.

Partial MHC Constructs Treat Thromboembolic Ischemic Stroke Characterized by Early Immune Expansion

Inflammation and thrombosis are tightly linked, with inflammation contributing to thromboembolism and to stroke outcome. Thromboembolism is a frequent cause of ischemic stroke; yet, the most used occlusion mouse models of experimental stroke do not effectively replicate thromboembolism. Our group recently described a novel thromboembolic mouse model of stroke that successfully occludes the middle cerebral artery with high reproducibility. In the current study, we characterize the peripheral and local immune outcomes as well as the ischemic response to immune therapy in a clinically relevant mouse model of thromboembolic stroke. Brain and spleen tissues were harvested 24 h after thromboembolic stroke and cells immunophenotyped by flow cytometry. We observed a significant increase in neutrophils and early activated T cells in the spleen and an increase in neutrophils and activated monocytes/microglia in the ischemic cortex after thromboembolic stroke. Moreover, as was shown previously for transient MCAO models, treatment of thromboembolic stroke with partial MHC constructs significantly reduced ischemic damage indicating an equivalent effect of this immune-based therapy in the thromboembolic model that better mimics the pathophysiology of human stroke.

Dynamics of T cell responses after stroke

T cells are integral to the pathophysiology of stroke. The initial inflammatory cascade leads to T cell migration, which results in deleterious and protective effects mediated through CD4(+), CD(8)+, γδ T cells and regulatory T cells, respectively. Cytokines are central to the T cell responses, with key roles established for TNF-α, IFN-γ, IL-17, IL-21 and IL-10. Through communication with the systemic immune system via neural and hormonal pathways, there is also transient immunosuppression after severe strokes. With time, the inflammatory process eventually transforms to one more conducive of repair and recovery, though some evidence also suggests ongoing chronic inflammation. The role of antigen-specific T cell responses requires further investigation. As our understanding develops, there is increasing scope to modulate the T cell response after stroke.

The use of flow cytometry to assess a novel drug efficacy in multiple sclerosis

Applying different technologies to monitor disease activity and treatment efficacy are essential in a complex disease such as multiple sclerosis. Combining current assays with flow cytometry could create a powerful tool for such analyses. The cell surface expression level of CD74, the MHC class II invariant chain, is a potential disease biomarker that could be monitored by FACS analysis in order to assess disease progression and the clinical efficacy of partial MHC class II constructs in treating MS. These constructs, which can bind to and down-regulate CD74 cell-surface expression on monocytes and inhibit macrophage migration inhibitory factor (MIF) effects, can reverse clinical and histological signs of EAE. These properties of partial class II constructs are highly compatible with a flow cytometry approach for monitoring CD74 expression as a possible biomarker for disease activity/progression and as a treatment response marker.

HLA-DRα1-mMOG-35-55 treatment of experimental autoimmune encephalomyelitis reduces CNS inflammation, enhances M2 macrophage frequency, and promotes neuroprotection

Background

DRα1-mouse(m)MOG-35-55, a novel construct developed in our laboratory as a simpler and potentially less immunogenic alternative to two-domain class II constructs, was shown previously to target the MIF/CD74 pathway and to reverse clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in DR*1501-Tg mice in a manner similar to the parent DR2β1-containing construct.

Methods

In order to determine whether DRα1-mMOG-35-55 could treat EAE in major histocompatibility complex (MHC)-mismatched mice and to evaluate the treatment effect on central nervous system (CNS) inflammation, C57BL/6 mice were treated with DRα1-mMOG-35-55. In addition, gene expression profile was analyzed in spinal cords of EAE DR*1501-Tg mice that were treated with DRα1-mMOG-35-55.

Results

We here demonstrate that DRα1-mMOG-35-55 could effectively treat EAE in MHC-mismatched C57BL/6 mice by reducing CNS inflammation, potentially mediated in part through an increased frequency of M2 monocytes in the spinal cord. Microarray analysis of spinal cord tissue from DRα1-mMOG-35-55-treated vs. vehicle control mice with EAE revealed decreased expression of a large number of pro-inflammatory genes including CD74, NLRP3, and IL-1β and increased expression of genes involved in myelin repair (MBP) and neuroregeneration (HUWE1).

Conclusion

These findings indicate that the DRα1-mMOG-35-55 construct retains therapeutic, anti-inflammatory, and neuroprotective activities during treatment of EAE across MHC disparate barriers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0342-4) contains supplementary material, which is available to authorized users.

Thrombin mutant W215A/E217A treatment improves neurological outcome and attenuates central nervous system damage in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a neuroinflammatory disease characterized by demyelination and axonal damage of the central nervous system. The pathogenesis of MS has also been linked to vascular inflammation and local activation of the coagulation system, resulting in perivascular fibrin deposition. Treatment of experimental autoimmune encephalomyelitis (EAE), a model of human MS, with antithrombotic and antiinflammatory activated protein C (APC) reduces disease severity. Since recombinant APC (Drotecogin alfa), originally approved for the treatment of severe sepsis, is not available for human MS studies, we tested the hypothesis that pharmacologic activation of endogenous protein C could likewise improve the outcome of EAE. Mice were immunized with murine myelin oligodendrocyte glycoprotein (MOG) peptides and at the onset of EAE symptoms, were treated every other day with either WE thrombin (25 μg/kg; i.v.), a selective recombinant protein C activator thrombin analog, or saline control. Mice were monitored for changes in disease score until euthanized for ex vivo analysis of inflammation. Administration of WE thrombin significantly ameliorated clinical severity of EAE, reduced inflammatory cell infiltration and demyelination, suppressed the activation of macrophages comprising the CD11b + population and reduced accumulation of fibrin (ogen) in the spinal cord. These data suggest that symptomatic MS may respond to a treatment strategy that involves temporal pharmacological enhancement of endogenous APC generation.

Different immunological mechanisms govern protection from experimental stroke in young and older mice with recombinant TCR ligand therapy

Stroke is a leading cause of death and disability in the United States. The lack of clinical success in stroke therapies can be attributed, in part, to inadequate basic research on aging rodents. The current study demonstrates that recombinant TCR ligand therapy uses different immunological mechanisms to protect young and older mice from experimental stroke. In young mice, RTL1000 therapy inhibited splenocyte efflux while reducing frequency of T cells and macrophages in the spleen. Older mice treated with RTL1000 exhibited a significant reduction in inflammatory cells in the brain and inhibition of splenic atrophy. Our data suggest age specific differences in immune response to stroke that allow unique targeting of stroke immunotherapies.

Novel humanized recombinant T cell receptor ligands protect the female brain after experimental stroke

Transmigration of peripheral leukocytes to the brain is a major contributor to cerebral ischemic cell death mechanisms. Humanized partial major histocompatibility complex class II constructs (pMHC), covalently linked to myelin peptides, are effective for treating experimental stroke in males, but new evidence suggests that some inflammatory cell death mechanisms after brain injury are sex-specific. We here demonstrate that treatment with pMHC constructs also improves outcomes in female mice with middle cerebral artery occlusion (MCAO). HLA-DR2 transgenic female mice with MCAO were treated with RTL1000 (HLA-DR2 moiety linked to human MOG-35-55 peptide), HLA-DRa1-MOG-35-55, or vehicle (VEH) at 3, 24, 48, and 72 h after reperfusion and were recovered for 96 h or 2 weeks post-injury for measurement of histology (TTC staining) or behavioral testing. RTL1000- and DRa1-MOG-treated mice had profoundly reduced infarct volumes as compared to the VEH group, although higher doses of DRa1-MOG were needed for females vs. males evaluated previously. RTL1000-treated females also exhibited strongly improved functional recovery in a standard cylinder test. In novel studies of post-ischemic ultrasonic vocalization (USV), as measured by animal calls to their cage mates, we modeled in mice the post-stroke speech deficits common in human stroke survivors. The number of calls was reduced in injured animals relative to pre-MCAO baseline regardless of RTL1000 treatment status. However, call duration was significantly improved by RTL1000 treatment, suggesting benefit to the animal’s recovery of vocalization capability. We conclude that both the parent RTL1000 molecule and the novel non-polymorphic DRα1-MOG-35-55 construct were highly effective immunotherapies for treatment of transient cerebral ischemia in females.

HLA-DRα1 constructs block CD74 expression and MIF effects in experimental autoimmune encephalomyelitis

CD74, the cell-surface form of the MHC class II invariant chain, is a key inflammatory factor that is involved in various immune-mediated diseases as part of the macrophage migration inhibitory factor (MIF) binding complex. However, little is known about the natural regulators of CD74 in this context. In order to study the role of the HLA-DR molecule in regulating CD74, we used the HLA-DRα1 domain, which was shown to bind to and downregulate CD74 on CD11b(+) monocytes. We found that DRα1 directly inhibited binding of MIF to CD74 and blocked its downstream inflammatory effects in the spinal cord of mice with experimental autoimmune encephalomyelitis (EAE). Potency of the DRα1 domain could be destroyed by trypsin digestion but enhanced by addition of a peptide extension (myelin oligodendrocyte glycoprotein [MOG]-35-55 peptide) that provided secondary structure not present in DRα1. These data suggest a conformationally sensitive determinant on DRα1-MOG that is responsible for optimal binding to CD74 and antagonism of MIF effects, resulting in reduced axonal damage and reversal of ongoing clinical and histological signs of EAE. These results demonstrate natural antagonist activity of DRα1 for MIF that was strongly potentiated by the MOG peptide extension, resulting in a novel therapeutic, DRα1-MOG-35-55, that within the limitations of the EAE model may have the potential to treat autoimmune diseases such as multiple sclerosis.