MIF contribution to progressive brain diseases

Progressive brain diseases create a huge social and economic burden on modern societies as a major cause of disability and death. Incidence of brain diseases has a significantly increasing trend and merits new therapeutic strategies. At the base of many progressive brain malfunctions is a process of unresolved, chronic inflammation. Macrophage migration inhibitory factor, MIF, is an inflammatory mediator that recently gained interest of neuro-researchers due to its varied effects on the CNS such as participation of nervous system development, neuroendocrine functions, and modulation of neuroinflammation. MIF appears to be a candidate as a new biomarker and target of novel therapeutics against numerous neurologic diseases ranging from cancer, autoimmune diseases, vascular diseases, neurodegenerative pathology to psychiatric disorders. In this review, we will focus on MIF's crucial role in neurological diseases such as multiple sclerosis (MS), Alzheimer's disease (AD) and glioblastoma (GBM).

Pharmacological targeting of coagulation factor XI attenuates experimental autoimmune encephalomyelitis in mice

Multiple sclerosis (MS) is the most common causes of non-traumatic disability in young adults worldwide. MS pathophysiologies include the formation of inflammatory lesions, axonal damage and demyelination, and blood brain barrier (BBB) disruption. Coagulation proteins, including factor (F)XII, can serve as important mediators of the adaptive immune response during neuroinflammation. Indeed, plasma FXII levels are increased during relapse in relapsing-remitting MS patients, and previous studies showed that reducing FXII levels was protective in a murine model of MS, experimental autoimmune encephalomyelitis (EAE). Our objective was to determine if pharmacological targeting of FXI, a major substrate of activated FXII (FXIIa), improves neurological function and attenuates CNS damage in the setting of EAE. EAE was induced in male mice using murine myelin oligodendrocyte glycoprotein peptides combined with heat-inactivated Mycobacterium tuberculosis and pertussis toxin. Upon onset of symptoms, mice were treated every other day intravenously with anti-FXI antibody, 14E11, or saline. Disease scores were recorded daily until euthanasia for ex vivo analyses of inflammation. Compared to the vehicle control, 14E11 treatment reduced the clinical severity of EAE and total mononuclear cells, including CD11b+CD45high macrophage/microglia and CD4+ T cell numbers in brain. Following pharmacological targeting of FXI, BBB disruption was reduced, as measured by decreased axonal damage and fibrin(ogen) accumulation in the spinal cord. These data demonstrate that pharmacological inhibition of FXI reduces disease severity, immune cell migration, axonal damage, and BBB disruption in mice with EAE. Thus, therapeutic agents targeting FXI and FXII may provide a useful approach for treating autoimmune and neurologic disorders.

Novel therapeutic for multiple sclerosis protects white matter function in EAE mouse model

Multiple sclerosis (MS) is a chronic demyelinating disease with prominent axon dysfunction. Our previous studies in an MS mouse model, experimental autoimmune encephalomyelitis (EAE), demonstrated that major histocompatibility complex Class II constructs can reverse clinical signs of EAE. These constructs block binding and downstream signaling of macrophage migration inhibitory factors (MIF-1/2) through CD74, thereby inhibiting phosphorylation of extracellular signal-regulated kinase (ERK) activation and tissue inflammation and promoting remyelination. To directly assess the effects of a novel third generation construct, DRhQ, on axon integrity in EAE, we compared axon conduction properties using electrophysiology on corpus callosum slices and optic nerves. By using two distinct white matter (WM) tracts, we aimed to assess the impact of the EAE and the benefit of DRhQ on myelinated and unmyelinated axons as well as to test the clinical value of DRhQ on demyelinating lesions in CC and optic myelitis. Our study found that EAE altered axon excitability, delayed axon conduction and slowed spatiotemporal summation correlated with diffuse astrocyte and microglia activation. Because MS predisposes patients to stroke, we also investigated and showed that vulnerability to WM ischemia is increased in the EAE MS mouse model. Treatment with DRhQ after the onset of EAE drastically inhibited microglial and astrocyte activation, improved functional integrity of the myelinated axons and enhanced recovery after ischemia. These results demonstrate that DRhQ administered after the onset of EAE promotes WM integrity and function, and reduces subsequent vulnerability to ischemic injury, suggesting important therapeutic potential for treatment of progressive MS.

PD-L1 is required for estrogen-induced protection against severe EAE in IL-10 deficient mice1

BACKGROUND

IL-10 knockout (KO) mice can be protected against experimental autoimmune encephalomyelitis (EAE) with low-dose estrogen (E2) treatment similar to wild type (WT) mice, indicating that IL-10 is not required for E2-induced EAE protection. Our previous study demonstrated that E2 treatment induced an increase in programmed death ligands 1 (PD-L1) and 2 (PD-L2) on monocytes and macrophages in the periphery and within the CNS. In this study, we selectively inhibited the function of PD-L1 and PD-L2 to evaluate their critical role in maintaining E2-induced protection against EAE in IL-10-KO mice.

METHODS

This study used female IL-10 KO mice pre-treated with either E2 or sham pellets seven days prior to induction of EAE and subsequently treated with Vehicle or antibodies to PD-L1, PD-L2 or respective isotype controls. Mice were scored daily for EAE severity over 21 days post-EAE induction. Cells from the spleen and brain were evaluated by flow cytometry.

RESULTS

Differences in EAE severity were assessed in E2 and sham pre-treated IL-10-KO mice treated with α-PD-L1 or α-PD-L2 antibodies over the course of disease compared to treatment with Vehicle or isotype control antibodies. The results revealed real-time development of severe EAE in E2-pre-treated IL-10-KO mice treated with α-PD-L1 but not α-PD-L2 antibodies, mediated in part by increased percentages of activated CD74⁺CD11b⁺ myeloid cells in spleen and brain as well as splenic B-cells, T-cells and CD73⁺ cells.

CONCLUSION

These results demonstrate unequivocally that PD-L1 but not PD-L2 was required to retain the inhibitory effects of E2 on clinical EAE scores in female IL-10-KO mice and further implicate the emergence of the MIF/CD74 axis as a contributing pathogenic mechanism.

"Near Cure" treatment of severe acute EAE in MIF-1-deficient female and male mice with a bifunctional MHCII-derived molecular construct

Our previous studies demonstrated increased serum levels of macrophage migration inhibitory factor (MIF-1) and its homologue, MIF-2, in males during MS progression; and that genetically high-MIF-expressing male subjects with relapsing multiple sclerosis (MS) had a significantly greater risk of conversion to progressive MS than lower-MIF-expressing males and females. However, female MS subjects with severe disease expressed higher levels of CD74, the common MIF-1/MIF-2 receptor, on blood cells. In the murine model of MS, experimental autoimmune encephalomyelitis (EAE), both male and female mice lacking MIF-1 and/or MIF-2 were clinically improved during development of moderately severe disease, thus implicating both homologs as co-pathogenic contributors. The current study using MIF-deficient mice with severe acute EAE revealed a highly significant reduction of EAE scores in MIF-1-deficient females, in contrast to only minor and delayed reduction of clinical signs in MIF-1-deficient males. However, clinical EAE scores and factor expression were strongly suppressed in males and further reduced in females after treatment of WT and MIF-1-, MIF-2- and MIF-1/2-DUAL-deficient female and male mice with a MHCII DRα1-MOG-35-55 molecular construct that competitively inhibits MIF-1 & MIF-2 signaling through CD74 as well as T cell activation. These results suggest sex-dependent differences in which the absence of the MIF-1 and/or MIF-2 genotypes may permit stronger compensatory CD74-dependent EAE-inducing responses in males than in females. However, EAE severity in both sexes could still be reduced nearly to background (a "near cure") with DRα1-MOG-35-55 blockade of compensatory MIF and CD74-dependent factors known to attract peripheral inflammatory cells into the spinal cord tissue.

Tyrphostin A9 protects axons in experimental autoimmune encephalomyelitis through activation of ERKs

AIMS

Small molecule compound tyrphostin A9 (A9), an inhibitor of platelet-derived growth factor (PDGF) receptor, was previously reported by our group to stimulate extracellular signal-regulated kinase 1 (ERK1) and 2 (ERK2) in neuronal cells in a PDGF receptor-irrelevant manner. The study aimed to investigate whether A9 could protect axons in experimental autoimmune encephalomyelitis through activation of ERKs.

MAIN METHODS

A9 treatment on the protection on neurite outgrowth in SH-SY5Y neuroblastoma cells and primary substantia nigra neuron cultures from the neurotoxin MPP+ were analyzed. Then, clinical symptoms as well as ERK1/2 activation, axonal protection induction, and the abundance increases of the regeneration biomarker GAP-43 in the CNS in the relapsing-remitting experimental autoimmune encephalomyelitis (EAE) model were verified.

KEY FINDINGS

A9 treatment could stimulate neurite outgrowth in SH-SY5Y neuroblastoma cells and protect primary substantia nigra neuron cultures from the neurotoxin MPP+. In the relapsing-remitting EAE model, oral administration of A9 successfully ameliorated clinical symptoms, activated ERK1/2, induced axonal protection, and increased the abundance of the regeneration biomarker GAP-43 in the CNS. Interestingly, gene deficiency of ERK1 or ERK2 disrupted the beneficial effects of A9 in MOG-35-55-induced EAE.

SIGNIFICANCE

These results demonstrated that small molecule compounds that stimulate persistent ERK activation in vitro and in vivo may be useful in protective or restorative treatment for neurodegenerative diseases.

Microglia and astrocyte involvement in neurodegeneration and brain cancer

The brain is unique and the most complex organ of the body, containing neurons and several types of glial cells of different origins and properties that protect and ensure normal brain structure and function. Neurological disorders are the result of a failure of the nervous system multifaceted cellular networks. Although great progress has been made in the understanding of glia involvement in neuropathology, therapeutic outcomes are still not satisfactory. Here, we discuss recent perspectives on the role of microglia and astrocytes in neurological disorders, including the two most common neurodegenerative conditions, Alzheimer disease and progranulin-related frontotemporal lobar dementia, as well as astrocytoma brain tumors. We emphasize key factors of microglia and astrocytic biology such as the highly heterogeneic glial nature strongly dependent on the environment, genetic factors that predispose to certain pathologies and glia senescence that inevitably changes the CNS landscape. Our understanding of diverse glial contributions to neurological diseases can lead advances in glial biology and their functional recovery after CNS malfunction.

Brief report: Enhanced DRα1-mMOG-35-55 treatment of severe EAE in MIF-1-deficient male mice

Macrophage migration inhibitory factor (MIF-1) and its homologue d-dopachrome tautomerase (MIF-2) share the common CD74 receptor and function innately to enhance severity of multiple sclerosis (MS) as well as the experimental autoimmune encephalomyelitis (EAE) model for MS. We previously demonstrated that genetically high-MIF-expressing male subjects with relapsing MS had a significantly greater risk of conversion to progressive MS (PMS) than lower-MIF-expressing males. To expand on this observation, we utilized MIF-1, MIF-2, and MIF-1/2-DUAL-deficient male mice to discern if there would be a greater contribution of these inflammatory factors in EAE mice with severe vs. moderate clinical disease signs. As shown previously, mice deficient in either MIF-1 or MIF-2 each had a ∼25% reduction of moderate EAE compared to WT mice, with significant differences in disease onset and trajectory. However, EAE induction in mice deficient in both MIF-1 and MIF-2 genes did not result in a further reduction in EAE severity. This result suggests that the two MIF homologues were likely affecting the same pathogenic pathways such that each could partially compensate for the other but not in an additive or synergistic manner. However, MIF-1-KO, MIF-2-KO, and MIF-1/2-DUAL-KO mice with severe EAE did not exhibit a significant reduction in cumulative EAE scores compared with WT mice, but the MIF-1-KO and, to a lesser extent, MIF-1/2-DUAL-KO mice did show a significant reduction in daily EAE scores over the last 3 days of observation, and MIF-2-KO mice showed a more modest but still consistent reduction over the same span. Furthermore, deletion of MIF-1 resulted in a massive reduction in the expression of EAE- and Complete Freund's Adjuvant-associated inflammatory factors, suggesting delayed involvement of the MIF/CD74 axis in promoting disease expression. To further explore modulation of MIF-1 and MIF-2 effects on EAE, we treated WT mice with moderate EAE using DRα1-mMOG-35-55, an inhibitor of CD74 that blocks both MIF-1 and MIF-2 action. This treatment reduced ongoing moderate EAE severity in excess of 25%, suggesting efficient blockade of the MIF/CD74 axis in disease-enhancing pathways. Moreover, DRα1-mMOG-35-55 treatment of mice with severe EAE strongly reversed EAE- and CFA-associated expression of inflammatory cytokines and chemokines including Tnf, Ccr7, Ccr6, Ccl8, Cxcr3, and Ccl19 in MIF-deficient mouse genotypes, and also exceeded innate MIF-1 and MIF-2 EAE enhancing effects, especially in MIF-1-KO mice. These results illustrate the therapeutic potential of targeting the disease-enhancing MIF/CD74 pathway in male mice with moderate and severe EAE, with implications for treatment of high-MIF-expressing RRMS human males at risk of conversion to progressive MS as well as those that have already transitioned to PMS.

Cross-Talk of the CNS With Immune Cells and Functions in Health and Disease

The immune system's role is much more than merely recognizing self vs. non-self and involves maintaining homeostasis and integrity of the organism starting from early development to ensure proper organ function later in life. Unlike other systems, the central nervous system (CNS) is separated from the peripheral immune machinery that, for decades, has been envisioned almost entirely as detrimental to the nervous system. New research changes this view and shows that blood-borne immune cells (both adaptive and innate) can provide homeostatic support to the CNS via neuroimmune communication. Neurodegeneration is mostly viewed through the lens of the resident brain immune populations with little attention to peripheral circulation. For example, cognition declines with impairment of peripheral adaptive immunity but not with the removal of microglia. Therapeutic failures of agents targeting the neuroinflammation framework (inhibiting immune response), especially in neurodegenerative disorders, call for a reconsideration of immune response contributions. It is crucial to understand cross-talk between the CNS and the immune system in health and disease to decipher neurodestructive and neuroprotective immune mechanisms for more efficient therapeutic strategies.

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.

Partial MHC/neuroantigen peptide constructs attenuate methamphetamine-seeking and brain chemokine (C-C motif) ligand 2 levels in rats

There are no medications that target the neurotoxic effects or reduce the use of methamphetamine. Recombinant T-cell receptor ligand (RTL) 1000 [a partial major histocompatibility complex (pMHC) class II construct with a tethered myelin peptide], addresses the neuroimmune effects of methamphetamine addiction by competitively inhibiting the disease-promoting activity of macrophage migration inhibitory factor to CD74, a key pathway involved in several chronic inflammatory conditions, including substance use disorders. We previously reported that RTL constructs improve learning and memory impairments and central nervous system (CNS) inflammation induced by methamphetamine in mouse models. The present study in Lewis rats evaluated the effects of RTL1000 on maintenance of self-administration and cue-induced reinstatement using operant behavioral methods. Post-mortem brain and serum samples were evaluated for the levels of inflammatory factors. Rats treated with RTL1000 displayed significantly fewer presses on the active lever as compared to rats treated with vehicle during the initial extinction session, indicating more rapid extinction in the presence of RTL1000. Immunoblotting of rat brain sections revealed reduced levels of the pro-inflammatory chemokine (C-C motif) ligand 2 (CCL2) in the frontal cortex of rats treated with RTL1000, as compared to vehicle. Post hoc analysis identified a positive association between the levels of CCL2 detected in the frontal cortex and the number of lever presses during the first extinction session. Taken together, results suggest that RTL1000 may block downstream inflammatory effects of methamphetamine exposure and facilitate reduced drug seeking-potentially offering a new strategy for the treatment of methamphetamine-induced CNS injury and neuropsychiatric impairments.

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.

Sex differences in the therapeutic effects of anti-PDL2 neutralizing antibody on stroke

Inflammation involving migration of immune cells across the damaged blood-brain barrier (BBB), activation of resident innate microglia and production of inflammatory humoral mediators such as cytokines and chemokines play a critical role in the pathogenesis of ischemic stroke. Cell-cell signaling involved in the process also includes checkpoint interaction between programmed death receptor (PD1) and programmed death ligands, PDL1 and PDL2. Based on our previous studies showing reduced MCAO infarct volumes in PDL2 deficient mice, we evaluated the ability of anti-PDL2 mAb to treat MCAO in male and female C57BL/6 mice. We found that anti-PDL2 neutralizing antibody treatment of MCAO significantly reduced infarct volumes in male mice but had no protective effects in female mice even at a 5-fold increased dose of anti-PDL2 mAb. The protection in male mice was likely mediated by reduced percentages in the spleen of PDL2⁺CD19⁺ B cells, PDL1⁺CD4⁺ T cells and CD86⁺CD11b⁺ macrophages in concert with reduced expression of PDL1 and TNFα and continued expression of CD206, in the injured ipsilateral brain hemisphere. The lack of a therapeutic benefit of anti-PDL2 on stroke-induced infarct volumes in female mice was reflected by no detectable reduction in expressed PDL2 or PDL1 and an increased frequency of Th₁ and Th₁₇ pro-inflammatory T cell subsets in the spleen, an effect not seen in PDL2 mAb treated males. This result potentially limits the utility of anti-PDL2 mAb therapy in stroke to males but underscores the importance of meeting the STAIR requirements for development of new stroke therapies for both sexes.

Estrogen-induced compensatory mechanisms protect IL-10-deficient mice from developing EAE

Background

IL-10 knockout (KO) mice are protected from experimental autoimmune encephalomyelitis (EAE) with low-dose estrogen (E2) treatment similar to wild-type (WT) mice. Previous studies have demonstrated a decrease in tumor necrosis factor in all E2-treated groups, which led to the protection of the mice.

Methods

This study used IL-10 KO mice and WT mice treated either with E2 or sham pellets 7 days prior to induction of EAE. Mice were observed for 21 days post-immunization. The spleen, inguinal lymph nodes, and brain were evaluated by flow cytometry. Spinal cords were evaluated using a cytokine/chemokine array, RT-PCR, and histology.

Results

This study demonstrates that E2 treatment induced three heightened regulatory mechanisms that potentially protect IL-10 KO mice from EAE: (1) an increase in programmed death-ligands 1 and 2 on monocytes and macrophages in the periphery and within the CNS; (2) an increase in CD73 in the inflamed CNS, which can increase the production of the anti-inflammatory molecule adenosine; and (3) a decrease in CD4⁺CD25⁺FoxP3⁺ regulatory T cells in the spleen. Together, these factors comprise an alternative compensatory mechanism that significantly downregulates key pro-inflammatory cytokine, chemokine, and chemokine receptor genes which are enhanced in the spinal cord of IL-10 KO mice. This group of E2-treated mice remained asymptomatic after EAE challenge similar to E2-treated WT mice, despite their having more T and B lymphocytes in the brain, and modestly increased demyelination in the spinal cord.

Conclusion

These results indicate that previously unrecognized compensatory mechanisms of EAE protection are stimulated by E2 in the absence of IL-10, which can provide disease protection comparable to the IL-10-dependent effects induced by E2 in WT mice.

Increased CD74 binding and EAE treatment efficacy of a modified DRα1 molecular construct

Multiple sclerosis (MS) is a demyelinating and degenerative disease of the central nervous system (CNS) with a strong inflammatory component that affects more than 2 million people worldwide (and at least 400,000 in the United States). In MS, macrophage migration inhibitory factor (MIF) and D-dopachrome tautomerase (D-DT) enhance the inflammatory event as a result of their interaction with their cognate receptor CD74. Therefore, the search for new agents aimed at blocking this interaction is critical for therapeutic purposes and will be of paramount importance for the treatment of MS. DRα1-MOG-35-55 constructs have been demonstrated to be effective in the treatment of experimental autoimmune encephalomyelitis (EAE) a mouse model for MS. This effect is directly correlated with the binding to its cell surface receptor, CD74, apparently preventing or blocking the binding of two inflammatory factors, MIF and D-DT. Here we report that a single amino acid substitution (L50Q) in the DRα1 domain of the human and mouse DRα1-MOG-35-55 constructs (notated as DRhQ and DRmQ, respectively) possessed increased affinity for CD74, a greater capacity to block MIF binding, the ability to inhibit pERK1/2 signaling and increased therapeutic activity in mice with EAE. These data suggest that binding affinity for CD74 could serve as an in vitro indicator of biological potency of DRhQ and thus support its possible clinical utility as an effective therapy for MS and perhaps other diseases in which there is an inflammatory reaction driven by MIF and D-DT.

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.

Antibiotics protect against EAE by increasing regulatory and anti-inflammatory cells

A seven day pretreatment course of an oral antibiotic cocktail (Ampicillin, Metronidazole, Neomycin Sulfate, and Vancomycin) was shown to induce changes in peripheral immune regulation and protect mice from signs of experimental autoimmune encephalomyelitis (EAE). To determine if a shorter course of antibiotic pretreatment could also protect the mice from EAE and induce regulatory immune cells, studies were conducted using the same oral antibiotic cocktail for three days. In addition, the CNS was examined to determine the effects of antibiotic pretreatment on EAE disease course and immune modulation within the affected tissue. The shorter three day pretreatment course was also significantly protective against severe EAE in C57BL/6 mice. Moreover, our study found increased frequencies of regulatory cells and a decrease in the frequency of anti-inflammatory macrophages in the spleen of EAE protected mice. Additionally, a chemokine and chemokine receptor array run on mRNA from spinal cords revealed that genes associated with regulatory T cells and macrophage recruitment were strongly upregulated in the antibiotic pretreated mice. Additional RT-PCR data showed genes associated with anti-inflammatory microglia/macrophages were upregulated and pro-inflammatory genes were downregulated. This suggests the macrophages recruited to the spinal cord by chemokines are subsequently polarized toward an anti-inflammatory phenotype. These results lend strong support to the conclusion that a three day course of antibiotic treatment given prior to the induction of severe EAE profoundly protected the mice by inducing regulatory lymphocytes in the periphery and an anti-inflammatory milieu in the affected spinal cord tissue.

Regulatory B cells in experimental stroke

Current treatment options for human stroke are limited mainly to the modestly effective infusion of tissue plasminogen activator (tPA), with additional improvement of functional independence and higher rates of angiographic revascularization observed after mechanical thrombectomy. However, new therapeutic strategies that address post-stroke immune-mediated inflammatory responses are urgently needed. Recent studies in experimental stroke have firmly implicated immune mechanisms in the propagation and partial resolution of central nervous system damage after the ischaemic event. A new-found anti-inflammatory role for regulatory B (Breg) cells in autoimmune diseases sparked interest in these cells as potential immunomodulators in stroke. Subsequent studies identified interleukin-10 as a common regulatory cytokine among all five of the currently recognized Breg cell subsets, several of which can be found in the affected brain hemisphere after induction of experimental stroke in mice. Transfer of enriched Breg cell subpopulations into both B-cell-depleted and wild-type mice confirmed their potent immunosuppressive activities in vivo, including recruitment and potentiation of regulatory T cells. Moreover, Breg cell therapy strongly reduced stroke volumes and treatment outcomes in ischaemic mice even when administered 24 hr after induction of experimental stroke, a treatment window far exceeding that of tPA. These striking results suggest that transfer of enriched Breg cell populations could have therapeutic value in human stroke, although considerable clinical challenges remain.

Estrogen protects both sexes against EAE by promoting common regulatory cell subtypes independent of endogenous estrogen

Autoimmune diseases including multiple sclerosis predominantly affect females. Although high levels of sex hormones, particularly estrogen (E2), can reduce proinflammatory immune responses, it remains unclear if a lack of endogenous sex hormones might affect treatment with exogenous sex hormones. Pretreatment with E2 almost completely prevents intact female and male mice from developing clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) by promoting various regulatory immune cell phenotypes. To evaluate the effects of exogenous estrogen in the absence of endogenous sex hormones, the current study compared EAE severity and the emergence of different immunoregulatory cell populations after E2 pretreatment of ovariectomized (OVX) female versus male mice. We found that E2 equally protected both OVX females and males from EAE over a 21 day observation period concomitant with reduced total cell numbers in spleen and spinal cord (males only), but enhanced percentages of CD19⁺CD5⁺CD1d^hi, CD19⁺CD138⁺CD44^hi and CD19⁺Tim-1⁺ Breg cells, CD8⁺CD122⁺ Treg cells and CD11b⁺CD 206⁺ARG-1⁺ anti-inflammatory M2-like monocytes/macrophages in both groups. In contrast, E2 decreased the percentage of CD4⁺CD25⁺FoxP3⁺ Treg cells in OVX females but increased these Treg cells in males and intact female mice. These data suggest that with the exception of CD4⁺CD25⁺FoxP3⁺ Treg cells, E2 protection against EAE promotes highly overlapping immunoregulatory subsets in OVX females and males.

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.

Estrogen protection against EAE modulates the microbiota and mucosal-associated regulatory cells

Sex hormones promote immunoregulatory effects on multiple sclerosis. In the current study we evaluated the composition of the gut microbiota and the mucosal-associated regulatory cells in estrogen or sham treated female mice before and after autoimmune encephalomyelitis (EAE) induction. Treatment with pregnancy levels of estrogen induces changes in the composition and diversity of gut microbiota. Additionally, estrogen prevents EAE-associated changes in the gut microbiota and might promote the enrichment of bacteria that are associated with immune regulation. Our results point to a possible cross-talk between the sex hormones and the gut microbiota, which could promote neuroprotection.

Sex differences in regulatory cells in experimental stroke

Stroke is the leading cause of disability in the United States. Sex differences, including smaller infarcts in females and greater involvement of immune-mediated inflammation in males may affect the efficacy of immune-modulating interventions. To address these differences, we sought to identify distinct stroke-modifying mechanisms in female vs. male mice. The current study demonstrated smaller infarcts and increased levels of regulatory CD19⁺CD5⁺CD1d^hi B10 cells as well as anti-inflammatory CD11b⁺CD206⁺ microglia/macrophages in the ipsilateral vs. contralateral hemisphere of female but not male mice undergoing 60min middle cerebral artery occlusion followed by 96h of reperfusion. Moreover, female mice with MCAO had increased total spleen cell numbers but lower B10 levels in spleens. These results elucidate differing sex-dependent regulatory mechanisms that account for diminished stroke severity in females and underscore the need to test immune-modulating therapies for stroke in both males and females.

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.

Novel feedback loop between M2 macrophages/microglia and regulatory B cells in estrogen-protected EAE mice

Immunoregulatory sex hormones, including estrogen and estriol, may prevent relapses in multiple sclerosis during pregnancy. Our previous studies have demonstrated that regulatory B cells are crucial for estrogen-mediated protection against experimental autoimmune encephalomyelitis (EAE). Herein, we demonstrate an estrogen-dependent induction of alternatively activated (M2) macrophages/microglia that results in an increased frequency of regulatory B cells in the spinal cord of estrogen treated mice with EAE. We further demonstrate that cultured M2-polarized microglia promote the induction of regulatory B cells. Our study suggests that estrogen neuroprotection induces a regulatory feedback loop between M2 macrophages/microglia and regulatory B cells.

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.

A highly immunogenic trivalent T cell receptor peptide vaccine for multiple sclerosis

Background: T cell receptor (TCR) peptide vaccination is a novel approach to treating multiple sclerosis (MS). The low immunogenicity of previous vaccines has hindered the development of TCR peptide vaccination for MS. Objective: To compare the immunogenicity of intramuscular injections of TCR BV5S2, BV6S5 and BV13S1 CDR2 peptides in incomplete Freund’s adjuvant (IFA) with intradermal injections of the same peptides without IFA. Methods: MS subjects were randomized to receive TCR peptides/IFA, TCR peptides/saline or IFA alone. Subjects were on study for 24 weeks. Results: The TCR peptides/IFA vaccine induced vigorous T cell responses in 100% of subjects completing the 24-week study (9/9) compared with only 20% (2/10) of those receiving the TCR peptides/saline vaccine (P =0.001). IFA alone induced a weak response in only one of five subjects. Aside from injection site reactions, there were no significant adverse events attributable to the treatment. Conclusions: The trivalent TCR peptide in IFA vaccine represents a significant improvement in immunogenicity over previous TCR peptide vaccines and warrants investigation of its ability to treat MS.

Estrogen induces multiple regulatory B cell subtypes and promotes M2 microglia and neuroprotection during experimental autoimmune encephalomyelitis

Sex hormones promote potent immunoregulatory effects on autoimmune diseases, including multiple sclerosis (MS). Our previous studies demonstrated a critical role for regulatory B cells in mediating estrogen (17β-estradiol, E2)-mediated protection against experimental autoimmune encephalomyelitis (EAE), a mouse model for MS, leading to elevated numbers of IL-10 secreting CD1dhiCD5+B regulatory cells (Bregs) in wild type mice. The current study evaluated estrogen effects on regulatory B cells and resident CNS microglia during EAE and demonstrates for the first time an E2-dependent induction of multiple regulatory B cell markers indicative of IL-10 dependent as well as IFN-γ dependent pathways. Moreover, although E2 pretreatment of female EAE mice inhibited the infiltration of pro-inflammatory immune cells into the CNS compared with sham pretreated mice, it enhanced the frequency of regulatory B cells and M2 microglia in the CNS. Our study suggests that estrogen has a broad effect on the development of regulatory B cells during EAE, which in turn could promote neuroprotection in the CNS.

Predicted structure of MIF/CD74 and RTL1000/CD74 complexes

Macrophage migration inhibitory factor (MIF) is a key cytokine in autoimmune and inflammatory diseases that attracts and then retains activated immune cells from the periphery to the tissues. MIF exists as a homotrimer and its effects are mediated through its primary receptor, CD74 (the class II invariant chain that exhibits a highly structured trimerization domain), present on class II expressing cells. Although a number of binding residues have been identified between MIF and CD74 trimers, their spatial orientation has not been established. Using a docking program in silico, we have modeled binding interactions between CD74 and MIF as well as CD74 and a competitive MIF inhibitor, RTL1000, a partial MHC class II construct that is currently in clinical trials for multiple sclerosis. These analyses revealed 3 binding sites on the MIF trimer that each were predicted to bind one CD74 trimer through interactions with two distinct 5 amino acid determinants. Surprisingly, predicted binding of one CD74 trimer to a single RTL1000 antagonist utilized the same two 5 residue determinants, providing strong suggestive evidence in support of the MIF binding regions on CD74. Taken together, our structural modeling predicts a new MIF(CD74)3 dodecamer that may provide the basis for increased MIF potency and the requirement for ~3-fold excess RTL1000 to achieve full antagonism.

Role for microglia in sex differences after ischemic stroke: importance of M2

Inflammation plays a critical role in the pathogenesis of ischemic stroke. This process depends, in part, upon proinflammatory factors released by activated resident central nervous system (CNS) microglia (MG). Previous studies demonstrated that transfer of IL-10(+) B-cells reduced infarct volumes in male C57BL/6 J recipient mice when given 24 h prior to or therapeutically at 4 or 24 h after experimental stroke induced by 60 min middle cerebral artery occlusion (MCAO). The present study assesses possible sex differences in immunoregulation by IL-10(+) B-cells on primary male vs. female MG cultured from naïve and ischemic stroke-induced mice. Thus, MG cultures were treated with recombinant (r)IL-10, rIL-4 or IL-10(+) B-cells after lipopolysaccharide (LPS) activation and evaluated by flow cytometry for production of proinflammatory and anti-inflammatory factors. We found that IL-10(+) B-cells significantly reduced MG production of TNF-α, IL-1β and CCL3 post-MCAO and increased their expression of the anti-inflammatory M2 marker, CD206, by cell-cell interactions. Moreover, MG from female vs. male mice had higher expression of IL-4 and IL-10 receptors and increased production of IL-4, especially after treatment with IL-10(+) B-cells. These findings indicate that IL-10-producing B-cells play a crucial role in regulating MG activation, proinflammatory cytokine release and M2 phenotype induction, post-MCAO, with heightened sensitivity of female MG to IL-4 and IL-10. This study, coupled with our previous demonstration of increased numbers of transferred IL-10(+) B-cells in the ischemic hemisphere, provide a mechanistic basis for local regulation by secreted IL-10 and IL-4 as well as direct B-cell/MG interactions that promote M2-MG.

Treatment with IL-10 producing B cells in combination with E2 ameliorates EAE severity and decreases CNS inflammation in B cell-deficient mice

Clinical improvement during pregnancy in multiple sclerosis (MS) patients suggests that sex hormones exert potent regulatory effects on autoimmune function. Our previous studies demonstrated that estrogen- (17β-estradiol; E2) mediated protection against experimental autoimmune encephalomyelitis (EAE), a mouse model for MS, hinges on the B cells, leading to elevated numbers of IL-10 secreting CD1d(hi)CD5(+) B regulatory cells (Bregs) in wild type mice. Our data show that co-administration of E2 and IL-10(+) B cells ameliorates EAE disease severity and limits CNS infiltrating leukocytes in B cell deficient mice. Additionally, treatment with E2 and Bregs reduces demyelination and dramatically decreases the proportion of CD11b(+)CD45(hi) activated microglia/macrophages found in the CNS of immunized animals compared to vehicle, E2 or Breg cells alone. Furthermore, mice given E2 and Bregs exhibit increased numbers of peripheral programmed death-1 positive CD4(+)Foxp3(+) regulatory T cells (Tregs) and up-regulation of programmed death receptor-ligand-1 and CD80 expression on monocytes. Our study suggests IL-10 producing Bregs have powerful therapeutic potential as an agent against EAE when augmented with E2 treatment.

PD-L1 Monoclonal Antibody Treats Ischemic Stroke by Controlling Central Nervous System Inflammation

BACKGROUND AND PURPOSE

Both pathogenic and regulatory immune processes are involved in the middle cerebral artery occlusion (MCAO) model of experimental stroke, including interactions involving the programmed death 1 (PD-1) receptor and its 2 ligands, PD-L1 and PD-L2. Although PD-1 reduced stroke severity, PD-L1 and PD-L2 appeared to play pathogenic roles, suggesting the use of anti-PD-L monoclonal antibody therapy for MCAO.

METHODS

Male C57BL/6 mice were treated with a single dose of anti-PD-L1 monoclonal antibody 4 hours after MCAO and evaluated for clinical, histological and immunologic changes after 96 hours of reperfusion.

RESULTS

Blockade of the PD-L1 checkpoint using a single injection of 200 μg anti-PD-L1 monoclonal antibody given intravenously 4 hours after occlusion significantly reduced MCAO infarct volumes and improved neurological outcomes after 96 hours of reperfusion. Treatment partially reversed splenic atrophy and decreased central nervous system infiltrating immune cells concomitant with enhanced appearance of CD8(+) regulatory T cells in the lesioned central nervous system hemisphere.

CONCLUSIONS

This study demonstrates for the first time the beneficial therapeutic effects of PD-L1 checkpoint blockade on MCAO, thus validating proposed mechanisms obtained in our previous studies using PD-1- and PD-L-deficient mice. These results provide strong support for the use of available humanized anti-PD-L1 antibodies for treatment of human stroke subjects.

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.

Regulatory CD8(+)CD122 (+) T-cells predominate in CNS after treatment of experimental stroke in male mice with IL-10-secreting B-cells

Clinical stroke induces inflammatory processes leading to cerebral and splenic injury and profound peripheral immunosuppression. IL-10 expression is elevated during major CNS diseases and limits inflammation in the brain. Recent evidence demonstrated that transfer of IL-10(+) B-cells reduced infarct volume in male C57BL/6J (wild-type, WT) recipient mice when given 24 h prior to or 4 h after middle cerebral artery occlusion (MCAO). The purpose of this study was to determine if passively transferred IL-10(+) B-cells can exert therapeutic and immunoregulatory effects when injected 24 h after MCAO induction in B-cell-sufficient male WT mice. The results demonstrated that IL-10(+) B-cell treated mice had significantly reduced infarct volumes in the ipsilateral cortex and hemisphere and improved neurological deficits vs. Vehicle-treated control mice after 60 min occlusion and 96 h of reperfusion. The MCAO-protected B-cell recipient mice had less splenic atrophy and reduced numbers of activated, inflammatory T-cells, decreased infiltration of T-cells and a less inflammatory milieu in the ischemic hemispheres compared with Vehicle-treated control mice. These immunoregulatory changes occurred in concert with the predominant appearance of IL-10-secreting CD8(+)CD122(+) Treg cells in both the spleen and the MCAO-affected brain hemisphere. This study for the first time demonstrates a major neuroprotective role for IL-10(+) B-cells in treating MCAO in male WT mice at a time point well beyond the ~4 h tPA treatment window, leading to the generation of a dominant IL-10(+)CD8(+)CD122(+) Treg population associated with spleen preservation and reduced CNS inflammation.

IL-10 producing B cells partially restore E2-mediated protection against EAE in PD-L1 deficient mice

Women with multiple sclerosis (MS) often experience clinical improvement during pregnancy, indicating that sex hormones might have therapeutic effects in MS. Our previous studies have demonstrated that B cells and PD-L1 are crucial for E2 (17β-estradiol)-mediated protection against experimental autoimmune encephalomyelitis (EAE). We here demonstrate that the transfer of IL-10(+) B cells into E2-treated PD-L1(-/-) mice after EAE induction could partially restore E2-mediated protection and decrease the frequency of pro-inflammatory cells in the CNS compared to E2/saline treated PD-L1(-/-) mice. Hence, co-administration of IL-10(+) B cells and E2 might have a powerful therapeutic potential for treatment of EAE.

Targeting immune co-stimulatory effects of PD-L1 and PD-L2 might represent an effective therapeutic strategy in stroke

Stroke outcome is worsened by the infiltration of inflammatory immune cells into ischemic brains. Our recent study demonstrated that PD-L1- and to a lesser extent PD-L2-deficient mice had smaller brain infarcts and fewer brain-infiltrating cells vs. wild-type (WT) mice, suggesting a pathogenic role for PD-ligands in experimental stroke. We sought to ascertain PD-L1 and PD-L2-expressing cell types that affect T-cell activation, post-stroke in the context of other known co-stimulatory molecules. Thus, cells from male WT and PD-L-deficient mice undergoing 60 min of middle cerebral artery occlusion (MCAO) followed by 96 h of reperfusion were treated with neutralizing antibodies to study co-stimulatory and co-inhibitory interactions between CD80, cytotoxic T-lymphocyte antigen-4 (CTLA-4), PD-1, and PD-Ls that regulate CD8⁺ and CD4⁺ T-cell activation. We found that antibody neutralization of PD-1 and CTLA-4 signaling post-MCAO resulted in higher proliferation in WT CD8⁺ and CD4⁺ T-cells, confirming an inhibitory role of PD-1 and CTLA-4 on T-cell activation. Also, CD80/CD28 interactions played a prominent regulatory role for the CD8⁺ T-cells and the PD-1/PD-L2 interactions were dominant in controlling the CD4⁺ T-cell responses in WT mice after stroke. A suppressive phenotype in PD-L1-deficient mice was attributed to CD80/CTLA-4 and PD-1/PD-L2 interactions. PD-L2 was crucial in modulating CD4⁺ T-cell responses, whereas PD-L1 regulated both CD8⁺ and CD4⁺ T-cells. To establish the contribution of PD-L1 and PD-L2 on regulatory B-cells (Bregs), infarct volumes were evaluated in male PD-L1- and PD-L2-deficient mice receiving IL-10⁺ B-cells 4h post-MCAO. PD-L2- but not PD-L1-deficient recipients of IL-10⁺ B-cells had markedly reduced infarct volumes, indicating a regulatory role of PD-L2 on Bregs. These results imply that PD-L1 and PD-L2 differentially control induction of T- and Breg-cell responses after MCAO, thus suggesting that selective targeting of PD-L1 and PD-L2 might represent a valuable therapeutic strategy in stroke.

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.

Multi-analyte profile analysis of plasma immune proteins: altered expression of peripheral immune factors is associated with neuropsychiatric symptom severity in adults with and without chronic hepatitis C virus infection

BackgroundThe purpose of this study was to characterize hepatitis C virus (HCV)-associated differences in the expression of 47 inflammatory factors and to evaluate the potential role of peripheral immune activation in HCV-associated neuropsychiatric symptoms-depression, anxiety, fatigue, and pain. An additional objective was to evaluate the role of immune factor dysregulation in the expression of specific neuropsychiatric symptoms to identify biomarkers that may be relevant to the treatment of these neuropsychiatric symptoms in adults with or without HCV. MethodsBlood samples and neuropsychiatric symptom severity scales were collected from HCV-infected adults (HCV+, n = 39) and demographically similar noninfected controls (HCV-, n = 40). Multi-analyte profile analysis was used to evaluate plasma biomarkers. ResultsCompared with HCV- controls, HCV+ adults reported significantly (P < 0.050) greater depression, anxiety, fatigue, and pain, and they were more likely to present with an increased inflammatory profile as indicated by significantly higher plasma levels of 40% (19/47) of the factors assessed (21%, after correcting for multiple comparisons). Within the HCV+ group, but not within the HCV- group, an increased inflammatory profile (indicated by the number of immune factors > the LDC) significantly correlated with depression, anxiety, and pain. Within the total sample, neuropsychiatric symptom severity was significantly predicted by protein signatures consisting of 4-10 plasma immune factors; protein signatures significantly accounted for 19-40% of the variance in depression, anxiety, fatigue, and pain. ConclusionsOverall, the results demonstrate that altered expression of a network of plasma immune factors contributes to neuropsychiatric symptom severity. These findings offer new biomarkers to potentially facilitate pharmacotherapeutic development and to increase our understanding of the molecular pathways associated with neuropsychiatric symptoms in adults with or without HCV.

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

Chemoattraction of leukocytes into the brain after induction of middle cerebral artery occlusion (MCAO) increases the lesion size and worsens disease outcome. Our previous studies demonstrated that partial MHC class II constructs can reverse this process. However, the potential application of pMHC to human stroke is limited by the need to rapidly match recipient MHC class II with the β1 domain of the pMHC construct. We designed a novel recombinant protein comprised of the HLA-DRα1 domain linked to MOG-35-55 peptide but lacking the β1 domain found in pMHC and treated MCAO after 4 h reperfusion in humanized DR2 mice. Infarct volumes were quantified after 96 h reperfusion and immune cells from the periphery and CNS were evaluated for expression of CD74 and other cell surface, cytokine and pathway markers. This study demonstrates that four daily treatments with DRα1-MOG-35-55 reduced infarct size by 40 % in the cortex, striatum and hemisphere, inhibited the migration of activated CD11b+CD45high cells from the periphery to the brain and reversed splenic atrophy. Furthermore, DRα1-MOG-35-55 bound to CD74 on monocytes and blocked both binding and downstream signaling of macrophage migration inhibition factor (MIF) that may play a key role in infarct development. The novel DRα1-MOG-35-55 construct is highly therapeutic in experimental stroke and could be given to all patients at least 4 h after stroke onset without the need for tissue typing due to universal expression of DRα1 in humans.

Treatment of experimental stroke with IL-10-producing B-cells reduces infarct size and peripheral and CNS inflammation in wild-type B-cell-sufficient mice

Clinical stroke induces inflammatory processes leading to cerebral and splenic injury and profound peripheral immunosuppression. IL-10 expression is elevated during major CNS diseases and limits inflammation in the brain. Recent evidence demonstrated that absence of B-cells led to larger infarct volumes and CNS damage after middle cerebral artery occlusion (MCAO) that could be prevented by transfer of IL-10(+) B-cells. The purpose of this study was to determine if the beneficial immunoregulatory effects on MCAO of the IL-10(+) B-cell subpopulation also extends to B-cell-sufficient mice that would better represent stroke subjects. CNS inflammation and infarct volumes were evaluated in male C57BL/6J (WT) mice that received either RPMI or IL-10(+) B-cells and underwent 60 min of middle cerebral artery occlusion (MCAO) followed by 96 h of reperfusion. Transfer of IL-10(+) B-cells markedly reduced infarct volume in WT recipient mice when given 24 h prior to or 4 h after MCAO. B-cell protected (24 h pre-MCAO) mice had increased regulatory subpopulations in the periphery, reduced numbers of activated, inflammatory T-cells, decreased infiltration of T-cells and a less inflammatory milieu in the ischemic hemispheres of the IL-10(+) B-cell-treated group. Moreover, transfer of IL-10(+) B-cells 24 h before MCAO led to a significant preservation of regulatory immune subsets in the IL-10(+) B-cell protected group presumably indicating their role in immunomodulatory mechanisms, post-stroke. Our studies are the first to demonstrate a major immunoregulatory role for IL-10(+) regulatory B-cells in preventing and treating MCAO in WT mice and also implicating their potential role in attenuating complications due to post-stroke immunosuppression.

PD-L1 enhances CNS inflammation and infarct volume following experimental stroke in mice in opposition to PD-1

Background

Stroke severity is worsened by recruitment of inflammatory immune cells into the brain. This process depends in part on T cell activation, in which the B7 family of co-stimulatory molecules plays a pivotal role. Previous studies demonstrated more severe infarcts in mice lacking programmed death-1 (PD-1), a member of the B7 family, thus implicating PD-1 as a key factor in limiting stroke severity. The purpose of this study was to determine if this protective effect of PD-1 involves either of its ligands, PD-L1 or PD-L2.

Methods

Central nervous system (CNS) inflammation and infarct volume were evaluated in male PD-L1 and PD-L2 knockout (^-/-) mice undergoing 60 minutes of middle cerebral artery occlusion (MCAO) followed by 96 hours of reperfusion and compared to wild-type (WT) C57BL/6J mice.

Results

PD-L1^-/- and PD-L2^-/- mice had smaller total infarct volumes compared to WT mice. The PD-L1^-/- and to a lesser extent PD-L2^-/- mice had reduced levels of proinflammatory activated microglia and/or infiltrating monocytes and CD4⁺ T cells in the ischemic hemispheres. There was a reduction in ischemia-related splenic atrophy accompanied by lower activation status of splenic T cells and monocytes in the absence of PD-L1, suggesting a pathogenic rather than a regulatory role for both PD-1 ligands (PD-Ls). Suppressor T cells (IL-10-producing CD8⁺CD122⁺ T cells) trafficked to the brain in PD-L1^-/- mice and there was decreased expression of CD80 on splenic antigen-presenting cells (APCs) as compared to the WT and PD-L2^-/- mice.

Conclusions

Our novel observations are the first to implicate PD-L1 involvement in worsening outcome of experimental stroke. The presence of suppressor T cells in the right MCAO-inflicted hemisphere in mice lacking PD-L1 implicates these cells as possible key contributors for controlling adverse effects of ischemia. Increased expression of CD80 on APCs in WT and PD-L2^-/- mice suggests an overriding interaction leading to T cell activation. Conversely, low CD80 expression by APCs, along with increased PD-1 and PD-L2 expression in PD-L1^-/- mice suggests alternative T cell signaling pathways, leading to a suppressor phenotype. These results suggest that agents (for example antibodies) that can target and neutralize PD-L1/2 may have therapeutic potential for treatment of human stroke.

IL-10-producing B-cells limit CNS inflammation and infarct volume in experimental stroke

Clinical stroke induces inflammatory processes leading to cerebral injury. IL-10 expression is elevated during major CNS diseases and limits inflammation in the brain. Recent evidence demonstrated that absence of B-cells led to larger infarct volumes and increased numbers of activated T-cells, monocytes and microglial cells in the brain, thus implicating a regulatory role of B-cell subpopulations in limiting CNS damage from stroke. The aim of this study was to determine whether the IL-10-producing regulatory B-cell subset can limit CNS inflammation and reduce infarct volume following ischemic stroke in B-cell deficient (μMT(-/-)) mice. Five million IL-10-producing B-cells were obtained from IL-10-GFP reporter mice and transferred i.v. to μMT(-/-)mice. After 24 h following this transfer, recipients were subjected to 60 min of middle cerebral artery occlusion (MCAO) followed by 48 h of reperfusion. Compared to vehicle-treated controls, the IL-10(+) B-cell-replenished μMT(-/-)mice had reduced infarct volume and fewer infiltrating activated T-cells and monocytes in the affected brain hemisphere. These effects in CNS were accompanied by significant increases in regulatory T-cells and expression of the co-inhibitory receptor, PD-1, with a significant reduction in the proinflammatory milieu in the periphery. These novel observations provide the first proof of both immunoregulatory and protective functions of IL-10-secreting B-cells in MCAO that potentially could impart significant benefit for stroke patients in the clinic.

Partial MHC class II constructs inhibit MIF/CD74 binding and downstream effects

MIF and its receptor, CD74, are pivotal regulators of the immune system. Here, we demonstrate for the first time that partial MHC class II constructs comprised of linked β1α1 domains with covalently attached antigenic peptides (also referred to as recombinant T-cell receptor ligands - RTLs) can inhibit MIF activity by not only blocking the binding of rhMIF to immunopurified CD74, but also downregulating CD74 cell-surface expression. This bifunctional inhibition of MIF/CD74 interactions blocked downstream MIF effects, including enhanced secretion of proinflammatory cytokines, anti-apoptotic activity, and inhibition of random migration that all contribute to the reversal of clinical and histological signs of EAE. Moreover, we demonstrate that enhanced CD74 cell-surface expression on monocytes in mice with EAE and subjects with multiple sclerosis can be downregulated by humanized RTLs, resulting in reduced MIF binding to the cells. Thus, binding of partial MHC complexes to CD74 blocks both the accessibility and availability of CD74 for MIF binding and downstream inflammatory activity.

Partial MHC/neuroantigen peptide constructs: a potential neuroimmune-based treatment for methamphetamine addiction

Relapse rates following current methamphetamine abuse treatments are very high (∼40-60%), and the neuropsychiatric impairments (e.g., cognitive deficits, mood disorders) that arise and persist during remission from methamphetamine addiction likely contribute to these high relapse rates. Pharmacotherapeutic development of medications to treat addiction has focused on neurotransmitter systems with only limited success, and there are no Food and Drug Administration approved pharmacotherapies for methamphetamine addiction. A growing literature shows that methamphetamine alters peripheral and central immune functions and that immune factors such as cytokines, chemokines, and adhesion molecules play a role in the development and persistence of methamphetamine induced neuronal injury and neuropsychiatric impairments. The objective of this study was to evaluate the efficacy of a new immunotherapy, partial MHC/neuroantigen peptide construct (RTL551; pI-A(b)/mMOG-35-55), in treating learning and memory impairments induced by repeated methamphetamine exposure. C57BL/6J mice were exposed to two different methamphetamine treatment regimens (using repeated doses of 4 mg/kg or 10 mg/kg, s.c.). Cognitive performance was assessed using the Morris water maze and CNS cytokine levels were measured by multiplex assay. Immunotherapy with RTL551 improved the memory impairments induced by repeated methamphetamine exposure in both mouse models of chronic methamphetamine addiction. Treatment with RTL551 also attenuated the methamphetamine induced increases in hypothalamic interleukin-2 (IL-2) levels. Collectively, these initial results indicate that neuroimmune targeted therapies, and specifically RTL551, may have potential as treatments for methamphetamine-induced neuropsychiatric impairments.

Oestrogen treatment of experimental autoimmune encephalomyelitis requires 17β-oestradiol-receptor-positive B cells that up-regulate PD-1 on CD4+ Foxp3+ regulatory T cells

It is now well accepted that sex hormones have immunoregulatory activity and may prevent exacerbations in multiple sclerosis during pregnancy. Our previous studies demonstrated that oestrogen (17β-oestradiol; E(2) ) protection against experimental autoimmune encephalomyelitis (EAE) is mediated mainly through oestrogen receptor-α (ERα) and the membrane receptor G-protein-coupled receptor 30 (GPR30) and is abrogated in the absence of B cells and the co-inhibitory receptor, Programmed Death-1 (PD-1). To critically evaluate the cell source of the E2 and PD-1 co-inhibitory pathways in EAE regulation, we assessed the requirement for ERs on transferred B cells and downstream effects on expression of PD-1/PD-ligand on CD4+ Foxp3+ regulatory T (Treg) cells in B-cell-replenished, E2-treated B-cell-deficient (μMT-/-) mice with EAE. The results clearly demonstrated involvement of ERα and GPR30 on transferred B cells that mediated the protective E2 treatment effect on EAE and further showed an E2-mediated B-cell-dependent up-regulation of PD-1 on CD4+ Foxp3+ Treg cells. These findings identify regulatory B-cell populations as key players in potentiating Treg-cell activity during E2-mediated protection against EAE.

The HLA-DRB1*15:01-restricted Goodpasture's T cell epitope induces GN

Human anti-glomerular basement membrane (GBM) disease strongly associates with HLA-DRB1*15:01. The target autoantigen in this disease is the noncollagenous domain of the α3 chain of type IV collagen, α3(IV)NC1, but critical early T cell epitopes presented by this human MHC class II molecule are unknown. Here, by immunizing HLA-DRB1*15:01 transgenic mice with whole recombinant α3(IV)NC1 and with overlapping α3(IV)NC1 peptides, we defined a HLA-DRB1*15:01-restricted α3(IV)NC1 T cell epitope (α3136-146) with four critical residues. This peptide was not immunogenic in HLA-DRB1*01:01 transgenic or C57BL/6 mice. The T cell epitope is naturally processed from α3(IV)NC1. CD4(+) T cell clones, generated from HLA-DRB1*15:01 transgenic mice and specific for α3136-146, transferred disease into naive HLA-DRB1*15:01 transgenic mice, evidenced by the development of necrotizing crescentic GN, albuminuria, renal impairment, and accumulation of CD4(+) T cells and macrophages in glomeruli. Because Fcγ receptors are implicated in disease susceptibility, we crossed HLA transgenic mice onto an FcγRIIb-deficient background. Immunization with either α3136-146 or α3(IV)NC1 induced GN in HLA-DRB1*15:01 transgenic FcγRIIb-deficient mice, but HLA-DRB1*01:01 transgenic FcγRIIb-deficient mice were unaffected. Taken together, these results demonstrate that the HLA-DRB1*15:01-restricted T cell epitope α3136-146 can induce T cell responses and injury in anti-GBM GN.

PD-1 Interaction with PD-L1 but not PD-L2 on B-cells Mediates Protective Effects of Estrogen against EAE

Increased remissions in multiple sclerosis (MS) during late pregnancy may result from high levels of sex steroids such as estrogen and estriol. Estrogen (E2=17β-estradiol) protects against experimental autoimmune encephalomyelitis (EAE), but the cellular basis for E2-induced protection remains unclear. Treatment with relatively low doses of E2 can protect against clinical and histological signs of MOG-_35-55 induced EAE through mechanisms involving the PD-1 coinhibitory pathway and B-cells. The current study evaluated the contribution of PD-1 ligands, PD-L1 and PD-L2, on B-cells in E2-mediated protection against EAE in WT, PD-L1^-/- and PD-L2^-/- mice. Unlike PD-L2^-/- mice that were fully protected against EAE after E2 treatment, E2-implanted PD-L1^-/- mice were fully susceptible to EAE, with increased numbers of proliferating Th1/Th17 cells in the periphery and severe cellular infiltration and demyelination in the CNS. Moreover, transfer of B-cells from MOG-immunized PD-L1^-/- or PD-L2^-/- donors into E2-preconditioned B-cell deficient μMT^-/- recipient mice revealed significantly reduced E2-mediated protection against EAE in recipients of PD-L1^-/- B-cells, but near-complete protection in recipients of PD-L2^-/- B-cells. We conclude that PD-1 interaction with PD-L1 but not PD-L2 on B-cells is crucial for E2-mediated protection in EAE and that strategies that enhance PD-1/PD-L1 interactions might potentiate E2 treatment effects in MS.

Intrastriatal B-cell administration limits infarct size after stroke in B-cell deficient mice

Recent evidence emphasizes B-cells as a major regulatory cell type that plays an important role in limiting the pathogenic effects of ischemic stroke. The aim of the current study was to extend this initial observation to specifically examine the infiltration of regulatory B-cells and to determine if the effect of B-cells to limit the inflammatory response to cerebral ischemia is mediated by their action centrally or peripherally. Our data demonstrate the increased presence of a regulatory B-cell subset in the affected hemisphere of wild-type mice after middle cerebral artery occlusion (MCAO). We further explored the use of a novel method of stereotaxic cell delivery to bypass the blood brain barrier (BBB) and introduce CD19(+) B-cells directly into the striatum as compared to peripheral administration of B-cells. Infarct volumes after 60 minutes of MCAO and 48 hours of reperfusion were determined in B-cell deficient μMT( -/- ) mice with and without replacement of either B-cells or medium. Infarct size was significantly decreased in cerebral cortex after intrastriatal transfer of 100,000 B-cells to μMT(-/-) mice vs. controls, with a comparable effect on infarct size as obtained by 50 million B-cells transferred intraperitoneally. These findings support the hypothesis that B-cells play a protective role against ischemic brain injury, and suggest that B-cells may serve as a novel therapeutic agent for modulating the immune response in central nervous system inflammation after stroke.