Insights into Acinetobacter baumannii protective immunity

Acinetobacter baumannii is a nosocomic opportunistic Gram-negative bacteria known for its extensive drug-resistant phenotype. A. baumannii hospital-acquired infections are major contributors to increased costs and mortality observed during the COVID-19 pandemic. With few effective antimicrobials available for treatment of this pathogen, immune-based therapy becomes an attractive strategy to combat multi-drug resistant Acinetobacter infection. Immunotherapeutics is a field of growing interest with advances in vaccines and monoclonal antibodies providing insight into the protective immune response required to successfully combat this pathogen. This review focuses on current knowledge describing the adaptive immune response to A. baumannii, the importance of antibody-mediated protection, developments in cell-mediated protection, and their respective therapeutic application going forward. With A. baumannii’s increasing resistance to most current antimicrobials, elucidating an effective host adaptive immune response is paramount in the guidance of future immunotherapeutic development.

The role of tumor necrosis factor receptor 2 in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune neuroinflammatory disease that affects over 2 million people globally. HLA-DR2b is a major histocompatibility complex (MHC) locus in humans responsible for antigen-specific immune responses. HLA-DR2b (DRB1*15:01) is a major genetic risk factor for MS. Experimental autoimmune encephalomyelitis (EAE) is the animal model for MS and can provide insights into the mechanisms behind MS pathogenicity. Tumor necrosis factor receptor 2 (TNFR2) was suspected to control EAE severity by altering regulatory T cell (Treg) function and impairing remyelination. In the absence of TNFR2, mice expressing the human DR2b allele and lacking mouse MHC II develop progressive EAE upon adoptive transfer of myelin oligodendrocyte glycoprotein (MOG)-reactive CD4 T cells. These mice show altered Treg phenotype, including decreased expression of Helios, a marker of thymic Tregs, by splenic Tregs from DR2bΔR2 mice compared with DR2b mice. However, it remains unclear how the presence or absence of TNFR2 alters the expression of specific protective genes in both astrocytes and Tregs in the context of EAE. Using the DR2bΔR2 and DR2b mouse models, we investigated the impact of TNFR2 on protective astrocyte subsets and regulatory T cells by single-cell RNA sequencing (scRNA-seq) in the context of both active and adoptive transfer EAE. Our results elucidate mechanisms underlying the protective function TNFR2 via modulating astrocyte and regulatory T cell function in EAE. Our results may aid in the development of new treatments for MS.

Supported by grant 1RO1NS117742 from the NIH/NINDS (T.G.F.) and by NIH/NIGMS RISE grant GM60655 (BB).

The role of ERK2 in dendritic cell function

Dendritic cells (DCs) are an important link between the innate and adaptive immune systems, specifically by serving as key regulators of T cell-dependent (TD) immune responses. In DCs, several processes critical for initiating TD immune responses, such as migration, provision of costimulatory signals, and antigen uptake and presentation, utilize the mitogen-activated protein kinase (MAPK) signaling pathway. The dysregulation of these processes can result in the aberrant activation of autoreactive CD4+ T cells, resulting in autoimmune disease. Extracellular signal-regulated kinase 1 and 2 (ERK1/2) are key effectors of the MAPK pathway, and while ERK1 has been shown to be a critical regulator of DC migration and TLR-induced IL-10 secretion, the function of ERK2 remains unknown. Preliminary data has shown that Erk2Δ bone marrow-derived DCs (BMDCs), as well as Erk2Δ splenic DCs, exhibit altered expression of surface markers associated with T cell costimulation, antigen presentation, and migration compared with DCs from littermate control. Taken together, this suggests that ERK2 plays a unique role in the regulation of several DC functions, potentially opening a new approach to treating CD4+ T cell-mediated autoimmune diseases.

Supported by grant R21AI44731 from the NIH/NIAID (TGF)

The Contribution of Connexin 43 in Choroid Plexus to Experimental Autoimmune Encephalomyelitis

Multiple Sclerosis (MS) is the most common progressive neurologic disease among young adults worldwide; yet the pathogenesis remains poorly understood. The myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalitis (EAE) in mice is a robust model and has been extensively used to understand the pathophysiology of MS. The expression of connexin 43 (CX43), a gap junction protein, has been shown to be enhanced in the choroid plexus during the development of acute EAE, with significantly increased CX43 expression at the peak of the disease. However, the contribution of such increased CX43 expression to the development of EAE has yet to be fully characterized. Using the Cre-Lox platform, we generated mice with conditional deletion of CX43 in the ciliated columnar epithelium of the choroid plexus (Foxj1Cre-CX43 KO mice; referred to as CX43 KO mice hereafter). We employed the MOG-induced EAE model in both male and female CX43 KO mice to understand the role of CX43 in the pathogenesis of EAE. Male CX43 and WT mice displayed comparable peak EAE clinical disease scores of 1.83±0.33 and 1.75±0.66, respectively. Female CX43 KO, however, displayed a significantly reduced peak EAE clinical disease score of 0.33±0.24 compared to 1.15±0.39 in female WT animals. These results suggest a role for CX43 in the ciliated columnar epithelium of choroid plexus to the development of EAE in female, not male, mice and underscore the need for further exploration of mechanism(s) underpinning the role of CX43 in the pathogenesis of EAE.

T cell cooperation in the induction of autoimmunity in a murine model of multiple sclerosis

Multiple sclerosis (MS) is a T cell-driven autoimmune disease. There are many unknowns regarding the disease etiology and pathogenesis. Importantly, the mechanisms of peripheral tolerance and dysregulation of pathogenic mechanisms are poorly understood. It is known that patients with MS exhibit myelin reactive T cells in the blood; however healthy controls also show myelin reactive T cells in the blood. Additionally, T cells from patients with MS react to many different myelin peptides. Current human studies do not support that patients exhibit large populations of T cells specific for a single myelin-antigen responsible for the induction of autoimmune pathology. In contrast, a quorum of several low avidity autoreactive T cells specific for one epitope might suffice to induce autoimmunity. We hypothesized that a quorum could be established and induce autoimmunity by small numbers of antigen-specific T cells recognizing different myelin antigen peptides. We found that disease in the experimental autoimmune encephalomyelitis (EAE) model of MS can be initiated by the cooperation of small numbers of myelin peptide-specific T cells reactive against different myelin epitopes. These results support the hypothesis that a quorum of autoreactive T cells could suffice to initiate autoimmune disease. We have developed a system whereby T cells of different antigen specificities can be traced in order to track the dynamics and kinetics of those T cells in disease initiation and progression. The results of this study provide further insights into the dynamic interactions between T cells of different antigen specificities.

Identification of markers of relapse in EAE using high-resolution quantitative mass spectrometry

Approximately 85 percent of individuals newly diagnosed with multiple sclerosis have the relapsing-remitting form of the disease characterized by attacks of neurologic symptoms that are unpredictable in occurrence and duration. Currently there are no clinically available biomarkers predictive of relapse. To address this need, we investigated CNS proteome changes over the disease course of relapsing-remitting experimental autoimmune encephalomyelitis (EAE) in SJL mice as a preclinical model of the disease. Using a high-throughput quantitative preparation technique and high-resolution Bruker timsTOF mass spectrometry, we were able to identify thousands of unique proteins at each disease timepoint. Principal component analysis of protein expression confirmed that the remission and relapse phases of disease cluster independently, indicating distinguishable variation in protein expression profiles between the two disease states. Importantly, statistical testing identified proteins with differential expression in the CNS at different stages of disease, several of which are CNS specific. We are seeking to detect corollary changes in these CNS-specific proteins in the serum, pointing to a minimally invasive means of monitoring disease progress and measuring drug efficacy. Our study will validate homologous human biomarkers to guide treatment in individual patients and allow for proactive therapeutic intervention. Furthermore, our results may provide insights into mechanisms that contribute to disease pathology and offer novel therapeutic targets.

IFN-γ-induced nitric oxide leads to inhibition of Th17 differentiation via induction of iNOS and nitration of ROR-γ T

Elucidating the molecular mechanisms involved in pleotropic cytokine signaling can lead to novel treatment approaches for autoimmune diseases that target proinflammatory functions while maintaining immune-regulatory functions. To that end, we sought to further investigate the immune-regulatory roles of the pleotropic cytokine IFN-γ. Previous studies demonstrated that IFN-γ prevents the differentiation of pathogenic Th17 cells. In addition, nitric oxide generated via inducible nitric oxide synthase (iNOS) prevents differentiation of Th17 cells by nitration of ROR-γT. However, it remains unresolved whether IFN-γ prevents Th17 differentiation directly via inducing nitric oxide (NO) and nitration of ROR-γT. In line with previous observations, we found an increase in the frequency of autoreactive Th17 cells and a decrease in iNOS expression and NO in the absence of IFN-γ in mice with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Additionally, the increase in Th17 cells in the absence of IFN-γ was reversible both in vitro and in vivo with treatment with a NO donor. This indicates a role for IFN-γ in inhibiting the differentiation of Th17 cells via iNOS-derived NO. We are currently elucidating the underlying mechanisms of NO mediated suppression and the molecular link between ROR-γt-nitration and decreased Th17 differentiation by flow cytometry, single-cell western blotting of key transcription factors, and in vivo adoptive transfer studies. Our studies may lead to a better understanding of the role of IFN-g and NO/iNOS axis in Th17 cell differentiation and autoimmune diseases.

Identification of molecules associated with disease progression of autoimmune myocarditis to dilated cardiomyopathy

Myocarditis is an inflammatory disease characterized by immune infiltrates into the myocardium. In many patients, the disease progresses to a chronic phase dilated cardiomyopathy (DCM) in which there is extensive fibrosis leading to ventricular dilation and impaired cardiac function. Less than 50% of these patients survive more than 5 years. Immunosuppressive treatments such as corticosteroids (CSs) are effective in managing the acute phase of the disease, but do not prevent progression to the DCM. Using the experimental autoimmune myocarditis (EAM) animal model, we previously demonstrated that the inflammatory cytokine macrophage migration inhibitory factor (MIF) plays a role in resistance to CS treatment. MIF knockout mice were treated with the corticosteroid Dexamethasone (Dex) and proved to be resistant to both EAM and DCM. We also observed that treatment with MIF inhibitors and Dex decreased the expression of chemokines and adhesion molecules and implicated these molecules in the progression of disease. Within these, osteopontin (OPN), a powerful chemoattractant, was downregulated. We hypothesized that OPN plays a role in the disease process and investigated its role in EAM and DCM using OPN knockout mice. Our results show that OPN knockout mice developed EAM, but that progression to DCM was impaired. Furthermore, we observed a decrease in CD45+CD133+ fibroblast progenitor cells infiltrating the myocardium in the absence of OPN, which could contribute to attenuated disease in KO mice. This study may provide insights into the mechanisms driving progression of EAM to DCM and point to potential therapeutic targets.

A modified method for rapid quantification of Chlamydia muridarum using Fluorospot

Although manual enumeration of Chlamydia inclusion forming units is the most widely accepted means of quantification in the field, it is both time consuming and subject to inherent investigator bias. We report here a rapid, i.e., minutes vs. hours, modified automated Fluorospot means of assessment that is linear (<1200 dots per well). Because the Fluorospot enumerated tissue culture plate/well can also be quantified using traditional manual counting, newly derived Fluorospot data can easily be compared to previously established manual enumeration data requiring no new reference norms.

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Concurrent enumeration of chlamydial IFU using automated and manual methods of counting on same tissue culture plate.

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Rapid method of counting chlamydial IFU reducing time from hours to minutes.

Identification of markers of relapse in a relapsing-remitting mouse model of multiple sclerosis

Approximately 85 percent of individuals newly diagnosed with multiple sclerosis have the relapsing-remitting form of the disease characterized by attacks of neurologic symptoms that are both unpredictable in occurrence and duration. The lack of markers that reliably predict the occurrence of multiple sclerosis relapses hinders the ability for proactive therapeutic intervention. To address the urgent need for biomarkers of relapse we investigated proteome changes over the disease course of relapsing-remitting experimental autoimmune encephalomyelitis (EAE) in SJL mice as a preclinical model of the disease using a high-throughput quantitative proteomic technique. In this study, we utilized this established proteomic technique as well as bioinformatics tools to prioritize key proteins that were expressed differentially at different stages of disease including remission and relapse. Principal component analysis of protein expression shows that the remission and relapse phases of disease cluster separately, indicating distinguishable variation between the two disease states. Importantly, statistical testing identified proteins with differential expression in the CNS at different stages of disease, several of which are CNS specific. We are seeking to detect corollary changes in these CNS-specific proteins in the serum, pointing to a minimally invasive means of monitoring disease progress and measuring drug efficacy. Our studies will provide proof-of-concept for identifying homologous human biomarkers to guide treatment in individual patients. Furthermore, our results may provide insights into mechanisms that contribute to disease pathology and offer additional therapeutic targets.

The role of ERK2 in germinal center B cell selection

The regulation of B cell activation and survival is a crucial control point for the maintenance of B cell tolerance in the germinal center (GC) and involves the coordination of several intracellular signaling pathways. Dysregulation of these pathways can lead to the production and survival of autoreactive memory B cells and plasma cells (PCs), resulting in autoimmune disease. The mitogen-activated protein kinase (MAPK) pathway is involved in the transduction of stimulating and apoptotic signals such as those received through the B cell receptor (BCR) and the Fas receptor (CD95), respectively. Extracellular signal regulated kinases 1 and 2 (ERK1/2), important effectors of this pathway, play a major role in B cell activation and survival. Though ERK2 specifically regulates the pro-apoptotic protein, Bmf, its role in regulating GC B cell selection is unknown. Our lab has developed a novel mouse model in which the deletion of Erk2 is accompanied by the expression of the fluorescent reporter protein, eYFP, allowing us to identify and isolate viable Erk2Δ B cells using flow cytometry. Preliminary data using this model has shown that peripheral Erk2Δ B cells express several surface markers associated with follicular T helper cell interactions and immunoglobulin class switching, such as DEC205 and CD80, respectively. Thus we hypothesize that ERK2 is a critical regulator of GC B cell selection. We are currently investigating the ability of Erk2Δ B cells to respond to various activating stimuli in vitro as well as to differentiate into antigen-specific PCs. Our results will contribute to a better understanding of the molecular programs involved in B cell selection, potentially offering new approaches to treating B cell-driven autoimmune diseases.

Small numbers of T cells specific to different myelin-antigens cooperate to induce autoimmunity in a murine model of multiple sclerosis

T cells play a crucial role in many autoimmune diseases including multiple sclerosis (MS). Despite this, mechanisms of peripheral tolerance and dysregulation of these mechanisms during autoimmunity remain elusive. Myelin-reactive T cells are present in the blood of both healthy controls and patients with MS and T cells from patients with MS react to many different myelin peptides. The strongest genetic risk factor for developing MS is the HLA-DRB1*1501 haplotype, indicating that peptide binding to this MHC aids in disease induction. It is unlikely and not supported by current human studies that patients exhibit large populations of T cells specific for a single myelin-antigen. In contrast, a quorum of 2–5 low avidity autoreactive T cells specific for one epitope might suffice to induce autoimmunity. We hypothesized that a quorum could be established and induce autoimmunity by small numbers of antigen-specific T cells recognizing different myelin antigen peptides, particularly in genetically susceptible individuals. We utilized wild-type C57BL/6 mice and transgenic mice expressing the human MHC HLA-DRB1*1501 allele to assess the effect of inducing experimental autoimmune encephalomyelitis (EAE), the murine model of multiple sclerosis, with low numbers of different myelin peptide-specific T cells or myelin peptides at suboptimal doses. In this proof-of-principle study, we found that EAE can be initiated by the cooperation of small numbers of myelin peptide-specific T cells reactive against different myelin epitopes. The results support the hypothesis that a quorum of T cells could be reached by multiple antigen-specific T cells and could suffice to initiate autoimmune disease.

The role of ERK2 in bone marrow-derived dendritic cells development and function

Dendritic cells (DCs) regulate antigen-specific T cell responses by providing stimulatory or inhibitory signals through surface receptors and cytokines, the expression of which relies on the mitogen-activated protein kinase (MAPK) signaling pathway. In lymphocytes, the MAPK pathway is involved in differentiation, proliferation, and survival, using extracellular signal regulated kinases 1 and 2 (ERK1/2) as primary effector molecules. Importantly, ERK1 and ERK2 are not functionally redundant, despite 85% sequence homology. The role of ERK1 in DCs has been explored, however that of ERK2 remains unknown due to the lack of Erk2 Δ transgenic models. Our lab has developed a novel mouse model in which Cre-mediated deletion of Erk2 is accompanied by the expression of an eYFP reporter gene, allowing us to identify and isolate viable Erk2 Δ cells using flow cytometry. Preliminary data has shown that DCs cultured from bone marrow progenitor cells (BMDCs) exhibit altered expression of several surface receptors associated with both antigen presentation and T cell stimulation when compared to wild type BMDCs. We therefore hypothesize that ERK2 deficiency will significantly affect the ability of DCs to prime naïve T cells. We are currently investigating the functional competency of these BMDCs regarding migration, cytokine secretion, and antigen presentation. Our results will help to elucidate the role ERK2 plays in regulating DC function, potentially offering a new approach to treating T cell-driven diseases.

Protective effect of IFN-γ during experimental autoimmune encephalomyelitis is associated with the induction of inducible nitric oxide synthase

Over 2.3 million people are affected by multiple sclerosis (MS), the most common demyelinating autoimmune disease of the CNS. The relapsing-remitting form of MS is the most common initial diagnosis; however, the vast majority of patients will eventually develop secondary-progressive MS. The mechanisms that contribute to the progression of MS are largely unknown. IFN-γ, a pro-inflammatory cytokine, has long been implicated in the pathogenesis of MS and its murine model, experimental autoimmune encephalomyelitis (EAE); however, protective functions have also been demonstrated. Previous studies in our lab revealed mice lacking IFN-γ signaling developed severe and progressive EAE due to an increased presence of myelin debris and lipid peroxidation in the CNS. Recently, we identified a significant increase of inducible nitric oxide synthase (iNOS) production in the brains of WT as compared with IFN-γR−/− mice at peak of disease by qRT-PCR. iNOS is an inducible enzyme that produces nitric oxide (NO) upon activation by immunological stimuli such as IFN-γ and LPS. There are conflicting data on the role of iNOS in the pathogenesis of EAE. Our preliminary findings indicate macrophages are the primary contributors to iNOS expression during disease progression. To further explore the role of iNOS in disease progression, we are studying the underlying mechanisms, key molecules involved in this process, and the effects of treatment with iNOS inhibitors on disease course, general pathology and biochemical composition of the CNS. Our results will contribute to a better understanding of the underlying mechanisms and may lead to new treatments to prevent progression of MS.

The role of ERK2 in germinal center B cell selection

The regulation of programmed cell death is a crucial control point for the maintenance of B cell tolerance in the germinal center (GC) and involves the coordination of several intracellular signaling pathways. Dysregulation of these pathways can lead to the survival of autoreactive B cells, resulting in autoimmune disease. The mitogen-activated protein kinase (MAPK) pathway is involved in the transduction of both survival and apoptotic signals received through the B cell receptor (BCR) and the Fas receptor (CD95), respectively. Extracellular signal regulated kinases 1 and 2 (ERK1/2) are important effectors of this pathway and play a major role in the B cell selection process. Though it is known that ERK2 specifically regulates the pro-apoptotic protein, Bmf, its function in GC B cells remains poorly understood. Our lab has developed a novel mouse model in which the deletion of Erk2 is accompanied by the expression of the fluorescent reporter protein, eYFP, allowing us to identify and isolate viable Erk2 Δ B cells using flow cytometry. Preliminary data using this model has shown that Erk2Δ B cells exhibit impaired survival ex vivo and express several activation-associated surface markers. This suggests that ERK2 plays a major role in facilitating GC B cell selection. Thus we hypothesize that Erk2 Δ B cells are impaired in their ability to participate in the GC reaction. We are currently investigating the ability of Erk2 Δ B cells to respond to activating and pro-apoptotic stimuli in vitro as well as to differentiate in to antibody-secreting plasma cells. Our results will contribute to a better understanding of the molecular programs involved in B cell selection, potentially offering new approaches to treating B cell-driven autoimmune diseases.

Tumor necrosis factor receptor 2 promotes neuroprotection during chronic autoimmune neuroinflammation

Multiple sclerosis (MS) is an inflammatory autoimmune disorder affecting the central nervous system (CNS) which affects over 400,000 Americans and over 2.5 million people worldwide. Although most patients are initially diagnosed with relapsing-remitting MS, the majority of these patients later develop a chronic-progressive form of MS, for which there is no well-established mouse model. The most common genetic factor associated with MS susceptibility is the Human Leukocyte Antigen (HLA)-DR2b haplotype. Additionally, studies in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS, showed that lack of TNF signaling through its receptor TNFR2 leads to disease exacerbation and severe demyelination. Here, we developed a mouse model which expresses HLA-DR2b and lacks TNFR2, designated DR2bΔR2. Strikingly, DR2bΔR2 mice develop progressive EAE with pathology and clinical features observed in progressive MS patients. Adoptive transfer studies revealed that the clinical phenotype of EAE in DR2bΔR2 mice are largely dependent on TNFR2 expression in the CNS. Subsequently, we showed that DR2bΔR2 mice have a significant increase of lesions in the cerebellum, associated with reduced of oligodendrocyte progenitor cells (OPC) recruitment or function. Moreover, we showed that DR2bΔR2 mice are presented with chronic astrogliosis in demyelinating lesions. Our studies provide key insights into CNS repair and regulatory mechanisms controlled by TNFR2 during neuroinflammation and provide novel therapeutic strategies for treating progressive MS.

Differential expression of CNS-specific proteins in progressive EAE point to potential biomarkers for progressive MS

The lack of reliable markers for assessing the progression of multiple sclerosis (MS) from the relapsing-remitting to the secondary progressive form hinders the ability for therapeutic intervention and results in continued physiological deterioration. To begin to address the urgent need for biomarkers of progressive MS we investigated proteome changes over the disease course of progressive experimental autoimmune encephalomyelitis (EAE) in NOD mice as a preclinical model of the disease using a high-throughput quantitative proteomic technique pioneered in our lab. In this study, we utilized this established proteomic technique as well as bioinformatics tools to prioritize key proteins whose expression level in the CNS correlated specifically with the progressive phase of disease in the NOD EAE model. Hierarchical clustering of timepoints indicate that samples cluster based on progression of disease. Specifically, late time points cluster separately from naïve and peak time points. Importantly, statistical testing identified proteins with differential expression in the CNS of mice across the time course of NOD EAE, several of which are CNS specific. We are seeking to detect corollary changes in these CNS-specific proteins in the serum, pointing to a minimally invasive means of monitoring disease progress and measuring drug efficacy. Our studies will provide proof-of-concept for identifying homologous human biomarkers to guide treatment in individual patients. Furthermore, our results may provide insights into mechanisms that contribute to disease pathology and offer additional therapeutic targets for slowing the progression of MS.

Aire is not essential for regulating autoimmune pathology in mice transgenic for human autoimmune-disease associated MHC class II genes HLA-DR2b and HLA-DR4

The human MHC class II molecules HLA-DR2b (DRB1*1501) and HLA-DR4 (DRB1*0401) are strongly linked to increased susceptibility to autoimmune diseases, such as multiple sclerosis (MS) and rheumatoid arthritis (RA). However, their contribution to disease pathogenesis is not completely understood. Conceivably, autoimmune disease-associated HLA alleles could shape the repertoire of pathogenic T cells via central or peripheral tolerance. The ectopic expression of tissue-specific antigens promoted by the autoimmune regulator (AIRE) is thought to play a critical role in central tolerance. Aire knockout mice (Aire−/−) develop spontaneous autoimmune pathology characterized by multi-organ lymphocytic infiltrates. Aire deficiency in humans causes multi-organ autoimmune conditions observed in autoimmune polyendocrinopathy syndrome type 1 (APS I). We wanted to investigate whether lack of Aire expression promoted spontaneous MS- or RA-like autoimmune pathology in HLA-DR2b or HLA-DR4 transgenic (tg) mice. We observed that Aire-deficiency modestly enhanced experimental autoimmune encephalomyelitis (EAE) in HLA-DR tg mice, but did not lead to spontaneous neuroinflammation or arthritis. Our results suggest that Aire has a mild and non-essential effect in restraining the autoimmune response in the context of autoimmune disease-associated human HLA alleles.

T cells directed against different myelin antigen epitopes cooperate to induce autoimmune encephalomyelitis in mice

Multiple Sclerosis (MS) is the most common demyelinating autoimmune disease of the central nervous system (CNS). Important insights have emerged into the pathogenic mechanisms that drive the inflammatory events and demyelination in MS, however, much less is known about the events initiating this disease. The murine model of MS, experimental autoimmune encephalomyelitis (EAE), is usually induced through injection with a high dose of single immunodominant peptides found on the myelin sheath of the CNS. Low doses of single peptide do not induce EAE or result in very low disease incidence. In individual MS patients, autoimmune T cell-reactivity is usually directed against multiple myelin antigen epitopes and fluctuates significantly over the course of disease. Thus, we hypothesize that MS is triggered by the emergence of autoreactive T cells directed against multiple myelin epitopes, which together synergize to induce the disease. To test this concept in an animal model of EAE, we explored the effect of induction of EAE using combinations of low dose peptides akin to a “multiple hit” mechanism implicated in other disease conditions. We found that EAE can be induced through the immunization of mice with a combination of low dose myelin peptides from different myelin proteins, which individually are suboptimal to induce disease. The disease observed after multi-peptide immunization is comparable or more severe than with optimal doses of peptide traditionally used to induce EAE. This research provides new insights into the potential mechanisms underlying the induction of MS and could lead to novel approaches for immunotherapy.

IFN-γ regulates transcription of key molecules to prevent progressive experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is the most common disabling neurological condition of young adults. Most patients are initially diagnosed with relapsing-remitting MS. Problematically; 10 years after diagnosis approximately 60% of MS patients will have converted from the relapsing-remitting form of MS to secondary-progressive MS despite treatments. IFN-γ, a well-studied pro-inflammatory cytokine, has long been implicated in the pathogenesis of MS and its preclinical model, experimental autoimmune encephalomyelitis (EAE), and is often suppressed during treatments for MS. However, previous studies in our lab revealed that mice lacking IFN-γ signaling developed severe and progressive EAE due to increased presence of myelin debris and lipid peroxidation in the CNS, the cause of which is yet to be fully elucidated. We hypothesize that IFN-g prevents disease progression in this progressive EAE model by regulating the expression of molecules that promote the resolution of lipid peroxidation and clearance of myelin debris in the CNS during EAE. We identified a number of key molecules associated with lipid peroxidation which are temporally dysregulated in the absence of IFN-gR using qRT-PCR. To discover additional molecules involved in disease progression we have performed comprehensive RNA sequencing on the CNS of IFN-gR−/− vs WT mice through the course of disease. We will present the result of the analysis of these molecules and supporting studies. The results of our studies will contribute to a more thorough understanding of the underlying mechanisms and may lead to new treatments to prevent progression of MS.

B-cell-targeted therapies in relapsing forms of MS

In recent years, there has been a significant increase in the therapeutic options available for the management of relapsing forms of MS. Therapies primarily targeting B cells, including therapeutic anti-CD20 monoclonal antibodies, have been evaluated in phase I, phase II, and phase III clinical trials. Results of these trials have shown their efficacy and relatively tolerable adverse effect profiles, suggesting a favorable benefit-to-risk ratio. In this review, we discuss the pathogenic role of B cells in MS and the rationale behind the utilization of B-cell depletion as a therapeutic cellular option. We also discuss the data of clinical trials for anti-CD20 antibodies in relapsing forms of MS and existing evidence for other B-cell–directed therapeutic strategies.

A serum CNS-specific protein fingerprint predictive of clinical relapses and disease development of multiple sclerosis

There is a critical need in MS to develop biomarkers to improve early diagnosis, predict imminent disease relapses, and optimize treatment responses. In MS, central nervous system (CNS) inflammation results in damage to neuronal tissues and disruption of blood-brain barrier integrity, and ultimately to leakage of CNS-specific proteins (CSPs) into serum. Therefore, altered serum levels of CSPs could be promising biomarkers of MS. Based on our previous discovery of CSP expression waves in brain tissue of mice with experimental autoimmune encephalomyelitis (EAE), a preclinical model for human MS, we investigated a subset of CSPs which have human-homologs in longitudinal serum specimens from individual mice in this model. Herein, we establish a pre-onset serum CSP expression wave that enabled prediction of clinical onset of EAE and stratification of subjects into diseased versus healthy. Importantly, we demonstrate that the pre-onset serum CSP wave was not affected by adjuvants and microbial infection, thereby has high sensitivity and specificity for a neuroinflammatory disease. Moreover, we identify differences in serum protein expression between active and passive immunization of EAE revealing hitherto not appreciated differences for disease induction mechanisms. The results provide proof of concept for the development serum CSP waves as biomarkers of MS, specifically for early detection and prediction of the onset of clinical relapse.

Identification of CNS-specific biomarkers for monitoring the progression of multiple sclerosis

There are currently no reliable methods for assessing the progression of multiple sclerosis (MS) from the relapsing-remitting to the secondary progressive form. This gap in knowledge hinders the ability for therapeutic intervention and results in continued relapses and physiological deterioration. To begin to address the urgent need for biomarkers of progressive MS we investigated proteome changes over the disease course of progressive experimental autoimmune encephalomyelitis (EAE) in NOD mice as a preclinical model of the disease. Our lab has pioneered a high-throughput quantitative proteomic technique, which we have previously used to quantify expression levels of central nervous system (CNS) proteins over the course of monophasic EAE in C57BL/6 mice, producing a predictive protein biomarker fingerprint for clinical relapses. In this study, we utilized this established proteomic technique as well as bioinformatics tools to prioritize key proteins whose expression level in the CNS correlated specifically with the progressive phase of disease in the NOD EAE model. Bioinformatics analysis identified 11 proteins with differential expression in the CNS of mice across the time course of NOD EAE, three of which are CNS specific. We are seeking to detect corollary changes in these three CNS-specific proteins in the serum, pointing to a minimally invasive means of monitoring disease progress and measuring drug efficacy. Our studies will provide a proof-of-concept for identifying homologous human biomarkers to guide treatment in individual patients. Furthermore, our results may provide insights into mechanisms that contribute to disease pathology and offer additional therapeutic targets for slowing the progression of MS.

Mechanisms by which IFN-γ mitigates lipid peroxidation that leads to progressive experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is the most common demyelinating autoimmune disease of the central nervous system affecting over 2.3 million people worldwide. Although most patients are initially diagnosed with relapsing-remitting MS, the vast majority of these will eventually develop progressive MS. Importantly, the mechanisms that contribute to the progression of MS are largely unknown. IFN-γ, a well-studied pro-inflammatory cytokine, has long been implicated in the pathogenesis of MS and its preclinical model, experimental autoimmune encephalomyelitis (EAE). Although pro-inflammatory, disease-promoting effects are well documented for IFN-γ, paradoxically, protective functions have also been demonstrated for this cytokine. We are interested in protective mechanisms of IFN-γ. Previous studies in our lab revealed that mice lacking IFN-γ signaling developed severe and progressive EAE due to increased presence of myelin debris and lipid peroxidation in the CNS, the cause of which is yet to be elucidated. We hypothesize that IFN-γ helps regulate expression of scavenger receptors, antioxidant molecules, and pro-oxidant molecules in order to promote resolution of lipid peroxidation and clearance of myelin debris in the CNS during EAE. We are currently investigating key scavenger receptor, antioxidant, and pro-oxidant molecule expression in IFN-γR−/− vs. wild type mice during EAE. Our results will contribute to a better understanding of the underlying mechanisms and may lead to new treatments to prevent progression of MS.

Molecular mechanisms promoting progression of autoimmune myocarditis to dilated cardiomyopathy

Myocarditis is an inflammatory disease of the myocardium, described by infiltration of immune cells and cardiomyocyte necrosis. It is a major cause of sudden death in young adults. Patients often progress to a more severe form of the disease termed dilated cardiomyopathy (DCM). It is characterized by extensive fibrosis leading to impaired cardiac function. Immunosuppressive treatments with corticosteroids (CSs) have not been effective in preventing the disease. We hypothesized that macrophage migration inhibitory factor (MIF), being the only known pro-inflammatory cytokine induced by CSs may play a role in resistance to CSs. Also, MIF counter-regulates CS-mediated immunosuppression. Using the experimental autoimmune myocarditis (EAM) animal model, we observed that MIF−/− mice treated with Dexamethasone (Dex) were highly resistant to EAM and progression to DCM. Furthermore, from a translational approach, treatment using small molecule inhibitors of MIF combined with Dex recapitulated this phenotype in wild type mice. We observed that treated mice showed decreased expression of key chemokines and extracellular matrix molecules compared with controls, implicating these molecules in disease progression. Currently, we are investigating these molecules by selectively inhibiting them in order to understand their contribution to disease pathogenesis. We observed that inhibition of CCL2 after, although not prior to establishment of EAM attenuated progression to DCM. Thereby, suggesting that CCL2 is predominantly involved during the fibrotic phase aiding in progression as opposed to the induction phase of the disease. Besides a novel approach to prevent DCM, our studies may provide new insights into the mechanisms driving DCM.

Signaling via TNFR2 mediates CNS remyelination in EAE through regulation of oligodendrocyte progenitor cells

Tumor necrosis factor-alpha (TNF) is a pleiotropic inflammatory cytokine that has been associated with the pathogenesis of several autoimmune diseases, including multiple sclerosis (MS). Consequently, TNF-blocking drugs have been widely used to treat many inflammatory conditions and have proven highly effective. However, treatment of MS patients with anti-TNF drugs leads to disease exacerbation and severe demyelination. This effect has been specifically associated with lack of TNF signaling through its receptor, TNFR2. However, the underlying mechanisms are not fully understood. Experimental autoimmune encephalomyelitis (EAE) is the most common animal model used to study MS. Our lab has recently generated TNFR2−/− DR2b+/+ mice to study the role of TNFR2 signaling in EAE in the context of the HLA-DR2b (DRB1*1501), a haplotype strongly associated with MS. We found that these mice developed progressive EAE characterized by increased demyelinating lesions. Strikingly, this phenotype was not due to lack of TNFR2 expression in T cells, but rather was associated with a decreased numbers of oligodendrocyte progenitor cells (OPCs) in the CNS. Moreover, we demonstrated that TNFR2 signaling is critical for expression of chemokines in the CNS, suggesting its involvement in OPC function and recruitment. Our studies provide key insights into CNS repair and regulatory mechanisms controlled by TNF during inflammation, and this information may help develop novel therapeutic strategies.

Identification of Iguratimod as an Inhibitor of Macrophage Migration Inhibitory Factor (MIF) with Steroid-sparing Potential

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that has been implicated in a broad range of inflammatory and oncologic diseases. MIF is unique among cytokines in terms of its release profile and inflammatory role, notably as an endogenous counter-regulator of the anti-inflammatory effects of glucocorticoids. In addition, it exhibits a catalytic tautomerase activity amenable to the design of high affinity small molecule inhibitors. Although several classes of these compounds have been identified, biologic characterization of these molecules remains a topic of active investigation. In this study, we used in vitro LPS-driven assays to characterize representative molecules from several classes of MIF inhibitors. We determined that MIF inhibitors exhibit distinct profiles of anti-inflammatory activity, especially with regard to TNFα. We further investigated a molecule with relatively low anti-inflammatory activity, compound T-614 (also known as the anti-rheumatic drug iguratimod), and found that, in addition to exhibiting selective MIF inhibition in vitro and in vivo, iguratimod also has additive effects with glucocorticoids. Furthermore, we found that iguratimod synergizes with glucocorticoids in attenuating experimental autoimmune encephalitis, a model of multiple sclerosis. Our work identifies iguratimod as a valuable new candidate for drug repurposing to MIF-relevant diseases, including multiple sclerosis.

Identifying biomarkers for monitoring progression of multiple sclerosis

There are currently no reliable methods for assessing the progression of multiple sclerosis (MS) from the relapsing-remitting to the secondary progressive form. This gap in knowledge hinders the ability for therapeutic intervention and ultimately results in continued relapses and physiological deterioration. To begin to address the urgent need for biomarkers of progressive MS we investigated proteome changes over the disease course of progressive experimental autoimmune encephalomyelitis (EAE) in NOD mice as a preclinical model of the disease. Our lab has pioneered a novel high-throughput quantitative proteomic technique which we used to quantify expression levels of central nervous system (CNS) proteins over the course of monophasic EAE in C57.BL/6 mice. We utilized bioinformatics tools to prioritize key proteins whose expression level correlated specifically with the progressive phase of disease in the NOD EAE model. Importantly, we were able to detect corollary changes in these CNS-specific proteins in the serum, pointing to a minimally invasive means of monitoring disease progress and measuring drug efficacy. Our studies will provide a proof-of-concept for identifying homologous human biomarkers to guide treatment in individual patients. Furthermore, our results may provide insights into mechanisms that contribute to disease pathology and offer additional therapeutic targets for slowing the progression of MS.

ERK2 regulation of mitophagy is important for T cell activation

Critical signals necessary for T cell activation are transduced into the cell, in part, by the MAPK pathway, for which extracellular regulated kinase 2 (ERK2) is a key member. Upon activation, changes to mitochondria location and metabolism mediate T cell priming; however the signaling pathways that modulate mitochondria in T cells are largely unknown. A primary mechanism regulating mitochondria is a form of selective autophagy termed mitophagy. Importantly, ERK2 is required for mitophagy in other cell types and has been shown to co-localize at the autophagosome during formation. These data suggest that ERK2 may have a unique role regulating mitophagy in T cells. Notably, dysregulation of mitochondria in T cells can result in impaired immunity and has also been associated with autoimmune disease.

Here, we investigated the role of ERK2 for mitophagy in CD4+ T cells using a mouse model with T cell-specific deletion of ERK2. Our results show that Erk2−/− CD4+ T cells have impaired autophagosome formation and increased cell death upon activation, a phenotype consistent with mitophagy blockade. Further, we are working to identify key mitophagy proteins that are regulated by ERK2 and to characterize mitochondria signaling metabolites during T cell activation. By elucidating the signaling pathways that connect extracellular immune stimuli with mitochondria regulation, we will obtain important information that may lead to new therapeutic targets for T cell mediated diseases and dysfunction.

Pentraxin 3: an immune modulator of infection and useful marker for disease severity assessment in sepsis

The acute phase protein pentraxin 3 (PTX3) is a pattern recognition receptor involved in regulation of the host immune response. This relatively newly discovered member of the pentraxin superfamily elicits both immunostimulatory and immunoregulatory functions preventing autoimmune pathology and orchestrated clearance of pathogens through opsonization of damage- and pathogen-associated molecular patterns (DAMP/PAMP). Thus, PTX3 has been described as a possible evolutionary precursor to immunoglobulins. While shown to provide protection against specific bacterial and fungal pathogens, persistent elevation of PTX3 levels following initial onset of infection appear to predict poor patient outcome and may contribute to disease sequelae such as tissue damage and coagulopathy. Measurement of PTX3 following onset of sepsis may improve patient risk assessment and thus be useful in guiding subsequent therapeutic interventions including steroidal anti-inflammatory and altered antibiotic therapies. In this review, we summarize the role of PTX3 in inflammatory syndromes and its utility as a marker of sepsis disease severity.

Identifying biomarkers for monitoring disease progression in experimental autoimmune encephalomyelitis (THER7P.942)

Multiple sclerosis (MS) is the most common demyelinating neuroinflammatory disorder which afflicts over 400,000 Americans. Currently, determining clinical or sub-clinical disease progression in MS patients and development of novel treatments has been hampered by the lack of specific and sensitive laboratory tests. Recently, our lab has developed a technique called M2 proteomics, which is a rapid quantitative approach for identifying putative protein biomarkers and therapeutic targets of experimental autoimmune encephalomyelitis (EAE), a commonly used animal model for MS. Notably, we identified several putative-biomarkers which correlate with different stages of monophasic EAE. The objective of this study is to identify protein biomarkers of disease progression in a progressive EAE model using non-obese diabetic (NOD) mice. We hypothesize that during progressive EAE key central nervous system (CNS) disease-specific proteins will be released into blood and changes of these proteins can be used to determine disease progression. Using the progressive NOD EAE model, we determined the expression of putative CNS-specific protein biomarkers by immune assay in brain homogenate and serum longitudinally over the course of disease. We identified several CNS-specific potential biomarkers in serum that correlated with the progression of disease. The results of this study could help development of biomarkers for disease progression and testing of novel treatments for progressive MS.

MIF inhibition as novel treatment for autoimmune myocarditis and dilated cardiomyopathy (THER7P.956)

Myocarditis is an inflammatory disease of the myocardium and a major cause of sudden death in young adults. It is characterized by the presence of immune infiltrates in the myocardium and often progresses to dilated cardiomyopathy (DCM). Despite the inflammatory nature of this autoimmune disease, immunosuppressive treatments with glucocorticoids (GCs) such as dexamethasone (Dex) have not been very effective in preventing myocarditis and progression to DCM. In addition, some patients develop resistance to GCs. We hypothesized that macrophage migration inhibitory factor (MIF) may play a role in resistance to GCs, as it is the only known pro-inflammatory cytokine to be induced by GCs. Importantly, MIF counter-regulates GC-mediated immunosuppression. Using the experimental autoimmune myocarditis (EAM) model, we observed that MIF-/- mice treated with Dex were highly resistant to disease and progression to DCM. In addition, we observe lower expression of CCL3 mRNA in MIF-/- mice treated with Dex compared with wild-type mice during the onset of EAM, which indicates that MIF promotes recruitment of inflammatory cells to the myocardium. Our results suggest that therapeutic inhibition of MIF may increase the efficacy of GC treatment. This study will allow us to better understand the mechanism by which MIF affects treatment of myocarditis by inhibiting the therapeutic effects of GCs.

Identification of predictive protein biomarkers for treatment efficacy and clinical relapses of multiple sclerosis (THER7P.950)

Despite extensive research, MS remains a disease that lacks a definitive prognostic test to predict imminent disease relapses. Thus, patients may undergo years of unnecessary treatments. Additionally, current treatments for MS can produce dramatically different outcomes in different individuals and therefore there is a critical need to develop biomarkers for treatment efficacy and resistance. We have recently developed a novel quantitative proteomics method to measure changes in proteome expression over the course of experimental autoimmune encephalomyelitis (EAE). Our statistical analyses indicate a strong correlation to EAE severity and/or clinical-phase. Interestingly, we revealed characteristic CNS-specific protein expression waves prior to the onset of clinical symptoms. We are currently testing whether these protein expression waves allow us to predict the onset of clinical episodes and forecast the severity of the disease to guide treatment strategies. Additionally, we have identified changes in the CNS proteome that can be measured in serum during EAE that correlate with the therapeutic efficacy of glucocorticoid treatment. Our studies will provide proof-of-principle for developing homologous human biomarkers that may be useful to predict disease onset and treatment efficacy. Finally, the detected changes in the CNS proteome may provide insights into key mechanisms that contribute to the disease pathology and may be useful to develop new therapeutic targets for MS.

Erk2-deficiency impairs the effector function of mature CD4+ T cells (IRM15P.455)

Extracellular signal-regulated kinase 2 (Erk2) is required for CD4+T cell development and positive selection in the thymus, however the role of Erk2 in mature CD4+T cells is unknown. Erk2 is a key player of the mitogen activated protein kinase (MAPK) pathway which, in T cells, transduces crucial signals such as TCR engagement, CD28 co-stimulation, and cytokine binding. Upon activation, these signals are carefully coordinated to initiate gene expression programs, thus directing the expansion and differentiation of Ag-specific cells. The exquisite control of these signaling mechanisms is needed to maintain tolerance; dysregulation can result in inappropriate immune responses. In this study we used a mouse model with T cell-specific deletion of Erk2 to determine the role of Erk2 for CD4+T cell function. Our results show that increased numbers of Erk2∆CD4+T cells from naïve mice express markers for activation (CD25, CD44, and CD69). Further, Erk2∆CD4+T cells are able to survive and expand in vivo and proliferate upon IL-2, IL-7, and IL-15 cytokine stimulation. Importantly however, although the frequency and magnitude of Ag-specific Erk2∆CD4+T cell responses was comparable with controls upon antigen recall, secretion of IFN-g and IL-17 was significantly impaired. As CD4+T cells orchestrate immune responses primarily via cytokine production, our results suggest that Erk2 is required for CD4+T cell effector function.

Body fluid biomarkers in multiple sclerosis: how far we have come and how they could affect the clinic now and in the future

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system, which affects over 2.5 million people worldwide. Although MS has been extensively studied, many challenges still remain in regards to treatment, diagnosis and prognosis. Typically, prognosis and individual responses to treatment are evaluated by clinical tests such as the expanded disability status scale, MRI and presence of oligoclonal bands in the cerebrospinal fluid. However, none of these measures correlates strongly with treatment efficacy or disease progression across heterogeneous patient populations and subtypes of MS. Numerous studies over the past decades have attempted to identify sensitive and specific biomarkers for diagnosis, prognosis and treatment efficacy of MS. The objective of this article is to review and discuss the current literature on body fluid biomarkers in MS, including research on potential biomarker candidates in the areas of miRNA, mRNA, lipids and proteins.

Immunodominant T-cell epitopes of MOG reside in its transmembrane and cytoplasmic domains in EAE

Objective:

Studies evaluating T-cell recognition of myelin oligodendrocyte glycoprotein (MOG) in multiple sclerosis (MS) and its model, experimental autoimmune encephalomyelitis (EAE), have focused mostly on its 117 amino acid (aa) extracellular domain, especially peptide (p) 35-55. We characterized T-cell responses to the entire 218 aa MOG sequence, including its transmembrane and cytoplasmic domains.

Methods:

T-cell recognition in mice was examined using overlapping peptides and intact full-length mouse MOG. EAE was evaluated by peptide immunization and by adoptive transfer of MOG epitope-specific T cells. Frequency of epitope-specific T cells was examined by ELISPOT.

Results:

Three T-cell determinants of MOG were discovered in its transmembrane and cytoplasmic domains, p119–132, p181–195, and p186–200. Transmembrane MOG p119-132 induced clinical EAE, CNS inflammation, and demyelination as potently as p35-55 in C57BL/6 mice and other H-2^b strains. p119-128 contained its minimal encephalitogenic epitope. p119-132 did not cause disease in EAE-susceptible non-H-2^b strains, including Biozzi, NOD, and PL/J. MOG p119-132–specific T cells produced Th1 and Th17 cytokines and transferred EAE to wild-type recipient mice. After immunization with full-length MOG, a significantly higher frequency of MOG-reactive T cells responded to p119-132 than to p35-55, demonstrating that p119-132 is an immunodominant encephalitogenic epitope. MOG p181-195 did not cause EAE, and MOG p181-195–specific T cells could not transfer EAE into wild-type or highly susceptible T- and B-cell–deficient mice.

Conclusions:

Transmembrane and cytoplasmic domains of MOG contain immunodominant T-cell epitopes in EAE. A CNS autoantigen can also contain nonpathogenic stimulatory T-cell epitopes. Recognition that a myelin antigen contains multiple encephalitogenic and nonencephalitogenic determinants may have implications for therapeutic development in MS.

MOG transmembrane and cytoplasmic domains contain highly stimulatory T-cell epitopes in MS

Objective:

Recently, we reported that the 218 amino acid murine full-length myelin oligodendrocyte glycoprotein (MOG) contains novel T-cell epitopes p119-132, p181-195, and p186-200, located within its transmembrane and cytoplasmic domains, and that p119-132 is its immunodominant encephalitogenic T-cell epitope in mice. Here, we investigated whether the corresponding human MOG sequences contain T-cell epitopes in patients with multiple sclerosis (MS) and healthy controls (HC).

Methods:

Peripheral blood T cells from patients with MS and HC were examined for proliferation to MOG p119-130, p181-195, p186-200, and p35-55 by fluorescence-activated cell sorting analysis using carboxylfluorescein diacetate succinimidyl ester dilution assay. Intracellular production of proinflammatory cytokines was analyzed by flow cytometry.

Results:

MOG p119-130, p181-195, and p186-200 elicited significantly greater T-cell responses than p35-55 in patients with MS. T cells from patients with MS proliferated significantly more strongly to MOG p119-130 and p186-200 than did T cells from HC. Further, MOG p119-130–specific T cells exhibited Th17 polarization, suggesting this T-cell epitope may be relevant to MS pathogenesis.

Conclusions:

Transmembrane and cytoplasmic MOG domains contain potent T-cell epitopes in MS. Recognition of these determinants is important when evaluating T-cell responses to MOG in MS and may have implications for development of myelin antigen-based therapeutics.

Small molecule inhibitor of antigen binding and presentation by HLA-DR2b as a therapeutic strategy for the treatment of multiple sclerosis

The strong association of HLA-DR2b (DRB1*1501) with multiple sclerosis (MS) suggests this molecule as prime target for specific immunotherapy. Inhibition of HLA-DR2b-restricted myelin-specific T cells has the potential to selectively prevent CNS pathology mediated by these MHC molecules without undesired global immunosuppression. In this study, we report development of a highly selective small molecule inhibitor of peptide binding and presentation by HLA-DR2b. PV-267, the candidate molecule used in these studies, inhibited cytokine production and proliferation of myelin-specific HLA-DR2b-restricted T cells. PV-267 had no significant effect on T cell responses mediated by other MHC class II molecules, including HLA-DR1, -DR4, or -DR9. Importantly, PV-267 did not induce nonspecific immune activation of human PBMC. Lastly, PV-267 showed treatment efficacy both in preventing experimental autoimmune encephalomyelitis and in treating established disease. The results suggest that blocking the MS-associated HLA-DR2b allele with small molecule inhibitors may be a promising therapeutic strategy for the treatment of MS.

Human aquaporin 4281-300 is the immunodominant linear determinant in the context of HLA-DRB1*03:01: relevance for diagnosing and monitoring patients with neuromyelitis optica

OBJECTIVE To identify linear determinants of human aquaporin 4 (hAQP4) in the context of HLA-DRB1*03:01. DESIGN In this controlled study with humanized experimental animals, HLA-DRB1*03:01 transgenic mice were immunized with whole-protein hAQP4 emulsified in complete Freund adjuvant. To test T-cell responses, lymph node cells and splenocytes were cultured in vitro with synthetic peptides 20 amino acids long that overlap by 10 amino acids across the entirety of hAQP4. The frequency of interferon γ, interleukin (IL) 17, granulocyte-macrophage colony-stimulating factor, and IL-5-secreting CD4+ T cells was determined by the enzyme-linked immunosorbent sport assay. Quantitative immunofluorescence microscopy was performed to determine whether hAQP4281-300 inhibits the binding of anti-hAQP4 recombinant antibody to surface full-length hAQP4. SETTING Academic neuroimmunology laboratories. SUBJECTS Humanized HLA-DRB1*03:01+/+ H-2b-/- transgenic mice on a B10 background. RESULTS Peptide hAQP4281-300 generated a significantly (P &lt;.01) greater TH1 and TH17 immune response than any of the other linear peptides screened. This 20mer peptide contains 2 dominant immunogenic 15mer peptides. hAQP4284-298 induced predominantly an IL-17 and granulocyte-macrophage colony-stimulating factor TH cell phenotype, whereas hAQP4285-299 resulted in a higher frequency of TH1 cells. hAQP4281-300 did not interfere with recombinant AQP4 autoantibody binding. CONCLUSIONS hAQP4281-330 is the dominant linear immunogenic determinant of hAQP4 in the context of HLA-DRB1*03:01. Within hAQP4281-330 are 2 dominant immunogenic determinants that induce differential TH phenotypes. hAQP4 determinants identified in this study can serve as diagnostic biomarkers in patients with neuromyelitis optica and may facilitate the monitoring of treatment responses to pharmacotherapies.

Evaluation of a HLA-DR2 Inhibitor for the Treatment of MS Using Human Cellular Immunologic Models (51.6)

Multiple sclerosis (MS) is the most common human neurological disease affecting approximately 400,000 Americans with no cure available. It is believed to be driven by autoimmune CD4+ T cell responses directed against myelin antigens in the CNS. CD4+ T cell activation and response require antigen presentation by MHC (HLA in human) class II molecules. The HLA class II allele HLA-DRB1*1501 (HLA-DR2) is highly associated with MS, therefore we tested the immunological properties and activity of PV-267, a small molecule DR2 inhibitor in vitro in human cellular immunologic models related to MS using flow cytometry analysis, human cytokine ELISPOT and Bio-Plex assays. In vitro studies of human PBMCs from MS patient or healthy control subjects and testing a myelin basic protein specific T cell line showed that: 1) DR2 inhibitors can inhibit myelin antigen-specific human T cell responses mediated via HLA-DR2; 2) inhibit the production of pro-inflammatory cytokines; 3) treatment with the inhibitors does not have undesired non-specific immune-activating effect on human PBMCs expressing either HLA-DR2 or other HLA-DR molecules. In sum, our preclinical study has established the immunologic efficacy and assessed the safety of DR2 inhibitors in vitro. The results provide a strong rationale for the application of MHC inhibitors for the treatment of MS and potentially other T cell-mediated autoimmune diseases based on the immunological efficacy and good safety profile.

Investigating the Role of ERK2 in Peripheral T cells Function Using a Novel Transgenic Mouse Model (47.13)

Extracellular signal Regulated Kinase 2 (ERK2) is an important Ser-Thr Kinase involved in MAPK pathway. It is indispensable for early T cell development and is also believed to play a role in T-cell specific antigen recognition signaling, cell proliferation, differentiation, migration and survival. However, it remains unclear how ERK2 regulates peripheral T cell function. Our studies focused on the impact and mechanism of ERK2 deficiency in peripheral T cell activation/function utilizing a mouse model with a conditional ERK2 knockout identified and confirmed by expression of a YFP reporter. Our gene knockout strategy relied on Cre recombinase driven by either distal Lck or inducible promoters. Using flow cytometry analysis/cell sorting and cytokine ELISPOT assay, we have found that T cell activation, survival and cytokine production were impaired in the absence of ERK2. Our results also indicate a role for ERK2 in cell survival in serum starvation and ionomycin/Ca2+ mediated apoptosis. The presented approach will allow us to further investigate the role of ERK2 in other peripheral T cell functions and potentially identify cellular signaling pathways that could be explored for the treatment of CD4+ T cell mediated autoimmune diseases such as MS.

Development of autoreactive CD8+ T cells in Aire-deficient mice (101.38)

Autoimmune regulator (Aire) regulates the transcription of a myriad of self antigens in the thymus, which is important for the process of central tolerance to eliminate autoreactive T cells and to prevent autoimmune pathology. Aire-deficient mice (aire-/-) have previously been shown to develop multi-organ autoimmune disorder. We were interested in investigating the role of Aire for autoreactive CD8+ T cells using aire-/-Ia-/- mice. We found that CD8+ T cells were increased in aire-/-Ia-/- mice as compare with their aire+/+ or heterozygous littermates. Furthermore, aire-/-Ia-/- mice showed significantly lower body weight as compared with their littermates. Immune infiltrates mainly composed of CD11c+ cells and CD8+ T cells were found in various tissues of aire-/-Ia-/- mice, especially in liver, lung, pancreas and stomach. Autoantibody was detected in the serum of aire-/-Ia-/- mice directed against gastric tissue and was determined to be predominantly IgM. Collectively, our study shows that autoreactive CD8+ T cells arise on the background of Aire-deficiency are capable of initiating and promoting autoimmunity in the absence of CD4+ T cells.

Antigen presentation in the CNS during EAE (100.26)

Experimental autoimmune encephalomyelitis (EAE) shares many similarities with the acute inflammatory episodes of human Multiple Sclerosis (MS) both clinically and histopathogically and has therefore been instrumental in defining the sequence of events that occur in MS. It is well established that CD4+ T cells specific for myelin antigen (Ag) can induce EAE in susceptible animals. Dendritic cells (DCs) and microglia are both capable of priming CD4+ T cells against myelin Ag via presentation by MHC class II molecules present on their cell surface. However, it has remained unclear precisely how infiltration of inflammatory cells into the CNS during EAE relates to the kinetics of myelin antigen uptake and presentation by specific APCs. In this study we have investigated which APCs are loaded with myelin antigen in the naïve brain as well as in the immunogenic context of EAE. Our results reveal that a low percentage of microglia are already pre-loaded with myelin Ag even in naïve mice and are capable of presenting Ag immediately for T cell activation following immunization. Several days after immunization a large influx of myelin-loaded DCs appears, coinciding with the onset of clinical disease. This data suggests that low-level presentation of myelin Ag by CNS-resident microglia may play a role in the induction phase of EAE, although the mechanism by which these cells have acquired Ag remains unresolved.

Macrophage migration inhibitory factor and its role in autoimmune diseases

After several decades of research into the macrophage migration inhibitory factor (MIF), its diverse actions in the immune system are yet to be fully revealed. What has become clear is that MIF plays an important role in both innate and adaptive immunity. However, while several pathways mediating the function of MIF in the immune system have been established, its role in pathogenic states such as autoimmune diseases has remained unresolved. MIF has been implicated in different autoimmune diseases, including rheumatoid arthritis, glomerulonephritis, and multiple sclerosis, but knowledge about the underlying cellular and molecular mechanisms is just emerging. However, overall it appears that the inhibition of its proinflammatory action is likely to be a successful new therapeutic strategy for some autoimmune diseases, possibly by reducing the need for steroids. As more aspects of the role of this cytokine in the pathogenesis of autoimmune diseases are elucidated, better strategies to target it therapeutically can be expected.

Autoreactive T cells promote post-traumatic healing in the central nervous system

In general, autoimmune responses are considered harmful to the host. In the best-defined model of autoimmune disease, murine experimental allergic encephalomyelitis (EAE), for example, brain-protein-specific autoimmune responses of both major classes, type-1 and type-2, have been implicated in causing brain pathology. We induced type-1 and type-2 autoimmunity to myelin oligodendrocyte protein (MOG) in C57.BL/6 mice. Instead of using pertussis toxin (PTX) to open the blood-brain barrier (BBB), which is the classic procedure, we set an aseptic cerebral injury (ACI) to see what the consequences of pre-primed, autoreactive type-1 and type-2 memory T cells gaining access to the brain in the course of sterile tissue injury would be. Neither of these autoimmune response types induced pathology; on the contrary, both accelerated re-vascularization and post-traumatic healing. The data suggest that induction of either type-1 or type-2 autoimmune responses is not inherently noxious to the host, but can have beneficial effects on tissue repair. Autoimmune pathology may develop only if molecules of microbial origin such as pertussis toxin additionally induce the "infectious nonself/danger" reaction in the antigen-presenting cells (APC) of the target organ itself.

T-cell activation and receptor downmodulation precede deletion induced by mucosally administered antigen

The fate of antigen-specific T cells was characterized in myelin basic protein (MBP) T-cell receptor (TCR) transgenic (Tg) mice after oral administration of MBP. Peripheral Th cells are immediately activated in vivo, as indicated by upregulation of CD69 and increased cytokine responses (Th1 and Th2). Concurrently, surface TCR expression diminishes and internal TCR levels increase. When challenged for experimental autoimmune encephalomyelitis during TCR downmodulation, Tg mice are protected from disease. To characterize Th cells at later times after antigen feeding, it was necessary to prevent thymic release of naive Tg cells. Therefore, adult Tg mice were thymectomized before treatment. TCR expression returns in thymectomized Tg mice 3 days after MBP feeding and then ultimately declines in conjunction with MBP-specific proliferation and cytokine responses (Th1-type and Th2-type). The decline correlates with an increase in apoptosis. Collectively, these results demonstrate that a high dose of fed antigen induces early T-cell activation and TCR downmodulation, followed by an intermediate stage of anergy and subsequent deletion.

Revisiting tolerance induced by autoantigen in incomplete Freund's adjuvant

Injection of autoantigens in IFA has been one of the most effective ways of preventing experimental, T cell-mediated, autoimmune disease in mice. The mechanism that underlies this protection has, however, remained controversial, with clonal deletion, induction of suppressor cells or of type 2 immunity being implicated at one time or another. Using high resolution enzyme-linked immunospot (ELISPOT) analysis, we have revisited this paradigm. As models of autoimmunity against sequestered and readily accessible autoantigens, we studied experimental allergic encephalomyelitis, induced by myelin oligodendrocyte glycoprotein, proteolipid protein, myelin basic protein, and renal tubular Ag-induced interstitial nephritis. We showed that the injection of each of these Ags in IFA was immunogenic and CD4 memory cells producing IL-2, IL-4, and IL-5, but essentially no IFN-gamma. IgG1, but not IgG2a, autoantibodies were produced. The engaged T cells were not classic Th2 cells in that IL-4 and IL-5 were produced by different cells. The IFA-induced violation of self tolerance, including the deposition of specific autoantibodies in the respective target organs, occurred in the absence of detectable pathology. Exhaustion of the pool of naive precursor cells was shown to be one mechanism of the IFA-induced tolerance. In addition, while the IFA-primed T cells acted as suppressor cells, in that they adoptively transferred disease protection, they did not interfere with the emergence of a type 1 T cell response in the adoptive host. Both active and passive tolerance mechanisms, therefore, contribute to autoantigen:IFA-induced protection from autoimmune disease.