Exacerbation of viral and autoimmune animal models for multiple sclerosis by bacterial DNA

Failed, Interrupted, or Inconclusive Trials on Immunomodulatory Treatment Strategies in Multiple Sclerosis: Update 2015-2020

In the past decades, multiple sclerosis (MS) treatment has experienced vast changes resulting from major advances in disease-modifying therapies (DMT). Looking at the overall number of studies, investigations with therapeutic advantages and encouraging results are exceeded by studies of promising compounds that failed due to either negative or inconclusive results or have been interrupted for other reasons. Importantly, these failed clinical trials are informative experiments that can help us to understand the pathophysiological mechanisms underlying MS. In several trials, concepts taken from experimental models were not translatable to humans, although they did not lack a well-considered pathophysiological rationale. The lessons learned from these discrepancies may benefit future studies and reduce the risks for patients. This review summarizes trials on MS since 2015 that have either failed or have been interrupted for various reasons. We identify potential causes of failure or inconclusiveness, looking at the path from basic animal experiments to clinical trials, and discuss the implications for our current view on MS pathogenesis, clinical practice, and future study designs. We focus on anti-inflammatory treatment strategies, without including studies on already approved and effective DMT. Clinical trials addressing neuroprotective and alternative treatment strategies are presented in a separate article.

Bioinformatics Analysis of Gut Microbiota and CNS Transcriptome in Virus-Induced Acute Myelitis and Chronic Inflammatory Demyelination; Potential Association of Distinct Bacteria With CNS IgA Upregulation

Virus infections have been associated with acute and chronic inflammatory central nervous system (CNS) diseases, e.g., acute flaccid myelitis (AFM) and multiple sclerosis (MS), where animal models support the pathogenic roles of viruses. In the spinal cord, Theiler's murine encephalomyelitis virus (TMEV) induces an AFM-like disease with gray matter inflammation during the acute phase, 1 week post infection (p.i.), and an MS-like disease with white matter inflammation during the chronic phase, 1 month p.i. Although gut microbiota has been proposed to affect immune responses contributing to pathological conditions in remote organs, including the brain pathophysiology, its precise role in neuroinflammatory diseases is unclear. We infected SJL/J mice with TMEV; harvested feces and spinal cords on days 4 (before onset), 7 (acute phase), and 35 (chronic phase) p.i.; and examined fecal microbiota by 16S rRNA sequencing and CNS transcriptome by RNA sequencing. Although TMEV infection neither decreased microbial diversity nor changed overall microbiome patterns, it increased abundance of individual bacterial genera Marvinbryantia on days 7 and 35 p.i. and Coprococcus on day 35 p.i., whose pattern-matching with CNS transcriptome showed strong correlations: Marvinbryantia with eight T-cell receptor (TCR) genes on day 7 and with seven immunoglobulin (Ig) genes on day 35 p.i.; and Coprococcus with gene expressions of not only TCRs and IgG/IgA, but also major histocompatibility complex (MHC) and complements. The high gene expression of IgA, a component of mucosal immunity, in the CNS was unexpected. However, we observed substantial IgA positive cells and deposition in the CNS, as well as a strong correlation between CNS IgA gene expression and serum anti-TMEV IgA titers. Here, changes in a small number of distinct gut bacteria, but not overall gut microbiota, could affect acute and chronic immune responses, causing AFM- and MS-like lesions in the CNS. Alternatively, activated immune responses would alter the composition of gut microbiota.

Identification of new CpG oligodeoxynucleotide motifs that induce expression of interleukin-1β and nitric oxide in avian macrophages

Unmethylated CpG motifs are known to stimulate mammalian toll-like receptor-9 expressing cells such as macrophages. However, the magnitude of immune-stimulation by CpG-motif can be sequence- and host-specific, implying the importance of identifying new immune-stimulatory motifs. This study aimed to determine the frequency distribution of 256 unique hexamers CpG-motifs in the Salmonella genome and to characterize their immune-stimulatory activity in avian host. We synthesized 256 CpG oligodeoxynucleotides (CpG-ODNs) each containing triplicates of a unique hexamer CpG-motif and tested their ability to induce expression of pro-inflammatory cytokine IL-1β in avian macrophages using q-RT PCR in four rounds of screening assays. CpG-ODNs that induced significantly higher IL-1β expression were also subjected to Griess assay to determine their ability to induce nitric oxide (NO) production in avian macrophages. This analysis resulted in identification of 7 CpG-ODNs that consistently induced IL-1β expression and NO production in avian macrophages at a level similar to the expression achieved using commercially available PTO-CpG-ODN 2007 and LPS derived from Salmonella. To the best of our knowledge, this is the first report showing comprehensive screening of all possible unique CpG hexamer (n=256) motifs for their ability to induce IL-1β expression and NO production in avian macrophages. We also show that the newly identified CpG-motifs with high immune-stimulatory activity are widely distributed in Salmonella genome. The CpG-ODNs identified in this study may serve as promising immunoprophylactics to potentiate innate responses in chickens against Salmonella and other infectious agents.

Targeting innate receptors with MIS416 reshapes Th responses and suppresses CNS disease in a mouse model of multiple sclerosis

Modification of the innate immune cell environment has recently been recognized as a viable treatment strategy for reducing autoimmune disease pathology. MIS416 is a microparticulate immune response modifier that targets myeloid cells, activating cytosolic receptors NOD2 and TLR9, and has completed a phase 1b/2a trial for the treatment of secondary progressive multiple sclerosis. Using a mouse model of multiple sclerosis, we are investigating the pathways by which activation of TLR9 and NOD2 may modify the innate immune environment and the subsequent T cell-mediated autoimmune responses. We have found that MIS416 has profound effects on the Th subset balance by depressing antigen-specific Th1, Th17, and Th2 development. These effects coincided with an expansion of specific myeloid subpopulations and increased levels of MIS416-stimulated IFN-γ by splenocytes. Additionally, systemic IFN-γ serum levels were enhanced and correlated strongly with disease reduction, and the protective effect of MIS416 was abrogated in IFN-γ-deficient animals. Finally, treatment of secondary progressive MS patients with MIS416 similarly elevated the levels of IFN-γ and IFN-γ-associated proteins in the serum. Together, these studies demonstrate that administration of MIS416, which targets innate cells, reshapes autoimmune T cell responses and leads to a significant reduction in CNS inflammation and disease.

BCG and BCG/DNAhsp65 vaccinations promote protective effects without deleterious consequences for experimental autoimmune encephalomyelitis

A prime-boost strategy conserving BCG is considered the most promising vaccine to control tuberculosis. A boost with a DNA vaccine containing the mycobacterial gene of a heat shock protein (pVAXhsp65) after BCG priming protected mice against experimental tuberculosis. However, anti-hsp65 immunity could worsen an autoimmune disease due to molecular mimicry. In this investigation, we evaluated the effect of a previous BCG or BCG/pVAXhsp65 immunization on experimental autoimmune encephalomyelitis (EAE) development. Female Lewis rats were immunized with BCG or BCG followed by pVAXhsp65 boosters. The animals underwent EAE induction and were daily evaluated for weight loss and clinical score. They were euthanized during recovery phase to assess immune response and inflammatory infiltration at the central nervous system. Previous immunization did not aggravate or accelerate clinical score or weight loss. In addition, this procedure clearly decreased inflammation in the brain. BCG immunization modulated the host immune response by triggering a significant reduction in IL-10 and IFN-γ levels induced by myelin basic protein. These data indicated that vaccination protocols with BCG or BCG followed by boosters with pVAXhsp65 did not trigger a deleterious effect on EAE evolution.

Magnetic resonance imaging reveals therapeutic effects of interferon-beta on cytokine-induced reactivation of rat model of multiple sclerosis

Interferon-β (IFN-β) drugs are considered to derive their beneficial effects on multiple sclerosis (MS) progression via their antiinflammatory properties, but the precise mechanism of action remains unclear. Here, we sought to discover how IFN-β impacts on inflammation-associated aggravation of MS-like lesions in rat. Animals with dormant focal experimental allergic encephalomyelitis (EAE) lesions were challenged intravenously with a replication-deficient adenovirus vector carrying interleukin (IL)-1β cDNA (AdIL-1β). Aggravation of inflammation and demyelination within the focal EAE lesion was observed after AdIL-1β injection with associated changes in tissue structure detected by diffusion and magnetization transfer imaging. Postgadolinium-DTPA T1-weighted images revealed contrast enhancement in the ipsilateral meninges, indicating breakdown of the blood-cerebrospinal fluid barrier, and increased left/right regional cerebral blood volume ratio was also observed after AdIL-1β injection. To determine the role of IFN-β on reactivation of the EAE lesion, rats were treated with therapeutic doses of IFN-β and focal EAE lesions showed significantly reduced reactivation in response to systemic AdIL-1β injection. In conclusion, these findings indicate a central role for peripheral IL-1β expression in the mechanism of MS lesion reactivation and that the therapeutic effects of IFN-β may, at least in part, reflect suppression of the effects of peripheral inflammation on MS lesion pathogenesis.

TH17-Driven Inflammation is Present in All Clinical Forms of Multiple Sclerosis; Disease Quiescence is Associated with Gata3-Expressing Cells

Multiple Sclerosis (MS) presents in a variety of clinical forms associated with a diverse grade of neurological impairment, different prognosis and, possibly, multiple pathogenic mechanisms. Thus, whereas relapsing-remitting (RR) MS appears to be largely driven by inflammatory processes, neurodegeneration, partially independent from inflammation, drives primary progressive (PP) and secondary progressive (SP) MS. An extensive analysis of neuroinflammation in the different forms of MS was performed by evaluating immunophenotypic and functional parameters in MBP-stimulated T lymphocytes of 103 MS patients (26 benign (BE) MS, 30 RRMS, 33 SPMS and 14 PPMS) and 40 healthy controls (HC). Results showed that: i) IL-17-producing and RORC/γt-expressing CD4+ T cells (TH17 lymphocytes), as well as IL-6 expressing CD14+ cell were augmented in all patients; ii) IL-22-expressing cells were increased in all forms of MS with the exception of PPMS; iii) TGF-β-expressing B cells were increased only in RRMS; and iv) GATA3-, NFATc-1, IL-13-, and IL-25-expressing cells (TH2 lymphocytes) were augmented in RRMS and BEMS patients alone. Data herein indicate a pivotal pathogenic role of TH17-driven inflammation in all clinical forms of MS and suggest that control over disease (RRMS and BEMS) is associated not with lack of inflammation per se, but rather with the activation of immune-mediated anti-inflammatory mechanisms. These results could help the design of novel diagnostic and therapeutic approaches.

Immunopathological patterns from EAE and Theiler's virus infection: Is multiple sclerosis a homogenous 1-stage or heterogenous 2-stage disease?

Multiple sclerosis (MS) is a disease which can presents in different clinical courses. The most common form of MS is the relapsing-remitting (RR) course, which in many cases evolves into secondary progressive (SP) disease. Autoimmune models such as experimental autoimmune encephalomyelitis (EAE) have been developed to represent the various clinical forms of MS. These models along with clinico-pathological evidence obtained from MS patients have allowed us to propose '1-stage' and '2-stage' disease theories to explain the transition in the clinical course of MS from RR to SP. Relapses in MS are associated with pro-inflammatory T helper (Th) 1/Th17 immune responses, while remissions are associated with anti-inflammatory Th2/regulatory T (Treg) immune responses. Based on the '1-stage disease' theory, the transition from RR to SP disease occurs when the inflammatory immune response overwhelms the anti-inflammatory immune response. The '2-stage disease' theory proposes that the transition from RR to SP-MS occurs when the Th2 response or some other responses overwhelm the inflammatory response resulting in the sustained production of anti-myelin antibodies, which cause continuing demyelination, neurodegeneration, and axonal loss. The Theiler's virus model is also a 2-stage disease, where axonal degeneration precedes demyelination during the first stage, followed by inflammatory demyelination during the second stage.

Alteration of T cell cytokine production in PLPp-139-151-induced EAE in SJL mice by an immunostimulatory CpG oligonucleotide

Experimental autoimmune encephalomyelitis (EAE) is - in certain aspects - regarded as an animal model of the human CNS autoimmune disease multiple sclerosis (MS). While in EAE CNS-autoantigen-specific immunity is induced in a defined way, the initial processes leading to CNS autoimmunity in humans are so far unknown. Despite essential restrictions, which exist regarding the interpretation of EAE data towards MS, EAE might be a useful model to study certain basic aspects of CNS autoimmunity. Studies in MS have demonstrated that established autoimmune pathology can be critically influenced by environmental factors, in particular viral and bacterial infections. To investigate this interaction, EAE as an instrument to study CNS autoimmunity under defined conditions appears to be a suitable experimental tool. For this reason, we here investigated the influence of the Toll-like-receptor (TLR) ligand CpG oligonucleotide (CpG) on already established CNS autoimmunity in murine proteolipid protein (PLP)-induced EAE in SJL mice. CpG were found to co-stimulate PLPp-specific IFN-γ production in the peripheral immune system and in the CNS. However, CpG induced Interleukin (IL)-17 production in the inflamed CNS both alone and in combination with additional PLPp stimulation. These findings might indicate a mechanism by which systemic infections and the microbial stimuli associated with them may influence already existing CNS autoimmune pathology.

Experimental autoimmune encephalomyelitis as a testing paradigm for adjuvants and vaccines

Experimental autoimmune encephalomyelitis (EAE) is an experimental model for multiple sclerosis. EAE can be induced by inoculation with central nervous system (CNS) proteins or peptides emulsified in complete Freund's adjuvant. Protection from EAE, enhancement of EAE or subclinical priming for EAE can occur as a result of either live viral infection or DNA immunization with molecular mimics of CNS proteins or peptides. Here we review the published data describing modulation of EAE through administration of various CNS proteins/peptides introduced via live virus or plasmid DNA and modulation of EAE through choice of adjuvant (immunostimulating agents).

Inverse vaccination, the opposite of Jenner's concept, for therapy of autoimmunity

DNA-based vaccines to induce antigen-specific inhibition of immune responses in human autoimmune diseases represent the inverse of what Jenner intended when he invented vaccination. Jenner's vaccine induced antigen-specific immunity to small pox. DNA vaccines for autoimmunity have been developed in preclinical settings, and now tested in human trials. The first two clinical trials, one in relapsing remitting multiple sclerosis, and the other in type 1 diabetes indicate that specific inhibition of antigen-specific antibody and T-cell responses is attainable in humans. Further development of this approach is ongoing. This new version of immunization termed 'inverse vaccination' when applied to autoimmune diseases, may allow targeted reduction of unwanted antibody and T-cell responses to autoantigens, while leaving the remainder of the immune system intact. The method of specifically reducing a pathological adaptive autoimmune response is termed inverse vaccination.

Synthetic oligodeoxynucleotides induce gastritis in mice

To investigate whether DNA directly induces gastritis and/or peptic ulcer, we injected synthetic DNA including CpG motif (CpG-DNA) to mouse stomach. BALB/c mice were injected with either saline, acetic acid (AA), CpG-DNA, or Control-DNA. Mice were sacrificed, and sections of the stomachs were stained with hematoxylin and eosin. The lesions were histopathologically scored from 0 to 4 based on the extent of the inflammation. Populations of neutrophils and mononuclear cells infiltrated to the lesion were calculated. IFN-y mRNA expression at the injection site was analyzed by RT-PCR. The number of CpG motifs included in the complete genomes of H. pylori HP26695 and J99, Escherichia coli O157, and Salmonella Typhi was determined by genomic analysis of these bacteria. Intragastric injection with CpG-DNA induced gastritis, and statistical analysis of histological scores revealed a significant difference between saline vs CpG-DNA (p = 0.037). The population of mononuclear cells infiltrated to the lesions was significantly higher in mice injected with CpG-DNA than that injected with AA (p = 0.0061). IFN-gamma mRNA expression was detected in the CpG-DNA group. While H. pylori includes multiple CpG motifs in its genome, it has fewer than the other pathogenic gram-negative bacilli. We conclude that synthetic DNA including CpG motif directly causes gastritis in mice and induces IFN-gamma production in the stomach. Bacterial DNA including CpG motif is known to stimulate innate immunity and to cause inflammation. Thus, H. pylori genomic DNA may be one of the virulent factors involved in H. pylori infection.

Neuropathogenesis of Theiler's murine encephalomyelitis virus infection, an animal model for multiple sclerosis

Theiler's murine encephalomyelitis virus (TMEV) infection of mice is an experimental model for multiple sclerosis (MS). TMEV induces a biphasic disease in susceptible mouse strains. During the acute phase, 1 week after infection, TMEV causes polioencephalomyelitis characterized by infection and apoptosis of neurons in the gray matter of the brain. During the chronic phase, about 1 month after infection, virus infects glial cells and macrophages, and induces inflammatory demyelination with oligodendrocyte apoptosis and axonal degeneration in the white matter of the spinal cord. Although antibody, CD4(+), and CD8(+) T cell responses against TMEV capsid proteins play important roles in neuropathogenesis, infectious virus with persistence is necessary to induce demyelination; in general, adoptive transfer of antibody or T cells alone did not induce central nervous system (CNS) disease. The TMEV model can be useful for testing new therapeutic strategies specifically as a viral model for MS. Therapies targeting adhesion molecules, axonal degeneration, and immunosuppression can be beneficial for pure autoimmune CNS demyelinating diseases, such as experimental autoimmune encephalomyelitis, but could be detrimental in virus-induced demyelinating diseases, such as progressive multifocal leukoencephalopathy.

Transgenic models for cytokine-induced neurological disease

Considerable evidence supports the idea that cytokines are important mediators of pathophysiologic processes within the central nervous system (CNS). Numerous studies have documented the increased production of various cytokines in the human CNS in a variety of neurological and neuropsychiatric disorders. Deciphering cytokine actions in the intact CNS has important implications for our understanding of the pathogenesis and treatment of these disorders. One approach to address this problem that has been used widely employs transgenic mice with CNS-targeted production of different cytokines. Transgenic production of cytokines in the CNS of mice allows not only for the investigation of complex cellular responses at a localized level in the intact brain but also more closely recapitulates the expression of these mediators as found in disease states. As discussed in this review, the findings show that these transgenic animals exhibit wide-ranging structural and functional deficits that are linked to the development of distinct neuroinflammatory responses which are relatively specific for each cytokine. These cytokine-induced alterations often recapitulate those found in various human neurological disorders not only underscoring the relevance of these models but also reinforcing the clinicopathogenetic significance of cytokines in diseases of the CNS.

Targeting myelin proteolipid protein to the MHC class I pathway by ubiquitination modulates the course of experimental autoimmune encephalomyelitis

Relapsing-remitting experimental autoimmune encephalomyelitis (EAE), a multiple sclerosis model, is induced in mice by injection of myelin proteolipid protein (PLP) encephalitogenic peptide, PLP139-151, in adjuvant. In this study, prior to EAE induction, mice were vaccinated with a bacterial plasmid encoding a PLP-ubiquitin fusion (pCMVUPLP). During the relapse phase of EAE, clinical signs, histopathologic changes, in vitro lymphoproliferation to PLP139-151 and interferon-gamma levels were reduced in pCMVUPLP-vaccinated mice, compared to mock-vaccinated mice (controls). Lymphocytes from pCMVUPLP-vaccinated mice produced interleukin-4, a cytokine lacking in controls. Thus, pCMVUPLP vaccination can modulate the relapse after EAE induction.

Role of B:T cell ratio in suppression of clinical signs: a model for silent MS

B10.S mice have been considered resistant to experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. However, sensitization with a myelin oligodendrocyte glycoprotein (MOG) peptide, MOG(92-106), induced clinical signs in 30% of mice and central nervous system (CNS) pathology in 93% of mice. Symptomatic mice had more demyelination, inflammation, perivascular cuffing and axonal damage in the CNS compared to asymptomatic mice, but no strong correlations between CNS pathology and clinical score were found. Interestingly, the ratio of B cells to T cells in cellular infiltrates correlated with clinical score. This suggests that the balance between B and T cells contributes to expression of clinical signs.

Multiple sclerosis and virus induced immune responses: autoimmunity can be primed by molecular mimicry and augmented by bystander activation

Polymicrobial infections have been associated with plausible immune mediated diseases, including multiple sclerosis (MS). Virus infection can prime autoimmune T cells specific for central nervous system (CNS) antigens, if virus has molecular mimicry with CNS proteins. On the other hand, infection of irrelevant viruses will induce two types of cytokine responses. Infection with a virus such as lymphocytic choriomeningitis virus (LCMV), can induce interferon (IFN)-alpha/beta production and suppress autoimmunity, while infection with a virus, such as murine cytomegalovirus (MCMV), can activate natural killer (NK), NKT and dendritic cells, resulting in interleukin (IL)-12 and IFN-gamma production. These cytokines can cause bystander activation of autoreactive T cells. We established an animal model, where mice infected with vaccinia virus encoding myelin protein can mount autoimmune responses. However, the mice develop clinical disease only after irrelevant immune activation either with complete Freund's adjuvant or MCMV infection. In this review, we propose that a combination of two mechanisms, molecular mimicry and bystander activation, induced by virus infection, can lead to CNS demyelinating diseases, including MS. Viral proteins having molecular mimicry with self-proteins in the CNS can prime genetically susceptible individuals. Once this priming has occurred, an immunologic challenge could result in disease through bystander activation by cytokines.

Active induction of experimental allergic encephalomyelitis

This protocol details a method to actively induce experimental allergic encephalomyelitis (EAE), a widely used animal model for studies of multiple sclerosis. EAE is induced by stimulating T-cell-mediated immunity to myelin antigens. Active induction of EAE is accomplished by immunization with myelin antigens emulsified in adjuvant. This protocol focuses on induction of EAE in mice; however, the same principles apply to EAE induction in other species. EAE in rodents is manifested typically as ascending flaccid paralysis with inflammation targeting the spinal cord. However, more diverse clinical signs can occur in certain strain/antigen combinations in rodents and in other species, reflecting increased inflammation in the brain.

Inhibition of allergic airways disease by immunomodulatory therapy with whole killed Streptococcus pneumoniae

Asthma is a common inflammatory disease of the airways. Current therapies alleviate symptoms but do not treat the disease. We aim to develop effective immunomodulatory therapies (IMTs) for asthma that target the underlying causes of disease based on Streptococcus pneumoniae (Spn). The effect of Spn IMT on the development of asthma [allergic airways disease (AAD)] was determined in mice. Killed Spn was administered before, during or after ovalbumin sensitization, and the subsequent development of AAD was assessed. IMT attenuated T cell cytokine production, goblet cell hyperplasia, airways hyperresponsiveness (AHR), and eosinophil numbers in the blood, bronchoalveolar lavage fluid and peribronchial tissue. This indicates the potential of Spn as an IMT for asthma.

Targeting inflammatory demyelinating lesions to sites of Wallerian degeneration

In Theiler's murine encephalomyelitis virus (TMEV) infection, an animal model for multiple sclerosis (MS), axonal injury precedes inflammatory demyelinating lesions, and the distribution of axonal damage present during the early phase of infection corresponds to regions where subsequent demyelination occurs during the chronic phase. We hypothesized that axonal damage recruits inflammatory cells to sites of Wallerian degeneration, leading to demyelination. Three weeks after TMEV infection, axonal degeneration was induced in the posterior funiculus of mice by injecting the toxic lectin Ricinus communis agglutinin (RCA) I into the sciatic nerve. Neuropathology was examined 1 week after lectin injection. Control mice, infected with TMEV but receiving no RCA I, had inflammatory demyelinating lesions in the anterior/lateral funiculi. Other control mice that received RCA I alone did not develop inflammatory lesions. In contrast, RCA I injection into TMEV-infected mice induced lesions in the posterior funiculus in addition to the anterior/lateral funiculi. We found no differences in lymphoproliferative responses or antibody titers against TMEV among the groups. This suggests that axonal degeneration contributes to the recruitment of inflammatory cells into the central nervous system by altering the local microenvironment. In this scenario, lesions develop from the axon (inside) to the myelin (outside) (Inside-Out model).

Sequential polymicrobial infections lead to CNS inflammatory disease: possible involvement of bystander activation in heterologous immunity

VV(PLP) is a recombinant vaccinia virus (VV) encoding myelin proteolipid protein (PLP) that has been used to investigate molecular mimicry and autoimmunity. Since virus infections can cause bystander activation, mice were first infected with VV(PLP), and later challenged with wild-type VV, lymphocytic choriomeningitis virus (LCMV), or murine cytomegalovirus (MCMV). Among the VV(PLP)-primed mice, only MCMV challenge induced significant Ki-67(+), CD3(+)T cell infiltration into the central nervous system (CNS) with a mild PLP antibody response. While MCMV alone caused no CNS disease, control VV-infected mice followed with MCMV developed mild CNS inflammation. Thus, heterologous virus infections can induce CNS pathology.

Cytokines and the immune–neuroendocrine network: What did we learn from infection and autoimmunity?

The initial view of the neuroendocrine-immune communication as the brake of immune activation is changing. Recent evidence suggests that the optimization of the body's overall response to infection could be actually the role of the immune-endocrine network. In gradually more complex organisms, the multiplicity of host-pathogen interfaces forced the development of efficient and protective responses. Molecules such as cytokines and Toll-like receptors (TLRs) are distributed both in the periphery and in the brain to participate in a coordinated adaptive function. When sustained release of inflammatory mediators occurs, as in autoimmune diseases, undesirable pathological consequences become evident with different manifestations and outcomes. Clearly, organisms are not well adapted to that disregulated condition yet, suggesting that additional partners within neuroendocrine-immune interactions might emerge from the evolutionary road.

Toll-like receptors in central nervous system glial inflammation and homeostasis

Toll-like receptors (TLRs) are a family of pattern-recognition receptors expressed on cells of the innate immune system that allow for the recognition of conserved structural motifs on a wide array of pathogens, referred to as pathogen-associated molecular patterns, as well as some endogenous molecules. The recent emergence of studies examining TLRs in the central nervous system (CNS) indicates that these receptors not only play a role in innate immunity in response to infectious diseases but may also participate in CNS autoimmunity, neurodegeneration, and tissue injury. This review summarizes the experimental evidence demonstrating a role for TLRs in the context of CNS inflammation in both infectious and noninfectious conditions.

Antibody association with a novel model for primary progressive multiple sclerosis: induction of relapsing-remitting and progressive forms of EAE in H2s mouse strains

Multiple sclerosis (MS) can be divided into 4 clinical forms: relapsing-remitting (RR), primary progressive (PP), secondary progressive (SP), and progressive relapsing (PR). Since PP-MS is notably different from the other forms of MS, both clinically and pathologically, the question arises whether PP-MS is immunologically similar to the other forms. The pathogenesis of the PP-MS remains unclear, partly due to a lack of highly relevant animal models. Using an encephalitogenic peptide from myelin oligodendrocyte glycoprotein (MOG)92-106, we have established animal models that mimic different forms of MS in 2 strains of H-2s mice, SJL/J and A.SW. We induced experimental allergic encephalomyelitis (EAE) using MOG92-106 in the presence or absence of supplemental Bordetella pertussis (BP). Although, SJL/J mice developed RR-EAE whether BP was given or not, A.SW mice developed PP-EAE without BP and SP-EAE with BP. Histologically, SJL/J mice developed mild demyelinating disease with T cell infiltration, while A.SW mice developed large areas of plaque-like demyelination with immunoglobulin deposition and neutrophil infiltration, but with minimal T cell infiltration. In A.SW mice without BP, high titer serum anti-MOG antibody was detected and the anti-MOG IgG2a/IgG1 ratio correlated with survival times of mice. We hypothesized that, in A.SW mice, a Th2 response favors production of myelinotoxic antibodies, leading to progressive forms with early death. Our new models indicate that a single encephalitogen could induce either RR-, PP-, or SP- forms of demyelinating disease in hosts with immunologically different humoral immune responses.

Massive apoptosis in lymphoid organs in animal models for primary and secondary progressive multiple sclerosis

The mechanism(s) responsible for generating the different forms of multiple sclerosis, primary progressive (PP) and secondary progressive (SP) versus relapsing-remitting (RR), is not well understood. Using myelin oligodendrocyte glycoprotein (MOG)(92-106), we have established animal models that mimic the different types of multiple sclerosis. A.SW mice develop PP or SP-experimental allergic encephalomyelitis (EAE) with large areas of demyelination and high titers of MOG antibody whereas SJL/J mice develop RR-EAE with perivascular T cells and mild demyelination. In A.SW progressive EAE, we found atrophy of the thymus, spleen, and lymph nodes with depletion of T and B cells and massive apoptosis, as demonstrated by immunohistochemistry, terminal dUTP nick-end labeling, and DNA agarose gel electrophoresis. To test whether lymphoid apoptosis itself contributes to disease progression, we injected SJL/J mice with apoptotic thymocytes. Injection of apoptotic cells resulted in greater than 20% of mice developing SP-EAE with ataxia. SJL/J mice with SP-EAE had large areas of demyelination, high MOG antibody titers and atrophic lymphoid organs. Spleen cells from mice with progressive EAE produced less interferon-gamma than those from RR-EAE when stimulated with mitogen. We suggest that induction of lymphoid apoptosis alters the balance of Th1 versus Th2 immune responses and increases MOG antibody production, leading to exacerbation of demyelination and subsequent disease progression.

Immunostimulatory oligodeoxynucleotide isolated from genome wide screening of Mycobacterium bovis chromosomal DNA

Bacterial DNA has a variety of immunostimulatory activities, such as the activation of B cells and natural killer cells, the induction of interferon-gamma, and the induction of Th1-type immune responses. In contrast, mammalian DNA does not have these activities. To evaluate the genomic DNA sequences of Mycobacterium bovis that have immunostimulatory activity, we used a computer to analyze the M. bovis genome and we designed a series of synthetic, 20 base length, phosphodiester backbone oligodeoxynucleotides (ODNs) that contain CpG motifs (MB-ODNs). We screened the immunostimulatory MB-ODNs that induce the activation of the NF-kappaB-responsive IL-8 promoter in RAW 264.7 cells. Our experimental analyses demonstrate that the potent CpG DNA in the M. bovis genome has functional effects as a Th1-responsive adjuvant, and that it activates the transcription factor NF-kappaB. Moreover, we found that both the CpG motifs and the context of the sequence surrounding the CpG motif are important for the immunostimulatory activities. The identification of the potent immunostimulatory DNA sequence in a native bacterial genome may give insights to the optimal sequence for well-controlled immune responses.

Central nervous system pathology caused by autoreactive CD8+ T-cell clones following virus infection

Theiler's murine encephalomyelitis virus (TMEV) causes a demyelinating disease in infected mice which has similarities to multiple sclerosis. Spleen cells from TMEV-infected SJL/J mice stimulated with antigen-presenting cells infected with TMEV resulted in a population of autoreactive CD8+ cytotoxic T cells that kill uninfected syngeneic cells. We established CD8+ T cell clones that could kill both TMEV-infected and uninfected syngeneic targets, although infected target cells were killed more efficiently. The CD8+ T-cell clones produced gamma interferon when incubated with either infected or uninfected syngeneic target cells. Intracerebral injection of the clones into naïve mice induced degeneration, not only in the brain, but also in the spinal cord. This suggests that CD8+ Tc1 cells could play a pathogenic role in central nervous system inflammation.

G-rich DNA suppresses systemic lupus

Whereas the role of immune complexes in mediating renal cell and immune cell activation is well established, the contribution of sequence-specific immunomodulatory actions of the chromatin part remains unclear. Toll-like receptor-9 (TLR-9) mediates immunostimulatory effects of unmethylated microbial CpG-DNA. It was hypothesized that hypomethylated CpG-DNA in vertebrates may have similar effects and may contribute to disease progression in lupus nephritis. A synthetic G-rich DNA, known to block CpG-DNA effects, was used in this study. In macrophages, G-rich DNA suppressed CpG-DNA-but not LPS-induced production of CCL5 in a dose-dependent manner. Injections of G-rich DNA suppressed lymphoproliferation induced by CpG-DNA injections in mice. In MRL(lpr/lpr) mice with lupus nephritis, labeled G-rich DNA co-localized to glomerular immune complexes and was taken up into endosomes of TLR-9-positive infiltrating macrophages. Eleven-week-old MRL(lpr/lpr) mice that received injections of either saline or G-rich DNA for 13 wk revealed decreased lymphoproliferation and less autoimmune tissue injury in lungs and kidneys as compared with saline-treated controls. G-rich DNA reduced the levels of serum dsDNA-specific IgG2a as well as the renal immune complex deposits. This was consistent with the blocking effect of G-rich DNA on CpG-DNA-induced proliferation of B cells that were isolated from MRL(lpr/lpr) mice. As oligodeoxyribonucleotide 2114-treated MRL(lpr/lpr) mice were not exposed to exogenous CpG-DNA, these effects should relate to a blockade of CpG motifs in endogenous DNA. It is concluded that adjuvant activity of self-DNA contributes to the pathogenesis of lupus nephritis. Modulating the CpG-DNA-TLR-9 pathway may offer new opportunities for the understanding and treatment of lupus.

Molecular mechanisms of autoimmunity triggered by microbial infection

Autoimmunity can be triggered by microbial infection. In this context, the discovery of Toll-like receptors (TLRs) provides new insights and research perspectives. TLRs induce innate and adaptive antimicrobial immune responses upon exposure to common pathogen-associated molecules, including lipopeptides, lipopolysaccharides, and nucleic acids. They also have the potential, however, to trigger autoimmune disease, as has been revealed by an increasing number of experimental reports. This review summarizes important facts about TLR biology, available data on their role in autoimmunity, and potential consequences for the management of patients with autoimmune disease.

Ets-1 deficiency leads to altered B cell differentiation, hyperresponsiveness to TLR9 and autoimmune disease

It has been shown that mice with a targeted mutation in the Ets-1 gene exhibit increased B cell terminal differentiation to IgM-secreting plasma cells. Here, we show that mice, formerly described to lack Ets-1 protein, actually express low levels of an internally deleted Ets-1 protein. Mice harboring this Ets-1 hypomorphic allele possess very few marginal zone B cells and have increased expression of activation markers on follicular B cells. Adoptive transfer experiments indicate that this activated phenotype can be reversed upon transfer of Ets-1-deficient B cells to a wild-type host, suggesting a role for B cell-extrinsic factors in regulating the activated state. Supporting this observation, the reverse transfer experiment of wild-type B cells into an Ets-1-deficient host resulted in increased expression of activation markers on the transferred B cells. However, there are also cell-intrinsic changes in Ets-1-deficient B cells as demonstrated by their increased differentiation to plasma cells in vitro in response to stimulation with cytosine-phosphate-guanine DNA sequence-containing oligodeoxynucleotide [CpG DNA, a Toll-like receptor (TLR) 9 ligand]. Consistent with the activated phenotype and increased terminal differentiation of Ets-1-deficient B cells, Ets-1 mutant mice develop autoimmune disease. Hence, our studies establish Ets-1 as an important regulator of peripheral B cell differentiation and B cell responses to TLR9 activation.

Immunology of multiple sclerosis

Multiple sclerosis (MS) develops in young adults with a complex predisposing genetic trait and probably requires an inciting environmental insult such as a viral infection to trigger the disease. The activation of CD4+ autoreactive T cells and their differentiation into a Th1 phenotype are a crucial events in the initial steps, and these cells are probably also important players in the long-term evolution of the disease. Damage of the target tissue, the central nervous system, is, however, most likely mediated by other components of the immune system, such as antibodies, complement, CD8+ T cells, and factors produced by innate immune cells. Perturbations in immunomodulatory networks that include Th2 cells, regulatory CD4+ T cells, NK cells, and others may in part be responsible for the relapsing-remitting or chronic progressive nature of the disease. However, an important paradigmatic shift in the study of MS has occurred in the past decade. It is now clear that MS is not just a disease of the immune system, but that factors contributed by the central nervous system are equally important and must be considered in the future.

An RNA vaccine based on recombinant Semliki Forest virus particles expressing the Cu,Zn superoxide dismutase protein of Brucella abortus induces protective immunity in BALB/c mice

We constructed infectious but replication-deficient Semliki Forest virus (SFV) particles carrying recombinant RNA encoding Brucella abortus Cu,Zn superoxide dismutase (SOD). The recombinant SFV particles (SFV-SOD particles) were then evaluated for their ability to induce a T-cell immune response and to protect BALB/c mice against a challenge with B. abortus 2308. Intraperitoneal injection of mice with recombinant SFV-SOD particles did not lead to the induction of SOD-specific antibodies, at least until week 6 after immunization (the end of the experiment). In vitro stimulation of splenocytes from the vaccinated mice with either recombinant Cu,Zn SOD (rSOD) or crude Brucella protein resulted in a T-cell proliferative response and the induction of gamma interferon secretion but not interleukin-4. In addition, the splenocytes exhibited significant levels of cytotoxic T-lymphocyte activity against Brucella-infected cells. The SFV-SOD particles, but not the control virus particles, induced a significant level of protection in BALB/c mice against challenge with B. abortus virulent strain 2308. These findings indicated that an SFV-based vector carrying the SOD gene has potential for use as a vaccine to induce resistance against B. abortus infections.

DNA vaccines coding for heat-shock proteins (HSPs): tools for the activation of HSP-specific regulatory T cells

Heat-shock proteins (HSPs) perform opposing functions in autoimmune arthritis. HSP-specific T cells drive the progression of adjuvant arthritis (AA), an experimental model of autoimmune arthritis. However, HSP-specific T cells can also have a regulatory phenotype, controlling arthritogenic T cells and inhibiting AA progression. This manuscript reviews the use of DNA vaccines coding for HSPs to analyse the role of these proteins in the regulation of arthritis. Recent studies suggest that HSPs participate in the control of pathological autoimmunity. Indeed, DNA vaccines coding for HSPs can be used to activate these HSP-specific built-in regulatory mechanisms. Thus, DNA vaccines coding for HSPs may serve not only as tools for the dissection of immunoregulatory mechanisms, but also as agents for the treatment of autoimmune disorders.

Converting relapsing remitting to secondary progressive experimental allergic encephalomyelitis (EAE) by ultraviolet B irradiation

We induced experimental allergic encephalomyelitis (EAE) in SJL/J mice, an animal model for multiple sclerosis (MS), using myelin oligodendrocyte glycoprotein (MOG)(92-106) peptide, following ultraviolet (UV) irradiation. While all control mice developed relapsing-remitting (RR)-EAE, UV irradiation induced secondary progressive (SP)-EAE in some of the mice. Although mild demyelination was observed with T cell infiltration in RR-EAE, large demyelinating lesions developed in SP-EAE with massive macrophage and neutrophil infiltration and immunoglobulin deposition, but with little T cell infiltration. UV irradiation induced higher anti-MOG antibody responses. In SP-EAE, lymphoproliferative responses and interferon-gamma production were decreased without alteration of interleukin-4.

CpG-DNA as immune response modifier

Toll-like receptors (TLRs) have been recognized to play a fundamental role in the recognition of microbial pathogens and the activation of innate immunity. However, it has also turned out that triggering of TLRs with purified compounds or synthetic ligands represents a powerful means to modulate innate as well as adaptive immune responses. Among the substances currently under investigation as immune response modifiers CpG-DNA has gained particular interest. One reason for this is the feasibility to easily synthesize and modify immunostimulatory CpG-containing oligodeoxynucleotides (CpG-ODNs). This review deals with the structural needs of CpG-ODNs. CpG-ODNs are discussed as being composed of distinct building blocks (e.g. sequence strings, backbone modifications) giving rise to a concept of structural modules within CpG-ODNs.

CG sequence- and phosphorothioate backbone modification-dependent activation of the NF-kappaB-responsive gene expression by CpG-oligodeoxynucleotides in human RPMI 8226 B cells

Oligodeoxynucleotides containing CpG motifs (CpG-ODNs) have gained attention because of their stimulatory effects on innate immune responses. CpG-ODN 1826 containing two GACGTT motifs is well known to activate the mouse immune cells while CpG-ODN 2006 containing three GTCGTT motifs is optimal for human cells. We have shown that stimulation of the human B cell line RPMI 8226 with CpG-ODN 1826 or 2006 results in the activation of IL-8 promoter and nuclear localization of NF-kappaB in the CG sequence- and phosphorothioate backbone modification-dependent manner. It was also demonstrated that myeloid differentiation protein and tumor necrosis factor receptor-associated factor 6 are involved in the signal transduction pathway triggered by the CpG-ODNs. Furthermore, phosphorothioate-modified CpG-ODN 1826 led to induce the NF-kappaB-responsive inflammatory cytokine gene expression in the cells. Experimental results indicated that the phosphorothioate derivative of CpG-ODN 1826 not only activates the mouse immune cells, but also stimulates NF-kappaB responsive gene expression in the human B cell line.

CpG immunostimulatory sequences enhance contact hypersensitivity responses in mice

Bacterial DNA and synthetic cytidine-phosphate-guanosine-oligodeoxynucleotides (CpG ODN) potently activate dendritic cells (DC) and therefore have been proposed as adjuvants for vaccination strategies. Although CpG ODN are considered as safe adjuvants this study shows that CpG ODN are responsible for enhanced antigen-specific skin inflammatory reactions. We used the murine model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB) in which hapten-specific CD8+T cytotoxic 1 cells are effector cells. Subcutaneous injection of CpG ODN, 1 d before sensitization enhanced the CHS response to DNFB and resulted in increased recruitment of CD8+ T cells at the challenge sites, whereas control ODN injection did not have any effect. This effect was local and not systemic as it was only observed when DNFB was applied at the same site as the CpG motifs. CpG ODN-induced enhancement of CHS was due to increased antigen-presenting cell functions of DC since: (i) CpG ODN-injected skin revealed upregulated expression of major histocompatibility complex class II, CD80, and CD86 molecules and (ii) CpG ODN treatment of DNFB-derivatized DC enhanced the intensity of CHS responses after in vivo transfer. Taken together, the results show that CpG ODN may be responsible for immune side-effects such as worsening of T cell-mediated skin diseases.

Distinct roles for IP-10/CXCL10 in three animal models, Theiler's virus infection, EAE, and MHV infection, for multiple sclerosis: implication of differing roles for IP-10

Theiler's murine encephalomyelitis virus (TMEV) causes demyelination with inflammation of the central nervous system (CNS) in mice and is used as an animal model for multiple sclerosis (MS). Interferon-gamma inducible protein-10 kDa (IP-10) is a CXC chemokine and a chemoattractant for CXCR3+ T cells. IP-10 mRNA is expressed in the CNS during TMEV infection. However, administration of anti-IP-10 serum caused no difference in clinical signs, inflammation, demyelination, virus persistence or anti-virus antibody response in TMEV infection, while levels of virus specific and autoreactive lymphoproliferation increased. This likely reflects a difference in the pathogenesis of TMEV infection from that of two other animal models for MS, mouse hepatitis virus infection and experimental allergic encephalomyelitis (EAE), where blocking of IP-10 resulted in clinical and histological improvement with suppression of antigen specific lymphoproliferation. In this review, we compare and contrast the roles of IP-10 between the three animal models for MS, and discuss the relevance to MS patients with different clinical courses.

Safety of CpG oligodeoxynucleotides in veterinary species

Bacterial DNA and synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in particular sequence contexts (CpG ODN) are recognized as a danger signal by the innate immune system of vertebrates. For this reason, CpG ODNs have a potential application as both an adjuvant and nonspecific immune modulator and are currently being evaluated in a number of human and veterinary clinical trials. Given their potent immunostimulatory activity, CpG ODNs could possibly induce adverse reactions. As all adjuvants and immune modulators must be nontoxic to meet safety requirements, it was essential to address the safety aspects of CpG ODNs. The current review summarizes experiments carried out to date to establish the safety of CpG ODNs in animals.

NF-kappaB-dependent regulation of tumor necrosis factor-alpha gene expression by CpG-oligodeoxynucleotides

Immunostimulatory activities of synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODNs) have gained attention as potentially useful immunotherapeutics. However, CpG-ODNs induce harmful and lethal shock effects because they greatly enhance the sequence-dependent induction of tumor necrosis factor-alpha (TNF-alpha). We have shown that phosphorothioate-modified oligodeoxynucleotides (PS-ODNs) of the CpG-ODN 1826 stimulate TNF-alpha gene expression, TNF-alpha promoter activity, IkappaB degradation, and NF-kappaB activation at higher levels compared with its phosphodiester ODN (PO-ODN). In contrast to the effects of CpG-ODN 1826, PS-ODN of the CpG-ODN 2006 showed lower stimulatory activities than its PO-ODN. Using transient transfection, it was found that myeloid differentiation protein (MyD88) and tumor necrosis factor receptor-associated factor 6 are commonly required for activation of the TNF-alpha promoter by various CpG-ODNs with different potencies. These results strongly suggest a possibility to optimally activate the innate immune responses by modulating the potency of CpG-ODNs via sequence rearrangement and phosphorothioate backbone modification.

A recombinant fragment of human SP-D reduces allergic responses in mice sensitized to house dust mite allergens

C57Bl6 mice sensitized to Dermatophagoides pteronyssinus and challenged with D. pteronyssinus allergen extract given intranasally followed by treatment with intranasal applications of a 60-kDa truncated, trimeric recombinant form of human SP-D (rfhSP-D) showed a significant reduction in serum IgE, IgG1, peripheral blood eosinophilia and airway hyperresponsiveness compared to saline or bovine serum albumin-treated controls. Intracellular cytokine staining of lung and spleen homogenates showed increases in interleukin (IL)-12 production in lung tissue and normalization of IL-12 and interferon (IFN)-gamma in spleen tissue. In previous studies we demonstrated the effectiveness of native SP-D and rfhSP-D in down-regulating allergic responses to allergens of Aspergillus fumigatus. The results reported here indicate that rfhSP-D can suppress the development of allergic symptoms in sensitized mice challenged with allergens of the common house dust mite.

Effect of intranasal administration of semliki forest virus recombinant particles expressing reporter and cytokine genes on the progression of experimental autoimmune encephalomyelitis

We have initiated studies to determine the feasibility of employing the Semliki Forest virus (SFV) expression system as a central nervous system (CNS) vector. We investigated the effects of infecting Balb/c mice intranasally (i.n.) with recombinant SFV particles expressing the enhanced green fluorescent protein (EGFP) reporter gene. EGFP expression was detected by fluorescence microscopy in the olfactory bulb as early as 1 day postinfection. No pathological changes were associated with infection. Viral RNA could be detected in the olfactory mucosa only, whereas fluorescence was detected in axons in the olfactory bulb, indicating that only the expressed protein was present. A vector expressing interleukin 10 (IL-10) was constructed and shown to induce good cytokine expression in cultured cells. IL-10 expression in the nasal passage and olfactory bulb of infected mice was enhanced following i.n. administration of such particles. Mice induced for experimental autoimmune encephalomyelitis (EAE) were treated i.n. with vectors expressing EGFP and IL-10 and with empty vector. The EGFP-expressing and empty vectors were found to exacerbate EAE, whereas that expressing IL-10 ameliorated EAE. It is concluded that the mice showed a significant biological response when treated i.n. with recombinant SFV particles and that such particles administered by the i.n. route have potential as a noninvasive vector for protein delivery to the CNS.

CpG DNA in the prevention and treatment of infections

Microbial infection is sensed by Toll-like receptors (TLRs) on innate immune cells. Among the ten so far defined TLRs, TLR9 and its ligand are peculiar. TLR9 recognises bacterial DNA characterised by the abundance of unmethylated CpG dinucleotides, which distinguish bacterial DNA (CpG DNA) from mammalian DNA. Moreover, TLR9 shows a restricted cellular and subcellular pattern of expression. In contrast to other TLR agonists, CpG DNA is superior in activation of dendritic dells and induction of costimulatory cytokines such as interleukin (IL)-12 and IL-18. This qualifies CpG DNA as a Th1-promoting adjuvant. During infection, recognition of CpG DNA of intracellular pathogens skews and fine-tunes the ongoing immune response and induces long-lasting Th1 milieus. Thus, CpG DNA might play an important role in driving the immune system to a Th1 profile, preventing undesired Th2 milieus that might favour induction of allergic responses. Since CpG DNA can be synthesised with high purity and sequence fidelity, synthetic CpG DNA will become an important agent for Th1 instruction and be an effective adjuvant during vaccination.

Gene therapy in autoimmune, demyelinating disease of the central nervous system

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system (CNS), where suspected autoimmune attack causes nerve demyelination and progressive neurodegeneration and should benefit from both anti-inflammatory and neuroprotective strategies. Although neuroprotection strategies are relatively unexplored in MS, systemic delivery of anti-inflammatory agents to people with MS has so far been relatively disappointing. This is most probably because of the limited capacity of these molecules to enter the target tissue, because of exclusion by the blood-brain barrier. The complex natural history of MS also means that any therapeutic agents will have to be administered long-term. Gene therapy offers the possibility of site-directed, long-term expression, and is currently being preclinically investigated in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. While some immune effects may be targeted in the periphery using DNA vaccination, strategies both viral and nonviral are being developed to target agents into the CNS either via direct delivery or using the trafficking properties of cell-carrier systems. Targeting of leucocyte activation, cytokines and nerve growth factors have shown some promising benefit in animal EAE systems, the challenge will be their application in clinical use.

Axonal injury heralds virus-induced demyelination

Axonal pathology has been highlighted as a cause of neurological disability in multiple sclerosis. The Daniels (DA) strain of Theiler's murine encephalomyelitis virus infects the gray matter of the central nervous system of mice during the acute phase and persistently infects the white matter of the spinal cord during the chronic phase, leading to demyelination. This experimental infection has been used as an animal model for multiple sclerosis. The GDVII strain causes an acute fatal polioencephalomyelitis without demyelination. Injured axons were detected in normal appearing white matter at 1 week after infection with DA virus by immunohistochemistry using antibodies specific for neurofilament protein. The number of damaged axons increased throughout time. By 2 and 3 weeks after infection, injured axons were accompanied by parenchymal infiltration of Ricinus communis agglutinin I(+) microglia/macrophages, but never associated with perivascular T-cell infiltration or obvious demyelination until the chronic phase. GDVII virus infection resulted in severe axonal injury in normal appearing white matter at 1 week after infection, without the presence of macrophages, T cells, or viral antigen-positive cells. The distribution of axonal injury observed during the early phase corresponded to regions where subsequent demyelination occurs during the chronic phase. The results suggest that axonal injury might herald or trigger demyelination.

Suppressive DNA vaccination in myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis involves a T1-biased immune response

Vaccination with DNA encoding a myelin basic protein peptide suppresses Lewis rat experimental autoimmune encephalomyelitis (EAE) induced with the same peptide. Additional myelin proteins, such as myelin oligodendrocyte glycoprotein (MOG), may be important in multiple sclerosis. Here we demonstrate that DNA vaccination also suppresses MOG peptide-induced EAE. MOG(91-108) is encephalitogenic in DA rats and MHC-congenic LEW.1AV1 (RT1(av1)) and LEW.1N (RT1(n)) rats. We examined the effects of DNA vaccines encoding MOG(91-108) in tandem, with or without targeting of the hybrid gene product to IgG. In all investigated rat strains DNA vaccination suppressed clinical signs of EAE. There was no requirement for targeting the gene product to IgG, but T1-promoting CpG DNA motifs in the plasmid backbone of the construct were necessary for efficient DNA vaccination, similar to the case in DNA vaccination in myelin basic protein-induced EAE. We failed to detect any effects on ex vivo MOG-peptide-induced IFN-gamma, TNF-alpha, IL-6, IL-4, IL-10, and brain-derived neurotropic factor expression in splenocytes or CNS-derived lymphocytes. In CNS-derived lymphocytes, Fas ligand expression was down-regulated in DNA-vaccinated rats compared with controls. However, MOG-specific IgG2b responses were enhanced after DNA vaccination. The enhanced IgG2b responses together with the requirement for CpG DNA motifs in the vaccine suggest a protective mechanism involving induction of a T1-biased immune response.

Development of short non-CpG phosphodiester oligonucleotides as immune stimulatory agents

We have previously reported that DNA isolated from Mycobacterium phlei (M. phlei) stimulates the synthesis of cytokines by monocytes and macrophages independently of the presence of unmethylated CpG motifs. Oligonucleotides as small as five to six bases isolated from M. phlei DNA have been found to induce cytokine synthesis. In the present study, we have investigated the potential for such CpG-lacking DNA to act as an immune stimulant. A series of six base length phosphodiester oligonucleotides derived from the genome of M. phlei were synthesised and tested for their ability to induce the synthesis of cytokines by murine, non-human primate (rhesus macaques and chimpanzee) and human peripheral blood mononuclear cells. The results show that phosphodiester oligonucleotides with a 5'GGGxGG3' sequence where x is A, C, G or T have the ability to induce the synthesis of IL-1beta, IL-6, IL10 or IL-12 by non-human primate and human PBMC, murine cells being unresponsive. The phosphodiester 5'GGGxGG3' oligonucleotides were shown to be stable in human serum, with a half-life of approximately 72 h. The addition of aluminium hydroxide to these 5'GGGxGG3' oligonucleotides potentiated, in a concentration-dependent manner, the synthesis of IL-12 by human peripheral blood mononuclear cells. These phosphodiester six base length non-CpG motif oligonucleotides may have potential as immunopotentiators for vaccines.

Bacterial CpG-DNA aggravates immune complex glomerulonephritis: role of TLR9-mediated expression of chemokines and chemokine receptors

Immune complex glomerulonephritis (GN) often deteriorates during infection with viruses and bacteria that, in contrast to mammals, have DNA that contains many unmethylated CpG motifs. Balb/c mice with horse apoferritin-induced GN (HAF-GN) were treated with either saline, CpG-oligodeoxynucleotides (ODN), or control GpC-ODN. Only CpG-ODN exacerbated HAF-GN with an increase of glomerular macrophages, which was associated with massive albuminuria and increased renal MCP-1/CCL2, RANTES/CCL5, CCR1, CCR2, and CCR5 mRNA expression. CpG-ODN induced a Th1 response as indicated by serum anti-HAF IgG(2a) titers, mesangial IgG(2a) deposits, and splenocyte IFN-gamma secretion. Messenger RNA for the CpG-DNA receptor Toll-like reeptor 9 (TLR9) was present in kidneys with HAF-GN but not in normal kidneys. The source of TLR9 mRNA in HAF-GN could be infiltrating macrophages or intrinsic renal cells, e.g., mesangial cells; but, in vitro, only murine J774 macrophages expressed TLR9. In J774 cells, CpG-ODN induced the chemokines MCP-1/CCL2 and RANTES/CCL5 and the chemokine receptors CCR1 and CCR5. It is concluded that CpG-DNA can aggravate preexisting GN via a shift toward a Th1 response but also by a novel pathway involving TLR9-mediated chemokine and chemokine receptor expression by macrophages, which may contribute to the enhanced glomerular macrophage recruitment and activation. This mechanism may be relevant during infection-triggered exacerbation of human immune-complex GN and other immune-mediated diseases in general.