Experimental autoimmune encephalomyelitis in mice: genetic control of susceptibility

Endogenous self-peptides guard immune privilege of the central nervous system

Despite the presence of strategically positioned anatomical barriers designed to protect the central nervous system (CNS), it is not entirely isolated from the immune system1,2. In fact, it remains physically connected to, and can be influenced by, the peripheral immune system1. How the CNS retains such responsiveness while maintaining an immunologically unique status remains an outstanding question. Here, in searching for molecular cues that derive from the CNS and enable its direct communication with the immune system, we identified an endogenous repertoire of CNS-derived regulatory self-peptides presented on major histocompatibility complex class II (MHC-II) molecules in the CNS and at its borders. During homeostasis, these regulatory self-peptides were found to be bound to MHC-II molecules throughout the path of lymphatic drainage from the brain to its surrounding meninges and its draining cervical lymph nodes. However, in neuroinflammatory disease, the presentation of regulatory self-peptides diminished. After boosting the presentation of these regulatory self-peptides, a population of suppressor CD4+ T cells was expanded, controlling CNS autoimmunity in a CTLA-4- and TGFβ-dependent manner. CNS-derived regulatory self-peptides may be the molecular key to ensuring a continuous dialogue between the CNS and the immune system while balancing overt autoreactivity. This sheds light on how we conceptually think about and therapeutically target neuroinflammatory and neurodegenerative diseases.

Pharmacological insights into autophagy modulation in autoimmune diseases

As a cellular bulk degradation and survival mechanism, autophagy is implicated in diverse biological processes. Genome-wide association studies have revealed the link between autophagy gene polymorphisms and susceptibility of autoimmune diseases including systemic lupus erythematosus (SLE) and inflammatory bowel disease (IBD), indicating that autophagy dysregulation may be involved in the development of autoimmune diseases. A series of autophagy modulators have displayed protective effects on autoimmune disease models, highlighting the emerging role of autophagy modulators in treating autoimmune diseases. This review explores the roles of autophagy in the autoimmune diseases, with emphasis on four major autoimmune diseases [SLE, rheumatoid arthritis (RA), IBD, and experimental autoimmune encephalomyelitis (EAE)]. More importantly, the therapeutic potentials of small molecular autophagy modulators (including autophagy inducers and inhibitors) on autoimmune diseases are comprehensively analyzed.

CD4 Deficiency Causes Poliomyelitis and Axonal Blebbing in Murine Coronavirus-Induced Neuroinflammation

Mouse hepatitis virus (MHV) is a murine betacoronavirus (m-CoV) that causes a wide range of diseases in mice and rats, including hepatitis, enteritis, respiratory diseases, and encephalomyelitis in the central nervous system (CNS). MHV infection in mice provides an efficient cause-effect experimental model to understand the mechanisms of direct virus-induced neural-cell damage leading to demyelination and axonal loss, which are pathological features of multiple sclerosis (MS), the most common disabling neurological disease in young adults. Infiltration of T lymphocytes, activation of microglia, and their interplay are the primary pathophysiological events leading to disruption of the myelin sheath in MS. However, there is emerging evidence supporting gray matter involvement and degeneration in MS. The investigation of T cell function in the pathogenesis of deep gray matter damage is necessary. Here, we employed RSA59 (an isogenic recombinant strain of MHV-A59)-induced experimental neuroinflammation model to compare the disease in CD4-/- mice with that in CD4+/+ mice at days 5, 10, 15, and 30 postinfection (p.i.). Viral titer estimation, nucleocapsid gene amplification, and viral antinucleocapsid staining confirmed enhanced replication of the virions in the absence of functional CD4+ T cells in the brain. Histopathological analyses showed elevated susceptibility of CD4-/- mice to axonal degeneration in the CNS, with augmented progression of acute poliomyelitis and dorsal root ganglionic inflammation rarely observed in CD4+/+ mice. Depletion of CD4+ T cells showed unique pathological bulbar vacuolation in the brain parenchyma of infected mice with persistent CD11b+ microglia/macrophages in the inflamed regions on day 30 p.i. In summary, the current study suggests that CD4+ T cells are critical for controlling acute-stage poliomyelitis (gray matter inflammation), chronic axonal degeneration, and inflammatory demyelination due to loss of protective antiviral host immunity.IMPORTANCE The current trend in CNS disease biology is to attempt to understand the neural-cell-immune interaction to investigate the underlying mechanism of neuroinflammation, rather than focusing on peripheral immune activation. Most studies in MS are targeted toward understanding the involvement of CNS white matter. However, the importance of gray matter damage has become critical in understanding the long-term progressive neurological disorder. Our study highlights the importance of CD4+ T cells in safeguarding neurons against axonal blebbing and poliomyelitis from murine betacoronavirus-induced neuroinflammation. Current knowledge of the mechanisms that lead to gray matter damage in MS is limited, because the most widely used animal model, experimental autoimmune encephalomyelitis (EAE), does not present this aspect of the disease. Our results, therefore, add to the existing limited knowledge in the field. We also show that the microglia, though important for the initiation of neuroinflammation, cannot establish a protective host immune response without the help of CD4+ T cells.

Immune Relevant and Immune Deficient Mice: Options and Opportunities in Translational Research

In 1989 ILAR published a list and description of immunodeficient rodents used in research. Since then, advances in understanding of molecular mechanisms; recognition of genetic, epigenetic microbial, and other influences on immunity; and capabilities in manipulating genomes and microbiomes have increased options and opportunities for selecting mice and designing studies to answer important mechanistic and therapeutic questions. Despite numerous scientific breakthroughs that have benefitted from research in mice, there is debate about the relevance and predictive or translational value of research in mice. Reproducibility of results obtained from mice and other research models also is a well-publicized concern. This review summarizes resources to inform the selection and use of immune relevant mouse strains and stocks, aiming to improve the utility, validity, and reproducibility of research in mice. Immune sufficient genetic variations, immune relevant spontaneous mutations, immunodeficient and autoimmune phenotypes, and selected induced conditions are emphasized.

Inclusion of non-target antigen in vaccination favors generation of OVA specific CD4 memory T cells

Inducing long-lived memory T cells by sub-unit vaccines has been a challenge. Subunit vaccines containing single immunogenic target antigen from a given pathogen have been designed with the presumption of mimicking the condition associated with natural infection, but fail to induce quality memory responses. In this study, we have included non-target antigens with vaccine candidate, OVA, in the inoculum containing TLR ligands to suffice the minimal condition of pathogen to provoke immune response. We found that inclusion of immunogenic HEL (hen egg lysozyme) or poorly immunogenic MBP (Myelin Basic protein) non-target antigen enhances the OVA specific CD4 T cell responses. Interestingly, poorly immunogenic MBP was found to strongly favor the generation of OVA specific memory CD4 T cells. MBP not only improves magnitude of T cell response but also promotes the T cells to undergo higher cycles of division, one of the characteristic of central memory T cells. Inclusion of MBP with vaccine targets was also found to promote multiple cytokine producing CD4 T cells. We also found that challenge of host with non-target antigen MBP favors generation of central Memory T cells.

Multiple sclerosis: experimental models and reality

One of the most frequent statements, provided in different variations in the introduction of experimental studies on multiple sclerosis (MS), is that "Multiple sclerosis is a demyelinating autoimmune disease and experimental autoimmune encephalomyelitis (EAE) is a suitable model to study its pathogenesis". However, so far, no single experimental model covers the entire spectrum of the clinical, pathological, or immunological features of the disease. Many different models are available, which proved to be highly useful for studying different aspects of inflammation, demyelination, remyelination, and neurodegeneration in the central nervous system. However, the relevance of results from such models for MS pathogenesis has to be critically validated. Current EAE models are mainly based on inflammation, induced by auto-reactive CD4+ T-cells, and these models reflect important aspects of MS. However, pathological data and results from clinical trials in MS indicate that CD8+ T-cells and B-lymphocytes may play an important role in propagating inflammation and tissue damage in established MS. Viral models may reflect key features of MS-like inflammatory demyelination, but are difficult to use due to their very complex pathogenesis, involving direct virus-induced and immune-mediated mechanisms. Furthermore, evidence for a role of viruses in MS pathogenesis is indirect and limited, and an MS-specific virus infection has not been identified so far. Toxic models are highly useful to unravel mechanisms of de- and remyelination, but do not reflect other important aspects of MS pathology and pathogenesis. For all these reasons, it is important to select the right experimental model to answer specific questions in MS research.

Robust effects of genetic background on responses to subarachnoid hemorrhage in mice

Outcome varies among patients with subarachnoid hemorrhage but known prognostic factors explain only a small portion of the variation in outcome. We hypothesized that individual genetic variations influence brain and vascular responses to subarachnoid hemorrhage and investigated this using inbred strains of mice.Subarachnoid hemorrhage was induced in seven inbred and a chromosome 7 substitution strain of mouse. Cerebral blood flow, vasospasm of the middle cerebral artery, and brain injury were assessed. After 48 h of subarachnoid hemorrhage, mice showed significant middle cerebral artery vasospasm that correlated positively with reduction in cerebral blood flow at 45 min. Mice also had increased neuronal injury compared to sham controls; A/J and C57BL/6 J strains represented the most and least severe, respectively. However, brain injury did not correlate with cerebral blood flow reduction at 45 min or with vasospasm at 48 h. Chromosome 7 substitution did not influence the degree of vasospasm or brain injury.Our data suggested that mouse genetic background influences outcome of subarachnoid hemorrhage. Investigations into the genetic factors causing these inter-strain differences may provide insight into the etiology of the brain damage following subarachnoid hemorrhage. These findings also have implications for animal modeling of disease and suggest that genetic differences may also modulate outcome in other cardiovascular diseases.

Time-Dependent Progression of Demyelination and Axonal Pathology in MP4-Induced Experimental Autoimmune Encephalomyelitis

Background

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by inflammation, demyelination and axonal pathology. Myelin basic protein/proteolipid protein (MBP-PLP) fusion protein MP4 is capable of inducing chronic experimental autoimmune encephalomyelitis (EAE) in susceptible mouse strains mirroring diverse histopathological and immunological hallmarks of MS. Limited availability of human tissue underscores the importance of animal models to study the pathology of MS.

Methods

Twenty-two female C57BL/6 (B6) mice were immunized with MP4 and the clinical development of experimental autoimmune encephalomyelitis (EAE) was observed. Methylene blue-stained semi-thin and ultra-thin sections of the lumbar spinal cord were assessed at the peak of acute EAE, three months (chronic EAE) and six months after onset of EAE (long-term EAE). The extent of lesional area and inflammation were analyzed in semi-thin sections on a light microscopic level. The magnitude of demyelination and axonal damage were determined using electron microscopy. Emphasis was put on the ventrolateral tract (VLT) of the spinal cord.

Results

B6 mice demonstrated increasing demyelination and severe axonal pathology in the course of MP4-induced EAE. In addition, mitochondrial swelling and a decrease in the nearest neighbor neurofilament distance (NNND) as early signs of axonal damage were evident with the onset of EAE. In semi-thin sections we observed the maximum of lesional area in the chronic state of EAE while inflammation was found to a similar extent in acute and chronic EAE. In contrast to the well-established myelin oligodendrocyte glycoprotein (MOG) model, disease stages of MP4-induced EAE could not be distinguished by assessing the extent of parenchymal edema or the grade of inflammation.

Conclusions

Our results complement our previous ultrastructural studies of B6 EAE models and suggest that B6 mice immunized with different antigens constitute useful instruments to study the diverse histopathological aspects of MS.

Chloroquine treatment enhances regulatory T cells and reduces the severity of experimental autoimmune encephalomyelitis

Background

The modulation of inflammatory processes is a necessary step, mostly orchestrated by regulatory T (Treg) cells and suppressive Dendritic Cells (DCs), to prevent the development of deleterious responses and autoimmune diseases. Therapies that focused on adoptive transfer of Treg cells or their expansion in vivo achieved great success in controlling inflammation in several experimental models. Chloroquine (CQ), an anti-malarial drug, was shown to reduce inflammation, although the mechanisms are still obscure. In this context, we aimed to access whether chloroquine treatment alters the frequency of Treg cells and DCs in normal mice. In addition, the effects of the prophylactic and therapeutic treatment with CQ on Experimental Autoimmune Encephalomyelitis (EAE), an experimental model for human Multiple Sclerosis, was investigated as well.

Methodology/Principal Findings

EAE was induced in C57BL/6 mice by immunization with myelin oligodendrocyte glycoprotein (MOG_35–55) peptide. C57BL/6 mice were intraperitoneally treated with chloroquine. Results show that the CQ treatment provoked an increase in Treg cells frequency as well as a decrease in DCs. We next evaluated whether prophylactic CQ administration is capable of reducing the clinical and histopathological signs of EAE. Our results demonstrated that CQ-treated mice developed mild EAE compared to controls that was associated with lower infiltration of inflammatory cells in the central nervous system CNS) and increased frequency of Treg cells. Also, proliferation of MOG_35–55-reactive T cells was significantly inhibited by chloroquine treatment. Similar results were observed when chloroquine was administrated after disease onset.

Conclusion

We show for the first time that CQ treatment promotes the expansion of Treg cells, corroborating previous reports indicating that chloroquine has immunomodulatory properties. Our results also show that CQ treatment suppress the inflammation in the CNS of EAE-inflicted mice, both in prophylactic and therapeutic approaches. We hypothesized that the increased number of regulatory T cells induced by the CQ treatment is involved in the reduction of the clinical signs of EAE.

Determinants of central nervous system adult neurogenesis are sex, hormones, mouse strain, age, and brain region

Multiple sclerosis is a sexually dimorphic (SD) disease that causes oligodendrocyte death, but SD of glial cells is poorly studied. Here, we analyze SD of neural progenitors in 6-8 weeks and 6-8 months normal C57BL/6, SJL/J, and BALB/c mice in the subventricular zone (SVZ), dorsolateral horn (DLC), corpus callosum (CC), and parenchyma. With a short 2-h bromodeoxyuridine (BrdU) pulse, no gender and strain differences are present at 6-8 weeks. At 6-8 months, the number of BrdU(+) cells decreases twofold in each sex, strain, and region, indicating that a common aging mechanism regulates BrdU incorporation. Strikingly, 2× more BrdU(+) cells are found in all brain regions in 6-8 months C57BL/6 females versus males, no gender differences in 6-8 months SJL/J, and fewer BrdU(+) cells in females versus males in BALB/cs. The number of BrdU(+) cells modestly fluctuates throughout the estrous cycle in C57BL/6 and SJLs. Castration causes a dramatic increase in BrdU(+) cells in SVZ and DLC. These findings indicate that testosterone is a major regulator of adult neural proliferation. At 6-8 months, the ratio of PDGFRα(+) cells in the CC to BrdU(+) cells in the DLC of both strains, sexes, estrous cycle, and castrated mice was essentially the same, suggesting that BrdU(+) cells in the DLC differentiate into CC oligodendrocytes. The ratio of TUNEL(+) to BrdU(+) cells does not match proliferation, indicating that these events are differentially regulated. Differential regulation of these two processes leads to the variation in glial numbers between gender and strain. Explanations of neural proliferation based upon data from one sex or strain may be very misleading.

Differential patterns of spinal cord pathology induced by MP4, MOG peptide 35-55, and PLP peptide 178-191 in C57BL/6 mice

In this study we demonstrate that experimental autoimmune encephalomyelitis (EAE) induced by the MBP-PLP fusion protein MP4, MOG peptide 35-55, or PLP peptide 178-191 in C57BL/6 mice, respectively, displays distinct features of CNS pathology. Major differences between the three models resided in (i) the region-/tract-specificity and disseminated nature of spinal cord degeneration, (ii) the extent and kinetics of demyelination, and (iii) the involvement of motoneurons in the disease. In contrast, axonal damage was present in all models and to a similar extent, proposing this feature as a possible morphological correlate for the comparable chronic clinical course of the disease induced by the three antigens. The data suggest that the antigen targeted in autoimmune encephalomyelitis is crucial to the induction of differential histopathological disease manifestations. The use of MP4-, MOG:35-55-, and PLP:178-191-induced EAE on the C57BL/6 background can be a valuable tool when it comes to reproducing and studying the structural-morphological diversity of multiple sclerosis.

Differential levels of resistance to disease induction and development of relapsing experimental autoimmune encephalomyelitis in two H-2b-restricted mouse strains

Besides the major histocompatibility complex (MHC) genes, background genes are believed to influence the encephalitogenicity of SJL(H-2(s)) and B10.S (H-2(s)) mice responding to myelin basic protein (MBP). A new mouse strain was constructed to study the effects of the SJL genetic background in mice responding to H-2(b)-restricted neuroantigens. Although the SJL.B (H-2(b)) mouse remained resistant to MBP in active EAE induction, the disease severity was uniformly higher in MOG-induced active EAE and in MBP-induced adoptive EAE when compared to those of B6 (H-2(b)) mice. Treatment of mice with anti-CD25 antibodies prior to immunization caused 60% of SJL.B mice to become susceptible to MBP-induced EAE while only 14% of B6 mice were converted. In addition, MOG-induced EAE in SJL.B mice followed a remitting-relapsing disease course while B6 mice only exhibited monophasic or chronic episodes. The new SJL.B mouse strain provides a valuable tool for studying EAE resistance and remitting-relapsing disease in H-2(b) mice.

Delineating the impact of neuroantigen vs genetic diversity on MP4-induced EAE of C57BL/6 and B6.129 mice

MBP-PLP fusion protein (MP4)-induced experimental autoimmune encephalomyelitis (EAE) is a model for multiple sclerosis (MS) that encompasses both a time-dependent attack on central nervous system (CNS) regions and a B cell component, mirroring important features of human multiple sclerosis. Comparing C57BL/6 with B6.129 mice immunized with MP4, we point out similarities regarding these hallmarks and thus propose that they are largely dependent on the nature of the MP4 antigen itself, while differences between the two strains suggest that additional fine-tuning is brought about by the genetic repertoire of the animal. Overall, our data imply that (i) the interplay between both the antigenic trigger and genetic variables can define the outcome of MP4-induced autoimmune encephalomyelitis in C57BL/6 and B6.129 mice and (ii) that MP4 is not only a strong neuroantigen when it comes to reproducing the dynamics in effector mechanisms as is typical of the disease but also a promising agent for studying interindividual heterogeneity derived from genetic diversity in EAE/MS.

Differential response of C57BL/6J mouse and DBA/2J mouse to optic nerve crush

Background

Retinal ganglion cell (RGC) death is the final consequence of many blinding diseases, where there is considerable variation in the time course and severity of RGC loss. Indeed, this process appears to be influenced by a wide variety of genetic and environmental factors. In this study we explored the genetic basis for differences in ganglion cell death in two inbred strains of mice.

Results

We found that RGCs are more susceptible to death following optic nerve crush in C57BL/6J mice (54% survival) than in DBA/2J mice (62% survival). Using the Illumina Mouse-6 microarray, we identified 1,580 genes with significant change in expression following optic nerve crush in these two strains of mice. Our analysis of the changes occurring after optic nerve crush demonstrated that the greatest amount of change (44% of the variance) was due to the injury itself. This included changes associated with ganglion cell death, reactive gliosis, and abortive regeneration. The second pattern of gene changes (23% of the variance) was primarily related to differences in gene expressions observed between the C57BL/6J and DBA/2J mouse strains. The remaining changes in gene expression represent interactions between the effects of optic nerve crush and the genetic background of the mouse. We extracted one genetic network from this dataset that appears to be related to tissue remodeling. One of the most intriguing sets of changes included members of the crystallin family of genes, which may represent a signature of pathways modulating the susceptibility of cells to death.

Conclusion

Differential responses to optic nerve crush between two widely used strains of mice were used to define molecular networks associated with ganglion cell death and reactive gliosis. These results form the basis for our continuing interest in the modifiers of retinal injury.

In vitro and in vivo pharmacological models to assess demyelination and remyelination

In making a selection of cellular tools and animal models for generating screening assays in the search for new drugs, one needs to take into consideration the practicality of their use in the drug discovery process. Conducting high-throughput primary screens using libraries of small molecules, close to 1 million members in size, requires the generation of large numbers of cells which are easily acquired, reliably enriched, and reproducibly responsive to standard positive controls. These cells need to be similar in form and function to their counterparts in human disease. In vitro assays that can be mechanized by using robots can therefore save time and costs. In selecting in vivo models, consideration must be given to the species and strain of animal chosen, the appropriateness of the model to human disease, the extent of animal husbandry required during the in-life pharmacological assessment, the technical aspects of generating the model and harvesting the tissues for analyses, the cost of research tools in terms of time and money (demyelinating and remyelinating agents, amount of compound to be generated), and the length of time required for drug testing in the model. A consideration of the translational aspects of the in vivo model compared to those used in the clinic is also important. These themes will be developed with examples for drug discovery in the field of CNS demyelination and repair, specifically as it pertains to multiple sclerosis.

Fundamental differences in the dynamics of CNS lesion development and composition in MP4- and MOG peptide 35-55-induced experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is characterized by a dynamic inflammatory process in which CNS lesions of distinct cellular composition coexist. In particular the formation of B cell plaques has been ascribed an important role as predictor of disease progression. Here we show that the novel MBP-PLP fusion protein (MP4)-induced experimental autoimmune encephalomyelitis (EAE) of C57BL/6 mice fulfils these criteria inducing differential cellular infiltration of B cells, T cells, macrophages and granulocytes and permitting the quantification and staging of the disease. On the contrary, both key features - dynamic CNS inflammation and B cell infiltration - were absent in the classical MOG:35-55-induced EAE of C57BL/6 mice, which was characterized by a static CD4(+) T cell and macrophage-mediated CNS immunopathology throughout the disease. MP4-induced EAE may thus provide a unique opportunity for studying immune-pathomechanisms of the disease that have been previously neglected due to experimental shortcomings in murine EAE.

B cells limit epitope spreading and reduce severity of EAE induced with PLP peptide in BALB/c mice

The role of B cells and antibody in experimental autoimmune encephalomyelitis (EAE) appears to differ based on the identity and state (protein vs. encephalitogenic peptide) of the inducing antigen and the strain of mouse utilized. The involvement of B cells in the induction of EAE by peptides of proteolipid protein (PLP) in BALB/c mice was investigated. Wild-type and B cell-deficient (B cell-/-) mice on the BALB/c background were immunized with overlapping PLP peptides, and the disease course was followed. Although incidence and onset of PLP(180-199)-induced EAE was similar in WT and B cell-/- mice, the clinical course was more severe in B cell-/- mice. During acute disease, proliferation and interferon-gamma production by lymphoid cells from both strains were similar and were elicited predominantly in response to the immunizing antigen. However, during chronic disease lymphoid cells isolated from B cell-/- mice proliferated to a greater extent and produced more interferon-gamma in response to the overlapping peptide PLP185-206 and to the smaller internal peptide PLP185-199 than did WT mice. These data suggest that B cells regulate PLP-induced EAE in BALB/c mice through control of epitope spreading.

Comparing the CNS morphology and immunobiology of different EAE models in C57BL/6 mice - a step towards understanding the complexity of multiple sclerosis

Multiple sclerosis (MS) is a chronic neurodegenerative disease that causes central nervous system (CNS) inflammation and demyelination, affecting approximately two million people worldwide. In humans, different subtypes of the disease have been noted, characterized by distinct clinical courses and different histopathological manifestations. These disease variants likely result from the targeting of different neuroantigens in the CNS and possibly from the involvement of different effector arms of the immune system such as CD4(+) and CD8(+) T cells as well as autoantibodies. Mechanistic studies addressing the pathomechanisms of MS involve experimental autoimmune encephalomyelitis (EAE) in which immunization with neuroantigens is used to elicit the disease. Mechanism-oriented studies of EAE rely mostly on gene-modified mice on the C57BL/6 (B6) background. Here, we discuss how a systematic immuno- and histopathological comparison of the presently available EAE models on the B6 background, i.e. myelin basic protein-proteolipid protein (MBP-PLP) fusion protein (MP4)-, myelin oligodendrocyte glycoprotein (MOG) peptide 35-55- and PLP peptide 178-191-induced EAE, can facilitate our understanding of the complexity of MS. We point out how the development of further models on this basis can help cover the plethora of disease manifestations seen in MS.

High cell surface expression of CD4 allows distinction of CD4(+)CD25(+) antigen-specific effector T cells from CD4(+)CD25(+) regulatory T cells in murine experimental autoimmune encephalomyelitis

Analysis of T regulatory cells (Treg) and T effector cells (Teff) in experimental autoimmune encephalomyelitis is complicated by the fact that both cell types express CD4 and CD25. We demonstrate that encephalitogenic T cells, following antigen recognition, up-regulate cell surface expression of CD4. The CD4(high) sub-population contains all of the antigen response as shown by proliferation and cytokine secretion, and only these cells are capable of transferring EAE to naive animals. On the other hand, a FACS separable CD25(+) sub-population of cells displayed consistent levels of CD4 prior to and after antigen stimulation. These cells displayed characteristics of Treg, such as expressing high levels of the Foxp3 gene and the ability to suppress mitogenic T cell responses.

MP4- and MOG:35-55-induced EAE in C57BL/6 mice differentially targets brain, spinal cord and cerebellum

Mechanism-oriented studies of EAE rely mostly on gene-modified mice on the C57BL/6 background. Here we report that MP4-induced EAE displays characteristic differences in CNS pathology as compared to MOG peptide 35-55-elicited disease. While in the latter, the topology of CNS infiltration remained unchanged throughout the disease, in MP4-induced EAE it was dynamic and stage-dependent shifting from the brain to the spinal cord and finally to the cerebellum. Unlike in the MOG peptide model, the frequencies and sizes of CNS lesions in MP4-induced disease showed a clear correlation with clinical disease severity. These characteristic features of MP4-induced EAE may contribute to modelling the complex spectrum of disease manifestations seen in MS.

CD4+FoxP3+ regulatory T cells gradually accumulate in gliomas during tumor growth and efficiently suppress antiglioma immune responses in vivo

The suppressive activity of regulatory T cells (Treg) has been implicated as an important factor limiting immune mediated destruction of tumor cells. However, not much is known about the presence and function of Treg within tumors. Here we show in a syngeneic murine glioma model a time-dependent accumulation of CD4+FoxP3+ Treg in brain tumors. Further analysis revealed a time-dependent upregulation of CD25, CTLA-4, GITR and CXCR4 on intratumoral CD4+FoxP3+ Treg during tumor growth. Moreover, freshly isolated intratumoral Treg were highly suppressive when tested directly ex vivo. Treatment with anti-CD25 monoclonal antibodies (mAbs) significantly reduced the number of these highly suppressive CD4+FoxP3+ cells within the growing tumor and provoked a CD4 and CD8 T cell dependent destruction of the glioma cells. Combining Treg depletion with administration of blocking CTLA-4 mAbs further boosted glioma-specific CD4+ and CD8+ effector T cells as well as antiglioma IgG2a antibody titers resulting in complete tumor eradication without any signs of autoimmunity. These data illustrate that intratumoral accumulation and activation of CD4+FoxP3+ Treg act as a dominant immune escape mechanism for gliomas and underline the importance of controlling tumor-infiltrating Treg in glioma immunotherapy.

A potential role for estrogen in experimental autoimmune encephalomyelitis and multiple sclerosis

The extensive literature and the work from our laboratory illustrate the large number of complex processes affected by estrogen that might contribute to the striking ability of 17-beta estradiol (E2) and its derivatives to inhibit clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in mice. These effects require sustained exposure to relatively low doses of exogenous hormone and offer better protection when initiated prior to induction of EAE. The E2 mediates inhibition of encephalitogenic T cells, inhibition of cell migration into central nervous system tissue, and neuroprotective effects that promote axon and myelin survival. E2 effects on EAE are mediated through Esr-1 (alpha receptor for E2) but not Esr-2 (beta receptor for E2), as are its anti-inflammatory and neuroprotective effects. A novel finding is that E2 upregulated the expression of FoxP3 that contributes to the activity of CD4 + CD25 + T regulatory cells (Treg). The protective effects of E2 in EAE suggest its use as a therapy for multiple sclerosis (MS). Possible risks may be minimized by using sub-pregnancy levels of exogenous E2 that produced synergistic effects when used in combination with another immunoregulatory therapy. Alternatively, one might envision using E2 derivatives alone or in combination therapies in both male and female MS patients.

MBP-PLP fusion protein-induced EAE in C57BL/6 mice

Gene knock-out and knock-in mice are becoming increasingly indispensable for mechanism-oriented studies of EAE. Most gene-modified mice are on the C57BL/6 background, for which presently there are only two EAE models available, the MOG peptide 35-55 and the PLP 178-191 peptide induced disease. However, because MS is not a single pathogenic entity, different EAE models are required to reproduce and study its various features. Here we are introducing MBP-PLP fusion protein (MP4)-induced EAE for C57BL/6 mice. B cell- and CD8+ T cell-dependence, as well as multi-determinant recognition are among the unique features of this demyelinating EAE.

Comparative analysis of lesion development and intraspinal inflammation in four strains of mice following spinal contusion injury

Susceptibility to neuroinflammatory disease is influenced in part by genetics. Recent data indicate that survival of traumatized neurons is strain dependent and influenced by polygenic loci that control resistance/susceptibility to experimental autoimmune encephalomyelitis (EAE), a model of CNS autoimmune disease. Here, we describe patterns of neurodegeneration and intraparenchymal inflammation after traumatic spinal cord injury (SCI) in mice known to exhibit varying degrees of EAE susceptibility [EAE-resistant (r) or EAE-susceptible (s) mice]. Spinal cords from C57BL/6 (EAE-s), C57BL/10 (EAE-r), BALB/c (EAE-r), and B10.PL (EAE-s) mice were prepared for stereological and immunohistochemical analysis at 6 hours or 3, 7, 14, 28, or 42 days following midthoracic (T9) spinal contusion injury. In general, genetic predisposition to EAE predicted the magnitude of intraparenchymal inflammation but not lesion size/length or locomotor recovery. Specifically, microglia/macrophage activation, recruitment of neutrophils and lymphocytes, and de novo synthesis of MHC class II were greatest in C57BL/6 mice and least in BALB/c mice at all times examined. However, lesion volume and axial spread of neurodegeneration were similar in C57BL/6 and BALB/c mice and were significantly greater than in C57BL/10 or B10.PL mice. Strains with marked intraspinal inflammation also developed the most intense lesion fibrosis. Thus, strain-dependent neuroinflammation was observed after SCI, but without a consistent relationship to EAE susceptibility or lesion progression. Only in C57BL/6 mice was the magnitude of intraspinal inflammation predictive of secondary neurodegeneration, functional recovery, or fibrosis.

Adoptive transfer of myelin basic protein-induced experimental autoimmune encephalomyelitis between SJL and B10.S mice: Correlation of priming milieus with susceptibility and resistance phenotypes

To study the mechanisms of EAE resistance, we directly transfer MBP-primed EAE-susceptible SJL lymph node cells into EAE-resistant B10.S recipients and vice versa. These transfers were unsuccessful because of strong alloreactivity between the two strains. Neonatal tolerance to SJL antigens was induced in B10.S mice and in these hosts MBP-primed SJL lymph node cells readily induce development of adoptive EAE. Conversely, transfer of MBP-primed B10.S lymph node cells into EAE-susceptible (SJL x B10.S)F1 recipients failed to induce EAE. These results are consistent with the notion that the priming milieus in the donor mice affect the expression of susceptible and resistant phenotypes.

Complement and demyelinating disease: no MAC needed?

It has long been accepted that the complement system participates in the onset, evolution, and exacerbation of demyelinating disease, and it is widely suspected that this is accomplished mainly via destruction of nervous tissue by membrane attack complex (MAC)-mediated lysis of oligodendrocytes and neurons. However, recent studies using mutant mice indicate the MAC may not be so important. For example, mice lacking C5 and mice lacking the C5a receptor both develop experimental autoimmune encephalomyelitis (EAE) with the same frequency and intensity as their wild type counterparts. Also, transgenic mice that express C5a exclusively in the central nervous system (CNS) develop EAE that is not remarkably different from that in non-transgenic littermates. Since C5 is required for formation of the MAC, development of fulminant EAE in the absence of this complement protein demonstrates that non-complement-mediated mechanisms of CNS damage are operating. Paradoxically, mice lacking C3, mice lacking the C3a receptor, and mice lacking the complement receptor type 3 develop attenuated EAE, while mice that express C3a exclusively in the CNS develop severe and often fulminant EAE. Based on these newer data, we posit that C3-derived biologically active fragments, rather than C5 and the MAC, are central players in the pathophysiology of complement in EAE.

Neuroimmunoprotective effects of estrogen and derivatives in experimental autoimmune encephalomyelitis: Therapeutic implications for multiple sclerosis

The extensive literature and the work from our laboratory illustrate the large number of complex processes affected by estrogen that might contribute to the striking ability of 17beta-estradiol (E2) and its derivatives to inhibit clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in mice. These effects require sustained exposure to relatively low doses of exogenous hormone and offer better protection when initiated prior to induction of EAE. However, oral ethinyl estradiol (EE) and fluasterone, which lacks estrogenic side effects, could partially reverse clinical EAE when given after the onset of disease. The three main areas discussed in this review include E2-mediated inhibition of encephalitogenic T cells, inhibition of cell migration into central nervous system tissue, and neuroprotective effects that promote axon and myelin survival. E2 effects on EAE were mediated through Esr1 (alpha receptor for E2) but not Esr2 (beta receptor for E2), as were its antiinflammatory and neuroprotective effects. A novel finding is that E2 up-regulated the expression of Foxp3 and CTLA-4 that contribute to the activity of CD4+CD25+ Treg cells. The protective effects of E2 in EAE suggest its use as therapy for MS, although the risk of cardiovascular disease may complicate treatment in postmenopausal women. This risk could be minimized by using subpregnancy levels of exogenous E2 that produced synergistic effects when used in combination another immunoregulatory therapy. Alternatively, one might envision using EE or fluasterone metabolites alone or in combination therapies in both male and female MS patients.

Immunization with myelin or recombinant Nogo-66/MAG in alum promotes axon regeneration and sprouting after corticospinal tract lesions in the spinal cord

We have shown previously that immunization with myelin in incomplete Freund's adjuvant (IFA) is able to promote robust regeneration of corticospinal tract fibers in adult mice. In the present study the effectiveness of such immunization with myelin was compared to that of a combination of two axon growth inhibitors in myelin, Nogo-66 (the 66-amino-acid inhibitory region of Nogo-A) and myelin-associated glycoprotein (MAG). The effectiveness of two adjuvants, IFA and aluminum hydroxide (Alum), was also compared, the latter being one that can be used in humans. In addition, larger dorsal overhemisections were made at the lower thoracic level, which resulted in a larger scar. These studies were carried out in SJL/J mice, a mouse strain that is susceptible to autoimmune experimental allergic encephalomyelitis (EAE). None of the immunized mice developed EAE. Long-distance axon regeneration and sprouting of the corticospinal tract was seen in myelin and Nogo-66/MAG immunized mice. Alum was as effective or better than IFA as the adjuvant. Overall, the robustness of axon growth and sprouting was greater in mice immunized with myelin. The abundance of this growth was less than in our earlier work in which smaller lesions were made, pointing to the possible influence of inhibitors in the scar. This work shows, however, that axon growth inhibitors in myelin can be selectively blocked using this immunization approach to promote long-distance axon regeneration in the spinal cord.

Experimental autoimmune encephalomyelitis (EAE) in CCR2(-/-) mice: susceptibility in multiple strains

Chemokines are low molecular weight cytokines which act as chemoattractants for infiltrating cells bearing appropriate receptors (CCR) to sites of inflammation. It has been proposed that CCR2 on monocytes is responsible for their recruitment into the central nervous system (CNS) in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, and two previous reports have described resistance of CCR2(-/-) mice to EAE. The present study examined three different mouse strains with CCR2 deletions for susceptibility to EAE. Animals were studied up to 4 months post-sensitization and were examined by neuropathology, RNase protection assay, in situ hybridization, and in vitro assays. All three strains were found to be susceptible to EAE: C57BL/6 x J129 and Balb c strains, 100%; and C57BL/6, 67%. Unusual in CNS lesions of CCR2(-/-) mice was an overabundance of neutrophils versus monocytes in wild-type animals. An attempt of the immune system to develop compensatory mechanisms for the lack of CCR2 was evidenced by a corresponding increase in mRNA for other chemokines and CCR. Inasmuch as neutrophils replaced monocytes and led to demyelination, our findings support the concept that promiscuity of chemokines and CCR was able to surmount the deletion of CCR2, still resulting in full expression of this autoimmune disease.

Identification of the encephalitogenic epitopes of CNS proteolipid protein in BALB/c mice

It was previously shown that BALB/c mice were susceptible to experimental autoimmune encephalomyelitis induced by immunization with proteolipid protein (PLP). To determine the encephalitogenic epitopes of PLP in BALB/c mice, mice were immunized with successively smaller pools of 20-mer peptides spanning the PLP molecule from amino acid 30 to amino acid 206. Immunization with PLP(180-199) resulted in clinical EAE in 9/15 mice (mean max clinical score of 3.3), and immunization with PLP(185-206) induced clinical EAE in 7/21 BALB/c mice (mean maximum score of 3.7). No relapses in disease were observed. No EAE was observed in BALB/c mice immunized with PLP(185-199) (n=15), PLP(178-191) (n=13) or other regions of PLP (n=15). Passive transfer of PLP(180-199)-primed lymph node cells into nai;ve BALB/c mice resulted in EAE (2/2 mice, max score of 4.0). One-micron toluidine blue stained sections from the spinal cord of EAE-affected BALB/c mice revealed features typical of EAE in other strains, including mononuclear cell infiltration, myelin loss, and axonal loss.

Microglial-macrophage synthesis of tumor necrosis factor after focal cerebral ischemia in mice is strain dependent

Commonly used inbred mouse strains display substantial differences in sensitivity to focal cerebral ischemia. Such differences can often be ascribed to differences in vascular anatomy. The authors investigated whether a contributing factor could be strain-related differences in cellular synthesis of the pleiotropic and potential neurotoxic cytokine tumor necrosis factor (TNF) in the border zone of and within the focal cerebral infarct. In all mouse strains investigated they found that TNF was synthesized by infarct and periinfarct infiltrating Mac-1 immunopositive microglia-macrophages. BALB/c mice, which developed the largest infarcts, contained significantly fewer TNF-producing microglia-macrophages compared with SJL and C57BL/6 mice at both 12 and 24 hours after permanent occlusion of the distal part of the middle cerebral artery. SJL mice developed larger infarcts than C57BL/6 mice, whereas the number of TNF-producing microglia-macrophages per infarct volume unit was comparable. Western blotting data confirmed the increased TNF levels in SJL mice compared with BALB/c and C57BL/6 mice. Furthermore, mice with 12-hour postischemic survival consistently contained two-to threefold more TNF-producing microglia-macrophages than mice with 24-hour survival. The data show that the magnitude of the cellular TNF response to cerebral ischemia is strain dependent, while the time-profile and the cellular sources of TNF are similar irrespective of genetic background. Furthermore, the lack of correlation between infarct size and cellular TNF response suggests that the functionally important TNF is produced in the very early phase (minutes to a few hours) after induction of ischemia, just as it raises the possibility that different mouse strains display different sensitivities to TNF.

The Wistar Kyoto (RT1(l)) rat is resistant to myelin basic protein-induced experimental autoimmune encephalomyelitis: comparison with the susceptible Lewis (RT1(l)) strain with regard to the MBP-directed CD4+ T cell repertoire and its regulation

Here, we demonstrate that the Wistar Kyoto (WKY/NHsd) rat, which bears the same RT1(l) haplotype as the experimental autoimmune encephalomyelitis (EAE)-susceptible Lewis rat strain, is highly resistant to myelin basic protein (MBP)-induced EAE. No differences between Lewis and WKY strains were found in T cell proliferative specificity or the use of Vbeta8.2 T cell receptors in response to MBP. A Th2 cytokine bias correlated with WKY's EAE resistance. MBP challenge of WKY-into-Lewis adoptive transfer recipients produced a novel biepisodic EAE. The WKY strain should be useful in studies of many tissue-specific autoimmune diseases to which the Lewis rat is susceptible.

Testicular-associated immune deviation: flushing of the testicular lymph sinusoids induces immunosuppression and inhibits formation of EAE in SJL mice

Injection of antigen into the testis has been previously proved to induce systemic tolerance in rats. Testicular-associated immune deviation (TAID) has thus far been induced and studied only in the rat and the present study was planned to study if TAID could be induced in mice as well. In addition, it was studied if TAID is organ-specific. Mouse spinal cord homogenate (MSCH), as well as phosphate-buffered saline (PBS), was injected into the testes of SJL and BALB/c male mice before the induction of experimental allergic encephalomyelitis into the animals. The control animals received MSCH intramuscularly into the hamstring muscles. The animals were followed and graded daily for symptoms attending the next 30 days. In the SJL strain, mice treated with an intratesticular (i.t.) MSCH injection prior to the induction of experimental autoimmune encephalomyelitis (EAE) had the shortest duration of symptoms and the longest time to the onset of the first symptoms. In addition, the mice injected i.t. with PBS had as mild symptoms as those injected with MSCH. There was a statistically significant difference, however, between the groups injected either with MSCH or PBS intratesticularly. In general, mice treated with an intramuscular injection of MSCH got sick first, and had the most severe symptoms for the longest duration of time. In the case of the BALB/c mice, there were no statistical differences between the groups investigated. It is concluded that TAID is a testis- and strain-specific phenomenon in the mouse, and not specific to the rat. In addition, i.t. injection of PBS is just as effective in creating tolerance against EAE as i.t. injection of MSCH in the SJL mice.

Modulation of susceptibility and resistance to an autoimmune model of multiple sclerosis in prototypically susceptible and resistant strains by neutralization of interleukin-12 and interleukin-4, respectively

Experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, is mediated by Th1 cells. The major Th1 inducer, IL-12, enhances EAE, while its blockade suppresses it. IL-4 suppresses EAE. Here, we determined IFN-gamma and IL-4 production by myelin basic protein-stimulated lymphocytes from prototypically EAE-susceptible SJL/J and EAE-resistant BALB/c mice, 9 days after immunization with spinal cord homogenate. While lymphocytes from SJL/J mice produce IFN-gamma and no IL-4, lymphocytes from BALB/c mice produce IL-4 and no IFN-gamma. Since early endogenous production of IL-12/IFN-gamma or IL-4 is linked to Th1 or Th2 responses, respectively, we determined whether neutralization of IL-12 or IL-4 at immunization modifies susceptibility or resistance to EAE. SJL/J mice given neutralizing anti-IL-12 mAb are protected from EAE. BALB/c mice given neutralizing anti-IL-4 mAb develop EAE, while those treated with control antibody remain resistant. These studies confirm the pivotal role of IL-12 in EAE development and show that endogenous IL-4 is important for determining the genetic resistance to EAE.

Bone marrow-derived dendritic cells pulsed with tumor homogenate induce immunity against syngeneic intracerebral glioma

To evaluate the efficacy and toxicity of dendritic cell (DC) based therapy for intracerebral gliomas, we utilized a cell line derived from an astrocytoma that arose spontaneously in a VM/Dk mouse. This astrocytoma mirrors human gliomas phenotypically, morphologically and secretes transforming growth factor (TGF)-betas, immunosuppressive cytokines secreted by human gliomas. Systemic vaccination of mice with DCs pulsed with tumor homogenate followed by intracranial tumor challenge produced a > 160% increase in median survival (p = 0.016) compared with mice vaccinated with PBS or unpulsed DCs (p = 0.083). Fifty percent of mice treated with pulsed DCs survived long-term. Immunologic memory was demonstrated by survival of mice rechallenged with tumor. Both cell-mediated and humoral immunity was induced. On histological examination only focal areas of demyelination at the tumor implantation site were present. There was no evidence that autoimmune encephalomyelitis was induced by DC vaccination. Therefore, in a murine model, vaccination with DCs pulsed with glioma tumor homogenate is a safe and effective therapy against a syngeneic glioma located in the immunologically privileged central nervous system (CNS).

A novel and efficient regimen for producing chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) in SJL mice

We report that SJL mice developed chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) when injected with a mixture of mouse spinal cord homogenate (MSCH), killed mycobacteria tuberculosis (M. tb), and mycobacteria butyricum (M. b) in PBS 2 months before a conventional acute experimental autoimmune encephalomyelitis (EAE) induction injection. The altered progression of the disease involved an accelerated but less severe acute attack and development of a chronic course with relapsing-remitting episodes. Histological examination revealed inflammatory cell infiltration and demyelination in the brain. The dose of neuroantigen as well as the anatomical sites of injections were found to be crucial for the development of the disease.

Genetic Analysis of Disease Subtypes and Sexual Dimorphisms in Mouse Experimental Allergic Encephalomyelitis (EAE): Relapsing/Remitting and Monophasic Remitting/Nonrelapsing EAE Are Immunogenetically Distinct

Experimental allergic encephalomyelitis (EAE) is the principal animal model of multiple sclerosis (MS), the major inflammatory disease of the central nervous system. Murine EAE is generally either an acute monophasic or relapsing disease. Because the clinical spectrum of MS is more diverse, the limited range of disease subtypes observed in EAE has raised concern regarding its relevance as a model for MS. During the generation of a large F2 mapping population between the EAE-susceptible SJL/J and EAE-resistant B10.S/DvTe inbred lines, we identified four distinct subtypes of murine EAE resembling clinical subtypes seen in MS. We observed acute progressive, chronic/nonremitting, remitting/relapsing, and monophasic remitting/nonrelapsing EAE. An additional subtype, benign EAE, was identified after histologic examination revealed that some mice had inflammatory infiltrates of the central nervous system, but did not show clinical signs of EAE. Genome exclusion mapping was performed to identify the loci controlling susceptibility to each disease subtype. We report three novel EAE-modifying loci on chromosomes 16, 7, and 13 (eae11–13, respectively). Additionally, unique loci with gender-specific effects govern susceptibility to remitting/relapsing (eae12) and monophasic remitting/nonrelapsing (eae7 and 13) EAE.

The Inflammatory Response to Nonfatal Sindbis Virus Infection of the Nervous System Is More Severe in SJL Than in BALB/c Mice and Is Associated with Low Levels of IL-4 mRNA and High Levels of IL-10-Producing CD4+ T Cells

SJL mice are susceptible to inflammatory autoimmune diseases of the central nervous system (CNS), while BALB/c mice are relatively resistant. To understand differences in immune responses that may contribute to autoimmune neurologic disease, we compared the responses of SJL and BALB/c mice to infection with Sindbis virus, a virus that causes acute nonfatal encephalomyelitis in both strains of mice. Clearance of virus was similar, but SJL mice developed a more intense inflammatory response in the brain and spinal cord and inflammation persisted for several weeks. Analysis of lymphocytes isolated from brains early after infection showed an absence of NK cells in SJL mice, while both strains of mice showed CD4+ and CD8+ T cells. During the second week after infection, CD4+ T cells increased in SJL mice and the proportion of CD8+ T cells decreased, while the opposite pattern was seen in BALB/c mice. Expression of IL-10 mRNA was higher and IL-4 mRNA was lower in the brains of infected SJL than in BALB/c mice, while expression of the mRNAs of IL-6, IL-1β, TNFα, and the Th1 cytokines IL-2, IL-12, and IFN-γ was similar. Lymphocytes isolated from the CNS of SJL mice produced large amounts of IL-10. CNS lymphocytes from both strains of mice produced IFN-γ in response to stimulation with Sindbis virus, but not in response to myelin basic protein. These data suggest that IL-10-producing CD4+ T cells are differentially recruited to or regulated within the CNS of SJL mice compared with BALB/c mice infected with Sindbis virus, a characteristic that may be related to low levels of IL-4, and is likely to be involved in susceptibility of SJL mice to CNS inflammatory diseases.

Induction of a multiple sclerosis-like disease in mice with an immunodominant epitope of myelin oligodendrocyte glycoprotein

Myelin oligodendrocyte glycoprotein (MOG) is postulated to be a target autoantigen in multiple sclerosis (MS). Here we investigated the encephalitogenicity of an immunodominant epitope of MOG, peptide 35-55, in various strains of mice. An MS-like disease was induced in NOD/Lt mice (H-2g7) and C57BL/6 mice (H-2b) by a single injection of MOG35-55 in CFA. The disease followed a relapsing-remitting course in NOD/Lt mice, whereas C57BL/6 mice developed a chronic paralytic disease. Histologically, the disease in both strains was characterized by cellular infiltration and multifocal demyelination in the CNS. Significant DTH type reactions to MOG35-55 were only seen in MOG-susceptible animals, with the NOD/Lt mice showing the strongest responses. Susceptible mice also showed specific antibody responses to MOG35-55 but not to a panel of other MOG peptides. These results provide further evidence for the role of MOG as a highly autoantigenic molecule capable of inducing severe demyelinating disease.

New Genetic Loci That Control Susceptibility and Symptoms of Experimental Allergic Encephalomyelitis in Inbred Mice

Experimental allergic encephalomyelitis (EAE), the principal animal model of multiple sclerosis, is a genetically determined phenotype. In this study, analyses of the cumulative disease frequencies in parental, F1 hybrid, and F2 mice, derived from the EAE-susceptible SJL/J strain and the EAE-resistant B10.S/DvTe strain, confirmed that susceptibility to EAE is not inherited as a simple Mendelian trait. Whole genome scanning, using 150 informative microsatellite markers and a panel of 291 affected and 390 unaffected F2 progeny, revealed significant linkage of EAE susceptibility to marker loci on chromosomes 7 (eae4) and 17, distal to H2 (eae5). Quantitative trait loci for EAE severity, duration, and onset were identified on chromosomes 11 (eae6, and eae7), 2 (eae8), 9 (eae9), and 3 (eae10). While each locus reported in this study is important in susceptibility or disease course, interactions between marker loci were not statistically significant in models of genetic control. One locus, eae7, colocalizes to the same region of chromosome 11 as Orch3 and Idd4, susceptibility loci in autoimmune orchitis and insulin-dependent diabetes mellitus, respectively. Importantly, eae5 and eae7 are syntenic with human chromosomes 6p21 and 17q22, respectively, two regions of potential significance recently identified in human multiple sclerosis genome scans.

T-cell responses to myelin basic protein in normal and MBP-deficient mice

BALB/c mice are resistant to the development of experimental autoimmune encephalomyelitis (EAE) after immunization with myelin basic protein (MBP). Previous studies of BALB/c mice suggest that MBP-specific T-cells can eventually be cloned from these mice, although they are either initially present in very low frequencies or are functionally anergic. To determine what role endogenous MBP expression plays in shaping the BALB/c T-cell repertoire, MBP-deficient BALB/c mice were constructed by breeding the shiverer (shi/shi) mutation onto the BALB/c background. These mice lack all conventional isoforms of MBP due to a deletion of MBP exons 3-7. Studies of the MBP-directed response of these mice suggest that endogenous MBP expression is directly responsible for EAE resistance in BALB/c mice, by quantitatively affecting expression of the T-cell repertoire. In contrast to wild-type BALB/c T-cells, uncloned T-cells from BALB/c shi/shi mice immunized with MBP proliferate in vitro to MBP and MBP peptides 59-76 and 89-101 and are able to induce severe EAE upon transfer to BALB/c recipients expressing MBP.

Gonadal hormones influence the immune response to PLP 139-151 and the clinical course of relapsing experimental autoimmune encephalomyelitis

Females have an increased incidence of multiple sclerosis (2:1). This gender dimorphism can be studied effectively using a murine model of relapsing experimental autoimmune encephalomyelitis (R-EAE). We demonstrated previously that male SJL mice immunized with proteolipid protein (PLP) peptide 139-151 developed an initial episode of paralysis, but failed to relapse. In the present study, clinical EAE relapses were induced by orchidectomy. Relapses in castrated mice were accompanied by an influx of activated CD4+, Th1 cells into the CNS which were absent in sham mice. Our data suggests an important regulatory role for androgens on the immune response to PLP 139-151 and the clinical course of R-EAE.

Pathogenesis of neuroimmunologic diseases. Experimental models

Animal models of autoimmune diseases have greatly improved our current understanding of the pathogenesis of human autoimmunity and have provided the potential for therapies based on manipulation of the immune system. In our laboratory, we have investigated the immunopathogenesis of autoimmune diseases of the nervous system and muscle. We have developed immune-based approaches for the suppression of experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS), and experimental autoimmune neuritis (EAN), a model for the Guillain-Barré syndrome (GBS). These approaches included induction of peripheral tolerance, immunotoxin targeting of activated T cells, and cytokine manipulations. In addition, we identified the antigen and characterized immunopathologically an autoimmune inflammatory disease of skeletal muscle, experimental autoimmune myositis (EAM), a model for the human inflammatory muscle disease polymyositis.

Insights into the aetiology and pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system, and the most common neurological disease affecting young adults. Multiple sclerosis is a clinically heterogeneous disorder. It is believed to be an autoimmune disease, with cell-mediated and humoral responses directed against myelin proteins. This hypothesis largely comes from pathological parallels with an animal model, experimental autoimmune encephalomyelitis (EAE). Autoimmunity to myelin proteins in humans may be inadvertently triggered by microbes which have structural homologies with myelin antigens (molecular mimicry). As with other autoimmune diseases, susceptibility to MS is associated with certain MHC genes/haplotypes. Full genomic screening of mutiplex families has underscored the role for MHC genes as exerting moderate but the most significant effects in susceptibility. The primary target autoantigen in MS has yet to be definitively identified, but as well as the major myelin proteins, it is now clear that minor myelin components, such as myelin oligodendrocyte glycoprotein (MOG) may play a primary role in disease initiation. This review examines the current knowledge about the aetiology and pathogenesis of MS, and the important similarities with EAE. A better understanding of the molecular mechanisms of autoimmune pathology will provide the basis for more rational immunotherapies to treat MS.

Relapsing and remitting experimental allergic encephalomyelitis: a focused response to the encephalitogenic peptide rather than epitope spread

The progression of experimental allergic encephalomyelitis (EAE) in certain mouse strains has been reported to involve a broadening of the response to myelin antigens, apparently resulting from priming to endogenous determinants of the myelin sheath. The phenomenon has been termed determinant spread. Interest in this effect has centered on the mechanism it offers to explain the progressive, relapsing and remitting course of EAE and indeed of multiple sclerosis. We have conducted a systematic, longitudinal study in SJL mice to look for determinant spread during relapsing and remitting EAE, correlating epitope recognition and cytokine production with disease severity. Disease was induced using three of the four encephalitogenic proteolipid protein or myelin basic protein epitopes, and responses to each of four epitopes recognized by SJL T cells were tracked through acute disease, remission and relapse. The responses of lymph node cells, splenocytes and central nervous system (CNS)-infiltrating T cells were analyzed. While marginal, transient responses to secondary epitopes were detectable in splenocytes, CNS-infiltrating cells showed a dominant response to the original disease-inducing epitope without evidence of a shift to other determinants during relapse. Disease relapse was correlated with an increase in CNS-infiltrating cells and a high proliferative and interferon (IFN)-gamma response to the disease-inducing peptide. During remission, there was a decrease in numbers of cells infiltrating the CNS. These cells were down-regulated, showing low if any response to the myelin peptides tested as measured by proliferation, production of IFN-gamma or production of IL-4. Our findings argue strongly against a causal role for determinant spread in disease relapse as observed in these models of EAE.

Immunodominance of a low-affinity major histocompatibility complex-binding myelin basic protein epitope (residues 111-129) in HLA-DR4 (B1*0401) subjects is associated with a restricted T cell receptor repertoire

The pathogenesis of multiple sclerosis (MS) is currently ascribed in part to a T cell-mediated process targeting myelin components. The T cell response to one candidate autoantigen, myelin basic protein (MBP), in the context of HLA-DR15Dw2, has been previously studied in detail. However, the characteristics of cellular immunity in the context of other MS-associated HLA-DR haplotypes are scarcely known. MBP-specific T cell lines (TCL) were generated from HLA-DR4 (B1*0401)-positive MS subjects. Out of 275 MBP-specific TCL, 178 (64. 7%) specifically recognized region MBP(111-129), predominantly in the context of DRB1*0401. The major T cell epitope for MBP recognition corresponded to residues MBP(116-123). These TCL expressed disparate profiles of cytokine secretion and cytotoxicity. T cell receptor analysis, on the other hand, revealed a strikingly limited heterogeneity of rearrangements. In contrast to MBP(81-99), which binds with high affinity to HLA-DR15 and is recognized by a diverse T cell repertoire, MBP(111-129) binds weakly to DRB1*0401, suggesting that only high affinity T cell receptors might be able to efficiently engage such unstable MHC/peptide complexes, thus accounting for the T cell receptor restriction we observed. This study provides new insight about MBP recognition and proposes an alternative mechanism for immunodominance of self-antigen T cell epitopes in humans.

Polygenic control of experimental allergic encephalomyelitis in Biozzi ABH and BALB/c mice

Experimental allergic encephalomyelitis (EAE) is a chronic inflammatory disease of the central nervous system (CNS), with many similarities to multiple sclerosis (MS). Susceptibility to EAE is under genetic control of both the major histocompatibility complex (MHC) and unknown non-MHC gene products. This study uses a selective cross between EAE-susceptible ABH and low responder BALB/c mice, where disease is dominant and affects female mice significantly more than males. In a genome screen using microsatellite markers, linkage analysis suggests that genes encoded on chromosomes 4, 8, 10, 11, 12 and 17 contribute to the development of EAE (p < 0.05), although none of these putative EAE loci fulfilled the criteria for significant linkage. Interestingly, genotype frequency showed significant deviation from the expected random distribution of alleles on chromosomes 4, 8 and 17, (p < 0.001), with 32% of mice developing disease, exhibiting all 3 alleles (p < 0.001). This may indicate complex interactions amongst gene products in the EAE phenotype. This and other recent studies in different mouse strains underlies that EAE is a complex polygenic trait and may provide clues to the genetic mechanisms involved in autoimmune diseases such as multiple sclerosis.

Characteristics of initial and reinduced experimental autoimmune encephalomyelitis

The factors which influence expression of autoimmune disease in the central nervous system are still poorly understood. We determined the characteristics of experimental autoimmune encephalomyelitis (EAE) in twelve different inbred strains of mice using either mouse spinal cord homogenate or synthetic peptides as the encephalitogen. We also determined whether these strains were susceptible to reinduction of EAE at six weeks after the initial injection. The incidence, time of onset, severity, duration, and number of spontaneous relapses varied widely among the different strains. Duration of initial EAE correlated significantly with incidence of spontaneous relapses, and was greatest in C57L mice and in mice with a C57BL/10 background. Most strains of mice recovered from initial EAE, but recovery was unusual in A.SW and PERA mice. Incidence of reinduced EAE differed from incidence of initial EAE in some strains and did not correlate with incidence of spontaneous relapse. We conclude that the same factors control disease duration and incidence of spontaneous relapse, and that these factors are independent of the factors which control initial incidence. The factors controlling incidence of reinduced EAE are distinct from those controlling spontaneous relapse, and may also differ from those controlling initial incidence. Further investigation of the mechanisms effecting recovery from EAE and the genetic background underlying those mechanisms may help us understand human diseases such as multiple sclerosis.