Suppression of chronic allergic encephalomyelitis: relevance to multiple sclerosis

Evolving understanding of autoimmune mechanisms and new therapeutic strategies of autoimmune disorders

Autoimmune disorders are characterized by aberrant T cell and B cell reactivity to the body's own components, resulting in tissue destruction and organ dysfunction. Autoimmune diseases affect a wide range of people in many parts of the world and have become one of the major concerns in public health. In recent years, there have been substantial progress in our understanding of the epidemiology, risk factors, pathogenesis and mechanisms of autoimmune diseases. Current approved therapeutic interventions for autoimmune diseases are mainly non-specific immunomodulators and may cause broad immunosuppression that leads to serious adverse effects. To overcome the limitations of immunosuppressive drugs in treating autoimmune diseases, precise and target-specific strategies are urgently needed. To date, significant advances have been made in our understanding of the mechanisms of immune tolerance, offering a new avenue for developing antigen-specific immunotherapies for autoimmune diseases. These antigen-specific approaches have shown great potential in various preclinical animal models and recently been evaluated in clinical trials. This review describes the common epidemiology, clinical manifestation and mechanisms of autoimmune diseases, with a focus on typical autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, and sjögren's syndrome. We discuss the current therapeutics developed in this field, highlight the recent advances in the use of nanomaterials and mRNA vaccine techniques to induce antigen-specific immune tolerance.

The role of costimulation in autoimmune demyelination

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated, autoimmune disorder characterized by central nervous system (CNS) inflammation and demyelination, features reminiscent of the human disease, multiple sclerosis (MS). In addition to the signal the encephalitogenic T cell receives through the T cell receptor (TCR), a second signal, termed costimulation, is required for complete T cell activation. The B7 family of cell surface molecules expressed on antigen presenting cells (APC) is capable of providing this second signal to T cells via two receptors, CD28 and CTLA-4. Our studies have shown that costimulation provided by B7 molecules to its ligand CD28 is important in the initiation of the autoimmune response in EAE. Further, it appears the costimulation provided by B7-1 is important in disease development, while B7-2 may play an important regulatory role. We and others later showed that B7/CTLA-4 interaction plays a critical role in down-regulating the immune response. Previous work has shown that activated T cells and T cells of a memory phenotype are less dependent on costimulation than naive T cells. T cells reactive with myelin components that are involved in the pathogenesis of EAE and possibly MS would be expected to have been activated as part of the disease process. Building upon our prior work in the EAE model, we have tested the hypothesis that myelin-reactive T cells, which are relevant to the pathogenesis of CNS inflammatory demyelination, can be distinguished from naive myelin-reactive T cells by a lack of dependence upon costimulation for activation and that the costimulatory requirements of these myelin-reactive T cells change during the course of disease. Our studies in the EAE model have also addressed the mechanisms of extrathymic (peripheral) T cell tolerance following intravenous (i.v. ) administration of high dose antigen. It is believed that TCR signaling in the absence of costimulation is a vital component of peripheral tolerance mechanisms. However, recent evidence suggests that peripheral tolerance of antigen-specific T cells induced in vivo may require CTLA-4 engagement of the tolerized T cells. We have begun to examine the molecular mechanisms of tolerance induction following intravenous and intraperitoneal administration of myelin antigens in the EAE model and test the hypothesis that tolerance induction is dependent on the B7:CD28/CTLA-4 pathway. The results from our studies will enhance our understanding of the role that myelin-reactive T cells may play in the pathogenesis of MS. We have determined that MBP-reactive T cells in MS patients are less dependent upon CD28 costimulation than in normal controls, suggesting that these T cells were previously primed in vivo. Characterization of these CD28-independent myelin-specific T cells will have broad implications for a variety of immunologically based therapies in diseases such as MS.

Intratracheal administration to the lung enhances therapeutic benefit of an MBP peptide in the treatment of murine experimental autoimmune encephalomyelitis

The treatment of autoimmune diseases by targeted down-regulation of autoantigen-specific cells has been accomplished by the administration of high doses of autoantigen. We performed direct comparisons between injection of myelin basic protein peptide and administration by several nonparenteral routes to determine whether route impacted benefit in the treatment of murine allergic encephalomyelitis, a model for multiple sclerosis. The range of effective peptide doses spanned over 1000-fold, and route of delivery played a major role in determining optimal dose. The oral route of administration was the least effective, requiring at least 50- to 100-fold more antigen than subcutaneous injection, which in turn required at least 10-fold more antigen than delivery of peptide to the lung using an intratracheal instillation. Intratracheal delivery was also considerably more effective than inhalation of peptide, and, unlike inhalation, resulted in obvious penetration of delivered material deep into the lung. The increase in therapeutic efficacy did not appear to result from slower systemic delivery of antigen. Accumulation of peptide on antigen presenting cells in the spleen and in the brain was less efficient using the intratracheal route of administration compared to subcutaneous injection, implicating a special role for the lung microenvironment in the induction of immune nonresponsiveness.

Biologic rhythms in the immune system

In all of its components, the immune system shows regularly recurring, rhythmic variations in numerous frequencies; the circadian (about 24 h) rhythms are the best explored. The circadian variations in immunocompetent cells circulating in the peripheral blood are of a magnitude to require attention in medical diagnostics. Both the humoral arm and the delayed (cellular) arm of the immune system function in a rhythmic manner. The response of the immune system to introduction of an antigen and to challenge of the sensitized organism varies in extent in the circadian frequency range and also in lower frequencies, for example, of about a week (circaseptan) or seasonally (circannual). The medical application of the biologic rhythms of the immune system extends to diagnostic measures, as well as treatment.

Expression of costimulatory molecules B7-1 (CD80), B7-2 (CD86), and interleukin 12 cytokine in multiple sclerosis lesions

Resting autoreactive T cells are present in the circulation of normal individuals without pathologic consequences. In autoimmune animal models, stimulation of these self-reactive T cells in the presence of costimulatory molecules B7-1 results in T cell-mediated autoimmune disease, whereas B7-2 stimulation generates regulatory autoreactive T cells that abrogate disease severity. Thus, reactivation in the brain of myelin-autoreactive T cells by antigen with costimulatory molecules may be a critical event in the pathophysiology of multiple sclerosis (MS), a putative autoimmune disease of central nervous system (CNS) myelin. We investigated the expression of cytokines and costimulatory molecules in a panel of 41 histologically characterized CNS specimens from 15 MS and 10 control cases using semiquantitative reverse transcriptase-polymerase chain reaction and immunocytochemistry. In four cases, vascular CNS infarcts with inflammation were compared with MS plaques from the same brain. We observed increased expression of B7-1 and interleukin (IL) 12p40 in acute MS plaques, particularly from early disease cases but not in inflammatory infarcts. B7-1 staining was localized predominantly to the lymphocytes in perivenular inflammatory cuffs but not the parenchyma. In contrast, B7-2 was expressed predominantly on macrophages both in MS lesions of varied time duration and in inflammatory infarcts. These findings indicate that an early event in the initiation of MS involves upregulation of B7-1 and IL-12, resulting in conditions that maximally stimulate T cell activation and induction of T helper 1-type immune responses.

Experimental strategies to promote central nervous system remyelination in multiple sclerosis: insights gained from the Theiler's virus model system

The destruction of central nervous system (CNS) myelin, the lipid-rich insulator surrounding axons in the mammalian brain and spinal cord, is the primary pathological finding in multiple sclerosis. Myelin loss can result in a significant clinical deficit, and was originally thought to be permanent, similar to axonal destruction. However, myelin regeneration is now an established phenomenon in both human disease and animal models of CNS demyelination. In this review, the concept of remyelination in demyelinating diseases such as multiple sclerosis is discussed and the usefulness of animal models of CNS demyelination in developing experimental strategies to promote remyelination is examined. Special emphasis is given to the Theiler's murine encephalomyelitis model, which has been the primary animal model used to investigate therapies designed specifically to stimulate myelin repair.

T cell deletion in high antigen dose therapy of autoimmune encephalomyelitis

Encounters with antigen can stimulate T cells to become activated and proliferate, become nonresponsive to antigen, or to die. T cell death was shown to be a physiological response to interleukin-2-stimulated cell cycling and T cell receptor reengagement at high antigen doses. This feedback regulatory mechanism attenuates the immune response by deleting a portion of newly dividing, antigen-reactive T cells. This mechanism deleted autoreactive T cells and abrogated the clinical and pathological signs of autoimmune encephalomyelitis in mice after repetitive administration of myelin basic protein.

Suppression of experimental autoimmune encephalomyelitis by oral administration of myelin basic protein. V. Hierarchy of suppression by myelin basic protein from different species

We have been investigating the suppression of experimental autoimmune encephalomyelitis (EAE) by oral tolerization to autoantigens. In the present study the tolerizing effect of orally administered myelin basic protein (MBP) from different species was examined in the Lewis rat, Hartley guinea pig, and SJL/J mouse model of EAE. Animals were fed guinea pig, rat, bovine, human or mouse-MBP and then immunized with the homologous species of MBP or myelin: Lewis rats were immunized with rat MBP, Hartley guinea pigs with guinea pig-MBP, and SJL/J mice with mouse myelin. Clinical expression of EAE and delayed-type hypersensitivity (DTH) responses to MBP were assessed. In each species, suppression of disease and DTH responses were most pronounced by tolerization with the homologous species of MBP. In addition, cross-species tolerization was observed in each species and in general was less suppressive than homologous MBP although in some instances MBP from a heterologous species was as effective as tolerization with the homologous species. We also studied guinea pig-MBP induced EAE in the Lewis rat because it is a widely studied model of EAE and found that oral tolerization with guinea pig MBP was as suppressive as rat MBP. Of note is that oral tolerization with mouse MBP suppressed myelin-induced EAE in the SJL mouse in which autoimmunity to proteolipid protein appears to play a primary role, suggesting that antigen-driven bystander suppression following oral tolerization with autoantigens (Miller et al., 1991b) may be an important contributing mechanism for suppression of EAE following oral tolerization with MBP in this model.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of experimental autoimmune encephalomyelitis by oral administration of myelin antigens: IV. Suppression of chronic relapsing disease in the Lewis rat and strain 13 guinea pig

Oral administration of proteins is a long-recognized method of inducing antigen-specific peripheral immune tolerance. We previously showed that oral administration of myelin basic protein suppresses monophasic experimental autoimmune encephalomyelitis in the Lewis rat when it is given in association with immunization and prior to disease onset. As a potential therapy for human autoimmune disease, it is crucial to determine whether oral tolerance can ameliorate an ongoing immune response. We therefore asked whether oral administration of myelin antigens, after sensitization and disease expression has occurred, could affect immunological, clinical, or pathological features of experimental autoimmune encephalomyelitis. Chronic relapsing experimental autoimmune encephalomyelitis was induced in the Lewis rat and strain 13 guinea pig by immunization with whole guinea pig cord homogenate, complete Freund's adjuvant, and Mycobacterium tuberculosis. Following recovery from the first attack, animals were orally given bovine myelin, guinea pig myelin, or guinea pig myelin basic protein three times per week for up to 3 months. Animals receiving myelin products orally had decreased severity and frequency of clinical relapses, decreased delayed-type hypersensitivity responses to myelin antigens, diminished inflammation in the central nervous system (CNS), and decreased areas of CNS demyelination. In the rat, guinea pig myelin basic protein was as effective as guinea pig myelin in ameliorating the disease and also resulted in decreased serum anti-myelin basic protein antibody levels. No exacerbation of disease or worsening of pathological findings occurred in the animals given myelin products. These results demonstrate that oral administration of myelin antigens can suppress chronic relapsing experimental autoimmune encephalomyelitis and have direct relevance to therapy of human demyelinating disorders such as multiple sclerosis.

The role of the thymus in multiple sclerosis

The presence of numerous changes in T lymphocyte activity found in MS patients points to the involvement of the thymus in multiple sclerosis. The etiophathogenetic mechanism of MS is probably an autoimmune reaction that is triggered by a viral infection caused by one or more viruses and that perpetuates itself, causing the disease to progress. It has been proved that the thymus maintains its immunocompetence even in adulthood and that it has a role in the pathogenesis in several autoimmune diseases. In exacerbations of MS there is a decrease in T suppressor lymphocytes while histological and lymphocyte subset changes have been demonstrated in the thymus of MS patients. The lymphocyte response to mitogens is also depressed in MS. The clinical results of thymectomy in MS are not uniform and are on the whole inconclusive, probably through the lack of criteria of selection of patients for surgical treatment. We consider that the morphological and functional study of the thymus biopsy specimen should supply the appropriate criteria of suitability for surgical treatment.

Sites of egress of inflammatory cells and horseradish peroxidase transport across the blood-brain barrier in a murine model of chronic relapsing experimental allergic encephalomyelitis

Results are reported of experiments designed to focus at attachment sites of inflammatory cells (ICs) on the luminal surface of brain endothelial cells (ECs) and on the mechanisms of horseradish peroxidase (HRP) transport across the altered blood-brain barrier (BBB) in a murine model of chronic relapsing experimental allergic encephalomyelitis. Cationized ferritin (CF) served as a marker for evaluating the electrostatic nature of brain microblood vessels (MBVs) on the plasma membranes of ICs or normal mouse peripheral white blood cells and erythrocytes. SJL/J mice demonstrating clinical illness were given HRP or CF, in vivo or in situ, respectively. Light microscopy and conventional transmission electron microscopy of cerebellum or thoracic and lumbar spinal cord regions demonstrated HRP leakage most pronounced in MBVs with perivascular infiltrates. HRP traversed across the ECs via numerous vesicles and tubular profiles located mostly in the parajunctional regions, while EC junctions appeared closed. Scanning electron microscopy demonstrated that IC attachment was primarily at parajunctional sites on the EC surface. We also observed increased microvillar projections extending from the EC surface into the lumen. CF demonstrated a patchy decoration on both the luminal EC surface and IC membranes but did not label uncoated invaginating membrane pits or tubular structures. Our data indicate that the points of attachment of the ICs on the EC surface may reflect specific receptor sites where the ICs eventually gain entrance into CNS across the BBB during brain inflammation.

Chronic relapsing experimental allergic encephalomyelitis in the Lewis rat: studies on immune regulation

To study immunoregulation of chronic relapsing experimental allergic encephalomyelitis (CR-EAE) in Lewis rats, we adoptively transferred concanavalin A-activated lymph node cells (LNC) or splenocytes, from hind footpad-inoculated donors at the onset (day 11), or recovery (day 16), of the first attack. Popliteal LNC, especially from day 16 donors, provided significant and dose-dependent, but incomplete, protection of recipients from encephalitogenic challenge; maximal mean delay in EAE onset was 10 days later than controls, with subsequent paralysis reduced more than 6-fold. In contrast, particularly from day 11 donors, superficial inguinal LNC recipients developed actively induced disease of normal severity up to 4 days earlier than CR-EAE controls. Furthermore day 11 EAE splenocytes, but not day 16 ones, adoptively transferred disease into 50-88% of naive recipients. In separate studies, we demonstrated unresponsiveness to active induction of disease in all rats re-challenged during stable late remission, as well as in a minority of animals pretreated with antigen in incomplete Freund's adjuvant. These results suggest an organ-dependent and time-dependent balance between effector and suppressor populations in the model.

A review of the etiology of multiple sclerosis

The geographic distribution of multiple sclerosis and the influence of migration on the risk of contracting it point to an environmental factor as cause of the disease. This environmental factor might be a virus which might produce the demyelination process through an autoimmune reaction against components of the central nervous system. The other possible cause of multiple sclerosis is a genetic susceptibility, inferred from the higher risk for the disease found among relatives of patients with multiple sclerosis and on the association between the disease and some histocompatibility antigens of the HLA system. Both theories seem to be correct, with the environmental factors(s) causing multiple sclerosis only in the presence of a genetic susceptibility.

Suppression of chronic-relapsing experimental allergic encephalomyelitis in strain-13 guinea pigs by administration of liposome-associated myelin basic protein

Juvenile strain-13 guinea pigs were challenged with isologous spinal cord in CFA. After recovery from the first EAE episode the animals were treated with guinea pig MBP inserted into liposomes, with cytochrome-c-liposomes, with MBP in saline or with MBP in IFA. Guinea pigs treated with MBP-liposomes showed a striking reduction in clinical signs and in the number and intensity of relapses. They displayed virtually no demyelinating lesions, and had comparatively little parenchymal inflammation in the spinal cord. Early T rosette levels showed an inverse correlation with the severity of histological lesions in the spinal cord but correlation with the clinical status at the time of rosette assay was less well defined.

Delayed type skin response to myelin basic protein in chronic relapsing experimental allergic encephalomyelitis

The skin response to myelin basic protein (MBP) was studied in chronic relapsing experimental allergic encephalomyelitis (EAE) using strain 13 guinea pigs. The delayed type skin response showed a monophasic curve; it gradually increased after immunization, reached maximum levels around 80 days post-immunization, and decreased thereafter. Relapses were more frequent while it was at high levels although it did not correlate directly in individuals with the clinical stage. The skin response was also high in MBP-immunized animals which had recovered from acute EAE. Our results suggest that delayed type hypersensitivity to MBP is involved but is not sufficient by itself to cause relapsing EAE.

Chronobiology in hematology and immunology

The hematopoietic and the immune systems in all their components are characterized by a multifrequency time structure with prominent rhythms in cell proliferation and cell function in the circadian, infradian, and rhythms in cell proliferation and cell function in the circadian, infradian, and circannual frequency ranges. The circulating formed elements in the peripheral blood show highly reproducible circadian rhythms. The timing and the extent of these rhythms were established in a clinically healthy human population and are shown as chronograms, cosinor summaries and, for some high-amplitude rhythms, as time-qualified reference ranges (chronodesms). Not only the number but also the reactivity of circulating blood cells varies predictably as a function of time as shown for the circadian rhythm in responsiveness of human and murine lymphocytes in vitro to lectin mitogens (phytohemagglutinin and pokeweed mitogen). Some circadian rhythms of hematologic functions appear to be innate and are presumably genetically determined but are modulated and adjusted in their timing by environmental factors, so-called synchronizers. Phase alterations in the circadian rhythms of hematologic parameters of human subjects and of mice by manipulation of the activity-rest or light-dark schedule and/or of the time of food uptake are presented. Characteristically these functions do not change their timing immediately after a shift in synchronizer phase but adapt over several and in some instances over many transient cycles. The circadian rhythm of cell proliferation in the mammalian bone marrow and lymphoid system as shown in mice in vivo and in vitro may lend itself to timed treatment with cell-cycle-specific and nonspecific agents in an attempt to maximize the desired and to minimize the undesired treatment effects upon the marrow. Differences in response, and susceptibility of cells and tissues at different stages of their circadian and circaseptan (about 7-day) rhythms and presumably of cyclic variations in other frequencies are expected to lead to the development of a chronopharmacology of the hematopoietic and immune system. Infradian rhythms of several frequencies have been described for numerous hematologic and immune functions. Some of these, i.e., in the circaseptan frequency range, seem to be of importance for humoral and for cell mediated immune functions including allograft rejection. Infradian rhythms with periods of 19 to 22 days seem to occur in some hematologic functions and are very prominent in cyclic neutropenia and (with shorter periods) in its animal model, the grey collie syndrome.(ABSTRACT TRUNCATED AT 400 WORDS)

Chronic relapsing experimental autoimmune encephalomyelitis. treatment with combinations of myelin components promotes clinical and structural recovery

Preliminary results are presented on the treatment of Strain 13 guinea pigs with chronic relapsing experimental autoimmune (allergic) encephalomyelitis (EAE) induced by a single sensitisation with whole spinal cord. Animals were treated at different stages of the disease with injection containing either myelin basic protein (MBP) alone in incomplete Freund's adjuvant (IFA), or MBP in combination with a lipid hapten of myelin, galactocerebroside (GC) in IFA. The rationale for this treatment stemmed from previous work which suggested that MBP was responsible for T cell sensitisation in EAE and that GC was important in producing demyelinating antibodies and that both myelin components were needed in the induction of disease. Although treatment with MBP alone caused some initial stabilisation of the disease process, subsequent relapses occurred in all animals. However, in animals given MBP and GC together, either early or late in the course of the disease, marked clinical improvement has been noted with little or no development of relapses over an observation period of more than one year post-treatment. In addition, evidence of extensive remyelination and oligodendroglial proliferation in CNS lesions has been found in MBP-GC-treated animals suggesting that this therapy might be beneficial for CNS repair and relevant to multiple sclerosis.

Circaseptan (about-7-day) bioperiodicity--spontaneous and reactive--and the search for pacemakers

A built-in (genetically determined) about-7-day (circaseptan) period comes to the fore as a desynchronized feature of human time structure in the urinary excretion of 17-ketosteroids by a clinical healthy man: during several years following an endocrine intervention (the self-administration of testosterone suppositories), a circaseptan rhythm (which during the preceding decade had revealed a period of precisely 7 days) deviated slightly, yet with statistical significance, from the environmental week. A second line of evidence for an intrinsic circaseptan component stems from the demonstration of statistically significant differences in timing of a circaseptan rhythm in springtail oviposition. A third line of evidence documents prominent circaseptan rhythmicity after the application of a single stimulus (devoid in itself of any circaseptan information). Such single stimulus induction, amplification and/or synchronization also documents the clinical and biologic importance of built-in circaseptan rhythms that were previously often misinterpreted as being purely reactive: a circaseptan spectral component is remarkably prominent in mammalian organ transplant rejection, both in the clinic and in the laboratory. In the latter case, in the absence of any weekly cycles in hospital routine, including treatment schedules, circaseptan components characterize the rejection of the rat kidney, pancreas and heart. Much additional information here reviewed reveals the occurrence of periods of about 7 days. Their implications for transplant and other chronoimmunology as well as biology in general, and their clinical applications in drug treatment, include the need to weld circaseptan timing to circadian timing and dosing. A dramatic documentation of this need stems from the circumstance that pretreatment for one week with the same total dose of the same substance (a polysaccharide - Lentinan) accelerates or retards cancerous growth (hence shortens or lengthens survival) as a function of interactive circaseptan and circadian rhythms.

The significance of abnormal immune responses in patients with multiple sclerosis

Early diagnosis of multiple sclerosis (MS) may be assisted by tests for the abnormal immune responses of the central nervous system (CNS) including oligoclonal IgG bands in the cerebrospinal fluid (CSF), increased CNS IgG synthesis, increased CNS antibody synthesis against multiple viruses and increased numbers of enlarged lymphoid cells in the CSF. Alterations in immunological responses are important in the pathogenesis of MS. Further studies are needed, however, to identify the antigen(s) and/or antibodies responsible for oligoclonal IgG in the CSF of MS patients. Also, the cause(s) for the other immunological abnormalities with diagnostic importance need to be identified. The increased synthesis of antibodies against multiple unrelated viruses suggests generalized alteration in the immune regulatory system. The etiology of MS might be multifactorial involving abnormal immunological responses, possibly precipitated by infectious agents acquired during childhood by genetically susceptible individuals. The immunological responses including alterations in myelin basic protein concentration, antimyelin antibody and immune complex activities in CSF, and in vitro stimulation, suppression and migration inhibition of blood lymphocytes appear to correlate with stage of MS and severity of CNS damage. Some of the tests may become useful in estimating the prognosis of the disease. Longitudinal studies are needed to clarify the sensitivity of the diagnostic and prognostic immunological tests and etiological significance of these abnormalities in MS.

Experimental allergic encephalomyelitis. Frequent sampling of blood alters disease course

Previous studies have shown that Strain 13 guinea pigs sensitised for experimental allergic encephalomyelitis (EAE) as adults usually develop an acute, fatal form of disease while animals inoculated as juveniles usually display a chronic relapsing form. The present study reports that following repeated short-interval blood sampling by cardiac puncture for the estimation of lymphocyte populations, some adult Strain 13 guinea pigs sensitised for acute EAE unexpectedly survived and developed chronic EAE, while a group of juveniles sensitised for chronic EAE and bled under the same conditions, developed a more severe, acute form of EAE. It is suggested that this reversal of disease course was related to the depletion of circulating factors.

Recurrent demyelination in chronic central nervous system infection produced by Theiler's murine encephalomyelitis virus

A morphologic study of demyelination produced by Theiler's encephalomyelitis virus (TMEV) infection in C3H/He mice was performed. Demyelination in this strain of mouse was less intense and had a milder gliomesodermal response than that observed in SJL mice. As early as 80 days after infection numerous remyelinated axons were present in C3H/He mice, and later, extensive remyelination was observed and was mainly by Schwann cells. About one-third of remyelinated plaques showed recurrent demyelinating activity at 200 days. The best evidence of recurrent demyelination was the loss of myelin by abons which had been previously remyelinated by Schwann cells. In addition, acute areas of demyelination were also seen in spinal cords which contained chronic or quiescent plaques. The demonstration of recurrent demyelination in TMEV infection is important for it increases the relevance of this model to multiple sclerosis (MS). In addition TMEV infection of C3H/He mice appears to be an excellent model for further studies of Schwann cell remyelination and recurrent demyelination in the central nervous system (CNS).

The effect of Cop 1, a synthetic polypeptide, on chronic relapsing experimental allergic encephalomyelitis in guinea pigs

Cop 1, a synthetic polypeptide, was evaluated for its effect on a chronic relapsing form of experimental allergic encephalomyelitis (EAE). Pretreatment of juvenile Strain 13 guinea pigs with Cop 1 in incomplete Freund's adjuvant (IFA) which were subsequently challenged with guinea pig spinal cord in complete Freund's adjuvant (CFA) had a marked effect in delaying or preventing the appearance of clinical signs of EAE. Administration of Cop 1 on appearance of clinical signs of EAE prevented progression of the first episode of the disease. Although relapses were not always prevented, they were modified on their duration and intensity both clinically and histologically.

Suppression and reversal of allergic encephalomyelitis in rhesus monkeys with basic protein and peptides

We have extended earlier studies on the suppression of clinically evident experimental allergic encephalomyelitis (EAE) in monkeys, repeated injections of human basis protein. The results confirm that after suppressive treatment, recovered animals remain clinically normal and do not show spontaneous recurrence of symptoms. However, recovered animals are susceptible to EAE upon renewed challenge, and they develop the disease more rapidly and more severely than after the initial challenge; resuppression is also accomplished in these cases by the same methods used previously. The results indicate further that the basic protein or peptide T administered without mycobacteria is effective in suppressing the development of basic protein-induced EAE regardless of the species from which it was derived.

Chronic relapsing experimental allergic encephalomyelitis. Correlation of circulating lymphocyte fluctuations with disease activity in suppressed and unsuppressed animals

Groups of juvenile Strain 13 guinea pigs sensitized for chronic relapsing experimental allergic encephalomyelitis (EAE) with isogeneic central nervous system (CNS) tissue in complete Freund's adjuvant (CFA) were either left to develop late-onset chronic EAE (unsuppressed), or given a series of injections of bovine myelin basic protein (MBP) in incomplete Freund's adjuvant (IFA) to suppress the disease. All unsuppressed animals developed disease and all suppressed animals remained healthy over a 27-month period of study. some unsuppressed and suppressed animals were rechallenged with CNS tissue in CFA 12 or 26 months post-inoculation (PI). Unsuppressed animals all became sick 2-4 weeks after rechallenge, while rechallenged, suppressed animals were protected, indicating that the suppression was permanent. Pathologic findings in the CNS complemented the clinical changes. Circulating lymphocyte studies were performed on animals from all groups. Early (active, high-affinity rosetting) T cell levels in unsuppressed animals showed significant decreases during exacerbations (P less than 0.01) and normal values during remissions. After rechallenge, circulating early T cells decreased in unsuppressed animals with the development of signs. In suppressed animals, early T cells showed significant elevations during, and for a short time after, the period of suppressive injections, and normal values afterwards. These levels did not change significantly after rechallenge. Late (total, 24 hour rosetting) T cell and B cell values showed minor fluctuations only which did not correlate with disease activity. These results indicate that chronic relapsing EAE can be successfully suppressed with MBP in IFA, that this suppression is permanent and that the immunologic findings presented correlate well with the clinical and pathologic facets of the disease. the findings are presented in terms of their relevance to multiple sclerosis.