Epitopes of immunoreactive myelin basic protein in human cerebrospinal fluid

Elevated Levels of Proinflammatory Cytokines in Cerebrospinal Fluid of Multiple Sclerosis Patients

Multiple sclerosis (MS) is an autoimmune neurodegenerative disease characterized by chronic brain inflammation. Leukocyte infiltration of brain tissue causes inflammation, demyelination, and the subsequent formation of sclerotic plaques, which are a hallmark of MS. Activation of proinflammatory cytokines is essential for regulation of lymphocyte migration across the blood–brain barrier. We demonstrate increased levels of many cytokines, including IL-2RA, CCL5, CCL11, MIF, CXCL1, CXCL10, IFNγ, SCF, and TRAIL, were upregulated in cerebrospinal fluid (CSF), whereas IL-17, CCL2, CCL3, CCL4, and IL-12(p40) were activated in MS serum. Interaction analysis of cytokines in CSF demonstrated a connection between IFNγ and CCL5 as well as MIF. Many cells can contribute to production of these cytokines including CD8 and Th1 lymphocytes and astrocytes. Therefore, we suggest that IFNγ released by Th1 lymphocytes can activate astrocytes, which then produce chemoattractants, including CCL5 and MIF. These chemokines promote an inflammatory milieu and interact with multiple chemokines including CCL27 and CXCL1. Of special note, upregulation of CCL27 was found in CSF of MS cases. This observation is the first to demonstrate CCL27 as a potential contributor of brain pathology in MS. Our data suggest that CCL27 may be involved in activation and migration of autoreactive encephalitogenic immune effectors in the brain. Further, our data support the role of Th1 lymphocytes in the pathogenesis of brain inflammation in MS, with several cytokines playing a central role.

Cerebrospinal fluid in multiple sclerosis

Background:

Technological advances have made it possible to examine the human cerebrospinal fluid (CSF) in a manner that was previously impossible. CSF provides a window into the changes that occur in the central nervous system (CNS) in health and disease. Through analysis of the CSF, we discern indirectly the state of health of the CNS, and correctly or incorrectly, draw conclusions regarding mechanisms of CNS injury and repair.

Objective, Materials and Methods:

To review the current state of knowledge of changes in the CSF in multiple sclerosis.

Discussion:

Establishing CSF markers that permit evaluation of the various biological processes in multiple sclerosis remains a challenge. Of all the biological processes, inflammatory markers are probably the best identified. Detection of oligoclonal immunoglobulin bands in the CSF is now established as the single most useful laboratory marker in the CSF to aid in the diagnosis of multiple sclerosis. Markers of demyelination, remyelination, neuro-axonal loss, neural repair and regeneration, and astrogliosis are only now being recognized. A good surrogate for any of these pathophysiological processes has not been defined to date.

Conclusion:

The goal of future research is not only to define surrogate markers in the CSF for each of the above functions, but also to extend it to other more readily accessible body fluids like blood and urine. A synopsis of the current literature in most of these areas of CSF evaluation pertaining to multiple sclerosis is presented in this article.

Myelin basic protein (MBP) and MBP peptides are mitogens for cultured astrocytes

After CNS demyelination, astrogliosis interferes with axonal regeneration and remyelination. We now provide evidence that myelin basic protein (MBP) can contribute to this observed astrocyte proliferation. We found that astrocytes grown in either serum-containing or serum-free medium proliferate in response to MBP. The mitogenic regions of MBP in both media were MBP(1-44), MBP(88-151) and MBP(152-167). The mitogenic effect of these individual peptides was potentiated by simultaneous treatment with microglia conditioned media (CM). MBP-induced proliferation was inhibited by suramin at concentrations known to block the fibroblast growth factor receptor (FGFR), whereas neither MBP(1-44), MBP(88-151) nor MBP(152-167) were affected. Cholera toxin B, that binds to ganglioside GM(1), inhibited the mitogenicity of MBP(1-44) and had no significant effect on the mitogenicity of MBP, MBP(88-151) or MBP(152-167). Treatment of astrocytes with MBP and MBP(152-167) caused a modest and transitory elevation of intracellular calcium, whereas treatment with MBP(1-44) resulted in a substantial and sustained increase in intracellular calcium. These results suggest that for cultured astrocytes 1) FGFR and extracellular calcium play a major role in MBP mitogenicity; 2) MBP(1-44), MBP(88-151) and MBP(152-167) are the mitogenic regions of MBP; 3) MBP(1-44) and MBP(152-167) interact with ganglioside GM(1) and FGFR, respectively; 4) Component(s) present in microglial CM potentiate the mitogenicity of MBP(1-44), MBP(88-151) and MBP(152-167). These data support the hypothesis that MBP related peptides in conjunction with microglial secreted factors may stimulate astrogliosis after demyelination in vivo.

Peptides from bovine brain: structure and biological role

Fractionation of bovine brain extracts followed by automatic Edman sequencing of individual components resulted in identification of 107 endogenous peptides formed from functional proteins (haemoglobin, myelin basic protein, cytochrome c oxidase, etc) or unknown precursors. Several of the newly identified brain peptides demonstrate different types of biological activity; some of the substances show considerable overlap with the known biologically active peptides. It is suggested that these peptides should participate in regulation of extracellular and intracellular biochemical processes. A concept of 'tissue-specific peptide pool' is formulated describing a novel system of peptidergic regulation, complementary to the conventional hormonal and neuromodulatory systems. According to that description functional proteins provide their proteolytically derived fragments for maintaining the tissue homeostasis by modulating the availability of peptide receptors to respective 'true' ligands.

Myelin basic protein in cerebrospinal fluid and other body fluids

Myelin basic protein (MBP) or a fragment thereof may enter cerebrospinal fluid (CSF) and other body fluids in an etiologically nonspecific fashion to provide information about the status of central nervous system (CNS) myelin damage. MBP immunochemically detected is referred to as MBP-like material (MBPLM). The clinical utility of the assay for MBPLM in CSF is to document the presence, continuation, or resolution of CNS myelin injury. The analysis of CSF for MBPLM is subject to many variables, among which are the antisera and the form of the assay utilized. The dominant epitope of CSF MBPLM is in the decapeptide of 80-89 from the intact MBP molecule of 170 residues. Normally, CSF has no detected MBPLM. Following an acute relapse of MS, MBPLM rises quickly in the range of ng/ml and rapidly declines and disappears. The presence of MBPLM in CSF in chronic and progressive phases of the disease is unusual, but it may sometimes be detected in low levels, depending on the assay used for detection. The level of CSF MBPLM is related to both the mass of CNS myelin damage and how recently it occurred. The level of CSF MBPLM rarely is elevated in optic neuritis. The level of CSF MBPLM is unrelated to CSF protein level, level of IgG, presence of oligoclonal bands or pleocytosis. CSF MBPLM has the potential of serving as a marker of therapeutic effectiveness in MS and does have predictive value for response to glucocorticoids given for worsening of disease. The detection of MBPLM in body fluids other than CSF would be of great value because of the resulting improved feasibility for objectively monitoring the natural history of MS and response to therapy. Studies on blood have yet to produce a valid assay of MBPLM. Urinary MBPLM, though different in its features from that in CSF, may provide a correlate, not with acute demyelination in MS as is the case for CSF, but with progression of disease.

Enzyme immunoassay for myelin basic protein in cerebrospinal fluid

Myelin basic proteins (MBPs) are a set of proteins making up about 30% of the protein content of the central nervous system myelin. Four human isoforms have been identified. The most abundant is a highly conserved 18.5 kDa polypeptide. For this species, the amino acid sequence homologies between human and monkey or human and chick are 98.2% and 71.1%, respectively. As a consequence, there is a very good immunological cross-reactivity between the mammalian MBP. This protein has been extensively used to induce experimental allergic encephalomyelits (EAE) in numerous animals. The evolution of chronic EAE in animal is similar to that of multiple sclerosis (MS), a demyelinating human pathology, and chronic EAE is considered to be an animal model of MS. In demyelinating pathologies, MBP concentration in the cerebrospinal fluid (CSF) is considered to be a good marker of demyelination. MBP concentration, in biological fluids, is generally determined by radioimmunoassay (RIA). The RIA technique currently used is highly sensitive (0.1-2.5 ng/ml) but has the drawback of requiring the handling of radioactivity and frequent labelling of MBP. So we developed a new enzyme immunoassay (EIA) technique. Our technique has the same sensitivity as RIA, needs only small volumes of CSF (50 microliters) and the enzyme-labelled MBP tracer is stable for at least 12 months.

Cerebrospinal fluid myelin basic protein-like material in acute monosymptomatic optic neuritis

INTRODUCTION

Cerebrospinal fluid (CSF) may provide markers of severity and outcome of optic neuritis.

MATERIAL AND METHODS

We examined the CSF from 29 patients with acute monosymptomatic optic neuritis (AMON) for content of myelin basic protein-like material (MBPLM) and correlated the levels with results of cranial magnetic resonance imaging. The length of the time from onset of AMON to the time of CSF collection did not exceed four weeks.

RESULTS

Only two patients (7%), one of whom developed an acute myelopathy one month after AMON, showed an elevated value of CSF MBPLM. No MBPLM was detected in 6 patients (21%), and other 21 (72%) had detectable levels of MBPLM but below the upper limit of normal of 0.1 ng/ml. The value of MBPLM was not significantly correlated with the interval to CSF sampling from onset of AMON or with severity of decreased visual acuity. The highest values of CSF MBLPM were observed among patients with severely decreased visual acuity and among patients with an abnormal MRI (13 of 27 i.e. 48%).

CONCLUSIONS

CSF MBPLM was rarely abnormal in AMON. However, CSF MBPLM may have potential value in reflecting disease activity, as the highest values were obtained among patients with CSF sampled soon after the maximum visual dysfunction was reached, with severe visual impairment, and with an abnormal MRI.

Correlation of clinical features and findings on cranial magnetic resonance imaging with urinary myelin basic protein-like material in patients with multiple sclerosis

Immunoreactive material that appears to be a peptide encompassing all or a portion of residues 80 to 89 of myelin basic protein is present in normal unconcentrated urine and is increased in certain patients with multiple sclerosis (MS). Compared with normal controls, urines collected randomly from 158 MS patients or in a clinical research unit from 8 patients with MS had higher mean values of urinary MBP-like material (MBPLM). The level of MBPLM in urine showed no direct relationship to MBPLM in cerebrospinal fluid and did not correlate with clinical relapses of disease. In the other neurological disease control group (26 patients), some patients with other inflammatory diseases, but not stroke or early phase Guillain-Barré syndrome, also showed elevations. Among the subtypes of MS, those with secondary chronic progressive disease had the highest values. Urinary MBPLM showed no definite correlation with or effect of treatment with glucocorticoids and immunosuppressants except that a lower level of urinary MBPLM showed a weak relationship with improvement following treatment with methylprednisolone/prednisone. In a serial study of 8 patients with unenhanced cranial magnetic resonance imaging and 20 patients with gadolinium-enhanced cranial magnetic resonance imaging, urinary MBPLM did not show a direct correlation with new or enhancing lesions. Urinary MBPLM does not parallel acute myelin damage but appears to reflect an ongoing process, possibly linked to attempted efforts at remyelination.

Human myelin basic protein (MBP) epitopes recognized by mouse MBP-selected T cell lines from multiple sclerosis patients

We investigated whether myelin basic protein (MBP)-reactive T cells from multiple sclerosis (MS) patients can recognize mouse MBP since this is an expected requirement for the transfer of experimental autoimmune encephalomyelitis (EAE) into severe combined immunodeficiency (SCID) mouse-human chimeras. Peripheral blood mononuclear cells from 11 MS patients were analyzed for in vitro proliferation to mouse MBP. Six patients (55%) responded to mouse MBP at the first or second stimulation. Five T cell lines, selected with mouse MBP from five MS patients, were analyzed for their proliferation to mouse and human MBP and to a panel of synthetic peptides of human MBP. Four of the five lines recognized mouse MBP. In vitro proliferation was restricted by MHC class II in one line tested for MHC restriction. One of the five lines recognized whole human MBP and all five of the lines responded to at least one of the five synthetic peptides corresponding to human MBP residues 8-28, 67-90, 84-102, 87-99 or 130-149. These results show that MS patient T cells recognize mouse MBP and suggest that distinct human MBP epitopes are immunologically cross-reactive with epitopes of mouse MBP.

The structure of a myelin basic protein-associated idiotope

A cross-reactive idiotope (CRI) has been previously described on monoclonal antibodies (mAbs) specific for encephalitogenic peptides from myelin basic protein (MBP). The anti-CRI mAb, F25F7, binds an idiotope (Id) localized to the light chains of an anti-MBP peptide 1-9 mAb, denoted F23C6, and an anti-MBP peptide 80-89 mAb, denoted 845D3. It is the purpose of this study to further delineate the CRI being recognized by F25F7. To this end, we have found a structural correlation between the CRI and the antigen, a small synthetic peptide, denoted PBM 9-1, used to elicit the anti-Id mAb. Sequence comparison between the light chain of F23C6 and PBM 9-1 reveals a region of homology in CDR 2/FWK 3. The configuration of this site in the VL, as determined by comparison with a mAb, HyHEL-10, whose structure has been determined and is 97% homologous to the light chain of F23C6, conforms to the rules used to define antigenic determinants or Ids. A synthetic peptide having the F23C6 VL CDR 2/FWK 3 sequence inhibited the binding of F25F7 to F23C6 and 845D3. Taken together, these data suggest the Id recognized by F25F7 is defined, in part, by the PBM 9-1-like sequence of F23C6.

Epitope specificity and V gene expression of cerebrospinal fluid T cells specific for intact versus cryptic epitopes of myelin basic protein

Recent evidence supports the possible involvement of myelin basic protein (BP) as one of the target autoantigens in multiple sclerosis (MS), including elevated frequencies of MS blood and cerebrospinal fluid (CSF) T cells, and the presence in MS plaque tissue of V beta gene sequences and CDR3 motifs characteristic of BP-reactive T cells. Because of its proximity to the target organ, the CSF has long been thought to harbor T cells involved in the pathogenic process. In order to evaluate their frequency and response characteristics, BP-reactive T cells were isolated by limiting dilution from the CSF of patients with MS and other neurological diseases (OND) for quantitation and determination of epitope specificity and V alpha and V beta gene expression. In addition to isolates responsive to intact BP epitopes that were present at a significantly higher frequency in MS versus OND CSF, we here describe a second clonotype responsive to 'cryptic' BP epitopes that is present at approximately equal frequencies in MS and OND patients. In spite of their difference in recognition of intact versus 'cryptic' BP determinants, both clonotypes predominantly recognized epitopes in the N terminal half of human BP, using a similar V gene repertoire that included biased use of V alpha 2 and to a lesser degree V beta 7 and V beta 18. These V gene biases were not related to the epitope specificity of the T cells, indicating that V gene selection is not epitope-driven. These data suggest that there is differential recognition of intact versus 'cryptic' BP determinants in MS versus OND patients that may be related to the processing and presentation of BP to the immune system.

An immunochemical comparison of human myelin basic protein and its modified, citrullinated form, C8

An immunochemical analysis was conducted to compare the C1 isomer of human myelin basic protein (MBP) with the newly described and less cationic, citrullinated isomer of MBP referred to as C8. Ten polyclonal antisera directed at multiple epitopes or restricted regions of MBP were used in radioimmunoassays to examine MBP-C1 and MBP-C8. Antisera reactive with MBP peptide 1-14 clearly distinguished MBP-C1 from MBP-C8. Antisera to human MBP peptides 10-19 and 90-170, but not to MBP peptide 69-89, showed modest differences between MBP-C1 and MBP-C8. The MBP-C8s from multiple sclerosis (MS) and non-MS brain reacted essentially the same. With murine monoclonal antibodies and enzyme-linked immunosorbent assay (ELISA), differences between MBP-C8 and other isomers were shown for anti-MBP 10-19 but not for anti-MBP 1-9 or anti-MBP 80-89. These findings imply differences in sequence or conformation in the structure of MBP-C7 compared to MBP-C1, most notably near the amino terminus.

Role of plasmapheresis in acute disseminated (postinfectious) encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) is a demyelinating central nervous system disease that is associated with high morbidity and mortality. Although the recognition of ADEM may be facilitated by newer imaging techniques, the optimal treatment of this disease remains uncertain. We describe 4 patients with severe ADEM who responded to treatment that included intensive plasmapheresis. Two of the patients were in coma at the time that plasmapheresis was instituted, and all 4 patients made an excellent recovery. Immunologic studies revealed increased serum IgA levels, increased circulating immune complex levels as measured by the Raji cell assay, and decreased numbers of T and B cells prior to treatment of ADEM. These abnormalities improved following plasma exchange. Plasmapheresis appears to be effective in reversing the neuropathologic process in ADEM. The role of this treatment modality in ADEM requires further evaluation in controlled clinical trials.

Cells producing antibodies specific for myelin basic protein region 70-89 are predominant in cerebrospinal fluid from patients with multiple sclerosis

Cells secreting antibodies against guinea pig myelin and synthetic myelin basic protein (MBP) peptides were evaluated in cerebrospinal fluid (CSF) and blood from patients with multiple sclerosis (MS) and a variety of other neurological diseases (OND). The peptides used, reproducing amino acid sequences 1-20, 70-89, 108-126, or 157-166 of MBP, were selected on the basis of their hydrophilic and encephalitogenic properties. Low numbers of cells secreting IgG antibodies against myelin or each of the MBP peptides (about 1 per 50,000) were detected in peripheral blood, with no difference between MS and OND. In CSF, cells secreting IgG antibodies to MBP 70-89 were more frequently (p = 0.007) detected in patients with MS (1/380 IgG-secreting cells on average) than in patients with OND (1/2083 IgG-secreting cells on average). The frequencies of cells secreting antibodies against myelin or the three other MBP peptides were similar in MS and OND. Thus, evaluation of B cell immunity at the cellular level indicates that MBP 70-89 is an immunodominant B cell epitope in MS. It is not clear whether this intrathecal anti-MBP 70-89 IgG antibody response has any pathogenetic relevance in MS or is the result of myelin breakdown.

Diagnostic usefulness of cerebrospinal fluid in multiple sclerosis

Multiple sclerosis (MS) is one of the most common demyelinating diseases of the central nervous system affecting adults between the ages of 20 and 40 years. Clinically, it is characterized by episodes of exacerbations and remissions. Although the cause of MS is unknown, it is generally believed that one or more infectious agents triggers an autoimmune response that causes myelin destruction. There is no known cure for this disease; however, early diagnosis is helpful in the management of patients with MS. The diagnosis of MS is commonly made on the basis of established clinical criteria. No specific laboratory diagnostic test exists, but detection of abnormalities in cerebrospinal fluid (CSF) is a useful aid to support the clinical diagnosis of MS. This review describes the most common CSF abnormalities. These include (a) elevation of immunoglobulin G (IgG), IgG index and IgG synthesis rate; and (b) detection of oligoclonal IgG bands in the CSF by electrophoresis and isoelectric-focusing procedures.

Conformational correlates of the epitopes of human myelin basic protein peptide 80-89

Different epitopes residing within the decapeptide of residues 80-89 of human myelin basic protein (MBP) exist in the MBP-like material detected in human CSF and urine. In the present study, the structure of human MBP peptide 80-89 was examined by a combination of physical measurements and correlated with its varying immunochemical reaction with three polyclonal antisera. At least two epitopes are present in the decapeptide. Progressive shortening and reduction in net negative charge of MBP peptide 80-89 to form peptides 81-89, 82-89, 83-89, and 84-89 revealed an epitope not present in intact MBP. Circular dichroism and Fourier-transform infrared of these MBP peptides in water demonstrated random structure that was partially changed to beta-structure in the shorter peptides. In methanol, used as a model for a lipid environment, the random structure was diminished and was replaced by alpha-helix and beta-structure, especially in the shorter peptides. The findings indicate that the range of epitopes present in this decapeptide is influenced by conformation, which, unexpectedly, becomes progressively less random as the peptide becomes smaller, especially in a hydrophobic environment. This behavior has implications for the immunochemical detection of small antigens or antibodies to them in tissue extracts or body fluids.

Antibody to peptides of human myelin basic protein in post-rabies vaccine encephalomyelitis sera

Development of neurologic complications after Semple rabies vaccine is closely linked to development of antibody to myelin basic protein (MBP). The portions of MBP against which the antibodies are directed were analyzed by enzyme immunoassay in sera and cerebrospinal fluid from 27 patients with vaccine complications. Most of the antibody was directed to regions of MBP peptides 45-89 and 90-170. There was no apparent correlation between antibody specificity for MBP peptides 1-44, 45-89 and 90-170 and the type of post-vaccinal neurologic complication. We conclude that the immunoglobulin repertoire in human B lymphocytes for responding to human MBP favors the portion of the MBP molecule containing residues 45-170.

Resistance to experimental autoimmune encephalomyelitis induced by neonatal tolerization to myelin basic protein: clonal elimination vs. regulation of autoaggressive lymphocytes

The target autoantigen of experimental autoimmune encephalomyelitis (EAE), myelin basic protein (MBP), appears late in ontogeny. In the rat MBP is expressed first on days 2-3 post partum, at a development stage, when self tolerance to most other autoantigens has already developed. To shed light on the cellular mechanisms that lead to immunological self tolerance to MBP, we treated neonatal rats with high doses of MBP before ontogenetic appearance of this autoantigen. We found that high doses are required to confer MBP-specific tolerance lasting until the adult life. Neonatally tolerized, adult rats are completely resistant to induction of EAE by injection of MBP in complete Freund's adjuvant (CFA). Upon MBP CFA challenge, these animals develop a limited humoral response to MBP, but are completely unreactive to MBP on the T cell level. The function of antigen-presenting cells is unchanged by neonatal tolerization, and there is no evidence for the induction of suppressive mechanisms. Transfers of large numbers of tolerized lymphocytes to normal hosts fails to interfere with EAE inducibility. Moreover, neonatally tolerized lymphocytes do not reduce MBP reactivity of primed lymph node cells or T line cells in vitro. Finally, neonatally tolerized rats are susceptible to EAE transferred by activated primed lymphocytes or by in vitro-activated MBP-specific T line cells. The apparent deletion of MBP-specific T lymphocytes in neonatally tolerized rats is in striking contrast to the physiological self tolerance to MBP, which is characterized by the presence of MBP-specific clones in the normal immune repertoire.

Multiple sclerosis: an overview

Demyelinating lesions of MS are infiltrated by activated T-lymphocytes and macrophages with secretion of soluble factors. This results in the synthesis of oligoclonal immunoglobulin (IgG) by plasma cells. The activated T-lymphocytes migrate from the peripheral blood to the CNS. This hyperactive state is linked to a selective loss of the suppressor/inducer T-cell subset. Administration of a soluble factor--interferon gamma--enhances the immune response by promoting class II antigen expression on macrophages or astrocytes, resulting in a relapse. However, the reason for T-cell activation in peripheral blood is not known, nor is the antigen. Myelin basic protein (MBP) has been considered to be the target since MBP is able to induce chronic relapsing allergic encephalomyelitis (CRAE) in an animal model of MS. Yet other myelin antigens have succeeded in inducing CRAE in animal models, and anti-MBP antibodies have been found in healthy individuals. The possibility that the hyperimmune state results from a viral infection has not yet been proven. It is known that in Caucasians, a genetic susceptibility factor is linked to class II MHC. Using MRI it has been found that the presence of new plaques was not regularly correlated with relapses, which indicates that MS is an ongoing pathology process. Most drugs used in MS influence the immune response but have potential toxicity. Monoclonal antibodies offer the opportunity of specific targeting of T-cells and are promising for the future.

New monoclonal antibodies reactive with defined sequential epitopes in human myelin basic protein

Three new IgG monoclonal antibodies are described which recognise sequential epitopes of the human myelin basic protein (MBP) molecule in amino acid sequences 36-50, 64-75 and 80-89. Two of the secreting hybridomas were prepared by immunisation of mice with synthetic peptides. This procedure appears to generate antibodies of similar affinities to those made using intact myelin basic protein as the immunogen. It has the advantage that antibodies to preselected regions of the molecule can be made at will and the problem of subsequent epitope localisation is simplified. It is possible with synthetic peptides to generate antibodies of specificities which it would be impossible to achieve by immunisation with intact myelin basic protein. The monoclonal antibodies described here should be useful tools in studies of myelin catabolism in vivo and in vitro. Of particular interest is our Clone 22, making an antibody which reacts equally well with intact human MBP and synthetic peptide sequence 80-89 in liquid phase assays. Antibodies of this rare specificity have been claimed to be able to react with the peptides of myelin basic protein found in the spinal fluid of patients with multiple sclerosis.

Human myelin basic protein peptide 69-89: immunochemical features and use in immunoassays of cerebrospinal fluid

The characteristics and heterogeneity of the myelin basic protein (MBP)-like material appearing in cerebrospinal fluid (CSF) after acute central nervous system (CNS) myelin injury are unresolved. Antigenic material containing an epitope in the carboxyl-terminal portion of human MBP peptide 45-89 (from the intact molecule of 170 residues) is a prominent species of the MBP-like material present. In an effort to define further the MBP-like material in CSF and to enhance its detection, a modified double-antibody radioimmunoassay has been developed using a radioligand of human MBP synthetic peptide 69-89. This assay is more sensitive with results paralleling those of previously used MBP assays for CNS myelin damage. Results with this assay provide additional confirmation of the presence of an epitope of MBP in the decapeptide of MBP 80-89 but in a conformation simulating that of intact MBP in CSF after CNS myelin injury. Unexpected buffer effects were noted to influence the immunochemical behavior of some of the small peptides of MBP.

Measurement of immunoreactive myelin basic protein peptide (45-89) in cerebrospinal fluid

To measure myelin basic protein (MBP)-like material in cerebrospinal fluid, we compared two radioimmunoassays, both using the same antiserum to MBP but one using peptide (45-89) as the radioligand and standard (peptide assay), and the other using purified MBP as the radioligand and standard (MBP assay), with respect to their diagnostic sensitivity. Cerebrospinal fluid specimens from 185 patients with definite multiple sclerosis (MS) (n = 27), possible MS (n = 63), probable MS (n = 24), and other neurological disease (n = 71) were analyzed using both assays. The diagnostic sensitivity of the peptide assay was significantly better than that of the MBP assay in those with definite MS (sensitivity 59% and 30%, respectively); there was no significant difference in specificity. The peptide assay also showed better correlation with disease activity than the MBP assay: 14 patients classified as having active MS showed significantly higher sensitivity (78.6% versus 38%, p less than 0.04) when compared to patients with inactive disease. The MBP assay showed no significant difference between these two groups. Besides the increase in sensitivity, the actual molar concentrations of immunoreactive MBP detected using this peptide assay were considerably higher than those found using the MBP assay. These results show that the use of MBP antisera capable of recognizing epitopes present in the carboxyl half of MBP peptide (45-89) results in more sensitive detection of immunoreactive MBP when used with MBP peptide (45-89) as radiolabeled ligand in the assay.

The presence of immunoreactive myelin basic protein peptide in urine of persons with multiple sclerosis

A polyclonal antiserum has been produced that can detect nanogram amounts of myelin basic protein (MBP)-like material in unconcentrated human urine. The urinary immunoreactive material is cross-reactive with human MBP peptides 45-89 and 69-89, dialyzable, heat resistant, and is not artifact of either degradation of radioligand or salt effect. An octapeptide, MBP peptide 82-89, was demonstrated to be the smallest peptide containing the main epitope against which this antiserum was directed. This epitope differed from the major epitope recognized by antisera detecting MBP-like material in cerebrospinal fluid, implying that the MBP-like material is altered, presumably degraded, in the kidney. Results of gel filtration and high-performance liquid chromatography suggested a size of 1,000 daltons or less and a charge similar to that of human MBP peptide 80-89. In a group of 39 persons with multiple sclerosis, 48 with other neurological diseases, and 26 normal control subjects, the concentration of urinary MBP-like material, related to the concentration of urinary creatinine, was significantly higher in the multiple sclerosis group (22.0 ng MBP-like material/mg creatinine) than in the other neurological diseases or control groups, in which the values were 7.0 and 3.9 ng MBP-like material/mg creatinine, respectively. Variations in the level of MBP-like material appearing in the urine may provide a clinically feasible test for myelin damage. The precise identification of the chemical nature of the urinary MBP-like material may also furnish a means for further analyzing the in vivo catabolism of the potentially autoantigenic MBP.

Myelin basic protein-specific RNA levels in interleukin-2-stimulated oligodendrocytes

In the immune system, T- and B-cell proliferation, as well as B-cell immunoglobulin secretion, is induced by interleukin-2 (IL-2), a T-cell-derived lymphokine. IL-2 also influences the growth of glial cells, specifically, the proliferation and maturation of oligodendrocytes. Studies were conducted to investigate further IL-2-induced maturation of oligodendrocytes through its effect on the regulation of the myelin basic protein (MBP) gene. A cDNA probe specific for rat MBP and a double-antibody radioimmunoassay for MBP were used to quantitate MBP mRNA and protein levels in oligodendrocytes under different experimental conditions. We demonstrate that both MBP mRNA and protein levels are increased in IL-2-stimulated oligodendrocytes. MBP mRNA levels increase within 8 h after IL-2 stimulation, peak between 24 and 48 h, and then decline slightly. MBP protein levels increase 24 h after stimulation and peak at 72 h. MBP mRNA transcripts in the range of 2.0-2.4 kilobases are present in cultured rat oligodendrocytes, which are similar to the MBP mRNA transcripts detected in whole rat and mouse brain. These mRNA transcripts are specifically increased in quantity after oligodendrocyte stimulation with IL-2. These results suggest that one component of oligodendrocyte differentiation/maturation--MBP mRNA and protein expression--can be regulated in part by IL-2.

Demyelinating canine distemper encephalomyelitis: measurement of myelin basic protein in cerebrospinal fluid

Beagle dogs were experimentally infected with the Cornell A75-17 strain of canine distemper virus. At three time points post-infection (PI), immunoreactive myelin basic protein (MBP) was measured in cerebrospinal fluid (CSF). Levels were correlated with neuropathological findings, interferon in CSF and virus isolation from the brain. CSF from animals inoculated with Cornell A75-17 strain often showed detectable immunoreactive MBP late in the disease course. As anticipated from earlier morphological studies, CSF drawn around day 20 PI lacked MBP while subsequent samples were positive. Dogs with severe demyelination had elevated values of immunoreactive MBP while dogs with only mild inflammation had little or none. Release of MBP or MBP peptides into CSF of dogs with canine distemper may be a valuable laboratory test in studies of the natural history of this disease and in assessing the response to treatment. Whether an immune response to MBP plays an immunopathogenic role in the chronic, demyelinating phase of canine distemper encephalitis remains to be determined.