The requirement of ammonium or other cations linked with p-cresol sulfate for cross-reactivity with a peptide of myelin basic protein

Urinary myelin basic protein-like material (MBPLM), so designated because of its immunoreactivity with a polyclonal antibody directed against a cryptic epitope located in residues 83-89 of myelin basic protein (MBP), exists in humans normally but increases in concentration in patients with multiple sclerosis who have progressive disease. Given its possible role in reflecting events of neural tissue destruction occurring in multiple sclerosis, urinary MBPLM is a candidate surrogate marker for this phase of the disease. Previously, it has been demonstrated that p-cresol sulfate (PCS) is the dominant component of MBPLM; however, another component(s) was essential in enabling p-cresol sulfate to have molecular mimicry with MBP peptide 83-89 detected by immunoreactivity. In the present investigation, this remaining component(s) was characterized by a combination of high performance size exclusion chromatography followed by nuclear magnetic resonance spectroscopy and shown to be ammonium. The monovalent cation ammonium could be substituted in vitro by several different monovalent and divalent cations, most notably zinc, in restoring to deprotonated p-cresol sulfate its immunoreactivity as MBPLM. These findings indicate the basis for the unexpected molecular mimicry between an epitope of an encephalitogenic protein and a complex containing a small organic molecule, p-cresol sulfate. Furthermore, the reaction of either ammonium or other cations with p-cresol sulfate may represent an in vivo process directly related to damage of axonal membranes.

Immunological indicators of disease activity and prognosis in multiple sclerosis

The need to ensure an accurate diagnosis and proper treatment for multiple sclerosis patients, considering the various clinical and immunopathological subtypes of the disease, requires the identification of biomarkers that measure disease activity and predict the course of disease development in individual patients. Moreover, the identification of effective indicators will lead not only to optimized patient treatment but also to the development of better tools for evaluating clinical trials. Recent studies focusing on the identification of possible immunological markers in multiple sclerosis will be reviewed.

Relationship of urinary myelin basic protein-like material with cranial magnetic resonance imaging in advanced multiple sclerosis

BACKGROUND

A significant correlation exists between disability and the volume of black holes (BHL VOL), defined as hypointense lesions on T1-weighted cranial magnetic resonance imaging. A consistent correlation has also been reported between urinary myelin basic protein-like material (MBPLM) and the transition toward secondary progression (SP) from relapsing-remitting (RR) multiple sclerosis (MS).

OBJECTIVE

To improve the management of MS through a noninvasive and cost-effective test for monitoring disease activity or disease status.

DESIGN AND METHODS

From 662 patients with MS (86 with RR MS, 259 with SP MS without continued attacks, and 317 with SP MS with continued attacks), 24-hour urine samples were obtained at enrollment in the phase 3 Linomide (roquinimex) drug study. The urine specimens were analyzed for MBPLM and correlated with clinical features and findings on cranial magnetic resonance imaging.

RESULTS

Significant but weak correlations existed between urinary MBPLM and BHL VOL in all patients with MS (r = 0.114, P =.003; n = 662), patients with SP MS without attacks (r = 0.185, P =.003; n = 259), and all patients with SP MS (r = 0.122, P =.003; n = 576). No significant correlations were detected in the RR MS group or any of the disease groups or subgroups whose Expanded Disability Status Scale score was 5.0 or lower. In subgroup analysis, the most significant correlation was detected between urinary MBPLM after adjustment for creatinine and BHL VOL in patients with SP MS with an Expanded Disability Status Scale score of 5.5 or higher but without continued relapses (r = 0.417, P<.001; n = 138).

CONCLUSIONS

In patients with advanced SP MS, urinary MBPLM may possibly serve as an indicator of failed remission and axonal damage. Urinary MBPLM correlates with disease status in MS, especially the transition of RR MS to SP MS with advancing disability.

p-Cresol sulfate is the dominant component of urinary myelin basic protein like material

Multiple sclerosis (MS) is clinically heterogeneous and has an uncertain natural history. A high priority for more effective treatment of MS is an objective and feasible laboratory test for predicting the disease's course and response to treatments. Urinary myelin basic protein (MBP)-like material (MBPLM), so designated because it is immunoreactive as a cryptic epitope in peptide 83-89 of the human MBP molecule of 170 amino acids, is present in normal adults, remains normal in relapsing-remitting, but increases in progressive MS. In the present investigation, MBPLM was purified from urine and characterized. p-Cresol sulfate is the major component of urinary MBPLM. This conclusion is based on the following: (1) MBPLM and p-cresol sulfate both have a mass of 187 on negative scans by electrospray ionization mass spectrometry, the same fragments on tandem mass spectrometry of 80 (SO(-)(3)) and 107 (methylphenol), and similar profiles on multiple reaction monitoring; (2) (1)H and (13)C nuclear magnetic resonance spectroscopy revealed identical spectra for MBPLM and p-cresol sulfate; (3) purified p-cresol sulfate reacted in parallel with MBP peptide 83-89 in the same radioimmunoassay for MBPLM; and (4) p-cresol sulfate has the same behavior on preparative HPLC columns as urinary MBPLM. The unexpected immunochemical degeneracy permitting a cross-reaction between p-cresol sulfate and a peptide of an encephalitogenic myelin protein is postulated to be based on shared conformational features. The mechanisms by which urinary p-cresol sulfate, possibly derived from tyrosine-SO(4), reflects progressive worsening that is disabling in MS are unknown.

Clinical and laboratory features of primary progressive and secondary progressive MS

OBJECTIVE

To compare the clinical and laboratory features of primary progressive (PP) and secondary progressive (SP) MS, to evaluate the role of CSF and urine myelin basic protein-like material (MBPLM) in differentiating PP from SP MS, and to assess the utility of urine MBPLM as a surrogate marker of disease activity in progressive MS.

BACKGROUND

The current categorization of subtypes of MS is based solely on clinical and temporal characteristics of the disease. Laboratory markers are needed that can differentiate reliably the subtypes of MS and serve as surrogate markers of disease progression.

METHODS

Clinical and paraclinical data of 51 PPMS and 140 SPMS patients were reviewed retrospectively. CSF and urine MBPLM were measured using a double-antibody radioimmunoassay.

RESULTS

PPMS was more likely to present with progressive myelopathy (p < or = 0.001) after the age of 40 years (p = < or = 0.001), and it affected men relatively more often than SPMS (male-to-female ratio, 1:1.7 versus 1:3.2 respectively). Ambulatory assistance was required by PP patients more often and earlier than in those with SPMS. The incidence of abnormal CSF, evoked potential, and cranial MRI studies was similar in the two groups. Spinal cord MRI abnormalities were noted significantly more often in SP disease. There was an insignificant trend of higher CSF MBPLM in SPMS compared with PPMS. Urine MBPLM and MBPLM/creatinine were significantly higher in SPMS than in PPMS. However, the values of urine MBPLM and MBPLM/creatinine at the initial visits of patients with PPMS and SPMS were not significantly different. Urine MBPLM/creatinine was significantly higher in both PPMS and SPMS compared with normal control subjects. No correlation was found between urine MBPLM and disease duration or between urine MBPLM and clinical disability. There was no correlation between urine MBPLM/creatinine and either disease duration or clinical disability.

CONCLUSIONS

These findings provide additional evidence of the differences in PPMS and SPMS, notably in the associated changes in MBPLM in urine, and also suggest a possible role for urine MBPLM in identifying patient cohorts. The high urine MBPLM levels in progressive MS patients indicate a potential role of this marker for assessing responsiveness to therapeutic interventions.

Urinary myelin basic protein-like material in patients with multiple sclerosis during interferon beta-1b treatment

OBJECTIVES

To determine levels of urinary myelin basic protein-like material (MBPLM) in patients with multiple sclerosis (MS) openly treated with interferon beta-1b and to correlate these with clinical changes.

BACKGROUND

Levels of urinary MBPLM correlate with the presence of the progressive phase of MS and with the disease burden detected on T2-weighted, cranial magnetic resonance imaging. Measurement of urinary MBPLM level may be a feasible test for monitoring or predicting response to therapeutic measures.

DESIGN AND METHODS

In a prospective study at one site, 166 patients with MS (131 with relapsing-remitting [RR] and 35 with secondary progressive [SP] disease) were treated for a minimum of 1 year and up to 3 years with interferon beta-1b and underwent assessment for neurologic disability (Expanded Disability Status Scale and Scripps Neurological Rating Scale) and change in disease subtype. Urine samples were obtained at 1219 of 1378 clinic visits, and urinary MBPLM level was determined and related to creatinine level to adjust for renal function.

RESULTS

Statistical analysis using the general linear models procedure confirmed previous findings that the level of urinary MBPLM related to urinary creatinine level (MBPLM/creatinine) was higher (P<.001) in patients with SP than RR MS. Of the 131 patients with RR MS, SP disease developed in 13 during the observation period. Compared with those in the RR group, the RR to SP group had a higher level (P<.001) of urinary MBPLM and did not differ from the SP group.

CONCLUSIONS

The level of urinary MBPLM is higher in SP MS than RR MS but not in RR MS that converts to SP MS. Level of urinary MBPLM may permit the examination of treatment tested to prevent RR disease from becoming progressive.

Age-related changes in the level of urinary myelin basic protein-like material during childhood

OBJECTIVE

To examine the developmental profile of myelin basic protein-like material (MBPLM) in urine. If urinary MBPLM exhibits a developmental profile corresponding to that of forebrain myelination, certain inferences should follow deviations from normal. Thus, MBPLM might provide a marker for monitoring the neurodevelopmental status in infants at risk for adverse outcomes.

BACKGROUND

MBPLM in different immunochemical forms is detectable in human CSF and urine, presumably a result of myelin basic protein (MBP) catabolism. Urinary MBPLM has been used successfully as a marker of disease status in adults with MS. Urinary MBPLM increases in MS patients changing from a relapsing-remitting to a progressive course, possibly reflecting attempted or failed remyelination. Scant information exists concerning the presence or specific levels of urinary MBPLM during infancy and childhood when myelination is most active.

METHODS

MBPLM was assayed in 402 urine specimens from 398 infants and children ranging in age from birth to 17 years according to previously described methods.

RESULTS

MBPLM is detectable in urine from newborns, although at substantially lower levels than in adults (157.3 +/- 83.9 ng/mg creatinine). Whether expressed as nanograms per milliliter urine or nanograms per milligram creatinine, MBPLM levels are lower (p < 0.05) from birth through 12 months and greater (p < 0.05) between ages 2 to 8 years than in adults.

CONCLUSION

Human urinary MBPLM exhibits a developmental profile that parallels the onset of normal myelination and exceeds normal adult values through early childhood. Thus, urinary MBPLM could serve as a useful marker of myelination in the developing child.

Myelin basic protein-like material in the urine of multiple sclerosis patients: relationships to clinical and neuroimaging changes

Urinary myelin basic protein-like material (MBPLM) represents material which is cross-reactive with a cryptic epitope in peptide 84-89 of human myelin basic protein. While normally present at moderate levels in the adult, these levels rise higher in patients who have secondary progressive multiple sclerosis (MS). The increase in urine MBPLM correlates with the burden of disease detected by T2-weighted cranial magnetic resonance imaging. There is no correlation between urinary MBPLM and acute disease activity in relapsing-remitting MS. The first major need for improving the clinical utility of measurements of MBPLM in urine in MS patients is to delineate its exact chemical features so that assays may be improved and a potential biological role of the MBPLM better understood. The second major task is to apply the group data accumulated and apply them to individual patients. This could prove to be means to individually direct treatment and determine its effectiveness.

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.

Urinary myelin basic protein-like material as a correlate of the progression of multiple sclerosis

In the multicenter, randomized, placebo-controlled trial of alternate-day injections of recombinant interferon beta-1b in relapsing-remitting multiple sclerosis (MS), urine specimens were collected periodically from all patients (n = 64) in two of the clinical test sites over the 2 years of the study. Urine specimens were also collected over two consecutive 24-hour periods from 43 patients from a third center. Urine samples were assayed for their content of myelin basic protein-like material (MBPLM), the level of which was correlated with clinical changes, cranial magnetic resonance imaging results, and the development of progressive disease. Concordant changes in creatinine values affected some of the relationships of MBPLM. The level of urinary MBPLM correlated with a chronic progressive course and with the number of lesions and the total lesion area on cranial magnetic resonance images. A rise in the level of urinary MBPLM appeared to antedate the clinical transition from a relapsing-remitting to a chronic progressive course. By chance, the randomized entry of patients led to significant differences in urinary MBPLM levels among the three treatment groups, thus precluding correlation studies of treatment effects. However, the patient group from which 24-hour specimens were collected showed that the patients with relapsing-remitting MS changing to a chronic progressive course, and more specifically, those patients with chronic progressive MS receiving placebo, had the highest values of urinary MBPLM. These findings indicate that urinary MBPLM may offer an objective test and possibly serve as a surrogate marker for detecting or predicting the failure of remission or the transition to a progressive phase of MS.

Monoclonal and polyclonal antibody responses to the myelin basic protein epitope present in human urine

The myelin basic protein (MBP)-like material (MBPLM) in human urine is expressed in a cryptic epitope(s) present in MBP peptide 80-89 and absent or inaccessible in intact MBP. These features of urinary MBPLM have made it difficult to produce reagents for its further characterization. Using an immunogen of keyhole limpet hemocyanin conjugated to MBP peptide cys 74-89, polyclonal antiserum to urinary MBPLM was prepared. With the same immunogen and screening with urine, the product from one of over 1600 wells from the original fusion, produced monoclonal antibody (mAb) which could detect urinary MBPLM. By radioimmunoassay two rabbit polyclonal reagents recognized a cryptic epitope in MBP peptide 84-89 while the two mAbs recognized another cryptic epitope in MBP peptide 80-85. Both could be used for quantitation of MBPLM in urine. These and previous results indicate the presence of at least three epitopes, one noncryptic and two cryptic, in the decapeptide of MBP 80-89. Of the two cryptic epitopes, the one near the carboxyl-terminal is dominant to that in the amino-terminal portion. The detection of urinary MBPLM with reagents with two different specificities suggests the presence of two or more small MBP peptides in urine.

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.

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.

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.