Simultaneous measurement of 2':3' cyclic-nucleotide 3' phosphodiesterase and RNase activities in sera and spinal fluids of multiple sclerosis patients

Disease biomarkers in multiple sclerosis: potential for use in therapeutic decision making

Multiple sclerosis (MS) is an autoimmune disorder of the brain and spinal cord that predominantly affects white matter. MS has a variable clinical presentation and has no 'diagnostic' laboratory test; this often results in delays to definite diagnosis. In confronting the disease, early diagnosis and appropriate, timely therapeutic intervention are critical factors in ensuring favorable long-term outcomes. The availability of reliable biomarkers could radically alter our management of MS at critical phases of the disease spectrum. Identification of markers that could predict the development of MS in high-risk populations would allow for intervention strategies that may prevent evolution to definite disease. Work with anti-myelin antibodies and the ongoing analysis of microarray gene expression have thus far not yielded biomarkers that predict future disease development. Similarly, extensive studies with serum and cerebrospinal fluid (CSF) have not yielded a disease-specific and sensitive diagnostic biomarker for MS. Establishment of disease diagnosis always leads to questions about long-term prognosis because in an individual patient the natural history of the disease is clinically unpredictable. Biomarkers that correlate with myelin loss, spinal cord disease, grey matter and subcortical demyelination need to be developed in order to accurately predict the disease course. The bulk of effort in biomarker development in MS has been concentrated in the area of monitoring disease activity. At present, a disease 'activation' panel of CSF biomarkers would include the following: interleukin-6 or its soluble receptor, nitric oxide and nitric oxide synthase, osteopontin, and fetuin-A. Although disease activity in MS is predominantly inflammatory, disease progression is likely to be the result of neurodegeneration. Therefore, the roles of proteins indicative of neuronal, axonal, and glial loss such as neurofilaments, tau, 14-3-3 proteins, and N-acetylaspartate are all under investigation, as are proteins affecting remyelination and regeneration, such as Nogo-A. With the increasing awareness of cognition dysfunction in MS, molecules such as apolipoprotein and proteins in the amyloid precursor protein pathway implicated in dementia are also being examined. Serum biomarkers that help monitor therapeutic efficacy such as the titer of antibody to beta-interferon, a first-line medication in MS, are established in clinical practice. Ongoing work with biomarkers that reflect drug bioavailability and factors that distinguish between medication responders and nonresponders are also under investigation. The discovery of new biomarkers relies on applying advances in proteomics along with microarray gene and antigen analysis and will hopefully result in the establishment of specific biomarkers for MS.

Dual implication of 2',3'-cyclic nucleotide 3' phosphodiesterase as major autoantigen and C3 complement-binding protein in the pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is characterized by intra-blood-brain barrier immunoglobulin synthesis that persists lifelong. Subcellular fractionation and two-dimensional electrophoresis were used in conjunction with immune precipitation and immunoblotting to identify antigenic determinants for this immunoglobulin. We report that 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP), a protein associated with oligodendrocyte/myelin membranes, also present in lymphocytes and retina, is one major target for the humoral response. Antibodies to CNP are detected in sera of 74% of MS patients. The antibodies are IgM and are present in serum in high titer as well as in cerebrospinal fluid. The antibody response is temporally persistent, consistent with systemic immune activation and persistent antigenic stimulation. Moreover, CNP is isolated as an immune complex from MS brain. CNP is expressed as two isoforms, with CNPII identical to CNPI but with a 20-amino acid extension at the amino terminus of CNPII; however, the antibody response is exclusively restricted to CNPI. In contrast, both isoforms bind the C3 complement, providing a plausible mechanism in MS central nervous system (CNS) for opsonization of myelin membrane CNP, mediated via the C3 receptor, and phagocytosis of CNP-Ig immune complexes, mediated by membrane Ig Fc receptors of macrophages and CNS microglia.

A derivative of myelin-associated glycoprotein in cerebrospinal fluid of normal subjects and patients with neurological disease

A procedure for quantitating the myelin-associated glycoprotein (MAG) in cerebrospinal fluid (CSF) was developed. The procedure involved immunoprecipitation with rabbit polyclonal anti-MAG antiserum followed by immune staining of electroblots with the monoclonal antibody HNK-1. This method could detect as little as 2 ng of MAG per ml of CSF and could accurately measure levels of 5 ng/ml or greater. No intact MAG was detected in any of the CSF samples examined, but all samples contained the 90K dalton proteolytic derivative of MAG called dMAG. Samples from normal volunteers and patients with demyelinating diseases contained levels of dMAG ranging from 2 to 13 ng/ml. There was no correlation of dMAG levels with levels of myelin basic protein or with active demyelinating disease. The relatively high levels of dMAG, even in control CSF samples, probably resulted from normal physiological turnover of MAG and could possibly obscure any additional increments of MAG or dMAG release that might occur as a result of demyelination.

Membrane-bound 2',3',-cyclic nucleotide 3'-phosphohydrolase activity of lymphocytes, granulocytes and erythrocytes in multiple sclerosis

A sensitive fluorimetric method was used for the assay of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) activity of lymphocyte, granulocyte and erythrocyte membranes from patients with multiple sclerosis (MS). The data obtained were compared with the corresponding data from normal individuals. CNP activities of granulocyte and erythrocyte membranes of the 2 groups did not differ significantly. However, a 40% decreased membrane CNP activity of MS lymphocytes was found when the data were compared with the normal lymphocytes' activity (P less than 0.0005) by both the non-parametric median test and Student's t-test. A role of CNP in immunoregulation is suggested.