Isoelectric focusing of CSF and serum proteins in neurological disorders combined with benign and malignant proliferations of reticulocytes, lymphocytes and plasmocytes

Proteomics of Multiple Sclerosis: Inherent Issues in Defining the Pathoetiology and Identifying (Early) Biomarkers

Multiple Sclerosis (MS) is a demyelinating disease of the human central nervous system having an unconfirmed pathoetiology. Although animal models are used to mimic the pathology and clinical symptoms, no single model successfully replicates the full complexity of MS from its initial clinical identification through disease progression. Most importantly, a lack of preclinical biomarkers is hampering the earliest possible diagnosis and treatment. Notably, the development of rationally targeted therapeutics enabling pre-emptive treatment to halt the disease is also delayed without such biomarkers. Using literature mining and bioinformatic analyses, this review assessed the available proteomic studies of MS patients and animal models to discern (1) whether the models effectively mimic MS; and (2) whether reasonable biomarker candidates have been identified. The implication and necessity of assessing proteoforms and the critical importance of this to identifying rational biomarkers are discussed. Moreover, the challenges of using different proteomic analytical approaches and biological samples are also addressed.

Immunoblotting techniques with picogram sensitivity in cerebrospinal fluid protein detection

Agarose isoelectric focusing followed by blotting with nitrocellulose, nylon or polyvinylidene difluoride membranes, and immunochemical detection of cerebrospinal fluid IgG with various combinations of antisera, was evaluated. Polyvinylidene difluoride proved to be an easy-to-handle and reliable membrane for protein blotting. Among immunochemical visualization reactions, the most sensitive employed biotinylated goat anti-human IgG followed by streptavidin colloidal gold conjugate and silver enhancement in 20% w/v urea, allowing a sensitivity of less then 1 picogram IgG/band.

Peripheral neuropathy in IgD myeloma. Cerebrospinal fluid paraprotein analysis in three cases

High resolution polyacrylamide gel isoelectric focusing (IEF), followed by direct immunofixation with anti-delta chains monospecific antibodies, were used to detect and identify IgD paraprotein in the cerebrospinal fluid (CSF) of 3 patients affected by IgD myeloma. Two of these patients presented a paraproteinemic neuropathy. Blood-brain barrier damage was investigated by means of CSF/serum albumin ratio. IgG index and CSF and serum IgD/albumin ratio were also evaluated. An intrathecal origin of the IgD paraprotein was excluded. The correlation between the presence of the paraprotein in the CSF and the possible neurological involvement was also examined.

Cerebrospinal fluid paraproteins in neurological disorders

Paraproteins display a characteristic pattern of limited heterogeneity on isoelectric focusing. In a group of 50 patients with various neurological disorders and paraproteinaemia this pattern could be demonstrated in serum and cerebrospinal fluid simultaneously, regardless of the form of nervous system involvement or of the function of the blood-cerebrospinal fluid barrier. Although there were no qualitative differences in the pattern between paraproteins from benign and malignant cases, a distinct quantitative difference was found: Paraproteins from myeloma patients had significantly more subfractions extending over a wider pH range than paraproteins from patients with benign monoclonal gammopathy. Due to the high sensitivity of isoelectric focusing, more paraproteins could be detected in cases where other electrophoretic methods including immunoelectrophoresis were negative. A surprisingly high percentage of patients was found with benign monoclonal gammopathy and vascular lesions of the central nervous system.

Peripheral neuropathy in patients with benign monoclonal gammopathy--a pilot study

It is well known that peripheral neuropathy occurs in patients with myeloma or macroglobulinaemia, but its pathogenesis is still obscure. In recent years, neuropathy has also been reported in association with benign monoclonal or oligoclonal gammopathy. Modern histo-immunological methods have revealed evidence of antibody production to peripheral nerve tissue, probably the myelin sheath. The present study included 21 unselected, consecutive patients with benign monoclonal gammopathy observed in the Division of Haematology. Clinical and laboratory investigations included electrophysiological examination and analyses of the M components. Of the 21 patients 11 had noticed slight neuropathic symptoms in their extremities; in 5 both clinical and electrophysiological findings were compatible with neuropathy; 6 showed positive clinical signs of neuropathy; 4 had either positive electromyographic or electroneurographic findings. In summary, 15 of 21 patients had some signs of peripheral neuropathy. In spite of the screening design of the study, this strikingly high frequency is comparable with other recent reports. Haematological studies did not reveal any significant differences between the patient groups with positive or negative neurological findings. The findings indicate that even benign gammopathies may be associated with peripheral neuropathy.

Benign monoclonal gammopathy and peripheral neuropathy

Peripheral neuropathy has been described in malignant plasma cell dyscrasias such as multiple myeloma and Waldenstöm's macroglobulinaemia. Since it is not known whether the neuropathy is related to the plasma cell disorder or is a paramalignant phenomenon, 21 consecutive out-patients with benign monoclonal gammopathy (BMG) were analysed for peripheral neuropathies. Eleven patients had noticed slight motor and/or sensory extremity symptoms. Clinical examination, electromyographic and electroneurographic studies of the upper and lower extremities were performed. In five patients all results indicated a neuropathy, six other patients had clinical signs of neuropathy and four additional patients had positive electromyographic and/or electroneurographic results compatible with neuropathy. There were no significant differences in haematological parameters between the group where all results indicated a neuropathy and the totally negative group or between the two groups with and without clinical neuropathy. Thus, the benign form of plasma cell dyscrasias seems also to be associated with mild clinical or subclinical peripheral neuropathy.

Isoelectric focusing and quantitative estimation of cerebrospinal fluid and serum IgG in idiopathic polyneuropathy

Isoelectric focusing and quantitative estimation of serum and CSF IgG were performed in 85 patients with idiopathic polyneuropathy (IP), subdivided according to the clinical course (acute, subacute, recurrent, chronic). Acute IP very frequently had an increase of oligoclonal and/or polyclonal serum IgG during the progressive phase and blood-CSF barrier damage accompanied by polyclonal IgG intrathecal synthesis during the stationary phase. Polyclonal IgG intrathecal synthesis was also present in several not acute IP and seemed to forecast unfavorable course. Oligoclonal IgG synthesis occurs very rarely within CSF but is a frequent finding in serum of patients with IP. Abnormalities of the IgG serum pattern are neither specific for any clinical course of IP nor of prognostic value. The possible significance of such findings is discussed.

Isoelectric focusing of CSF proteins in known or probable infectious neurological diseases and the Guillain-Barré syndrome

The CSF and serum proteins of 120 patients with known or probable infectious neurological diseases or the Guillain-Barré syndrome were examined with thin-layer IEF. All but two of these patients exhibited one or combinations of different CSF-protein aberrations in the acidic and alkaline range. Aberrant non-Ig fractions (including transferrin, the tau-fraction and gamma-trace protein) were found in frequencies varying between 4 and 48%. CSF Ig components of restricted heterogeneity, i.e. oligoclonal bands and/or regional increases of gamma-globulins, were more frequent in patients with (meningo-)encephalitic or (meningo-)-myelitis/radiculitic disorders (respectively 69 and 48%) than in subjects with meningitis or Guillain-Barré syndrome (17%). The occurrence of such Ig abnormalities was higher in subacute or chronic than in acute disease and in subjects examined greater than 4 weeks after the onset rather than earlier. Ig-band spectra with marked anodal extension were found predominantly in (meningo-)encephalitic disorders with infratentorial symptoms. Age and sex were not found to influence the occurrence of abnormal Ig fractions. Such components could be detected in spite of pronounced blood-CSF barrier defects.

CSF protein examinations with thin-layer isoelectric focusing in multiple sclerosis

Thin-layer IEF, due to its extremely high resolving capacity, has been found to be quite valuable for CSF protein examinations, one important advantage of the technique being its excellent capacity for separation of immunoglobulins. The CSF and serum proteins of 230 patients with clinically verified or probable MS and 20 subjects with optic neuritis were examined with thin-layer IEF and the findings were compared with clinical data and results of other CSF examinations. All but 3 of the MS patients and about two thirds of the subjects with optic neuritis inhibited one or combinations of different CSF protein aberrations in the acidic and alkaline range. Oligoclonal bands and/or regional increases of Ig fractions, changes compatible with intrathecal Ig synthesis, were detected in respectively 95 and 80% of patients with clinically verified and probable MS and 30% of subjects with optic neuritis. Other aberrant CSF protein fractions (including transferrin, the taufraction and gamma-trace protein) were found in about half of the cases; some of these fractions had the highest occurrence in patients with the most extensive Ig abnormalities. The diverse CSF protein aberrations seemed to be influenced by the duration and course of the disorder as well as the probable sites of lesions; further factors might be the release of decomposition products from destroyed tissues, the genetically determined reactivity of the individual and the presence of possible agents.