Detection of Protein Aggregates in Brain and Cerebrospinal Fluid Derived from Multiple Sclerosis Patients

Soluble oligomers are common to most amyloids and may represent the primary toxic species of amyloids, like the Abeta peptide in Alzheimer's disease (AD). Here we show that all of the soluble oligomers tested display a common conformation-dependent structure that is unique to soluble oligomers regardless of sequence. The in vitro toxicity of soluble oligomers is inhibited by oligomer-specific antibody. Soluble oligomers have a unique distribution in human AD brain that is distinct from fibrillar amyloid. These results indicate that different types of soluble amyloid oligomers have a common structure and suggest they share a common mechanism of toxicity.

Two or more oligoclonal IgG bands (OB) detected by separation of cerebrospinal fluid (CSF) proteins while not demonstrable in corresponding serum reflect a local B-cell response accompanying central nervous system (CNS) inflammation. Using optimized, standardized methodology, preferentially protein separation by isoelectric focusing followed by immunoblotting, more than 95% of patients with multiple sclerosis (MS) have CSF OB of IgG class not detectable in serum, thereby providing powerful evidence for the diagnosis of MS. Once present, CSF OB persists in the individual patient irrespective of MS course or therapy. Because of the high sensitivity of CSF OB in MS as well as its high specificity in the appropriate clinical setting, examination of CSF for OB of IgG class can be strongly recommended to obtain support for the diagnosis of MS and identify patients with clinically isolated syndrome (CIS) at increased risk of developing MS. The IgG index equal to CSF/serum IgG:CSF/serum albumin is elevated in about 70% of MS patients, but rarely in CSF OB-negative MS. Because of lower diagnostic sensitivity, IgG index cannot be recommended as replacement of CSF OB in the diagnosis of MS but, when elevated, as additional evidence for an augmented B-cell response within the CNS that is compatible with MS. Although the clinical picture as well as findings from magnetic resonance imaging of the brain and spinal cord are essential for an MS diagnosis, this should be re-evaluated in CSF OB-negative patients, keeping in mind the many disease entities imitating MS. Recommended diagnostic criteria for MS must include definitions of the role of lumbar puncture and of clearly specified, optimized and standardized routine CSF investigations including for the presence of CSF IgG OB. There is a need for concerted long-term follow-up studies of the subgroup of MS patients without CSF OB regarding e.g. prognostic and immunologic features. For inclusion in trials of disease-modulating drugs, it is recommended that patients with MS or CIS are selected regarding presence vs. absence of CSF OB. Development and evaluation of new technologies to define local vs. systemic B-cell responses in patients with MS or CIS vs. patients with other inflammatory neurological diseases should shed new light on the role of CSF OB, which remains enigmatic.

The paired helical filaments (PHFs) of Alzheimer's disease consist mainly of the microtubule-associated protein tau. PHF tau differs from normal human brain tau in that it has a higher Mr and a special state of phosphorylation. However, the protein kinase(s) involved, the phosphorylation sites on tau and the resulting conformational changes are only poorly understood. Here we show that a new monoclonal antibody, AT8, records the PHF-like state of tau in vitro, and we describe a kinase activity that turns normal tau into a PHF-like state. The epitope of AT8 is around residue 200, outside the region of internal repeats and requires the phosphorylation of serines 199 and/or 202. Both of these are followed by a proline, suggesting that the kinase activity belongs to the family of proline-directed kinases. The epitope of AT8 is nearly coincident with that of another phosphorylation-dependent antibody, TAU1 [Binder, L.I., Frankfurter, A. and Rebhun, L. (1985) J. Cell Biol., 101, 1371-1378], but the two are complementary since TAU1 requires a dephosphorylated epitope.