Methylated Peptides Derived from Tau Protein and their Antibodies for Diagnosis and Therapy of Alzheimer's Disease

Abstract

In sporadic Alzheimer's disease, neurofibrillary lesion formation is preceded by extensive post-translational modification of the microtubule associated protein tau. Immunoassays have been developed recently that detect tau in biological specimens, thus providing a means for pre-mortem diagnosis of Alzheimer's disease, which has remained elusive. These assays have been improved by the analysis of relevant post-translational modifications, such as phosphorylation, however opportunity for improvement remains. The present invention addresses this issue by disclosing synthetic methylated peptides derived from the tau protein of paired helical filaments and non-diseased control brain. Alzheimer's disease specificity is provided by the presence or absence of methyl moieties on lysine residues and differences between mono-, di-, and tri-methylation. The methylated peptide is useful as an antigen and a binding partner for identifying compounds that interact with the peptide and the methylated tau protein, including antibodies that can distinguish non-diseased brain from that affected by Alzheimer's disease. The resulting antibodies are useful diagnostically and therapeutically. The compounds that specifically bind to methylated tau proteins are useful for eliminating abnormally methylated tau.

1 . A method of diagnosing Alzheimer's disease, or a predisposition of an individual to Alzheimer's disease, the method comprising:
 a. obtaining a test biological sample from an individual, the test biological sample being chosen from cerebrospinal fluid, blood, serum, and plasma;   b. quantifying the amounts of a methylated tau protein in the test biological sample obtained in step a, said methylation occurring on one or more lysine residues, wherein said quantifying of said methylated tau protein is achieved via use of an antibody to a methylated peptide derived from tau protein, wherein the peptide is methylated on one or more lysines, and wherein the one or more methylated lysines are numbered according to the human tau isoform with NCBI accession number NP_005901 and include one or more of the following residues: 24, 44, 163, 174, 180, 254, 267, 281, 290, 311, 317, 340, 353, 369, and 395;   c. comparing the amounts of methylated tau protein in the test biological sample with the amounts present in a control biological sample from a subject without Alzheimer's disease; and   d. diagnosing Alzheimer's disease, or predisposition thereto, based on a difference in the amount of the methylated tau protein in the test biological sample as compared to the control biological sample.   
     
     
         2 . The method of  claim 1 , further comprising comparing and/or detecting a change in the level of the methylated tau protein present in samples taken on two or more occasions. 
     
     
         3 . The method of  claim 1 , further comprising comparing the amount of the methylated tau protein present in said test biological sample with more than one control sample. 
     
     
         4 . The method of  claim 1 , wherein the biological sample is an extract, purification, or dilution from the sample chosen from cerebrospinal fluid, blood, serum, and plasma. 
     
     
         5 . The method of  claim 1 , wherein the antibody is chosen from a monoclonal antibody, a fragment of a monoclonal antibody, a polyclonal antibody, and a fragment of a polyclonal antibody. 
     
     
         6 . The method of  claim 5 , wherein the antibody is a recombinant antibody and is chosen from bifunctional antibodies, chimeric antibodies, and humanized antibodies. 
     
     
         7 . The method of  claim 1 , wherein samples are taken prior to and/or during and/or following therapy for Alzheimer's disease. 
     
     
         8 . The method of  claim 1 , wherein quantifying is performed by one or more methods selected from SELDI (-TOF), MALDI (-TOF), a 1-D gel-based analysis, a 2-D gel-based analysis, Mass spec (MS), reverse phase liquid chromatography, size permeation (gel filtration), ion exchange, affinity HPLC, UPLC, or other LC or LC-MS-based technique.