Purified antigen for Alzheimer's disease and methods of obtaining and using same

A protein preparation consisting essentially of an antigen, which preparation is a diagnostic marker of Alzheimer's disease, wherein said antigen comprises a major polypeptide species that:

• (a) has an isoelectric point of about 6 in reduced or non-reduced form;
• (b) binds to an affi-Blue column;
• (c) is at least 50% soluble in a solution of 0.01 M sodium phosphate, 0.14 M sodium chloride and 1 mM phenyl methyl sulfonyl fluoride at pH 6.8, and precipitates in 50% saturated ammonium sulfate at 4° C.;
• (d) is immunologically reactive with a monoclonal antibody produced by the hybridoma cell line identified as ATCC No. HB9205;
• and
• (e) is substantially free of immunoglobulin G.

A method of increasing the ability of an Alzheimer's disease antigen to detect autoantibodies that are present in Alzheimer's disease, wherein said antigen is tau isolated from various species including human, or is recombinant human tau, or is phosphorylated recombinant human tau or isolated tau, and said method comprises:

• (a) treating said antigen with hypericin, or calphostin C or the like;
• or
• (b) treating said antigen with free fatty acids;
• or
• (c) treating said antigen with hydroxynonenal or other advanced glycation endproducts;
• or
• (d) combinations of the above.

A method of obtaining an antibody that is immunologically reactive with an antibody directed against A68 antigen, said method comprising:

• (a) obtaining sera from individuals having high titers of anti-A68 autoantibodies, combining to create a pool, and isolating antibodies from said pool, or, obtaining isolated monoclonal antibodies to A68 antigen;
• (b) immunizing mice with said isolated antibodies;
• (c) obtaining serum from said mice;
• and
• (d) testing said serum to identify mice having high levels of antibodies that are immunologically reactive with a monoclonal antibody or serum autoantibodies directed against A68 antigen.