title: Characterization of novel CSF Tau and ptau biomarkers for Alzheimer's disease.
abstract: Cerebral spinal fluid (CSF) Aβ42, tau and p181tau are widely accepted biomarkers of Alzheimer's disease (AD). Numerous studies show that CSF tau and p181tau levels are elevated in mild-to-moderate AD compared to age-matched controls. In addition, these increases might predict preclinical AD in cognitively normal elderly. Despite their importance as biomarkers, the molecular nature of CSF tau and ptau is not known. In the current study, reverse-phase high performance liquid chromatography was used to enrich and concentrate tau prior to western-blot analysis. Multiple N-terminal and mid-domain fragments of tau were detected in pooled CSF with apparent sizes ranging from <20 kDa to ~40 kDa. The pattern of tau fragments in AD and control samples were similar. In contrast, full-length tau and C-terminal-containing fragments were not detected. To quantify levels, five tau ELISAs and three ptau ELISAs were developed to detect different overlapping regions of the protein. The discriminatory potential of each assay was determined using 20 AD and 20 age-matched control CSF samples. Of the tau ELISAs, the two assays specific for tau containing N-terminal sequences, amino acids 9-198 (numbering based on tau 441) and 9-163, exhibited the most significant differences between AD and control samples. In contrast, CSF tau was not detected with an ELISA specific for a more C-terminal region (amino acids 159-335). Significant discrimination was also observed with ptau assays measuring amino acids 159-p181 and 159-p231. Interestingly, the discriminatory potential of p181 was reduced when measured in the context of tau species containing amino acids 9-p181. Taken together, these results demonstrate that tau in CSF occurs as a series of fragments and that discrimination of AD from control is dependent on the subset of tau species measured. These assays provide novel tools to investigate CSF tau and ptau as biomarkers for other neurodegenerative diseases.
authors.affiliation: Research and Development, Bristol-Myers Squibb, Wallingford, Connecticut, United States of America.
authors.forename: Jere E
authors.initials: JE
authors.lastname: Meredith
authors.forename: Sethu
authors.initials: S
authors.lastname: Sankaranarayanan
authors.forename: Valerie
authors.initials: V
authors.lastname: Guss
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Lanzetti
authors.forename: Flora
authors.initials: F
authors.lastname: Berisha
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Neely
authors.forename: J Randall
authors.initials: JR
authors.lastname: Slemmon
authors.forename: Erik
authors.initials: E
authors.lastname: Portelius
authors.forename: Henrik
authors.initials: H
authors.lastname: Zetterberg
authors.forename: Kaj
authors.initials: K
authors.lastname: Blennow
authors.forename: Holly
authors.initials: H
authors.lastname: Soares
authors.forename: Michael
authors.initials: M
authors.lastname: Ahlijanian
authors.forename: Charles F
authors.initials: CF
authors.lastname: Albright
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid* / Q000175:diagnosis; D015415:Biomarkers / Q000134:cerebrospinal fluid*; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D010446:Peptide Fragments / Q000134:cerebrospinal fluid* / Q000378:metabolism; D010766:Phosphorylation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016875:tau Proteins / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000378:metabolism
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; D016875:tau Proteins