Quantification of axonal damage in traumatic brain injury : Affinity purification and characterization of cerebrospinal fluid tau proteins

• Published in: Journal of neurochemistry Vol. 72; no. 2; pp. 741 - 750
• Main Authors: ZEMLAN, F. P, ROSENBERG, W. S, LUEBBE, P. A, CAMPBELL, T. A, DEAN, G. E, WEINER, N. E, COHEN, J. A, RUDICK, R. A, WOO, D
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell 01-02-1999
• Subjects: Alzheimer Disease - cerebrospinal fluid; Animals; Antibodies, Monoclonal; Axons - pathology; Biological and medical sciences; Brain Injuries - cerebrospinal fluid; Brain Injuries - pathology; Chromatography, Affinity; Enzyme-Linked Immunosorbent Assay - methods; Female; Humans; Injuries of the nervous system and the skull. Diseases due to physical agents; Medical sciences; Mice; Mice, Inbred BALB C; Microtubules - chemistry; Neuroprotective Agents - cerebrospinal fluid; Neuroprotective Agents - isolation & purification; Recombinant Proteins - immunology; tau Proteins - cerebrospinal fluid; tau Proteins - immunology; tau Proteins - isolation & purification; Traumas. Diseases due to physical agents; Human; Purification; Pathophysiology; Axon; Neuroprotective agent; Cerebrospinal fluid; Trauma; Cerebral disorder; Characterization; Tau protein; Central nervous system disease; Parasympathetic nervous system; Brain (vertebrata)
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.1999.0720741.x

Diffuse axonal injury is a primary feature of head trauma and is one of the most frequent causes of mortality and morbidity. Diffuse axonal injury is microscopic in nature and difficult or impossible to detect with imaging techniques. The objective of the present study was to determine whether axonal injury in head trauma patients could be quantified by measuring levels of CSF tau proteins. Tau proteins are structural microtubule binding proteins primarily localized in the axonal compartment of neurons. Monoclonal antibodies recognizing the form of tau found in the CSF of head trauma patients were developed by differential CSF hybridoma screening using CSF from head trauma and control patients. Clones positive for head trauma CSF tau proteins were used to characterize this form of tau and for ELISA development. Using the developed ELISA, CSF tau levels were elevated >1,000-fold in head trauma patients (mean, 1,519 ng/ml of CSF) when compared with patients with multiple sclerosis (mean, 0.014 ng/ml of CSF; p < 0.001), normal pressure hydrocephalus (nondetectable CSF tau), neurologic controls (mean, 0.031 ng/ml of CSF; p < 0.001), or nonneurologic controls (nondetectable CSF tau; p < 0.001). In head trauma, a relationship between clinical improvement and decreased CSF tau levels was observed. These data suggest that CSF tau levels may prove a clinically useful assay for quantifying the axonal injury associated with head trauma and monitoring efficacy of neuroprotective agents. Affinity purification of CSF tau from head trauma patients indicated a uniform cleavage of approximately 18 kDa from all six tau isoforms, reducing their apparent molecular sizes to 30-50 kDa. These cleaved forms of CSF tau consisted of the interior portion of the tau sequence, including the microtubule binding domain, as judged by cyanogen bromide digestion. Consistent with these data, CSF cleaved tau bound taxol-polymerized microtubules, indicating a functionally intact microtubule binding domain. Furthermore, epitope mapping studies suggested that CSF cleaved tau proteins consist of the interior portion of the tau sequence with cleavage at both N and C terminals.