Tau ELISA Kits

Tau is a microtubule-associated protein expressed primarily in the central nervous system, where it regulates the stability of microtubules. It is a major component of neurofibrillary tangles (NFTs) observed in the neurons of Alzheimer’s disease (AD) patients. Furthermore, there is a correlation between tau accumulation in the brain and the severity of cognitive impairment¹⁾, suggesting that tau is closely involved in the onset of AD. It should be noted that NFTs characterized by tau accumulation are not exclusive to AD; they are also observed in Pick's disease, progressive supranuclear palsy, corticobasal degeneration, and other conditions, which are collectively referred to as tauopathies.

Total tau levels in cerebrospinal fluid (CSF) are known to increase in AD patients, and elevated levels are believed to reflect the extent of neuronal damage and neurodegeneration^2-3). The reason for the increase in tau in CSF remains unclear; however, it is hypothesized that tau may be released extracellularly as a result of cell death or actively secreted by neurons.

Tau in NFTs is known to undergo excessive phosphorylation. Phosphorylated tau in CSF is considered a biomarker for AD, with pTau T181—tau phosphorylated at the 181st threonine residue—recognized, in particular, as a specific biomarker for the disease⁴⁾. Recent studies have shown that pTau T181 in CSF reflects the accumulation of Aβ in the brain rather than tau accumulation⁵⁾.

The Tau ELISA Kit Wako is designed to measure total tau in human CSF. It uses two types of antibodies: one that recognizes the middle region of the tau protein and another that recognizes the C-terminus, allowing for the detection of all tau, regardless of its phosphorylation state.

Kit Performance

Assay target	Total Tau
Calibration curve range	4.10-1,000 pg/mL
Analysis sample	Human CSF
Sample volume	10 μL (50 μL recommended)
Measurement duration	Approx. 3 hours
Detection method	Luminescence (A plate reader for luminescence measurement is required)

Assay Principle

Data

Measurement in Human CSF

CSF from non-dementia patients (Control), patients with MCI and AD patients (AD) was analyzed using this product and another commercially available product.

[Result]
An increase in total tau levels was confirmed in AD and MCI patients compared to the control group.

Correlation Data with Cognitive Function Test (MMSE Score)

The correlation between the concentration of total tau in CSF, as measured by this product, and the MMSE scores of the patients was measured.

MMSE Score
≦ 23 : Dementia suspected
24-27 : MCI suspected
28-30 : Normal

[Result]
A negative correlation was observed between tau concentration and MMSE scores, with this product showing a stronger correlation compared to another commercially available product.

The Phosphorylated Tau T181 ELISA Kit Wako is designed to measure pTau T181 in human CSF. By using an anti-pTau T181 antibody as the capture antibody, this kit specifically measures pTau T181.

Kit Performance

Assay target	Phosphorylated Tau T181
Calibration curve range	4.40-500 pg/mL
Analysis sample	Human CSF (no used for serum and plasma)
Sample volume	20 μL
Measurement duration	Approx. 20 hours
Detection method	Luminescence (A plate reader for luminescence measurement is required)

Assay Principle

Data

Measurement in Human CSF

CSF from non-dementia patients (Control), patients with MCI and AD patients (AD) was analyzed using this product and another commercially available product.

[Result]
An increase in total tau levels was confirmed in AD and MCI patients compared to the Control group.

Correlation Data with Cognitive Function Test (MMSE Score)

The correlation between the concentration of pTau T181 in CSF, as measured by this product,and the MMSE scores of the patients were measured.

MMSE Score
≦ 23 : Dementia suspected
24-27 : MCI suspected
28-30 : Normal

[Result]
A negative correlation was observed between the concentration of pTau T181 and MMSE scores.

1. Nelson, P. T. et al.: J. Neuropathol. Exp. Neurol., 71(5), 362(2012).
   Correlation of Alzheimer disease neuropathologic changes with cognitive status: a review of the literature
2. Arai, H. et al.: Ann. Neurol., 38(4), 649(1995).
   Tau in cerebrospinal fluid: a potential diagnostic marker in Alzheimer's disease
3. Blennow, K. and Hampel, H.: Lancet Neurol., 2(10), 605(2003).
   CSF markers for incipient Alzheimer's disease
4. Schoonenboom, N. S. et al.: Neurology, 78(1), 47(2012).
   Cerebrospinal fluid markers for differential dementia diagnosis in a large memory clinic cohort
5. Therriault, J. et al.: JAMA Neurol., 80(2), 188(2023).
   Association of Phosphorylated Tau Biomarkers With Amyloid Positron Emission Tomography vs Tau Positron Emission Tomography