Epitope: Tau phosphorylated at serine-202
Immunogen: Paired-helical filament tau extracted from AD brains
Clonality: Monoclonal
Isotype: IgG1
Host: Mouse
Reactivity: Human; Mouse; Non human primates; Feline; Hamster

Overview

This monoclonal antibody, generated against paired helical filaments (PHFs) isolated from Alzheimer’s brains, recognizes tau phosphorylated at serine 202.

CP-13 labels neurofibrillary tangles (NFTs), pretangles, neuropil threads, and dystrophic neurites in the brains of Alzheimer’s cases, as well as neurons and astrocytes in other neurodegenerative tauopathies. Limited data suggest that CP-13 immunoreactivity is minimal in normal human brains. The antibody also labels neurons in rodent models of tauopathy, with some immunoreactivity detected in the brains of wild-type animals.

CP-13 labels neuronal filaments. Left, Immunogold-labeled PHFs from a neuron in the prefrontal cortex of an aged chimpanzee. Scale bar, 200 nm. Right, Immunogold-labeled filaments in a neuron in a JNPL3 mouse. Scale bar, 100 nm. [Left, from Rosen et al., 2008. © 2008 Wiley-Liss, Inc. Right, from Lewis et al., 2000. © 2000 Nature America.]

CP-13 immunotherapy has been tested in disease models, with limited success. Passive immunization of JNPL3 mice, which express human tau with the P301L mutation, prevented the appearance of pathological forms of tau, although this effect depended upon the brain region and tau fraction examined (d’Abramo et al., 2015). Intrabodies derived from CP-13 slowed the development of tau pathology and paralysis in JNPL3 mice, when expressed from AAV vectors injected into the spinal cords of these animals (Goodwin et al., 2021). The intrabodies—this time injected intracerebroventricularly—also slowed the development of tau pathology in rTg4510 mice, another transgenic line that expresses human tauP301L. Passive immunization of zQ175 mice, a knockin model of Huntington’s disease, led to improvements on some measures of motor and cognitive function but not others (Alpaugh et al., 2022).

Generation and epitope mapping

The CP-13 antibody was generated in the laboratory of the late Dr. Peter Davies, following immunization of mice with PHF tau isolated from Alzheimer’s brains (Xia et al., 2020, citing personal communication from Dr. Davies).

Studies from the Davies laboratory reported the CP-13 epitope as tau phosphorylated at serine 202 (Jicha et al., 1999; Weaver et al., 2000; Espinoza et al., 2008) but did not describe their epitope-mapping experiments. While papers from the late 1990s frequently have been cited—incorrectly—as sources for the mapping of the CP-13 epitope, it was not until 2020 that epitope-mapping data actually were published. Giasson and colleagues (Xia et al., 2020) used CP-13 as a detection antibody in a direct ELISA in which the targets were synthetic phospho-peptides duplicating sequences within amino acids 193 through 213 of the 441-amino acid isoform of tau. Among this set of peptides, CP-13 recognized only those in which the serine corresponding to residue 202 was phosphorylated.

Characterization of the phospho-epitope recognized by CP-13. In a direct ELISA, wells were coated with synthetic phospho-peptides corresponding to sequences within amino acids 193 through 213 of tau. Left, plates probed with CP-13. CP-13 reacts only with peptides mimicking tau phosphorylated at serine 202. Right, control plates exposed to buffer (PBS) without antibody. [From Xia et al., 2020, Figure 4A,C; licensed under Creative Commons BY 4.0.]

Specificity

CP-13 immunoreactivity has been observed in the brains of subjects with Alzheimer's disease and other tauopathies, but data from normal brains are limited. In dot blots of homogenates of middle temporal gyrus, minimal CP-13 immunoreactivity was seen in controls (Braak stages 0-3) compared with AD (Braak stages 4-6) cases, and the level of immunoreactivity correlated with Braak stage (Koss et al., 2016). Using immunohistochemical techniques, CP-13-immunoreactive neurons were found in the entorhinal cortices of elderly subjects characterized as Braak stages 1 and 2, who did not have a clinically diagnosed neurological disorder at the time of death (Llamas-Rodríguez et al., 2022). CP-13 detected proteins on western blots of biopsy specimens from the temporal cortices of patients undergoing surgery for epilepsy—although this tissue was described as apparently normal, it did come from diseased brains (Jicha et al., 1999). CP-13-immunoreactive bands were also seen in samples from fetal brains on these same western blots.

CP-13 reacts with proteins in Alzheimer’s brains but not controls. CP-13 immunoreactivity in lysates of temporal cortices from subjects with neuropathologically confirmed Alzheimer’s disease (Braak stages 4-6) and controls (Braak stages 0-3). i) Sample blot.  ii-iv) Quantification of dot blot signals. [From Koss et al., 2016, Figure 2.c; licensed under Creative Commons BY 4.0.]

CP-13 staining in entorhinal cortices of neurologic controls. Cases were Braak stages 1 and 2, ranged in age from 59 to 84 years, and did not show symptoms of neurological disease at the time of death. [Llamas-Rodríguez et al., 2022, Figure 1; licensed under Creative Commons BY 4.0. © 2022 The authors.]

CP-13 immunostaining has been reported in several neurodegenerative diseases in addition to AD. In Alzheimer’s brains, CP-I3 labels neurofibrillary tangles (NFTs), pretangles, neuropil threads, and dystrophic neurites (Espinoza et al., 2008; Arena et al., 2020; Xia et al., 2020). CP-13 labeled both NFTs and astrocytes in cases of chronic traumatic encephalopathy (Arena et al., 2020; Mantyh et al., 2020). In corticobasal degeneration, CP-13 labeled astrocytes (Arena et al., 2020; Xia et al., 2020). CP-13-immunoreactive astrocytes were also seen in progressive supranuclear palsy (Espinoza et al., 2008; Arena et al., 2020; Xia et al., 2020), as were CP-13-positive NFTs (Espinoza et al., 2008) and neuronal globose tangles (Xia et al., 2020). In Pick’s disease, a form of frontotemporal dementia, CP-13 labeled spherical tau inclusions called Pick bodies (Espinoza et al., 2008; Arena et al., 2020), as well as astrocytes (Arena et al., 2020). CP-13 also labeled Lewy bodies in the brains of subjects characterized as having diffuse Lewy body disease with a range of Alzheimer-like pathology (Ishizawa et al., 2003).

CP-13 labels intracellular inclusions in neurodegenerative tauopathies. Upper row, neuronal labeling. Lower row, astrocytic labeling. AD, Alzheimer’s disease. CTE, chronic traumatic encephalopathy. PiD, Pick’s disease. PART, primary age-related tauopathy. ARTAG, ageing-related tau astrogliopathy. PSP, progressive supranuclear palsy. CBD, corticobasal degeneration. [Adapted from Arena et al., 2020. © 2020 The authors.]

CP-13 immunoreactivity is seen in transgenic mouse models of tauopathy, but, generally, little or no immunoreactivity is apparent in the brains of non-transgenic mice (Lewis et al., 2000; Ramsden et al., 2005; Acker et al., 2013; Ward et al., 2014; Xu et al., 2014). An early study showed that CP-13 detected bands in extracts of the brains of fetal and adult wild-type mice, but no samples from transgenic animals were included for comparison (Jicha et al., 1999). To date, published immunohistochemical results indicate that the CP-13 immunoreactivity in transgenic mice is neuronal (Lewis et al., 2000; Ramsden et al., 2005; McKee et al., 2008; Xia et al., 2020).

CP-13 immunoreactivity in the brains of mouse models of tauopathy. A) Upper, western blot of mouse brain extracts, probed with CP-13. Lower, the same blot shown above was stripped and re-probed with an antibody against GAPDH, as a loading control. nt, non-transgenic; tg, rTg4510, which express human tau with the P301L mutation linked to frontotemporal dementia. Ages of the mice are shown above the blot. B) Immunohistochemical staining of the hippocampi of an rTg4510 mouse (top) and an age-matched non-transgenic control (bottom). Panels on the right are shown at 2.5x the magnification of panels on the left. C) Immunohistochemical staining of the hippocampi of hTau.P301S transgenic mice, which express human tau with the P301S mutation (also linked to frontotemporal dementia), compared with non-transgenic (Wildtype) mice. Note that little or no CP-13 immunoreactivity is found in non-transgenic animals. [A) From Ward et al., 2014. Neurobiology of Disease © 2014 Elsevier Inc. B) From Ramsden et al., 2005, Journal of Neuroscience. © 2005 Society for Neuroscience. Original labeling masked by Alzforum curator. C) From Xu et al., 2014. Neuropathology and Applied Neurobiology © 2014 British Neuropathological Society.]

Species

CP-13 immunoreactivity has been reported in Syrian hamsters (Härtig et al., 2005), an aged cat (Flock et al., 2020), and an aged chimpanzee (Rosen et al., 2008), in addition to the brains of humans and mice.

Validation

CP-13 has been tested against brain extracts from tau knockouts in western blot (Petry et al., 2014; Wobst et al., 2017) and ELISA (Acker et al., 2013) applications, to assess the selectivity of the antibody for tau versus other proteins. In each study, CP-13 failed to detect any proteins in the knockout samples.

Validation of CP-13. A) ELISA of brain extracts from wild-type mice, transgenic mice that overexpress wild-type human tau in the absence of mouse tau (htau), transgenic mice that express human tau with the P301L mutation linked to frontotemporal dementia (P301L), and Mapt knockout mice. B) CP-13 does not bind any protein in the brains of tau knockout (KO) mice and displays elevated signals in the brains of mice expected to have increased levels of hyperphosphorylated tau—transgenic mice that express human amyloid precursor protein, presenilin-1, and tau with disease-linked mutations (3xTg) and hypothermic wild-type mice (Hypo). Blot probed with CP-13 followed by a secondary antibody that recognizes non-denatured mouse IgG. [A) Adapted from Acker et al., 2013. Neurobiology of Aging © 2012 Elsevier Inc. B) From Petry et al., 2014; Figure 3.E2 CP-13-TB, labels added; licensed under Creative Commons BY 4.0.]

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References

Research Models Citations

1. JNPL3(P301L)
2. rTg(tauP301L)4510
3. hTau.P301S
4. htau
5. 3xTg

Mutations Citations

1. MAPT P301L
2. MAPT P301S

Paper Citations

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16. Acker CM, Forest SK, Zinkowski R, Davies P, d'Abramo C. Sensitive quantitative assays for tau and phospho-tau in transgenic mouse models. Neurobiol Aging. 2013 Jan;34(1):338-50. Epub 2012 Jun 21 PubMed.
17. Ward SM, Himmelstein DS, Ren Y, Fu Y, Yu XW, Roberts K, Binder LI, Sahara N. TOC1: a valuable tool in assessing disease progression in the rTg4510 mouse model of tauopathy. Neurobiol Dis. 2014 Jul;67:37-48. Epub 2014 Mar 12 PubMed.
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20. Härtig W, Oklejewicz M, Strijkstra AM, Boerema AS, Stieler J, Arendt T. Phosphorylation of the tau protein sequence 199-205 in the hippocampal CA3 region of Syrian hamsters in adulthood and during aging. Brain Res. 2005 Sep 14;1056(1):100-4. PubMed.
21. Fiock KL, Smith JD, Crary JF, Hefti MM. β-amyloid and tau pathology in the aging feline brain. J Comp Neurol. 2020 Jan 1;528(1):108-113. Epub 2019 Jul 12 PubMed.
22. Petry FR, Pelletier J, Bretteville A, Morin F, Calon F, Hébert SS, Whittington RA, Planel E. Specificity of anti-tau antibodies when analyzing mice models of Alzheimer's disease: problems and solutions. PLoS One. 2014;9(5):e94251. Epub 2014 May 2 PubMed.
23. Wobst HJ, Denk F, Oliver PL, Livieratos A, Taylor TN, Knudsen MH, Bengoa-Vergniory N, Bannerman D, Wade-Martins R. Increased 4R tau expression and behavioural changes in a novel MAPT-N296H genomic mouse model of tauopathy. Sci Rep. 2017 Feb 24;7:43198. PubMed.

External Citations

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Further Reading

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