New Therapeutic Strategy—Mimic the ApoE Christchurch Mutation?

People with ApoE3 Christchurch variant stave off even autosomal-dominant Alzheimer’s disease by keeping neurofibrillary tangles at bay. Could people born without this protective mutation reap its benefits? Researchers led by Joseph Arboleda-Velasquez and Claudia Marino of Massachusetts Eye and Ear in Boston are exploring this question with an antibody that mimics this form of ApoE. In the October 4 Alzheimer’s & Dementia, they reported that the antibody blocked tau hyperphosphorylation, provoked by human ApoE, in the mouse eye and brain. Alzforum wrote about this concept earlier this year (Aug 2023 conference news).

“This study is an important step in leveraging the unique biology of the Christchurch APOE variant to gain a better understanding of how one might try to neutralize an APOE region that affects certain aspects of AD pathophysiology,” wrote David Holtzman and Jason Ulrich at Washington University in St. Louis.

To create Christchurch-mimicking antibodies, co-first authors Marino and Paula Perez-Corredor made peptides corresponding to the Christchurch region in ApoE, i.e., its heparan sulfate proteoglycan binding domain. HSPGs help toxic forms of tau spread between neurons, and scientists think ApoE-HSPG binding might explain the low tangle loads seen in Christchurch carriers (May 2018 news; Stopschinski et al., 2018). After injecting the peptides into mice, one made an antibody, called 7C11, that tightly bound ApoE. This weakened binding between the apolipoprotein and HSPG.

See 7C11 in Action. In the retinas of P301S mice, minimal phospho-tau (red) accumulates (left). ApoE3 injection prompts p-tau aggregation (middle), but 7C11 blocks it (right). [Courtesy of Marino et al., Alzheimer’s & Dementia, 2023.]

Could 7C11 prevent tau pathology in vivo? Marino and Perez-Corredor wanted a quick readout of the antibody’s effect, so they peered into the eyes of P301S mice. They injected human ApoE into the eye to induce tau phosphorylation in the retina, and then looked to see how the antibody influenced this pathology over the next three days. Co-injecting 7C11 reduced the amount of AT8-positive p-tau provoked by ApoE3 by two-thirds (image above).

New Therapeutic Strategy—Mimic the ApoE Christchurch Mutation? An antibody copying the effects of the protective ApoE variant prevents tau hyperphosphorylation in the mouse eye and brain.

The antibody also curbed tau pathology in the brains of 16-month-old APOE4 knock-in mice. Despite having no tau mutations, these mice accumulate phosphorylated tau at this age (Brecht et al., 2004). Injecting 7C11 intraperitoneally into the knock-ins daily for four days halved p-tau396 (image at right).

"Marino et al. provide support for the hypothesis that the protective effects of the APOE3 Christchurch variant against a dominant Alzheimer’s disease mutation is due to reduced interactions of ApoE with HSPGs,” wrote Jacob Raber, Oregon Health and Science University in Portland (comment below).

Will the antibody work in people? 7C11 bound to postmortem middle temporal gyri samples from an APOE3/3 and an APOE4/4 carrier, suggesting it might. Alas, ApoE has proven to be a tough target before, Holtzman and Ulrich note (full comment below).

Arboleda-Velasquez co-founded a Massachusetts-based company called Epoch Biotech, LLC, that plans to test 7C11 in clinical trials. It has not announced when a Phase 1 study will start.—Chelsea Weidman Burke

Comments

  1. The identification of rare variants in APOE that appear to protect against Alzheimer’s disease, such as V236E (Jacksonville) and R136S (Christchurch), present an exciting opportunity to better understand the mechanisms by which APOE may influence different aspects of AD pathology and neurodegeneration. As the authors note, both the Jacksonville and Christchurch variants reduce the affinity of APOE for heparin sulfate proteoglycans (HSPGs), which could indicate a potential role for the APOE-HSPG interaction in AD pathogenesis. The antibodies described in the paper provide an excellent tool for blocking the HPSG binding region on APOE, and the authors report some interesting preliminary effects of the antibody in reducing tau phosphorylation in different experiments.

    Directly translating an effect of an anti-APOE antibody to a therapy may turn out to be quite challenging. For example, our group has developed an APOE antibody (HAE-4) that reduces amyloid plaques, CAA, and amyloid-dependent tau seeding/spreading. This antibody targets a conformation of APOE that is co-deposited in amyloid plaques and CAA. Importantly, it does not bind to native, lipidated APOE particles in the plasma or CNS (Liao et al., 2018; Gratuze et al., 2022; Xiong et al., 2021). Because of this, the half-life of HAE-4 after peripheral injection is similar to that of other IgG’s in mice, about seven days, and because it does not bind lipidated APOE, it does not affect peripheral lipoprotein metabolism. 

    In contrast, we have found that most peripherally administered APOE antibodies recognize lipidated, physiological APOE-containing lipoproteins, and have a very short half-life, in the order of minutes to hours (Liao et al., 2018). Given the abundance of APOE in both the periphery and CNS, achieving a therapeutic level of HSPG-APOE neutralization in the brain could be a very tall order if the antibody used in the study by Marino et al. binds to lipidated APOE. It may not get to its target at a high enough concentration to neutralize it over longer periods of time. As such, it would be interesting to know if the HSPG-blocking APOE antibodies affected peripheral lipoprotein/lipid profiles similarly to the Christchurch variant.

    Nonetheless, this study is an important step in leveraging the unique biology of the Christchurch APOE variant to gain a better understanding of how one might try to neutralize an APOE region that affects certain aspects of AD pathophysiology.

    References:

    Liao F, Li A, Xiong M, Bien-Ly N, Jiang H, Zhang Y, Finn MB, Hoyle R, Keyser J, Lefton KB, Robinson GO, Serrano JR, Silverman AP, Guo JL, Getz J, Henne K, Leyns CE, Gallardo G, Ulrich JD, Sullivan PM, Lerner EP, Hudry E, Sweeney ZK, Dennis MS, Hyman BT, Watts RJ, Holtzman DM. Targeting of nonlipidated, aggregated apoE with antibodies inhibits amyloid accumulation. J Clin Invest. 2018 May 1;128(5):2144-2155. Epub 2018 Mar 30 PubMed.

    Gratuze M, Jiang H, Wang C, Xiong M, Bao X, Holtzman DM. APOE Antibody Inhibits Aβ-Associated Tau Seeding and Spreading in a Mouse Model. Ann Neurol. 2022 Jun;91(6):847-852. Epub 2022 Mar 31 PubMed.

    Xiong M, Jiang H, Serrano JR, Gonzales ER, Wang C, Gratuze M, Hoyle R, Bien-Ly N, Silverman AP, Sullivan PM, Watts RJ, Ulrich JD, Zipfel GJ, Holtzman DM. APOE immunotherapy reduces cerebral amyloid angiopathy and amyloid plaques while improving cerebrovascular function. Sci Transl Med. 2021 Feb 17;13(581) PubMed.

    View all comments by Jason Ulrich View all comments by David Holtzman

  2. The R136S Christchurch mutation is in the domain involved in the interaction between ApoE and heparan sulfate proteoglycans (HSPGs) which binds the low-density lipoprotein (LDL) and LDL receptor-related protein (LRP) receptors. The astrocyte-secreted HSPG called Glypican-4 (GPC-4) binds ApoE4 and mediates its toxicity to propagate tau pathology in the brain. E4-mediated surface trafficking of the APOE receptor LRP 1 through GPC-4 can be a gateway to spreading of tau pathology (Saroja et al., 2022). As previously reported for prion proteins, HSPGs are involved in the uptake of tau and α-synuclein fibrils, causing intracellular aggregation and transcellular aggregate propagation (Holmes et al., 2013).

    Consistent with these data, in this study, Marino et al. provide support for the hypothesis that the protective effect of the APOE3 Christchurch (APOECh) variant against a dominant AD mutation is due to reduced interactions of ApoE with heparan sulfate proteoglycans (HSPGs). Introducing the Christchurch mutation in E4 reduced cytotoxicity in the lactate dehydrogenase assay of SH-SY5Y neuroblastoma cells treated for 24 hours compared to those treated with E4.

    Well-characterized ApoE-binding antibodies that specifically inhibit the interaction of ApoE with HSPGs reduced ApoE-induced tau pathology in the retina of MAPT*P301S mice three days after intravitreal injection of E3. Notably, the paraformaldehyde fixation of the retina was overnight at 4ºC, while typically much shorter fixation times are being used for retina immunohistochemistry to improve the signal-to-noise ratio. Intraperitoneal administration of these well-characterized ApoE-binding antibodies that inhibit the interaction of ApoE with HSPGs also reduced phosphorylation of tau S396 in the brain. Cognitive performance was not addressed in this study but would be expected to be improved with reduced tau pathology.

    While the authors provide evidence that these antibodies, when labeled with Alexa-647, can penetrate the blood-brain barrier, this might not be required to reduce tau pathology. Liver-generated human ApoE does not enter the brain, but murine ApoE and markers of synaptic integrity, neuroinflammation, and insulin signaling are negatively affected in the brains of human liver E4 mice (Giannisis et al., 2022). Comparing human liver E3 with targeted replacement E3 mice, there are model-dependent correlations between plasma ApoE levels and behavioral and cognitive measures, suggesting that a humanized liver might be sufficient to induce mouse behavioral and cognitive phenotypes (Kessler et al., 2023).

    Consistent with a role of the liver in brain phenotypes is the neurodegenerative phenotype described in mice that generate human Aβ only in the liver (Lam et al., 2021), the altered levels of Aβ-degrading enzymes in the livers of AD patients (Maarouf et al., 2018), and the association between altered liver enzymes and AD diagnostic, cognition, neuroimaging, and cerebrospinal fluid biomarkers (Nho et al., 2019). Further, a recent study showed that inhibition of liver enzyme soluble epoxide hydrolase drives a subsequent increase of 14,15-epoxyeicosatrienoic acid in the blood and into the brain, release of ApoE by astrocytes, and activation of microglia that reduces Aβ plaque pathology and improves cognitive function (Wu et al., 2023).

    Alterations in the gut microbiome and involvement of the bidirectional gut-liver-brain axis could be an additional pathway where peripheral antibody treatment can have central effects without antibodies having to penetrate the blood-brain-barrier. The gut microbiome is key in modulating the response of cancer patients to immune activation using checkpoint inhibitor antibodies, for example (for a recent review, see Li et al., 2022).

    Delivery of tripartite motif (TRIM) 11, which is reduced in AD brains, into the brain also protects against tau pathology (Zhang et al., 2023). However, TRIM11 promotes tumor progression and high TRIM11 levels are associated with reduced survival of colon cancer patients and increased resistance to chemotherapy (Noble and Hanger, 2023). HSPGs play important roles in cancer initiation and progression and are targets for cancer therapy (Onyeis et al., 2020). ApoE isoforms may also be important in cancer. E4 prolongs survival in melanoma patients, while E2 associates with shorter survival (Ostndorf et al., 2020). APOE genotype also modulates aggressive behavior in prostate cancer cells by modulating cholesterol metabolism (Ifere et al., 2013). Therefore, an important question to address is whether peripherally reducing β-HSPG binding affects cancer risk or tumor progression in addition to reducing tau pathology in the brain.

    References:

    Saroja SR, Gorbachev K, Julia T, Goate AM, Pereira AC. Astrocyte-secreted glypican-4 drives APOE4-dependent tau hyperphosphorylation. Proc Natl Acad Sci U S A. 2022 Aug 23;119(34):e2108870119. Epub 2022 Aug 15 PubMed.

    Holmes BB, DeVos SL, Kfoury N, Li M, Jacks R, Yanamandra K, Ouidja MO, Brodsky FM, Marasa J, Bagchi DP, Kotzbauer PT, Miller TM, Papy-Garcia D, Diamond MI. Heparan sulfate proteoglycans mediate internalization and propagation of specific proteopathic seeds. Proc Natl Acad Sci U S A. 2013 Aug 13;110(33):E3138-47. Epub 2013 Jul 29 PubMed.

    Giannisis A, Patra K, Edlund AK, Nieto LA, Benedicto-Gras J, Moussaud S, de la Rosa A, Twohig D, Bengtsson T, Fu Y, Bu G, Bial G, Foquet L, Hammarstedt C, Strom S, Kannisto K, Raber J, Ellis E, Nielsen HM. Brain integrity is altered by hepatic APOE ε4 in humanized-liver mice. Mol Psychiatry. 2022 Apr 13; PubMed.

    Kessler K, Giannisis A, Bial G, Foquet L, Nielsen HM, Raber J. Behavioral and cognitive performance of humanized APOEε3/ε3 liver mice in relation to plasma apolipoprotein E levels. Sci Rep. 2023 Jan 31;13(1):1728. PubMed.

    Lam V, Takechi R, Hackett MJ, Francis R, Bynevelt M, Celliers LM, Nesbit M, Mamsa S, Arfuso F, Das S, Koentgen F, Hagan M, Codd L, Richardson K, O'Mara B, Scharli RK, Morandeau L, Gauntlett J, Leatherday C, Boucek J, Mamo JC. Synthesis of human amyloid restricted to liver results in an Alzheimer disease-like neurodegenerative phenotype. PLoS Biol. 2021 Sep;19(9):e3001358. Epub 2021 Sep 14 PubMed.

    Maarouf CL, Walker JE, Sue LI, Dugger BN, Beach TG, Serrano GE. Impaired hepatic amyloid-beta degradation in Alzheimer's disease. PLoS One. 2018;13(9):e0203659. Epub 2018 Sep 7 PubMed.

    Nho K, Kueider-Paisley A, Ahmad S, MahmoudianDehkordi S, Arnold M, Risacher SL, Louie G, Blach C, Baillie R, Han X, Kastenmüller G, Trojanowski JQ, Shaw LM, Weiner MW, Doraiswamy PM, van Duijn C, Saykin AJ, Kaddurah-Daouk R, Alzheimer’s Disease Neuroimaging Initiative and the Alzheimer Disease Metabolomics Consortium. Association of Altered Liver Enzymes With Alzheimer Disease Diagnosis, Cognition, Neuroimaging Measures, and Cerebrospinal Fluid Biomarkers. JAMA Netw Open. 2019 Jul 3;2(7):e197978. PubMed.

    Wu Y, Dong JH, Dai YF, Zhu MZ, Wang MY, Zhang Y, Pan YD, Yuan XR, Guo ZX, Wang CX, Li YQ, Zhu XH. Hepatic soluble epoxide hydrolase activity regulates cerebral Aβ metabolism and the pathogenesis of Alzheimer's disease in mice. Neuron. 2023 Sep 20;111(18):2847-2862.e10. Epub 2023 Jul 3 PubMed.

    Li X, Zhang S, Guo G, Han J, Yu J. Gut microbiome in modulating immune checkpoint inhibitors. EBioMedicine. 2022 Aug;82:104163. Epub 2022 Jul 15 PubMed.

    Zhang ZY, Harischandra DS, Wang R, Ghaisas S, Zhao JY, McMonagle TP, Zhu G, Lacuarta KD, Song J, Trojanowski JQ, Xu H, Lee VM, Yang X. TRIM11 protects against tauopathies and is down-regulated in Alzheimer's disease. Science. 2023 Jul 28;381(6656):eadd6696. PubMed.

    Noble W, Hanger DP. Trimming away tau in neurodegeneration. Science. 2023 Jul 28;381(6656):377-378. Epub 2023 Jul 27 PubMed.

    Onyeisi JO, Ferreira BZ, Nader HB, Lopes CC. Heparan sulfate proteoglycans as targets for cancer therapy: a review. Cancer Biol Ther. 2020 Dec 1;21(12):1087-1094. Epub 2020 Nov 12 PubMed.

    Ostendorf BN, Bilanovic J, Adaku N, Tafreshian KN, Tavora B, Vaughan RD, Tavazoie SF. Common germline variants of the human APOE gene modulate melanoma progression and survival. Nat Med. 2020 Jul;26(7):1048-1053. Epub 2020 May 25 PubMed.

    Ifere GO, Desmond R, Demark-Wahnefried W, Nagy TR. Apolipoprotein E gene polymorphism influences aggressive behavior in prostate cancer cells by deregulating cholesterol homeostasis. Int J Oncol. 2013 Oct;43(4):1002-10. Epub 2013 Aug 7 PubMed.

    View all comments by Jacob Raber

  3. This paper provides more evidence that interactions between APOE-HSPG may be involved in AD. Additionally, neurons secrete SPOCK1, which encodes testican1, which is a heparan sulfate and chondroitin sulfate proteoglycan. SPOCK1 is essential in forming and maintaining the blood brain barrier (BBB).

    References:

    O'Brown NM, Patel NB, Hartmann U, Klein AM, Gu C, Megason SG. The secreted neuronal signal Spock1 promotes blood-brain barrier development. Dev Cell. 2023 Sep 11;58(17):1534-1547.e6. Epub 2023 Jul 11 PubMed.

    View all comments by Charles Stromeyer

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References

Mutations Citations

  1. APOE R154S (Christchurch)

News Citations

  1. Does One Copy of the Christchurch ApoE Variant Slow Alzheimer’s?
  2. To Deliver Itself From Cell to Cell, Phospho-Tau Uses UPS

Research Models Citations

  1. Tau P301S (Line PS19)
  2. APOE4 Targeted Replacement

Paper Citations

  1. Stopschinski BE, Holmes BB, Miller GM, Manon VA, Vaquer-Alicea J, Prueitt WL, Hsieh-Wilson LC, Diamond MI. Specific glycosaminoglycan chain length and sulfation patterns are required for cell uptake of tau versus α-synuclein and β-amyloid aggregates. J Biol Chem. 2018 Jul 6;293(27):10826-10840. Epub 2018 May 11 PubMed.
  2. Brecht WJ, Harris FM, Chang S, Tesseur I, Yu GQ, Xu Q, Dee Fish J, Wyss-Coray T, Buttini M, Mucke L, Mahley RW, Huang Y. Neuron-specific apolipoprotein e4 proteolysis is associated with increased tau phosphorylation in brains of transgenic mice. J Neurosci. 2004 Mar 10;24(10):2527-34. PubMed.

Further Reading

Primary Papers

  1. Marino C, Perez-Corredor P, O'Hare M, Heuer A, Chmielewska N, Gordon H, Chandrahas AS, Gonzalez-Buendia L, Delgado-Tirado S, Doan TH, Vanderleest TE, Arevalo-Alquichire S, Obar RA, Ortiz-Cordero C, Villegas A, Sepulveda-Falla D, Kim LA, Lopera F, Mahley R, Huang Y, Quiroz YT, Arboleda-Velasquez JF. APOE Christchurch-mimetic therapeutic antibody reduces APOE-mediated toxicity and tau phosphorylation. Alzheimers Dement. 2024 Feb;20(2):819-836. Epub 2023 Oct 4 PubMed.

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