Research ArticleAlzheimer’s Disease

APOE immunotherapy reduces cerebral amyloid angiopathy and amyloid plaques while improving cerebrovascular function

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Science Translational Medicine  17 Feb 2021:
Vol. 13, Issue 581, eabd7522
DOI: 10.1126/scitranslmed.abd7522

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Controlling amyloid in brain and vasculature

The genetic variant ε4 of the gene APOE (APOE4) is associated with increased risk of developing Alzheimer’s disease (AD). In AD, Aβ forms deposits in the brain parenchyma (amyloid plaques) and in the cerebral vasculature [cerebral amyloid angiopathy (CAA)]. Immunotherapy targeting human APOE reduced brain Aβ deposits in mice. Now, Xiong et al. used a mouse model with both amyloid plaques and CAA and evaluated the effects of the anti-human APOE antibody HAE-4. The treatment reduced both parenchymal Aβ plaques and CAA without vascular complications, whereas an antibody targeting Aβ exacerbated CAA-related microhemorrhages. The results suggest that HAE-4 may provide therapeutic effects on amyloid removal in AD while protecting the cerebrovasculature.

Abstract

The ε4 allele of the apolipoprotein E (APOE) gene is the strongest genetic risk factor for late-onset Alzheimer’s disease (AD) and greatly influences the development of amyloid-β (Aβ) pathology. Our current study investigated the potential therapeutic effects of the anti-human APOE antibody HAE-4, which selectively recognizes human APOE that is co-deposited with Aβ in cerebral amyloid angiopathy (CAA) and parenchymal amyloid pathology. In addition, we tested whether HAE-4 provoked brain hemorrhages, a component of amyloid-related imaging abnormalities (ARIA). ARIA is an adverse effect secondary to treatment with anti–Aβ antibodies that can occur in blood vessels with CAA. We used 5XFAD mice expressing human APOE4+/+ (5XE4) that have prominent CAA and parenchymal plaque pathology to assess the efficacy of HAE-4 compared to an Aβ antibody that removes parenchymal Aβ but increases ARIA in humans. In chronically treated 5XE4 mice, HAE-4 reduced Aβ deposition including CAA compared to a control antibody, whereas the anti–Aβ antibody had no effect on CAA. Furthermore, the anti–Aβ antibody exacerbated microhemorrhage severity, which highly correlated with reactive astrocytes surrounding CAA. In contrast, HAE-4 did not stimulate microhemorrhages and instead rescued CAA-induced cerebrovascular dysfunction in leptomeningeal arteries in vivo. HAE-4 not only reduced amyloid but also dampened reactive microglial, astrocytic, and proinflammatory-associated genes in the cortex. These results suggest that targeting APOE in the core of both CAA and plaques could ameliorate amyloid pathology while protecting cerebrovascular integrity and function.

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