HAE-4 reduced both small and large parenchymal A plaques (Fig

HAE-4 reduced both small and large parenchymal A plaques (Fig. strongest genetic risk factor for late-onset AD and exacerbates the development of A pathology through several mechanisms, including affecting A aggregation and clearance (15, 16). Previously, we exhibited that passive immunotherapy targeting mouse APOE PTP1B-IN-3 or human APOE4 reduced A pathology in mice with parenchymal amyloidosis (17C19). Specifically, our anti-human APOE antibody (HAE-4) recognizes poorly-lipidated human APOE only present in amyloid plaques (19). To recapitulate both the vascular and parenchymal A pathology found in AD human brains, we utilized an animal model that deposits A mostly in the form of CAA but also in the brain parenchyma. Our goal was to determine if HAE-4 treatment could decrease CAA pathology and subsequently improve PTP1B-IN-3 vessel function without eliciting adverse effects. We compared the treatment effects of HAE-4 against chimeric Aducanumab (chi-Adu), a monoclonal antibody that has shown the ability to remove plaques by binding oligomeric/fibrillar A and induced ARIA in clinical trials (9). We also investigated the mechanisms of action of an APOE antibody and an A antibody, which are largely unknown particularly in the context of CAA. Results Anti-human APOE antibody HAE-4 reduces CAA and parenchymal A plaques First, we validated the efficacy of chi-Adu made up of the human variable heavy and light chain sequences of Aducanumab and a mouse IgG2ab Fc domain name. Chi-Adu significantly reduced A plaques compared to control IgG in 3.5-month-old 5XFAD (line 6799) mice, which develop aggressive A parenchymal plaques beginning at 2-months-of-age (Fig. S1A: < 0.0001; Fig. S1B: < 0.001). For all those further experiments, we used 5XFAD (line 7031) transgenic mice expressing human < 0.05) and fibrillar (Thioflavin-S, ThioS+; Fig. 1FCI, < 0.05) parenchymal and vascular plaques compared to control IgG. HAE-4 reduced both small and large parenchymal A plaques (Fig. S2, < 0.05). There were no sex-dependent differences in A plaque load in response to antibody administrations (Fig. S3ACF), but there was a significant treatment effect (Fig. S3ACE, Stat3 < 0.05). We also assessed the A concentrations from guanidine-soluble (insoluble) fractions of bulk cortical or forebrain vasculature extracts (Fig. 1JCO). HAE-4 significantly reduced insoluble bulk cortical A42 (Fig. 1K, < 0.01) and insoluble vascular A40 and A42 (Fig. 1N, ?,O,O, < 0.05) compared to chi-Adu but not compared to control IgG (Fig. 1K: = 0.09; Fig. 1N, ?,O:O: = 0.08). Thus, not only did HAE-4 reduce parenchymal plaques consistent with our previous findings (19), but HAE-4 also decreased CAA and exhibited higher efficacy compared to chi-Adu in a mouse model with prominent CAA. Open in a separate windows Fig. 1: HAE-4 reduces parenchymal A plaques and CAA in 5XE4 mice.A, Schematic timeline of antibody treatment in 5XFAD (line 7031) x < 0.05, PTP1B-IN-3 **< 0.01. No other statistical comparisons are significant unless indicated. Chi-Adu but not HAE-4 exacerbates CAA-related microhemorrhages The pathogenic mechanism underlying ARIA is usually unclear. One hypothesis is usually that focal, prolonged inflammation resulting from A antibodies targeting PTP1B-IN-3 of CAA impairs vascular integrity, leading to microhemorrhages or ARIA (6, 21). Given that HAE-4 is usually selective for non-lipidated APOE, a small component of the material in ThioS+ or X34+ dense core plaques and CAA, we hypothesized that HAE-4 would be involved in microglial-mediated A PTP1B-IN-3 removal but induce less prolonged inflammation compared to chi-Adu. This is because whereas HAE-4 favors dense core fibrillar plaques, chi-Adu binds abundantly to both diffuse and fibrillar plaques in tissue from 5XE4 mice and human CAA and AD (Fig. 2, Table S1) and might have less effective CAA clearance. Open in a separate windows Fig. 2: HAE-4 selectively binds dense core fibrillar plaques whereas chi-Adu recognizes both dense core and diffuse A plaques.A, B, Triple co-staining of X34, HAE-4 (A), and chi-Adu (B) in unfixed, cortical.