The blood-brain barrier-penetrating fusion protein BBB-ABP selectively binds amyloid-β oligomers and prevents in vitro neurotoxicity

BackgroundSoluble amyloid-β oligomers (Aβo) are considered the most neurotoxic species of Aβ and key drivers of Alzheimer's disease (AD) pathogenesis. Selective targeting of Aβo offers a promising therapeutic strategy. We previously identified an amyloid-binding peptide (ABP) that binds Aβo and engages Aβ deposits in AD mouse and human brain tissue. To facilitate brain penetration, ABP was fused to the blood-brain barrier (BBB) transporter FC5 and an Fc fragment, generating BBB-permeable constructs (mouse FC5-mFc2a-ABP and humanized FC5-hFc-ABP, referred to as BBB-ABP). Previous in vivo studies demonstrated the ability of BBB-enabled ABP to engage and clear Aβ from the central nervous system.ObjectiveThis study aimed to evaluate the in vitro functionality of BBB-ABP and its ability to prevent Aβo-induced neurotoxicity and synaptic dysfunction.MethodsBinding specificity was assessed using ELISA and western blot overlay assays. Functional assays were performed in SH-SY5Y cells and primary neurons to evaluate Aβo sequestration, protection against Aβo-induced toxicity, and effects on synaptic activity measured via multi-electrode arrays.ResultsBBB-ABP retained selective binding to Aβo and effectively prevented its interaction with neuronal proteins and its binding to dendritic spines in live primary neurons. BBB-ABP significantly reduced Aβo-induced toxicity in SH-SY5Y cells and primary neurons, including under conditions of NMDA-induced stress. Aβ exposure did not significantly alter spontaneous synaptic activity, precluding assessment of electrophysiological rescue by BBB-ABP.ConclusionsThese findings demonstrate that BBB-ABP maintains Aβo-selective binding and is capable of preventing the interaction of Aβo with neurons, thereby mitigating Aβo-induced toxicity in vitro, supporting its further development as a therapeutic candidate for AD.