Single domain antibodies as promising tools for the selective detection and neutralization of neurotoxic Aβ42 oligomers in the cerebrospinal fluid of Alzheimer’s disease patients

Abstract

AbstractBackgroundExtracellular amyloid β (Aβ) plaques and intracellular neurofibrillary tangles of the hyperphosphorylated tau protein are the main hallmarks of Alzheimer’s disease (AD). Small, soluble oligomers, rather than mature fibrils, are the major neurotoxic agents. The heterogeneous structures and the transient nature of these oligomers make their isolation and characterization very challenging. Single domain Abs (sdAbs), composed only of a variable domain of the heavy chain with high specificity and affinity, appear as promising tools for an early diagnosis and therapy for AD.MethodsPerforming an in vitro and in vivo screening of different sdAbs, we selected those targeting Aβ42 oligomers or fibrils with high specificity using dot‐blot, ELISA assay and the super resolution stimulated emission depletion (STED) microscopy. The potential of sdAbs was also investigated in preventing Aβ42 oligomer‐induced cytotoxicity in cultured neuronal cells. Then, the sdAbs were used to selectively detect Aβ42 species in the cerebrospinal fluid (CSF) of AD patients and control subjects and to neutralize their associated harmful effects following cell exposure to CSF samples.ResultssdAbs can selectively detect Aβ42 oligomers or fibrils both in vitro and in cultured cells, preventing the neurotoxicity induced by small oligomers. Moreover, sdAbs can significantly identify Aβ42 oligomers in the CSF of AD patients counteracting their induced toxicity in our cell models.ConclusionsAll these data provide a solid foundation for the development of sdAbs‐based immunodiagnostic tools that can selectively detect toxic aggregates in human body fluids for an early differential diagnosis of protein deposition diseases, such as AD. Furthermore, our results contribute to the improvement of the current therapeutic approaches against AD.The study was supported by Airalzh (AGYR 2020 to R.C.).