Tau protein, a biomarker of Alzheimer's disease: in vitro phosphorylation and tau-reactive antibodies characterization

Tau protein, a microtubule-associated protein localized in axonal projections of neurons, is a key molecule in the pathology of Alzheimer's disease (AD), the most common cause of dementia in the elderly population. Tau belongs to the group of natively unfolded proteins without globular structure and is prone to numerous posttranslational modifications (PTMs). Under pathological conditions, abnormal PTMs and misfolding of tau protein occurs and leads to oligomerization and aggregation into paired helical filaments forming neurofibrillary tangles, the histopathological hallmark of AD. Currently available drugs applied in AD treatment can only slow the disease progression and those, which halt the AD-specific neurodegenerative processes, are still missing. Very promising and evolving therapeutic approach is immunotherapy, and even immunomodulation by administration of intravenous immunoglobulin (IVIG) products, a reservoir of natural antibodies from the plasma of healthy donors, has been already tested. The discovery of naturally occurring antibodies directed to tau (nTau-Abs) in body fluids of both AD and healthy subjects and their presence in IVIG begin the investigation of their therapeutic potential. Considering a wide range of possible modifications of tau and of various tau species (oligomers,..