title: Passive immunization targeting the N-terminal region of phosphorylated tau (residues 68-71) improves spatial memory in okadaic acid induced tauopathy model rats.
abstract: Alzheimer's disease (AD) is the leading cause of dementia, characterized by progressive loss of memory and other cognitive functions. The cognitive impairment in patients with AD is closely associated with loss of synapses and the formation of neurofibrillary tangles (NFT) containing hyperphosphorylated tau in the hippocampus. Effective treatment for AD is still not available. In this study, the sequence comprising of residues 50-71 in the N-terminal region of tau, containing theoretically predicted B- and T-cell epitopes in close proximity to pathologically relevant phospho-serine (residue 68) and phospho-threonine (residues 69, 71) was selected as a potential immunotherapeutic peptide. This 22-residue long phospho-peptide (50TPTEDGSEEPGSETSDAKpSpTPpT71) was custom synthesized and its therapeutic potential was tested in experimental rats. For this purpose, adult Sprague-Dawley rats were intranasally treated with okadaic acid (OA), a selective inhibitor of protein phosphatase PP2A. Within a day of OA administration, these rats showed marked impairment in cognitive functions with a significant increase in p-tau/t-tau ratio in the hippocampal homogenates. Passive immunization studies conducted in these OA treated rats with polyclonal anti-phospho-peptide antibodies resulted in a significant improvement in learning and memory functions in Barne's maze task. Further, p-tau levels in the hippocampal homogenates were reduced. In addition, these antibodies effectively prevented the aggregation of recombinant tau in vitro. These results demonstrate that targeting N-terminal region of tau harbouring the phospho-residue cluster 68-71 would be beneficial and may present an effective therapeutic opportunity for AD and other tauopathies.
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health & Neurosciences, Bangalore, 560 029, India. Electronic address: sarada@nimhans.ac.in.
authors.forename: Sarada
authors.initials: S
authors.lastname: Subramanian
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health & Neurosciences, Bangalore, 560 029, India.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Savanur
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health & Neurosciences, Bangalore, 560 029, India.
authors.forename: Sowmya
authors.initials: S
authors.lastname: Madhavadas
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D000939:Epitopes / Q000737:chemistry; D005260:Female; D006624:Hippocampus / Q000378:metabolism; D007114:Immunization / Q000379:methods*; D008297:Male; D019319:Okadaic Acid / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D000072417:Protein Domains; D054648:Protein Phosphatase 2 / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D065852:Spatial Memory; D024801:Tauopathies / Q000139:chemically induced / Q000628:therapy*; D016875:tau Proteins / Q000737:chemistry*
chemical_list: D000939:Epitopes; C489131:Mapt protein, rat; D010455:Peptides; D011994:Recombinant Proteins; D016875:tau Proteins; D019319:Okadaic Acid; C514014:Ppp2ca protein, rat; D054648:Protein Phosphatase 2
keywords: Alzheimer disease; Okadaic acid; Phosphopeptide; Spatial memory; Tau; Tauopathy