Short ReportInternalization of tau antibody and pathological tau protein detected with a flow cytometry multiplexing approach

IntroductionTau immunotherapy has emerged as a promising approach to clear tau aggregates from the brain. Our previous findings suggest that tau antibodies may act outside and within neurons to promote such clearance.MethodsWe have developed an approach using flow cytometry, a human neuroblastoma cell model overexpressing tau with the P301L mutation, and paired helical filament (PHF)-enriched pathologic tau to effectively screen uptake and retention of tau antibodies in conjunction with PHF.ResultsThe flow cytometry approach correlates well with Western blot analysis to detect internalized antibodies in naïve and transfected SH-SY5Y cells (r2 = 0.958, and r2 = 0.968, P = .021 and P = .016, respectively). In transfected cells, more antibodies are taken up/retained as pathologic tau load increases, both under co-treated conditions and when the cells are pretreated with PHF before antibody administration (r2 = 0.999 and r2 = 0.999, P = .013 and P = .011, respectively).DiscussionThis approach allows rapid in vitro screening of antibody uptake and retention in conjunction with pathologic tau protein before more detailed studies in animals or other more complex model systems.