MultiTEP‐based conjugated vaccines targeting various phosphorylated tau epitopes are immunogenic and effective in the PS19 mouse model

Abstract

AbstractBackgroundPathological tau correlates well with cognitive impairments in Alzheimer’s disease (AD) patients and represents a promising immunotherapy target. In theory, targeting an appropriate B‐cell epitope in pathological tau could effectively reduce the pathology without affecting normal native tau. Hyperphosphorylation of tau is a well‐known feature of Alzheimer’s and other tauopathies, with many disease‐specific phosphorylation sites documented. Accordingly, we attached several disease‐related phosphorylated tau peptides to our universal vaccine platform, MultiTEP that is safe and extremely immunogenic in various disease models of AD, rabbits, and aged monkeys. We hypothesized that high immunogenicity of MultiTEP‐based vaccines, coupled with the selectivity of the immune responses, will allow the identification of pathological and protective phosphorylation sites, thus leading to the generation of vaccines, which would preferentially clear the toxic forms of tau without disrupting the normal brain homeostasis.MethodA genetically engineered variant of MultiTEP was generated to enable chemoselective bioconjugation of synthetic peptides under mild aqueous conditions. MultiTEP‐based vaccines targeting p‐tau 202/205, p‐tau 396/404, p‐tau 422 were tested in the PS19 mouse model of AD and other tauopathies. Antibody specificity and titers were tested via ELISA. Brain total and phosphorylated soluble and insoluble tau were measured by ELISA and IHC.ResultAll three vaccines generated robust and selective immune responses specific to phosphorylated tau in mice. The generated antibodies selectively bound to the appropriate phosphorylated, but not non‐phosphorylated form of the same peptide. Importantly, these antibodies effectively reduce/cleared pathological tau in the brains of immunized mouse model of tauopathy. The MultiTEP immunogenicity was sufficient to generate robust immune responses after two immunizations, even without adjuvant.ConclusionMultiTEP‐based conjugated vaccines could be used to generate robust immune responses selective to multiple phosphorylation sites of tau. This, in conjunction with a previous report on MultiTEP‐based pE3Aβ vaccine, suggests that the methodology is universally applicable for various post‐translational modifications. Our technology can facilitate the identification of optimal therapeutic targets of p‐tau for generating an active immunotherapeutic strategy that can be used in conjunction with pE3Aβ vaccine. If successful, preventive vaccinations targeting disease‐related tau and/or Aβ molecules could at least delay AD and related neurodegenerative disorders.