Immunisation with tau peptide vaccine reduced tau oligomers and tau hyperphosphorylation. Western blot analysis with pan-tau monoclonal antibody DC25 showed reduction in oligomeric tau in the brain of transgenic rats treated with tau peptide vaccine (A). The monomeric endogenous rat tau proteins run between 43 and 68 kDa marker bands, whereas monomeric transgenic tau comprises multiple phospho-species between 29 and 43 kDa marker bands. In the vaccine-treated animals, there are only remnants of nonphosphorylated transgene running just above the 29 kDa marker band. Western blot analysis revealed significant reduction of hyperphosphorylated tau species phosphorylated at Thr217 (monoclonal antibody (mAb) DC217) (B), pThr231 (mAb DC209) (C), pSer202/pThr205 (mAb AT8) (D) and pThr181 (mAb DC179) (E). (F) The graph represents the quantification and statistical evaluation of the difference between animals treated with vaccine and those treated with adjuvant only; *P < 0.05, **P < 0.01 . A 6-μl sarkosyl-insoluble fraction was loaded per lane, which corresponds to 30 mg of tissue. Loading of an equal amount of sarkosyl-insoluble proteins, and the efficiency of electroblotting was verified by staining the membrane with Ponceau S (Additional file 1).