In addition to these biochemical assays, the presence of hyperphosphorylated tau was investigated by immunohistology using two phospho-tau specific antibodies: AT8 (phosphorylated Ser 202/Thr 205) and PHF1 (phosphorylated Ser 396/Ser 404). In 7-month-old mice, a strong immunoreactivity for AT8 and PHF1 antibodies was found in the cortex and hippocampus, in the AAV-WT group and to a lesser extent in the AAV-P301S group (Fig. 5b). Whereas immunoreactivity for phospho-tau epitopes was mainly observed in the axons of neurons overexpressing WT tau, phosphorylated P301S was more evident in the somatodendritic compartment. Altogether, these results indicate that overexpression of WT tau is characterized by a more extensive hyperphosphorylation pattern, which tends to further develop over time when compared to P301S tau.