Herpes simplex virus type 1 induces nuclear accumulation of hyperphosphorylated tau in neuronal cells.

Herpes simplex virus type 1 (HSV-1) is a neurotropic virus that remains latent in host neurons. Viral DNA replication is a highly structured process in which the redistribution of nuclear proteins plays an important role. Although tau is most widely known as a microtubule-associated protein found in a hyperphosphorylated state in the brains of patients with Alzheimer's disease (AD), this protein has also been detected at other sites such as the nucleolus. Here, we establish that HSV-1 infection gives rise to an increase in tau phosphorylation and that hyperphosphorylated tau accumulates in the nucleus, forming defined structures in HSV-1-infected neuronal cells reminiscent of the common sites of viral DNA replication. When tau expression in human neuroblastoma cells was specifically inhibited using an adenoviral vector expressing a short hairpin RNA to tau, viral DNA replication was not affected, indicating that tau is not required for HSV-1 growth in neuronal cells. Given that HSV-1 is considered a risk factor for AD, our results suggest a new way in which to understand the relationships between HSV-1 infection and the pathogenic mechanisms leading to AD.