Amyloid-β and p-Tau Anti-Threat Response to Herpes Simplex Virus 1 Infection in Primary Adult Murine Hippocampal Neurons

Abstract

Alzheimer's Disease (AD) is the sixth leading cause of death in the United States. Recent studies have established a potential link between herpes simplex virus 1 (HSV-1) infection and the development of AD. HSV-1 DNA has been detected in AD amyloid plaques in human brains, and treatment with the antiviral acyclovir (ACV) was reported to block the accumulation of the AD-associated proteins beta-amyloid (Aβ) and hyper-phosphorylated tau (p-tau) in Vero and glioblastoma cells. Our goal was to determine whether the accumulation of AD-related proteins is attributable to acute and/or latent HSV-1 infection in mature hippocampal neurons, a region of the brain severely impacted by AD. Primary adult murine hippocampal neuronal cultures infected with HSV-1, with or without antivirals, were assessed for Aβ and p-tau expression over 7 days postinfection. P-tau expression was transiently elevated in HSV-1-infected neurons, as well as in the presence of antivirals alone. Infected neurons, as well as uninfected neurons treated with antivirals, had a greater accumulation of Aβ₄₂ than uninfected untreated neurons. Furthermore, Aβ₄₂ colocalized with HSV-1 latency-associated transcript (LAT) expression. These studies suggest that p-tau potentially acts as an acute response to any perceived danger-associated molecular pattern (DAMP) in primary adult hippocampal neurons, while Aβ aggregation is a long-term response to persistent threats, including HSV-1 infection.IMPORTANCE Growing evidence supports a link between HSV-1 infection and Alzheimer's disease (AD). Although AD is clearly a complex multifactorial disorder, an infectious disease etiology provides alternative therapy opportunities for this devastating disease. Understanding the impact that HSV-1 has on mature neurons and the proteins most strongly associated with AD pathology may identify specific mechanisms that could be manipulated to prevent progression of neurodegeneration and dementia.

Keywords: Alzheimer’s disease; HSV-1; amyloid-β; herpes simplex virus; hippocampal neurons; p-tau; primary neurons; protein plaques.