Phosphorylated-tau associates with HSV-1 chromatin and correlates with nuclear speckles decondensation in low-density host chromatin regions.

Abnormal tau phosphorylation is a key mechanism in neurodegenerative diseases. Evidence implicates infectious agents, such as Herpes Simplex Virus 1 (HSV-1), as co-factors in the onset or the progression of neurodegenerative diseases, including Alzheimer's disease. This has led to divergence in the field regarding the contribution of viruses in the etiology of neurodegenerative diseases. Research indicates that viruses may function as risk factors driving neurodegenerative disease rather than playing a causative role. Investigating HSV-1 in abnormal tau phosphorylation is important for understanding the role of infectious agents in neurodegeneration. We generated cellular models of HSV-1 acute, latent infection, and viral reactivation from latency in cortical brain organoids and investigated the interplay between tau phosphorylation and HSV-1 infection by employing human induced pluripotent stem cell (iPSC)-derived monolayer neuronal cultures and brain organoids. Acute infection with HSV-1 strains 17syn⁺ and KOS caused nuclear accumulation of phosphorylated tau (p-tau) in neurons and neural precursor cells. Antivirals prevented nuclear accumulation of p-tau. Viral reactivation was accompanied by the nuclear translocation of p-tau. Chromatin immunoprecipitation analysis indicated an interaction of p-tau with the viral chromatin. A reduction in abundance of component of nuclear speckles and their loss of organized morphology in low-denisty host chromatin regions was observed, with strain-specific differences. HSV-1 infection was followed by an increase in the abundance of BRSKs and TAOKs, kinases known to phosphorylate tau. These findings show interaction between p-tau and HSV-1 chromatin and demonstrate the ability of HSV-1 to activate mechanisms that are observed in Alzheimer's disease.