Herpes simplex virus alters Alzheimer's disease biomarkers - A hypothesis paper

Introduction: Human herpes simplex virus 1 (HSV1) is discussed to induce amyloid-β (Aβ) accumulation and neurofibrillary tangles of hyperphosphorylated tau (pTau) in Alzheimer's disease (AD) in cell culture and animal models. Aβ appears to be virostatic. We investigated the association between intrathecal antibodies against HSV or cytomegalovirus (CMV) and cerebrospinal fluid (CSF) AD biomarkers. Methods: Aβ₄₂/Aβ₄₀ ratio, pTau, and tTau were measured in CSF of 117 patients with early AD positive for amyloid pathology (A+) and 30 healthy controls (A-). CSF-to-serum anti-HSV1/2-IgG antibody indices (AI-IgG_HSV1/2) and CMV (AI-IgG_CMV) were determined by enzyme-linked immunosorbent assay (ELISA). Results: Exclusively in HSV1-seropositive AD, pTau was positively and significantly predicted by AI-IgG_HSV1/2 and negatively by the Aβ₄₂/Aβ₄₀ ratio in both univariate and multivariate regression analyses. Furthermore, a significant and negative interaction between the AI-IgG_HSV1/2 and Aβ₄₂/Aβ₄₀ ratio on pTau was found. Discussion: The results support the hypothesis that HSV infection contributes to AD. Highlights: HSV antibody index is positively associated with tau pathology in patients with AD. HSV antibody index is negatively associated with cerebral FDG metabolism. Amyloid modulates the association of HSV antibody index with CSF-pTau. HSV in AD offers a pathophysiological model connecting tau and amyloid.