INTRODUCTION: While there may be microbial contributions to Alzheimer’s disease (AD), findings have been inconclusive. We recently reported an AD-associated CD83(+)microglia subtype associated with increased immunoglobulinG4(IgG4) in the transverse colon (TC).
METHODS: We used immunohistochemistry (IHC), IgG4 repertoire profiling, and brain organoid experiments to explore this association.
RESULTS: CD83(+) microglia in the superior frontal gyrus (SFG) are associated with elevated IgG4 and human cytomegalovirus (HCMV) in the TC, anti-HCMV IgG4 in cerebrospinal fluid, and both HCMV and IgG4 in the SFG and vagal nerve. This association was replicated in an independent AD cohort. HCMV-infected cerebral organoids showed accelerated AD pathophysiological features (Aβ42 and pTau-212) and neuronal death.
DISCUSSION: Findings indicate complex, cross-tissue interactions between HCMV and the adaptive immune response associated with CD83(+)microglia in persons with AD. This may indicate an opportunity for antiviral therapy in persons with AD and biomarker evidence of HCMV, IgG4, or CD83(+)microglia.