Alzheimer’s disease (AD) therapies utilizing amyloid-β (Aβ) immunization have shown potential in clinical trials. Yet, the mechanisms driving Aβ clearance in the immunized AD brain remain unclear. Here, we use spatial transcriptomics to explore the effects of both active and passive Aβ immunization in the AD brain. We compare actively immunized patients with AD with nonimmunized patients with AD and neurologically healthy controls, identifying distinct microglial states associated with Aβ clearance. Using high-resolution spatial transcriptomics alongside single-cell RNA sequencing, we delve deeper into the transcriptional pathways involved in Aβ removal after lecanemab treatment. We uncover spatially distinct microglial responses that vary by brain region. Our analysis reveals upregulation of the triggering receptor expressed on myeloid cells 2 (TREM2) and apolipoprotein E (APOE) in microglia across immunization approaches, which correlate positively with antibody responses and Aβ removal. Furthermore, we show that complement signaling in brain myeloid cells contributes to Aβ clearance after immunization. These findings provide new insights into the transcriptional mechanisms orchestrating Aβ removal and shed light on the role of microglia in immune-mediated Aβ clearance. Importantly, our work uncovers potential molecular targets that could enhance Aβ-targeted immunotherapies, offering new avenues for developing more effective therapeutic strategies to combat AD.

Simple group testing designs to improve SARS-CoV-2 surveillance in resource-constrained settings are identified using modeling and experimental data.

Background: Modern Alzheimer’s disease (AD) therapeutics include immunization against amyloid‐β (Aβ). Intriguingly, neuropathological examination of the first active Aβ vaccination trial (Elan Pharmaceuticals’ AN1792) showed some patients with evidence of Aβ clearance 15 years post‐vaccination. Yet, these patients progressed to severe dementia before death, possibly due to ongoing tau propagation. The AN1792 trial was halted when some participants developed aseptic meningoencephalitis driven by auto‐aggressive T cells. Imaging features of meningoencephalitis experienced by AN1792 subjects are pathologically reminiscent of amyloid‐related imaging abnormalities (ARIA) that currently hamper clinical trials and the therapeutic use of passive Aβ immunotherapy for AD.Method: Here, we utilized spatial transcriptomics to sequence RNA from formalin‐fixed paraffin‐embedded (FFPE) cortical brain sections from a unique neuropathological cohort of 14 immunized AD cases and a placebo‐control from AN1792. Additional controls included 6 naïve (unimmunized) AD cases and 3 non‐neurological disease controls.Result: We reveal a cytotoxic and migratory phenotype of infiltrating T cells in the meninges of AD patients immunized against Aβ. Specifically, brain infiltrating T cells express cytotoxic genes (e.g. GZMA), activation genes (e.g. CD74 and B2M), and migratory genes (e.g. ITGAL and VCAM1). Additionally, we discovered genetic signatures that distinguish cortical areas cleared of Aβ in immunized AN1792 subjects.Conclusion: We show that active Aβ immunotherapy induces long‐term adaptive immune effects in the AD cortex.