Plasma tau phosphorylated at threonine 181 (pTau181) is a key blood-based biomarker that correlates with the burden of amyloid-beta (Aβ) pathology in Alzheimer’s disease (AD). The Elecsys® Phospho-Tau (181P) Plasma (pT181p) immunoassay (Roche Diagnostics International Ltd, Rotkreuz, Switzerland) is intended for use as an aid in the early detection of Aβ pathology in adults ≥ 55 years presenting with complaints of cognitive decline and is Conformité Européenne-marked and approved for clinical use by the US FDA. Here, we evaluated the stability of plasma pTau181 measured using the pT181p immunoassay under different pre-analytical and storage conditions in samples from an intended-use population. Whole blood samples from individuals presenting at LMU Hospital with symptom severity ranging from subjective cognitive decline to moderate AD dementia were collected in three different tubes for plasma preparation (Li-Heparin, K2-EDTA, and K3-EDTA). These were transported under cooled (never frozen) conditions to the measurement site and processed within 6 h of collection. Plasma samples were stored at different temperatures for varying durations, and impact on plasma pTau181 recoveries was assessed. Out-of-specification results not meeting pre-defined acceptance criteria observed in an initial cohort (n = 14), were found to be the result of buffy coat/erythrocyte contamination. Pre-analytical procedures were modified to prevent contamination during post-centrifugation plasma transfer. In samples from a separate cohort (n = 10), no instabilities were observed and acceptance criteria were met. After considering safety margins, analyte stability for all sample types was determined to be 2 days at 25 °C, 7 days at 4 °C, 12 weeks at -20 °C, and 16 weeks at -80°C; stability was also observed after one freeze/thaw cycle. pT181p immunoassay measurements were stable and robust with respect to different sample handling procedures and storage conditions. These findings support implementation of the assay into routine, non-specialist healthcare settings to facilitate practical blood-based testing to rule out AD-related Aβ pathology.
Current treatments for Alzheimer’s disease (AD) offer limited benefits, and many amyloid-targeting therapies have failed. This has led to exploring alternative approaches, including plasma exchange (PE) with albumin replacement. While this treatment shows promise as a potential therapy, its effect on Aβ pathology, neuroinflammation, and cognitive function is not yet fully understood. APP/PS1 mice received a monthly PE treatment starting at 11 months of age, when the animals had reached an advanced stage of amyloid pathology in this model. Brain and plasma biomarkers were quantified, and immunofluorescence staining of plaques and microglia was performed. Aged APP/PS1 mice subjected to PE showed significantly reduced insoluble Aβ42 and Aβ40 levels, plaque burden, and overall microglia burden while increasing microglia engagement per plaque. These changes were accompanied by higher plasma Aβ levels. PE altered levels of cytokines linked to AD pathology; however, the neurodegenerative and neuroinflammatory markers NSE and GFAP were elevated in both transgenic groups relative to WT controls, but did not differ significantly between PE-treated and sham-treated mice. These findings demonstrate that PE with albumin replacement engages amyloid pathology and the neuroinflammatory milieu in the brain, even at advanced stages of the disease. Whether these changes improved the neurodegenerative state remains unknown. These results, along with our previous report, support the need for further studies on PE treatment for AD, including combination therapies and longitudinal studies at preclinical and clinical stages of the disease.
While early- and late-onset Alzheimer’s disease (AD) are defined by the same pathology, presentation of neuropsychiatric symptoms can differ between groups. In this study, we investigate differences in neuropsychiatric symptom co-occurrence between early-onset (EOAD) and late-onset AD (LOAD) using a network-based approach. This cross-sectional study included 655 EOAD (< 65 years, mean age 58.4 ± 4.5 years; 53
Chimeric antigen receptors (CARs) are being used to direct cytokine secretion and phagocytosis by immune and glial cells toward amyloid β (Aβ) pathology, effectively adapting oncology-derived cell therapies to Alzheimer’s disease (AD). New synthetic receptor systems can take this approach a step further by enabling cells to deliver genetically encoded therapeutics. Among these systems, T cells Redirected for Universal Cytokine Killing (TRUCKs), synthetic Notch (synNotch), and Synthetic Intramembrane Proteolysis Receptors (SNIPRs) have shown promise in oncology and, as CARs, could potentially be adapted to AD. Here, we compared these receptor systems in vitro using Jurkat cells and human regulatory T cells (Tregs). All receptors shared an Aβ-targeting binding domain derived from Aducanumab (Aduhelm) and were coupled to inducible expression cassettes driving identical transgenes: secreted Metridia luciferase (MetLuc) and a Lecanemab (Leqembi)-based chimeric human–mouse antibody (chLecanemab). To model AD pathology in vitro, cell clones were exposed to oligomer-enriched Aβ (AβO) preparations. In Jurkat cells, TRUCK, synNotch, and SNIPR systems were assessed for basal transcriptional leakage, ligand-independent activation, and ligand-dependent activation using flow cytometry and MetLuc reporter assays. Aβ-dependent production of chLecanemab by synNotch and SNIPR systems was further evaluated in Jurkat cells and human Tregs by immunofluorescence (IF). We found that the inducible expression cassettes of all receptor systems exhibited transcriptional leakage. Despite confirmed CAR function and transcriptional competence of 6xNFAT response elements paired with different minimal promoters, none of the TRUCK variants produced AβO-induced output significantly above basal leakage. In contrast, synNotch and SNIPR expressed in Jurkat cells and human Tregs responded robustly to AβO. We demonstrate that Aβ-targeting SNIPR and synNotch systems can support Aβ-dependent inducible transgene expression in vitro. Their modular architectures enable straightforward substitution of chLecanemab with alternative therapeutic payloads while preserving Aβ-dependent delivery. Because these receptors are orthogonal, the same sequences we provide can be used across different model species and cell types in further studies without requiring receptor redesign.
In Alzheimer’s disease (AD), early endosomal dysfunction and chronic neuroinflammation critically shape disease progression, yet the neuronal mechanisms underlying the coordinating intracellular trafficking and microglial immune responses remain poorly defined. Sortilin-1 (SORT1), a neuronal VPS10P-domain receptor implicated in endosomal trafficking, proteostasis, and AD genetic risk, acts as a potential integrator of neuronal homeostasis and neuroimmune signaling. Here, we investigated the role of neuronal SORT1 in regulating endosomal integrity and neuron-microglia communication in AD models. Using a co-culture system of human iPSC-derived neurons and microglia-like cells, we found that neuronal SORT1 deficiency disrupted endosomal trafficking and proteostatic balance, leading to the accumulation of β-C-terminal fragments (β-CTFs) of amyloid precursor protein (APP) and pathological tau species. These neuronal defects were accompanied by heightened microglial pro-inflammatory activation and increased neuronal vulnerability. Single-cell RNA-sequencing (scRNA-seq) analyses revealed that SORT1 was dynamically expressed in inflammatory microglial populations, supporting early adaptive activation but declining in late-stage AD, which coincided with chronic neuroinflammation. In contrast, preservation of neuronal SORT1 stabilized endosomal organization, attenuated maladaptive microglial responses, and promoted neuronal survival. Moreover, in the 5xFAD mouse model of AD, AAV-mediated neuronal SORT1 expression reduced DNA damage, decreased microglia-associated neuroinflammation, reduced Aβ plaque burden and improved cognitive performance. Together, these findings establish neuronal SORT1 as a critical regulator that preserves endosomal homeostasis, coordinates neuron-microglia crosstalk, and mitigates neurodegeneration and cognitive decline in AD models, highlighting its potential as a target for early therapeutic intervention. Neuronal SORT1 preserves endosomal homeostasis and restrains neuroinflammation in Alzheimer’s disease
