Haass, Christian

Abstract Glioblastomas exhibit low immunogenicity and a highly immunosuppressive tumor microenvironment (TME) mediated by both tumor cells and tumor associated microglia/macrophages (TAMs). However, biomarkers that allow for specific detection, monitoring and therapy response assessment of the TAM phenotype in glioblastoma are still lacking. To address this gap, we characterized the dynamics of TAM clusters in the TME of experimental SB28 glioblastoma using single-cell RNA sequencing, immunofluorescence, and molecular imaging and identified Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) as a dynamic TAM-specific target. Consequently, we investigated a novel 64 Cu-labeled TREM2 radiotracer with a blood-brain barrier transport vehicle for translational mapping of TAMs in the TME of glioblastoma. We found strong and highly myeloid cell-specific PET signals that followed the trajectory of TREM2 gene expression from early- towards late-stage tumors. Transient myeloid cell depletion via CSF1R inhibition showed a reduction of TREM2 PET signals compared to placebo and prolonged survival in SB28 glioblastoma mice, while TREM2 stimulation led to increased TREM2 PET signals. Translation into a pilot cohort of patients with glioblastoma revealed strong TREM2 PET signals predominantly at lesion edges and high heterogeneity across individuals, matching with immunohistochemistry. In summary, TREM2 PET imaging has strong potential as an immune cell-specific biomarker for personalized assessment of the TAM phenotype in the TME of patients with glioblastoma.

AbstractINTRODUCTIONAt the Alzheimer's Association's APOE and Immunity virtual conference, held in October 2021, leading neuroscience experts shared recent research advances on and inspiring insights into the various roles that both the apolipoprotein E gene (APOE) and facets of immunity play in neurodegenerative diseases, including Alzheimer's disease and other dementias.METHODSThe meeting brought together more than 1200 registered attendees from 62 different countries, representing the realms of academia and industry.RESULTSDuring the 4‐day meeting, presenters illuminated aspects of the cross‐talk between APOE and immunity, with a focus on the roles of microglia, triggering receptor expressed on myeloid cells 2 (TREM2), and components of inflammation (e.g., tumor necrosis factor α [TNFα]).DISCUSSIONThis manuscript emphasizes the importance of diversity in current and future research and presents an integrated view of innate immune functions in Alzheimer's disease as well as related promising directions in drug development.

Abstract Neurofilament light chain, a putative measure of neuronal damage, is measurable in blood and CSF and is predictive of cognitive function in individuals with Alzheimer’s disease. There has been limited prior work linking neurofilament light and functional connectivity, and no prior work has investigated neurofilament light associations with functional connectivity in autosomal dominant Alzheimer’s disease. Here, we assessed relationships between blood neurofilament light, cognition, and functional connectivity in a cross-sectional sample of 106 autosomal dominant Alzheimer’s disease mutation carriers and 76 non-carriers. We employed an innovative network-level enrichment analysis approach to assess connectome-wide associations with neurofilament light. Neurofilament light was positively correlated with deterioration of functional connectivity within the default mode network and negatively correlated with connectivity between default mode network and executive control networks, including the cingulo-opercular, salience, and dorsal attention networks. Further, reduced connectivity within the default mode network and between the default mode network and executive control networks was associated with reduced cognitive function. Hierarchical regression analysis revealed that neurofilament levels and functional connectivity within the default mode network and between the default mode network and the dorsal attention network explained significant variance in cognitive composite scores when controlling for age, sex, and education. A mediation analysis demonstrated that functional connectivity within the default mode network and between the default mode network and dorsal attention network partially mediated the relationship between blood neurofilament light levels and cognitive function. Our novel results indicate that blood estimates of neurofilament levels correspond to direct measurements of brain dysfunction, shedding new light on the underlying biological processes of Alzheimer’s disease. Further, we demonstrate how variation within key brain systems can partially mediate the negative effects of heightened total serum neurofilament levels, suggesting potential regions for targeted interventions. Finally, our results lend further evidence that low-cost and minimally invasive blood measurements of neurofilament may be a useful marker of brain functional connectivity and cognitive decline in Alzheimer’s disease.

Aβ deposition in the basal ganglia is common in autosomal dominant Alzheimer’s disease. Vöglein et al. report an increased severity of motor symptoms in autosomal dominant versus sporadic disease in advanced disease stages. Motor symptoms are more severe in post-codon 200 presenilin 1 mutation carriers and correlate with basal ganglia Aβ.