mRNA Vaccine for Alzheimer’s Disease: Pilot Study

The escalating global healthcare challenge posed by Alzheimer's Disease (AD) and compounded by the lack of effective treatments emphasizes the urgent need for innovative approaches to combat this devastating disease. Currently, passive and active immunotherapies remain the most promising strategy for AD. FDA-approved lecanemab significantly reduces Aβ aggregates from the brains of early AD patients administered biweekly with this humanized monoclonal antibody. Although the clinical benefits noted in these trials have been modest, researchers have emphasized the importance of preventive immunotherapy. Importantly, data from immunotherapy studies have shown that antibody concentrations in the periphery of vaccinated people should be sufficient for targeting Aβ in the CNS. To generate relatively high concentrations of antibodies in vaccinated people at risk of AD, we generated a universal vaccine platform, MultiTEP, and, based on it, developed a DNA vaccine, AV-1959D, targeting pathological Aβ, completed IND enabling studies, and initiated a Phase I clinical trial with early AD volunteers. Our current pilot study combined our advanced MultiTEP technology with a novel mRNA approach to develop an mRNA vaccine encapsulated in lipid-based nanoparticles (LNPs), AV-1959LR. Here, we report our initial findings on the immunogenicity of 1959LR in mice and non-human primates, comparing it with the immunogenicity of its DNA counterpart, AV-1959D

Therapeutic potential of human microglial transplantation in a chimeric model of CSF1R-related leukoencephalopathy

Microglia replacement strategies are increasingly being considered for the treatment of primary microgliopathies like adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). However, available mouse models fail to recapitulate the diverse neuropathologies and reduced microglia numbers observed in patients. In this study, we generated a xenotolerant mouse model lacking the fms-intronic regulatory element (FIRE) enhancer within Csf1r, which develops nearly all the hallmark pathologies associated with ALSP. Remarkably, transplantation of human induced pluripotent stem cell (iPSC)-derived microglial (iMG) progenitors restores a homeostatic microglial signature and prevents the development of axonal spheroids, white matter abnormalities, reactive astrocytosis, and brain calcifications. Furthermore, transplantation of CRISPR-corrected ALSP-patient-derived iMG reverses pre-existing spheroids, astrogliosis, and calcification pathologies. Together with the accompanying study by Munro and colleagues, our results demonstrate the utility of FIRE mice to model ALSP and provide compelling evidence that iMG transplantation could offer a promising new therapeutic strategy for ALSP and perhaps other microglia-associated neurological disorders

Routes and rates of bacterial dispersal impact surface soil microbiome composition and functioning.

Recent evidence suggests that, similar to larger organisms, dispersal is a key driver of microbiome assembly; however, our understanding of the rates and taxonomic composition of microbial dispersal in natural environments is limited. Here, we characterized the rate and composition of bacteria dispersing into surface soil via three dispersal routes (from the air above the vegetation, from nearby vegetation and leaf litter near the soil surface, and from the bulk soil and litter below the top layer). We then quantified the impact of those routes on microbial community composition and functioning in the topmost litter layer. The bacterial dispersal rate onto the surface layer was low (7900 cells/cm2/day) relative to the abundance of the resident community. While bacteria dispersed through all three routes at the same rate, only dispersal from above and near the soil surface impacted microbiome composition, suggesting that the composition, not rate, of dispersal influenced community assembly. Dispersal also impacted microbiome functioning. When exposed to dispersal, leaf litter decomposed faster than when dispersal was excluded, although neither decomposition rate nor litter chemistry differed by route. Overall, we conclude that the dispersal routes transport distinct bacterial communities that differentially influence the composition of the surface soil microbiome

Data for: Prescribed versus wildfire impacts on exotic plants and soil microbes in California grasslands

Prescribed burns are often used as a management tool to decrease exotic plant cover and increase native plant cover in grasslands. These changes may also be mediated by fire impacts on soil microbial communities, which drive plant productivity and function. Yet, the ecological effects of prescribed burns compared to wildfires on either plant or soil microbial composition remain unclear. Grassland fires account for roughly 80% of global annual fires, but only roughly 12% of research on belowground impacts of fires occurs in grasslands, limiting our understanding of aboveground belowground connections in these important habitats. Here, we took advantage of the serendipitous opportunity of a wildfire burning through the same reserve where we had previously sampled a prescribed burn. This enabled us to investigate the impacts of a spring prescribed burn versus a fall wildfire on plant cover and community composition and bacterial and fungal richness, abundance, and composition. Our California grassland sites were thus within the same reserve, limiting environmental, vegetation, or climate variation between the sites. We used qPCR of 16S and 18S to assess impacts on bacterial and fungal abundance and Illumina MiSeq of 16S and ITS2 to assess impacts on bacterial and fungal richness and composition. Wildfire had stronger impacts than prescribed burns on microbial communities and both fires had similar impacts on plants with both prescribed and wildfire reducing exotic plant cover but neither reducing exotic plant richness. Fungal richness declined after the wildfire but not prescribed burn, but bacterial richness was unaffected by either. Yet, fire exposure in both fire types resulted in reduced bacterial and fungal abundance and altered bacterial and fungal composition. Plant diversity differentially impacted soil microbial diversity, with exotic plant diversity positively impacting bacterial richness and having no effect on arbuscular mycorrhizal richness. However, the remainder of the soil microbial communities were more related to aspects of soil chemistry including cation exchange capacity, organic matter, pH and phosphorous. Our coupled plant and soil community sampling allowed us to capture the sensitivity to fire of the fungal community and highlights the importance of potentially incorporating management actions such as soil or fungal amendments to promote this critical community that mediates native plant performance.APSoil_file column header metadata.txt This is a central file that has column header descriptions for the Dryad data files. APSoil_SpringPlantdata.csv Plant species composition data for grassland plots in prescribed and wildfire study sites. It includes plots that were exposed to fire (i.e. burned) and those not (i.e. unburned). Data were collected in the first spring after the respective fire. Six letter species codes are used for column headers. Full species names for species codes can be found in APSoil_Plant Species List.csv Columns for species diversity response variables are also included in that are stratified across the entire community or based on species provenance (i.e. native or exotic). APSoil_Plant Species List.csv Provides full species names for any plant species observed during the study. A "NA" value was given for any species that had no field observation notes. APSoil_Bacterial-Metadata-withsoilPCA_final.csv Bacterial richness, diversity and abundance response variables for grassland plots sampled in prescribed and wildfire study sites that were either exposed to fire or not. Data are reported for multiple time points and file includes soil chemistry data and soil PCA axis scores that were used for data analysis. Soil samples were only collected for first time point after fire; thus the soil variables for other timepoints are listed as NA. APSoil_otu_Bacteria_16S_rarefied data.csv Bacterial OTU table after rarefication adjustments. The first column is a sample ID key that can be connected to plot treatment information found in APSoil_Bacterial-Metadata-withsoilPCA_final.csv APSoil_Fungal-Metadata-withsoilPCA_final.csv Fungal richness, diversity and abundance response variables for grassland plots sampled in prescribed and wildfire study sites that were either exposed to fire or not. Data are reported for multiple time points and file includes soil chemistry data and soil PCA axis scores that were used for data analysis. Soil samples were only collected for first time point after fire; thus the soil variables for other timepoints are listed as NA. APSoil_otu_Fungal_ITS_rarefied data.csv Fungal OTU table after rarefication adjustments. The first column is a sample ID key that can be connected to plot treatment information found in APSoil_Fungal-Metadata-withsoilPCA_final.csv APSoil_AMF data.csv Compiled data file that has summary spring plant richness and diversity metrics and richness, diversity metrics for arbuscular fungal mycorrhizaeFunding provided by: U.S. Bureau of Land ManagementCrossref Funder Registry ID: http://dx.doi.org/10.13039/100007149Award Number: L19AC0028

Engineering an inhibitor-resistant human CSF1R variant for microglia replacement

Hematopoietic stem cell transplantation (HSCT) can replace endogenous microglia with circulation-derived macrophages but has high mortality. To mitigate the risks of HSCT and expand the potential for microglia replacement, we engineered an inhibitor-resistant CSF1R that enables robust microglia replacement. A glycine to alanine substitution at position 795 of human CSF1R (G795A) confers resistance to multiple CSF1R inhibitors, including PLX3397 and PLX5622. Biochemical and cell-based assays show no discernable gain or loss of function. G795A- but not wildtype-CSF1R expressing macrophages efficiently engraft the brain of PLX3397-treated mice and persist after cessation of inhibitor treatment. To gauge translational potential, we CRISPR engineered human-induced pluripotent stem cell-derived microglia (iMG) to express G795A. Xenotransplantation studies demonstrate that G795A-iMG exhibit nearly identical gene expression to wildtype iMG, respond to inflammatory stimuli, and progressively expand in the presence of PLX3397, replacing endogenous microglia to fully occupy the brain. In sum, we engineered a human CSF1R variant that enables nontoxic, cell type, and tissue-specific replacement of microglia