Biology subjects

Amason, J.

Publications and source records attributed to Amason, J..

3 recordsLinked to original sources

bioRxiv2024

Truncated Complement Factor H Y402 Gene Therapy Cures C3 Glomerulonephritis

Patients with both age-related macular degeneration (AMD) and C3 glomerulonephritis (C3G) are challenged by the absence of effective therapies to reverse and eliminate their disease burden. Capitalizing on complement dysregulation as both a significant risk factor for AMD and the known pathophysiology of C3G, we investigated the potential for adeno-associated virus (AAV) delivery of complement factor H (CFH) to rescue C3G in a Cfh-/- mouse model of C3G. While past efforts to treat C3G using exogenous human CFH resulted in limited success before immune rejection led to a foreign protein response, our findings demonstrate the capacity for long-term AAV-mediated delivery of truncated CFH (tCFH) to restore inhibition of the alternative pathway of complement and ultimately reverse C3G without immune rejection. Comparing results from the administration of several tCFH vectors also revealed significant differences in their relative efficiency and efficacy. These discoveries pave the way for subsequent development of AAV-mediated tCFH replacement therapy for patients with C3G, while simultaneously demonstrating proof of concept for a parallel AAV-mediated tCFH gene augmentation therapy for patients with AMD.

pathology↗

bioRxiv2023

Microglia at Sites of Atrophy Restrict the Progression of Retinal Degeneration via Galectin-3 and Trem2 Interactions

Degenerative diseases of the outer retina, including age-related macular degeneration (AMD), are characterized by atrophy of photoreceptors and retinal pigment epithelium (RPE). In these blinding diseases, macrophages are known to accumulate ectopically at sites of atrophy, but their ontogeny and functional specialization within this atrophic niche remain poorly understood, especially in the human context. Here, we uncovered a transcriptionally unique profile of microglia, marked by galectin-3 upregulation, at atrophic sites in mouse models of retinal degeneration and in human AMD. Using disease models, we found that conditional deletion of galectin-3 in microglia led to defects in phagocytosis and consequent augmented photoreceptor death, RPE damage and vision loss, suggestive of a protective role. Mechanistically, Trem2 signaling orchestrated the migration of microglial cells to sites of atrophy, and there, induced galectin-3 expression. Moreover, pharmacologic Trem2 agonization led to heightened protection, but only in a galectin-3-dependent manner, further signifying the functional interdependence of these two molecules. Likewise in elderly human subjects, we identified a highly conserved population of microglia at the transcriptomic, protein and spatial levels, and this population was enriched in the macular region of postmortem AMD subjects. Collectively, our findings reveal an atrophy-associated specialization of microglia that restricts the progression of retinal degeneration in mice and further suggest that these protective microglia are conserved in AMD. One Sentence SummaryA common neuroprotective response of microglia at the site of retinal atrophy is identified in mice and humans.

immunology↗

bioRxiv2019

A Homogeneous SIRPα-CD47 Cell-Based, Ligand-Binding Assay: Utility for Small Molecule Drug Development in Immuno-oncology.

CD47 is an immune checkpoint protein that downregulates both the innate and adaptive anti-tumor immune response via its counter receptor SIRP. Biologics, including humanized CD47 monoclonal antibodies and decoy SIRP receptors, that block the SIRP-CD47 interaction, are currently being developed as cancer immunotherapy agents. However, adverse side effects and limited penetration of tumor tissue associated with their structure and large size may impede their clinical application. We recently developed a quantitative high throughput screening assay platform to identify small molecules that disrupt the binding of SIRP and CD47 as an alternative approach to these protein-based therapeutics. Here, we report on the development and optimization of a cell-based binding assay to validate active small molecules from our biochemical screening effort. This assay has a low volume, high capacity homogenous format that relies on laser scanning cytometry (LSC) and associated techniques to enhance signal to noise measurement of cell surface binding. The LSC assay is specific, concentration dependent, and validated for the two major human SIRP variants (V1 and V2), with results that parallel those of our biochemical data as well as published studies. The LSC assay also confirmed published studies, such as the inhibition of amino-terminal pyroglutamate formation in CD47 disrupts SIRP binding. SIRP-CD47 interaction could be quantitatively measured in live and fixed tumor cells. Use of fixed cells reduces the burden of cell maintenance and provides stable cell standards to control for inter- and intra-assay variations. We also demonstrate the utility of the assay to characterize the activity of the first reported small molecule antagonists of the SIRP-CD47 interaction. This assay will support the screening of thousands of compounds to identify or validate active small molecules as hits, develop structure activity relationships and assist in the optimization of hits to leads by a typical iterative medicinal chemistry campaign.

immunology↗