Development of ultra-efficient antibodies for single cell mapping applications - PROJECT SUMMARY Histone post-translational modifications (PTMs) are some of the most widely studied epigenomic factors, and alterations in histone PTM abundance / distribution have been implicated in numerous disease etiologies. Epigenomic mapping of histone PTMs in limited cell populations or single cells (SCs) would provide the opportunity to study the epigenetic landscape of rare and heterogenous cell populations and be highly enabling for drug discovery research. The recent development of the antibody-mediated genomic mapping approach CUT&Tag (Cleavage Under Targets and Tagmentation) permits the study of select, abundant histone PTMs using very few cells and even SCs. Despite this progress, ultra-low input and SC CUT&Tag assays still present a unique challenge, and have not yet been successfully applied to many challenging targets, such as less abundant histone PTMs. Indeed, to maximize data yield per cell, ultra-low input and SC CUT&Tag assays require antibodies to exhibit high on-target epitope binding with minimal off-target binding, which most commercial antibodies do not offer. We envision a new class of “SC-grade” antibodies that deliver ultra-efficient histone PTM binding for dramatically increased CUT&Tag assay sensitivity, improving reliability and providing access to new targets that are currently intractable. Here, EpiCypher will leverage a novel antibody development pipeline to generate ultra-efficient, “SC-grade” antibodies to unlock the potential of genomic mapping technology for next- generation ultra-low input / SC applications. Unlike traditional antibody development pipelines that use histone peptides for screening, a central innovation of our strategy is the implementation of recombinant modified designer nucleosome technology during antibody development. In Phase I equivalent studies, we used our novel approach to select and validate ultra-efficient antibodies for two key histone PTM targets (H3K4me1 and H3K4me3), generating antibodies that exhibit a >5-10x increase in nucleosome capture efficiency vs. current best-in-class antibodies. Importantly, these ultra-efficient antibodies generated significantly greater signal-to- noise in genomic mapping assays that employ low cell inputs, demonstrating strong proof-of-concept for our approach. In Phase II, we will leverage this validated antibody development pipeline to develop a suite of ultra- efficient antibodies and use these reagents to develop low input and SC CUT&Tag assays for breakthrough immunology research. Toward this goal, we will first develop and screen antibodies for high-value histone PTM targets (Aim 1). We will then scale up production and rigorously validate antibody lots in CUT&Tag assays using both low input and SC workflows (Aim 2). Finally, we will test the application of our next-generation ultra-efficient antibodies to enable cutting-edge immunological research and provide our antibodies and validated protocols to leading epigenetics laboratories for beta testing (Aim 3). This research project will result in the development of a new class of histone PTM antibodies that will be used to increase the utility of CUT&Tag assays for breakthrough chromatin research and drug discovery.
