PROJECT SUMMARY / ABSTRACT Pluripotent stem cells hold great promise for regenerative medicine. Beyond their ability to restore normal tissues, their potential can be expanded even further through engineering approaches to create new lineages with therapeutic properties that are not normally made in vivo. In preliminary studies, we have created pluripotent stem cell lines that 1) have been genomically edited such that they are able to cross human-mouse barriers; 2) engineered these cells to carry a knockin insertion of a broadly neutralizing HIV antibody at the endogenous loci. With these cells, we will develop strategies to differentiate human pluripotent stem cells into transplantable pathogen-specific plasma cells. This process will involve iterative and recursive steps to engineer pluripotent stem cell differentiation to downstream hematopoietic, B cell, and plasma cell lineages using single cell transcriptional trajectories as guides. These targeted approaches will be complemented with unbiased genetic and small molecule screens for new pathways that promote or inhibit specific steps in differentiation, and additional single cell transcriptomic and epigenetic analyses to provide templates for cellular engineering.