Advancing Cell Therapies: Single-Cell Profiling, Generation, Expansion, and Gene Delivery in Rhesus Macaque Plasma B Cells

Engineered long lived plasma cells have the potential to be a new area of cell therapy. A key step in developing this cell therapy is testing in a model with an intact immune system similar to humans. To that end, we have developed methods to purify, expand, and differentiate non-human primate (NHP; rhesus macaque) B cells ex vivo. We consistently achieved 10-fold expansion of NHP B cells using a readily available commercial supplement. After only seven days in culture, large percentages of cells in NHP B cell cultures were differentiated. These cells expressed surface markers found in human antibody secreting cells (CD38 and CD138) and secreted immunoglobulin G. From single cell transcriptome analysis of NHP, we verified the presence of plasma cell markers commonly shared with humans, and have unearthed less recognized markers such as CD59 and CD79A. In addition, we identified unique NHP plasma cell markers that are absent in humans including the immune checkpoint molecule CD274 (PD-L1, Programmed Death-Ligand 1). Furthermore, we found that MHC class I molecules were upregulated in NHP plasma cells, in contrast to the pattern observed in humans. Lastly, we also identified the serotypes (AAVD-J) and established the conditions for efficient transduction of NHP B cells with AAV vectors, achieving an editing rate of approximately 60%. We envision that this work will accelerate proof-of-concept in vivo studies using engineered protein-secreting B cells in the NHP model.