Immunotherapy perspectives in the new era of B-cell editing

In vivo tracking of ex-vivo-generated 89Zr-oxine-labeled plasma cells by PET in a non-human primate model

B cells are an attractive platform for engineering to produce protein-based biologics absent in genetic disorders, and potentially for the treatment of metabolic diseases and cancer. As part of pre-clinical development of B cell medicines, we demonstrate a method to collect, ex vivo expand, differentiate, radioactively label, and track adoptively transferred non-human primate (NHP) B cells. These cells underwent 10- to 15-fold expansion, initiated IgG class switching, and differentiated into antibody-secreting cells. Zirconium-89-oxine-labeled cells were infused into autologous donors without any preconditioning and tracked by PET/CT imaging. Within 24 h of infusion, 20% of the initial dose homed to the bone marrow and spleen and distributed stably and equally between the two. Interestingly, approximately half of the dose homed to the liver. Image analysis of the bone marrow demonstrated inhomogeneous distribution of the cells. The subjects experienced no clinically significant side effects or laboratory abnormalities. A second infusion of B cells into one of the subjects resulted in an almost identical distribution of cells, suggesting possibly a non-limiting engraftment niche and feasibility of repeated infusions. This work supports the NHP as a valuable model to assess the potential of B cell medicines as potential treatment for human diseases.

In vivo tracking of ex vivo generated 89 Zr-oxine labeled plasma cells by PET in a non-human primate model

B cells are an attractive platform for engineering to produce protein-based biologics absent in genetic disorders, and potentially for the treatment of metabolic diseases and cancer. As part of pre-clinical development of B cell medicines, we demonstrate a method to collect, ex vivo expand, differentiate, radioactively label, and track adoptively transferred non-human primate (NHP) B cells. These cells underwent 10- to 15-fold expansion, initiated IgG class switching, and differentiated into antibody secreting cells. Zirconium-89-oxine labeled cells were infused into autologous donors without any preconditioning and tracked by PET/CT imaging. Within 24 hours of infusion, 20% of the initial dose homed to the bone marrow and spleen and distributed stably and equally between the two. Interestingly, approximately half of the dose homed to the liver. Image analysis of the bone marrow demonstrated inhomogeneous distribution of the cells. The subjects experienced no clinically significant side effects or laboratory abnormalities. A second infusion of B cells into one of the subjects resulted in an almost identical distribution of cells, suggesting a non-limiting engraftment niche and feasibility of repeated infusions. This work supports the NHP as a valuable model to assess the potential of B cell medicines as potential treatment for human diseases.

Production of therapeutic levels of human FIX-R338L by engineered B cells using GMP-compatible medium

B cells can differentiate into plasmablast and plasma cells, capable of producing antibodies for decades. Gene editing using zinc-finger nucleases (ZFN) enables the engineering of B cells capable of secreting sustained and high levels of therapeutic proteins. In this study, we established an advanced in vitro good manufacturing practice-compatible culturing system characterized by robust and consistent expansion rate, high viability, and efficient B cell differentiation. Using this process, an optimized B cell editing protocol was developed by combining ZFN/adeno-associated virus 6 technology to achieve site-specific insertion of the human factor IX R338L Padua into the silent TRAC locus. In vitro analysis revealed high levels of secreted human immunoglobulins and human factor IX-Padua. Following intravenous infusion in a mouse model, human plasma cells were detected in spleen and bone marrow, indicating successful and potentially long-term engraftment in vivo. Moreover, high levels of human immunoglobin and therapeutic levels of human factor IX-Padua were detected in mouse plasma, correlating with 15% of normal human factor IX activity. These data suggest that the proposed process promotes the production of functional and differentiated engineered B cells. In conclusion, this study represents an important step toward the development of a manufacturing platform for potential B cell-derived therapeutic products.

Adenoviral vectors infect B lymphocytes in vivo

B cells are the antibody-producing arm of the adaptive immune system and play a critical role in controlling pathogens. Several groups have now demonstrated the feasibility of using engineered B cells as a therapy, including infectious disease control and gene therapy of serum deficiencies. These studies have largely utilized ex vivo modification of the cells. Direct in vivo engineering would be of utility to the field, particularly in infectious disease control where the infrastructure needs of ex vivo cell modification would make a broad vaccination campaign highly challenging. In this study we demonstrate that engineered adenoviral vectors are capable of efficiently transducing murine and human primary B cells both ex vivo and in vivo. We found that unmodified human adenovirus C5 was capable of infecting B cells in vivo, likely due to interactions between the virus penton base protein and integrins. We further describe vector modification with B cell-specific gene promoters and successfully restrict transgene expression to B cells, resulting in a strong reduction in gene expression from the liver, the main site of human adenovirus C5 infection in vivo.

Challenges and opportunities in gene editing of B cells

B cells have long been an underutilized target in immune cell engineering, despite a number of unique attributes that could address longstanding challenges in medicine. Notably, B cells evolved to secrete large quantities of antibodies for prolonged periods, making them suitable platforms for long-term protein delivery. Recent advances in gene editing technologies, such as CRISPR-Cas, have improved the precision and efficiency of engineering and expanded potential applications of engineered B cells. While most work on B cell editing has focused on ex vivo modification, a body of recent work has also advanced the possibility of in vivo editing applications. In this review, we will discuss both past and current approaches to B cell engineering, and its promising applications in immunology research and therapeutic gene editing.

Recent advances in biomaterial-boosted adoptive cell therapy

Adoptive immunotherapies based on the transfer of functional immune cells hold great promise in treating a wide range of malignant diseases, especially cancers, autoimmune diseases, and infectious diseases. However, manufacturing issues and biological barriers lead to the insufficient population of target-selective effector cells at diseased sites after adoptive transfer, hindering effective clinical translation. The convergence of immunology, cellular biology, and materials science lays a foundation for developing biomaterial-based engineering platforms to overcome these challenges. Biomaterials can be rationally designed to improve ex vivo immune cell expansion, expedite functional engineering, facilitate protective delivery of immune cells in situ, and navigate the infused cells in vivo. Herein, this review presents a comprehensive summary of the latest progress in biomaterial-based strategies to enhance the efficacy of adoptive cell therapy, focusing on function-specific biomaterial design, and also discusses the challenges and prospects of this field.