Baboon envelope pseudotyped lentiviral vectors efficiently transduce human B cells and allow active factor IX B cell secretion in vivo in NOD/SCIDγc-/- mice.

Essentials B cells are attractive targets for gene therapy and particularly interesting for immunotherapy. A baboon envelope pseudotyped lentiviral vector (BaEV-LV) was tested for B-cell transduction. BaEV-LVs transduced mature and plasma human B cells with very high efficacy. BaEV-LVs allowed secretion of functional factor IX from B cells at therapeutic levels in vivo. SUMMARY: Background B cells are attractive targets for gene therapy for diseases associated with B-cell dysfunction and particularly interesting for immunotherapy. Moreover, B cells are potent protein-secreting cells and can be tolerogenic antigen-presenting cells. Objective Evaluation of human B cells for secretion of clotting factors such as factor IX (FIX) as a possible treatment for hemophilia. Methods We tested here for the first time our newly developed baboon envelope (BaEV) pseudotyped lentiviral vectors (LVs) for human (h) B-cell transduction following their adaptive transfer into an NOD/SCIDγc-/- (NSG) mouse. Results Upon B-cell receptor stimulation, BaEV-LVs transduced up to 80% of hB cells, whereas vesicular stomatitis virus G protein VSV-G-LV only reached 5%. Remarkably, BaEVTR-LVs permitted efficient transduction of 20% of resting naive and 40% of resting memory B cells. Importantly, BaEV-LVs reached up to 100% transduction of human plasmocytes ex vivo. Adoptive transfer of BaEV-LV-transduced mature B cells into NOD/SCID/γc-/- (NSG) [non-obese diabetic (NOD), severe combined immuno-deficiency (SCID)] mice allowed differentiation into plasmablasts and plasma B cells, confirming a sustained high-level gene marking in vivo. As proof of principle, we assessed BaEV-LV for transfer of human factor IX (hFIX) into B cells. BaEV-LVs encoding FIX efficiently transduced hB cells and their transfer into NSG mice demonstrated for the first time secretion of functional hFIX from hB cells at therapeutic levels in vivo. Conclusions The BaEV-LVs might represent a valuable tool for therapeutic protein secretion from autologous B cells in vivo in the treatment of hemophilia and other acquired or inherited diseases.

Efficient expression of bioactive murine IL12 as a self-processing P2A polypeptide driven by inflammation-regulated promoters in tumor cell lines.

Interleukin 12 (IL12) is a heterodimeric proinflammatory cytokine that has shown promise as an anticancer agent. However, despite encouraging results in animal models, clinical trials involving IL12 have been unsuccessful due to toxic side effects associated with its systemic administration, prompting investigation into new delivery methods to confine IL12 expression to the tumor environment. In this study we used the self-cleaving property of the 2A peptide to express both codon-optimized murine IL12 subunits (muIL12opt) as a self-processing polypeptide (muIL12opt-P2A). We cloned muIL12opt-P2A driven by different inflammation-induced lentiviral expression systems to transduce murine tumor cell lines commonly employed in syngeneic tumor models. We confirmed the inducibility of these systems in vitro and in vivo and demonstrated the successful expression of both IL12 subunits and the release of bioactive IL12 upon proinflammatory stimulation in vitro. Therefore, IL12 release driven by these inflammation-regulated expression systems might be useful not only to address the impact of IL12 expression in the tumor environment but also to achieve a local IL12 release controlled by the inflammation state of the tumor, thus avoiding toxic side effects associated with systemic administration.