Abstract Text: Primary immunodeficiencies (PIDs) are a group of inherited, monogenic disorders characterized by recurrent, severe, chronic infections, autoimmunity, and inflammation. The most common PID to affect males is X-linked Agammaglobulinemia (XLA), which is caused by the inactivation of the Bruton tyrosine kinase (BTK) gene. Without treatment, XLA patients do not survive past childhood. The mainstream treatment is immunoglobulin replacement therapy (e.g., intravenous, or subcutaneous delivery of immuno-globulin), a life-long therapy that begins soon after diagnosis. However, it is not curative, leaving patients at risk of developing severe respiratory tract infections and chronic lung disease. Lentiviral- and gamma retroviral-based gene addition strategies have been attempted, but they are not feasible therapies for XLA since overexpression of the BTK gene is known to drive B cell malignancies. For these reasons, we are developing a ‘universal gene targeting-based correction’ as a novel therapy for XLA, where the underlying genetic mutation is corrected in a patient’s hematopoietic stem and progenitor cells (HSPCs), in support of BTK gene endogenous levels of regulation and protein expression. We have developed highly efficient gene-targeting tools and achieved over 50% allelic modification at the BTK locus, using a therapeutic BTK codon-optimized (co)cDNA, demonstrating the feasibility of this approach. In upcoming studies, I plan to use OMICs–cytometry by time of flight, single-cell RNA sequencing, and Assay for Transposase-Accessible Chromatin–in addition to xenotransplantation studies to characterize the BTK-modified cells for the safety and efficacy of this new therapy and to potentially generate new insight into the pathophysiology of XLA disease.
