Hematopoietic stem cell gene therapy for the treatment of X-linked agammaglobulinemia.
Publication Year:
2025
PubMed ID:
40917692
Public Summary:
X-linked agammaglobulinemia (XLA) is an inherited immune deficiency where a gene, BTK, needed for B cells to develop and make protective antibodies is defective. XLA patients are very susceptible to infections due to the absence of antibodies and are treated with immunoglobulin replacement therapy, receiving pooled antibodies from other donors to provide protection. Besides the high costs and inconvenience of weekly-monthly immunoglobulin infusions, patients with XLA may still develop severe infections of the sinuses, middle ears and airway, the GI tract and the brain. We have developed a gene editing method to insert a normal copy of the BTK gene into a patient's blood-forming stem cells to support their production of normal functional B cells capable of making a diverse spectrum of protective antibodies. In a mouse model of BTK, we showed that insertion of a normal BTK gene into their blood-forming stem cells did enable the production of B cells after the gene-corrected stem cells were transplanted into XLA mice. After gene therapy, the mice produced normal levels of antibodies and responded to a vaccine with production of specific antibodies. These studies demonstrate disease-modifying activity and the prospect of direct benefit that wold allow pediatric patients to be enrolled into future clinical trials of blood-forming stem cell gene therapy for XLA.
Scientific Abstract:
X-linked agammaglobulinemia (XLA) is a rare inborn error of immunity caused by loss-of-function mutations in the gene encoding Bruton's tyrosine kinase (BTK). XLA patients lack mature B cells and have negligible antibody levels, leaving them susceptible to recurrent bacterial and chronic viral infections. Autologous hematopoietic stem cell gene therapy with gene-corrected HSC may serve as a promising treatment of XLA; this therapy would provide a one-time cure and would replace lifelong immunoglobulin replacement therapy. Due to the requirement of strict physiological regulation of BTK gene expression, a site-specific editing strategy was designed to insert a BTK cDNA transgene directly into its endogenous locus. To study the effectiveness of this therapy, murine lineage-negative hematopoietic cells from a murine model of XLA were edited using CRISPR-Cas9/rAAV6 then transplanted into recipient XLA mice. Myeloablated XLA mice that received transplantation of Btk-corrected Lin- cells displayed high levels of engraftment, significant increases in their B cell levels, increased production of various immunoglobulins, improved B cell development in the bone marrow, increased B cell receptor diversity, and the ability to produce antigen-specific antibodies following immunization. Collectively, we have modeled a gene therapy strategy in a disease model of XLA and extensively validated the site-specific genome editing approach.