UCLA researchers in the Department of Microbiology, Immunology and Molecular Genetics have developed a novel method to produce short lentiviral vectors with tissue-specific expression, with a primary focus on lentiviral vectors for treating sickle cell disease and other disorders of hemoglobin.
Sickle cell disease (SCD) is one of the most common monogenic disorders worldwide and is a major cause of morbidity and early mortality. SCD is cause by a single amino acid change in β-globin which leads to hemoglobin polymerization and red blood cell sickling. Although SCD is well characterized, there is still no ideal long-term treatment. Current therapies are based on induction of fetal hemoglobin to inhibit polymerization of sickle hemoglobin or transfusions to reduce the percentage of sickle hemoglobin. Stem cell transplantation is a promising technique but its reliance on a sibling donor significantly limits its widespread use. Transplantation of allogeneic cells is high risk due to graft-versus-host disease. Recently, gene therapy has emerged as a potential treatment, with lentiviral vectors as gene delivery modalities showing the most promise. Unfortunately, current β-globin expression vectors suffer from low vector titer and sub-optimal gene transfer, limiting the advancement of this gene therapy to the clinic.
UCLA researchers have developed novel LVs for the treatment of SCD. These vectors are considerably smaller, up to half the number of base pairs of previous examples. Shorter vectors have higher titer, more complete packaged genomes, and better infectivity. Administration of early versions of these vectors resulted in 18.5% of total hemoglobin tetramers at week 20 (more than 10% provides therapeutic effect) in a mouse model of SCD. These optimized and shortened LVs with erythroid-specific enhancers, provided up to a 10-fold higher titer with superior gene transfer to hematopoietic stem cells while retaining robust expression levels. These enhanced vectors are particularly important in clinical situations where poor gene transfer to hematopoietic stem cells is an issue. Translation of this LV-based gene therapy to the clinic would be facilitated by lower costs due to higher titer and gene transfer. The methods developed in order to design these new shorter LVs can be translated to many other untreatable, chronic diseases.
The enhanced β-globin-expressing lentiviral vector demonstrated superior transduction of hematopoietic stem cells (human and mouse) and has been validated in in vivo models of Sickle Cell Disease. Administration of early versions of these vectors resulted in 18.5% of total hemoglobin tetramers (more than 10% provides therapeutic effect).
DNA enhancers, gene therapy, transduction, reporter assay, transgenes, cell-type specific, gene transfer, hemoglobinopathies, sickle cell disease, ß-thalassemia, lentiviral vector, erythroid cell, hematopoietic stem cell