Gene therapy, a promising clinical approach to treat patients with a range of inherited diseases, often uses vectors derived from lentiviruses to insert a correcting genetic sequence into the patient’s stem cell chromosomes. While this type of treatment can provide long-term cures for inherited diseases, vectors from these viruses can also inadvertently activate cancer-causing genes because of the way they stitch or “integrate” the therapeutic DNA with human DNA. Avoiding these unwanted integrations while retaining the correcting gene has been challenging.
Researchers at the Papé Family Pediatric Research Institute at Oregon Health & Science University recently developed a new gene delivery vector that safely anchors its DNA within the cell nucleus and remains in dividing cells without insertion within the chromosomes. The floating lentiviral vector episomes are anchored and persist in rapidly dividing tissue culture cells for more than 100 rounds of cell divisions. To do this, the researchers added a human DNA fragment called S/MAR (Scaffold/Matrix Associated Region) to the vector to help it replicate safely during cell division while also remaining in the cell nucleus without integration. Because the vector they created acts like an anchor, they named it “anchored non-integrating lentiviral vector,” or AniLV for short.
The study, recently published in Nucleic Acids Research, by Santhosh Chakkaramakkil Verghese, Ph.D.; a postdoctoral fellow in the lab of Peter Kurre; Natalia Goloviznina, a research assistant; and co-authors illustrates the ability of this new anchoring, but non-integrating lentivector to persist in mouse bone marrow stem cells.
What’s next? Dr. Kurre’s team is planning to use this anchoring lentiviral vector to improve gene transfer to stem cells for a Fanconi Anemia mouse model. The goal is to demonstrate the therapeutic approach to genetically correct the hematopoietic failure that affects Fanconi Anemia patients while the episomes safely persist in the rapidly dividing bone marrow stem cell pool.
This project was done in collaboration with Dr. Hans Lipps at the University of Witten/Herdecke, Germany. The research was funded in part through generous support by the Friends of Doernbecher and extends the team’s gene therapy effort under the National Institutes of Health grant (R01HL90765).
Image caption: An illustration and microscopic image of anchoring non-integrating lentiviral vector episome located near chromosomes (blue) within the nucleus. Florescence In situ hybridization (FISH) experiments by Ms. Goloviznina show the episome vector DNA (Green) attachment. Absence of vector DNA within the chromosomes suggests absence of integrated vector DNA in these cells.