NASHVILLE--Using a "hairpin ribozyme" gene, researchers
at the University of California, San Diego, School of Medicine
have managed to stop HIV infection in its tracks by dismantling
the virus's RNA.
"We've shown that therapeutic genes can be passed on from
parent cells to their offspring cells and that those progeny cells
will be protected against HIV infection," said Anthony Ho,
MD, PhD, speaking at the scientific sessions of the American Society
of Hematology (ASH) meeting.
Virus vectors used to insert a therapeutic gene into target cells
produce protection only for the lifetime of the cells that receive
the gene therapy dose. But when the hairpin ribozyme gene is inserted
into stem cells, via a standard viral delivery system, the progeny
of these ribozyme-transduced cells also express the hairpin ribozyme
gene, Dr. Ho noted.
When these treated cells were exposed in the lab to HIV, they
did not become infected, said Dr. Ho, professor of medicine and
director of stem cell transplantation, UCSD Medical Center.
The new treatment method, known as intracellular immunization,
is based on work by Flossie Wong-Staal, PhD, professor of medicine,
University of San Diego. She found that the hairpin ribozyme disables
HIV-1 by cleaving its RNA like a molecular knife.
In the experiment, the researchers extracted CD34+ cells from
human fetal cord blood and mobilized these cells by culturing
them with growth factors so that the final blood sample was comprised
of nearly 90% CD34+ cells. The hairpin ribozyme gene was inserted
into this line of cells, which then went on to produce a new generation
of macro-phage-like CD34+ cells that expressed the hairpin ribozyme
gene and successfully resisted HIV infection.