HIV-positive adults in California are participating in a
clinical trial that combines stem cell technology and
genetic engineering to create what researchers call a
"parallel immune" system to fight the
disease, the San Francisco Chronicle reports.
About half of the study participants have received
injections of their own blood cells that have been
engineered to contain a gene that blocks HIV. The goal
is to create an array of long-lived cells that will fight
HIV and outlast natural blood cells that are targeted by the
The key to the
therapy is inserting an engineered enzyme called ribozyme,
which does not exist naturally in the body, into immune
system cells. The enzyme destroys one of HIV's
key genes when the virus tries to copy itself,
essentially preventing HIV from spreading in the body.
Researchers attach the enzyme to an engineered mouse virus
and expose human stem cells culled from bone marrow
and the bloodstream to the virus. The mouse virus
carries the enzyme into a cell, where it becomes part
of the cell's natural machinery and fortifies it
against any attempts by HIV to infect it and begin
making viral copies. The stem cells are then
reinserted into the donor's body, where they begin
making numerous copies of immune system cells that are
resistant to HIV.
participants must sit through two eight-hour sessions in
which their blood is filtered to isolate the stem
cells. Once the stem cells are removed, they are
exposed to the ribozyme-carrying mouse virus, and
three days later are injected back into the donors.
Ronald Mitsuyasu of the University of California, Los
Angeles's Center for Clinical AIDS Research and
Education says that while he doesn't think the
approach will eventually replace standard
antiretroviral therapy, it could be useful for HIV patients
resistant to anti-HIV medications or those
experiencing AIDS-related complications.
trial's preliminary results will be reported in
clinical trial is being conducted by a research company in
Sydney, Australia, that is owned by Johnson & Johnson.