More than 35 million people around the world have been killed by HIV, the virus that causes AIDS. So, it’s hard to think that the same approach the virus uses to infect cells could also be used to help children battling a deadly immune system disorder. But that’s precisely what researchers at UC San Francisco and St. Jude Children’s Research Hospital are doing.
The disease the researchers are tackling is a form of severe combined immunodeficiency (SCID). It’s also known as ‘bubble baby’ disease because children are born without a functioning immune system and in the past were protected from germs within the sterile environment of a plastic bubble. Children with this disease often die of infections, even from a common cold, in the first two years of life.
The therapy involves taking the patient’s own blood stem cells from their bone marrow, then genetically modifying them to correct the genetic mutation that causes SCID. The patient is then given low-doses of chemotherapy to create space in their bone marrow for the news cells. The gene-corrected stem cells are then transplanted back into the infant, creating a new blood supply and a repaired immune system.
Unique delivery system
The novel part of this approach is that the researchers are using an inactivated form of HIV as a means to deliver the correct gene into the patient’s cells. It’s well known that HIV is perfectly equipped to infiltrate cells, so by taking an inactivated form – meaning it cannot infect the individual with HIV – they are able to use that infiltrating ability for good.
The results were announced at the American Society of Hematology (ASH) Annual Meeting and Exposition in Atlanta.
The researchers say seven infants treated and followed for up to 12 months, have all produced the three major immune system cell types affected by SCID. In a news release, lead author Ewelina Mamcarz, said all the babies appear to be doing very well:
“It is very exciting that we observed restoration of all three very important cell types in the immune system. This is something that’s never been done in infants and a huge advantage over prior trials. The initial results also suggest our approach is fundamentally safer than previous attempts.”
If the stem cell-gene therapy combination continues to show it is both safe and effective it would be a big step forward in treating SCID. Right now, the best treatment is a bone marrow transplant, but only around 20 percent of infants with SCID have a sibling or other donor who is a good match. The other 80 percent have to rely on a less well-matched bone marrow transplant – usually from a parent – that can still leave the child prone to life-threatening infections or potentially fatal complications such as graft-versus-host disease.