Genetic therapies have been teetering on the brink of success for decades, it seems, only to fail to meet original expectations. In a tragic instance in 1999, a young man named Jesse Gelsinger became the first person to die as a result of gene therapy when he developed a severe allergic reaction to the virus used as the vector, or carrier, of the corrected gene. The fallout from his death led to suspensions and reevaluations of programs and new guidelines and requirements being put in place.
The Gelsinger case was mentioned in a recent episode of NOVA Wonders, a new series that showcases cutting edge scientific research. The episode entitled “Can We Make Life?” featured segments about a program to short-circuit Lyme disease on Nantucket Island by altering the genes of the mouse that carries the bacteria so that it will no longer be infected. There was also a segment reminiscent of Jurassic Park, in which a scientist discussed bringing back the woolly mammoth by taking DNA decoded from remains and inserting it in elephant embryos. The pros and cons of such work were discussed–the scientist working on Nantucket Island is treading very carefully and making sure he has the approval of the citizens before moving forward, and while there are questions about whether we should attempt to revive the woolly mammoth, it is possible that genetic engineering could allow us to conserve species that might otherwise go extinct.
But along with these possibilities, one marvelous result was shown: a treatment for cerebral adrenoleukodystrophy, or ADL, an X-linked disease in which the myelin sheaths of nerves are progressively damaged. There are several variations, or phenotypes, of this disease. The variation discussed in the episode primarily affects boys. It presents in early childhood as inflammatory lesions in the brain–this damage leads to progressive deterioration and death. The disease has been treated by blood stem cell transplant followed by chemotherapy. But a suitable donor is needed for this treatment, and they are not always available.
In the segment about treatment, seventeen boys were enrolled in a gene therapy program. First, stem cells were collected from the boys’ blood; the boys then underwent chemotherapy to ready their bone marrow. An inactivated form of the HIV virus was used to deliver the healthy gene to the stem cells, which were then reintroduced. In the end, the fifteen boys who remained in the trial and completed the treatment were apparently cured. Doctors sounded hopeful that treatments for hundreds of diseases may now be within sight, if not yet within their grasp.
I hope so.
I’ve enjoyed other episodes of NOVA Wonders about dark matter (“What is the Universe Made Of?” and AI (“Can We Build a Brain?”) The presentation can seem a little pop-science at first, but that sense faded as the discussions became more involved. The episodes can be watched on the PBS .org website, along with supplemental videos containing additional information. A sciencey rabbit hole, in other words.
Image: Depositphoto/vector by blueringmedia