Geneticists were humbled by these barriers, but they were not stumped. A second wave of enthusiasm for gene therapy is now well under way, thanks to recent advances that suggest new strategies. This technique avoided triggering a general immune response and exploited the rapid division of tumor cells. Results from two other groups recently suggested that it might be possible to design gene therapies that altogether avoid viruses and their many drawbacks. Workers at the University of Chicago and at Vical , a biotechnology firm in San Diego, rolled a gene for erythropoietin into a circular DNA package called a plasmid.
Erythropoietin is a hormone that triggers the body to produce red blood cells.
In an article published October 1 in the Proceedings of the National Academy of Sciences , the Chicago group reported that simply injecting the naked DNA into the hindquarters of normal mice boosted their red blood cell counts by a third. Boosting blood-cell production does little good for patients whose blood cells are malformed, such as those of sickle cell anemics. The ultimate goal of gene therapy is not to compensate for genetic diseases but to erase them completely. Preliminary work published in the September 6 issue of Science offers a reason to hope that goal may be possible. A team led by Allyson Cole-Strauss and Kyonggeun Yoon of Thomas Jefferson University in Philadelphia experimented on cells containing a mutant gene that causes sickle cell anemia.