A new type of gene therapy that injects a modified version of HIV into special immune cells appears to hinder the AIDS virus' ability to replicate, according to a new study.
In the five HIV-infected patients in the study, the amount of virus remained stable or decreased. The number of T cells -- immune cells that fight the virus -- held steady or increased in four of five patients.
Tests showed no dangerous, mutated forms of the genetically modified virus in the body, said Bruce Levine, lead author of the paper published Tuesday in the Proceedings of the National Academy of Sciences.
Levine, an immunologist at the University of Pennsylvania, said none of the patients, who received the treatment two to three years ago, had developed leukemia or other problems that had afflicted patients in other gene therapy studies.
"Although gene therapy has had setbacks ... this shows the slope of steady progress we're making," he said.
The Penn group collaborated with scientists at Virxsys Corp., a Gaithersburg, Md., biotechnology firm that developed the modified version of HIV, called VRX496.
The study was funded by Virxsys, the National Institute of Allergy and Infectious Disease and the Abramson Family Cancer Research Institute.
Levine's group gathered T cells from five subjects who had failed to improve using combination drug treatments. The cells were mixed with the altered virus, which was designed to attach itself into the genetic material of the T cell and block replication of the full HIV genome.
"We used the modified HIV as a Trojan horse to deliver something that throws a monkey wrench in the natural replication process," Levine said.
Researchers reinfused the patients with about 10 billion modified T cells.
In one subject, the treatment cut the amount of virus in his blood by a factor of about 50 at the end of 12 months.
"It's a promising start and worthy of trials to figure out if it's going to work," Levine said.