New approach to HIV treatment
destroying the virus as it enters host cells. The treatment is
based on the genetic manipulation of the immune cells that HIV
infects to enable them to destroy the virus.
Thomas Merigan of Stanford University School of Medicine, one of the scientists who developed the concept, is seeking volunteers for a study to test the approach, which will involve removing the patient's stem cells - the ones in the bloodstream that form the different immune system cell types that HIV infects - and inserting a gene that produces an HIV-obliterating enzyme.
"This is a broad-spectrum treatment that could integrate well with other therapies as the disease progresses, as it will in all patients eventually," said Merigan, who is collaborating with other researchers at University of California, Los Angeles, and St Vincent's Hospital in Sydney, Australia. It is being funded by Johnson & Johnson.
The strategy relies on the fact that the genetic information of HIV is encoded in RNA rather than DNA. Enzymes called ribozymes can chew up RNA at very specific sites, rendering it inactive. If a ribozyme specific to HIV RNA were present inside the cells that the virus infects, then it could constitute a first-line defense against the invasion.
And even if HIV did make it into the cell and replicated, the ribozyme could potentially cleave the HIV RNA at various steps during the virus' life cycle.
Merigan said: "We know there is a sufficient risk that patients will eventually need more than the 19 drugs currently available."
A total of 70 patients will be enrolled at three sites for this stage of the testing. The participants will be randomly assigned to receive either the ribozyme gene therapy or a dummy gene. J&J Research produces the reagents used for introducing ribozyme into the blood stem cells.
Merigan said that similar studies testing the strategy of using gene therapy in more than 1,200 patients have proven the technique to be safe. The safety studies for the current trial looked at a total of 14 patients and found no safety concerns.
Merigan discussed a scare a few years ago when two babies undergoing gene therapy developed leukaemia, which was successfully treated. He noted that the HIV trial had been delayed for two years while the trial's safety design was examined by the National Institutes of Health, the U.S. Food and Drug Administration and local review boards.
The verdict was that the immune system of adults with HIV differs greatly from that of babies, whose immune systems are not fully formed, and that they should not face the same risk.
