Gene Therapy for HIV

A new form of gene therapy designed to block HIV has been administered to three people with drug-resistant strains of HIV. An article on the therapy was published in the May 15, 2004, issue of New Scientist.

The new therapy was developed by Virxsys Corp. (Gaithersburg, MD, USA). The company's idea was to use a modified form of HIV to deliver an "antisense” gene to the immune cells that HIV infects. This was to be integrated into the cells' genome, and stays there until a cell is infected. Then it is switched on and produces RNA complementary to the "sense” RNA encoding a viral protein. In theory, the RNAs should bind together, blocking viral replication. Laboratory trials of the therapy showed that viral replication was at least 100 times lower in the treated cells.

In July 2004, the company began treating patients by filtering immune cells from their blood, exposing the cells to very low doses of the modified virus, and then putting them back into the body. Like existing antiretroviral drugs, the approach will not completely eliminate HIV from the body. However, because the antisense RNA fragment is very long, HIV should never be able to mutate enough to become resistant to it, according to Boro Dropulic, Ph.D., chief scientific officer of Virxsys, in a presentation at the RNAi 2004 meeting in Boston (MA, USA) in May 2004.

It is the first time that this therapy with modified HIV has been attempted and Dr. Dropulic says the results so far are encouraging. Richard Sutton, of Baylor College of Medicine (Houston, TX, USA), however, is skeptical. He points out that many problems inherent in gene therapy for HIV have led others to give up on the approach. "A lot of people, including large pharma, have seen the writing on the wall,” he noted.



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