Wilson da Silva, Sydney
TRIALS of a type of gene therapy that slices through the genetic material ofHIV and prevents it from multiplying have begun in Australia. Within a few months they should provide the first signs of whether the technique can halt the progression of AIDS.
Existing treatments try to reduce the amount of HIV in the body with a cocktail of anti-viral drugs. But researchers at Gene Shears, a biotechnology company in Sydney, will try to discover whether an immune system already under attack can be repaired from within.
Last week, Gene Shears announced that it had begun clinical trials of an engineered “ribozyme”—a molecule of RNA that behaves like an enzyme and cuts through a vital part of HIV’s genetic material. In laboratory tests, the ribozyme, called Rz2, halts replication of HIV inside CD4 cells. These are the white blood cells, or lymphocytes, that the virus commandeers at the outset of infection, converting them into factories turning out multiple copies of the virus.
Six pairs of identical twins are taking part in the trials at St Vincent’s Hospital, Sydney. One twin in each pair is HIV-positive, the other is negative. The team takes healthy lymphocytes from the uninfected twin, equips them with the gene that makes the ribozyme and injects them into the HIV-positive twin. The gene is carried into the lymphocytes on board a disarmed mouse leukaemia virus. This inserts the anti-HIV gene into human DNA, allowing the lymphocyte to create its own ribozyme.
Indications of how the armed cells are faring are expected in six months. Their survival will be the first sign that gene therapy can halt the progress of AIDS. “I’m very optimistic about it,” says David Cooper, head of the Centre for Immunology and HIV Medicine at St Vincent’s. “At worst we expect this technology to be complementary to existing therapies.”