A MYSTERIOUS protein extracted from pregnant women’s urine can slow the
progression of an AIDS-like disease in laboratory animals. It can also destroy
cells from tumours that afflict some AIDS patients and boost the production of
immune cells, virologist Robert Gallo of the University of Maryland in Baltimore
told the AAAS.
“We’re still in the early days. We don’t even know what the active component
is exactly,” says Gallo. “But we may have the basis here for a whole new avenue
of AIDS drugs.”
The winding route to the discovery started with a chance observation by Gallo
and his colleagues while they were studying Kaposi’s sarcoma, a skin cancer that
often claims the lives of patients with AIDS. Kaposi’s sarcoma is particularly
common in gay men with the disease, and is thought to be triggered by a herpes
The researchers grew the tumour cells in mice with crippled immune systems.
Soon nearly all the animals were overwhelmed by the cancer and died.
Surprisingly, the survivors were female mice that had become pregnant soon after
infection and were able to destroy the deadly cancer cells.
That led Gallo and his team to examine the anti-sarcoma activity of different
hormones that pregnant woman produce. Late last year, they announced that
partially purified commercial preparations of one particular hormone could kill
Kaposi’s tumours when it was injected into the skin lesions of human patients.
The hormone, called human chorionic gonadotropin (hCG), allows implantation of
the fertilised egg and subsequently helps to prevent miscarriage.
But when the researchers tried to improve the hormone’s effectiveness by
purifying it further, they found that it did not work. This was true whether
they purified the hormone from commercial sources or directly from pregnant
women’s urine. The partially purified hormone contains a smaller protein thought
to be a breakdown product of hCG and this seemed to be attacking the tumours.
Gallo says that the active molecule is a fragment of one protein chain that
makes up hCG. But the exact sequence of amino acids in the protein is still
Why women produce such a potent anticancer drug early in pregnancy is not
clear. “It must be something important to the early life of the embryo,” says
Gallo. One possibility is that the hormone fragment has a general protective
effect, stimulating the immune system and attacking viruses and other
microorganisms that might attack a developing embryo.
Indeed, the researchers have shown that the fragment has a range of desirable
activities appealing to embryos—as well as to drug designers who are
trying to develop new treatments for HIV.
The protein fragment stimulates the production of bone marrow cells which
give rise to immune and blood cells. It can also eliminate SIV, the monkey
equivalent of HIV, from infected macaques if given early enough. So far Gallo’s
team has not identified any toxic side effects associated with the compound.