A mystery protein in pregnant women’s pee may wipe out HIV, said Dr. Robert Gallo in April’s Nature Medicine. A chance observation in a 1995 Kaposi’s sarcoma (KS) study led the HIV codiscoverer’s team to find a new function for human chorionic gonadotropin (hCG), a hormone produced during the first trimester of pregnancy. When male and female mice injected with KS cells were put in the same cage by mistake, those that didn’t develop KS had one thing in common—they were females that got pregnant soon after the injection. That led Gallo to try hCG in PWAs. Surprise! The hormone not only shrank KS tumors, it also reduced the HIV in several patients’ blood.

Gallo now cites “hCG-associated factor,” or HAF, as responsible, and said it appears to inhibit viral replication in CD4 cells. The best news? HAF may encourage the growth of red and white blood cells. Once the mystery protein is identified, it will be synthesized and tested in animals and people. But a Nature Medicine editorial noted, “This is not without problems—the only known source is first-trimester human urine and it took 40 liters (42.4 quarts) just to get this far.”