HIV Blocking Protein Found in Placenta

A protein factor found in human placentas blocks HIV in laboratory studies and may be what naturally protects most fetuses from acquiring HIV when the woman is infected, researchers announced this week at the 8th Conference on Retroviruses and Opportunistic Infections in Chicago, Newsday reports. Dr. Bruce Patterson of Children's Memorial Hospital in Chicago, together with researchers from Northwestern University and the Karolinska Institute in Sweden, found in an analysis of 22 placentas that leukemia inhibitory factor, or LIF, may be the "naturally occurring protective ingredient" that keeps 66% of newborns from acquiring HIV from HIV-positive pregnant women, "even in the absence of drugs such as AZT." Patterson and his associates analyzed 22 placentas, 14 placentas from HIV-positive women who gave birth to HIV-negative infants, five placentas from infected women whose infants tested positive for the virus and three placentas from uninfected mothers. They found LIF present in all of the placentas, but levels of the protein were highest in HIV-positive women who gave birth to uninfected infants. The researchers treated placental cultures with "dozens of HIV strains" and found that when they added "minute quantities of LIF to the cultures, HIV replication was blocked." LIF's role in the body is "unknown," but it attaches itself to placental cells and "some types of immune system macrophages found in men and women." The bond formed by LIF and the cells releases other "unidentified chemicals" that block HIV from penetrating cells, leaving the virus unable to replicate and causing it to die. The protein "appears to be highly potent" in doses "a thousand fold smaller" than those of most current antiHIV drugs. Researchers hope to use LIF to help the "body's own defense mechanisms ... in the fight against AIDS" (Garrett, Newsday, 2/9).