Leukemia inhibitory factor inhibits HIV-1 replication and is upregulated in placentas from nontransmitting women

The placenta may play a critical role in inhibiting vertical transmission of HIV-1. Here we demonstrate that leukemia inhibitory factor (LIF) is a potent endogenous HIV-1-suppressive factor produced locally in placentae, In vitro, LIF exerted a potent, gp130-LIFR beta -dependent, HIV coreceptor-independent inhibition of HIV-1 replication with IC50 values between 0.1 pg/ml and 0.7 pg/ml, depending on the HIV-1 isolate. LIF also inhibited HIV-1 in placenta and thymus tissues grown in ex vivo organ culture. The level of LIF mRNA and the incidence of LIF protein-expressing cells were significantly greater ill placentae from HIV-1-infected women who did not transmit HIV-1 to their fetus es compared with women who transmitted the infection, brit they were not significantly different from placentae of uninfected mothers. These Endings demonstrate a novel pathway for endogenous HIV suppression that may prove to be an effective immune therapy for HIV infection.