Leukemia Inhibitor Factor (LIF) Inhibits HIV-1 Replication Via Restriction of Stat 3 Activation

Leukemia inhibitor factor (LIF) has been shown to potently inhibit HIV-1 replication in vitro and in human organ explant cultures. Furthermore, LIF activates the Jak/Stat signaling pathway with which many viruses, including HIV-1, interfere. We used CXCR4 and the LIF signaling receptor (gp130)-expressing cMAGI cells transfected with CD4, CCR5, and HIV-LTR-beta-galactosidase as a model system to investigate the potential involvement of Stat proteins in the anti-HIV-1 effect of LIF. Pretreatment with recombinant human (rh)LIF resulted in a significantly reduced uptake of HIV-1(BaL) , HIV-1(LAI), and SIVmac251 viral particles without affecting uptake of murine leukemia retroviral particles. HIV-1(BaL), HIV-1(LAI), as well as rhLIF selectively induced phosphorylation of Stat 3 but not Stat 1 or Stat 5. However, treatment of cMAGI cells with rhLIF prior to HIV-1 infection downregulated the HIV-1-mediated Stat 3 phosphorylation. In addition, peripheral blood mononuclear cells (PBMCs) transfected with Stat 3 siRNA prior to HIV-1(LAI) or HIV-1(BaL) infection produced significantly less HIV-1 p24 antigen as compared to nontransfected HIV-1(LAI) and HIV-1(BaL)-infected PBMCs. Thus, the Jak/Stat signaling pathway is important for the HIV-1 replication life cycle and rhLIF excerts its anti-HIV-1 activity by disrupting this signaling cascade.