Inhibition of HIV replication by the plasminogen activator is dependent on vitronectin-mediated cell adhesion

Abstract: Urokinase-type plasminogen activator (uPA), an inducer of macrophage adhesion, inhib-its HIV-1 expression in PMA-stimulated, chroni-cally infected U1 cells. We investigated whether uPA-dependent cell adhesion played a role in uPA-dependent inhibition of HIV-1 replication in these cells. Monocyte-derived macrophages (MDM) were generated from monocytes of HIV-infected individ-uals or from cells of seronegative donors infected acutely in vitro. U1 cells were stimulated in the presence or absence of uPA in standard tissue cul-ture (TC) plates, allowing firm cell adhesion or ultra-low adhesion (ULA) plates. Moreover, U1 cells were also maintained in the presence or ab-sence of vitronectin (VN)-containing sera or serum from VN/ mice. Virus production was evaluated by RT activity in culture supernatants, whereas cell adhesion was by crystal violet staining and optical microscopy. uPA inhibited HIV replication in MDM and PMA-stimulated U1 cells in TC plates but not in ULA plates. uPA failed to inhibit HIV ex-pression in U1 cells stimulated with IL-6, which induces virus expression but not cell adhesion in TC plates. VN, known to bind to the uPA/uPA receptor complex, was crucial for these adhesion-dependent, inhibitory effects of uPA on HIV ex-pression, in that they were not observed in TC plates in the presence of VN/ mouse serum. HIV production in control cell cultures was increased significantly in ULA versus TC plates, indicating that macrophage cell adhesion per se curtails HIV replication. In conclusion, uPA inhibits HIV-1 rep-lication in macrophages via up-regulation of cell adhesion to the substrate mediated by VN. J. Leu-koc. Biol. 82: 000–000; 2007. Key Words: inflammation AIDS acute infection chronic in-fection amino-terminal fragmen