FIG. 1.

Modulation of viral infection by lectin expression. (A) Characterization of cell lines expressing lectins upon induction. The indicated cell lines were generated by stable transfection of T-REx cells (Invitrogen). Lectin expression was induced by doxycycline (0.1 μg/ml) and quantified by fluorescence-activated cell sorting with a monoclonal antibody directed against a C-terminal AU-1 antigenic tag. Control cells are shown in light grey, uninduced cells are shown in dark grey, and doxycycline-induced cells are shown in black. (B) Infection of lectin-expressing cell lines. Lectin expression was induced with doxycycline, and the indicated cell lines were infected with lentiviral pseudotypes bearing the indicated glycoproteins. The lentiviral genome encodes the luciferase gene which is expressed under control of the viral promoter upon integration of the viral genome into the cellular chromosome. Luciferase activity in cell lysates was quantified 3 days after infection. Infection of lectin-expressing cells is presented relative to infection of T-REx control cells. Upon infection of control cells with pseudotypes bearing SARS-CoV S, MARV GP, VSV-G, or no GP, 548, 2,125, 2,197 and 35 cps were measured. A representative experiment is shown; similar results were obtained in two independent experiments. Error bars indicate standard deviations (SD). EBOZ, EBOV Zaire subspecies. (C) Inhibition of infection of DC-SIGN-expressing T-REx cells. DC-SIGN-expressing and control T-REx cells were induced with doxycycline, preincubated for 30 min with the indicated antibodies or mannan at a final concentration of 20 μg/ml, and infected with SARS-CoV S-bearing pseudotypes. Luciferase activity was assessed 3 days after infection. The results are shown relative to inhibition with control murine IgG; similar results were obtained in an independent experiment.