FIG. 2.

Tropism and infectivity of SARS-S-bearing lentiviral pseudotypes. (A) Cellular tropism of SARS-CoV S pseudotypes. SARS-CoV S-mediated infection of a panel of common cell lines was assessed. For infection, 3 ng of p24-normalized pseudotypes carrying either the pantropic VSV G as positive control, no GP (pcDNA3) as negative control, or the SARS-CoV S GP was added to the cells followed by a 2-h centrifugation at 800 × g in order to concentrate the infectious material on the cells. After 72 h, cells were lysed and luciferase activity was determined in the cell extracts. Results of a representative experiment performed in quadruplicate are shown. Comparable results were obtained in at least three different experiments with independent virus stocks. (B) Relative infectivity of pseudotypes bearing VSV G, MLV GP, and SARS-CoV S. Huh-7 cells were infected with culture supernatants containing 1 ng of viral antigen, and luciferase activity was measured 3 days after infection. Results of a representative experiment carried out in quadruplicate are shown; comparable results were obtained in an independent experiment. (C) Efficiency of transduction of Huh-7 cells with p24-normalized GFP reporter viruses. Huh-7 cells were spin infected for 2 h with 25 ng of pseudotypes bearing VSV G or SARS-CoV S or control pseudotypes lacking an envelope protein (pcDNA3). After 72 h, cells were fixed and analyzed by immunofluorescence. Results of a representative experiment carried out in quadruplicate are shown. The results were confirmed in two independent experiments.