FIG. 4.
Soluble Sca2 protein inhibits rickettsial invasion. (A) Monolayers of HeLa cells were incubated with 1 μM soluble GST or GST-Sca234-794 protein for 20 min at 37°C and 5%CO2 prior to infection with. E. coli BL21(DE3) expressing pSca2-200. BL21(DE3) harboring pET-22b was used as a negative control. Bacterial invasion was assessed as described in Fig. 3B. (B) Vero cell monolayers seeded at 90% confluence were incubated with 8 μM GST or GST-Sca234-794 protein prior to infection with R. conorii for 30 min. Total rickettsial association and intracellular bacteria were enumerated by differential immunofluorescence microscopy. *, P < 0.05. The data presented are representative of at least two independent experiments. The error bars represent the standard deviation from the average in these experiments.