FIG. 3.

Inhibition of actin polymerization significantly reduces borrelial invasion of fibroblasts. Cytochalasin D was added to a final concentration of 10 nM for 2 h prior to infection of fibroblasts with ML23/pEW159. The infected cells were processed, and B. burgdorferi was visualized as indicated in the legend to Fig. 2. Addition of cytochalasin D did not affect fibroblast viability for the duration of the experiment (not shown). The data shown for extracellular and intracellular B. burgdorferi are the averages from 3 independent assays from >4,000 host cells analyzed per group per assay (total of >12,000 analyzed). Error bars depict standard deviation. Asterisks indicate a statistically significant difference in the internalization of B. burgdorferi in fibroblasts with or without cytochalasin D (P < 0.001).