FIG. 4.

Inhibition of Src kinases significantly reduces borrelial invasion of fibroblasts. Fibroblasts were infected with gfp-expressing B. burgdorferi strain ML23/pEW159 as indicated in the legends to Fig. 2 and 3. The inhibitors PP2 (A) and SU6656 (B) were added to final concentrations of 10 μM and 10 nM for 2 h prior to infection, respectively. The infected cells were processed, and B. burgdorferi was visualized as indicated in the legends to Fig. 2 and Fig. 3. Addition of the inhibitors did not affect fibroblast viability for the duration of the experiment (not shown). The extracellular and intracellular B. burgdorferi data shown 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 and without PP2 (P < 0.00001, in panel A) or with or without SU6656 (P < 0.001, in panel B).