FIG. 2.

Borrelia burgdorferi invades immortalized and primary fibroblasts, as well as primary endothelial cells. Fibroblasts (L929 or NHDF) or endothelial cells (HUVECs) were infected with ML23/pEW159 at an MOI of 5 for 18 h. Extracellular B. burgdorferi bacteria (B.b.) were detected with anti-OspA coupled with an Alexa Fluor 594 secondary antibody. 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 of internalization in NHDF and HUVECs relative to L929 cells (P < 0.001).