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Bartonella bacilliformis, a gram-negative, flagellated, motile bacterium, is the etiologic agent of verruca peruana. It is found within the verruca, where it can form large cytoplasmic (Rocha-Lima) inclusions in endothelial cells. Previously, an activity has been described in homogenates of B. bacilliformis that in vitro increases the proliferation of endothelial cells and their production of tissue-type plasminogen activator (t-PA) and in vivo is angiogenic. The aim of the present study was to determine if live B. bacilliformis similarly stimulated endothelial cells and produced the Rocha-Lima inclusion. By measuring proliferation of cells and the production of t-PA in vitro, it was found that the live bacteria increased both parameters in a fashion similar to the homogenates of B. bacilliformis. Interaction between the bacteria and endothelial cells appeared to be necessary for proliferation. On electron microscopy, bacteria penetrated the endothelial cell within 1 h, forming a small membrane-bound inclusion. By 12 h, a large membrane-bound inclusion, similar to the Rocha-Lima inclusion, containing numerous bacteria was present. These data provide further evidence that B. bacilliformis has an angiogenic activity and that the bacteria are at least in part responsible for the vascular proliferation of the verruca.

Bartonellosis, a biphasic disease caused by motile intracellular bacteria, produces in its tissue phase a characteristic dermal eruption (Verruga peruana) resulting from a pronounced endothelial cell proliferation. Bacteria are found in the interstitium and within the cytoplasm of endothelial cells (Rocha-Lima inclusion). The aim of this study was to determine if Bartonella bacilliformis produce a substance(s) that might be responsible for the vascular proliferation seen in the Verruga. This was assessed in an in vitro system using human endothelial cells and measuring proliferation as well as production of tissue type plasminogen activator after exposure to the endothelial cultures to B. bacilliformis extracts. Our results indicate that B. bacilliformis possess an activity that stimulates endothelial cell proliferation up to three times that of control. The factor(s) is specific for endothelial cells, heat sensitive, larger than 12 to 14 kd, not enhanced by heparin, has no affinity for heparin, and is precipitated by 45% ammonium sulfate. In addition, the B. bacilliformis extracts stimulate production of t-PA antigen in a concentration-dependent fashion. This activity is also heat sensitive and not lost after dialysis (12 to 14 kd). B. bacilliformis extracts, however, do not increase the production of plasminogen activator inhibitor. It was also determined that B. bacilliformis extracts stimulate the formation of new blood vessels in an in vivo model for angiogenesis. These results describe a bacterial factor(s) that stimulates two important steps in the development of new blood vessels in vitro, as well as the formation of new blood vessels in vivo. Determining the mechanism of action, combined with a complete characterization of this factor(s), may help in understanding the pathogenesis not only of the Verruga and angiogenesis in general but also the recently described Cat-Scratch-associated epithelioid hemangiomas in patients with AIDS and Kaposi sarcoma.