Figure 3

Holistic view of bartonellae interactions with endothelial cells and erythrocytes. Exploitation of vascular endothelial cells by bartonellae involves binding to the cell surface via BadA/Vomps proteins as well as VirB/D4 and possible other adhesions as Omp43/pap31. VirB/D4 and its effectors mediate massive rearrangements of the actin cytoskeleton, resulting in the formation of large bacterial aggregates by the invasome structure as well as inhibition of apoptosis leading to enhanced endothelial cell survival. The mechanisms of the passage of Bartonella spp. from endothelial cells to erythrocytes is unknown however, it appears that before infecting erythrocytes, the bacteria is free in the blood. Adherence to erythrocytes appears to be mediated by Trw (for most Bartonella species) or by flagella (for B. bacilliformis and the lineage 2 species). A erythrocyte is usually infected by a single bacterium, which once inside, replicates in a membrane-bound compartment then persists throughout the lifespan of the red blood cell. During this process, proteases IalA and CtpA are suspected to degrade misfolded proteins and to protect bacteria against stress.