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Abstract

Introduction: Bartonella bacilliformis is a neglected bacterialpathogen and the causative agent of the biphasic Carrion"s disease, leading to hemorrhagic fever (Oroya fever) and Peruvian warts. The disease is restricted to the Peruvian Andes. Transmission is mediated by the sand fly Lutzomyia verrucarum.
Aims: Little is known about the infection mechanisms and the underlying pathogenicity factors of B. bacilliformis. Therefore, infection models need to be established to analyze the pathogenicity mechanisms. Cellular microbiology methods should help to understand the complex interactions of B. bacilliformis and its host (e.g. host cell tropism, cell adhesion, invasion and host cell response).
Materials and Methods: HUVECs, HeLa-229 cells and erythrocytes were co-cultured with B. bacilliformis (strains: ATCC35686, JB584, friendly gift of Prof. M. Minnick, Montana, USA). Bacteria and infected cells were analyzed via immunofluorescence microscopy and electron microscopy. Host cell response upon B. bacilliformis infection was determined on transcriptional (qPCR) and translational level (ELISA) for vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8).
Results: Due to the fact that the growth conditions of B. bacilliformis and their human host cells differ in terms of culture media and cultivation temperature (temperature optimum of B. bacilliformis: 27C°) experimental infection conditions were adapted. B. bacilliformis was able to invade HUVECs more efficient than HeLa-229 cells. Likewise, the gene induction of IL-8 and VEGF was significantly more increased in endothelial cells than in epithelial cells. In contrast, significant quantifiable secretion of VEGF was only detected in infected HeLa-229 cells. Furthermore, infection of human erythrocytes resulted in considerable movement and agglomeration of erythrocytes compared to uninfected controls.
Conclusion: Although cell tropism to endothelial cells is described extensively in literature our investigations show no considerable effect of B. bacilliformis infection on epithelial and endothelial cells. These results may point to the fact, that B. bacilliformis might engage unknown mechanisms or other cells e.g. erythrocytes to interact with these cells. The role of flagellin and the trimeric autotransporter adhesion BrpA need to be elucidated in detail to understand B. bacilliformis pathogenicity.