Potential Role of Bartonella sp. in Vasoproliferative Disorders in Dogs

Bartonella sp. are highly fastidious, vector borne zoonotic agents. Bartonella sp. cause persistent intraerythrocytic bacteremia in reservoir hosts whereas endothelial cells are the major target cells in incidental hosts. Three species of Bartonella are associated with vasoproliferative disorders including verruga peruana ( B. bacilliformis), bacillary angiomatosis (B. henselae, B. quintana) and peliosis hepatis (B. henselae). Bartonella sp. induces proliferation of endothelial cells by both direct mitotic stimulation and by inhibiting endothelial cell apoptosis.;Commonly used diagnostic methods for Bartonella include liquid enrichment cultures, serology, polymerase chain reaction (PCR), immunohistochemistry, silver staining and fluorescent in situ hybridization (FISH). We developed fluorescent in situ hybridization probes specific for Bartonella sp., B. henselae and B. vinsonii subsp. berkhoffii. We tested paraffin embedded tissues with these FISH probes and compared the results with PCR, Warthin-Starry silver staining, immunohistochemistry and FISH with the universal probe Eub338. Even though the sensitivity of these probes were lower compared to the other techniques, it may be useful for the detection and localization of Bartonella sp. in tissues when combined with other diagnostic techniques like PCR.;Paraffin embedded tissues are readily available and highly useful for diagnosis of infectious diseases and retrospective studies. PCR is a highly sensitive and specific technique for diagnosis of bartonellosis from blood and tissues. Extreme care should be taken to avoid contamination or carryover of DNA between samples. This is especially important in case of paraffin embedded tissues, since there are many steps involved in the preparation and processing of the paraffin blocks which could be potential sources of DNA carry over. We found presence of Bartonella sp. DNA on different parts of the microtome, necropsy room table and in the paraffin from the tissue processor. Our results emphasize the need of extreme care and proper controls when paraffin embedded tissues are used for the diagnosis and research studies.;B. bacilliformis, B. henselae and B. quintana are known to induce vasoproliferative disorders in human beings and animals. Here we present evidence that B. vinsonii subsp. berkhoffii also has ability to induce vasoproliferation. B. vinsonii subsp. berkhoffii was isolated and/or detected from various vasoproliferative disorders from humans and animas. We also demonstrated that B. vinsonii subsp. berkhoffii induces VEGF production in HeLa 229 cells in a dose dependent manner. Taken together these results strongly support the addition of B. vinsonii subsp. berkhoffii to the list of bartonellae capable of inducing vasoproliferation.;Next, we performed a case control study to detect the molecular prevalence of Bartonella, Babesia and hemotropic Mycoplasma sp. in splenic biopsy tissues from dogs with splenic fibrohistiocytic nodules (FHN), hemangiosarcoma (HSA) and lymphoid nodular hyperplasia (LNH). The prevalence of Bartonella sp. DNA was higher in FHN and HSA when compared to LNH. Prevalence of Bartonella sp. was significantly higher when compared to the prevalence of Babesia and Mycoplasma sp. in both FHN and HSA whereas no significant difference was noted in the prevalence of the three genera tested in LNH group. Our studies indicate a plausible role of Bartonella sp. in pathogenesis of splenic FHN and HSA.;We studied the effect of Bartonella sp. infection in human brain vascular pericytes in vitro. We demonstrated invasion of pericytes by B. henselae. Bartonella decreased the proliferation of pericytes when compared to uninfected controls. Bartonella did not have any significant effect on the apoptosis of pericytes. Bartonella induced the production of VEGF production by pericytes. Our results indicate that B. henselae can infect pericytes and induce production of VEGF from pericytes which may act in turn help in the proliferation of the endothelial cells in a paracrine manner.