PI: Annette Vergunst
Margarida Castro Gomes
Burkholderia cepacia complex infections
Bacteria belonging to the Burkholderia cepacia complex (Bcc), including Burkholderia cenocepacia, are are a major cause of mortality and morbidity in cystic fibrosis patients. Infection can be asymptomatic but often results in chronic progressive worsening of lung function and sometimes acute fatal necrotizing pneumonia and sepsis, termed cepacia syndrome. The inherent resistance of the bacterium to multiple clinically useful antibiotics makes it is impossible to control the infection. The molecular mechanisms that allow B. cenocepacia to cause disease in these patients are still largely unknown. We are interested in the host phagocyte and early innate immune signaling pathways during virulent and persistent infections, the bacterial intracellular stages during infection, the transition between chronic and disseminated disease, and the role of bacterial virulence factors.
Zebrafish embryo infection model for Bcc
We have established the zebrafish (Danio rerio) as a vertebrate model to study Bcc virulence. The zebrafish has become a potent biomedical research model that has revolutionized our knowledge of the interaction of microbes with host phagocytes and the immune system through powerful live imaging and genetic tools.The transparent fish embryos allow easy real time analysis of infection with fluorescent bacteria, and in combination with transgenic reporter fish this allows for remarkable imaging of the behavior of host cells during infection. Most importantly, an innate immune system, with a high degree of similarity to that of mammals is already developing in the young embryo.
In zebrafish embryos, the epidemic strain B. cenocepacia isolate K56-2, induces an acute inflammatory infection that becomes rapidly fatal. Intravenously injected bacteria are mainly taken up by macrophages in which they are able to survive and efficiently replicate (Vergunst et al 2010 I&I), prior to dissemination and induction of systemic fatal infection. In contrast, other isolates, notably B. stabilis LMG14294 and B. vietnamiensis FC441, cause persistent infection, characterized by low but steady bacterial numbers in macrophages. Our results confirm earlier suggestions that an intracellular survival strategy contributes to virulence of B. cenocepacia in vivo. The model is particularly amenable to study in more detail the intracellular stages in vivo, and the effect of bacterial gene expression on host immune response.
We are using the zebrafish embryo as an animal model to study in vivo the capacity of intracellular Bcc to redirect maturation of the phagosome and create an intracellular replication niche, and to identify host factors involved in persistent and acute phases of the disease.
1. Analysis of host phagocyte response and analysis of early innate immune response signaling pathways to virulent and persistent B. cenocepacia infection.
2. Analysis of the intracellular stages during infection and identification of bacterial and host factors involved.
3. Analysis of the role of secretion systems and other virulence factors during infection.
Marie-Curie International training network (2012-2015) Link
Vaincre la Mucoviscidose (2016-2018), link
Fondation pour la recherche médicale (2010, 2016) link
Région de Languedoc-Roussillon (2010-2012, grant Chercheuse d’avenir, Annette Vergunst)