Pierre Cosson


Host-pathogen relationships: recognition, phagocytosis and killing of bacteria.


Phagocytosis is the process by which eukaryotic cells ingest big particles (>1µm), for example bacteria. Phagocytic cells such as macrophages are an essential element in the defense of the human body against infectious microorganisms. To understand at the molecular level how perform and control phagocytosis, we are making use of a model phagocytic cell, the amoeba Dictyostelium discoideum. Amoebae phagocytose bacteria to feed upon them, and the molecular mechanisms involved are very similar to those observed in mammalian phagocytic cells.


Using this simple system, we are studying the role of various gene products in phagocytic cells. Our aim is to understand how a cell can sense different types of bacteria, how it ingests them, and how it kills them. Some facets of this process (ingestion phase) have been relatively well studied, others (intracellular killing) are still poorly understood. Our results indicate that different-and largely uncharacterized- mechanisms ensure killing of different types of bacteria. We are also using cultured cells to validate our findings in mammalian cells.


Many species of pathogenic bacteria have developed strategies to survive their encounter with phagocytic cells, enabling them to infect human patients. We are also studying these bacterial survival strategies, notably those used by Pseudomonas aeruginosa, Klebsiella pneumoniae and Mycobacterium marinum.


These various themes (phagocytosis, recognition and killing of bacteria, host-pathogen relationships) are linked both conceptually and at the experimental level.


Pierre Cosson holds the Doerenkamp-Naef-Zbinden chair at the Faculty of Medicine, dedicated to the development of alternatives to animal experimentation. His group is pioneering the use of recombinant antibodies as a high-quality alternative to antibodies produced in animals. They have created the ABCD database describing existing recombinant antibodies, the Geneva Antibody Facility for production and discovery of recombinant antibodies and Antibody Reports, an open access journal dedicated to the description and characterisation of recombinant antibodies.