ERC FUNDED PROJECTS

A common strategy of bacterial pathogens is active or passive uptake into host cells. There, they can localize within a bacterial containing vacuole (BCV) or access the host cytoplasm through BCV rupture. Hence, intracellular pathogens are often classified as vacuole-bound or cytoplasmic. Recently, this definition has been challenged by the discovery that many vacuole-bound pathogens, including Mycobacterium tuberculosis and Salmonella enterica, access the host cytoplasm, and by the insight that cytoplasmic bacteria, like Shigella flexneri or Listeria monocytogenes, do not always escape the BCV. Despite this increasing complexity, a precise understanding lacks for why and how a pathogen “chooses” between a BCV or the cytoplasm and yet this is very important: because of differential pathogen sensing in membrane-bound and cytoplasmic compartments, intracellular localization leads to induction of different host responses. Therefore, a comprehensive understanding of the processes controlling BCV integrity is not only essential, but can provide new therapeutic targets. Our previous research has implemented innovative fluorescence microscopy to track the invasion steps of pathogenic bacteria. We have further integrated a large-volume, correlative, light/electron microscopy (CLEM) workflow via focused ion beam scanning electron microscopy. This uncovered the subversion of host Rab cascades by Shigella to rupture its BCV. Starting with the Shigella model of epithelial cell invasion, we will delineate the precise molecular mechanisms controlling BCV integrity in different host cell types. We will analyze (i) the scaffolds of host pathways for membrane remodeling, (ii) their subversion by various pathogens, and (iii) their differential regulation depending on pathophysiological conditions. Together, this will allow development of novel, rational antimicrobial strategies and will yield fundamental insight into understudied cell biological mechanisms of membrane trafficking.

2 000 000 €

Start date: 2017-01-01, End date: 2021-12-31

Studying host-pathogen interactions by focusing on the interaction of a single pathogen with the host has defined our understanding of these events and the insights gained form the basis for the therapeutic and vaccination strategies we use today. However, people become infected with multiple pathogens throughout their lifetime, at times even simultaneously. Still, it is largely unknown how the immune response to one pathogen alters the body’s ability to respond to a second infectious agent or the susceptibility to autoimmunity or cancer. This project will address this question by focusing on infection-induced changes in regulatory T cells (Tregs) as they may lead to biased suppression and changes in the nature of subsequent immune responses. Our efforts will focus on two areas: In a first part, we will use single cell RNA-Seq to address how infections shape the Treg compartment by defining the specialized Treg subsets generated during polarized infectious settings and analyzing how they interact with effector T cells. Based on the depth of information we expect to obtain from this approach, we envisage finding thus far unappreciated interactions and functions of Tregs in the course of an immune response. The second part will investigate how an altered Treg compartment, either through genetic modifications or infection-induced, affects disease susceptibility. In this context, we will also address stability and persistence of pathogen-induced changes in the Treg compartment. Collectively the proposed experiments will allow us to start addressing how preceding infections affect disease susceptibility. Deciphering how infection history shapes the Treg compartment and how this affects susceptibility to future challenges will lay the groundwork for addressing this question more broadly in the future and as such will likely have a transformative impact on the field.

1 499 755 €

Start date: 2016-06-01, End date: 2021-05-31

TILC focuses on Innate Lymphoid Cells (ILCs). ILCs are a newly discovered type of lymphocyte, and their study opens up new perspectives for understanding and manipulating of immunity. ILCs include cytotoxic ILCs (NK cells) and helper-like ILCs (ILC1, ILC2 & ILC3). Studies of ILC2 cells have advanced considerably, but much remains unknown about the respective roles of NK, ILC1 and ILC3 cells. TILC aims to explore new frontiers in ILC biology, by focusing on these subsets of ILCs in mice and humans, through five specific aims. 1. NK cells, ILC1 & NCR+ILC3 are known to express NKp46 in humans and mice, but the nature of the NKp46 ligands remains unclear, limiting our understanding of the biology of these three major ILC subsets. We thus aim to identify the NKp46 ligands, building on our preliminary data showing that Complement Factor P (CFP, Properdin) is involved in NKp46 recognition, hence revealing an unprecedented mode of immune recognition. 2. We also aim to create new mouse models selectively targeting these ILC subsets in vivo. We will then use these models for dissecting out the selective roles of ILC subsets in two major immune functions: cancer surveillance and gut homeostasis. 3. In cancer, we will investigate the contribution of these cells to tumor editing. 4. In the intestine, we will focus on the homeostasis of the cecum and appendix. These organs were long considered to be vestiges of evolution, but our own recent findings and those of phylogenetic studies have challenged this notion. We thus aim to address the role of ILC subsets in the cecum/appendix, and determine whether these organs serve as a refuge for repopulation with commensals after dysbiosis. 5. Finally, we aim to identify patients with deficiencies in ILCs, to dissect the function of these cells in natura. From the molecular scale to that of patients, we believe that TILC will provide answers to some of the most pressing questions concerning the role and clinical potential of NKp46+ ILCs

2 500 000 €

Start date: 2017-01-01, End date: 2021-12-31