Macrophage inflammatory activation and behaviour in immunity to infection

Macrophages are innate immune cells that kill microbes and are important regulators of immune signaling in both health and disease. Many macrophage types have been identified and how different macrophages interact and function is crucial to many diseases. Macrophages are effector cells that directly kill pathogenic microbes and regulator cells that coordinate the response of the immune system to infection. In this project we want to understand how these two aspects of macrophage behaviour interact to decide the outcome of infection:
1) What is the relationship between individual macrophage behaviours and increased susceptibility to infection?
2) What is the molecular basis for differences in macrophage behaviour and can this be targeted for new therapy?The primary infection we will use in the project is the fungal pathogen Cryptococcus neoformans (goo.gl/bJaQco). Cryptococcal infection is both a significant opportunistic infection that causes hundreds of thousands of deaths worldwide each year and an excellent opportunity to understand the relationship between individual macrophage behaviour and infection due to the complicated interactions of Cryptococcus and macrophages (goo.gl/IkIf2V). Macrophages are essential for control of cryptococcal infection but we and others have identified how Cryptococcus is able to efficiently disrupt macrophage function: cryptococci can resist phagocytosis, grow within macrophages if they are taken up and can escape non-lytically by vomocytosis.
Critically, we have recently identified several key macrophage molecular immune modulators of behaviour (interferon-gamma, bacterial peptidoglycan and prostaglandin E2) that we can measure (with fluorescent reporters) and modify genetically. Therefore, in this project we will test two hypotheses:
1) The control and clearance of cryptococcal infection is dependent on extracellular pro-inflammatory cues that modify macrophage behaviour to intracellular cryptococci.
2) Changing macrophage behaviour to a controlling phenotype will reverse uncontrolled infection.
Zebrafish have a number of advantages in studying human infections having a highly similar immune system and being able to study both cell and sub-cellular biology in a living organism during infection. This project will use our in vivo zebrafish models of immunity and infection (goo.gl/Vhe8hF) to gain high content imaging data of the immune response and progression of infection with interferon-gamma, bacterial peptidoglycan and prostaglandin E2. These three factors will be modulated using transgenic and mutant zebrafish and pathogen strains (e.g. plb and lac mutants that have altered prostaglandin secretion, bacterial cell wall mutants and interferon gamma receptor mutants). We will measure, for example, the number of macrophages that respond to cryptococcal infection, the growth of cryptococci in the phagosome and the production of antimicrobial factors such as cathepsin D (as described previously: goo.gl/Vhe8hF). The project will be primarily wet lab-based but will use expertise from co-supervisors in engineering, mathematics and physics. We will use automated image analysis to specify and track immune cell and pathogen behaviour during infection. Image analysis data will be used for individual-based and multiscale modeling of cryptococcal infection and used to inform physical models of the macrophage pathogen macrophage interaction. We will then use our models to make experimental predictions and use these as a basis for exploring targeted therapy.