Immunopathogenesis Of West Nile Virus Encephalitis - Requirement For Interferon-gamma-dependent Soluble Mediators
Funder
National Health and Medical Research Council
Funding Amount
$250,500.00
Summary
Flaviviruses transmitted by arthropods cause considerable illness and death world-wide by their propensity to cause encephalitis. In August 1999, an outbreak of West Nile virus (WNV) encephalitis occurred in New York for the first time, indicating that these viruses are spreading beyond endemic areas. However, the mechanisms by which these viruses kill people are not at all clear. How the immune system deals with them is controlled by a complex network of interactions involving cells and soluble ....Flaviviruses transmitted by arthropods cause considerable illness and death world-wide by their propensity to cause encephalitis. In August 1999, an outbreak of West Nile virus (WNV) encephalitis occurred in New York for the first time, indicating that these viruses are spreading beyond endemic areas. However, the mechanisms by which these viruses kill people are not at all clear. How the immune system deals with them is controlled by a complex network of interactions involving cells and soluble mediators such as cytokines, chemokines, and nitric oxide, many induced or modulated by the cytokine, inteferon-gamma. Evidence suggests that these agents together influence both the types of cells that are mobilised to eradicate virus and also disease outcomes. Our hypothesis is that the host's own immune system is inadvertently responsible for encephalitis through an over-vigorous attempt to destroy the infecting virus, resulting in damage to the brain. To study WNV encephalitis, we are using a mouse model developed in this laboratory that reproduces the features of human disease. Another strain of these mice has the gene for interferon-gamma (IFN) inactivated or 'knocked out', so they cannot respond in the conventional way to virus infection. This mouse survives WNV infection significantly better than normal mice and becomes immune. Therefore we will compare cellular and soluble mediator responses of these mice during WNV infection to those of normal mice. We will also delete specific cell types making interferon-gamma in normal mice, as well as transfering such cells into knockout mice. Experiments will indicate which cell types are responsible and when particular components cause most damage. Thus, we will better understand how interferon-gamma recruits cells that mediate immune brain damage in this model. By understanding the events that lead to death in encephalitis, it may be possible to prevent or ameliorate them by means of immune intervention.Read moreRead less
Investigation Of Dendritic Cell Activation And Function In A Murine Model Of Plasmodium And Schistosoma Co-infection
Funder
National Health and Medical Research Council
Funding Amount
$358,938.00
Summary
Malaria is responsible for over 2 million deaths annually, mainly in sub-Saharan Africa. Importantly, around 1 billion people in malaria endemic areas are infected with parasitic worms, thus malaria and worm co-infections frequently occur. This project will investigate how malaria and worm parasites interact to influence the immune response and clinical outcomes of each other in a mouse infection model. This will provide new strategies for the design of effective treatments in co-endemic areas.
Critical Role Of TNF In Host-virus Interactions And Outcome Of Infection: Involvement Of Reverse Signalling Through MTNF
Funder
National Health and Medical Research Council
Funding Amount
$496,500.00
Summary
Cytokines are molecules produced by cells that take part in the immune response. They coordinate the activities of leukocytes and are important in the host response to virus infections. For their part, viruses have evolved strategies to try and evade the host response. The analysis of these strategies in the context of a viral infection will lead to a better understanding of the immune system and host-virus interactions. Tumour necrosis factor is a cytokine made by specific leukocytes, in two st ....Cytokines are molecules produced by cells that take part in the immune response. They coordinate the activities of leukocytes and are important in the host response to virus infections. For their part, viruses have evolved strategies to try and evade the host response. The analysis of these strategies in the context of a viral infection will lead to a better understanding of the immune system and host-virus interactions. Tumour necrosis factor is a cytokine made by specific leukocytes, in two stages: First, the cytokine is exposed on the surface of the cell and then it is clipped off and released as a soluble form. In either form it can interact with specific receptors on other cells and, in this way, change the cells' activities. We have found that binding of tumour necrosis factor receptors to the cytokine, while it is in its membrane form, can also send a message backwards into the cell bearing the tumour necrosis factor. This process, known as reverse signalling, then changes the activity of this cell and constitutes a major new route through which information transfer can occur. In this project we will characterize the biological changes that result from reverse signalling in specific types of leukocytes. We will be looking at the role of membrane tumour necrosis factor in two separate models of viral disease. The first is influenza pneumonia that is responsible for a great deal of morbidity and mortality worldwide. The second is a model of poxvirus infection (mousepox) that mimics the disease smallpox in humans. Human poxvirus infections are on the rise (e.g. monkeypox) and there is an increased threat of smallpox as a weapon of bioterrorism. Mousepox is a good model for the study of generalized viral infections and is also an excellent example of a virus that encodes proteins specifically designed to interfere with host tumour necrosis factor. Our studies will focus on the role of this cytokine in host-virus interactions and the outcome of infection.Read moreRead less
Understanding Interactions Between Eosinophils And Tissue-Invasive Parasitic Helminths
Funder
National Health and Medical Research Council
Funding Amount
$227,545.00
Summary
Eosinophils are blood cells which contribute to our defences against parasitic worms. Given the right opportunity, eosinophils can cause damage to some parasites within just a few hours of contact. This is quite a feat because parasitic worms are multicellular organisms which are much larger than eosinophils and which have evolved to live in the presence of active immune responses. To do it's job properly an eosinophil probably makes use of small soluble molecules in the blood and others fixed t ....Eosinophils are blood cells which contribute to our defences against parasitic worms. Given the right opportunity, eosinophils can cause damage to some parasites within just a few hours of contact. This is quite a feat because parasitic worms are multicellular organisms which are much larger than eosinophils and which have evolved to live in the presence of active immune responses. To do it's job properly an eosinophil probably makes use of small soluble molecules in the blood and others fixed to it's own cell surface, to recognize the parasite and to promote adhesion to the target. You might like to consider these molecules as hands grabbing onto handles on the surface of the parasite. The more hands there are, the better the grip and some hands grip more strongly than others. We are investigating what these molecules are and how they work. By understanding how eosinophils operate, we may be able to devise ways in which we can make them more effective. We are also trying to understand why some species of parasite are resistant to attack by eosinophils. We think that resistant parasites secrete substances which either block the binding of eosinophils to the parasite surface, or prevent the functioning of eosinophils that do bind. It is possible that these inhibitory substances may even kill the eosinophils before they can do their job. Resistant parasites might induce eosinophils to commit suicide, a useful property for us when we no longer need these cells, but a definite drawback if they still have a job to do. Parasitic worms have evolved to avoid at least some of our defences and sometimes they do this by mimicing natural processes important for regulating immune responses. In some diseases like asthma and allergy eosinophils slip from normal controls which regulate them and then they can cause tissue damage. Inhibitors of eosinophils which are produced by parasites might form the basis of new drugs to control these cells in diseases like asthma.Read moreRead less