Viral Immunopathology Unit - Honours projects available in 2010

An Honours project undertaken in this lab would be administered by the Discipline of Pathology.

Background: Flaviviruses are single-stranded, RNA viruses transmitted by mosquitoes and ticks. This group of viruses is a major cause of illness and death throughout the world. Well known diseases include Yellow fever, dengue, Japanese encephalitis and Murray Valley encephalitis. Another flavivirus, West Nile virus (WNV), which causes encephalitis in humans and animals has recently spread for the first time throughout the continental USA, Mexico and Canada since a single epidemic outbreak in New York in August 1999. This disease causes 10-15 % death in clinical cases of encephalitis and survivors may end up with permanent nervous system damage.

Importantly, this disease is likely to be due to the over vigorous activity of the immune response. Indeed, infection of cells with WNV, causes a massive increase in the cell surface molecules that help to induce a successful immune response. These molecules include the class I major histocompatibility complex (MHC-I) and MHC-II molecules, intracellular adhesion molecule-1 (ICAM-1) (CD54), VCAM-1 (CD106) and E-selectin (CD62E), as well as the co-stimulatory molecule, B-7 (CD80), on Langerhans cells. These molecules are the major targets for cytotoxic T cell recognition. Thus, not surprisingly, these changes are associated with an increase in killing of infected cells by antiviral T cells during the immune response.

SO, why does a virus paradoxically encourage an immune response that will eradicate it?

Flavivirus-mediated increases in the immune response may constitute a novel virus survival strategy. However, it may also be the cause of the excessive immune system-mediated damage (immunopathology) in disease caused by these viruses. The mechanisms involved in these dramatic interactions are unknown and investigation of these issues is the main thrust of this laboratory..

We use a laboratory adapted strain of WNV, that has been used in Australia for about 40 years. Our laboratory has used this virus for 20 years. All students are trained in the use of sterile and safe techniques in virus handling. The following are brief outlines of a few possible projects in this laboratory for Honours (or PhD) in 2008. Should you wish to discuss these or others please contact Prof Nicholas King (nickk@pathology.usyd.edu.au) to make a time to talk about them in more detail.

1. Changes in gene expression in neurons and microglia in WNV encephalitis

Supervisor + contact details:

• Professor Nicholas King
• Professor Iain L. Campbell

We have shown that in WNV encephalitis, resting microglia (the macrophages of the brain) differentiate into a highly activated phenotype. They also increase MHC and adhesion molecule expression and proliferate and migrate to surround infected neurones. We think these cells clear the WNV from neurones, since in interferon-gamma gene knockout mice, which show much greater activation of microglia, animals survive 3-fold better. However, significant numbers of blood-derived inflammatory macrophages which migrate to the brain can also turn into microglia. We think these macrophage/microglia may contribute to the immunopathology in WNV encephalitis. The aim of this project is to examine the expression of various genes in neurones and microglia during infection, to determine the progress of events by looking at changes in various cell populations and determine how WNV is cleared from the brain

2. Infiltrating leukocytes in WNV encephalitis - their role in mortality

Supervisor + contact details:

• Professor Nicholas King
• Professor Iain L. Campbell

Part of the response to WNV infection of neurones is an infiltration of leukocytes into the brain on day 5 after infection. In interferon-gamma gene knockout mice, this infiltration is much reduced. This suggests that the increased survival in these mice may be because a particular subset of leukocytes does not migrate to the brain. This subset may also be involved in attracting inflammatory macrophages (see above). The aim of this project is to examine these subsets in the brain in both the wild type and gene knockout mice and look at their cytokine and chemokine expression. This will tell us why an increased leukocyte infiltration is associated with increased mortality in the wild type mouse.

3. The role of mucosal dendritic cells in controlling virus infection in epithelium

Supervisor + contact details:

• Professor Nicholas King

In a sexually transmitted disease (STD) model of virus infection in the mouse we find that infection by this route results in excellent immunity and very low mortality, compared to other routes on infection. Why is this so successful at this site? Understanding this is crucial for the development of effective vaccines.

We have found that the dendritic cells (DC) in the vaginal tissue accumulate where the virus infection is greatest in the epithelium and these DC disperse once the infection is eradicated. However, DC gather more quickly upon a second challenge with the same virus. What factors make them accumulate in this accelerated manner? Do these DC have antiviral activities? We are measuring how and when these cells immigrate into the vaginal epithelium and how they migrate from here to the local draining lymph nodes after infection to enable the antiviral immune response to be initiated. We are asking how this is different on the second challenge with the same virus. Using this model we are investigating if these steps involved in generating long-lasting antiviral immune memory responses at this site are the reasons for better survival.

4. Why isn't the foreign embryo rejected by the mother's role of adhesion molecules.

Supervisor + contact details:

• Professor Nicholas King

In the embryo MHC and ICAM-1 is downregulated shortly before implantation. This is thought to enhance the implantation of the embryo, since the effect of foreign proteins donated genetically by the father's sperm are not seen by the mother's immune system. The local area of the uterus is also immunosuppressed and specific changes occur in the mother which allow the foreign embryo to continue to develop, rather than be rejected. However, it does not make evolutionary sense that the mother is unable to distinguish viruses from the foreign paternal MHC expressed in the placenta. If this were so, it could lead to the death of the mother from infection. Using WNV infection as a tool, we are infecting the trophectoderm of embryos and re-implanting them into mothers to see if the immune system can distinguish virus infection from mere paternal "foreignness". Because of the technical demands of this project this is available for a PhD student only.

5. The role of monocyte/dendritic cells in initiating WNV immune responses.

Supervisor + contact details:

• Professor Nicholas King

We are also looking at the induction of the immune response via the skin where WNV gains its first access in vivo. As in the vagina (see above), large numbers of cells infiltrate into the focus of virus infection in the skin surrounding the area of infection. In our model, we have shown that immature monocytes come from the bone marrow via the blood and turn into dendritic cells (DC) locally. These immature cells are highly inflammatory and have attributes of inflammatory macrophages. Our question is, do these cells migrate to the draining lymph nodes and take part in the iinitiation of the immune response there, or are they a new type of DC that specifically wall off the infection to prevent its spread to the lymph node? There is significant scope for collaboration with the project below to see if microparticles enhance the initiation of the immune response by DC.

6. The role of microparticles in the immune response to WNV

Supervisor + contact details:

• Professor Nicholas King
• Professor Georges Emile Raymond Grau

Recent research shows that endothelial and other cells can produce small membrane vesicles or microparticles (MP) in response to inflammatory conditions. MP may worsen disease, but they may also be instrumental in enabling the efficient initiation and/or modulation of the immune response to infectious agents, for example, by interacting with dendritic cells. This project will investigate the production of MP by WNV-infected cells in vitro and in vivo. It will investigate when such particles are produced, what effect they have on other uninfected cells and if they can enhance the initiation of immune response in infected animals.