Viral Immunopathology Unit - Honours projects available in 2009

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. In addition, significant numbers of blood-derived inflammatory macrophages migrate to the brain. We think this may be the way in which WNV is cleared from neurones, since in interferon-gamma gene knockout mice, which exhibit greater activation of microglia, animals survive 3-fold better. However, our work indicates that these macrophages may also contribute to the immunopathology occurring 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 does this happen? We are therefore examining what factors are associated with innate resistance to infection and what conditions best facilitate the generation of specific and effective anti-viral responses. This is important for the development of vaccines against STD's.

Using this model we are analysing the steps involved in generating long-lasting antiviral immune memory responses. For example, 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. This suggests the presence of factors that allow them to accumulate in this accelerated manner. We are measuring when and how these cells migrate from the vaginal epithelium to the local draining lymph nodes after infection to enable the antiviral immune response to be initiated and how different this is on the second challenge with the same virus. We are also looking at the migration of naive and immune lymphocytes along these pathways.

From these results we may be able to better understand how these immune response are initiated and understand better the differences in antiviral immune responses after primary and secondary infection. This will also allow us and determine when, where and how STD vaccines should be administered to obtain the most effective immunity.

4. Maintenance of epithelial barriers in cell defence against virus infection

Supervisor + contact details:

• Professor Nicholas King
• Dr Michele Madigan

In the eye, a major cellular seal against the 'outside world' is the retinal pigment epithelium, which protects the cells inside the eye from infectious organisms, such as viruses, and even immune cells that may invade it. Infection of these cells with WNV in culture results in changes in the cells that may prevent the transmission of virus into the eye itself. We are investigating the factors involved in controlling these changes. They have an important bearing on the way a crucial organ like the eye avoids being destroyed by virus infection or the resulting over-vigorous immune response.

5. The role of Langerhans and 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. We have already shown that Langerhans cells in the epidermis migrate to the local draining lymph nodes faster in response to WNV infection than in response to infection by other skin-acquired viruses. However, in addition, dendritic cells also migrate from the dermis to the lymph nodes and also seem take part in the accelerated initiation of immune response to viruses. We know that UV irradiation of the skin produces systemic immunosuppression. Most of these viruses are prevalent in countries with a lot of sunshine. So, what happens when a virus that stimulates a strong immune response infects an animal that is immunosuppressed by UV irradiation? The aim of this project is therefore to examine the changes that occur in association with migration of Langerhans cells to the local draining lymph node at various sites of infection and in different strains of mouse after UV irradiation.

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

Supervisor + contact details:

• Professor Nicholas King
• Professor Georges 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.