The immune system employs a variety of strategies to combat parasites including viruses. One of them is cytolytic lymphocytes, cells that can recognize and destroy virus-infected target cells. These cells use, besides other molecules, enzymes called granzymes to kill target cells by inducing suicide in them. We intend to investigate if those granzymes can protect cytolytic lymphocytes themselves from being infected by viruses and turned into viral factories. We are going to use a model of a natu ....The immune system employs a variety of strategies to combat parasites including viruses. One of them is cytolytic lymphocytes, cells that can recognize and destroy virus-infected target cells. These cells use, besides other molecules, enzymes called granzymes to kill target cells by inducing suicide in them. We intend to investigate if those granzymes can protect cytolytic lymphocytes themselves from being infected by viruses and turned into viral factories. We are going to use a model of a natural infection, ectromelia, mouse pox. Mouse pox is fatal in resistant strains of mice if the genes for the two dominant granzymes are deleted. This indicates that granzymes are essential for fighting this viral disease. We will explore in which cells of the immune system granzymes are expressed and whether virus entry into a cell can actually trigger their expression. Furthermore, we will investigate how the granzymes inhibit virus infection within the infected cell to determine whether the mechanisms involved resemble those used by cytolytic lymphocytes in killing of target cells (i.e. degradation of DNA and mitochondrial damage), or whether they represent entirely new facets of granzyme function. Finally, using viruses from a number of different families, we will establish whether these functions of granzymes also contribute to protection from other viral infections. An understanding of the role of these granzymes in the innate immune response, i.e. before antigen specific T cell and antibody responses are fully activated, is of great significance as it may allow us to manipulate this particular anti-viral response and thus enhance survival and reduce morbidity in viral infections.Read moreRead less
The Early Inflammatory Response To Virulent And Avirulent Influenza Viruses
Funder
National Health and Medical Research Council
Funding Amount
$252,761.00
Summary
Innate immune mechanisms are vital components of host defences against pathogens. In this proposal I aim to investigate the particular mechanisms that operate in early defence against influenza virus infection and compare the ability of virulent and avirulent virus strains to (i) be recognized by components of the innate immune system, and (ii) to trigger an early inflammatory response to infection. It is anticipated that virulent virus strains have adapted to avoid recognition by innate cells s ....Innate immune mechanisms are vital components of host defences against pathogens. In this proposal I aim to investigate the particular mechanisms that operate in early defence against influenza virus infection and compare the ability of virulent and avirulent virus strains to (i) be recognized by components of the innate immune system, and (ii) to trigger an early inflammatory response to infection. It is anticipated that virulent virus strains have adapted to avoid recognition by innate cells such as macrophages. By avoiding this route of uptake and destruction, the virus is free to infect and replicate in other cells of the respiratory tract. Furthermore, by evading macrophage entry, the virus avoids triggering the release of early inflammatory mediators from these cells and this may affect both the speed and the magnitude of the subsequent inflammatory response. This study will contribute to a greater understanding of factors involved in initiating and regulating inflammation in the respiratory tract following viral infection. Furthermore, the findings may provide new insights into mechanisms of virulence of influenza and other enveloped viruses.Read moreRead less
The world has suddenly been alerted to the threat of pandemic influenza with the recent deaths in Asia of patients and their close contacts from which the avian influenza H5N1 virus has been isolated. Experts believe that it is only a matter of time before this virus mutates and acquires the ability to rapidly spread within the human population. The currently available vaccines have virtually no capacity to prevent infection by a new pandemic virus. Once the virus strikes appropriate vaccines ca ....The world has suddenly been alerted to the threat of pandemic influenza with the recent deaths in Asia of patients and their close contacts from which the avian influenza H5N1 virus has been isolated. Experts believe that it is only a matter of time before this virus mutates and acquires the ability to rapidly spread within the human population. The currently available vaccines have virtually no capacity to prevent infection by a new pandemic virus. Once the virus strikes appropriate vaccines can be made against it but this procedure takes at least 6 months, the time predicted for the virus to have already spread throughout the globe. We are proposing that a vaccine designed to induce killer T cells (called CTLs) that target the conserved regions shared by all influenza viruses, could be used as a preventative measure without prior knowledge of the exact type of virus that will emerge. This sort of vaccine will not prevent against infection but will greatly lessen the severity of the disease. We have already designed a vaccine that that will induce high levels of CTLs that can greatly speed up the clearance of viruses of the type that are currently in the human population, when tested in animal models. However, we predict that a new pandemic virus will be much more vigorous in its growth and so our vaccines will have to be improved to cope with this. This project looks at ways of increasing the number and effectiveness of the CTLs that are induced by our vaccines. This will require an understanding of how we can modulate the function of other specialised cells, dendritic cells and helper T cells, that play a role in starting and maintaining the CTL response, as well as modulating the CTLs themselves.Read moreRead less
Role Of Plasmacytoid Dendritic Cells And Neutrophils In The Generation Of Antiviral Immunity
Funder
National Health and Medical Research Council
Funding Amount
$469,500.00
Summary
Work described in this application is important in understanding how two very different types of white blood cells, namely neutrophils and plasmacytoid dendritic cells (PDC), contribute to the generation of an effective immune response and control of virus growth. Both these cell types are activated in the earliest phase of the host response and are likely to play crucial roles in determining the nature of the later components of the response. We have recently shown that animals depleted of Gr-1 ....Work described in this application is important in understanding how two very different types of white blood cells, namely neutrophils and plasmacytoid dendritic cells (PDC), contribute to the generation of an effective immune response and control of virus growth. Both these cell types are activated in the earliest phase of the host response and are likely to play crucial roles in determining the nature of the later components of the response. We have recently shown that animals depleted of Gr-1+ cells, with monoclonal antibody (mAb) RB6-8C5, rapidly succumb to a poxvirus infection (mousepox) with 100% mortality. In contrast, mice treated with a control mAb clear the infection very effectively. Host responses essential for recovery from mousepox, including antiviral cytotoxic T lymphocyte (CTL) response and gamma interferon production, are severely diminished in mice treated with the Gr-1+ cell depleting mAb. Since the mAb can potentially deplete both neutrophils and PDC, this raises the important question of whether one or both of these cell types may be involved in the generation of cytokine and cell-mediated immune responses to viral infection. Although PDC and neutrophils themselves are not thought to present antigen to T cells, the elucidation of how they may control the generation of this major arm of the immune response will be novel and has important implications for vaccine design. Virtually nothing is known about how neutrophils or PDC influence viral antigen presentation by antigen presenting cells. Several murine models of viral infection, that in many ways mimic the diseases in humans, will be used to map the sequence of events initiated by PDC and neutrophils and which end in the clearance of virus from the host. Understanding these pathways and identifying the essential mediators and their interactions is critical in elucidating the role of the two cell types in the host response to virus infection.Read moreRead less
Viral Immune Evasion From The NK Cell Ly49H Activation Receptor
Funder
National Health and Medical Research Council
Funding Amount
$239,250.00
Summary
Infection with human cytomegalovirus (HCMV) remains a significant health problem for individuals whose immune systems are immunocompromised (transplant patients and AIDS patients) or poorly developed (such as the foetus and newborn children). While drugs are available to treat HCMV infection the emergence of viral drug escape mutants means there is a medical necessity to develop new therapies and vaccines against this agent. As a basis for this it is important to develop a better understand the ....Infection with human cytomegalovirus (HCMV) remains a significant health problem for individuals whose immune systems are immunocompromised (transplant patients and AIDS patients) or poorly developed (such as the foetus and newborn children). While drugs are available to treat HCMV infection the emergence of viral drug escape mutants means there is a medical necessity to develop new therapies and vaccines against this agent. As a basis for this it is important to develop a better understand the host-virus relationship to rationally design appropriate treatments. As HCMV is species specific and does not infect experimental animals, the murine cytomegalovirus (MCMV) in mice is widely used as a model for HCMV disease. MCMV infection is controlled by both innate and adaptive arms of the host's immune response. Natural killer (NK) cells constitute an important frontline defence against MCMV and understanding how they are activated is of importance to harnessing them for anti-viral control measures. Recently we have shown that NK cells are activated via the interaction of an NK cell activation receptor (Ly49H) with a MCMV-encoded ligand (m157). However, we have also found that MCMV can rapidly mutate its m157 gene to evade effective NK cell control and that wild populations of MCMV have foms of m157 that don't bind to Ly49H. Other studies suggest that m157 can bind to inhibitory NK cell receptors, such as Ly49I, and inactivate the NK cell response. This study seeks to understand the dynamics of the m157-Ly49H and m157-Ly49I interactions. As HCMV infection is also regulated at early stages by NK cells, an understanding of how CMV can rapidly mutate its m157 gene to avoid interaction with Ly49H-expressing NK cells has important implications for understanding human disease caused by HCMV, in terms of potential viral escape from NK cell surveillance.Read moreRead less