IgA Mediated Activation Of FcalphaRI, An Fc Receptor And A Leukocyte Ig-like Receptor.
Funder
National Health and Medical Research Council
Funding Amount
$535,500.00
Summary
Our immune system exists to seek and destroy infections caused by bacteria and viruses (pathogens) that would grow in us. B cells in the immune system make antibody tags which attach to pathogens marking them for elimination. A special type of antibody is IgA. IgA occurs in two forms, the first is found at mucosal sites, these are membranous passages in the body, such as the lung, the gut and the genital tract. These communicate with the outside and are the major route of pathogen entry into the ....Our immune system exists to seek and destroy infections caused by bacteria and viruses (pathogens) that would grow in us. B cells in the immune system make antibody tags which attach to pathogens marking them for elimination. A special type of antibody is IgA. IgA occurs in two forms, the first is found at mucosal sites, these are membranous passages in the body, such as the lung, the gut and the genital tract. These communicate with the outside and are the major route of pathogen entry into the body. Here IgA forms a rather passive, but pathogen specific, sticky barrier to prevent microbial pathogens attaching to these large surfaces. In an everyday analogy this IgA behaves somewhat like fly-paper. This subdued response is appropriate as we are constantly exposed to micro-organisms living in our gut, or breathed into our lungs, and our immune system would make us ill if it aggressively attacked our innocuous microbial neighbours. The second type of IgA is found in the blood where it attaches to pathogens that have breached the body's barriers. These IgA tags are actively sought by white blood cells whose function is to protect the body from infection by recognising and engulfing the tagged pathogens and destroying them with killer molecules, including bleach. The IgA-Fc receptor is the sensor on the surface of white blood cells which seeks the IgA tags as they attach to pathogens. In order to survive in this hostile environment some of our pathogens, such as Staphylococcus, have their own strategies to make themselves invisible to the immune system. These strategies include cutting up the IgA tags or blocking the sensors for IgA. In this project we will study how IgA tags turn on white blood cells to destroy pathogens. We will also be looking at two Staphylococcal proteins which block up the sensor for IgA tags. Finally we are endeavouring to understand how it is the mucosal type IgA does not activate the white cells nearly as much as the IgA from the blood.Read moreRead less
Defining The Molecular Effectors And Regulators Of Anti-viral Immune Responses
Funder
National Health and Medical Research Council
Funding Amount
$447,750.00
Summary
In humans, cytomegalovirus infection can cause severe disease and may even be fatal in individuals with immature or compromised immune systems, such as newborns, AIDS patients, transplant recipients and people treated with chemotherapeutic drugs. The majority of healthy individuals however can clear the infection with minimal disease. The ability of cytomegalovirus to cause disease is increased in the absence of effective immune responses which would normally clear the virus before illness occur ....In humans, cytomegalovirus infection can cause severe disease and may even be fatal in individuals with immature or compromised immune systems, such as newborns, AIDS patients, transplant recipients and people treated with chemotherapeutic drugs. The majority of healthy individuals however can clear the infection with minimal disease. The ability of cytomegalovirus to cause disease is increased in the absence of effective immune responses which would normally clear the virus before illness occurs. Understanding the role of specific mediators of anti-viral immune responses is therefore of paramount importance in establishing the guidelines for the design of more effective anti-viral therapies. The mouse model of cytomegalovirus infection provides a unique system to dissect the roles of specific components of the immune response during the course of viral infection. Our previous studies have shown that anti-viral immune responses are complex and involve a multitude of players. The central aim of the work in the current proposal is to establish the precise contribution of specific molecular effectors and regulators of anti-viral immune responses and define their relevance during the different stages of viral infection. Hence, the results of these studies will be relevant to understanding the pathogenesis of cytomegalovirus infection in humans and more importantly will provide critical insights into the rational design of improved antiviral drugs and vaccines. Since the molecules and cells under investigation are also known to play a crucial role in immune responses that control tumour growth and transplant survival, the proposed studies will provide valuable insight towards the development of new therapies for pathologies associated not only with cytomegalovirus infection, but also with the conditions named above.Read moreRead less
Biology Of The Novel C-type Lectin Receptor DCL-1 In Innate And Adaptive Immune Response
Funder
National Health and Medical Research Council
Funding Amount
$439,500.00
Summary
The innate immune system is the first line of defense in protecting the body from infection. Phagocytic (meaning eating) white blood cells, which include dendritic cells and macrophages are equipped with cell surface proteins These bind the many types of microbes that cause infection, allowing the phagocytes to destroy them (innate immune response). Furthermore, dendritic cells and macrophages have mechanisms to activate additional specific responses (adaptive immune response) mediated by lympho ....The innate immune system is the first line of defense in protecting the body from infection. Phagocytic (meaning eating) white blood cells, which include dendritic cells and macrophages are equipped with cell surface proteins These bind the many types of microbes that cause infection, allowing the phagocytes to destroy them (innate immune response). Furthermore, dendritic cells and macrophages have mechanisms to activate additional specific responses (adaptive immune response) mediated by lymphocytes (T and B cells). We have discovered a cell surface protein, termed DCL-1, which may play a role in uptake of microbes by phagocytes and activation of innate and adaptive immune responses. This project will examine the mechanisms whereby DCL-1 mediates these immune responses. Understanding the mechanism may allow us to exploit DCL-1 for tumor immunotherapy.Read moreRead less
Immunodominance In Vaccinia Virus And Recombinant Vaccinia Vaccines
Funder
National Health and Medical Research Council
Funding Amount
$388,455.00
Summary
When confronted with an invading microbe, the human immune system does not recognise its overall shape. Instead, the microbe is chopped up into tiny fragments, called peptides, and these can be recognised by special cells of the immune system called T cells which orchestrate a response. We have a good understanding of this chopping process and can predict many of these peptides, but this is only part of the story. Not all peptides will be recognized by a T cell. Further, through processes we do ....When confronted with an invading microbe, the human immune system does not recognise its overall shape. Instead, the microbe is chopped up into tiny fragments, called peptides, and these can be recognised by special cells of the immune system called T cells which orchestrate a response. We have a good understanding of this chopping process and can predict many of these peptides, but this is only part of the story. Not all peptides will be recognized by a T cell. Further, through processes we do not understand well, T cells that recognize only a few out of the many peptides will dominate an entire immune response. As a result, immune responses are focused in such a way that they recognize only a tiny portion of an invading microbe. Focusing of immune responses also occurs during immunization with vaccines. Some new, genetically engineered vaccines use a harmless microbe to carry small parts of more dangerous pathogens. The parts chosen will not cause any disease by themselves, so the whole vaccine is safe. Vaccines built in this way are in clinical trials for diseases such as AIDS and malaria, but do not work as well as was hoped. These new vaccines are largely made up of the carrier and the parts of the microbe we wish to immunize against (e.g. a part of the AIDS virus) will be only a small fraction of the whole vaccine. Ideally we would like the immune system to focus on this small part of our choosing, but the few studies done suggest that this is not the case. In this project we will study vaccines that use a carrier called vaccinia virus. We will test to what extent immune responses are focused inappropriately. We will then genetically alter the virus and use new immunisation strategies to try and shift the focus of the immune response so that it targets the right parts of the vaccine. The ultimate aim is to improve vaccines, but in the process we may learn more about how the immune system chooses its targets.Read moreRead less
HIV currently infects ~40 million people world-wide, causing ~3 million deaths in 2003, mainly in the world's poorest countries. A cheap, effective vaccine seems the best means of preventing the spread of the epidemic. The two main approaches to vaccination are either to make antibodies (which bind to and inactivate the virus), or killer T cells (which kill infected cells). Many of these vaccines are now being tested in monkeys. The results of killer T cell vaccination trials have been both enco ....HIV currently infects ~40 million people world-wide, causing ~3 million deaths in 2003, mainly in the world's poorest countries. A cheap, effective vaccine seems the best means of preventing the spread of the epidemic. The two main approaches to vaccination are either to make antibodies (which bind to and inactivate the virus), or killer T cells (which kill infected cells). Many of these vaccines are now being tested in monkeys. The results of killer T cell vaccination trials have been both encouraging and disappointing. The vaccines do not appear able to prevent the monkeys from getting infected with the virus. However, in many cases even though the monkeys become infected with HIV, they do not get the usual disease associated with AIDS, and hence live with rather than die from this infection. The aims of this project are to use statistical analysis, and more complex mathematical and computer models to try to analyse the data generated by these vaccine trials and to understand how these partially effective vaccines help control virus. For example, even if a vaccine does not prevent infection, we can investigate whether it slowed viral growth, or increased killing of infected cells, and if so, whether an increase in this response could be effective. In preliminary work we have analysed data from a vaccination trial performed in Boston. The results of this study suggest that the reason vaccinated monkeys still become infected is that the killer T cells produced by the vaccine do not appear to activate for the first 10 days of infection. In these first 10 days the virus grows normally and is able to establish a foothold for continuing infection. By contrast, we find that antibodies act extremely early after infection. The methods we propose have not been used before to study vaccines, and by studying the kinetics of the virus and immune response from a large number of vaccine trials we hope to help identify the optimal vaccine design.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
Molecular Interactions Of The Tetraspanins CD37, TSSC6 And CD151 In T Cells
Funder
National Health and Medical Research Council
Funding Amount
$566,575.00
Summary
The tetraspanins are a new type of protein that are found at the surface of cells. Cells of the immune system, such as white blood cells, display at their surface, up to 20 different tetraspanin proteins. However, the precise contributions of these tetraspanin proteins to immunity is still not clear, nor is it clear exactly how tetraspanin proteins differ from one another and why white blood cells need to display so many different tetraspanins. Using genetic technology we have created mice which ....The tetraspanins are a new type of protein that are found at the surface of cells. Cells of the immune system, such as white blood cells, display at their surface, up to 20 different tetraspanin proteins. However, the precise contributions of these tetraspanin proteins to immunity is still not clear, nor is it clear exactly how tetraspanin proteins differ from one another and why white blood cells need to display so many different tetraspanins. Using genetic technology we have created mice which are unable to express certain individual tetraspanin proteins at their cell surface. Excitingly, the immune systems of these mice are not normal, in particular one type of white blood cell, the T cell responds in an exaggerated manner to stimulation. These results suggest a role for tetraspanins in the control and regulation of the immune system. This project will extend these results and work out the precise molecular mechanism by which the tetraspanins exert this control. In the future, a full understanding of how tetraspanins control T cells may ultimately lead to novel ways of controlling the immune system.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
Role Of The Natural Killer Complex In The Control Of Murine Malarial Pathogenesis
Funder
National Health and Medical Research Council
Funding Amount
$487,500.00
Summary
Natural Killer (NK )cells are an essential arm of the innate immune system. NK cell function is controlled by a series of cell surface receptors encoded within a defined genetic region named the Natural Killer Complex (NKC). This region appears to be highly polymorphic both in mice and humans. It is known that different mouse strains, which differ in the expression of NKC molecules have distinct ability to mount inflammatory responses during infection. In fact, we have previously shown that the ....Natural Killer (NK )cells are an essential arm of the innate immune system. NK cell function is controlled by a series of cell surface receptors encoded within a defined genetic region named the Natural Killer Complex (NKC). This region appears to be highly polymorphic both in mice and humans. It is known that different mouse strains, which differ in the expression of NKC molecules have distinct ability to mount inflammatory responses during infection. In fact, we have previously shown that the differential expression of NKC molecules in mice accounts for the degree of susceptibility to Plasmodium berghei-mediated cerebral malaria, a syndrome that accurately reproduces malarial disease induced by Plasmodium falciparum in humans and that results from an exacerbated pro-inflammatory response to infection. Since the NKC comprises several genes and multi-gene families, the main objective of this proposal is to identify which molecule-s within this genetic region are responsible for the induction of cerebral malaria pathogenesis. Our preliminary results indicate that an activation receptor named Ly49D, which is only expressed on the surface of NK cells from cerebral malaria-susceptible mice, plays a key role in disease-induction. Activation of Ly49D induces NK cells to secrete large amounts of IFN-gamma, a pro-inflammatory cytokine known to mediate cerebral-malaria pathogenesis. We will characterize the immunological function of Ly49D+ NK cells during P. berghei infection and determine whether these cells are the main source of IFN-gamma production. We will also identify the ligand (from parasite or host origin) responsible for the stimulation of this NKC activation receptor during malaria infection. The identification and characterization of these NKC receptors will provide new insights to explain the immunological basis of malarial pathogenesis and could lead to the development of therapeutical approaches designed to prevent severe malarial disease.Read moreRead less