Human cytomegalovirus (HCMV) is a classic example of a group of herpes viruses, which is found universally throughout all geographic locations and socioeconomic groups, and infects 50% of adults in developed countries. HCMV infection is important to certain high-risk groups. Major areas of concern are: (1) the risk of infection to unborn baby during pregnancy, (2) the risk of infection to people who work with children, and (3) the risk of infection to immunocompromised persons (e.g. organ transp ....Human cytomegalovirus (HCMV) is a classic example of a group of herpes viruses, which is found universally throughout all geographic locations and socioeconomic groups, and infects 50% of adults in developed countries. HCMV infection is important to certain high-risk groups. Major areas of concern are: (1) the risk of infection to unborn baby during pregnancy, (2) the risk of infection to people who work with children, and (3) the risk of infection to immunocompromised persons (e.g. organ transplant patients and HIV-infected individuals). Epidemiological studies have shown that 80%-90% of developing unborn babies who acquire congenital HCMV infection displays a variable pattern of pathological sequelae within the first few years of life that may include hearing loss, vision impairment and mental retardation. There is an increasing argument that a reduction in HCMV load will have a significant effect on the sequelae associated with congenital HCMV infection. Indeed, vaccination provides the most practical modality of achieving such a reduction in HCMV load. To develop such a vaccine, formulation based on viral antigens that activate both protective cellular and humoral responses needs to be tested to assess its immunogenicity. No such vaccine is presently available for HCMV. In this application we have sought to develop a prophylactic vaccine and to test its efficacy in a immunocompetent transgenic mouse model and as well under conditions of immunosuppression (CD4 T cell deficient). The overall strategy is to use this prophylactic vaccine to stimulate the cellular (CD8+ and CD4+ T cells) and humoral responses against multiple HCMV antigens. This vaccine will be based on the novel chimeric polyepitope technology and exploits a novel replication deficient adenovirus expression system which has recently been approved for human use.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
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
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
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