Identification Of Antigen Selection In The Human IgE Response By Analysis Of Somatic Point Mutations
Funder
National Health and Medical Research Council
Funding Amount
$256,973.00
Summary
Allergic disease affects over 25% of the Australian community. It is responsible for significant sickness and death, particularly amongst children, and its incidence is on the increase. The reasons for this, and the underlying causes of allergic disease, remain unclear. Allergic disease results from the actions of molecules called IgE antibodies, which are also associated with parasitic infection. Even in these conditions, where IgE concentrations are raised in the blood, the concentrations are ....Allergic disease affects over 25% of the Australian community. It is responsible for significant sickness and death, particularly amongst children, and its incidence is on the increase. The reasons for this, and the underlying causes of allergic disease, remain unclear. Allergic disease results from the actions of molecules called IgE antibodies, which are also associated with parasitic infection. Even in these conditions, where IgE concentrations are raised in the blood, the concentrations are too low to allow their direct study. We have recently applied molecular biological techniques to study the genes that encode IgE antibodies. Our work suggests that the IgE response can sometimes develop in a different way to that of other antibodies (eg IgG). On the other hand, laboratory (in vitro) studies over many years support the possibility that IgE and IgG develop in parallel. In this study, we wish to identify circumstances in which IgG-like IgE antibodies develop. We therefore wish to study patients with different kinds of allergic disease, and patients with other conditions that are associated with IgE production. We therefore wish to study patients who have infections with parasitic worms. We deduce the processes that give rise to IgE antibodies by analysing patterns of mutations that accumulate in antibody genes during an immune response. Over recent years, we have developed new approaches to the analysis of such mutations, and this project also seeks to further develop our mutation analysis. This more powerful analysis will be applied to the study of mutations in the IgE genes seen in different patient groups, and should allow us to quantify the proportion of IgE antibodies that develop in each way. A better understanding of the relative contributions of the two pathways to IgE, in different conditions, will transform our understanding of the IgE response, and open up new avenues for the investigation of the causes and treatment of allergic disease.Read moreRead less
Analysis And Regulation Of Leptospiral Virulence Factors.
Funder
National Health and Medical Research Council
Funding Amount
$630,465.00
Summary
Leptospirosis is a globally important infectious disease caused by Leptospira spp. This project aims to identify and characterise factors which play a role in disease development by knocking out genes, then investigating the impact on overall gene-protein expression in the mutant strain and its ability to cause disease. This will allow us to gain insights on mechanisms by which Leptospira spp. cause disease, leading to development of better methods of disease control and prevention.
Regulatory Networks Controlling Virulence In Neisseria Gonorrhoeae And Neisseria Meningitidis.
Funder
National Health and Medical Research Council
Funding Amount
$147,500.00
Summary
Bacteria that cause disease produce substances called virulence determinants, often on their cell surface. These virulence determinants are either directly involved in allowing infection to take place, or cause the damage that we recognize as an infectious disease. Some virulence determinants are produced all the time, while others are only made under particular conditions, that is, their expression is regulated. To target efforts in the development of new vaccines and treatments, it is importan ....Bacteria that cause disease produce substances called virulence determinants, often on their cell surface. These virulence determinants are either directly involved in allowing infection to take place, or cause the damage that we recognize as an infectious disease. Some virulence determinants are produced all the time, while others are only made under particular conditions, that is, their expression is regulated. To target efforts in the development of new vaccines and treatments, it is important to identify all the virulence determinants produced by a particular bacterial species, but also to know which are regulated, and the environmental signals that determine their expression. Neisseria gonorrhoeae and Neisseria meningitidis are two important disease-causing bacteria that exclusively infect humans and cause gonorrhoea, and meningitis. The complete DNA sequence of both of these bacteria is now known. From computer analysis of these data, it appears that these bacteria have few of the specific regulatory systems that are present in other bacteria. Because of the limited repertoire of regulatory systems still present in N. gonorrhoeae and N. meningitidis, it is feasible to mutate each one and determine which are involved in regulation of virulence determinants. We have made copies of every individual gene found in the DNA sequence of these bacteria and have attached each one individually to a glass slide to form a microarray measuring 18mm x 18mm. This microarray will allow us to monitor the expression of every gene in these bacteria in response to environmental signals. This information will be used to identify all the virulence genes controlled by each regulatory system. Such an analysis has never been previously achieved for any bacterial species, because of the number and complexity of the regulatory systems usually present.Read moreRead less
Environmental Regulation Of Virulence In Attaching And Effacing Enterobacteria
Funder
National Health and Medical Research Council
Funding Amount
$569,063.00
Summary
Disease-causing bacteria must respond to the extreme conditions, such as acid and bile, which they encounter in their hosts. They achieve this by sensing their environment and activating genes that enhance their survival and ability to cause disease. In this project we will define the mechanisms by which these sensing and response pathways occur, using E. coli as a model. The information obtained from this research should lead to new strategies to treat and prevent bacterial infections.
Role Of Novel Mobile Elements In The Infiltration Of Antibiotic Resistance Genes Into Clinical Isolates.
Funder
National Health and Medical Research Council
Funding Amount
$421,650.00
Summary
Bacteria have a remarkable ability to capture and spread antibiotic resistance genes. This phenomenon is a particular problem in our hospitals and in the community as multi-drug resistant pathogenic organisms have been selected over time as a result of the use of antibitoics. Moreover the incidence of resistance appears to be on the increase. Once resistant strains appear they can greatly complicate the treatment of infections and the eradication of such pathogens from a hospital is both difficu ....Bacteria have a remarkable ability to capture and spread antibiotic resistance genes. This phenomenon is a particular problem in our hospitals and in the community as multi-drug resistant pathogenic organisms have been selected over time as a result of the use of antibitoics. Moreover the incidence of resistance appears to be on the increase. Once resistant strains appear they can greatly complicate the treatment of infections and the eradication of such pathogens from a hospital is both difficult and costly. We have been working on the problem of how antibiotic resistance genes are spread for a number of years and have identified a novel genetic element that can capture resistance genes by a process of site-specific recombination. This element, the integron, is common in mutli-drug resistant clinical isolates. To be captured by an integron, an antibiotic resistance gene has to be part of a mobile element known as a gene cassette. Although the application of antibiotics acts to amplify pathogens that are resistant and favours their persistance in hospitals, it is generally recognized that neither the gene cassette nor the drug resistance gene evolve in the hospital. Rather, these genes make their way into human pathogens from bacteria that normally reside in other environments, for example soil or water. In this project, we will investigate one route by which drug resistance genes and integrons might find their way into clinically relevant strains and what the sources of the resistance genes and gene cassettes might be. A greater understanding of these processes will help in developing strategies to limit the spread of drug resistant bacteria into and around hospitals.Read moreRead less
Characterisation Of The Key Role Played By The Persistent Phase Of Chlamydia Pneumoniae In Disease Pathogenesis
Funder
National Health and Medical Research Council
Funding Amount
$286,320.00
Summary
Chlamydia pneumoniae is a relatively newly identified pathogen that is responsible for several respiratory conditions such as, pneumonia and chronic obstructive pulmonary disease and has been strongly linked to heart disesae. Serious disease is due to low grade chronic infections, but we do not understand how the bacterium causes these chronic diseases. This project will identify markers of chronic C. pneumoniae infections and relate these to the disease that results. Identifying these markers o ....Chlamydia pneumoniae is a relatively newly identified pathogen that is responsible for several respiratory conditions such as, pneumonia and chronic obstructive pulmonary disease and has been strongly linked to heart disesae. Serious disease is due to low grade chronic infections, but we do not understand how the bacterium causes these chronic diseases. This project will identify markers of chronic C. pneumoniae infections and relate these to the disease that results. Identifying these markers of chronic disease should lead to improved methods of disease control, including new diagnostic tests, vaccines and new drug therapies.Read moreRead less
Characterisation Of A Novel Type Of Promoter Controlling Expression Of Virulence Genes In Neisseria.
Funder
National Health and Medical Research Council
Funding Amount
$200,880.00
Summary
This project will investigate how two different types of bacteria control genes that are involved in determining their disease-causing ability. The expression of many bacterial genes is controlled by a sophisticated battery of regulatory systems that respond to individual, very specific, environmental signals. Such regulatory systems are capable of exerting very precise control over the level of gene expression, in response to the concentration of specific molecules in the immediate environment. ....This project will investigate how two different types of bacteria control genes that are involved in determining their disease-causing ability. The expression of many bacterial genes is controlled by a sophisticated battery of regulatory systems that respond to individual, very specific, environmental signals. Such regulatory systems are capable of exerting very precise control over the level of gene expression, in response to the concentration of specific molecules in the immediate environment. However, there is evidence to suggest that many important disease-causing bacteria are much less reliant on specific regulatory systems. Instead, these bacteria rely more heavily what have been termed global systems for the regulation of gene expression. Such systems typically respond to less specific signals, such as the growth rate of the bacterial cell, but nevertheless appear capable of very precise control. We have evidence for a previously uncharacterised type of global control system that appears to be widespread amongst bacteria. It is likely that many virulence genes in a variety of disease-causing bacteria will prove to be controlled by similar means. Therefore this project will not only provide an insight into how expression of these particular virulence determinants is regulated, but will yield data that may help in our understanding of precise global regulatory processes in other bacterial species of medical importance.Read moreRead less
A group of bacteria called Neisseria cause human-specific infections. To initiate infection, the bacteria must produce a hair-like surface structure, the pilus. The pilus consists mainly of a protein called pilin, and we now understand how pilin production is controlled. However 20 other genes are also involved in pilus production. This project aims to understand how these other genes are controlled and coordinated to assemble this structure that is central to the ability to cause disease.
Virulence And Oxidative Stress In Streptococcus Pneumoniae
Funder
National Health and Medical Research Council
Funding Amount
$110,125.00
Summary
Streptococcus pneumoniae is an important human pathogen that causes pneumonia, meningitis and bacteraemia as well as otitis media in young children. It is a cause of high morbidity and mortality around the world. S. pneumoniae grows by fermentative metabolism, a characteristic of anaerobic organisms, but it is able to adapt towards oxygen in the environment. This adaptive ability enables S. pneumoniae to live under conditions of high oxygen tension (eg. the upper respiratory tract) or under almo ....Streptococcus pneumoniae is an important human pathogen that causes pneumonia, meningitis and bacteraemia as well as otitis media in young children. It is a cause of high morbidity and mortality around the world. S. pneumoniae grows by fermentative metabolism, a characteristic of anaerobic organisms, but it is able to adapt towards oxygen in the environment. This adaptive ability enables S. pneumoniae to live under conditions of high oxygen tension (eg. the upper respiratory tract) or under almost anaerobic conditions (eg. the middle ear) in the human body. The emergence of antibiotic resistant pneumococci and limitations of current vaccines has led to increased interest in understanding the molecular mechanisms of pathogenesis of this bacterium. Of particular interest has been the pneumococcal surface antigen PsaA, which has been shown to be a protective immunogen in mice. It has also been shown that psaA mutants exhibit massively reduced virulence in mice in intranasal and intraperitoneal challenge models. Taken together, these data have led to the suggestion that PsaA might be an effective vaccine antigen or antimicrobial target. We postulate that PsaA is involved in the oxidative stress response and virulence under aerobic conditions and have devised a study to determine the procise role of this protein in disease caused by Streptococcus pneumoniae.Read moreRead less
Multidrug Resistance Regulatory Protein QacR From Staphylococcus Aureus
Funder
National Health and Medical Research Council
Funding Amount
$459,750.00
Summary
One of the most significant mechanisms of drug resistance is the export of antibiotics and other chemotherapeutic drugs from the cell. Drug export systems are an important medical problem due to their frequent occurrence in bacteria and parasites which cause human disease, and in human cancer cells. Proteins which recognise and export a broad range of drugs from a cell are called multidrug efflux pumps. These multidrug efflux systems present a serious threat to patient care and to successful the ....One of the most significant mechanisms of drug resistance is the export of antibiotics and other chemotherapeutic drugs from the cell. Drug export systems are an important medical problem due to their frequent occurrence in bacteria and parasites which cause human disease, and in human cancer cells. Proteins which recognise and export a broad range of drugs from a cell are called multidrug efflux pumps. These multidrug efflux systems present a serious threat to patient care and to successful therapy, since the ability to produce a single protein simultaneously renders the cell or organism resistant to several different drugs. Strains of the bacterial pathogen Staphylococcus aureus or Golden Staph, which are endemic in hospitals world-wide, contain an example of such a multidrug exporter, the QacA multidrug efflux pump. QacA exports at least 30 different antimicrobial compounds, including antiseptics and disinfectants. Production of this protein is regulated by a sensor protein, QacR, which detects the presence of a number of these antimicrobial compounds. To understand how the QacR sensor protein can recognise such a wide variety of compounds, we will identify and structurally characterise the regions of the QacR multidrug regulatory protein which bind these compounds. Additionally, we will examine the means by which QacR regulates the production of the QacA pump protein. This project will provide fundamental knowledge that will not only help with understanding the important process of multidrug resistance but will also enable the rational design of more effective antibacterial compounds that either block or evade these multidrug efflux systems.Read moreRead less