Progress 06/01/97 to 09/30/05
Outputs
This project was initially established to report all activities relating to Dr. Barthold's research in the area of human granulocytic ehrlichiosis or lyme disease. Subsequently several projects were established to report progress on individual projects rather than collectively. This project has since been replaced by: 'Non-human primate animal models for experimental reserach on chronic lymp neuroborreliosis' (CALV-NewJersey02-) and 'Immunopathogenesis of granulocytic ehrlichiosis' (CALV-Yale02-AI41440). This project, therefore, is being terminated.
Impacts
Dr. Barthold's research involves studying the immunology and pathogenesis of lyme disease.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Using the mouse model, Dr. Barthold's group has discovered that B. burgdorferi up-regulates several key antigens within the feeding tick and in vivo during the course of infection, and these antigens are the principal targets for protective and disease-resolving immune responses. Because these biologically relevant immune responses are B cell-mediated, a B. burgdorferi genomic expression library is being screened with serum from infected mice. The group has incriminated, cloned and expressed key antigens that elicit either protective immunity or arthritis-resolving immunity. Using the mouse model, the group is also investigating deleterious immune reactions that elicit autoimmunity, which are suspected in chronic Lyme disease patients, as well as mechanisms by which B. burgdorferi evades immune clearance. Dr. Barthold has also utilized the mouse model to develop and test a recombinant outer surface protein A (OspA) vaccine that has been approved by the FDA for human
use, and has been proven efficacious as a dog vaccine. Ongoing efforts are focused on development of second-generation protective vaccines and therapeutic vaccines.
Impacts
Lyme disease is a tick-borne infectious disease of humans and animals. Inoculation of Borrelia burgdorferi into laboratory mice results in development of arthritis, carditis and neurologic disease within the first few weeks of infection. Arthritis and carditis resolve and recur episodically over the course of persistent infection. These are key features of Lyme disease in humans and some domestic animals (dogs, horses, etc.). Despite persistent infection, infected hosts (mice, dogs and humans) develop protective and disease-resolving immune responses that are B cell-mediated and T cell-independent.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
Despite significant advances in understanding the biology of Borrelia burgdorferi, the agent of Lyme disease, the pathogenesis of Lyme disease remains poorly understood. The overall objective of this project is to use a mouse model of Lyme disease to investigate spirochete population kinetics and differential expression of specific Borrelia burgdorferi genes in selected target tissues during the dissemination/disease evolution phase, disease resolution (immune) phase, and persistent phases of B. burgdorferi infection. We continue the search for B. burgdorferi antigens associated with biologically relevant antibody responses by screening a B. burgdotferi genomic expression library with sera from infected mice. Recombinant proteins and antisera were tested for biologic activity (protective, disease- resolving, and dissemination-preventing activity) in the model. We examined prototype gene expression during different phases of infection, and examined the effects of
immunity or immune tolerance to biologically relevant antigens on these events. We investigate mechanisms of persistent infection and disease quiecence by examining expression of prototype genes during this phase of infection, and defining antigens that are involved in maintaining the host-agent equillibrium.
Impacts
During the past project period, gene products were defined that are associated with antibody- mediated protective, but not arthritis- or carditis-resolving immunity (DbpA), and gene products that are associated with arthritis-, but not carditisresolving or protective immunity. In the current project period, the search will continue for other arthritis- and carditis- resolving antigen targets, as well as to characterize antigens expressed during persistent infection. Highly sensitive assays (real time PCR) have been optimized for quantitative analysis of spirochete population kinetics and for examining prototype gene expression in tissues at different stages of infection.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
The bacterial population kinetics were followed in mice for up to 1 year of infection. Following syringe or tick-borne infection, spirochete numbers rose during early phase of infection , then declined, but persisted in all tissues for 1 year. Spirochete numbers did not correlate with exacerbation of disease during persistence. We also determined passive immunizing antibody titers during the course of persistent infection. Titers peaked at 60 days, then declined but plateaued throughout persistent infection. No correlation was found between passive immunizing titer and disease exacerbation. A major thrust of this project was to screen a genomic expression library to identify immunogenic clones that expressed recombinant proteins that might serve to incriminate antigens responsible for protective immunity. Over 60 clones were obtained and characterized, many of which were replicates of the same genes. A number of clones expressed decorin binding protein A. which we
found to be protective against syringe and tick challenge. On further analysis, however, persistent spirochetes were detectable at the site of inoculation or feeding in DbpA-immunized mice. Thus, DbpA immunity did not prevent infection, but rather prevented spread of spirochetes to other tissues. This project also uncovered another immunogenic protein, arthritis-related protein (Arp), which did not elicit protective immunity. However, upon further investigation of this protein, it has been found to induce arthritis resolution. The final aim of this project was to examine mRNA expression of selected gene targets in various tissues during persistent infection. This aim proved to be the most difficult. Although we effectively showed mRNA transcription of selected genes in various tissues, sensitivity did not allow this to be applied quantitatively.
Impacts
This project continues to expand our knowledge of Lyme disease.
Publications
- Barthold SW: Lyme borrelosis. In: Nataro JP, Blaser MJ, Cummingham-Rundles S (eds), Persistent Bacterial Infections. 1999. Academic Press. In-Press.
- Hodzic E, Feng S, Barthold SW. Stability of Borrelia burgdorferi OspC under immune selection pressure. 2000. J. Infect Dis, 181:750-753.
- Germen J, Ryckmann B, Moro M, Hofmeister e, Barthold SW, Bockenstedt L, Persing DH. 1999. Quantitative detection of Borrelia burgdorferi with a microtiter-based competitive polymerase chain reaction assay. Mol. Diagnosis, 4:185-193.
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Progress 01/01/99 to 12/31/99
Outputs
This project examines both protective as well as disease modulating immunity in the mouse model following tick-borne challenge. The PI can accurately assess infection in mice by a well-established record of sensitive culture, as well as PCR detection of B. burgdorferi genes targets, quantitative PCR, serology and histopathology. Currently they are studying utilizing mutant mice with targeted gene disruptions (knock out mice) that result in selective immune deficiencies. These mice have proven to be powerful research tools. In brief, they have found that critical host immune responses during infection are T cell-independent, B cell responses. This greatly narrows the search for antigens involve din protective and arthritis-resolving immune responses, both of which occur in T cell deficient mice. Using these mice, they have discovered that acquired T cell responses during infection are actually deleterious to the host, causing more severe arthritis and carditis.
Impacts
These observations have far-reaching consequences in our understanding of Lyme disease immunopathogenesis and incrimination of immunogenic antigen involved in effective host immunity.
Publications
- A complete lisiting of publications for 1999 may be obtained from the Center for Comparative Medicine, University of California Davis, Davis California 95616.
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