The plasminogen activation system enhances brain and heart invasion in murine relapsing fever borreliosis.
ABSTRACT: The role of the plasminogen activation system (PAS) was investigated during the course of infection of a relapsing fever Borrelia species in plasminogen-deficient (plg -/-) and control (plg +/+ and plg +/-) mice. Subcutaneous inoculation of 10(4) spirochetes resulted in a peak spirochetemia five days after infection with 20-23 x 10(6) organisms per milliliter of whole blood in all mice, indicating that the PAS had no effect on the development of this phase of the infection. Anemia, thrombocytopenia, hepatitis, carditis, and splenomegaly were noted in all mice during and immediately after peak spirochetemia. Fibrin deposition in organs was noted in plg -/- mice but not in controls during these stages. Significantly greater spirochetal DNA burdens were consistently observed in the hearts and brains of control mice 28-30 days after infection, as determined by PCR amplification of this organism's flagellin gene (flaB), followed by quantitative densitometry. Furthermore, the decreased spirochetal load in brains of plg -/- mice was associated with a significant decrease in the degree of inflammation of the leptomeninges in these mice. These findings indicate a role for the PAS in heart and brain invasion by relapsing fever Borrelia, resulting in organ injury.
Project description:Relapsing fever is an infection characterized by peaks of spirochetemia attributable to antibody selection against variable serotypes. In the absence of B cells, serotypes cannot be cleared, resulting in persistent infection. We previously identified differences in spirochetemia and disease severity during persistent infection of severe combined immunodeficiency mice with isogenic serotypes 1 (Bt1) or 2 (Bt2) of Borrelia turicatae. To investigate this further, we studied pathogen load, clinical disease, cytokine/chemokine production, and inflammation in mice deficient in B (Igh6-/-) or B and T (Rag1-/-) cells persistently infected with Bt1 or Bt2. The results showed that Igh6-/- mice, despite lower spirochetemia, had a significantly aggravated disease course compared with Rag1-/- mice. Measurement of cytokines revealed a significant positive correlation between pathogen load and interleukin (IL)-10 in blood, brain, and heart. Bt2-infected Rag1-/- mice harbored the highest spirochetemia and, at the same time, displayed the highest IL-10 plasma levels. In the brain, Bt1, which was five times more neurotropic than Bt2, caused higher IL-10 production. Activated microglia were the main source of IL-10 in brain. IL-10 injected systemically reduced disease and spirochetemia. The results suggest IL-10 plays a protective role as a down-regulator of inflammation and pathogen load during infection with relapsing fever spirochetes.
Project description:The Lyme disease (Borrelia burgdorferi) and relapsing-fever (Borrelia hispanica) agents have distinct infection courses, but both require cholesterol for growth. They acquire cholesterol from the environment and process it to form cholesterol glycolipids that are incorporated onto their membranes. To determine whether higher levels of serum cholesterol could enhance the organ burdens of B. burgdorferi and the spirochetemia of B. hispanica in laboratory mice, apolipoprotein E (apoE)-deficient and low-density lipoprotein receptor (LDLR)-deficient mice that produce large amounts of serum cholesterol were infected with both spirochetes. Both apoE- and LDLR-deficient mice infected with B. burgdorferi had an increased number of spirochetes in the joints and inflamed ankles compared with the infected wild-type (WT) mice, suggesting that mutations in cholesterol transport that result in high serum cholesterol levels can affect the pathogenicity of B. burgdorferi. In contrast, elevated serum cholesterol did not lead to an increase in the spirochetemia of B. hispanica. In the LDLR-deficient mice, the course of infection was indistinguishable from the WT mice. However, infection of apoE-deficient mice with B. hispanica resulted in a longer spirochetemia and increased mortality. Together, these results argue for the apoE deficiency, and not hypercholesterolemia, as the cause for the increased severity with B. hispanica. Serum hyperlipidemias are common human diseases that could be a risk factor for increased severity in Lyme disease.
Project description:Relapsing fever Borrelia spp. undergo antigenic variation, achieve high levels in blood, and require rapid production of immunoglobulin M (IgM) for clearance. MyD88-deficient mice display defective clearance of many pathogens; however, the IgM response to persistent infection is essentially normal. Therefore, MyD88(-/-) mice provided a unique opportunity to study the effect of nonantibody, innate host defenses to relapsing fever Borrelia. Infected MyD88(-/-) mice harbored extremely high levels of B. hermsii in the blood compared to wild-type littermates. In the comparison of MyD88(-/-) mice and B- and T-cell-deficient scid mice, two features stood out: (i) bacterial numbers in blood were at least 10-fold greater in MyD88(-/-) mice than scid mice, even though the production of IgM still occurred in MyD88(-/-) mice; and (ii) many of the MyD88(-/-) mice were able to exert partial clearance, although with delayed kinetics relative to wild-type mice, a feature not seen in scid mice. Further analysis revealed a delay in the IgM response to lipoproteins expressed by the original inoculum; however, by 6 days of infection antibodies were produced in MyD88(-/-) mice that could clear spirochetemia in scid mice. While these results indicated that the production of IgM was delayed in MyD88(-/-) mice, they also point to a second, antibody-independent role for MyD88 signaling in host defense to relapsing fever Borrelia. This second defect was apparent only when antibody levels were limiting.
Project description:<h4>Background</h4>In the United States, Tick-Borne Relapsing Fever (TBRF) in dogs is caused by the spirochete bacteria Borrelia turicatae and Borrelia hermsii, transmitted by Ornithodoros spp. ticks. The hallmark diagnostic feature of this infection is the visualization of numerous spirochetes during standard blood smear examination. Although the course of spirochetemia has not been fully characterized in dogs, in humans infected with TBRF the episodes of spirochetemia and fever are intermittent.<h4>Objectives</h4>To describe TBRF in dogs by providing additional case reports and reviewing the disease in veterinary and human medicine.<h4>Animals</h4>Five cases of privately-owned dogs naturally infected with TBRF in Texas are reviewed.<h4>Methods</h4>Case series and literature review.<h4>Results</h4>All dogs were examined because of lethargy, inappetence, and pyrexia. Two dogs also had signs of neurologic disease. All dogs had thrombocytopenia and spirochetemia. All cases were administered tetracyclines orally. Platelet numbers improved and spirochetemia and pyrexia resolved in 4 out of 5 dogs, where follow-up information was available.<h4>Conclusion and clinical importance</h4>TBRF is likely underdiagnosed in veterinary medicine. In areas endemic to Ornithodoros spp. ticks, TBRF should be considered in dogs with thrombocytopenia. Examination of standard blood smears can provide a rapid and specific diagnosis of TBRF when spirochetes are observed.
Project description:DNA methyltransferases have been implicated in the regulation of virulence genes in a number of pathogens. Relapsing fever Borrelia species harbor a conserved, putative DNA methyltransferase gene on their chromosome, while no such ortholog can be found in the annotated genome of the Lyme disease agent, Borrelia burgdorferi. In the relapsing fever species Borrelia hermsii, the locus bh0463A encodes this putative DNA adenine methyltransferase (dam). To verify the function of the BH0463A protein product as a Dam, the gene was cloned into a Dam-deficient strain of Escherichia coli. Restriction fragment analysis subsequently demonstrated that complementation of this E. coli mutant with bh0463A restored adenine methylation, verifying bh0463A as a Dam. The requirement of bh0463A for B. hermsii viability, infectivity, and persistence was then investigated by genetically disrupting the gene. The dam- mutant was capable of infecting immunocompetent mice, and the mean level of spirochetemia in immunocompetent mice was not significantly different from wild type B. hermsii. Collectively, the data indicate that dam is dispensable for B. hermsii viability, infectivity, and persistence.
Project description:Tick-borne relapsing fever spirochetes are maintained in endemic foci that involve a diversity of small mammals and argasid ticks in the genus Ornithodoros. Most epidemiological studies of tick-borne relapsing fever in West Africa caused by Borrelia crocidurae have been conducted in Senegal. The risk for humans to acquire relapsing fever in Mali is uncertain, as only a few human cases have been identified. Given the high incidence of malaria in Mali, and the potential to confuse the clinical diagnosis of these two diseases, we initiated studies to determine if there were endemic foci of relapsing fever spirochetes that could pose a risk for human infection.We investigated 20 villages across southern Mali for the presence of relapsing fever spirochetes. Small mammals were captured, thin blood smears were examined microscopically for spirochetes, and serum samples were tested for antibodies to relapsing fever spirochetes. Ornithodoros sonrai ticks were collected and examined for spirochetal infection. In total, 11.0% of the 663 rodents and 14.3% of the 63 shrews tested were seropositive and 2.2% of the animals had active spirochete infections when captured. In the Bandiagara region, the prevalence of infection was higher with 35% of the animals seropositive and 10% infected. Here also Ornithodoros sonrai were abundant and 17.3% of 278 individual ticks tested were infected with Borrelia crocidurae. Fifteen isolates of B. crocidurae were established and characterized by multi-locus sequence typing.The potential for human tick-borne relapsing fever exists in many areas of southern Mali.
Project description:Relapsing fever (RF) is an acute infectious disease caused by arthropod-borne spirochetes of the genus Borrelia. The disease is characterized by recurrent episodes of fever that concur with spirochetemia. The RF borrelioses include louse-borne RF caused by Borrelia recurrentis and tick-borne endemic RF transmitted by argasid soft ticks and caused by several Borrelia spp. such as B. crocidurae, B. coriaceae, B. duttoni, B. hermsii, B. hispanica and B. persica. Human infection with B. persica is transmitted by the soft tick Ornithodoros tholozani and has been reported from Iran, Israel, Egypt, India, and Central Asia.During 2003-2015, five cats and five dogs from northern, central and southern Israel were presented for veterinary care and detected with borrelia spirochetemia by blood smear microscopy. The causative infective agent in these animals was identified and characterized by PCR from blood and sequencing of parts of the flagellin (flab), 16S rRNA and glycerophosphodiester phosphodiestrase (GlpQ) genes.All animals were infected with B. persica genetically identical to the causative agent of human RF. Phylogenetic analysis indicated that DNA sequences from these pet carnivores clustered together with B. persica genotypes I and II from humans and O. tholozani ticks and distinctly from other RF Borrelia spp. The main clinical findings in cats included lethargy, anorexia, anemia in 5/5 cats and thrombocytopenia in 4/5. All dogs were lethargic and anorectic, 4/5 were febrile and anemic and 3/5 were thrombocytopenic. Three dogs were co-infected with Babesia spp. The animals were all treated with antibiotics and the survival rate of both dogs and cats was 80 %. The cat and dog that succumbed to disease died one day after the initiation of antibiotic treatment, while survival in the others was followed by the rapid disappearance of spirochetemia.This is the first report of disease due to B. persica infection in cats and the first case series in dogs. Infection was associated with anemia and thrombocytopenia. Fever was more frequently observed in dogs than cats. Domestic canines and felines suffer from clinical disease due to B. persica infection and may also serve as sentinels for human infection.
Project description:Asthma is a syndrome whose common pathogenic expression is inflammation of the airways. Plasminogen plays an important role in cell migration and is also implicated in tissue remodeling, but its role in asthma has not been defined.To test whether plasminogen is a critical component in the development of asthma.We used a mouse model of ovalbumin-induced pulmonary inflammation in Plg(+/+), Plg(+/-), and Plg(-/-) mice.The host responses measured included lung morphometry, and inflammatory mediators and cell counts were assessed in bronchoalveolar lavage fluid. Bronchoalveolar lavage demonstrated a marked increase in eosinophils and lymphocytes in ovalbumin-treated Plg(+/+) mice, which were reduced to phosphate-buffered saline-treated control levels in Plg(+/-) or Plg(-/-) mice. Lung histology revealed peribronchial and perivascular leukocytosis, mucus production, and increased collagen deposition in ovalbumin-treated Plg(+/+) but not in Plg(+/-) or Plg(-/-) mice. IL-5, tumor necrosis factor-alpha, and gelatinases, known mediators of asthma, were detected in bronchoalveolar lavage fluid of ovalbumin-treated Plg(+/+) mice, yet were reduced in Plg(-/-) mice. Administration of the plasminogen inhibitor, tranexamic acid, reduced eosinophil and lymphocyte numbers, mucus production, and collagen deposition in the lungs of ovalbumin-treated Plg(+/+) mice.The decreased inflammation in the lungs of Plg(-/-) mice and its blockade with a plasminogen inhibitor indicate that plasminogen plays an important role in orchestrating the asthmatic response and suggests that plasminogen may be a therapeutic target for the treatment of asthma.
Project description:Skin damage caused by radiation therapy (radiodermatitis) is a severe side effect of radiotherapy in cancer patients, and there is currently a lack of effective strategies to prevent or treat such skin damage. In this work, we show with several lines of evidence that plasminogen, a pro-inflammatory factor, is key for the development of radiodermatitis. After skin irradiation in wild-type (plg+/+) mice, the plasminogen level increased in the irradiated area, leading to severe skin damage such as ulcer formation. However, plasminogen-deficient (plg-/-) mice and mice lacking plasminogen activators were mostly resistant to radiodermatitis. Moreover, treatment with a plasminogen inhibitor, tranexamic acid, decreased radiodermatitis in plg+/+ mice and prevented radiodermatitis in plg+/- mice. Together with studies at the molecular level, we report that plasmin is required for the induction of inflammation after irradiation that leads to radiodermatitis, and we propose that inhibition of plasminogen activation can be a novel treatment strategy to reduce and prevent the occurrence of radiodermatitis in patients.
Project description:Lyme disease (LD), the most prevalent tick-borne illness in North America, is caused by Borrelia burgdorferi The long-term survival of B. burgdorferi spirochetes in the mammalian host is achieved though VlsE-mediated antigenic variation. It is mathematically predicted that a highly variable surface antigen prolongs bacterial infection sufficiently to exhaust the immune response directed toward invariant surface antigens. If the prediction is correct, it is expected that the antibody response to B. burgdorferi invariant antigens will become nonprotective as B. burgdorferi infection progresses. To test this assumption, changes in the protective efficacy of the immune response to B. burgdorferi surface antigens were monitored via a superinfection model over the course of 70 days. B. burgdorferi-infected mice were subjected to secondary challenge by heterologous B. burgdorferi at different time points postinfection (p.i.). When the infected mice were superinfected with a VlsE-deficient clone (?VlsE) at day 28 p.i., the active anti-B. burgdorferi immune response did not prevent ?VlsE-induced spirochetemia. In contrast, most mice blocked culture-detectable spirochetemia induced by wild-type B. burgdorferi (WT), indicating that VlsE was likely the primary target of the antibody response. As the B. burgdorferi infection further progressed, however, reversed outcomes were observed. At day 70 p.i. the host immune response to non-VlsE antigens became sufficiently potent to clear spirochetemia induced by ?VlsE and yet failed to prevent WT-induced spirochetemia. To test if any significant changes in the anti-B. burgdorferi antibody repertoire accounted for the observed outcomes, global profiles of antibody specificities were determined. However, comparison of mimotopes revealed no major difference between day 28 and day 70 antibody repertoires.