Single exposure of mice to Borrelia burgdorferi elicits immunoglobulin G antibodies characteristic of secondary immune response without production of interleukin-4 by immune T cells

Seroprevalence of Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum Infections in German Horses

There are limited data on Lyme borreliosis (LB), a tick-borne disease caused by the Borrelia burgdorferi sensu lato complex, in horses. Seropositivity is not necessarily associated with clinical disease. Data on seropositivity against Borrelia burgdorferi and Anaplasma phagocytophilum in German horses are sparse. Therefore, serum samples from horses (n = 123) suspected of having Lyme borreliosis and clinically healthy horses (n = 113) from the same stables were tested for specific antibodies against Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum. The samples were screened for antibodies against Borrelia burgdorferi (ELISA and an IgG line immunoblot assay). Furthermore, the samples were examined for antibodies against B. burgdorferi and Anaplasma phagocytophilum with a validated rapid in-house test (SNAP^® 4Dx Plus^® ELISA). The clinical signs of suspect horses included lameness (n = 36), poor performance (n = 19), and apathy (n = 12). Twenty-three percent (n = 26) of suspect horses and 17% (n = 18) of clinically healthy horses were seropositive for having a Borrelia burgdorferi sensu lato infection (p = 0.371), showing that the detection of specific antibodies against B. burgdorferi alone is not sufficient for a diagnosis of equine LB. Anaplasma phagocytophilum seropositivity and seropositivity against both pathogens was 20%/6% in suspect horses and 16%/2% in the clinically healthy population, showing only minor differences (p = 0.108). Unspecific testing for antibodies against B. burgdorferi without clinical suspicion of Lyme borreliosis is not recommended since the clinical relevance of seropositivity against Borrelia burgdorferi sensu lato remains to be elucidated.

Susceptibility to experimental Lyme arthritis correlates with KC and monocyte chemoattractant protein-1 production in joints and requires neutrophil recruitment via CXCR2

The development of experimental Lyme arthritis has been correlated with the expression of a number of chemokines and cytokines, however, none of these have been measured directly from the arthritic joint. We examined the temporal expression of IL-1beta, IL-4, IL-6, IL-10, IL-12p70, GM-CSF, IFN-gamma, TNF-alpha, macrophage inflammatory protein-2, KC, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1 directly from the tibiotarsal joint in arthritis-resistant C57BL/6 (B6) and -susceptible C3H/He (C3H) mice. Only the chemokines KC and monocyte chemoattractant protein-1 were differentially expressed in joints of B6 and C3H mice and correlated with the development of Lyme arthritis. Infection of CXCR2(-/-) mice on either genetic background resulted in a significant decrease in the development of pathology, although infection of CCR2(-/-) mice had little or no effect. Neutrophils in CXCR2(-/-) mice were marginalized within blood vessels and could not enter the joint tissue. These results suggest that chemokine-mediated recruitment of neutrophils into the infected joint is a key requirement for the development of experimental Lyme arthritis.

Protection against tick-transmitted Lyme disease in dogs vaccinated with a multiantigenic vaccine

In an effort to develop a safe and effective vaccine for the prevention of Lyme borreliosis that addresses concerns raised over currently available vaccines, dogs were vaccinated twice with a multiantigenic preparation of Borrelia burgdorferi, strain N40, on days 0 and 20 of the experiment. About 70 and 154 days after the first immunization, dogs were challenged by exposing them to field-collected Ixodes scapularis ticks harboring B. burgdorferi. Vaccinated dogs were completely protected from infection by all criteria utilized to assess infection, developed high-titer anti-B. burgdorferi serum antibodies and growth inhibitory activity which persisted for over 200 days, and did not demonstrate any untoward consequence of vaccination. Serum absorption experiments revealed that borreliacidal and most likely protective antibodies in dogs receiving the multiantigenic preparation were not only elicited against the OspA antigen, but were also produced against additional yet to be determined targets on B. burgdorferi organisms. These data demonstrate that a multiantigenic vaccine is effective in preventing Lyme disease transmitted via the natural vector.

Cell-mediated immune response to high-passage Borrelia spirochetes in C57bl/6 mice is strictly dependent on antigen specificity

Inbred C57bl/6 mice were challenged with high-passage Borrelia afzelii, Borrelia garinii and Borrelia burgdorferi sensu stricto and tested for antigen specific T-cell response in vitro. Sonicated preparations of washed spirochetes were potent cell activators, capable of stimulating polyclonal proliferation after 72h of culture while increasing the incubation time up to 120h provoked specific cell-mediated response. Isolated murine spleocytes previously sensitized to B. burgdorferi sensu lato but not those from control mice could be induced for antigen-specific proliferation in vitro, as revealed by [3H]thymidine incorporation assay, Moreover, in mice presensitized to B. burgdorferi sensu lato, detectable cell-mediated response could be induced only with antigen preparations derived from a corresponding strain but not with those obtained from other Borrelia genospecies. The current study emphasises that the B. burgdorferi antigen-specific response may also be expected in different genospecies infections in men.

The cell-mediated immune response to Borrelia afzelii, garinii and burgdorferi in C57BL/6 mice is dependent on antigen specificity

Inbred C57BL/6 mice were challenged with Borrelia afzelii, Borrelia garinii and Borrelia burgdorferi sensu stricto and tested for antigen-specific T-cell response in vitro. The sonicated preparations of in vitro grown spirochetes were capable of stimulating polyclonal proliferation and specific cell-mediated response, depending on duration of the cell culture. Murine splenocytes previously sensitized to B. burgdorferi sensu lato (s.l. ), but not those from control mice, could be induced for antigen-specific proliferation in vitro. Moreover, detectable cell-mediated response could be induced only with antigen preparations derived from a corresponding strain but not with those obtained from other Borrelia genospecies as revealed by the [(3)H]thymidine incorporation assay. The current study considers that the strict B. burgdorferi s.l. antigen-specific response may also be expected in infections in humans and contributes to the explanation of the frequently poor antibody- and cell-mediated immune response observed in patients diagnosed with Lyme disease.

Defensins act as potent adjuvants that promote cellular and humoral immune responses in mice to a lymphoma idiotype and carrier antigens

Defensins released by neutrophils are able to kill a broad spectrum of microbes. They also induce leukocyte migration in vitro and elicit inflammatory leukocyte responses at s.c. injection sites in mice. In vitro experiments showed that human defensins enhanced concanavalin A-stimulated murine spleen cell proliferation and IFN-gamma production. This led us to examine the effects of human defensins on specific immune responses in vivo. BALB/c mice were immunized with 50 microg of keyhole limpet hemocyanin (KLH) adsorbed to aluminum hydroxide and administered with defensins in aqueous solution. Intraperitoneal administration of defensins significantly increased the production of KLH-specific IgG1, IgG2a and IgG2b antibodies 14 days after immunization. In vitro splenic KLH-specific proliferative responses were higher in mice treated with KLH and defensins than in those treated with KLH alone. Increased IFN-gamma and, to a lesser extent, IL-4 production were also detected in the supernatants of ex vivoKLH-activated spleen cells from mice treated with defensins. Finally, defensins significantly enhanced the antibody response to a syngeneic tumor antigen, lymphoma Ig idiotype and also augmented resistance to tumor challenge. These results indicate that defensins act as potent immune adjuvants by inducing the production of lymphokines, which promote T cell-dependent cellular immunity and antigen-specific Ig production. Thus, defensins appear to function as neutrophil-derived signals that promote adaptive immune responses.

Improvement of the immune response against plasmid DNA encoding OspC of Borrelia by an ER-targeting leader sequence

The present study outlines the characterization of a DNA-based immune response against the OspC antigen, one of the most promising candidates for a Borrelia vaccine. Balb/c mice were injected intradermally with plasmid DNA encoding the OspC gene (lacking the natural leader sequence) under transcriptional control of the cytomegalovirus (CMV) promotor. Immunization with this construct elicited only a marginal response, which was drastically improved by a fusion construct containing the human tissue plasminogen activator (hTPA) signal sequence. The results indicate that for DNA-based immunization against OspC an ER-targeting signal may be necessary for both antibody production as well as cellular immune responses.

Experimental lyme arthritis in the absence of interleukin-4 or gamma interferon

Genetic resistance and susceptibility to experimental Lyme arthritis have been linked with the production of interleukin-4 (IL-4) or gamma interferon (IFN-gamma), respectively. To determine the absolute requirement for these cytokines in disease outcome, we compared arthritis development in wild-type, IL-4-deficient (IL-4 degrees ), and IFN-gamma-deficient (IFN-gamma degrees ) mice. While susceptible C3H mice developed swelling of ankle joints during the second week of infection, this swelling was exacerbated in C3H IFN-gamma degrees mice. Their arthritis severity scores at day 21, however, were similar. Resolution of arthritis was also similar between C3H and C3H IFN-gamma degrees mice. Arthritis-resistant DBA mice did not develop ankle swelling during the experimental period. There were no differences in ankle swelling or arthritis severity scores between control DBA mice and DBA IL-4 degrees mice at any of the time points tested. While the presence of spirochetes in various tissues was similar among all strains at day 21, DBA IL-4 degrees mice had a higher presence of spirochetes in blood, heart, and spleen than the DBA, C3H, and C3H IFN-gamma degrees mice did at day 60. DBA IL-4 degrees mice also had impaired ability to produce Borrelia-specific antibody responses, especially immunoglobulin G1. Thus, while IFN-gamma and IL-4 are not absolutely required for arthritis susceptibility or resistance, the production of IL-4 does appear to play an important role in Borrelia-specific antibody production and spirochete clearance.

Multidose streptozotocin induction of diabetes in BALB/cBy mice induces a T cell proliferation defect in thymocytes which is reversible by interleukin-4

Thymic T cell function in streptozotocin-treated (STZ) diabetic mice has been examined. STZ administration suppresses thymic T cell proliferation in response to mitogen stimulation in vitro. Secretion of IL-4 was dramatically reduced; however, secretion of IL-2 or IFN-gamma was not significantly inhibited. RT-PCR analysis of thymocyte RNA revealed that levels of IL-4 mRNA were dramatically decreased in STZ-treated mice. Levels of mRNA encoding IFN-gamma were similar, but the appearance was delayed in thymocytes derived from STZ-treated mice, implying differential regulation of IL-4 and IFN-gamma. Defective thymocyte proliferation was partially restored by exposure to IL-2 in vitro; however, IL-4 completely reversed the STZ-induced defect. Administration in vivo of IL-4 before STZ treatment reversed the STZ-induced thymocyte proliferation defect and prevented both pancreatic islet destruction and hyperglycemia. Thymocyte cell surface differentiation markers were not appreciably different from control mice. Collectively these experiments suggest that STZ treatment of mice reduces expression of IL-4 which is associated with development of autoimmune diabetes.

Soluble proteins isolated from Borrelia burgdorferi by extraction with Triton X-114 confer resistance to experimental infection

Fractionation of Borrelia burgdorferi was made by extraction of infectious spirochetes using the detergent Triton X-114. Gel electrophoresis analysis of hydrophilic and hydrophobic proteins demonstrated that detergent extraction resulted in two populations of proteins with nonoverlapping electrophoretic profiles. Immunoblot analysis with monoclonal antibodies reactive with two abundant membrane proteins demonstrated that hydrophilic proteins were uncontaminated with hydrophobic proteins. In addition, assay of thymidine incorporation into and secretion of tumor necrosis factor-alpha from splenocytes cocultured in vitro with either detergent or aqueous phase proteins showed that lymphocyte mitogenic and macrophage activation activities of B. burgdorferi were completely absent from the hydrophilic phase proteins. The Triton X-114 aqueous and detergent phase proteins were used to immunize BALB/c and separately microMT/microMT (B cell knockout) mice that were subsequently challenged with infectious B. burgdorferi. The hydrophilic phase proteins were able to induce protective resistance to infection in either strain of mice demonstrating that potential candidate vaccine antigens are contained in the biochemical class of antigens which is devoid of both lymphocyte mitogen activity and major outer surface proteins. Furthermore, the ability to vaccinate B cell knockout mice suggests that the humoral antispirochete immune response is not the exclusive basis for protective immunity.

Administration of silica sensitizes lipopolysaccharide responsiveness of murine macrophages but inhibits T and B cell priming by inhibition of antigen presenting function

Macrophages play a key role in natural host defense against infection by a variety of pathogens. In addition, macrophages initiate the development of acquired immunity via antigen processing and presentation. The role of macrophages in resistance to pathogens, the development of autoimmune diseases and the induction of acquired immunity has been studied by treatment of rodents with reagents which are cytotoxic. We have studied the effects of one such reagent, silica, on the function of spleen macrophages and peritoneal exudate cells (PEC). Intraperitoneal administration of silica caused the accumulation of spleen macrophages and neutrophils, reduction in the number of B cells and had a modest effect on T cell abundance. The percentage of CD11b+ PEC was not affected by silica treatment but total PEC recovery was diminished 5-8 fold. Silica treatment did not cause release of TNF-alpha or IL-1-beta but, when stimulated with lipopolysaccharide (LPS) in vitro after silica treatment, PEC or spleen macrophages produced elevated levels of both cytokines compared to controls. In contrast, release of IL-12 from non-LPS treated PEC was stimulated 4-5 fold by silica treatment. In addition, sensitivity to LPS toxicity in vivo was significantly enhanced by silica. The ability of macrophages to present antigen to a T cell clone in vitro was found to be dramatically inhibited by silica treatment, as was the ability to prime antigen-specific T cells and B cells by antigen injection. Collectively these data demonstrate that silica treatment enhances macrophage sensitivity to LPS exposure but inhibits antigen processing and presentation.

Lyme disease: a review of aspects of its immunology and immunopathogenesis

Lyme disease, caused by Borrelia burgdorferi, causes a multisystem inflammatory ailment, although the precise means of tissue damage are not well understood. It is clear that the organism is present at the site of inflammation in many organs and that many of the features of the illness are relieved by antibiotic therapy. A complex interaction between spirochete and immune systems of a number of mammalian hosts, in human disease and animal models, has been described. It is clear that T cells and macrophages are intimately associated with the pathogenesis of arthritis and that immune mechanisms are involved in other aspects of disease. Inflammation directed at persistence of Borrelial antigens is a plausible explanation for persisting arthritis. Autoimmunity based on molecular mimicry may play a role in the pathogenesis of Lyme disease. Humoral immunity plays a protective role, prompting interest in vaccine development. Significant variation in certain of the outer surface proteins suggests that multiple proteins, peptides, or chimeric vaccines may be needed to provide a sufficiently broad humoral protective response.