Borrelia burgdorferi infection of the brain: characterization of the organism and response to antibiotics and immune sera in the mouse model

Age-Related Differential Stimulation of Immune Response by Babesia microti and Borrelia burgdorferi During Acute Phase of Infection Affects Disease Severity

Lyme disease is the most prominent tick-borne disease with 300,000 cases estimated by CDC every year while ~2,000 cases of babesiosis occur per year in the United States. Simultaneous infection with Babesia microti and Borrelia burgdorferi are now the most common tick-transmitted coinfections in the U.S.A., and they are a serious health problem because coinfected patients show more intense and persisting disease symptoms. B. burgdorferi is an extracellular spirochete responsible for systemic Lyme disease while B. microti is a protozoan that infects erythrocytes and causes babesiosis. Immune status and spleen health are important for resolution of babesiosis, which is more severe and even fatal in the elderly and splenectomized patients. Therefore, we investigated the effect of each pathogen on host immune response and consequently on severity of disease manifestations in both young, and 30 weeks old C3H mice. At the acute stage of infection, Th1 polarization in young mice spleen was associated with increased IFN-γ and TNF-α producing T cells and a high Tregs/Th17 ratio. Together, these changes could help in the resolution of both infections in young mice and also prevent fatality by B. microti infection as observed with WA-1 strain of Babesia. In older mature mice, Th2 polarization at acute phase of B. burgdorferi infection could play a more effective role in preventing Lyme disease symptoms. As a result, enhanced B. burgdorferi survival and increased tissue colonization results in severe Lyme arthritis only in young coinfected mice. At 3 weeks post-infection, diminished pathogen-specific antibody production in coinfected young, but not older mice, as compared to mice infected with each pathogen individually may also contribute to increased inflammation observed due to B. burgdorferi infection, thus causing persistent Lyme disease observed in coinfected mice and reported in patients. Thus, higher combined proinflammatory response to B. burgdorferi due to Th1 and Th17 cells likely reduced B. microti parasitemia significantly only in young mice later in infection, while the presence of B. microti reduced humoral immunity later in infection and enhanced tissue colonization by Lyme spirochetes in these mice even at the acute stage, thereby increasing inflammatory arthritis.

Infection Kinetics and Tropism of Borrelia burgdorferi sensu lato in Mouse After Natural (via Ticks) or Artificial (Needle) Infection Depends on the Bacterial Strain

Borrelia burgdorferi sl is a complex of pathogen bacteria transmitted to the host by Ixodes ticks. European Ixodes ricinus ticks transmit different B. burgdorferi species, pathogenic to human. Bacteria are principally present in unfed tick midgut, then migrate to salivary glands during blood meal and infect a new host via saliva. In this study, efficiency of transmission in a mouse model of three pathogen species belonging to the B. burgdorferi sl complex, B. burgdorferi sensu stricto (B31, N40, and BRE-13), B. afzelii (IBS-5), and B. bavariensis (PBi) is examined in order to evaluate infection risk after tick bite. We compared the dissemination of the Borrelia species in mice after tick bite and needle injection. Location in the ticks and transmission to mice were also determined for the three species by following infection kinetics. After inoculation, we found a significant prevalence in the brain for PBi and BRE-13, in the heart, for PBi, in the skin where B31 was more prevalent than PBi and in the ankle where both B31 and N40 were more present than PBi. After tick bite, statistical analyses showed that BRE-13 was more prevalent than N40 in the brain, in the bladder and in the inguinal lymph node. When Borrelia dissemination was compared after inoculation and tick bite, we observed heart infection only after tick inoculation of BRE-13, and PBi was only detected after tick bite in the skin. For N40, a higher number of positive organs was found after inoculation compared to tick bite. All European B. burgdorferi sl strains studied were detected in female salivary glands before blood meal and infected mice within 24 h of tick bite. Moreover, Borrelia-infected nymphs were able to infect mice as early as 12 h of tick attachment. Our study shows the need to remove ticks as early as possible after attachment. Moreover, Borrelia tropism varied according to the strain as well as between ticks bite and needle inoculation, confirming the association between some strains and clinical manifestation of Lyme borreliosis, as well as the role played by tick saliva in the efficiency of Borrelia infection and dissemination in vertebrates.

Borrelia burgdorferi adhere to blood vessels in the dura mater and are associated with increased meningeal T cells during murine disseminated borreliosis

Borrelia burgdorferi, the causative agent of Lyme disease, is a vector-borne bacterial infection that is transmitted through the bite of an infected tick. If not treated with antibiotics during the early stages of infection, disseminated infection can spread to the central nervous system (CNS). In non-human primates (NHPs) it has been demonstrated that the leptomeninges are among the tissues colonized by B. burgdorferi spirochetes. Although the NHP model parallels aspects of human borreliosis, a small rodent model would be ideal to study the trafficking of spirochetes and immune cells into the CNS. Here we show that during early and late disseminated infection, B. burgdorferi infects the meninges of intradermally infected mice, and is associated with concurrent increases in meningeal T cells. We found that the dura mater was consistently culture positive for spirochetes in transcardially perfused mice, independent of the strain of B. burgdorferi used. Within the dura mater, spirochetes were preferentially located in vascular regions, but were also present in perivascular, and extravascular regions, as late as 75 days post-infection. At the same end-point, we observed significant increases in the number of CD3+ T cells within the pia and dura mater, as compared to controls. Flow cytometric analysis of leukocytes isolated from the dura mater revealed that CD3+ cell populations were comprised of both CD4 and CD8 T cells. Overall, our data demonstrate that similarly to infection in peripheral tissues, spirochetes adhere to the dura mater during disseminated infection, and are associated with increases in the number of meningeal T cells. Collectively, our results demonstrate that there are aspects of B. burgdorferi meningeal infection that can be modelled in laboratory mice, suggesting that mice may be useful for elucidating mechanisms of meningeal pathogenesis by B. burgdorferi.

Hyperglycemia Impairs Neutrophil-Mediated Bacterial Clearance in Mice Infected with the Lyme Disease Pathogen

Insulin-insufficient type 1 diabetes is associated with attenuated bactericidal function of neutrophils, which are key mediators of innate immune responses to microbes as well as pathological inflammatory processes. Neutrophils are central to immune responses to the Lyme pathogen Borrelia burgdorferi. The effect of hyperglycemia on host susceptibility to and outcomes of B. burgdorferi infection has not been examined. The present study investigated the impact of sustained obesity-independent hyperglycemia in mice on bacterial clearance, inflammatory pathology and neutrophil responses to B. burgdorferi. Hyperglycemia was associated with reduced arthritis incidence but more widespread tissue colonization and reduced clearance of bacterial DNA in multiple tissues including brain, heart, liver, lung and knee joint. B. burgdorferi uptake and killing were impaired in neutrophils isolated from hyperglycemic mice. Thus, attenuated neutrophil function in insulin-insufficient hyperglycemia was associated with reduced B. burgdorferi clearance in target organs. These data suggest that investigating the effects of comorbid conditions such as diabetes on outcomes of B. burgdorferi infections in humans may be warranted.

Lyme neuroborreliosis: infection, immunity, and inflammation

Lyme neuroborreliosis (LNB), the neurological manifestation of systemic infection with the complex spirochaete Borrelia burgdorferi, can pose a challenge for practising neurologists. This Review is a summary of clinical presentation, diagnosis, and therapy, as well as of recent advances in our understanding of LNB. Many new insights have been gained through work in experimental models of the disease. An appreciation of the genetic heterogeneity of the causative pathogen has helped clinicians in their understanding of the diverse presentations of LNB.

Intrathecal antibody production in a mouse model of Lyme neuroborreliosis

Intrathecal antibody (ITAb) production is a common feature of neurological diseases, yet very little is known about its mechanisms. Because ITAb is prominent in human Lyme neuroborreliosis (LNB), in the present study we established a mouse model of LNB to study ITAb production. We injected different strains of Borrelia burgdorferi into a variety of mouse strains by the intracerebral (i.c.) route to develop the model. Spirochetal infection and ITAb production were identified by complementary methods. This study demonstrates that the mouse model of LNB can be utilized to test hypotheses related to the mechanisms of ITAb production.

Borrelia burgdorferi, host-derived proteases, and the blood-brain barrier

Neurological manifestations of Lyme disease in humans are attributed in part to penetration of the blood-brain barrier (BBB) and invasion of the central nervous system (CNS) by Borrelia burgdorferi. However, how the spirochetes cross the BBB remains an unresolved issue. We examined the traversal of B. burgdorferi across the human BBB and systemic endothelial cell barriers using in vitro model systems constructed of human brain microvascular endothelial cells (BMEC) and EA.hy 926, a human umbilical vein endothelial cell (HUVEC) line grown on Costar Transwell inserts. These studies showed that B. burgdorferi differentially crosses human BMEC and HUVEC and that the human BMEC form a barrier to traversal. During the transmigration by the spirochetes, it was found that the integrity of the endothelial cell monolayers was maintained, as assessed by transendothelial electrical resistance measurements at the end of the experimental period, and that B. burgdorferi appeared to bind human BMEC by their tips near or at cell borders, suggesting a paracellular route of transmigration. Importantly, traversal of B. burgdorferi across human BMEC induces the expression of plasminogen activators, plasminogen activator receptors, and matrix metalloproteinases. Thus, the fibrinolytic system linked by an activation cascade may lead to focal and transient degradation of tight junction proteins that allows B. burgdorferi to invade the CNS.

Genotype determines phenotype in experimental Lyme borreliosis

Borrelia burgdorferi sensu lato, the causative organism of Lyme borreliosis, is a heterogeneous group of spirochetes, consisting of at least three pathogenic species. To test the hypothesis that the genetic heterogeneity is the reason for the clinical differences, we investigated whether the experimental disease induced by European isolates is different from that induced by American isolates. Two American isolates of species B. burgdorferi sensu stricto were compared with three European isolates, two of species B. garinii, and one of species B. afzelii. The patterns of infection, immunity, and inflammation induced by the different species was distinctive. Inflammatory cells and levels of antibody in B. garinii- and B. afzelii-infected animals were lower than in B. burgdorferi s.s.-infected animals, whereas levels of spirochetal infection in the skin and nervous system were higher in the former group of animals. These data demonstrate that B. burgdorferi s.s. strains are more infective and inflammatory, whereas B. garinii and B. afzelii strains can survive the adaptive immune response to a greater degree and persist at greater numbers in the skin and nervous system. The results explain to a large extent the disparities between LNB in humans in the United States and Europe.

Humoral immune response associated with lyme borreliosis in nonhuman primates: analysis by immunoblotting and enzyme-linked immunosorbent assay with sonicates or recombinant proteins

The immune response to Borrelia burgdorferi, the causative agent of Lyme disease, is complex. We studied the immunoglobulin M (IgM) and IgG antibody response to N40Br, a sensu stricto strain, in the rhesus macaque(nonhuman primate [NHP]) model of infection to identify the spirochetal protein targets of specific antibody. Antigens used in enzyme-linked immunosorbent assays were whole-cell sonicates of the spirochete and recombinant proteins of B. burgdorferi. Immunoblotting with a commercially available strip and subsequent quantitative densitometry of the bands were also used. Sera from four different groups of NHPs were used: immunocompetent, transiently immunosuppressed, extended immunosuppressed, and uninfected. In immunocompetent and transiently immunosuppressed NHPs, there was a strong IgM and IgG response. Major proteins for the early IgM response were P39 and P41 and recombinant BmpA and OspC. Major proteins for the later IgG response were P39, P41, P18, P60, P66, and recombinant BmpA and DbpA. There was no significant response in the NHPs to recombinant OspA or to Arp, a 37-kDa protein that elicits an antibody response during infection in mice. Most antibody responses, except for that to DbpA, were markedly diminished by prolonged dexamethasone treatment. This study supports the hypothesis that recombinant proteins may provide a useful adjunct to current diagnostic testing for Lyme borreliosis.

Localization of Borrelia burgdorferi in the nervous system and other organs in a nonhuman primate model of lyme disease

Lyme borreliosis is caused by infection with the spirochete Borrelia burgdorferi. Nonhuman primates inoculated with the N40 strain of B. burgdorferi develop infection of multiple tissues, including the central (CNS) and peripheral nervous system. In immunocompetent nonhuman primates, spirochetes are present in low numbers in tissues. For this reason, it has been difficult to study their localization and changes in expression of surface proteins. To further investigate this, we inoculated four immunosuppressed adult Macaca mulatta with 1 million spirochetes of the N40 strain of B. burgdorferi, and compared them with three infected immunocompetent animals and two uninfected controls. The brain, spinal cord, peripheral nerves, skeletal muscle, heart, and bladder were obtained at necropsy 4 months later. The spirochetal tissue load was first studied by polymerase chain reaction (PCR)-ELISA of the outer surface protein A (ospA) gene. Immunohistochemistry was used to study the localization and numbers of spirochetes in tissues and the expression of spirochetal proteins and to characterize the inflammatory response. Hematoxylin and eosin and trichrome stains were used to study inflammation and tissue injury. The results showed that the number of spirochetes was significantly higher in immunosuppressed animals. B. burgdorferi in the CNS localized to the leptomeninges, nerve roots, and dorsal root ganglia, but not to the parenchyma. Outside of the CNS, B. burgdorferi localized to endoneurium and to connective tissues of peripheral nerves, skeletal muscle, heart, aorta, and bladder. Although ospA, ospB, ospC, and flagellin were present at the time of inoculation, only flagellin was expressed by spirochetes in tissues 4 months later. Significant inflammation occurred only in the heart, and only immunosuppressed animals had cardiac fiber degeneration and necrosis. Plasma cells were abundant in inflammatory foci of steroid-treated animals. We concluded that B. burgdorferi has a tropism for the meninges in the CNS and for connective tissues elsewhere in the body.

Spirochetal infection of the nervous system

Neurologic infection is a characteristic feature of spirochetes. The neurologic manifestations of spirochetal infection are a source of continuing public concern: Lyme neuroborreliosis in endemic areas, neurosyphilis in HIV infected patients, and neuroborreliosis during outbreaks of relapsing fever. These are reviewed in this article. The techniques for diagnosis and recommendations in the management of these infections are also discussed.

Detection of active infection in nonhuman primates with Lyme neuroborreliosis: comparison of PCR, culture, and a bioassay

Ideally a diagnosis of infection of the central nervous system (CNS) is made by culture of the etiologic pathogen, but Borrelia burgdorferi, the causative agent of Lyme neuroborreliosis (LNB), is rarely cultured from the cerebrospinal fluid (CSF). PCR and measurement of specific antibody in the CSF also have their limitations. The role of available assays for LNB has not been studied carefully in a comparative investigation. There is a need to assess the reliability of assays and to increase the ability to document active infection in the CNS. The recent development of the nonhuman primate (NHP) model of LNB allowed us to address this need in a faithful model of human LNB. In this study we compared the abilities of PCR and culture to detect the presence of spirochetes in the CSF and brain tissue of infected NHPs and related these measures of infection to the development of anti-B. burgdorferi antibody. We also tested a bioassay, the mouse infectivity test (MIT), in this model. Fourteen of 16 CSFs from four NHPs were positive by at least one of these techniques. Detection of spirochetes in the CSF by PCR, the MIT, and culture was inversely related to the concomitant presence of anti-B. burgdorferi antibody intrathecally. The performance of any particular test was associated with the strength of the host immune response. In early CNS infection, when anti-B. burgdorferi antibody had not yet appeared, or in immunocompromised hosts, the MIT compared favorably to culture and PCR for infected NHPs; antibody in the CSF was the most useful assay for immunocompetent NHPs.

Lyme disease in transgenic mice expressing the Borrelia burgdorferi flagellin epitope implicated in human neuroborreliosis

Because of an association of human neuroborreliosis with the development of an antibody response against an antigen in neural tissue that cross-reacts with an epitope on the flagellin protein of Borrelia burgdorferi, C3H transgenic mice were created that expressed the flagellin epitope (amino acids 213-224) as a fusion protein with myelin basic protein. The transgenic mice expressed the flagellin epitope selectively in myelinated regions of the nervous system. Both transgenic and non-transgenic mice developed an antibody response to the flagellin epitope during B. burgdorferi infection and both developed arthritis and carditis. However, no lesions were found in the central nervous system of either type of mouse for up to 8 weeks after infection. The data indicate that expression of the flagellin 213-24 epitope in mice does not result in neurologic disease, suggesting that B. burgdorferi flagellin antibodies may not be directly implicated in neuroborreliosis.

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.

Experimental immunization with Borrelia burgdorferi induces development of antibodies to gangliosides

Patients with neuroborreliosis produce antibodies, mostly of the immunoglobulin M (IgM) class, to gangliosides, particularly to those with Gal(beta 1-3)GalNac terminal sequences. Lewis rats were immunized with a nonpathogenic strain of Borrelia burgdorferi and with a chloroform-methanol extract (nonprotein) of this organism (CM) to determine whether antibodies to B. burgdorferi also recognized gangliosides. Rats were also immunized with asialo-GM1 to determine whether the elicited antibodies recognized antigens in B. burgdorferi. Rats immunized with B. burgdorferi produced low levels of IgM antibodies that cross-reacted with asialo-GM1 and GM1. Rats immunized with CM had marked IgM reactivity to asialo-GM1 and GM1. Immunization with asialo-GM1 resulted in antibodies that cross-reacted with B. burgdorferi antigens. Although antibodies to B. burgdorferi were of both the IgM and IgG classes, those to CM and to asialo-GM1 and GM1 were predominantly in the IgM fraction. Reactivity of the IgM antibodies decreased after adsorption with the heterologous and the homologous antigens, indicating bidirectional cross-reactivity between CM, asialo-GM1, and GM1 and that immunization with one produces antibodies to the other. There was no in vivo deposition of Ig in peripheral nerves, nor was there nerve pathology as a result of immunizations, but IgM antibodies to asialo-GM1 and CM recognized homologous antigens in the nodes of Ranvier of peripheral nerves from nonimmunized rats. This immunization model suggests that antibodies to gangliosides in Lyme disease have a microbial origin and are potentially relevant in pathogenesis.

Neuroborreliosis in the nonhuman primate: Borrelia burgdorferi persists in the central nervous system

Neurological involvement in Lyme disease is common, and is frequently difficult to diagnose and treat. Little is known about the fate of the causative spirochete Borrelia burgdorferi in the central nervous system (CNS). To determine the frequency of parenchymal infection and to determine localization of the organism, polymerase chain reaction/hybridization assays were performed in a newly described model of Lyme neuroborreliosis in nonhuman primates infected with B. burgdorferi. Polymerase chain reaction/hybridization of CNS tissues from 5 infected nonhuman primates was performed. Substantial amounts of B. burgdorferi DNA were detected in the CNS in all infected animals, with a predilection toward subtentorial structures. These data suggest that Lyme neuroborreliosis represents persistent infection with B. burgdorferi.

Lyme neuroborreliosis

Neuroborreliosis, an infection of the nervous system caused by spirochetes of the genus Borrelia, has achieved worldwide attention in the last decade as part of the clinical spectrum of Lyme disease. This disorder, caused by Borrelia burgdorferi, has increased in incidence to become the most frequent arthropod-borne infection in North America and Europe. As a result of this rapid rise in incidence and of its protean neurological manifestations, this disease has created an important challenge to modern neurology. The diverse manifestations of neuroborreliosis require that it be included in the differential diagnosis of many neurological disorders. This review takes a chronological approach to clinical neuroborreliosis to summarize its most important aspects. The limitations as well as the benefits of laboratory diagnosis are also considered, with the aim of providing assistance in this area. Recent advances in neuroimmunology regarding the pathogenesis of neuroborreliosis that may elucidate its protean clinical spectrum are summarized.

Early disseminated Lyme disease: Lyme meningitis

Lyme meningitis is the direct result of invasion of the nervous system by Borrelia burgdorferi. Occurring within the first few months of infection, it initially presents as a chronic basilar meningitis. Much about the pathogenesis of Lyme meningitis has been learned from animal models, the best being the adult Rhesus macaque. Injection of these animals with a highly infective strain of B. burgdorferi has led to a very predictable course of events: erythema migrans within the first few weeks after injection, development of anti-B. burgdorferi antibody, detection of spirochetemia in weeks 3 and 4, and central nervous system (CNS) invasion within 1 month with cerebrospinal fluid (CSF) pleocytosis. In humans, facial palsy is the earliest clinical indicator. Headache and meningismus are symptoms of inflammation of the subarachnoid space. Severe fatigue and arthralgia are common extra-CNS symptoms. Culture is not generally useful for detecting or confirming Lyme meningitis. False-positive serologic tests may occur in patients with other infections, inflammatory processes, or malignancies. Immunoblotting will differentiate true-from false-positive antibody reactivity. Lack of a consistently positive serum antibody titer should make the diagnosis of Lyme meningitis suspect. Positive CSF antibody is almost universal in patients with Lyme meningitis. Polymerase chain reaction is a direct test that is highly specific and sensitive. The antibiotic treatment of choice is intravenous (i.v.) cephalosporins or penicillin for 2-3 weeks. If the clinical picture is anything less than absolutely classic, a lumbar puncture and Western blot of serum should be obtained in a seropositive patient before initiating intravenous antibiotic therapy. There is no role at this time for long-term (> 1 month) intravenous antibiotics. Nonsteroidal antiinflammatory agents can also be of benefit.

Inoculation of nonhuman primates with the N40 strain of Borrelia burgdorferi leads to a model of Lyme neuroborreliosis faithful to the human disease

We injected rhesus macaques with a highly infective strain of Borrelia burgdorferi to assess whether experimentally inoculated nonhuman primates (NHPs) could serve as models of human Lyme neuroborreliosis (LNB). The animals developed biopsy-confirmed erythema migrans in the area of the inoculations. ELISA testing of sera revealed strong antibody reactivity to B burgdorferi antigens, and Western blotting showed that 16-, 22-, 31-, 34-, and 41-kd proteins of the spirochete were major antigens recognized by antibody. Culture and polymerase chain reaction (PCR) testing of serial CSF specimens revealed that chronic infection of the CNS occurred in all NHPs injected. CSF pleocytosis occurred concurrently with CNS infection. Brain MRI revealed intense meningeal inflammation in one NHP as manifested by gadolinium uptake by the dura at the base of the temporal lobes. All animals had measurable antibody in the CSF after invasion. These studies are the first to demonstrate that experimental LNB in NHPs is a reliable model faithful to the human disease, with spirochetal invasion of the subarachnoid space. This also is the first report of CSF samples positive by culture in experimental LNB. Inflammation in the CNS as manifested by CSF pleocytosis and MRI findings was also correlated with the presence of spirochetal DNA detected by PCR. These data support the hypothesis that the pathogenesis of LNB is associated with direct spirochetal invasion, and provide evidence that CNS involvement is more common than heretofore thought.

Effectiveness of antimicrobial treatment against Borrelia burgdorferi infection in mice

Although antimicrobial agents are effective therapy for early Lyme disease, optimal treatment schedules have not been conclusively established. The efficacy of various dosages of eight antibiotics used for borreliosis treatment was evaluated for C3H/HeNCrIBR mice, which reproducibly develop persistent infection, arthritis, and carditis when inoculated with Borrelia burgdorferi. Amoxicillin-clavulanic acid, ceftriaxone, and high-dose penicillin G effectively eliminated infection and disease. Oxytetracycline, doxycycline, chloramphenicol, erythromycin, and azithromycin failed to cure infected mice. There was a correlation between peak serum antibiotic concentrations in mice, as determined by agar well diffusion bioassays, and therapeutic levels in humans. When experimentally inoculated mice were treated at 1 week postinfection with ceftriaxone (16 mg/kg of body weight twice daily for 5 days) and monitored for up to 90 days, all treated mice were free of spirochetes and had no gross or histologic lesions. This antibiotic regimen at days 7 to 11 postinoculation eliminated the spirochetes so that there were no relapses during the 90-day observation period. For experimentally inoculated mice treated with ceftriaxone at 7 or 14 days postinfection, arthritis, carditis, and infection were eliminated. When treatment began at 30 and 90 days after inoculation, infection and active cardiac and arthritic lesions were eradicated; however, residual mild synovitis and vasculitis persisted in some mice. In comparison with inoculated, untreated mice, ceftriaxone therapy at 7, 14, 30, and 90 days postinfection abrogated the development of antibody titers against B. burgdorferi. Having the potential to determine the presence of the spirochete through culture and histologic lesions makes the B. burgdorferi-inoculated C3H mouse model a valuable adjunct in evaluating chemotherapeutic options for Lyme disease.

Variability of a bacterial surface protein and disease expression in a possible mouse model of systemic Lyme borreliosis

During persistent infection of scid mice with Borrelia turicatae, an agent of relapsing fever and neuroborreliosis, there was variation in the surface proteins the bacteria expressed and in disease manifestations over time. Two serotypes, A and B, were isolated from the mice, cloned by limiting dilution, and further characterized. The only discernible difference between the two variants was in the size of the major surface protein they expressed: serotype A had a variable major protein (Vmp) of 23,000, and serotype B had a Vmp of 20,000. When other scid mice were inoculated with clonal populations of A and B, the infections were similar with respect to onset and degree of spirochetemia, involvement of the eye and heart, and occurrence of a peripheral vestibular disorder. However, there were differences between the serotypes in other respects: (a) serotype B but not A caused reddened and significantly enlarged joints, markedly impaired performance on a walking bar, and severe arthritis by histologic examination; (b) serotype A but not B invaded the central nervous system during early infection; and (c) serotype A penetrated monolayers of human umbilical vein endothelial cells more readily than did serotype B. The combination of arthritis, myocarditis, and neurologic disease resembled human Lyme borreliosis. The findings indicate that differences in disease expression are determined by variable surface proteins of the bacterium and that scid mouse infections with B. turicatae provide a model for the study of the pathogenesis of Lyme borreliosis and other persistent spirochetal diseases.

The polymerase chain reaction in the diagnosis of Lyme neuroborreliosis

The polymerase chain reaction is sensitive and specific in the detection of defined DNA sequences and holds promise for diagnosing the presence of fastidious microorganisms in human infectious diseases. We developed a methodology for nested polymerase chain reaction and hybridization analysis of the cerebrospinal fluid using primers from a genomic Borrelia burgdorferi sequence and applied it to the cerebrospinal fluid (CSF) of patients suspected of having Lyme neuroborreliosis and other diseases. Polymerase chain reaction and hybridization demonstrated extremely high sensitivity for spirochetal DNA, and was highly specific, with a false-positivity rate of less than 3%. However, the results were negative or indeterminate in 54% of CSF samples from patients with definite or probable disease, indicating an absence, or extremely low level, of spirochetes or spirochetal DNA in a significant percentage of patients with Lyme neuroborreliosis. Polymerase chain reaction and hybridization of the CSF can thus be considered a useful adjunct in diagnosis, but its negativity does not rule out Lyme neuroborreliosis.

Comparison of polymerase chain reaction with culture and serology for diagnosis of murine experimental Lyme borreliosis

After the intradermal inoculation of mice with Borrelia burgdorferi, the antibody response, culture, and histology of blood and target organs were assessed and compared with results of a nested polymerase chain reaction (PCR) assay. Of 247 specimens of heart, brain, bladder, and blood, the tested concordance between the PCR and culture was 72%. In the 69 instances of discordance, the PCR was positive in 51 and the culture was positive in 18; thus, the PCR was concordant or more sensitive in 93% of the tested organs. In mice infected with 10 spirochetes, serology confirmed by Western blotting (immunoblotting) was more sensitive than either culture or PCR of brain, bladder, or heart specimens. The organs most commonly culture or PCR positive were the heart and bladder; the brain was infected in only 26% of the animals. DNA hybridization was helpful in confirming the PCR product as being specific and, in some cases, in demonstrating a positive product in the face of negative agarose gels. PCR was less sensitive than culture in detecting the presence of spirochetes in blood specimens, possibly because of the presence of blood inhibitors. We thus found a nested PCR assay, using primers from a genomic sequence, to be a valuable adjunct to serology and culture in the study of murine Lyme borreliosis. The assay confirmed that, after small numbers of spirochetes are injected intradermally, the heart and bladder, and less frequently the brain, are sites of persistence of the spirochetes.

Serologic response to the Borrelia burgdorferi flagellin demonstrates an epitope common to a neuroblastoma cell line

Antibodies in sera of 7 patients with neurologic manifestations of Lyme borreliosis and a monoclonal antibody (mAb H9724) to the flagellin of Borrelia burgdorferi have been shown to bind neural tissue. To identify the antibody binding site common to the B. burgdorferi flagellin and the neural tissue, we made recombinant fusion proteins expressing epitopes of flagellin. Antibodies in patients' sera and mAb H9724 bound within an 18-amino acid epitope (residues 208-225) in the central region of flagellin, whereas two other mAbs bound to epitopes mapping elsewhere in the protein. Antibodies in patients sera and mAb H9724 also bound to a human neuroblastoma cell line. Absorption of patients sera with a peptide, EGVQQEGAQQPA, corresponding to amino acids 213-224 of flagellin, inhibited binding to the neuroblastoma cell line. The data suggest that the immune response to a specific B-cell epitope within flagellin, shared by a human neuroblastoma cell line, may be involved in the pathogenesis of neuroborreliosis.