Analysis of the Borrelia burgdorferi GeHo fla gene and antigenic characterization of its gene product

Screening and identification of immunoactive FlaB protein fragments of Treponema pallidum for the serodiagnosis of syphilis

Flagellin is a classical pathogen-associated molecular pattern that can evoke a robust immune response. We have demonstrated previously that three full-length flagellins of Treponema pallidum, namely FlaB1, FlaB2 and FlaB3, did have diagnostic value in the serodiagnosis of syphilis. Here, we selected and constructed three recombinant fragments of each complete FlaB, both the conserved N-terminal and the C-terminal region, and the middle variable part, with the goal of exploring fragments unique to Treponema pallidum for use as antigen targets in a fragment-based serological test. The diagnostic performance of fragments was evaluated using different panels of serum specimens (= 332) by indirect IgG enzyme-linked immunosorbent assay. The data showed that all the conserved fragments exhibited excellent sensitivities (91.1-95.0%) but poor specificities (64.1-78.4%), while the three middle regions demonstrated higher sensitivities and specificities for detecting IgG antibody, with 92.7% and 96.1% for FlaB1M ('B1M'), 91.6% and 94.8% for B2M, and 95.0% and 100% for B3M, respectively. In comparison, the sensitivity and specificity of Architect Syphilis TP was found to be 95.5% and 94.8%, respectively. These findings revealed that the middle portion of each FlaB had epitopes specific for Treponema pallidum and identified B3M as a promising candidate antigen for the serodiagnosis of syphilis.

Sequence- and Structure-Based Immunoreactive Epitope Discovery for Burkholderia pseudomallei Flagellin

Burkholderia pseudomallei is a Gram-negative bacterium responsible for melioidosis, a serious and often fatal infectious disease that is poorly controlled by existing treatments. Due to its inherent resistance to the major antibiotic classes and its facultative intracellular pathogenicity, an effective vaccine would be extremely desirable, along with appropriate prevention and therapeutic management. One of the main subunit vaccine candidates is flagellin of Burkholderia pseudomallei (FliC_Bp). Here, we present the high resolution crystal structure of FliC_Bp and report the synthesis and characterization of three peptides predicted to be both B and T cell FliC_Bp epitopes, by both structure-based in silico methods, and sequence-based epitope prediction tools. All three epitopes were shown to be immunoreactive against human IgG antibodies and to elicit cytokine production from human peripheral blood mononuclear cells. Furthermore, two of the peptides (F51-69 and F270-288) were found to be dominant immunoreactive epitopes, and their antibodies enhanced the bactericidal activities of purified human neutrophils. The epitopes derived from this study may represent potential melioidosis vaccine components.

Melioidosis is an infectious disease caused by Burkolderia pseudomallei that poses a major public health problem in Southeast Asia and northern Australia. This bacterium is difficult to treat due to its intrinsic resistance to antibiotics, poor diagnosis, and the lack of a licensed vaccine. Vaccine safety is a prime concern, therefore recombinant protein subunit and/or peptide vaccine components, may represent safer alternatives. In this context, we targeted one of the main subunit vaccine candidates tested to date, flagellin from B. pseudomallei (FliC_Bp) that comprises the flagellar filament that mediates bacterial motility. Based on the knowledge that activation of both cell-mediated and antibody-mediated responses must be addressed in a melioidosis vaccine, we identified B and T cell immunoreactive peptides from FliC_Bp, using both sequence-based and structure-based computational prediction programs, for further in vitro immunological testing. Our data confirm the accuracy of sequence-based epitope prediction tools, and two structure-based methods applied to the FliC_Bp crystal structure (here-described), in predicting both T- and B-cell epitopes. Moreover, we identified two epitope peptides with significant joint T-cell and B-cell activities for further development as melioidosis vaccine components.

Motility is crucial for the infectious life cycle of Borrelia burgdorferi

The Lyme disease spirochete, Borrelia burgdorferi, exists in a zoonotic cycle involving an arthropod tick and mammalian host. Dissemination of the organism within and between these hosts depends upon the spirochete's ability to traverse through complex tissues. Additionally, the spirochete outruns the host immune cells while migrating through the dermis, suggesting the importance of B. burgdorferi motility in evading host clearance. B. burgdorferi's periplasmic flagellar filaments are composed primarily of a major protein, FlaB, and minor protein, FlaA. By constructing a flaB mutant that is nonmotile, we investigated for the first time the absolute requirement for motility in the mouse-tick life cycle of B. burgdorferi. We found that whereas wild-type cells are motile and have a flat-wave morphology, mutant cells were nonmotile and rod shaped. These mutants were unable to establish infection in C3H/HeN mice via either needle injection or tick bite. In addition, these mutants had decreased viability in fed ticks. Our studies provide substantial evidence that the periplasmic flagella, and consequently motility, are critical not only for optimal survival in ticks but also for infection of the mammalian host by the arthropod tick vector.

The Borrelia burgdorferi flaB promoter has an extended -10 element and includes a T-rich -35/-10 spacer sequence that is essential for optimal activity

In this study, we investigated the functional elements of the flaB promoter of Borrelia burgdorferi. Promoter function was examined in a high-passage variant of strain JD1 using a set of 5' deletions and mutations within the flaB promoter. Expression from the modified flaB promoters was assayed using the gene for green fluorescent protein (gfp) as a reporter. Although the -35 element of the promoter stimulated promoter activity, its disruption did not negate expression. Sequences upstream of the -35 had no effect on expression. The -35/-10 spacer region composed of a T-rich sequence was critical for optimal promoter function. Surprisingly, a cytosine at the -13 site was found to be more favorable for transcription compared with a guanosine at the same site. Based on these results and other characteristics, we propose that the B. burgdorferi flaB promoter is an example of an extended -10 promoter. Further, the T-rich spacer is a key element of the flaB promoter that contributes to the abundance of the flagellar core protein in Borrelia species.

Evaluation of the recombinant VlsE-based liaison chemiluminescence immunoassay for detection of Borrelia burgdorferi and diagnosis of Lyme disease

Recent efforts to improve the serologic diagnosis of Lyme disease have included the use of a synthetic peptide (C6) that reproduces the sequence of invariable region 6 of VlsE, the variable surface antigen of Borrelia burgdorferi. In the present study, the diagnostic performance of DiaSorin's recombinant VlsE-based chemiluminescence immunoassay in 1,947 human serum samples was evaluated. Sensitivity was determined using two serum panels from the CDC. For panel I, we observed sensitivities of 68.4% and 75.6% for subjects with early, localized (n=19) or disseminated (n=41) disease, respectively. For panel II, we observed sensitivities of 61.5% and 100% for subjects with early (n=26) or late-stage (n=11) disease, respectively. We observed a specificity of 99.5% for healthy donors (n=600) living either in regions of the United States where the disease is endemic or in regions where it is not endemic. Overall, specificity among 207 potentially cross-reactive sera from subjects who had other spirochetal infections, nonspirochetal infections including bacterial and viral infections, or autoimmune or neurologic disease; who were positive for rheumatoid factor or anti-mouse antibodies; or who had been previously vaccinated for Lyme disease was 93.7%. In a direct comparison of 1,038 prospectively collected samples for Lyme disease testing we observed a relative sensitivity of 70%, a relative specificity of 99.1%, and an overall agreement of 97.1% between the DiaSorin recombinant VlsE chemiluminescence immunoassay and the Immunetics peptide-based C6 enzyme-linked immunosorbent assay.

Diagnosis of lyme borreliosis

A large amount of knowledge has been acquired since the original descriptions of Lyme borreliosis (LB) and of its causative agent, Borrelia burgdorferi sensu stricto. The complexity of the organism and the variations in the clinical manifestations of LB caused by the different B. burgdorferi sensu lato species were not then anticipated. Considerable improvement has been achieved in detection of B. burgdorferi sensu lato by culture, particularly of blood specimens during early stages of disease. Culturing plasma and increasing the volume of material cultured have accomplished this. Further improvements might be obtained if molecular methods are used for detection of growth in culture and if culture methods are automated. Unfortunately, culture is insensitive in extracutaneous manifestations of LB. PCR and culture have high sensitivity on skin samples of patients with EM whose diagnosis is based mostly on clinical recognition of the lesion. PCR on material obtained from extracutaneous sites is in general of low sensitivity, with the exception of synovial fluid. PCR on synovial fluid has shown a sensitivity of up to >90% (when using four different primer sets) in patients with untreated or partially treated Lyme arthritis, making it a helpful confirmatory test in these patients. Currently, the best use of PCR is for confirmation of the clinical diagnosis of suspected Lyme arthritis in patients who are IgG immunoblot positive. PCR should not be used as the sole laboratory modality to support a clinical diagnosis of extracutaneous LB. PCR positivity in seronegative patients suspected of having late manifestations of LB most likely represents a false-positive result. Because of difficulties in direct methods of detection, laboratory tests currently in use are mainly those detecting antibodies to B. burgdorferi sensu lato. Tests used to detect antibodies to B. burgdorferi sensu lato have evolved from the initial formats as more knowledge on the immunodominant antigens has been collected. The recommendation for two-tier testing was an attempt to standardize testing and improve specificity in the United States. First-tier assays using whole-cell sonicates of B. burgdorferi sensu lato need to be standardized in terms of antigen composition and detection threshold of specific immunoglobulin classes. The search for improved serologic tests has stimulated the development of recombinant protein antigens and the synthesis of specific peptides from immunodominant antigens. The use of these materials alone or in combination as the source of antigen in a single-tier immunoassay may someday replace the currently recommended two-tier testing strategy. Evaluation of these assays is currently being done, and there is evidence that certain of these antigens may be broadly cross-reactive with the B. burgdorferi sensu lato species causing LB in Europe.

The decrease in FlaA observed in a flaB mutant of Borrelia burgdorferi occurs posttranscriptionally

The Lyme disease bacterium Borrelia burgdorferi is a motile spirochete with a flat-wave morphology. The periplasmic flagella, which are situated between the outer membrane sheath and cell cylinder, are essential for both the cell's wavy shape and motility. Here we focus on the structure and regulation of its periplasmic flagella. Previous studies have suggested that the periplasmic flagella consist of a polymer of the major filament protein FlaB and a minor protein, FlaA. We used immunoprecipitation methodology to present further evidence that FlaA is indeed a flagellar protein. In addition, in contrast to FlaA of the spirochete Brachyspira hyodysenteriae, B. burgdorferi FlaA did not impact the overall helical shape of the periplasmic flagella. We have previously shown that B. burgdorferi lacks the sigma factor-dependent cascade control of motility gene transcription found in other bacteria. To begin to understand motility gene regulation in B. burgdorferi, we examined the effects of an insertion mutation in flaB on the amounts of proteins encoded by motility genes. Of several motility gene-encoded proteins examined, only the amount of FlaA was decreased in the flaB mutant; it was 13% compared to the wild-type amount. Real-time reverse transcriptase PCR analysis indicated that this inhibition was not the result of a decrease in flaA mRNA. In addition, protein stability analysis suggested that FlaA was turned over in the flaB mutant. Our results indicate that the lack of FlaB negatively influences the amount of FlaA found in the cell and that this effect is at the level of either translational control or protein turnover.

Borrelia burgdorferi periplasmic flagella have both skeletal and motility functions

Bacterial shape usually is dictated by the peptidoglycan layer of the cell wall. In this paper, we show that the morphology of the Lyme disease spirochete Borrelia burgdorferi is the result of a complex interaction between the cell cylinder and the internal periplasmic flagella. B. burgdorferi has a bundle of 7-11 helically shaped periplasmic flagella attached at each end of the cell cylinder and has a flat-wave cell morphology. Backward moving, propagating waves enable these bacteria to swim in both low viscosity media and highly viscous gel-like media. Using targeted mutagenesis, we inactivated the gene encoding the major periplasmic flagellar filament protein FlaB. The resulting flaB mutants not only were nonmotile, but were rod-shaped. Western blot analysis indicated that FlaB was no longer synthesized, and electron microscopy revealed that the mutants were completely deficient in periplasmic flagella. Wild-type cells poisoned with the protonophore carbonyl cyanide-m-chlorophenylhydrazone retained their flat-wave morphology, indicating that the periplasmic flagella do not need to be energized for the cell to maintain this shape. Our results indicate that the periplasmic flagella of B. burgdorferi have a skeletal function. These organelles dynamically interact with the rod-shaped cell cylinder to enable the cell to swim, and to confer in part its flat-wave morphology.

Rapid differentiation of Borrelia garinii from Borrelia afzelii and Borrelia burgdorferi sensu stricto by LightCycler fluorescence melting curve analysis of a PCR product of the recA gene

To differentiate the Borrelia burgdorferi sensu lato genospecies, LightCycler real-time PCR was used for the fluorescence (SYBR Green I) melting curve analysis of borrelial recA gene PCR products. The specific melting temperature analyzed is a function of the GC/AT ratio, length, and nucleotide sequence of the amplified product. A total of 32 DNA samples were tested. Of them three were isolated from B. burgdorferi reference strains and 16 were isolated from B. burgdorferi strains cultured from Ixodes ricinus ticks; 13 were directly isolated from nine human biopsy specimens and four I. ricinus tick midguts. The melting temperature of B. garinii was 2 degrees C lower than that of B. burgdorferi sensu stricto and B. afzelii. Melting curve analysis offers a rapid alternative for identification and detection of B. burgdorferi sensu lato genospecies.

Recombinant chimeric Borrelia proteins for diagnosis of Lyme disease

Current serologic Lyme disease tests use whole borrelia cells as the source of antigen. These assays are difficult to standardize and to optimize for sensitivity and specificity. To help solve these problems, we constructed a library of recombinant chimeric proteins composed of portions of key antigens of Borrelia burgdorferi. These proteins were then used to develop an enzyme-linked immunosorbent assay. We compared our assay with the most sensitive of three whole-cell borrelia assays. We found that the recombinant assay could detect antibodies significantly better from early Lyme disease sera (P<0.05), and had the same sensitivity for late Lyme disease sera, as the most sensitive whole-cell borrelia assay. On potentially cross-reactive sera, the recombinant assay was more specific, but not significantly so, than the best whole-cell borrelia assay. Optimization of the recombinant assay offers the potential for a significant improvement in both sensitivity and specificity.

Molecular typing of Borrelia burgdorferi sensu lato: taxonomic, epidemiological, and clinical implications

Borrelia burgdorferi sensu lato, the spirochete that causes human Lyme borreliosis (LB), is a genetically and phenotypically divergent species. In the past several years, various molecular approaches have been developed and used to determine the phenotypic and genetic heterogeneity within the LB-related spirochetes and their potential association with distinct clinical syndromes. These methods include serotyping, multilocus enzyme electrophoresis, DNA-DNA reassociation analysis, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis, plasmid fingerprinting, randomly amplified polymorphic DNA fingerprinting analysis, species-specific PCR and PCR-based restriction fragment length polymorphism (RFLP) analysis, and sequence analysis of 16S rRNA and other conserved genes. On the basis of DNA-DNA reassociation analysis, 10 different Borrelia species have been described within the B. burgdorferi sensu lato complex: B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii, Borrelia japonica, Borrelia andersonii, Borrelia valaisiana, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, and Borrelia bissettii sp. nov. To date, only B. burgdorferi sensu stricto, B. garinii, and B. afzelii are well known to be responsible for causing human disease. Different Borrelia species have been associated with distinct clinical manifestations of LB. In addition, Borrelia species are differentially distributed worldwide and may be maintained through different transmission cycles in nature. In this paper, the molecular methods used for typing of B. burgdorferi sensu lato are reviewed. The current taxonomic status of B. burgdorferi sensu lato and its epidemiological and clinical implications, especiallly correlation between the variable clinical presentations and the infecting Borrelia species, are discussed in detail.

Low risk of Lyme borreliosis in a protected area on the Tyrrhenian coast, in central Italy

A comprehensive Lyme borreliosis risk assessment process was applied in S. Rossore Estate, on the Tyrrhenian coast, near Pisa, Italy. Host-seeking Ixodes ricinus nymphs peaked in May in oak-dominated deciduous wood (median, Q1-Q3, number of nymphs/50 m dragging = 4.5, 2.5-8), whereas host-seeking larvae peaked in August in the same habitat type (6.0, 4-17/50 m dragging). Prevalence of I. ricinus infestation was 88.9% in wild rodents (n = 11), 64.3% in fallow deer (n = 28) and 0.0% in wild boars (n = 5). Borrelia burgdorferi sensu lato was not isolated from rodents' organs, and from 80 I. ricinus nymphs and 50 adults. Moreover, PCR for B. burgdorferi sl carried out on 110 nymphs and 12 adult ticks also gave negative results. Forest workers were at higher risk of tick bite than other Estate employees (relative risk (RR): 1.7, p = 0.02). In spite of high levels of tick exposure, B. burgdorferi sl specific antibodies were not detected in sera from Estate personnel (n = 30) and sentinel animals (dogs, n = 23, fallow deer, n = 61).

Peptide-based OspC enzyme-linked immunosorbent assay for serodiagnosis of Lyme borreliosis

Sera from 210 patients with Lyme borreliosis (LB) were studied by an enzyme-linked immunosorbent assay (ELISA) based on a synthetic peptide (pepC10) comprising the C-terminal 10-amino-acid residues of OspC of Borrelia burgdorferi. We found that 36.3 and 45.0% of the serum samples from patients with erythema migrans (EM) and neuroborreliosis (NB), respectively, displayed immunoglobulin M (IgM) anti-pepC10 reactivities, while these samples rarely (</=8%) displayed IgG antibody reactivities. Sera from patients with acrodermatitis chronica atrophicans did not contain anti-pepC10 antibodies. The diagnostic performance of this newly developed peptide ELISA was compared with those of an ELISA based on the full-length recombinant OspC protein (rOspC) and a commercially available ELISA based on the B. burgdorferi flagellum (Fla). The sensitivity of the IgM pepC10 ELISA was slightly lower (P < 0.04) than that of the rOspC ELISA for EM patients (36.3 versus 43.8%), while there was no difference for NB patients (45.0 versus 48.0%). However, the optical density values obtained by the pepC10 ELISA were generally higher than those obtained by the rOspC ELISA, leading to a significantly better quantitative discrimination between seropositive patients with NB and controls (P < 0.008). The specificity of the pepC10 ELISA was similar to those of the rOspC ELISA and the Fla ELISA for relevant controls including patients with syphilis and mononucleosis. Although the overall diagnostic sensitivity of the Fla ELISA was superior, 8.8 and 12.0% of the EM and NB patients, respectively, were antibody positive only by the pepC10 ELISA. Thus, use of a diagnostic test for LB based on the detection of IgM antibodies to pepC10 and Fla has increased sensitivity for the diagnosis of early LB.

Diagnostic value of proteins of three Borrelia species (Borrelia burgdorferi sensu lato) and implications for development and use of recombinant antigens for serodiagnosis of Lyme borreliosis in Europe

More and more assays for the serodiagnosis of Lyme borreliosis (LB) are based on recombinant antigens. However, so far, there is no consensus as to which are the most specific and sensitive proteins and how they should be used in combination to obtain tests with the best discrimination abilities. The present study was preceded by a detailed analysis of Western blots (WB) using whole-cell lysates of Borrelia burgdorferi sensu stricto strain PKa2, B. afzelii PKo, and B. garinii PBi (U. Hauser, G. Lehnert, R. Lobentanzer, and B. Wilske, J. Clin. Microbiol. 35:1433-1444, 1997). For the present work, the data bank from that study, containing information about the reactivities of 330 sera (from patients at different stages of LB [n = 189]; control group, n = 141), was reused. The specificities and sensitivities of various combinations of proteins from different strains were calculated for different interpretation criteria. For immunoglobulin G (IgG) WB, the recommended combination of antigens available to date as recombinant proteins included p83/100 of PKa2, p83/100 of PKo, p39 of PKo, p39 of PBi, and OspC of PBi (interpretation criterion, at least one reactive band required for a positive WB; specificity, 96.5%; sensitivity, 56.1%). The further addition of p58 of PKo, p17 of PKo, or p14 of PKo was most favorable in terms of both a considerable gain of sensitivity and little loss of specificity. IgG Western blotting with a whole-cell lysate of strain PKo might be improved by the addition of OspC of PBi. For IgG WB, the best combination, out of all bands, was p83/100, p58, p39, p30, and p21 of all three strains and OspC of PBi, p17b of PBi, p56 of PKa2, p43 of PKo, p17 of PKo, and p14 of PKo (interpretation criterion, at least two reactive bands required for a positive WB; specificity, 97.2%; sensitivity, 61.4%). An interpretation criterion of at least two reactive bands is more reliable than one of only one reactive band. For IgM WB, the best combination was OspC of PKo, OspC of PBi, p39 of all three strains, p17 of PKo, and strong reactions with p41 of all three strains (interpretation criterion, at least one reactive band required; specificity, 97.9%; sensitivity, 47.0%).

Structure and expression of the FlaA periplasmic flagellar protein of Borrelia burgdorferi

The spirochete which causes Lyme disease, Borrelia burgdorferi, has many features common to other spirochete species. Outermost is a membrane sheath, and within this sheath are the cell cylinder and periplasmic flagella (PFs). The PFs are subterminally attached to the cell cylinder and overlap in the center of the cell. Most descriptions of the B. burgdorferi flagellar filaments indicate that these organelles consist of only one flagellin protein (FlaB). In contrast, the PFs from other spirochete species are comprised of an outer layer of FlaA and a core of FlaB. We recently found that a flaA homolog was expressed in B. burgdorferi and that it mapped in a fla/che operon. These results led us to analyze the PFs and FlaA of B. burgdorferi in detail. Using Triton X-100 to remove the outer membrane and isolate the PFs, we found that the 38.0-kDa FlaA protein purified with the PFs in association with the 41.0-kDa FlaB protein. On the other hand, purifying the PFs by using Sarkosyl resulted in no FlaA in the isolated PFs. Sarkosyl has been used by others to purify B. burgdorferi PFs, and our results explain in part their failure to find FlaA. Unlike other spirochetes, B. burgdorferi FlaA was expressed at a lower level than FlaB. In characterizing FlaA, we found that it was posttranslationally modified by glycosylation, and thus it resembles its counterpart from Serpulina hyodysenteriae. We also tested if FlaA was synthesized in a spontaneously occurring PF mutant of B. burgdorferi (HB19Fla-). Although this mutant still synthesized flaA message in amounts similar to the wild-type amounts, it failed to synthesize FlaA protein. These results suggest that, in agreement with data found for FlaB and other spirochete flagellar proteins, FlaA is likely to be regulated on the translational level. Western blot analysis using Treponema pallidum anti-FlaA serum indicated that FlaA was antigenically well conserved in several spirochete species. Taken together, the results indicate that both FlaA and FlaB comprise the PFs of B. burgdorferi and that they are regulated differently from flagellin proteins of other bacteria.

Clearance of Borrelia burgdorferi may not be required for resistance to experimental lyme arthritis

Infection of inbred mouse strains with Borrelia burgdorferi results in the development of experimental Lyme arthritis. The degree of arthritic pathology has been suggested to correlate with the level of spirochete burden within tissues. To investigate this further, we infected resistant DBA/2 (DBA) and susceptible C3H/HeJ (C3H) mice in the hind footpads and monitored arthritis development for 21 days. To quantitate levels of spirochetes within tissues, we created a competitive PCR molecule containing modified ospA and fla gene segments. C3H mice developed severe arthritis of the tibiotarsal joints, while DBA mice developed only mild inflammation throughout the experimental period. At day 21, when the gross size and histologic composition of ankles revealed significant differences in arthritis between the strains, there was little difference in levels of spirochete DNA as determined by competitive PCR. Cultures of ankle tissue at day 21 were also uniformly positive in both C3H and DBA animals and contained relatively similar levels of spirochetes. These results indicate that the presence of spirochetes in the ankles of experimental animals is not sufficient for arthritis development. Since arthritic and nonarthritic animals can harbor relatively equal spirochete burdens yet retain their distinct phenotypic outcomes, an aberrant or overly exuberant immune response may be an additional requirement for pathology in arthritis-prone mice.

Enzyme-linked immunosorbent assay using recombinant OspC and the internal 14-kDa flagellin fragment for serodiagnosis of early Lyme disease

The outer surface protein C (OspC) and the internal 14-kDa flagellin fragment of strain GeHo of Borrelia burgdorferi sensu stricto were expressed as recombinant proteins in Escherichia coli and were purified for use in an immunoglobulin M (IgM) enzyme-linked immunosorbent assay (OspC-14-kDa antigen ELISA). No hint at disturbing protein-protein interferences, which might influence the availability of immunoreactive epitopes, was found when the recombinant antigens were combined in the ELISA. The recombinant OspC-14-kDa antigen ELISA was compared to a commercial IgM ELISA that used a detergent cell extract from Borrelia afzelii PKo as the antigen. According to the manufacturer's information, the cell extract contains, in addition to other antigens, the following diagnostically relevant antigens: the 100-kDa (synonyms, 93- and 83-kDa antigens), 41-kDa, OspA, OspC, and 17-kDa antigens. The specificity was adjusted to 95% on the basis of data for 154 healthy controls. On testing of 104 serum samples from patients with erythema migrans (EM), the sensitivity of the recombinant ELISA (46%) for IgM antibodies was similar to that of the commercial ELISA (45%). However, when 42 serum samples from patients with polyclonal B-cell stimulation due to an Epstein-Barr virus infection were tested, false-positive reactions were significantly less frequent in the recombinant ELISA (10%) than in the whole-cell-extract ELISA (23%). OspC displays sequence heterogeneity of up to 40% according to the genomospecies. However, when the reactions of serum specimens from controls and EM patients with OspC from representative strains of B. burgdorferi sensu stricto (strain GeHo) and B. afzelii (strain PKo) were compared in an ELISA, almost no differences in specificity and sensitivity were seen. This demonstrates that the sera predominantly recognize the common epitopes of OspC tested in this study. In conclusion, we suggest that the OspC-14-kDa antigens ELISA is a suitable test for the detection of an IgM response in early Lyme disease.

Analysis of promoters in Borrelia burgdorferi by use of a transiently expressed reporter gene

A transient chloramphenicol acetyltransferase (CAT) expression system was developed for Borrelia burgdorferi. An Escherichia coli vector containing a promoterless Streptococcus agalactiae cat gene was constructed. Promoters for ospA, ospC, and flaB were placed upstream of this cat gene, and CAT assays were performed in E. coli from these stably maintained plasmids. The plasmids with putative promoters ospA and flaB were found to be approximately 20-fold more active than were the plasmids with ospC or no promoter. The level of activity correlated well with the resistance to chloramphenicol that each plasmid provided. Next, the nonreplicative plasmid constructs were transformed by electroporation into B. burgdorferi. CAT assays were performed by both thin-layer chromatography and the fluor diffusion method. Measurement of CAT activity demonstrated that the ospA promoter was again about 20-fold more active than the promoterless cat gene. The flaB and ospC promoters increased the activity seven- and threefold, respectively, over that with the promoterless construct. This simple transient-expression assay was shown to be an effective method to study promoter function in B. burgdorferi in the absence of a well-developed genetic system.

FlaA, a putative flagellar outer sheath protein, is not an immunodominant antigen associated with Lyme disease

FlaA was recently found to be associated with flagellar filaments of Borrelia burgdorferi. We tested whether antibodies to this protein are a good indicator of infection, as antibodies to FlaA proteins in other spirochetal infections show an increase in titer. Although overproduction of intact FlaA was highly toxic to Escherichia coli, truncated proteins which lacked the N-terminal signal sequence could be successfully overexpressed. Immunoblotting with sera from mammalian hosts infected with B. burgdorferi indicated that FlaA is not an immunodominant antigen in Lyme disease. However, sera from two patients reacted with both recombinant and native FlaA protein, suggesting that B. burgdorferi FlaA was antigenic and expressed in vivo.

The flgK motility operon of Borrelia burgdorferi is initiated by a sigma 70-like promoter

A cluster of flagellar genes of Borrelia burgdorferi was identified and sequenced. This cluster comprises an operon, designated the flgK operon, which is initiated by a sigma 70-like promoter. The flgK operon consists of flbF (function unknown), flgK (encoding HAP1), flgL (encoding HAP3) and orfX (function unknown), and maps at 185 kb on the chromosome. In other bacteria, the hook-associated proteins HAP1 and HAP3 connect the flagellar filament to the hook and are required for the last stage of flagellar assembly. Reverse transcriptase-PCR analysis indicated that flbF through to orfX are transcribed as a single mRNA, and primer extension analysis revealed that transcription of the flgK operon is initiated by a sigma 70-like promoter upstream of flbF. Subcloning the flgK promoter element into a promoter probe cat vector revealed that the flgK promoter element had strong activity in both Escherichia coli and Salmonella typhimurium. In addition, when this construct was transformed into a fliA mutant of S. typhimurium which lacked a functional flagellar-specific sigma 28 factor, the flgK promoter was still functional. Based on these results, the promoter element of the flagellin gene (fla, hereafter referred to as flaB) was re-examined. flaB encodes the flagellar filament protein, and a sigma gp33-34-like promoter has been reported to be involved in the transcription of this gene. A transcriptional start point was found 1 bp downstream of the reported start site. The sequence around -10 and -35 are consistent with the presence of a sigma 70-like promoter in addition to the putative sigma gp33-34-like promoter for flaB. In contrast to the flgK promoter element, no activity was detected after subcloning a flaB promoter element into the promoter probe cat vector. Because a sigma 70-like promoter rather than a unique flagellar sigma factor is involved in the later stage of flagellar assembly, the regulation of B. burgdorferi flagellar genes is evidently different from that of other bacteria.

Identification of a large motility operon in Borrelia burgdorferi by semi-random PCR chromosome walking

Motility has been implicated in the invasive process of Borrelia burgdorferi (Bb), the etiologic agent of Lyme disease. To identify Bb motility related genes, we used a method termed 'semi-random PCR chromosome walking' (SRPCW) to walk through a large motility gene cluster. The major advantage of this approach over other PCR walking methods is that it employs a secondary PCR amplification of cloned fragments which can be readily sequenced and analyzed. Starting with a primer specific to flgE, we identified and sequenced 14 open reading frames (ORFs) spanning 11 kb downstream of the flgE gene. The genes identified include flbD, motA, motB, fliL, fliM, fliN, fliZ, fliP, fliQ, fliR, flhB, flhA, flhF and flbE. Twelve of the deduced proteins shared extensive homology with flagellar proteins from other bacteria. The gene products and order of genes within this cluster are most similar to those of Treponema pallidum (Tp) and Bacillus subtilis (Bs). One of the unique genes identified, flbD, demonstrated homology to an ORF from the same operon of Tp. Another ORF, flbE, showed similarity to genes from both Tp and Bs. RT-PCR and primer extension analysis revealed that this gene cluster is transcribed as a single unit indicating that it is part of a large motility operon spanning more than 21 kb. Antisera to Escherichia coli and Salmonella typhimurium FliN, FliM, FlhB and FlhA reacted with proteins of the predicted molecular weights in cell lysates of Bb. The results suggest that the flagellar system is highly conserved in evolution and thus underscore the importance of motility in bacterial survival and pathogenesis.

Mutagenesis of Burkholderia pseudomallei with Tn5-OT182: isolation of motility mutants and molecular characterization of the flagellin structural gene

Burkholderia pseudomallei is a human and animal pathogen in tropical regions, especially Southeast Asia and northern Australia. Currently little is known about the genetics and molecular biology of this organism. In this report, we describe the mutagenesis of B. pseudomallei with the transposon Tn5-OT182. B. pseudomallei 1026b transposon mutants were obtained at a frequency of 4.6 x 10(-4) per initial donor cell, and the transposon inserted randomly into the chromosome. We used Tn5-OT182 to identify the flagellin structural gene, fliC. We screened 3,500 transposon mutants and identified 28 motility mutants. Tn5-OT182 integrated into 19 unique genetic loci encoding proteins with homology to Escherichia coli and Salmonella typhimurium flagellar and chemotaxis proteins. Two mutants, MM35 and MM36, contained Tn5-OT182 integrations in fliC. We cloned and sequenced fliC and used it to complement MM35 and MM36 in trans. The fliC transcriptional start site and a sigmaF-like promoter were identified by primer extension analysis. We observed a significant difference in the expression of two distinct fliC-lacZ transcriptional fusions during bacterial growth, suggesting the presence of a latent intragenic transcriptional terminator in fliC. There was no significant difference in the virulence of 1026b compared to that of MM36 in diabetic rats or Syrian hamsters, suggesting that flagella and/or motility are probably not virulence determinants in these animal models of B. pseudomallei infection. A phylogenetic analysis based on the flagellins from a variety of bacterial species supported the recent transfer of B. pseudomallei from the genus Pseudomonas to Burkholderia.

The flagellin gene of Borrelia miyamotoi sp. nov. and its phylogenetic relationship among Borrelia species

We have cloned and sequenced the flagellin gene from Borrelia miyamotoi strain HT31 and compared it with previously published flagellin sequences. Sequence similarity analysis demonstrated that strain HT31 is phylogenetically distant from the three species of Lyme disease borreliae is deeply branched into the relapsing fever borrelia cluster. The result was in full agreement with the classification of Borrelia strains using 16S tRNA sequences. This finding indicates that a phylogenetic analysis using flagellin gene sequences might be useful for classification of Borrelia strains.

Evaluation of a Lyme disease enzyme immunoassay using the 41-G fragment of flagellin

An immunogenic region of the Borrelia burgdorferi flagellin encompassing amino acids 197-273 and designated 41-G was evaluated as an antigen in an enzyme immunoassay (EIA) for Lyme disease on a routine basis in a reference laboratory. Sera that tested positive for Lyme disease by EIA using 41-G or the whole-cell Borrelia burgdorferi lysate as the antigen were also evaluated by immunoblot for reactivity with Borrelia burgdorferi, and the patient's clinical history was determined retrospectively by a questionnaire distributed to the referring physician. The sensitivity of the 41-G based EIA for the serologic diagnosis of Lyme disease, when compared with that of the Borrelia burgdorferi lysate EIA, was 70% (35 of 50). These data demonstrate that 41-G has utility as an antigen in EIA, although the sensitivity is at present less than that of the assay employing the Borrelia burgdorferi whole-cell lysate.

Use of a hybrid protein consisting of the variable region of the Borrelia burgdorferi flagellin and part of the 83-kDa protein as antigen for serodiagnosis of Lyme disease

A hybrid protein consisting of the variable region of the Borrelia burgdorferi flagellin (an 18-kDa fragment) and a 59-kDa fragment (lacking the N-terminal part) of the 83-kDa protein has been constructed by genetic engineering. It was expressed as a nonfusion protein of an apparent molecular weight of 77,000 in Escherichia coli. The suitability of this new antigen for the diagnosis of Lyme disease was tested by immunoblotting; for comparison, the recombinant variable region of the flagellin, the 18-kDa fragment (p18), and the whole recombinant 83-kDa protein (p83), both expressed in E. coli, were used. A total of 120 serum samples from various stages of Lyme disease, which were positive in two serological assays, a passive hemagglutination assay and an indirect immunofluorescence assay, were tested. By indirect immunofluorescence, 74 samples were positive for immunoglobulin G (IgG) antibodies and 72 were positive for IgM antibodies. Of these serum samples, 69 of 74 (93%) contained IgG antibodies against p18 and/or p83, and IgG antibodies were detected by the hybrid protein in 67 (90%) samples. IgM antibodies against p18 and/or p83 were detected in 60 of 72 (83%) serum samples, and 57 (79%) serum samples were reactive with the hybrid protein. Twenty serum samples of patients with a history of syphilis and 40 serum samples, negative in routine B. burgdorferi serology, were tested as controls. The hybrid protein, made up of specific epitopes of an early (p18) and late (p83) antigen, is recognized by almost the same number of patient serum samples as the individual antigens.

Immunoblot using recombinant antigens derived from different genospecies of Borrelia burgdorferi sensu lato

Immunodominant proteins are variable in molecular and antigenic structure among different genospecies of Borrelia burgdorferi sensu lato. We have recently developed an immunoblot using five recombinant antigens: the chromosomal-encoded B. burgdorferi proteins p100, the flagellin and an internal flagellin fragment thereof, and the plasmid-encoded outersurface proteins A (OspA) and C (OspC). In the present study the same antigens (derived from strain PKo, genospecies B. afzelii) were compared with the homologous recombinant proteins from strain B31 (genospecies B. burgdorferi sensu stricto) and with OspA, OspC and the internal flagellin fragment from strain PBi (genospecies B. garinii). Patients with neuroborreliosis (n = 28) and patients with acrodermatitis chronica atrophicans (n = 20) were investigated in the IgG immunoblot; the IgM immunoblot was performed only in patients with neuroborreliosis. There was a small increase in the detection rate of OspA-specific IgG or IgM antibodies using the different variants of recombinant OspA; however, OspA remained an insensitive antigen for antibody detection in Lyme borreliosis. The same was true to OspC-specific IgG antibodies. The sensitivity of OspC, which is the immunodominant antigen for IgM antibody detection, could not be increased using recombinant antigens derived from different strains. However, some sera which were negative in the recombinant immunoblot reacted with OspC in the conventional immunoblot using B. burgdorferi whole cell lysate as antigen. The most unexpected finding was the high degree of immunological heterogeneity of the internal flagellin fragments: IgG antibodies were detected in 18 of 48 patients using B31 fragments, in 25 of 48 using PKo fragments, in 23 of 48 using PBi fragments versus 33 of 48 when the three recombinant proteins were combined. PKo-derived fragments were more sensitive for antibody detection in patients with acrodermatitis chronica atrophicans, B31- and PBi-derived fragments for antibody detection in patients with neuroborreliosis. This is in agreement with the fact that isolates from patients with neuroborreliosis are predominantly belonging to the genospecies B. burgdorferi sensu stricto and B. garinii. For detection of IgM antibodies in sera from patients with neuroborreliosis, recombinant internal fragments derived from strains B31 and PBi were more sensitive than the PKo-derived fragment. The best discrimination between neuroborreliosis sera and control sera was achieved when the IgM blot was performed using recombinant internal flagellin fragments derived from strains PKo and PBi and OspC derived from B31 or PKo.

Outer surface proteins E and F of Borrelia burgdorferi, the agent of Lyme disease

We report the cloning and characterization of two outer surface proteins (Osps), designated OspE and OspF, from strain N40 of Borrelia burgdorferi, the spirochetal agent of Lyme disease. The ospE and ospF genes are structurally arranged in tandem as one transcriptional unit under the control of a common promoter. The ospE gene, located at the 5' end of the operon, is 513 nucleotides in length and encodes a 171-amino-acid protein with a calculated molecular mass of 19.2 kDa. The ospF gene, located 27 bp downstream of the stop codon of the ospE gene, consists of 690 nucleotides and encodes a protein of 230 amino acids with a calculated molecular mass of 26.1 kDa. Pulsed-field gel electrophoresis showed that the ospE and ospF genes are located on a 45-kb plasmid. Comparison of the leader sequences of OspE and OspF with those of the four known B. burgdorferi Osps (OspA, OspB, OspC, and OspD) reveals a hydrophobic domain and a consensus cleavage sequence (L-X-Y-C) recognized by signal peptidase II, and [3H]palmitate labeling shows that OspE and OspF are lipoproteins. Immunofluorescence studies demonstrated that both the OspE and OspF proteins are surface exposed. These features are consistent with the finding that OspE and OspF are B. burgdorferi surface lipoproteins.

Recombinant immunoblot in the serodiagnosis of Lyme borreliosis. Comparison with indirect immunofluorescence and enzyme-linked immunosorbent assay

A recombinant immunoblot was developed for detection of IgM and IgG antibodies in patients with Lyme borreliosis. The recombinant antigens were the chromosomal-encoded Borrelia burgdorferi proteins p100, the flagellin and an internal flagellin fragment thereof as well as the plasmid-encoded outer surface proteins A (OspA) and C (OspC). A panel of 144 sera from patients with Lyme borreliosis (erythema migrans, n = 31; neuroborreliosis state II, n = 60; Lyme arthritis, n = 24 and acrodermatitis chronica atrophicans, n = 19) have been investigated and the results have been compared to the immunofluorescence absorption test (IFA-ABS) and to two different enzyme-linked immunosorbent assays [the flagellin ELISA and a newly developed ELISA (OGP-ELISA)]. The two ELISAs were comparable in sensitivity, whereas the IFA-ABS was less sensitive for IgM antibody but equally sensitive for IgG antibody detection. Immunoblot analysis revealed that IgG antibodies are mainly reactive with p100 and the internal flagellin fragment (sensitivity 51% and 32%, respectively) and rarely with OspC (14%). All patients with late Lyme borreliosis had IgG antibodies against the p100. IgM antibodies were predominantly directed against OspC (43%) and in a lower extent against the internal flagellin fragment and p100 (15% and 13%, respectively). The complete flagellin was not useful due to a high number of unspecific reactions with control sera and the OspA was only exceptionally reactive in Lyme borreliosis patients. The sensitivity of IgM antibody detection could be increased in cases with early Lyme borreliosis from 46% to 65% when the OspC blot was performed in addition to the flagellin ELISA, or from 56% to 65% when performed in addition to the OGP-ELISA. The recombinant blot is, therefore, a valuable diagnostic test to increase sensitivity of early antibody detection and is regarded as a valuable confirmatory test also in late disease.

Serologic analysis of dogs, horses, and cottontail rabbits for antibodies to an antigenic flagellar epitope of Borrelia burgdorferi

Enzyme-linked immunosorbent assays (ELISA) and immunoblots using either whole-cell lysates of Borrelia burgdorferi or an antigenic region of flagellin (41-G) as the antigen were performed, and the abilities of the two assays to detect antibodies to this spirochete in dog, cottontail rabbit, and horse sera were compared. Assays using whole-cell B. burgdorferi lysates as the antigen were more sensitive for detecting antibodies. ELISA with 41-G as the antigen were specific for Borrelia antibodies but were not as sensitive as the assays with whole-cell lysates coated to the solid phase. Use of recombinant full-length flagellin, rather than 41-G, as the antigen in immunoblots increased the sensitivity of each assay. However, antibodies to other bacterial antigens cross-react with whole flagellin and may account for false-positive results. Antibodies to B. burgdorferi outer surface protein A or B were usually undetected when the sera were tested by immunoblotting methods. Borrelia lysates or the 41-G antigen may be used in ELISA or immunoblots to document host exposure to this spirochete. The use of 41-G as the antigen may increase the specificity of an assay or help confirm the serologic diagnosis of Lyme borreliosis in dogs, horses, and cottontail rabbits.

Western blot as a tool in the diagnosis of Lyme borreliosis

Borrelia burgdorferi is the causative agent of Lyme borreliosis, a multisystem disorder, which can mimic numerous immune disorders and inflammatory diseases. Laboratory diagnosis of Borrelia infection relies on immunodiagnostic assays, which, however, are hampered by unsatisfactory specificity. The Western blot technique has been employed to analyze the humoral immune response in Lyme borreliosis and is used as a serodiagnostic confirmation test. The most important immunodominant proteins of Borrelia burgdorferi are the 94 kDa, 60 kDa, 41 kDa (flagellin), 34 kDa (Osp B), 31 kDa (Osp A), 30 kDa, 21 kDa (Osp C), and 17/18 kDa proteins. Whereas the 60 kDa, 41 kDa, and 34 kDa constituents reveal a marked cross-antigenicity with other spirochetes and even more distantly related bacteria, antibodies against the 94 kDa, 31 kDa and 21 kDa proteins are largely species-specific. The early immune response in Lyme borreliosis is triggered mainly by the flagellin. In the later stage a wide range of immunogenic proteins is involved, with the 94 kDa antigen being the best marker for late immune response. If the Western blot is used for diagnostic purposes the differences between early and late-stage immunogenicity of Borrelia proteins must be taken into account. Interpretation criteria for blot positivity in early-stage borreliosis are primarily based on the presence of the 21 kDa band and the semiquantitatively recorded intensity of the 41 kDa band. In the diagnosis of late-stage infection, blot positivity relies on the presence of the 94 kDa, 39 kDa, 31 kDa, 30 kDa and 21 kDa bands.

Cross-reactive antigenic domains of the flagellin protein of Borrelia burgdorferi

The p41 flagellin of Borrelia burgdorferi is the most common antigen recognized by serum of patients with Lyme borreliosis. This antigen shares amino acid homology, particularly in the amino and carboxy termini, with periflagellar antigens found in other microorganisms including Treponema pallidum. We cloned and expressed the p41 open reading frame in Escherichia coli and expressed it both as TrpE fusion and full-length unfused proteins. Also, we generated deletion constructs of various portions of the gene. Sera from patients with late Lyme borreliosis and secondary syphilis were used to identify the recombinant proteins by immunoblot analysis. Sera from 26 patients with Lyme borreliosis, 20 with secondary syphilis and 10 controls were used to identify cross-reactive domains of the B. burgdorferi flagellin. The variable region (amino acids 131-234) of the protein was recognized by 59% (15/26) of patients with late Lyme borreliosis compared to 30% (6/20) of patients with secondary syphilis and no (0/10) control patients. It appears that cross-reactive epitopes between B. burgdorferi and T. pallidum extend to the variable region of the flagellin.

Linear chromosomal physical and genetic map of Borrelia burgdorferi, the Lyme disease agent

A physical map of the 952 kbp chromosome of Borrelia burgdorferi Sh-2-82 has been constructed. Eighty-three intervals on the chromosome, defined by the cleavage sites of 15 restriction enzymes, are delineated. The intervals vary in size from 96 kbp to a few hundred bp, with an average size of 11.5 kbp. A striking feature of the map is its linearity; no other bacterial groups are known to have linear chromosomes. The two ends of the chromosome do not hybridize with one another, indicating that there are no large common terminal regions. The chromosome of this strain was found to be stable in culture; passage 6, 165 and 320 cultures have identical chromosomal restriction maps. We have positioned all previously known Borrelia burgdorferi chromosomal genes and several newly identified ones on this map. These include the gyrA/gyrB/dnaA/dnaN gene cluster, the rRNA gene cluster, fla, flgE, groEL (hsp60), recA, the rho/hip cluster, the dnaK (hsp70)/dnaJ/grpE cluster, the pheT/pheS cluster, and the genes which encode the potent immunogen proteins p22A, p39 and p83. Our electrophoretic analysis detects five linear and at least two circular plasmids in B. burgdorferi Sh-2-82. We have constructed a physical map of the 53 kbp linear plasmid and located the operon that encodes the two major outer surface proteins ospA and ospB on this plasmid. Because of the absence of functional genetic tools for this organism, these maps will serve as a basis for future mapping, cloning and sequencing studies of B. burgdorferi.

Detection of Borrelia burgdorferi by nested polymerase chain reaction in cerebrospinal fluid and urine of children with neuroborreliosis

Diagnosis of neuroborreliosis is often difficult since history and clinical presentation may be non-specific and serological tests may initially be negative. We therefore tested the polymerase chain reaction (PCR) for the detection of borrelial sequences in CSF and urine samples of consecutive children with neuroborreliosis seen in a single summer season. Four of eight children were negative in serum for antibodies to Borrelia burgdorferi. Two of eight children were PCR-positive in CSF and one other child was positive in urine. In two out of four children PCR was the only laboratory test confirming the clinical diagnosis. All children recovered after treatment with third generation cephalosporins. When seven of eight children were re-examined 6 months later all were healthy and antibodies to B. burgdorferi were detected in their serum. PCR may assist the paediatrician in establishing a diagnosis of neuroborreliosis; however, a negative result does not rule out neuroborreliosis. PCR is an adjunct, but no substitute for clinical judgement and serology.

Analysis of the humoral response to the flagellin protein of Borrelia burgdorferi: cloning of regions capable of differentiating Lyme disease from syphilis

Selected regions of the Borrelia burgdorferi flagellin gene (fla) that exhibit high or low homology with related genes from other bacterial species were amplified by the polymerase chain reaction and expressed as fusion proteins in Escherichia coli. Purified fusion proteins were assayed for antibody reactivity in a microtiter plate enzyme-linked immunosorbent assay with sera from Lyme disease patients as well as syphilitic and normal sera. Immunoglobulin G antibody from Lyme disease patient sera reacted predominantly with the central portion of the protein. The region of the flagellin protein encompassing amino acids 64 to 311 detected nearly all of the immunoglobulin G-positive Lyme sera and only reacted with 1 of 26 syphilis patient serum samples. In contrast, 12 of 26 syphilis patient serum samples and 2 of 47 normal serum samples reacted with the amino terminus of the flagellin protein, whereas 4 of 26 syphilis patient serum samples and 7 of 47 normal serum samples reacted with the carboxyl terminus. The central region containing amino acids 64 to 311 may be employed diagnostically to differentiate antibodies to B. burgdorferi from antibodies to Treponema pallidum. In addition, this region also was recognized by immunoglobulin M in the Lyme patient sera, indicating its potential usefulness as a marker for early Lyme disease.

Genetic heterogenity of the genes coding for the outer surface protein C (OspC) and the flagellin of Borrelia burgdorferi

The ospC gene coding for the outer surface protein OspC and the fla gene coding for the flagellin have been investigated in three different Borrelia burgdorferi sensu lato strains. These strains (the North American strain B31 and the European strains PKo and PBi) derive from various biological sources (lxodes dammini, human skin and human CSF) and belong to three different B. burgdorferi OspA serotypes and genospecies (OspA serotype 1, B. burgdorferi sensu stricto; OspA serotype 2, group VS461 and OspA serotype 4, B. garinii, respectively). The ospC and fla genes of the respective strains have been amplified by polymerase chain reaction, cloned in pUC8 and sequenced. The fla as well as the ospC genes were different among the three strains investigated. In general the fla genes are more conserved than the ospC genes. The fla genes have the same length of 1008 nucleotides coding for proteins of 336 amino acids, whereas the ospC genes differ in length. The ospC genes of strains B31, PKo and PBi have 630, 636 and 621 nucleotides encoding proteins of 210, 212 and 207 amino acids, respectively. The ospC genes exhibit sequence identities between 70% and 74% among each other, sequence identities of the fla genes are in the range 96-97%. The ospC genes could be expressed in Escherichia coli to obtain proteins with and without leader peptides. The expression of the fla gene and an internal gene fragment resulted in the complete flagellin protein and a truncated protein (amino acids 129-251). The different ospC and fla gene products were immunoreactive with monoclonal antibodies and human sera and, thus, enlarge the spectrum of recombinant antigens to improve antibody detection in patients with Lyme borreliosis.

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.

Spirochete chemotaxis, motility, and the structure of the spirochetal periplasmic flagella

Spirochetes have a unique motility system that is characterized by flagellar filaments contained within the outer membrane sheath. Direct evidence using video microscopy has recently been obtained which indicates that these periplasmic flagella (PF) rotate in several spirochetal species. This rotation generates thrust. As shown for one spirochete, Spirochaeta aurantia, motility is driven by a proton motive force. Spirochete chemotaxis has been most thoroughly studied in S. aurantia. This spirochete exhibits three distinct behaviours, runs of smooth swimming, reversals and flexing. These behaviours are modulated by addition of attractants such that S. aurantia swims towards higher concentrations of attractants in a spatial gradient. Unlike the prototypical bacterium, Escherichia coli, chemotaxis in S. aurantia involves fluctuations in membrane potential. The PF of a number of spirochetes have been examined in considerable detail. For most species, the PF filaments are complex, consisting of an assembly of several different polypeptides. There are several antigenically related core polypeptides surrounded by an outer layer consisting of a different polypeptide. Borrelia burgdorferi and Spirochaeta zuelzerae represent exceptions where the filaments are composed of a single major polypeptide species. The genes encoding the filament polypeptides from several spirochete species have been cloned and analysed. Apparently, the outer layer polypeptides of S. aurantia, Treponema pallidum and Serpulina hyodysenteriae are transcribed from sigma-70-like promoters, whereas the core polypeptide genes are transcribed from sigma-28-like promoters. A gene encoding the hook polypeptide in Treponema phagedenis has been cloned and analysed. The product of this gene shows significant similarity to the E. coli hook protein, FlgE, and homologs have been identified in T. pallidum and B. burgdorferi.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigenic variation and strain heterogeneity in Borrelia spp

Antigenic variation and strain heterogeneity have been demonstrated for the pathogenic Borrelia species, i.e. B. burgdorferi and the relapsing fever borreliae. In relapsing fever, new borrelia serotypes emerge at a high rate spontaneously, a mechanism that is caused by DNA rearrangements on linear plasmid translocating genes coding for variable major proteins from previous silent to expression sites (i.e. from inner sites to telomeric sites of the plasmid). As a result of this variation, the borreliae escape the immune response of the host, thus leading to the relapse phenomenon. In B. burgdorferi, which is the causative agent of the multisystem disorder Lyme borreliosis, there is also a growing body of findings that antigenic variation is involved in pathogenesis of the disease. Phenotypic variation of strains in vitro concerns the size and the amount of surface-associated proteins (OspA, OspB and pC). There are indications that OspA and OspB truncations are due to deletions within the ospAB operon caused by recombination events, and that OspA/OspB-less mutants lack the 49-kb plasmid that bears the ospAB operon. With the increasing number of isolates obtained from various geographic and biological sources, it became apparent that B. burgdorferi is immunologically and genetically more heterogeneous, as previously believed. The major outer surface proteins OspA and OspB (which have been efficient antigens in vaccine studies) are heterogeneous at a genetic level. The same degree of genetic non-identity was observed for the pC protein. Other proteins like flagellin and the highly specific immunodominant p100 range protein show a lower degree of non-identity. Recombinant OspA, pC, p100 range protein and flagellin have been hyperexpressed in E. coli and these proteins are immunologically reactive. This allows further research for development of vaccines and diagnostic tools. B. burgdorferi isolates have been investigated with genotyping (DNA hybridization, PCR and 16S rRNA analysis) as well as serotyping by various authors. Comparison of the different methods has shown good agreement when the same strains have been investigated. No correlation could be found between different phenotypic and genotypic groups with respect to the ability to cause arthritis in SCID mice. A serotyping system based on immunological differences in OspA detected by a panel of monoclonal antibodies has been proposed. Serotyping a large number of B. burgdorferi isolates has shown a striking predominance of the OspA serotype 2 among European isolates from human skin, in contrast to isolates from ticks or CSF.(ABSTRACT TRUNCATED AT 400 WORDS)

Mapping the major antigenic domains of the native flagellar antigen of Borrelia burgdorferi

Purified flagellar protein (p41) of Borrelia burgdorferi (strain B31) was subjected to chemical cleavage with hydroxylamine or proteolysis with V8 protease, endoproteinase Asp-N, or alpha-chymotrypsin. The resulting polypeptides were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their positions in the published DNA sequence of the p41 protein were determined by amino-terminal sequencing and amino acid analysis. Epitope specificities of antibody binding by a monoclonal antibody raised by immunization of mice with purified flagella and pooled sera from patients with multiple erythema migrans, late Lyme borreliosis, or secondary syphilis were analyzed by Western blots (immunoblots) of peptides transferred to Immobilon polyvinylidene difluoride filters. The major epitope binding one murine monoclonal antibody (158) was localized to a carboxy-terminal domain that includes residues 300 to 336. The dominant epitopes binding human polyclonal antibodies are in the central portion of the molecule (residues 182 to 218) that is not conserved compared with other bacterial flagellins. Additional reactive epitopes were identified in the amino-terminal domain of the protein. Sera from patients with syphilis bound strongly to the amino-terminal conserved domain, providing a structural basis for cross-reactivity seen in standard enzyme-linked immunosorbent assays, but not to the central part of the molecule. Specific and cross-reactive antigenic determinants need to be considered in the design of improved immunodiagnostics for spirochetal diseases.

Nucleotide sequence of the ospAB operon of a Borrelia burgdorferi strain expressing OspA but not OspB

The nucleotide sequence of a 1.6-kb clone containing the gene for outer surface protein A (OspA) of a German strain (GO2) of Borrelia burgdorferi was determined. The deduced amino acid sequence showed a homology of 82% to the OspA molecules from three other B. burgdorferi strains. The best-conserved region was recognized at the 36-amino-terminal amino acids of OspA. OspB could not be identified in the strain investigated, probably because the nucleotide sequence of the ospAB operon prevented expression of the OspB gene.

Cross-reactive proteins of Borrelia burgdorferi

The specificity of serological tests for Lyme borreliosis is impaired by cross-reacting antibodies. In order to select antigens for more specific tests, specific and cross-reactive proteins of Borrelia burgdorferi must be identified. Therefore, to analyze cross reactions of Borrelia burgdorferi with other bacteria, rabbit immune sera against heterologous bacteria (Borrelia hermsii, Treponema pallidum, Treponema phagedenis, Leptospira interrogans (serogroup grippotyphosa), Neisseria meningitidis, Haemophilus influenzae, Yersinia enterocolitica (serotypes O3 and O9), Campylobacter jejuni, Listeria monocytogenes O1, Pseudomonas aeruginosa, Escherichia coli, Salmonella typhimurium, Shigella flexneri and Legionella micdadei) were examined by Western blot using Borrelia burgdorferi as antigen. Broad cross reactivity was shown for Borrelia proteins of the 60-75 kDa range. Other broadly cross-reacting proteins were at the level of p40, p33 and two proteins in the range of 20 kDa. Some of the cross reactions were eliminated by absorption of the sera with Treponema phagedenis. The absorbed antibodies were directed mainly against bands at the level of p33 and bands of the 60 to 75 kDa range. Showing the lowest potential for cross reactivity, p100, p41, OspA and pC seem to be the most suitable antigens for serodiagnosis. In contrast to p100 and OspA, however, p41 and pC showed cross reactivity with immune sera against bacteria not belonging to the genus Borrelia.

The bvgAS locus negatively controls motility and synthesis of flagella in Bordetella bronchiseptica

The products of the bvgAS locus coordinately regulate the expression of Bordetella virulence factors in response to environmental conditions. We have identified a phenotype in Bordetella bronchiseptica that is negatively controlled by bvg. Environmental signals which decrease (modulate) the expression of bvg-activated genes lead to flagellum production and motility in B. bronchiseptica. Wild-type (Bvg+) strains are motile and produce peritrichous flagella only in the presence of modulating signals, whereas Bvg- (delta bvgAS or delta bvgS) strains are motile in the absence of modulators. The bvgS-C3 mutation, which confers signal insensitivity and constitutive activation of positively controlled loci, eliminates the induction of motility and production of flagellar organelles. The response to environmental signals is conserved in a diverse set of clinical isolates of both B. bronchiseptica and B. avium, another motile Bordetella species; however, nicotinic acid induced motility only in B. bronchiseptica. Purification of flagellar filaments from B. bronchiseptica strains by differential centrifugation followed by CsCl equilibrium density gradient centrifugation revealed two classes of flagellins of Mr 35,000 and 40,000. A survey of clinical isolates identified only these two flagellin isotypes, and coexpression of the two forms was not detected in any strain. All B. avium strains tested expressed a 42,000-Mr flagellin. Amino acid sequence analysis of the two B. bronchiseptica flagellins revealed 100% identity in the N-terminal region and 80% identity with Salmonella typhimurium flagellin. Monoclonal antibody 15D8, which recognizes a conserved epitope in flagellins in members of the family Enterobacteriaceae, cross-reacted with flagellins from B. bronchiseptica and B. avium. Our results highlight the biphasic nature of the B. bronchiseptica bvg regulon and provide a preliminary characterization of the Bvg-regulated motility phenotype.

Prognostic B-cell epitopes on the flagellar protein of Borrelia burgdorferi

Overlapping decapeptides based on the flagellin sequence of Borrelia burgdorferi B31 (G. S. Gassmann, M. Kramer, U. B. Göbel, and R. Wallich, Nucleic Acids Res. 17:3590, 1989) were used to identify immunologically reactive regions of flagellin. Five serum specimens from patients with late manifestations of Lyme disease and borrelia-specific monoclonal antibody H9724 reacted with an epitope in the central region of the flagellar protein (amino acids 205 to 226), which is heterologous to the amino acid sequences of other bacterial flagellins. This epitope was not recognized by human sera with antibodies to Treponema pallidum, sera of healthy individuals, or sera from patients with stage I or II of Lyme disease.

Repeated detection of Borrelia burgdorferi DNA in synovial fluid of a child with Lyme arthritis

In the pathogenesis of late Lyme borreliosis the relative importance of the causative organism, Borrelia burgdorferi, and the immune response of the host, including autoimmune phenomena, is not yet known. We describe a 7-year-old boy with Lyme arthritis from whom two synovial fluid samples were obtained 5 months apart and up to 17 months after the first appearance of arthritis. Both synovial fluid specimens were shown to contain borrelial DNA by nested polymerase chain reaction for the amplification of portions of the genes for flagellin and OspA. Thus, Borrelia burgdorferi may persist within the joint even during late stages of the disease.