Diversity of OspA and OspC among cerebrospinal fluid isolates of Borrelia burgdorferi sensu lato from patients with neuroborreliosis in Germany

BS, Raghuraman V, Rajyaguru U, Llamera KE, Andrew L, Anderson AS, Hovius JW, Liberator PA, Simon R, Hao L. Development of a sequence-based in silico OspA typing method for Borrelia burgdorferi sensu lato

Lyme disease (LD), caused by spirochete bacteria of the genus Borrelia burgdorferi sensu lato, remains the most common vector-borne disease in the northern hemisphere. Borrelia outer surface protein A (OspA) is an integral surface protein expressed during the tick cycle, and a validated vaccine target. There are at least 20 recognized Borrelia genospecies, that vary in OspA serotype. This study presents a new in silico sequence-based method for OspA typing using next-generation sequence data. Using a compiled database of over 400 Borrelia genomes encompassing the 4 most common disease-causing genospecies, we characterized OspA diversity in a manner that can accommodate existing and new OspA types and then defined boundaries for classification and assignment of OspA types based on the sequence similarity. To accommodate potential novel OspA types, we have developed a new nomenclature: OspA in silico type (IST). Beyond the ISTs that corresponded to existing OspA serotypes 1-8, we identified nine additional ISTs that cover new OspA variants in B. bavariensis (IST9-10), B. garinii (IST11-12), and other Borrelia genospecies (IST13-17). The IST typing scheme and associated OspA variants are available as part of the PubMLST Borrelia spp. database. Compared to traditional OspA serotyping methods, this new computational pipeline provides a more comprehensive and broadly applicable approach for characterization of OspA type and Borrelia genospecies to support vaccine development.

Allelic Variants of P66 Gene in Borrelia bavariensis Isolates from Patients with Ixodid Tick-Borne Borreliosis

Protein P66 is one of the crucial virulence factors of Borrelia, inducing the production of specific antibodies in patients with ixodid tick-borne borreliosis (ITBB). Various species of Borrelia are characterized by genetic variability of the surface-exposed loop of P66. However, little is known about this variability in Borrelia bavariensis. Here we describe the variability of the nucleotide sequences of P66 gene locus in isolates of B. bavariensis. Analysis of nucleotide sequences of P66 in 27 isolates of B. bavariensis from ITBB patients revealed three allelic variants of this gene. The alignment score of amino acid sequences in the isolates showed amino acid replacements in various positions confirming the presence of three allelic variants. Two of them are characteristic only for some isolates of B. bavariensis of the Eurasian gene pool from various parts of the geographic ranges of B. bavariensis from various samples. At least three allelic variants of P66 B. bavariensis have been identified, which have different amino acid expression, occur with different frequency in ITBB patients and, presumably, can have different effects on the course of the infection.

Utilizing Two Borrelia bavariensis Isolates Naturally Lacking the PFam54 Gene Array To Elucidate the Roles of PFam54-Encoded Proteins

Lyme borreliosis is the most common vector-borne disease in the Northern Hemisphere, caused by spirochetes belonging to the Borrelia burgdorferi sensu lato species complex, which are transmitted by ixodid ticks. B. burgdorferi sensu lato species produce a family of proteins on the linear plasmid 54 (PFam54), some of which confer the functions of cell adhesion and inactivation of complement, the first line of host defense. However, the impact of PFam54 in promoting B. burgdorferi sensu lato pathogenesis remains unclear because of the hurdles to simultaneously knock out all PFam54 proteins in a spirochete. Here, we describe two Borrelia bavariensis strains, PBN and PNi, isolated from patients naturally lacking PFam54 but maintaining the rest of the genome with greater than 95% identity to the reference B. bavariensis strain, PBi. We found that PBN and PNi less efficiently survive in human serum than PBi. Such defects were restored by introducing two B. bavariensis PFam54 recombinant proteins, BGA66 and BGA71, confirming the role of these proteins in providing complement evasion of B. bavariensis. Further, we found that all three strains remain detectable in various murine tissues 21 days post-subcutaneous infection, supporting the nonessential role of B. bavariensis PFam54 in promoting spirochete persistence. This study identified and utilized isolates deficient in PFam54 to associate the defects with the absence of these proteins, building the foundation to further study the role of each PFam54 protein in contributing to B. burgdorferi sensu lato pathogenesis. IMPORTANCE To establish infections, Lyme borreliae utilize various means to overcome the host's immune system. Proteins encoded by the PFam54 gene array play a role in spirochete survival in vitro and in vivo. Moreover, this gene array has been described in all currently available Lyme borreliae genomes. By investigating the first two Borrelia bavariensis isolates naturally lacking the entire PFam54 gene array, we showed that both patient isolates display an increased susceptibility to human serum, which can be rescued in the presence of two PFam54 recombinant proteins. However, both isolates remain infectious to mice after intradermal inoculation, suggesting the nonessential role of PFam54 during the long-term, but may differ slightly in the colonization of specific tissues. Furthermore, these isolates show high genomic similarity to type strain PBi (>95%) and could be used in future studies investigating the role of each PFam54 protein in Lyme borreliosis pathogenesis.

Prevalence of tick-borne encephalitis virus and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks in Lower Bavaria and Upper Palatinate, Germany

Lyme borreliosis and tick-borne encephalitis (TBE) are the most common tick-borne diseases in Germany. We collected Ixodes ricinus ticks from 16 high-risk and four low-risk sites distributed in Lower Bavaria and Upper Palatinate based on the number of human TBE cases recorded at the Robert Koch Institute from 2001 to 2009. A total of 8805 questing ticks (8203 nymphs, 602 adults) were collected in 2010 and examined in pools for the presence of tick-borne encephalitis virus (TBEV) using real-time RT-PCR. Overall TBEV prevalence evaluated as the minimum infection rate (MIR) was 0.26 % (23 positive pools/8805 ticks in 1029 pools). TBEV was detected at seven of the 16 high-risk sites, where MIR ranged from 0.16 to 2.86 %. A total of 3969 ticks were examined by PCR for infection with Borrelia burgdorferi sensu lato (s.l.) targeting the 5 S-23 S rRNA intergenic spacer (IGS) region. IGS nucleotide sequences were used to determine genospecies. Selected positive Borrelia samples were subjected to PCR and sequencing targeting the OspA gene, providing 46 sequences for molecular phylogenetic analysis. Of the 3969 questing ticks, 506 (12.7 %) were positive for B. burgdorferi s.l. Seven B. burgdorferi s.l. genospecies were identified: B. afzelii (41.3 %), B. garinii (19 %), B. valaisiana (13.8 %), B. burgdorferi sensu stricto (11.1 %), B. spielmanii (0.4 %), B. lusitaniae (0.2 %), and Candidatus B. finlandensis (0.6 %). Mixed infections were identified in 13.6 % of the ticks. The rate of infection in questing ticks varied among sites from 5.6 % (72 examined, four positive) to 29.5 % (88 examined, 26 positive). B. burgdorferi s.l. occurred at all 20 sites, whereas TBEV was detected only at the high-risk sites where more human TBE cases were reported compared to low-risk sites.

Infection history of the blood-meal host dictates pathogenic potential of the Lyme disease spirochete within the feeding tick vector

Lyme disease in humans is caused by several genospecies of the Borrelia burgdorferi sensu lato (s.l.) complex of spirochetal bacteria, including B. burgdorferi, B. afzelii and B. garinii. These bacteria exist in nature as obligate parasites in an enzootic cycle between small vertebrate hosts and Ixodid tick vectors, with humans representing incidental hosts. During the natural enzootic cycle, infected ticks in endemic areas feed not only upon naïve hosts, but also upon seropositive infected hosts. In the current study, we considered this environmental parameter and assessed the impact of the immune status of the blood-meal host on the phenotype of the Lyme disease spirochete within the tick vector. We found that blood from a seropositive host profoundly attenuates the infectivity (>104 fold) of homologous spirochetes within the tick vector without killing them. This dramatic neutralization of vector-borne spirochetes was not observed, however, when ticks and blood-meal hosts carried heterologous B. burgdorferi s.l. strains, or when mice lacking humoral immunity replaced wild-type mice as blood-meal hosts in similar experiments. Mechanistically, serum-mediated neutralization does not block induction of host-adapted OspC+ spirochetes during tick feeding, nor require tick midgut components. Significantly, this study demonstrates that strain-specific antibodies elicited by B. burgdorferi s.l. infection neutralize homologous bacteria within feeding ticks, before the Lyme disease spirochetes enter a host. The blood meal ingested from an infected host thereby prevents super-infection by homologous spirochetes, while facilitating transmission of heterologous B. burgdorferi s.l. strains. This finding suggests that Lyme disease spirochete diversity is stably maintained within endemic populations in local geographic regions through frequency-dependent selection of rare alleles of dominant polymorphic surface antigens.

Natural foci of Borrelia lusitaniae in a mountain region of Central Europe

Lyme borreliosis is the most prevalent tick-borne disease in Europe. It is caused by spirochaetes of the Borrelia burgdorferi sensu lato (s.l.) complex and transmitted to humans by ticks of the genus Ixodes. Borrelia afzelii, Borrelia garinii, and Borrelia valaisiana are the most common genospecies in Central Europe. In contrast, Borrelia lusitaniae predominates in Mediterranean countries such as Portugal, Morocco, and Tunisia. In Slovakia, its prevalence is low and restricted to only a few sites. The aim of our research was to study the expansion of ticks into higher altitudes in the ecosystem of the Malá Fatra mountains (north Slovakia) and their infection with B. burgdorferi s.l. pathogens. Questing ticks were collected by flagging in seven years (2004, 2006-2011) at three different altitudes: low (630-660 m above sea level (ASL)), intermediate (720-750 m ASL), and high (1040-1070 m ASL). Tick abundance was highest at the lowest altitude and lowest at the highest altitude. The average infection prevalence of B. burgdorferi s.l. in nymphs and adults was 16.8% and 36.2%, respectively. The number of infected ticks decreased from 38.5% at the lowest altitude to 4.4% at the highest altitude. B. lusitaniae was the most frequently found genospecies (>60% of the ticks found positive for B. burgdorferi s.l.) in all sites in all the studied years with the exception of 2008 when B. afzelii predominated (62%). Our study confirms the spread of Ixodes ricinus ticks to higher altitudes in Slovakia. The discovery that our mountain study sites were a natural foci of B. lusitaniae was unexpected because this genospecies is usually associated with lizards and xerothermic habitats.

BGA66 and BGA71 facilitate complement resistance of Borrelia bavariensis by inhibiting assembly of the membrane attack complex

Borrelia (B.) bavariensis exhibits a marked tropism for nervous tissues and frequently causes neurological manifestations in humans. The molecular mechanism by which B. bavariensis overcomes innate immunity, in particular, complement remains elusive. In contrast to other serum-resistant spirochetes, none of the B. bavariensis isolates investigated bound complement regulators of the alternative (AP) and classical pathway (CP) or proteolytically inactivated complement components. Focusing on outer surface proteins BGA66 and BGA71, we demonstrated that both molecules either inhibit AP, CP and terminal pathway (TP) activation, or block activation of the CP and TP respectively. Both molecules bind complement components C7, C8 and C9, and thereby prevent assembly of the terminal complement complex. This inhibitory activity was confirmed by the introduction of the BGA66 and BGA71 encoding genes into a serum-sensitive B. garinii strain. Transformed spirochetes producing either BGA66 or BGA71 overcome complement-mediated killing, thus indicating that both proteins independently facilitate serum resistance of B. bavariensis. The generation of C-terminally truncated proteins as well as a chimeric BGA71 protein lead to the localization of the complement-interacting binding site within the N-terminus. Collectively, our data reveal a novel immune evasion strategy of B. bavariensis that is directed against the activation of the TP.

Public health impact of strain specific immunity to Borrelia burgdorferi

BACKGROUND

Lyme disease, caused by Borrelia burgdorferi, is the most common tick-borne infection in the United States. Although humans can be infected by at least 16 different strains of B. burgdorferi, the overwhelming majority of infections are due to only four strains. It was recently demonstrated that patients who are treated for early Lyme disease develop immunity to the specific strain of B. burgdorferi that caused their infection. The aim of this study is to estimate the reduction in cases of Lyme disease in the United States that may occur as a result of type specific immunity.

METHODS

The analysis was performed based on three analytical models that assessed the effects of type specific immunity. Observational data on the frequency with which different B. burgdorferi strains cause human infection in culture-confirmed patients with an initial episode of erythema migrans diagnosed between 1991 and 2005 in the Northeastern United States were used in the analyses.

RESULTS

Assuming a reinfection rate of 3 % and a total incidence of Lyme disease per year of 300,000, the estimated number of averted cases of Lyme disease per year ranges from 319 to 2378 depending on the duration of type specific immunity and the model used.

CONCLUSION

Given the assumptions of the analyses, this analysis suggests that type specific immunity is likely to have public health significance in the United States.

Lyme neuroborreliosis-epidemiology, diagnosis and management

Lyme disease, caused by the Borrelia burgdorferi bacterium, is the most common vector-borne disease in the northern hemisphere. The clinical presentation varies with disease stage, and neurological manifestations (often referred to as Lyme neuroborreliosis) are reported in up to 12% of patients with Lyme disease. Most aspects of the epidemiology, clinical manifestation and treatment of Lyme neuroborreliosis are well known and accepted; only the management of so-called chronic Lyme disease is surrounded by considerable controversy. This term is used for disparate patient groups, including those who have untreated late-stage infection (for example, late neuroborreliosis), those with subjective symptoms that persist after treatment (termed 'post-treatment Lyme disease syndrome' [PTLDS]), and those with unexplained subjective complaints that may or may not be accompanied by positive test results for B. burgdorferi infection in serum (here called 'chronic Lyme disease'). The incidence of PTLDS is still a matter of debate, and its pathogenesis is unclear, but there is evidence that these patients do not have ongoing B. burgdorferi infection and, thus, do not benefit from additional antibiotic therapy. Chronic Lyme disease lacks an accepted clinical definition, and most patients who receive this diagnosis have other illnesses. Thus, a careful diagnostic work-up is needed to ensure proper treatment.

RNA-Seq-based analysis of changes in Borrelia burgdorferi gene expression linked to pathogenicity

Background

Lyme disease is a global public health problem caused by the spirochaete Borrelia burgdorferi. Our previous studies found differences in disease severity between B. burgdorferi B31- and B. garinii SZ-infected mice. We hypothesized that genes that are differentially expressed between Borrelia isolates encode bacterial factors that contribute to disease diversity.

Methods

The present study used high-throughput sequencing technology to characterize and compare the transcriptional profiles of B. burgdorferi B31 and B. garinii SZ cultured in vitro. Real-time quantitative RT-PCR was used to validate selected data from RNA-seq experiments.

Results

A total of 731 genes were differentially expressed between B. burgdorferi B31 and B. garinii SZ isolates, including those encoding lipoproteins and purine transport proteins. The fold difference in expression for B. garinii SZ versus B. burgdorferi B31 ranged from 22.07 to 1.01. Expression of the OspA, OspB and DbpB genes were significantly lower in B. garinii SZ compared to B. burgdorferi B31.

Conclusions

The results support the hypothesis that global changes in gene expression underlie differences in Borrelia pathogenicity. The findings also provide an empirical basis for studying the mechanism of action of specific genes as well as their potential usefulness for the diagnosis and management of Lyme disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-014-0623-2) contains supplementary material, which is available to authorized users.

NGS population genetics analyses reveal divergent evolution of a Lyme Borreliosis agent in Europe and Asia

Borrelia bavariensis is a recently described agent of Lyme disease within the B. burgdorferi sensu lato species complex and exhibits a strong capacity for human pathogenicity. B. bavariensis strains are widely distributed in Eurasia spanning the distribution range of the tick vectors Ixodes persulcatus and I. ricinus. It has been suggested that B. bavariensis forms two populations, one of which arose through vector adaptation and geographic expansion. We have performed phylogenetic and population genetic analyses with next-generation sequencing data of 26 strains of B. bavariensis targeting the main linear chromosome and two plasmids (lp54, cp26). A very low number of single nucleotide polymorphisms (SNPs) was found in the European population and a deep branching pattern between European and Asian B. bavariensis was observed in all phylogenies. The results confirm the population structure of B. bavariensis and strongly support the hypothesis of clonal expansion of the European population of B. bavariensis. In addition, signals of positive selection identified in the populations further support the hypothesis that the European population of B. bavariensis likely underwent vector adaptation in its recent evolutionary history. Identified genes represent promising candidates for experimental vector adaptation studies. Thus, this species forms a very good model to study vector adaptation, which is known to play an important role in the geographic distribution of B. burgdorferi. Analysis of well known virulence determinants that are attributed to severity of clinical manifestation in B. burgdorferi s.s. revealed no variation within the European population of B. bavariensis, underlining the importance of including various Borrelia species into investigations that aim to understand the pathogenesis of Lyme disease agents.

Early cytokine release in response to live Borrelia burgdorferi Sensu Lato Spirochetes is largely complement independent

Aim

Here we investigated the role of complement activation in phagocytosis and the release of cytokines and chemokines in response to two clinical isolates: Borrelia afzelii K78, which is resistant to complement-mediated lysis, and Borrelia garinii LU59, which is complement-sensitive.

Methods

Borrelia spirochetes were incubated in hirudin plasma, or hirudin-anticoagulated whole blood. Complement activation was measured as the generation of C3a and sC5b-9. Binding of the complement components C3, factor H, C4, and C4BP to the bacterial surfaces was analyzed. The importance of complement activation on phagocytosis, and on the release of cytokines and chemokines, was investigated using inhibitors acting at different levels of the complement cascade.

Results

1) Borrelia garinii LU59 induced significantly higher complement activation than did Borrelia afzelii K78. 2) Borrelia afzelii K78 recruited higher amounts of factor H resulting in significantly lower C3 binding. 3) Both Borrelia strains were efficiently phagocytized by granulocytes and monocytes, with substantial inhibition by complement blockade at the levels of C3 and C5. 4) The release of the pro-inflammatory cytokines and chemokines IL-1β, IL-6, TNF, CCL20, and CXCL8, together with the anti-inflammatory IL-10, were increased the most (by>10-fold after exposure to Borrelia). 5) Both strains induced a similar release of cytokines and chemokines, which in contrast to the phagocytosis, was almost totally unaffected by complement blockade.

Conclusions

Our results show that complement activation plays an important role in the process of phagocytosis but not in the subsequent cytokine release in response to live Borrelia spirochetes.

Borrelia bavariensis sp. nov. is widely distributed in Europe and Asia

Since the original description of Borrelia bavariensis sp. nov. in 2009, additional samples available from humans and ticks from Europe and Mongolia, respectively, have been used to further characterize Borrelia strains belonging to this group of spirochaetes that utilize rodents as reservoir hosts. These investigations suggested the presence of related strains in Europe and Asia and confirmed their status as representing a distinct species. Furthermore, samples that were investigated by researchers from China and Japan confirm the ecological relationship of members of this proposed species with rodents and suggest that it has a wide distribution in Eurasia. Here, we use phylogenetic and genetic distance analyses to validate B. bavariensis sp. nov. as a species within the Borrelia burgdorferi sensu lato species complex. The type strain is PBiT ( = DSM 23469T = BAA-2496T).

Pathogenic analysis of Borrelia garinii strain SZ isolated from Northeastern China

Background

Various genospecies of Borrelia burgdorferi sensu lato (s.l.) have been identified from patients and animals worldwide. Genospecies-related dissemination of disease has been reported. The present study aimed to elucidate the pathogenicity of infections caused by B. garinii SZ isolated in China. B. burgdorferi B31 and B. afzelii BO23 were used for comparison.

Methods

Spirochete load in blood and tissue samples of infected mice were measured by minor groove binder-based real-time polymerase chain reaction. The kinetics of spirochete dissemination and disease severity were assessed in BALB/c mice.

Results

The pattern of bacterial load differed between the three genospecies. The B. garinii SZ strain is highly pathogenic and can trigger multi-system pathological damage in mice.

Conclusions

Spirochete dissemination, persistence, tissue tropism and disease severity varied significantly, suggesting that different genospecies may play an important role in the pathogenicity and development of clinical diseases.

CXCL13 may improve diagnosis in early neuroborreliosis with atypical laboratory findings

Background

Current guidelines regarding Lyme neuroborreliosis [LNB] require the presence of intrathecal Borrelia burgdorferi-specific antibody production for the definite diagnosis of LNB. However, about 20% of early stage infections present without an elevated antibody index. Moreover, intrathecal B. burgdorferi specific antibody synthesis may persist long after successful therapy of LNB. Recently published data indicate that CXCL13 seems to be a promising diagnostic tool for early stage LNB. In addition, CXCL13 might be suitable for treatment monitoring.

Case presentation

We report on a 39-year-old male patient from southern Germany, who has been suffering from subfebrile body temperatures and meningeal headache for six weeks. On the second day after hospital admission he developed peripheral palsy of the VII. cranial nerve. Cerebrospinal fluid (CSF) analysis showed granulocytic pleocytosis, elevated total protein and blood-CSF barrier dysfunction. Differential diagnostics for granulocytic pleocytosis were unremarkable. Only a second lumbar puncture, on day 6 after admission, revealed a lymphocytic pleocytosis. Serologic testing pointed to clear intrathecal Borrelia specific IgG antibody production. Interestingly, no anti-OspC antibodies were detectable. DNA of the rare Borrelia garinii OspA-type 7 could be amplified from the first CSF sample. The monitoring of CXCL13 in all CSF samples documented a fast decrease from 5000 pg/ml to 450 pg/ml after appropriate antibiotic treatment.

Conclusion

CXCL13 is a novel biomarker with high sensitivity and specificity for acute LNB. Our data show, that CXCL13 might be helpful in unclear cases and support the presumption that it might be a valuable tool for treatment monitoring. Anti-OspC antibody negativity is a rare observation, given the need of OspC for infection of the human hosts. Most likely this is due to a lack of sensitivity of OspC immunoblots that are unable to detect rare OspC variants.

Exploring gaps in our knowledge on Lyme borreliosis spirochaetes--updates on complex heterogeneity, ecology, and pathogenicity

The Lyme borreliosis complex is a heterogeneous group of tick-borne spirochaetes of the genus Borrelia (Spirochaetales: Spirochaetaceae) that are distributed all over the temperate zone of the northern hemisphere. Due to the usage of new methods for phylogenetic analysis, this group has expanded rapidly during the past 5 years. Along with this development, the number of Borrelia spp. regarded as pathogenic to humans also increased. Distribution areas as well as host and vector ranges of Lyme borreliosis agents turned out to be much wider than previously thought. Furthermore, there is evidence that ticks, reservoir hosts, and patients can be coinfected with multiple Borrelia spp. or other tick-borne pathogens, which indicates a need to establish new and well-defined diagnostic and therapeutic standards for Lyme borreliosis. This review gives a broad overview on the occurrence of Lyme borreliosis spirochaetes worldwide with particular emphasis on their vectors and vertebrate hosts as well as their pathogenic potential and resultant problems in diagnosis and treatment. Against the background that many issues regarding distribution, species identity, ecology, pathogenicity, and coinfections are still unsolved, the purpose of this article is to reveal directions for future research on the Lyme borreliosis complex.

Phylogeography of Lyme borreliosis-group spirochetes and methicillin-resistant Staphylococcus aureus

Multilocus sequence typing (MLST) and multilocus sequence analysis (MLSA) have revolutionized understanding the global epidemiology of many medically relevant bacteria utilizing a number, mostly seven, of housekeeping genes. A more recent introduction, single nucleotide polymorphisms (SNPs), constitutes an even more powerful tool for bacterial typing, population genetic studies and phylogeography. The introduction of massive parallel sequencing has made genome re-sequencing and SNP discovery more economical for investigations of microbial organisms. In this paper we review phylogeographic studies on Lyme borreliosis (LB)-group spirochetes and methicillin-resistant Staphylococcus aureus (MRSA). Members of the LB-group spirochetes are tick-transmitted zoonotic bacteria that have many hosts and differ in their degree of host specialism, constituting a highly complex system. MRSA is a directly transmitted pathogen that may be acquired by contact with infected people, animals or MRSA-contaminated objects. For the LB-group spirochetes, MLSA has proved a powerful tool for species assignment and phylogeographic investigations while for S. aureus, genome-wide SNP data have been used to study the very short-term evolution of two important MRSA lineages, ST239 and ST225. These data are detailed in this review.

Evaluation of molecular methods for detection of Borrelia burgdorferi senso lato in ticks

Borrelia burgdorferi sensu lato (s. l.), the agent of Lyme disease, is distributed widely worldwide. A large number of polymerase chain reaction (PCR) methods have been developed and used for detection of B. burgdorferi s. l. However, there is a lack of a reference standard because of the genetic diversity of the B. burgdorferi s. l. complex. In this study, 4 PCR methods, based on the OspA, flagellin, rrs, and P66 genes, for detection of B. burgdorferi s. l. were evaluated by detection of genomic DNA from 3 reference genospecies and tick samples. The sensitivity of the PCR methods was analyzed using serially diluted gDNA from B. afzelii (Bo23), B. burgdorferi sensu stricto (B31), and B. garinii (PBi). The performance of the PCRs was evaluated by detection of the gDNA of 543 ticks. The results showed that the PCRs targeting the OspA gene, fla gene, rrs gene, and P66 gene detected 37 (6.8%), 74 (13.6%), 16 (2.9%), and 14 (2.6%) tick samples, respectively. The PCR targeting the fla gene was the most sensitive method for the detection of B. burgdorferi s. l.

Population genetics, taxonomy, phylogeny and evolution of Borrelia burgdorferi sensu lato

In order to understand the population structure and dynamics of bacterial microorganisms, typing systems that accurately reflect the phylogenetic and evolutionary relationship of the agents are required. Over the past 15 years multilocus sequence typing schemes have replaced single locus approaches, giving novel insights into phylogenetic and evolutionary relationships of many bacterial species and facilitating taxonomy. Since 2004, several schemes using multiple loci have been developed to better understand the taxonomy, phylogeny and evolution of Lyme borreliosis spirochetes and in this paper we have reviewed and summarized the progress that has been made for this important group of vector-borne zoonotic bacteria.

Updates on Borrelia burgdorferi sensu lato complex with respect to public health

Borrelia burgdorferi sensu lato (s.l.) complex is a diverse group of worldwide distributed bacteria that includes 18 named spirochete species and a still not named group proposed as genomospecies 2. Descriptions of new species and variants continue to be recognized, so the current number of described species is probably not final. Most of known spirochete species are considered to have a limited distribution. Eleven species from the B. burgdorferi s.l. complex were identified in and strictly associated with Eurasia (B. afzelii, B. bavariensis, B. garinii, B. japonica, B. lusitaniae, B. sinica, B. spielmanii, B. tanukii, B. turdi, B. valaisiana, and B. yangtze), while another 5 (B. americana, B. andersonii, B. californiensis, B. carolinensis, and B. kurtenbachii) were previously believed to be restricted to the USA only. B. burgdorferi sensu stricto (s.s.), B. bissettii, and B. carolinensis share the distinction of being present in both the Old and the New World. Out of the 18 genospecies, 3 commonly and 4 occasionally infect humans, causing Lyme borreliosis (LB) - a multisystem disease that is often referred to as the 'great imitator' due to diversity of its clinical manifestations. Among the genospecies that commonly infect people, i.e. B. burgdorferi s.s., B. afzelii, and B. garinii, only B. burgdorferi s.s. causes LB both in the USA and in Europe, with a wide spectrum of clinical conditions ranging from minor cutaneous erythema migrans (EM) to severe arthritis or neurological manifestations. The epidemiological data from many European countries and the USA show a dramatic increase of the diagnosed cases of LB due to the development of new progressive diagnostic methods during the last decades (Hubálek, 2009). Recently, the definition of the disease has also changed. What was not considered Lyme borreliosis before might be now.

Identification and functional characterisation of Complement Regulator Acquiring Surface Protein-1 of serum resistant Borrelia garinii OspA serotype 4

Background

B. burgdorferi sensu lato (sl) is the etiological agent of Lyme borreliosis in humans. Spirochetes have adapted themselves to the human immune system in many distinct ways. One important immune escape mechanism for evading complement activation is the binding of complement regulators Factor H (CFH) or Factor H-like protein1 (FHL-1) to Complement Regulator-Acquiring Surface Proteins (CRASPs).

Results

We demonstrate that B. garinii OspA serotype 4 (ST4) PBi resist complement-mediated killing by binding of FHL-1. To identify the primary ligands of FHL-1 four CspA orthologs from B. garinii ST4 PBi were cloned and tested for binding to human CFH and FHL-1. Orthologs BGA66 and BGA71 were found to be able to bind both complement regulators but with different intensities. In addition, all CspA orthologs were tested for binding to mammalian and avian CFH. Distinct orthologs were able to bind to CFH of different animal origins.

Conclusions

B. garinii ST4 PBi is able to evade complement killing and it can bind FHL-1 to membrane expressed proteins. Recombinant proteins BGA66 can bind FHL-1 and human CFH, while BGA71 can bind only FHL-1. All recombinant CspA orthologs from B. garinii ST4 PBi can bind CFH from different animal origins. This partly explains the wide variety of animals that can be infected by B. garinii.

Borrelia burgdorferi sensu lato species in Europe induce diverse immune responses against C6 peptides in infected mice

The diversity of Lyme-borreliosis-inducing Borrelia species in Europe set high standards for the use of serodiagnostic test systems in terms of specificity and sensitivity. In the United States, the one-step C6 antibody test system based on the invariable domain IR6 of the VlsE molecule has been established as a successful diagnostic tool for testing canine samples. However, only a limited set of data are available regarding the antigenicity of the C6 peptides in an experimental murine model and sensitivity of the test regarding European Borrelia species. In order to investigate antibody reactions induced by these spirochetes, a total of 142 C3H/HeN mice were inoculated with Borrelia burgdorferi sensu stricto N40, B. garinii PBi, two isolates of B. afzelii, B. spielmanii A14S, B. valaisiana Rio6, B. valaisiana VS116, or B. lusitaniae. Infection of the mice was documented utilizing tissue culture and PCR. The IR6 sequences of B. burgdorferi sensu stricto B31, B. garinii IP90, and two B. afzelii ACAI strains have been used to synthesize and test additional C6 peptides. Compared to the well-established two-tiered test system, the results indicate that single C6 peptides derived from B. burgdorferi sensu stricto and B. garinii can be used in an enzyme-linked immunosorbent assay-based technique to detect murine antibodies induced by either agent. Little is known about the prevalence or pathogenicity of the B. afzelii strains in mammalian hosts, but our experimental data indicate differences in the C6 peptide test sensitivity for the detection of antibodies induced by different strains or isolates of B. afzelii.

A new Borrelia species defined by multilocus sequence analysis of housekeeping genes

Analysis of Lyme borreliosis (LB) spirochetes, using a novel multilocus sequence analysis scheme, revealed that OspA serotype 4 strains (a rodent-associated ecotype) of Borrelia garinii were sufficiently genetically distinct from bird-associated B. garinii strains to deserve species status. We suggest that OspA serotype 4 strains be raised to species status and named Borrelia bavariensis sp. nov. The rooted phylogenetic trees provide novel insights into the evolutionary history of LB spirochetes.

Lyme disease--current state of knowledge

BACKGROUND

Lyme disease is the most frequent tick-borne infectious disease in Europe. The discovery of the causative pathogen Borrelia burgdorferi in 1982 opened the way for the firm diagnosis of diseases in several clinical disciplines and for causal antibiotic therapy. At the same time, speculation regarding links between Borrelia infection and a variety of nonspecific symptoms and disorders resulted in overdiagnosis and overtreatment of suspected Lyme disease.

METHOD

The authors conducted a selective review of the literature, including various national and international guidelines.

RESULTS

The spirochete Borrelia burgdorferi sensu lato is present in approximately 5% to 35% of sheep ticks (Ixodes ricinus) in Germany, depending on the region. In contrast to North America, different genospecies are found in Europe. The most frequent clinical manifestation of Borrelia infection is erythema migrans, followed by neuroborreliosis, arthritis, acrodermatitis chronica atrophicans, and lymphocytosis benigna cutis. Diagnosis is made on the basis of the clinical symptoms, and in stages II and III by detection of Borrelia-specific antibodies. In adults erythema migrans is treated with doxycycline, in children with amoxicillin. The standard treatment of neuroborreliosis is third-generation cephalosporins.

CONCLUSIONS

After appropriate antibiotic therapy, the outcome is favorable. In approximately 95% of cases neuroborreliosis is cured without long-term sequelae. When chronic borreliosis is suspected, other potential causes of the clinical syndrome must be painstakingly excluded.

MLST of housekeeping genes captures geographic population structure and suggests a European origin of Borrelia burgdorferi

Lyme borreliosis, caused by the tick-borne bacterium Borrelia burgdorferi, has become the most common vector-borne disease in North America over the last three decades. To understand the dynamics of the epizootic spread and to predict the evolutionary trajectories of B. burgdorferi, accurate information on the population structure and the evolutionary relationships of the pathogen is crucial. We, therefore, developed a multilocus sequence typing (MLST) scheme for B. burgdorferi based on eight chromosomal housekeeping genes. We validated the MLST scheme on B. burgdorferi specimens from North America and Europe, comprising both cultured isolates and infected ticks. These data were compared with sequences for the commonly used genetic markers rrs-rrlA intergenic spacer (IGS) and the gene encoding the outer surface protein C (ospC). The study demonstrates that the concatenated sequences of the housekeeping genes of B. burgdorferi provide highly resolved phylogenetic signals and that the housekeeping genes evolve differently compared with the IGS locus and ospC. Using sequence data, the study reveals that North American and European populations of B. burgdorferi correspond to genetically distinct populations. Importantly, the MLST data suggest that B. burgdorferi originated in Europe rather than in North America as proposed previously.

Evaluation of a modified culture medium for Borrelia burgdorferi sensu lato

The aim of the present study was to assess the possible use of a modified medium, prepared in the laboratory using the constituents of Barbour-Stonner-Kelly (BSK) medium and medium 199 as base, for the culture of Borrelia strains, comparing the growth of individual strains in this medium and in the BSK-H medium, and the protein profile and antigenic characteristics of Borrelia proteins expressed in these media. A qualitative evaluation of growth of Borrelia species was made with acceptable results (morphology and motility), but during a quantitative evaluation using the three main genospecies of Borrelia, the better results were obtained with a B. burgdorferi sensu stricto strain. The modified medium did not enable the growth of a B. afzelii strain. The protein profile and antigenic characteristic of the expressed proteins in the modified medium were studied with satisfactory results. These results suggest the modified medium as an alternative for the cultivation of Borrelia strains, with some limitations, in poorly-resourced laboratories.

Population-based study of diagnostic assays for Borrelia infection: comparison of purified flagella antigen assay (Ideia, Dako Cytomation) and recombinant antigen assay (Liaison, DiaSorin)

Background

Testing for Borrelia-specific IgM and IgG-antibodies are often performed on a variety of poorly defined symptoms, and isolated IgM results are a frequent finding, which results in diagnostic uncertainty and further testing. We wanted to test the hypothesis that Borrelia-specific assays using recombinant antigens perform differently from assays based on purified flagella antigen.

Methods

We compared the use of recombinant antigens (LIAISON^® DiaSorin, Saluggia, Italy) and purified flagella antigen (IDEIA™ Borrelia, DakoCytomation, Glostrup, Denmark) in the assay for Borrelia-specific IgM and IgG-antibodies. The assays were tested on an unselected population of serum samples submitted from general practice. A total of 357 consecutive samples for analysis of Borrelia IgM and IgG antibodies. Furthermore, we analysed 540 samples for Borrelia-specific IgM or IgG antibodies first by the IDEIA™ and, if they were positive, the samples were further analysed using the LIAISON^® assay. To verify the correctness of the patient's serological status, discrepant samples were analysed by line blots (EcoLine, Virotech).

Results

In the consecutive series of 357 samples, the IgM assays detected 308 negative and 3 positive samples with concordant results. Compared with the line blot, the IDEIA™ system produced 21 false-positive IgM results, whereas the LIAISON^® system produced only one false-positive IgM result. The IgG assays showed 1 positive and 328 negative concordant results. The LIAISON^® system produced 9 true IgG-positive samples that were not detected by the IDEIA™ system, but the former produced 4 positive IgG results that were negative by line blot.

Conclusion

Diagnostic assays based on flagella antigen seem to show more false-positive IgM and false-negative IgG results than assays based on recombinant antigens. The latter may reduce the number of presumably false-positive IgM results and identify more IgG-positive subjects, but this system also produces more false-positive IgG results.

Larvae of chigger mites Neotrombicula spp. (Acari: Trombiculidae) exhibited Borrelia but no Anaplasma infections: a field study including birds from the Czech Carpathians as hosts of chiggers

Chigger mites were collected from 1,080 wild birds of 37 species at Certak (Czech Republic), in the western Carpathian Mountains, from 29 July to 24 September 2005. The prevalence of infestation with chigger larvae was 7%. A total of 325 chigger specimens from 10 bird species was identified and three chigger species were found: Neotrombicula autumnalis, N. carpathica, and N. inopinata, the latter two species being reported on new hosts. Neotrombicula carpathica is reported in the Czech Republic for the first time. A total of 509 chigger larvae found on 79 host specimens were examined by polymerase chain reaction (PCR) for the presence of Borrelia burgdorferi s.l. DNA (fragments of the rrf (5S)--rrl (23S) intergenic spacer), and Anaplasma phagocytophilum DNA (epank1 gene). A fragment of specific Borrelia DNA was amplified through PCR in one sample, and the PCR product was further analyzed by reverse line blotting assay, whereby both genospecies of B. garinii and B. valaisiana were proved. This sample pooled five chigger larvae collected from one Sylvia atricapilla on 11 August 2005. No A. phagocytophilum DNA was amplified. We conclude that larvae of the genus Neotrombicula can be infected with Borrelia genospecies originated from their present or former hosts.

Epidemiological aspects and molecular characterization of Borrelia burgdorferi s.l. from southern Germany with special respect to the new species Borrelia spielmanii sp. nov

In 475 Borrelia-infected Ixodes ricinus (2155 ticks investigated) from southern Germany the most common Borrelia burgdorferi sensu lato species was B. garinii (34.3%) followed by B. afzelii (25.1%), B. burgdorferi sensu stricto (22.0%), and B. valaisiana (12.7%). B. spielmanii sp. nov. was detected in 5.9% of the 475 infected ticks. Hints for a focal distribution were found for B. spielmanii sp. nov. and B. garinii OspA type 4. In 242 patient isolates, dominance (66.9%) of B. afzelii for skin could be confirmed, while frequency of B. garinii in cerebrospinal fluid (CSF) isolates (51.1%) was comparable to the frequency in nymphal ticks (51.6%). Four patient isolates from southern Germany and two from Slovenia, all isolated from erythema migrans, could be assigned to B. spielmanii sp. nov. Within this new species high sequence identities were found for rrs, fla, and ospA while rrf-rrl, ospC, and dbpA were less conserved: three new ospC and two new dbpA sequence types were found. This genetic heterogeneity reveals that B. spielmanii sp. nov. did not evolve just recently.

Borrelia burgdorferi VlsE antigen for the serological diagnosis of Lyme borreliosis

In this study, raising and development of antibody response to Borrelia burgdorferi infection in 66 Italian patients suffering from culture-confirmed Lyme borreliosis erythema migrans (EM) was investigated. Sixty-two of 66 cultures obtained from biopsies were identified as B. afzelii by PCR. A total of 175 serially collected serum samples were tested by using two different sets of commercial assays: Enzygnost Lyme link VlsE/IgG and Enzygnost Borreliosis IgM (DADE Behring, Marburg, Germany) and LIAISON Borrelia IgG and IgM (Diasorin, Saluggia, Italy). Considering only samples obtained at first presentation when EM was clinically evident, 49/66 patients (72.4%) were IgG or IgM positive by Enzygnost, whereas 33/66 (50.0%) patients were IgG or IgM positive by LIAISON. Taking into account the follow-up period, eight patients sero-converted for IgG or IgM by Enzygnost and four by LIAISON. Similar and very good specificity values were obtained by all methods. Testing sera obtained from blood donors (n = 300) and from patients suffering from some of the most common biological conditions possibly resulting in false-positive reactivity in Lyme disease serology (n = 100) showed that Enzygnost Lyme link VlsE/IgG was the more specific (98.3%), followed by LIAISON Borrelia IgG (96.5%), and considering IgM tests, Enzygnost Borreliosis IgM showed to be 95.3%% specific, whereas the LIAISON Borrelia IgM was 92.8% specific. Recombinant VlsE antigens obtained from all three B.burgdorferi genospecies pathogenic to humans (included in Enzygnost Lyme link VlsE/IgG) greatly improved serodiagnosis of Lyme disease.

Borrelia garinii induces CXCL13 production in human monocytes through Toll-like receptor 2

Recent studies have suggested an important role for the B-cell-attracting chemokine CXCL13 in the B-cell-dominated cerebrospinal fluid (CSF) infiltrate in patients with neuroborreliosis (NB). High levels of CXCL13 were present in the CSF of NB patients. It has not been clear, however, whether high CSF CXCL13 titers are specific for NB or are a characteristic of other spirochetal diseases as well. Furthermore, the mechanisms leading to the observed CXCL13 expression have not been identified yet. Here we describe similarly elevated CSF CXCL13 levels in patients with neurosyphilis, while pneumococcal meningitis patient CSF do not have high CXCL13 levels. In parallel, challenge of human monocytes in vitro with two of the spirochetal causative organisms, Borrelia garinii (the Borrelia species most frequently found in NB patients) and Treponema pallidum, but not challenge with pneumococci, induced CXCL13 release. This finding implies that a common spirochetal motif is a CXCL13 inducer. Accordingly, we found that the lipid moiety N-palmitoyl-S-(bis[palmitoyloxy]propyl)cystein (Pam(3)C) (three palmitoyl residues bound to N-terminal cysteine) of the spirochetal lipoproteins is critical for the CXCL13 induction in monocytes. As the Pam(3)C motif is known to signal via Toll-like receptor 2 (TLR2) and an anti-TLR2 monoclonal antibody blocked CXCL13 production of human monocytes incubated with B. garinii, this suggests that TLR2 is a major mediator of Borrelia-induced secretion of CXCL13 from human monocytes.

Microbiological and serological diagnosis of Lyme borreliosis

In Europe, Lyme borreliosis is caused by Borrelia burgdorferi sensu stricto, B. afzelii, B. garinii and the recently described species B. spielmanii. For the development of diagnostic tools, the heterogeneity of the causative agents must be considered. The serological diagnosis should follow the principle of a two-step procedure: a sensitive enzyme-linked immunosorbent analysis as the first step, followed by immunoblot (IgM and IgG) if reactive. The sensitivity and standardization of immunoblots have been enhanced by the use of recombinant antigens instead of whole cell lysates. Improved sensitivity has resulted from the use of recombinant proteins primarily expressed in vivo (e.g. VlsE) and the combination of homologous proteins from different strains (e.g. DbpA). At present, detection rates for serum antibodies are 20-50% in localized, 70-90% in disseminated early and nearly 100% in late disease. Detection of the borreliae by culture or PCR should be confined to specific indications. The best results are obtained from skin biopsies (50-70% with culture or PCR) and synovial tissue or fluid (50-70% with PCR). Cerebrospinal fluid is positive in only 10-30%. Methods that are not recommended for diagnostic purposes include antigen tests in body fluids, PCR of urine and lymphocyte transformation tests.

Complementation of a Borrelia afzelii OspC mutant highlights the crucial role of OspC for dissemination of Borrelia afzelii in Ixodes ricinus

Alteration of the outer surface protein (Osp) composition--especially that of OspA and OspC--seems to be important for the adaptation of Borrelia burgdorferi sensu lato to its endothermic hosts (mammals) and poikilothermic vectors (ticks). OspA possibly mediates adherence to tick midgut cells thus enabling the borreliae to survive in the vector, while OspC is associated with borrelial invasion of the tick salivary glands and infection of the mammalian hosts. Here we describe the first successful transformation and complementation of a Borrelia afzelii ospC mutant with the wild-type ospC in trans. To test the influence of OspC on the dissemination behavior in ticks, unfed Ixodes ricinus nymphs were artificially infected by capillary feeding either with B. afzelii wild type, the B. afzelii ospC mutant or the ospC-complemented clone. Tick midguts and salivary glands were investigated after different time intervals for the presence of borreliae and for OspA and OspC by immunfluorescence staining with monoclonal antibodies. While the B. afzelii wild-type strain exhibiting abundant OspC on its surface disseminated to the salivary glands, the OspC-negative mutant was only present in the tick midguts. The ospC-complemented clone which constitutively expresses the wild-type ospC was again able to colonize the salivary glands. This finding demonstrates that OspC is crucial for dissemination of B. afzelii from the tick midgut to the salivary glands, a prerequisite for infection of the warm-blooded host. A summary of the detailed data presented here has already been given in Goettner et al. [2006. OspC of B. afzelii is crucial for dissemination in the vector as shown by transformation and complementation of a European OspC-deficient B. afzelii strain. Int. J. Med. Microbiol. 296S1(Suppl. 40), 122-124].

Comparative genome analysis: selection pressure on the Borrelia vls cassettes is essential for infectivity

Background

At least three species of Borrelia burgdorferi sensu lato (Bbsl) cause tick-borne Lyme disease. Previous work including the genome analysis of B. burgdorferi B31 and B. garinii PBi suggested a highly variable plasmid part. The frequent occurrence of duplicated sequence stretches, the observed plasmid redundancy, as well as the mainly unknown function and variability of plasmid encoded genes rendered the relationships between plasmids within and between species largely unresolvable.

Results

To gain further insight into Borreliae genome properties we completed the plasmid sequences of B. garinii PBi, added the genome of a further species, B. afzelii PKo, to our analysis, and compared for both species the genomes of pathogenic and apathogenic strains.

The core of all Bbsl genomes consists of the chromosome and two plasmids collinear between all species. We also found additional groups of plasmids, which share large parts of their sequences. This makes it very likely that these plasmids are relatively stable and share common ancestors before the diversification of Borrelia species.

The analysis of the differences between B. garinii PBi and B. afzelii PKo genomes of low and high passages revealed that the loss of infectivity is accompanied in both species by a loss of similar genetic material. Whereas B. garinii PBi suffered only from the break-off of a plasmid end, B. afzelii PKo lost more material, probably an entire plasmid. In both cases the vls gene locus encoding for variable surface proteins is affected.

Conclusion

The complete genome sequences of a B. garinii and a B. afzelii strain facilitate further comparative studies within the genus Borrellia. Our study shows that loss of infectivity can be traced back to only one single event in B. garinii PBi: the loss of the vls cassettes possibly due to error prone gene conversion. Similar albeit extended losses in B. afzelii PKo support the hypothesis that infectivity of Borrelia species depends heavily on the evasion from the host response.

A decrease in the immunoglobulin G antibody response against the VlsE protein of Borrelia burgdorferi sensu lato correlates with the resolution of clinical signs in antibiotic-treated patients with early Lyme disease

The purpose of this study was to evaluate the diagnostic performance of the LIAISON Borrelia Screen (Diasorin, Saluggia, Italy), a new automated immunoassay based on the chemiluminescent technology (chemiluminescence immunoassay). To assess whether a decrease in a negative value in the anti-VlsE immunoglobulin G (IgG) antibody titer was correlated with a positive response to treatment, a group of serially collected serum samples from 67 patients with culture-confirmed erythema migrans was retrospectively studied. All the patients had been treated with antibiotics and were free of disease within 3 to 6 months of follow-up. All the 15 patients who were found to be IgG positive at the time of enrollment and who were bled at least four times during the follow-up became IgG seronegative at 2 to 6 months posttreatment. These results indicate that a decline in the anti-VlsE antibody titer coincides with effective antimicrobial therapy in patients with early localized Lyme disease.

Prevalence of Borrelia burgdorferi s.l. OspA types in Ixodes ricinus ticks from selected localities in Slovakia and Poland

In this study, 746 questing Ixodes (I.) ricinus ticks from eastern Slovakia and 187 ticks from southern Poland were investigated for infection with Borrelia (B.) burgdorferi sensu lato and different outer surface protein A (OspA) types by an improved restriction fragment length polymorphism (RFLP) analysis of the ospA gene. The method enables differentiation of both single and multiple infections with B. burgdorferi s.s. (OspA type 1), B. afzelii (OspA type 2), B. garinii (OspA types 3-8), B. valaisiana (subgroups I and II), B. lusitaniae, B. bissettii, and the recently described genospecies A14S. Broad heterogeneity in B. burgdorferi s.l. was found including all species and subtypes except for B. lusitaniae, B. bissettii, and genospecies A14S. Regional prevalence of B. burgdorferi s.l. varied between 8% and 22.5%. The most frequent species were B. garinii (45.4%) and, notably, B. burgdorferi s.s. (31.3%). I. ricinus nymphs harbored almost exclusively B. burgdorferi s.s. and B. garinii OspA type 4, while in adults a broad variety of B. burgdorferi s.l. types was found. Mixed infections were significantly more often in nymphs than in adult ticks. In all mixed infected nymphs, B. burgdorferi s.s. with OspA type 4 was present. These data strongly suggest that B. burgdorferi s.s. and B. garinii OspA type 4 are maintained in these areas by specific transmission cycles involving a so far undetermined vertebrate host which is frequently fed on by I. ricinus larvae. This improved method provides a reliable tool for epidemiological studies on the heterogeneity of B. burgdorferi species and OspA types, an important prerequisite for improved local risk assessment and for test- and vaccine development for Europe.

Molecular analysis of decorin-binding protein A (DbpA) reveals five major groups among European Borrelia burgdorferi sensu lato strains with impact for the development of serological assays and indicates lateral gene transfer of the dbpA gene

The Borrelia (B.) burgdorferi adhesin DbpA (decorin-binding protein A) is a valuable antigen for serodiagnosis of Lyme borreliosis and a promising candidate for a vaccine. To investigate the heterogeneity of DbpA, we aligned DNA sequences of 83 different dbpA genes (37 from the database, where the majority of sequences belong to B. burgdorferi sensu stricto and 46 were newly sequenced). Analysis of 25 sequences from the species B. burgdorferi s.s., 16 from B. afzelii, 40 from B. garinii, and two from the recently described human pathogenic genospecies A14S revealed five distinct DbpA groups. Group I comprises B. burgdorferi s.s. and group II B. afzelii. B. garinii is divided into groups III and IV, whereas A14S strains form group V. Formation of groups is mainly due to insertions of whole sequence sections. Comparison of dbpA sequences with ospC sequences from a subset of 59 strains revealed all kinds of cross-connections indicating processes of lateral gene transfer among strains. The extent of sequence identity within the dbpA genes decreases from the DNA (67%) to the amino acid (AA) level (44%) by about 23%, in contrast ospC sequence identities differed only by about 10%. This might be an indication that DbpA plays an important role in immune escape. Immunoblots using four recombinant DbpAs representing groups I-IV show that DbpA proteins are sensitive and specific antigens and complement one another in their reactivity. Part of the sera showed group-specific reactivity which could also be demonstrated with monoclonal antibodies.

Comparison of isolation rate of Borrelia burgdorferi sensu lato in MKP and BSK-II medium

Different media have been utilized for borrelial cultivation. The aim of the present study was to evaluate the isolation rate of Borrelia burgdorferi sensu lato from two commonly used media, i.e. modified Kelly-Pettenkofer (MKP) and Barbour-Stoenner-Kelly II (BSK-II) medium, and to compare the isolated strains with regard to their phenotypic and genotypic characteristics. Skin biopsy specimens of 2 x 2 x 4 mm were taken from the peripheral site of human solitary erythema lesions and were divided in two pieces, one of which was inoculated into MKP and the other one into BSK-II medium. Species analysis of the obtained strains was performed and their plasmid and protein profiles were determined. Borrelia strains were isolated from 48/96 patients (50%) with erythema migrans. We obtained in 26/48 patients (54%) from MKP as well as from BSK-II, in 11 patients (23%) only from MKP, and in another 11 (23%) only from BSK-II medium a positive result. B. afzelii was isolated from 43 patients (23 were positive in both media, nine in MKP only and 11 in BSK-II medium only), while B. garinii was isolated from five patients (in three from both media, in two from MKP only). All strains of the obtained strain pairs were identical according to species and the type within the species. Plasmid profiles were identical in 17/21 B. afzelii strain pairs (81%) and in 1/3 B. garinii strain pairs; in 6/24 strain pairs, distinctions in the number of plasmids or in their molecular mass were present. Differences in the protein profile were found in 7/24 strain pairs (29%). The distinctions were uniform and were limited to the expression of OspC. In conclusion, our study showed comparable Borrelia isolation rates from MKP and BSK-II medium. The results of the present study indicate that human patients with Lyme borreliosis may simultaneously harbor heterogeneous B. burgdorferi s.l. strains.

Adhesion of Borrelia garinii to neuronal cells is mediated by the interaction of OspA with proteoglycans

To study pathogenic mechanisms of Lyme meningoradiculitis, dorsal root ganglia (DRG) cells and two neuronal cell lines (B50, SH-SY5Y) were incubated with Borrelia garinii, the Borrelia species most frequently isolated from CSF of Lyme neuroborreliosis patients in Europe. We demonstrated that (I) OspA-positive B. garinii adhere to neuronal cells, (II) Borrelia adhesion can be blocked by a monoclonal antibody against OspA, (III) preincubation with proteoglycans interferes with the adhesion process and (IV) rOspA directly binds to the proteoglycans. This indicates that both OspA and the cell bound proteoglycans are involved in the attachment of B. garinii to neuronal cells.

Improvement of Lyme borreliosis serodiagnosis by a newly developed recombinant immunoglobulin G (IgG) and IgM line immunoblot assay and addition of VlsE and DbpA homologues

We developed and evaluated a recombinant Borrelia line immunoblot assay based on 18 homologues of seven different antigens, i.e., p100, p58, p41i, BmpA, VlsE, OspC, and DbpA. Each recombinant antigen can be detected separately and is distinct even from homologues with identical molecular weights. This blot was compared to the recently described recombinant Borrelia Western immunoblot assay (U. Schulte-Spechtel, G. Lehnert, G. Liegl, V. Fingerle, C. Heimerl, B. J. Johnson, and B. Wilske, J. Clin. Microbiol. 41:1299-1303, 2003). To verify sensitivity and specificity, both blots were evaluated for reactivity with Borrelia-specific immunoglobulin G (IgG) and IgM antibodies with 85 sera from patients with different manifestations of Lyme borreliosis and 110 controls. According to European interpretation criteria for Borrelia Western blots, which define a serum as positive when it recognizes at least two bands, sensitivity increased significantly from 70.6% (Western blot) to 84.7% (line blot) for IgG (P = 0.042) and from 40.0% (Western blot) to 73.8% (line blot) for IgM (P < 0.005). The increased sensitivity for IgG detection is due to the new line blot technique, whereas the improvement in detection of IgM is mainly achieved through incorporation of the additional antigens. Notably, the recombinant VlsE of Borrelia garinii strain PBi displayed the highest sensitivity of all antigens tested for IgG detection and is also one of the most useful antigens for IgM. Due to its excellent sensitivity and specificity combined with ease of evaluation, this line immunoblot assay offers a useful improvement in serodiagnosis of Lyme borreliosis.

Comparison of Borrelia burgdorferi sensu lato strains isolated from specimens obtained simultaneously from two different sites of infection in individual patients

The aim of the present study was to analyze and compare Borrelia strains isolated from two different specimens obtained simultaneously from individual patients with Lyme borreliosis. Fifty such patients and 50 corresponding pairs of Borrelia isolates (100 low-propagated strains) were subjected to genotypic and phenotypic analysis, including pulsed-field gel electrophoresis for species identification and plasmid profile determination and protein profile electrophoresis for the assessment of the presence and molecular masses of separated proteins. The strains were isolated from two distinct skin lesions (12 patients), skin and blood (28 patients), skin and cerebrospinal fluid (8 patients), and blood and cerebrospinal fluid (2 patients). Out of 100 isolates, 63 were typed as B. afzelii and 37 as B. garinii. From each individual specimen only a single Borrelia species was cultured. Comparison of 50 Borrelia strain pairs isolated from two different specimens of an individual patient revealed that 12/50 (24%) patients were simultaneously infected with two different Borrelia strains; in 3/50 (6%) patients strains differed at the species level, in 4 out of the remaining 47 (9%) patients a strain difference in plasmid profile was established, while 5 out of the remaining 43 (11%) patient strain pairs differed in regard to the protein profiles of the two concurrently isolated strains. The results of the present study indicate that human patients with Lyme borreliosis may simultaneously harbor different B. burgdorferi sensu lato strains.

Comparative evaluation of three different ELISA methods for the diagnosis of early culture-confirmed Lyme disease in Italy

In this study the raising and development of the immune response to Borrelia burgdorferi infection in 45 Italian patients suffering from culture-confirmed Lyme borreliosis erythema migrans was investigated. A total of 95 serially collected serum samples were tested by using three different commercial ELISAs: recomWell Borrelia (Mikrogen), Enzygnost Borreliosis (DADE Behring) and Quick ELISA C6 Borrelia (Immunetics). The sensitivities of the ELISAs were as follows: Enzygnost Borreliosis IgM, 70.5 %; Quick ELISA C6 Borrelia, 62.1 %; recomWell Borrelia IgM, 55.7 %; recomWell Borrelia IgG, 57.9 %; and Enzygnost Borreliosis IgG, 36.8 %. In order to compare the specificity values of the three ELISAs, a panel of sera obtained from blood donors (210 samples coming from a non-endemic area and 24 samples from an endemic area) was tested, as well as sera from patients suffering from some of the most common biological conditions that could result in false-positive reactivity in Lyme disease serology (n = 40). RecomWell Borrelia IgG and recomWell Borrelia IgM were the most specific (97.1 % and 98.9 %, respectively), followed by Quick ELISA C6 Borrelia (96.7 %). Enzygnost Borreliosis IgG and IgM achieved 90.1 % and 92.3 % specificity, respectively. Sera that gave discrepant results when tested by the three ELISAs were further analysed by Western blotting.

Lyme borreliosis in Europe and North America

Since the discovery of the Lyme disease spirochete in North America in 1982 and in Europe in 1983, a plethora of studies on this unique group of spirochetes that compriseBorrelia burgdorferisensu lato has been accumulated. In an attempt to compare and contrast Lyme borreliosis in Europe and North America we have reviewed the biology of the aetiologic agents, as well as the clinical aspects, diagnosis and treatment of this disease on both continents. Moreover, we have detailed the ecology of theIxodesticks that transmit this infection and the reservoir hosts that maintain the spirochete cycle in nature. Finally, we have examined the transmission dynamics of the spirochete on both continents, as well as the available prevention strategies. Although it has been over two decades since the discovery of the Lyme disease spirochete, Lyme borreliosis is an expanding public health problem that has defied our attempts to control it. By comparing the accumulated experience of investigators in North America and Europe, where the disease is most frequently reported, we hope to advance the cause of developing novel approaches to combat Lyme borreliosis.

Epidemiology and diagnosis of Lyme borreliosis

The multisystem disease Lyme borreliosis is the most frequent tick-transmitted disease in the northern hemisphere. In Europe Lyme borreliosis is most frequent in Central Europe and Scandinavia (up to 155 cases per 100,000 individuals) and is caused by the species, B. burgdorferi sensu stricto, B. afzelii and B. garinii. The recently detected genospecies A14S may also play a role in skin manifestations. Microbiological diagnosis in European patients must consider the heterogeneity of borreliae for development of diagnostic tools. According to guidelines of the USA and Germany, serological diagnosis should follow the principle of a two-step procedure (enzyme-linked immunosorbent assay (ELISA) as first step, if reactive; followed by immunoblot). The sensitivity and standardization of immunoblots has been considerably enhanced by use of recombinant antigens (p100, p58, p41i, VlsE, OspC, DbpA) including those expressed primarily in vivo (VlsE and DbpA) instead of whole cell lysates. VlsE is the most sensitive antigen for IgG antibody detection, OspC for IgM antibody detection. At present, detection rates for serum antibodies are 20%-50% in stage I, 70%-90% in stage II, and nearly 100% in stage III Lyme disease. Detection of the etiological agent by culture or polymerase chain reaction (PCR) should be confined to specific indications and specialized laboratories. Recommended specimens are skin biopsy specimens, cerebrospinal fluid (CSF) and synovial fluid. The best results are obtained from skin biopsies with culture or PCR (50%-70%) and synovial tissue or fluid (50%-70% with PCR). CSF yields positive results in only 10%-30% of patients except when the duration of symptoms is shorter than 2 weeks (50% sensitivity). Methods which are not recommended or adequately documented for diagnosis are antigen tests on body fluids, PCR of urine, and lymphocyte transformation tests.

Comparative analysis of the Borrelia garinii genome

Three members of the genus Borrelia (B.burgdorferi, B.garinii, B.afzelii) cause tick-borne borreliosis. Depending on the Borrelia species involved, the borreliosis differs in its clinical symptoms. Comparative genomics opens up a way to elucidate the underlying differences in Borrelia species. We analysed a low redundancy whole-genome shotgun (WGS) assembly of a B.garinii strain isolated from a patient with neuroborreliosis in comparison to the B.burgdorferi genome. This analysis reveals that most of the chromosome is conserved (92.7% identity on DNA as well as on amino acid level) in the two species, and no chromosomal rearrangement or larger insertions/deletions could be observed. Furthermore, two collinear plasmids (lp54 and cp26) seem to belong to the basic genome inventory of Borrelia species. These three collinear parts of the Borrelia genome encode 861 genes, which are orthologous in the two species examined. The majority of the genetic information of the other plasmids of B.burgdorferii is also present in B.garinii although orthology is not easy to define due to a high redundancy of the plasmid fraction. Yet, we did not find counterparts of the B.burgdorferi plasmids lp36 and lp38 or their respective gene repertoire in the B.garinii genome. Thus, phenotypic differences between the two species could be attributable to the presence or absence of these two plasmids as well as to the potentially positively selected genes.