Frequency and factors associated of potential zoonotic pathogens (Borrelia spp., Rickettsia spp., Leishmania spp., and Anaplasma phagocytophilum) in equids in the state of Bahia, Brazil

BACKGROUND

Currently, various zoonotic diseases are classified as emerging or reemerging. Because equids have a direct relationship with various vectors, they are possibly more frequently exposed to zoonotic agents than are humans. The undeniable importance of diseases such as human granulocytic anaplasmosis, spotted fever, and leishmaniasis for both public and animal health, as well as the possibility of equids acting as sources, reservoirs, or even sentinels for these pathogens, justifies the detection of their frequency and factors associated with infection in equids from northeastern Brazil.

METHODS

Blood samples were collected from 569 equids (528 horses, 33 donkeys, and 8 mules), 516 from a rural area and 53 from an urban area. Pathogen detection was carried out as follows: Borrelia spp. and Rickettsia spp., serological analysis; Leishmania spp., serological analysis and polymerase chain reaction (PCR); Anaplasma phagocytophilum, PCR. Determination of associated factors was carried out through generalized linear models.

RESULTS

The frequencies of positivity for the pathogens observed in equids were as follows: Borrelia spp., 13.9% (79/569); Leishmania spp., 3.5% (20/569); Rickettsia spp. 33.4% (190/569). Regarding factors associated with infection, male sex was associated with protection against Borrelia spp.; donkeys and mules were associated with protection against Rickettsia spp., while a younger age was a risk factor. The infection of A. phagocytophilum was not detected in the sampled population. Co-infection was detected in 5.1% (29/569) of the animals.

CONCLUSIONS

Most of the studied pathogenic agents are present in the prospected area, indicating a possible risk for both human and animal health. This demonstrates that equids can be considered important sentinels in the assessment of pathogens with zoonotic potential in the region.

Borrelia burgdorferi and Borrelia miyamotoi seroprevalence in California blood donors

The western blacklegged tick, Ixodes pacificus, an important vector in the western United States of two zoonotic spirochetes: Borrelia burgdorferi (also called Borreliella burgdorferi), causing Lyme disease, and Borrelia miyamotoi, causing a relapsing fever-type illness. Human cases of Lyme disease are well-documented in California, with increased risk in the north coastal areas and western slopes of the Sierra Nevada range. Despite the established presence of B. miyamotoi in the human-biting I. pacificus tick in California, clinical cases with this spirochete have not been well studied. To assess exposure to B. burgdorferi and B. miyamotoi in California, and to address the hypothesis that B. miyamotoi exposure in humans is similar in geographic range to B. burgdorferi, 1,700 blood donor sera from California were tested for antibodies to both pathogens. Sampling was from high endemic and low endemic counties for Lyme disease in California. All sera were screened using the C6 ELISA. All C6 positive and equivocal samples and nine randomly chosen C6 negative samples were further analyzed for B. burgdorferi antibody using IgG western blot and a modified two ELISA test system and for B. miyamotoi antibody using the GlpQ ELISA and B. miyamotoi whole cell sonicate western blot. Of the 1,700 samples tested in series, eight tested positive for antibodies to B. burgdorferi (0.47%, Exact 95% CI: 0.20, 0.93) and two tested positive for antibodies to B. miyamotoi (0.12%, Exact 95% CI: 0.01, 0.42). There was no statistically significant difference in seroprevalence for either pathogen between high and low Lyme disease endemic counties. Our results confirm a low frequency of Lyme disease and an even lower frequency of B. miyamotoi exposure among adult blood donors in California; however, our findings reinforce public health messaging that there is risk of infection by these emerging diseases in the state.

The impact of in vitro cultivation on the natural life cycle of the tick-borne relapsing fever spirochete Borrelia turicatae

Tick-borne relapsing fever is an infectious disease caused by Borrelia species and are primarily transmitted by Ornithodoros ticks. Prior work indicated that in vitro cultivated spirochetes remain infectious to mice by needle inoculation; however, the impact of laboratory propagation on the pathogens natural life cycle has not been determined. Our current study assessed the effect of serial cultivation on the natural tick-mammalian transmission cycle. First, we evaluated genomic DNA profiles from B. turicatae grown to 30, 60, 120, and 300 generations, and these spirochetes were used to needle inoculate mice. Uninfected nymphal ticks were fed on these mice and acquisition, transstadial maintenance, and subsequent transmission after tick bite was determined. Infection frequencies in mice that were fed upon by ticks colonized with B. turicatae grown to 30, 60, and 120 generations were 100%, 100%, and 30%, respectively. Successful infection of mice by tick feeding was not detected after 120 generations. Quantifying B. turicatae in tick tissues indicated that by 300 generations they no longer colonized the vector. The results indicate that in vitro cultivation significantly affects the establishment of tick colonization and murine infection. This work provides a foundation for the identification of essential genetic elements in the tick-mammalian infectious cycle.

Lyme disease and relapsing fever in Mexico: An overview of human and wildlife infections

Lyme borreliosis and Relapsing fever are considered emerging and re-emerging diseases that cause major public health problems in endemic countries. Epidemiology and geographical distribution of these diseases are documented in the US and in Europe, yet in Mexico, studies are scarce and scattered. The aims of this study were (1) to present the first confirmatory evidence of an endemic case of Lyme disease in Mexico and (2) to analyze the epidemiological trend of these both diseases by compiling all the information published on Borrelia in Mexico. Two databases were compiled, one of human cases and another of wild and domestic animals in the country. The analysis included the evaluation of risk factors for the human population, the diversity of Borrelia species and their geographic distribution. Six Borrelia species were reported in a total of 1,347 reports, of which 398 were of humans. Women and children from rural communities were shown to be more susceptible for both Lyme borreliosis and Relapsing fever. The remaining reports were made in diverse mammalian species and ticks. A total of 17 mammalian species and 14 tick species were recorded as hosts for this bacterial genus. It is noteworthy that records of Borrelia were only made in 18 of the 32 states, mainly in northern and central Mexico. These results highlight the importance of performing further studies in areas where animal cases have been reported, yet no human studies have been done, in order to complete the epidemiological panorama for Lyme borreliosis and Relapsing fever. Finally, the search for Borrelia infections in other vertebrates, such as reptiles and amphibians is recommended to gain a more accurate view of Borrelia species and their distribution. The geographical approach presented herein justifies an intense sampling effort to improve epidemiological knowledge of these diseases to aid vector control and prevention programs.

Factors affecting the microbiome of Ixodes scapularis and Amblyomma americanum

The microbial community composition of disease vectors can impact pathogen establishment and transmission as well as on vector behavior and fitness. While data on vector microbiota are accumulating quickly, determinants of the variation in disease vector microbial communities are incompletely understood. We explored the microbiome of two human-biting tick species abundant in eastern North America (Amblyomma americanum and Ixodes scapularis) to identify the relative contribution of tick species, tick life stage, tick sex, environmental context and vertical transmission to the richness, diversity, and species composition of the tick microbiome. We sampled 89 adult and nymphal Ixodes scapularis (N = 49) and Amblyomma americanum (N = 40) from two field sites and characterized the microbiome of each individual using the v3-v4 hypervariable region of the 16S rRNA gene. We identified significant variation in microbial community composition due to tick species and life stage with lesser impact of sampling site. Compared to unfed nymphs and males, the microbiome of engorged adult female I. scapularis, as well as the egg masses they produced, were low in bacterial richness and diversity and were dominated by Rickettsia, suggesting strong vertical transmission of this genus. Likewise, microbiota of A. americanum nymphs and males were more diverse than those of adult females. Among bacteria of public health importance, we detected several different Rickettsia sequence types, several of which were distinct from known species. Borrelia was relatively common in I. scapularis but did not show the same level of sequence variation as Rickettsia. Several bacterial genera were significantly over-represented in Borrelia-infected I. scapularis, suggesting a potential interaction of facilitative relationship between these taxa; no OTUs were under-represented in Borrelia-infected ticks. The systematic sampling we conducted for this study allowed us to partition the variation in tick microbial composition as a function of tick- and environmentally-related factors. Upon more complete understanding of the forces that shape the tick microbiome it will be possible to design targeted experimental studies to test the impacts of individual taxa and suites of microbes on vector-borne pathogen transmission and on vector biology.

Comparison of tick-borne pathogen prevalence in Ixodes ricinus ticks collected in urban areas of Europe

Tick-borne diseases are a major threat to human and animal health. An increasing number of natural habitats have been transformed into urban areas by human activity; hence, the number of reported tick bites in urban and suburban areas has risen. This retrospective analysis evaluated 53 scientific reports concerning infections of Ixodes ricinus ticks collected from urban and suburban areas of Europe between 1991 and 2017. The results indicate significant differences in many variables, including a higher number of Anaplasma phagocytophilum infections in Eastern Europe than in Western Europe. The opposite result was observed for Candidatus Neoehrlichia mikurensis infections. A comparison of climate zones revealed that Borrelia burgdorferi s.l. infections have the greatest median incidence rate in subtropical climate zones. No statistical significance was found when comparing other tick-borne pathogens (TBPs), such as Borrelia miyamotoi, Rickettsia spp., Babesia spp., Bartonella spp., Ehrlichia spp., Coxiella burnetii and Francisella tularensis. The analysis also showed significant differences in the overall prevalence of TBPs according to average temperatures and rainfall across Europe. This retrospective study contributes to the knowledge on the occurrence and prevalence of TBPs in urbanized areas of Europe and their dependence on the habitats and geographical distributions of ticks. Due to the increased risk of tick bites, it is of great importance to investigate infections in ticks from urban and suburban areas.

Neuroborreliosis and Neurosyphilis

PURPOSE OF REVIEW

This article presents an overview of the current diagnosis and management of two spirochetal infections of the nervous system, neuroborreliosis (Lyme disease) and neurosyphilis, focusing on similarities and differences. Although neuroborreliosis was first identified almost a century ago, much confusion remains about how to accurately diagnose this quite treatable nervous system infection. Well-established diagnostic tools and therapeutic regimens exist for neurosyphilis, which has been well-known for centuries.

RECENT FINDINGS

Serologic testing targeting the C6 antigen may simplify diagnostic testing in neuroborreliosis while improving accuracy. Historically, screening for syphilis has used a reaginic test followed by a treponeme-specific assay; alternative approaches, including use of well-defined recombinant antigens, may improve sensitivity without sacrificing specificity. In neuroborreliosis, measurement of the chemokine CXCL13 in CSF may provide a useful marker of disease activity in the central nervous system.

SUMMARY

Lyme disease causes meningitis, cranial neuritis, radiculitis, and mononeuropathy multiplex. Cognitive symptoms, occurring either during (encephalopathy) or after infection (posttreatment Lyme disease syndrome) are rarely, if ever, due to central nervous system infection. Posttreatment Lyme disease syndrome is not antibiotic responsive. Syphilis causes meningitis, cranial neuritis, chronic meningovascular syphilis, tabes dorsalis, and parenchymal neurosyphilis. The organism remains highly sensitive to penicillin, but residua of chronic infection may be irreversible.

Genomic blueprint of a relapsing fever pathogen in 15th century Scandinavia

Louse-borne relapsing fever (LBRF) is known to have killed millions of people over the course of European history and remains a major cause of mortality in parts of the world. Its pathogen, Borrelia recurrentis, shares a common vector with global killers such as typhus and plague and is known for its involvement in devastating historical epidemics such as the Irish potato famine. Here, we describe a European and historical genome of Brecurrentis, recovered from a 15th century skeleton from Oslo. Our distinct European lineage has a discrete genomic makeup, displaying an ancestral oppA-1 gene and gene loss in antigenic variation sites. Our results illustrate the potential of ancient DNA research to elucidate dynamics of reductive evolution in a specialized human pathogen and to uncover aspects of human health usually invisible to the archaeological record.

Pathogen transmission in relation to duration of attachment by Ixodes scapularis ticks

The blacklegged tick, Ixodes scapularis, is the primary vector to humans in the eastern United States of the deer tick virus lineage of Powassan virus (Powassan virus disease); the protozoan parasite Babesia microti (babesiosis); and multiple bacterial disease agents including Anaplasma phagocytophilum (anaplasmosis), Borrelia burgdorferi and Borrelia mayonii (Lyme disease), Borrelia miyamotoi (relapsing fever-like illness, named Borrelia miyamotoi disease), and Ehrlichia muris eauclairensis (a minor causative agent of ehrlichiosis). With the notable exception of Powassan virus, which can be transmitted within minutes after attachment by an infected tick, there is no doubt that the risk of transmission of other I. scapularis-borne pathogens, including Lyme disease spirochetes, increases with the length of time (number of days) infected ticks are allowed to remain attached. This review summarizes data from experimental transmission studies to reinforce the important disease-prevention message that regular (at least daily) tick checks and prompt tick removal has strong potential to reduce the risk of transmission of I. scapularis-borne bacterial and parasitic pathogens from infected attached ticks. The most likely scenario for human exposure to an I. scapularis-borne pathogen is the bite by a single infected tick. However, recent reviews have failed to make a clear distinction between data based on transmission studies where experimental hosts were fed upon by a single versus multiple infected ticks. A summary of data from experimental studies on transmission of Lyme disease spirochetes (Bo. burgdorferi and Bo. mayonii) by I. scapularis nymphs indicates that the probability of transmission resulting in host infection, at time points from 24 to 72 h after nymphal attachment, is higher when multiple infected ticks feed together as compared to feeding by a single infected tick. In the specific context of risk for human infection, the most relevant experimental studies therefore are those where the probability of pathogen transmission at a given point in time after attachment was determined using a single infected tick. The minimum duration of attachment by single infected I. scapularis nymphs required for transmission to result in host infection is poorly defined for most pathogens, but experimental studies have shown that Powassan virus can be transmitted within 15 min of tick attachment and both A. phagocytophilum and Bo. miyamotoi within the first 24 h of attachment. There is no experimental evidence for transmission of Lyme disease spirochetes by single infected I. scapularis nymphs to result in host infection when ticks are attached for only 24 h (despite exposure of nearly 90 experimental rodent hosts across multiple studies) but the probability of transmission resulting in host infection appears to increase to approximately 10% by 48 h and reach 70% by 72 h for Bo. burgdorferi. Caveats to the results from experimental transmission studies, including specific circumstances (such as re-attachment of previously partially fed infected ticks) that may lead to more rapid transmission are discussed.

Epidemiological study of relapsing fever borreliae detected in Haemaphysalis ticks and wild animals in the western part of Japan

The genus Borrelia comprises arthropod-borne bacteria, which are infectious agents in vertebrates. They are mainly transmitted by ixodid or argasid ticks. In Hokkaido, Japan, Borrelia spp. were found in deer and Haemaphysalis ticks between 2011 and 2013; however, the study was limited to a particular area. Therefore, in the present study, we conducted large-scale surveillance of ticks and wild animals in the western part of the main island of Japan. We collected 6,407 host-seeking ticks from two regions and 1,598 larvae obtained from 32 engorged female ticks and examined them to elucidate transovarial transmission. In addition, we examined whole blood samples from 190 wild boars and 276 sika deer, as well as sera from 120 wild raccoons. We detected Borrelia spp. in Haemaphysalis flava, Haemaphysalis megaspinosa, Haemaphysalis kitaokai, Haemaphysalis longicornis, and Haemaphysalis formosensis. In addition, we isolated a strain from H. megaspinosa using Barbour-Stoenner-Kelly medium. The minimum infection rate of ticks was less than 5%. Transovarial transmission was observed in H. kitaokai. Phylogenetic analysis of the isolated strain and DNA fragments amplified from ticks identified at least four bacterial genotypes, which corresponded to the tick species detected. Bacteria were detected in 8.4%, 15%, and 0.8% of wild boars, sika deer, and raccoons, respectively. In this study, we found seasonal differences in the prevalence of bacterial genotypes in sika deer during the winter and summer. The tick activity season corresponds to the season with a high prevalence of animals. The present study suggests that a particular bacterial genotype detected in this study are defined by a particular tick species in which they are present.

Characterization of a DNA Adenine Methyltransferase Gene of Borrelia hermsii and Its Dispensability for Murine Infection and Persistence

DNA methyltransferases have been implicated in the regulation of virulence genes in a number of pathogens. Relapsing fever Borrelia species harbor a conserved, putative DNA methyltransferase gene on their chromosome, while no such ortholog can be found in the annotated genome of the Lyme disease agent, Borrelia burgdorferi. In the relapsing fever species Borrelia hermsii, the locus bh0463A encodes this putative DNA adenine methyltransferase (dam). To verify the function of the BH0463A protein product as a Dam, the gene was cloned into a Dam-deficient strain of Escherichia coli. Restriction fragment analysis subsequently demonstrated that complementation of this E. coli mutant with bh0463A restored adenine methylation, verifying bh0463A as a Dam. The requirement of bh0463A for B. hermsii viability, infectivity, and persistence was then investigated by genetically disrupting the gene. The dam^- mutant was capable of infecting immunocompetent mice, and the mean level of spirochetemia in immunocompetent mice was not significantly different from wild type B. hermsii. Collectively, the data indicate that dam is dispensable for B. hermsii viability, infectivity, and persistence.

Borrelia crocidurae in Ornithodoros ticks from northwestern Morocco: a range extension in relation to climatic change?

Tick-borne relapsing fever (TBRF) is caused by Borrelia spirochetes transmitted to humans by Argasid soft ticks of the genus Ornithodoros. We investigated the presence of Ornithodoros ticks in rodent burrows in nine sites of the Gharb region of northwestern Morocco where we recently documented a high incidence of TBRF in humans. We assessed the Borrelia infection rate by nested PCR and sequencing. All sites investigated were colonized by ticks of the Ornithodoros marocanus complex and a high proportion of burrows (38.4%) were found to be infested. Borrelia infections were observed in 6.8% of the ticks tested. Two Borrelia species were identified by sequencing: B. hispanica and B. crocidurae. The discovery in northwestern Morocco of Ornithodoros ticks infected by B. crocidurae represents a 350 km range extension of this Sahelo-Saharan spirochete in North Africa. The spread of B. crocidurae may be related to the increasing aridity of northwestern Morocco in relation to climate change.

Inactivation of genes for antigenic variation in the relapsing fever spirochete Borrelia hermsii reduces infectivity in mice and transmission by ticks

Borrelia hermsii, a causative agent of relapsing fever of humans in western North America, is maintained in enzootic cycles that include small mammals and the tick vector Ornithodoros hermsi. In mammals, the spirochetes repeatedly evade the host's acquired immune response by undergoing antigenic variation of the variable major proteins (Vmps) produced on their outer surface. This mechanism prolongs spirochete circulation in blood, which increases the potential for acquisition by fast-feeding ticks and therefore perpetuation of the spirochete in nature. Antigenic variation also underlies the relapsing disease observed when humans are infected. However, most spirochetes switch off the bloodstream Vmp and produce a different outer surface protein, the variable tick protein (Vtp), during persistent infection in the tick salivary glands. Thus the production of Vmps in mammalian blood versus Vtp in ticks is a dominant feature of the spirochete's alternating life cycle. We constructed two mutants, one which was unable to produce a Vmp and the other was unable to produce Vtp. The mutant lacking a Vmp constitutively produced Vtp, was attenuated in mice, produced lower cell densities in blood, and was unable to relapse in animals after its initial spirochetemia. This mutant also colonized ticks and was infectious by tick-bite, but remained attenuated compared to wild-type and reconstituted spirochetes. The mutant lacking Vtp also colonized ticks but produced neither Vtp nor a Vmp in tick salivary glands, which rendered the spirochete noninfectious by tick bite. Thus the ability of B. hermsii to produce Vmps prolonged its survival in blood, while the synthesis of Vtp was essential for mammalian infection by the bite of its tick vector.

The epidemiology and geographic distribution of relapsing fever borreliosis in West and North Africa, with a review of the Ornithodoros erraticus complex (Acari: Ixodida)

BACKGROUND

Relapsing fever is the most frequent bacterial disease in Africa. Four main vector / pathogen complexes are classically recognized, with the louse Pediculus humanus acting as vector for B. recurrentis and the soft ticks Ornithodoros sonrai, O. erraticus and O. moubata acting as vectors for Borrelia crocidurae, B. hispanica and B. duttonii, respectively. Our aim was to investigate the epidemiology of the disease in West, North and Central Africa.

METHODS AND FINDINGS

From 2002 to 2012, we conducted field surveys in 17 African countries and in Spain. We investigated the occurrence of Ornithodoros ticks in rodent burrows in 282 study sites. We collected 1,629 small mammals that may act as reservoir for Borrelia infections. Using molecular methods we studied genetic diversity among Ornithodoros ticks and Borrelia infections in ticks and small mammals. Of 9,870 burrows investigated, 1,196 (12.1%) were inhabited by Ornithodoros ticks. In West Africa, the southern and eastern limits of the vectors and Borrelia infections in ticks and small mammals were 13°N and 01°E, respectively. Molecular studies revealed the occurrence of nine different Ornithodoros species, including five species new for science, with six of them harboring Borrelia infections. Only B. crocidurae was found in West Africa and three Borrelia species were identified in North Africa: B. crocidurae, B. hispanica, and B. merionesi.

CONCLUSIONS

Borrelia Spirochetes responsible for relapsing fever in humans are highly prevalent both in Ornithodoros ticks and small mammals in North and West Africa but Ornithodoros ticks seem absent south of 13°N and small mammals are not infected in these regions. The number of Ornithodoros species acting as vector of relapsing fever is much higher than previously known.

Periplasmic flagellar export apparatus protein, FliH, is involved in post-transcriptional regulation of FlaB, motility and virulence of the relapsing fever spirochete Borrelia hermsii

Spirochetes are bacteria characterized in part by rotating periplasmic flagella that impart their helical or flat-wave morphology and motility. While most other bacteria rely on a transcriptional cascade to regulate the expression of motility genes, spirochetes employ post-transcriptional mechanism(s) that are only partially known. In the present study, we characterize a spontaneous non-motile mutant of the relapsing fever spirochete Borrelia hermsii that was straight, non-motile and deficient in periplasmic flagella. We used next generation DNA sequencing of the mutant's genome, which when compared to the wild-type genome identified a 142 bp deletion in the chromosomal gene encoding the flagellar export apparatus protein FliH. Immunoblot and transcription analyses showed that the mutant phenotype was linked to the posttranscriptional deficiency in the synthesis of the major periplasmic flagellar filament core protein FlaB. Despite the lack of FlaB, the amount of FlaA produced by the fliH mutant was similar to the wild-type level. The turnover of the residual pool of FlaB produced by the fliH mutant was comparable to the wild-type spirochete. The non-motile mutant was not infectious in mice and its inoculation did not induce an antibody response. Trans-complementation of the mutant with an intact fliH gene restored the synthesis of FlaB, a normal morphology, motility and infectivity in mice. Therefore, we propose that the flagellar export apparatus protein regulates motility of B. hermsii at the post-transcriptional level by influencing the synthesis of FlaB.

A prospective study among patients presenting at the general practitioner with a tick bite or erythema migrans in The Netherlands

Background

We performed a nationwide prospective study on the transmission risk for Borrelia to humans, investigating symptoms and serology at enrolment and three months after tick bites, and after standard treatment for erythema migrans (EM). Aiming to quantify the infection risk at point of care by physicians, we explored risk factors such as tick testing for Borrelia and assessment of the duration of the tick's blood meal.

Methods and Findings

Questionnaires, blood samples and ticks from patients who consulted one of 307 general practitioners for tick bites (n = 327) or EM (n = 283) in 2007 and 2008, were collected at enrolment and three months later at follow-up. Borrelia burgdorferi sensu lato DNA was detected in 29.3% of 314 ticks, using PCR/reverse line blot and real-time PCR on the OspA gene. Seroconversion in C6 ELISA, IgM or IgG immunoblots for Borrelia-specific antibodies was observed in 3.2% of tick bite cases. Fourteen tick bite cases had evidence of early Borrelia infection, of which EM developed among seven cases. The risk of developing EM after tick bites was 2.6% (95%CI: 1.1%–5.0%), and the risk of either EM or seroconversion was 5.1% (95%CI: 2.9%–8.2%). Participants with Borrelia-positive ticks had a significantly higher risk of either EM or seroconversion (odds ratio 4.8, 95%CI: 1.1–20.4), and of seroconversion alone (odds ratio 11.1, 95%CI: 1.1–108.9). A third (34%) of the cases enrolled with EM did not recall preceding tick bites. Three EM cases (1%) reported persisting symptoms, three months after standard antibiotic treatment for EM.

Conclusions

One out of forty participants developed EM within three months after tick bites. The infection risk can be assessed by tick testing for Borrelia at point of care by physicians. However, further refining is needed considering sensitivity and specificity of tick tests, accuracy of tick attachment time and engorgement.

Microbes bind complement inhibitor factor H via a common site

To cause infections microbes need to evade host defense systems, one of these being the evolutionarily old and important arm of innate immunity, the alternative pathway of complement. It can attack all kinds of targets and is tightly controlled in plasma and on host cells by plasma complement regulator factor H (FH). FH binds simultaneously to host cell surface structures such as heparin or glycosaminoglycans via domain 20 and to the main complement opsonin C3b via domain 19. Many pathogenic microbes protect themselves from complement by recruiting host FH. We analyzed how and why different microbes bind FH via domains 19–20 (FH19-20). We used a selection of FH19-20 point mutants to reveal the binding sites of several microbial proteins and whole microbes (Haemophilus influenzae, Bordetella pertussis, Pseudomonas aeruginosa, Streptococcus pneumonia, Candida albicans, Borrelia burgdorferi, and Borrelia hermsii). We show that all studied microbes use the same binding region located on one side of domain 20. Binding of FH to the microbial proteins was inhibited with heparin showing that the common microbial binding site overlaps with the heparin site needed for efficient binding of FH to host cells. Surprisingly, the microbial proteins enhanced binding of FH19-20 to C3b and down-regulation of complement activation. We show that this is caused by formation of a tripartite complex between the microbial protein, FH, and C3b. In this study we reveal that seven microbes representing different phyla utilize a common binding site on the domain 20 of FH for complement evasion. Binding via this site not only mimics the glycosaminoglycans of the host cells, but also enhances function of FH on the microbial surfaces via the novel mechanism of tripartite complex formation. This is a unique example of convergent evolution resulting in enhanced immune evasion of important pathogens via utilization of a “superevasion site.”

Complement is an important arm of innate immunity. Activation of this plasma protein cascade leads to opsonization of targets for phagocytosis, direct lysis of Gram-negative bacteria, and enhancement of the inflammatory and acquired immune responses. No specific signal is needed for activation of the alternative pathway of complement, leading to its activation on all unprotected surfaces. Pathogenic microbes need to evade this pathway, and several species are known to recruit host complement inhibitor factor H (FH) to prevent the activation. FH is important for protection of host cells, too, as defects in FH lead to a severe autoreactive disease, atypical hemolytic uremic syndrome. We have now identified at the molecular level a common mechanism by which seven different microbes, Haemophilus influenzae, Bordetella pertussis, Pseudomonas aeruginosa, Streptococcus pneumoniae, Candida albicans, Borrelia burgdorferi and B. hermsii, recruit FH. All microbes bind FH via a common site on domain 20, which facilitates formation of a tripartite complex between the microbial protein, the main complement opsonin C3b, and FH. We show that, by utilizing the common microbial binding site on FH20, microbes can inhibit complement more efficiently. This detailed knowledge on mechanism of complement evasion can be used in developing novel antimicrobial chemotherapy.

RELAPSING FEVER, A DISAPPEARING CAUSE OF FEVER AND MATERNAL DEATH IN SENGEREMA, TANZANIA, EAST AFRICA

OBJECTIVE

To study the incidence of tick borne relapsing fever (TBRF) during the last 50 years, once like malaria an endemic disease in Sengerema, Tanzania.

DESIGN

By analyzing the annual reports, focusing on the number of admissions, maternal deaths, blood smears of patients with fever for Borrelia.

SETTING

Sengerema district, Tanzania.

SUBJECT

Admissions in Sengerema Hospital due to TBRF.

MAIN OUTCOME MEASURES

From 1960 to 2010, we analyzed the incidence of TBRF.

RESULT

Forty annual admissions in the sixties/seventies, 200 in the eighties (range from 37 in 1964 to 455 in 1988), dropping to 30 in the nineties. For the last nine years no Borrelia spirochetes were found in blood smears at the laboratory anymore and no admissions for TBRF were registered. The number of maternal deaths due to relapsing fever decreased simultaneously; the last one recordedwas in 2002.

CONCLUSION

During the last century, we have witnessed the disappearing of tick borne relapsing fever in Sengerema. Increase of gold mining, improved local economy, housing and standards of living after the nineties resulted in an almost complete eradication of the incidence of TBRF.

Borrelia valaisiana resist complement-mediated killing independently of the recruitment of immune regulators and inactivation of complement components

Spirochetes belonging to the Borrelia (B.) burgdorferi sensu lato complex differ in their resistance to complement-mediated killing, particularly in regard to human serum. In the present study, we elucidate the serum and complement susceptibility of B. valaisiana, a genospecies with the potential to cause Lyme disease in Europe as well as in Asia. Among the investigated isolates, growth of ZWU3 Ny3 was not affected while growth of VS116 and Bv9 was strongly inhibited in the presence of 50% human serum. Analyzing complement activation, complement components C3, C4 and C6 were deposited on the surface of isolates VS116 and Bv9, and similarly the membrane attack complex was formed on their surface. In contrast, no surface-deposited components and no aberrations in cell morphology were detected for serum-resistant ZWU3 Ny3. While further investigating the protective role of bound complement regulators in mediating complement resistance, we discovered that none of the B. valaisiana isolates analyzed bound complement regulators Factor H, Factor H-like protein 1, C4b binding protein or C1 esterase inhibitor. In addition, B. valaisiana also lacked intrinsic proteolytic activity to degrade complement components C3, C3b, C4, C4b, and C5. Taken together, these findings suggest that certain B. valaisiana isolates differ in their capability to resist complement-mediating killing by human serum. The molecular mechanism utilized by B. valaisiana to inhibit bacteriolysis appears not to involve binding of the key host complement regulators of the alternative, classical, and lectin pathways as already known for serum-resistant Lyme disease or relapsing fever borreliae.

Associations between coinfection prevalence of Borrelia lusitaniae, Anaplasma sp., and Rickettsia sp. in hard ticks feeding on reptile hosts

An increasing number of studies reveal that ticks and their hosts are infected with multiple pathogens, suggesting that coinfection might be frequent for both vectors and wild reservoir hosts. Whereas the examination of associations between coinfecting pathogen agents in natural host-vector-pathogen systems is a prerequisite for a better understanding of disease maintenance and transmission, the associations between pathogens within vectors or hosts are seldom explicitly examined. We examined the prevalence of pathogen agents and the patterns of associations between them under natural conditions, using a previously unexamined host-vector-pathogen system--green lizards Lacerta viridis, hard ticks Ixodes ricinus, and Borrelia, Anaplasma, and Rickettsia pathogens. We found that immature ticks infesting a temperate lizard species in Central Europe were infected with multiple pathogens. Considering I. ricinus nymphs and larvae, the prevalence of Anaplasma, Borrelia, and Rickettsia was 13.1% and 8.7%, 12.8% and 1.3%, and 4.5% and 2.7%, respectively. The patterns of pathogen prevalence and observed coinfection rates suggest that the risk of tick infection with one pathogen is not independent of other pathogens. Our results indicate that Anaplasma can play a role in suppressing the transmission of Borrelia to tick vectors. Overall, however, positive effects of Borrelia on Anaplasma seem to prevail as judged by higher-than-expected Borrelia-Anaplasma coinfection rates.

[Ticks infected with bacteria pathogenic to humans in municipal parks in Warsaw]

The aim of the study was to detect bacteria pathogenic to humans, such as Borrelia burgdorferi sensu lato, Rickettsia spp, and Coxiella burnetii in ticks found in municipal parks in Warsaw, including The Royal Łazienki Park, Mokotów Fields, Józef Sowiński Park, Ujazdów Park and Fort Bema Park. To detect microorganisms PCR technique was used. It was shown that 6.1% of the ticks in Warsaw's parks are infected with B. burgdorferi sensu lato, and 2.9% with Rickettsia spp. Analysis of sequencing results revealed in examined ticks the presence of B. burgdorferi sensu stricto and R. helvetica.

Interleukin-10 mediated autoregulation of murine B-1 B-cells and its role in Borrelia hermsii infection

B cells are typically characterized as positive regulators of the immune response, primarily by producing antibodies. However, recent studies indicate that various subsets of B cells can perform regulatory functions mainly through IL-10 secretion. Here we discovered that peritoneal B-1 (B-1P) cells produce high levels of IL-10 upon stimulation with several Toll-like receptor (TLR) ligands. High levels of IL-10 suppressed B-1P cell proliferation and differentiation response to all TLR ligands studied in an autocrine manner in vitro and in vivo. IL-10 that accumulated in cultures inhibited B-1P cells at second and subsequent cell divisions mainly at the G1/S interphase. IL-10 inhibits TLR induced B-1P cell activation by blocking the classical NF-κB pathway. Co-stimulation with CD40 or BAFF abrogated the IL-10 inhibitory effect on B-1P cells during TLR stimulation. Finally, B-1P cells adoptively transferred from the peritoneal cavity of IL-10^−/− mice showed better clearance of Borrelia hermsii than wild-type B-1P cells. This study described a novel autoregulatory property of B-1P cells mediated by B-1P cell derived IL-10, which may affect the function of B-1P cells in infection and autoimmunity.

Borrelia recurrentis employs a novel multifunctional surface protein with anti-complement, anti-opsonic and invasive potential to escape innate immunity

Borrelia recurrentis, the etiologic agent of louse-borne relapsing fever in humans, has evolved strategies, including antigenic variation, to evade immune defence, thereby causing severe diseases with high mortality rates. Here we identify for the first time a multifunctional surface lipoprotein of B. recurrentis, termed HcpA, and demonstrate that it binds human complement regulators, Factor H, CFHR-1, and simultaneously, the host protease plasminogen. Cell surface bound factor H was found to retain its activity and to confer resistance to complement attack. Moreover, ectopic expression of HcpA in a B. burgdorferi B313 strain, deficient in Factor H binding proteins, protected the transformed spirochetes from complement-mediated killing. Furthermore, HcpA-bound plasminogen/plasmin endows B. recurrentis with the potential to resist opsonization and to degrade extracellular matrix components. Together, the present study underscores the high virulence potential of B. recurrentis. The elucidation of the molecular basis underlying the versatile strategies of B. recurrentis to escape innate immunity and to persist in human tissues, including the brain, may help to understand the pathological processes underlying louse-borne relapsing fever.

The genome of Borrelia recurrentis, the agent of deadly louse-borne relapsing fever, is a degraded subset of tick-borne Borrelia duttonii

In an effort to understand how a tick-borne pathogen adapts to the body louse, we sequenced and compared the genomes of the recurrent fever agents Borrelia recurrentis and B. duttonii. The 1,242,163–1,574,910-bp fragmented genomes of B. recurrentis and B. duttonii contain a unique 23-kb linear plasmid. This linear plasmid exhibits a large polyT track within the promoter region of an intact variable large protein gene and a telomere resolvase that is unique to Borrelia. The genome content is characterized by several repeat families, including antigenic lipoproteins. B. recurrentis exhibited a 20.4% genome size reduction and appeared to be a strain of B. duttonii, with a decaying genome, possibly due to the accumulation of genomic errors induced by the loss of recA and mutS. Accompanying this were increases in the number of impaired genes and a reduction in coding capacity, including surface-exposed lipoproteins and putative virulence factors. Analysis of the reconstructed ancestral sequence compared to B. duttonii and B. recurrentis was consistent with the accelerated evolution observed in B. recurrentis. Vector specialization of louse-borne pathogens responsible for major epidemics was associated with rapid genome reduction. The correlation between gene loss and increased virulence of B. recurrentis parallels that of Rickettsia prowazekii, with both species being genomic subsets of less-virulent strains.

Borreliae are vector-borne spirochetes that are responsible for Lyme disease and recurrent fevers. We completed the genome sequences of the tick-borne Borrelia duttonii and the louse-borne B. recurrentis. The former of these is responsible for emerging infections that mimic malaria in Africa and in travellers, and the latter is responsible for severe recurrent fever in poor African populations. Diagnostic tools for these pathogens remain poor with regard to sensitivity and specificity due, in part, to the lack of genomic sequences. In this study, we show that the genomic content of B. recurrentis is a subset of that of B. duttonii, the genes of which are undergoing a decay process. These phenomena are common to all louse-borne pathogens compared to their tick-borne counterparts. In B. recurrentis, this process may be due to the inactivation of genes encoding DNA repair mechanisms, implying the accumulation of errors in the genome. The increased virulence of B. recurrentis could not be traced back to specific virulence factors, illustrating the lack of correlation between the virulence of a pathogen and so-called virulence genes. Knowledge of these genomes will allow for the development of new molecular tools that provide a more-accurate, sensitive, and specific diagnosis of these emerging infections.

A system for site-specific genetic manipulation of the relapsing fever spirochete Borrelia hermsii

The lack of a system for genetic manipulation has hindered studies on the molecular pathogenesis of relapsing fever Borrelia. The focus of this chapter is to describe selectable markers, manipulation strategies, and methods to electro-transform and clone wild-type infectious Borrelia hermsii. Preliminary studies suggest that the variable tick protein (Vtp) of B. hermsii is involved in tick-to-mammal transmission. To address this hypothesis, we have developed a system for genetic manipulation and have constructed clones of a Vtp mutant and an isogenic reconstituted strain. The methods described here are applicable for the inactivation of other loci in B. hermsii and should be adaptable for other species of relapsing fever spirochetes.

Tick-borne zoonotic bacteria in wild and domestic small mammals in northern Spain

The prevalence and diversity of tick-borne zoonotic bacteria (Borrelia spp., Anaplasma phagocytophilum, Coxiella burnetii, and spotted fever group rickettsiae) infecting 253 small mammals captured in the Basque Country (Spain) were assessed using PCR and reverse line blot hybridization. Trapping sites were selected around sheep farms (study 1, 2000 to 2002) and recreational parks (study 2, 2003 to 2005). The majority of the studied mammals (162) were wood mice (Apodemus sylvaticus), but six other different species were also analyzed: yellow-necked mice (Apodemus flavicollis), shrews (Crocidura russula and Sorex coronatus), bank voles (Clethrionomys glareolus), domestic mice (Mus domesticus), and moles (Talpa europaea). The results showed an infection rate ranging from 10.7% to 68.8%, depending on the small mammal species. One C. russula shrew and one A. sylvaticus mouse gave positive reactions for A. phagocytophilum, and C. burnetii was detected in two domestic mice and one A. sylvaticus mouse in a farm. The DNA of Borrelia spp. was detected in 67 animals (26.5%), most of them presenting positive hybridization with the probe for Borrelia sp. strain R57, the new Borrelia species previously detected in small mammals in our region. Furthermore, a second PCR and reverse line blot hybridization specific for B. burgdorferi sensu lato revealed the presence of Borrelia afzelii in 6.3% of C. glareolus voles and 14.3% of S. coronatus shrews. All small mammals were negative for spotted fever group rickettsiae. These results highlight the relevance of small mammals as reservoirs of some zoonotic bacteria.

Dual binding specificity of a Borrelia hermsii-associated complement regulator-acquiring surface protein for factor H and plasminogen discloses a putative virulence factor of relapsing fever spirochetes

Tick-borne relapsing fever in North America is primarily caused by the spirochete Borrelia hermsii. The pathogen employs multiple strategies, including the acquisition of complement regulators and antigenic variation, to escape innate and humoral immunity. In this study we identified in B. hermsii a novel member of the complement regulator-acquiring surface protein (CRASP) family, designated BhCRASP-1, that binds the complement regulators factor H (FH) and FH-related protein 1 (FHR-1) but not FH-like protein 1 (FHL-1). BhCRASP-1 specifically interacts with the short consensus repeat 20 of FH, thereby maintaining FH-associated cofactor activity for factor I-mediated C3b inactivation. Furthermore, ectopic expression of BhCRASP- 1 converted the serum-sensitive Borrelia burgdorferi B313 strain into an intermediate complement-resistant strain. Finally, we report for the first time that BhCRASP-1 binds plasminogen/plasmin in addition to FH via, however, distinct nonoverlapping domains. The fact that surface-bound plasmin retains its proteolytic activity suggest that the dual binding specificity of BhCRASP-1 for FH and plasminogen/plasmin contributes to both the dissemination/invasion of B. hermsii and its resistance to innate immunity.

Lyme neuroborreliosis: infection, immunity, and inflammation

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

Coinfection with Borrelia turicatae serotype 2 prevents the severe vestibular dysfunction and earlier mortality caused by serotype 1

BACKGROUND

Relapsing fever (RF) is a multisystemic spirochetal infection caused by different Borrelia species. Studies in our laboratory have shown that disease severity varies depending on the infecting serotype. However, the relative contribution of each serotype to pathogenesis during mixed infections is not known. To investigate this, we compared the outcome of infection with isogenic serotypes 1 (Bt1) or 2 (Bt2) of the RF agent B. turicatae alone or in combination.

METHODS

B cell-deficient mice were used for these experiments, to avoid serotype clearance by the host's variable membrane protein-specific antibodies. Observers masked to infection status examined infected and uninfected control mice for clinical disease and functional impairment for up to 65 days.

RESULTS

All mice developed persistent infection with the serotypes with which they were originally inoculated. Severe vestibular dysfunction developed in mice infected with Bt1 alone and was associated with increased morbidity and mortality. However, coinfection with Bt2 significantly reduced the severity of vestibular dysfunction and prevented earlier mortality. In contrast, coinfection with Bt1 had little effect on the severe arthritis caused by Bt2 infection.

CONCLUSIONS

The manifestations of infection with B. turicatae are significantly influenced by the combination of serotypes present during mixed infection.

Borrelia lusitaniae in immature Ixodes ricinus (Acari: Ixodidae) feeding on common wall lizards in Tuscany, central Italy

Lizards and small rodents were live captured in Tuscany, central Italy, from May through August 2005. Prevalence of infestation by larval Ixodes ricinus L. (Acari: Ixodidae) and mean numbers of larvae per host were not significantly different for common wall lizards, Podarcis muralis Laurenti, and Apodemus spp. mice, whereas infestation levels by nymphs were significantly greater on lizards. Borrelia lusitaniae, which was previously shown to be dominant in host-seeking I. ricinus in the same study area, was detected by polymerase chain reaction (PCR) in 19.8% (95% confidence interval: 14.4, 26.0) of larval ticks and in 52.9% (27.8, 77.0) of nymphs that were collected from lizards. Moreover, 18.8% (7.2, 36.4) and 25.0 (3.2, 65.1) of lizards' tail biopsies and blood samples, respectively, were positive for B. lusitaniae. Conversely, attached ticks and ear biopsies from Apodemus spp. mice were PCR negative. Passerine birds belonging to 10 species were live captured in March 2005, and Borrelia valaisiana was detected in 57.1% (18.4, 90.1) of I. ricinus nymphs feeding on Eurasian blackbirds, Turdus merula L. Results of this study suggest that lizards play an important role as reservoirs for B. lusitanae and may affect the dominance of this genospecies in the Mediterranean area.

Pathogens and host DNA in Ixodes ricinus nymphal ticks from a German forest

Unfed nymphs of Ixodes ricinus were collected from vegetation in a forest on the outskirts of Berlin, Germany and were analyzed for host and pathogen DNA. Pathogens were detected in 47% of the ticks. Borrelia afzelii was the commonest pathogen detected, followed by Rickettsia helvetica. Other pathogens included B. valaisiana, B. garinii, B. burgdorferi sensu stricto, Anaplasma phagocytophilum, and a relapsing fever-like Borrelia. Most of the host DNA detected was of rodent origin and was associated with infection by B. afzelii, R. helvetica, and A. phagocytophilum. Bird DNA was associated with B. valaisiana and B. garinii, and ruminant DNA with A. phagocytophilum. B. afzelii was also found in two ticks that contained bird DNA.

Pathogen escape from host immunity by a genome program for antigenic variation

The vector-borne bacterium Borrelia hermsii, a relapsing fever agent, switches gene expression of a surface protein between different antigenic variants, thereby causing sequential waves of immune escape within hosts and increasing the likelihood of transmission. Analogous programmed systems of antigenic variation occur in African trypanosomes and Plasmodium falciparum. In these examples, switch rates to individual variants differ over a wide range. We studied how B. hermsii determines switch rates in two experimental infections: one where variants were identified by specific antisera and one based on identification by DNA sequence. Unexpressed loci of variant antigens copy into a single expression site at rates determined by extragenic features of silent loci rather than similarity between coding sequences of variants at silent sites and the single expression site. Two elements, in particular, determine switch rates. One set of elements overlaps the 5' ends of the expressed gene and the silent loci; greater sequence identity between elements was associated with a higher switch rate. The second set of elements flanks the expression site on the 3' side and occurs at variable distances downstream from silent loci; the nearer an element to a silent locus, the greater the switch rate of that locus into the expression site. In combination, these two features of the genome provide a simple mechanism to modulate switch rate whereby silent loci form a hierarchy of switch rates into the expression site. Although the switching hierarchy causes changes in individual cells that are stochastic, ordering of variants within hosts is semipredictable.

Alzheimer's disease Braak Stage progressions: reexamined and redefined as Borrelia infection transmission through neural circuits

Brain structure in health is a dynamic energized equation incorporating chemistry, neuronal structure, and circuitry components. The chemistry "piece" is represented by multiple neurotransmitters such as Acetylcholine, Serotonin, and Dopamine. The neuronal structure "piece" incorporates synapses and their connections. And finally circuits of neurons establish "architectural blueprints" of anatomic wiring diagrams of the higher order of brain neuron organizations. In Alzheimer's disease, there are progressive losses in all of these components. Brain structure crumbles. The deterioration in Alzheimer's is ordered, reproducible, and stepwise. Drs. Braak and Braak have described stages in the Alzheimer disease continuum. "Progressions" through Braak Stages benchmark "Regressions" in Cognitive function. Under the microscope, the Stages of Braak commence in brain regions near to the hippocampus, and over time, like a tsunami wave of destruction, overturn healthy brain regions, with neurofibrillary tangle damaged neurons "marching" through the temporal lobe, neocortex and occipital cortex. In effect the destruction ascends from the limbic regions to progressively destroy the higher brain centers. Rabies infection also "begins low and finishes high" in its wave of destruction of brain tissue. Herpes Zoster infections offer the paradigm of clinical latency of infection inside of nerves before the "marching commences". Varicella Zoster virus enters neurons in the pediatric years. Dormant virus remains inside the neurons for 50-80 years, tissue damage late in life (shingles) demonstrates the "march of the infection" down neural pathways (dermatomes) as linear areas of painful blisters loaded with virus from a childhood infection. Amalgamation of Zoster with Rabies models produces a hybrid model to explain all of the Braak Stages of Alzheimer's disease under a new paradigm, namely "Alzheimer's neuroborreliosis" in which latent Borrelia infections ascend neural circuits through the hippocampus to the higher brain centers, creating a trail of neurofibrillary tangle injured neurons in neural circuits of cholinergic neurons by transsynaptic transmission of infection from nerve to nerve.

Use of CFSE staining of borreliae in studies on the interaction between borreliae and human neutrophils

Background

Species of the tick-transmitted spirochete group Borrelia burgdorferi sensu lato (B. burgdorferi) cause Lyme borreliosis. Acute borrelial infection of the skin has unusual characteristics with only a mild local inflammatory response suggesting that the interaction between borreliae and the cells of the first-line defence might differ from that of other bacteria. It has been reported that human neutrophils phagocytose motile borreliae through an unconventional mechanism (tube phagocytosis) which is not observed with non-motile borreliae. Therefore, it would be of great interest to visualise the bacteria by a method not affecting motility and viability of borreliae to be able to study their interaction with the cells of the innate immunity. Carboxyfluorescein diacetate, succinimidyl ester (CFSE) labelling has been previously used for studying the adhesion of labelled bacteria to host cells and the uptake of labelled substrates by various cells using flow cytometry.

Results

In this study, CFSE was shown to efficiently stain different genospecies of B. burgdorferi without affecting bacterial viability or motility. Use of CFSE staining allowed subsequent quantification of borreliae associated with human neutrophils with flow cytometry and confocal microscopy. As a result, no difference in association between different borrelial genospecies (Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii), or between borreliae and the pyogenic bacterium Streptococcus pyogenes, with neutrophils could be detected. Borrelial virulence, on the other hand, affected association with neutrophils, with significantly higher association of a non-virulent mutant B. burgdorferi sensu stricto strain compared to the parental virulent wild type strain.

Conclusion

These results suggest that the flow cytometric assay using CFSE labelled borreliae is a valuable tool in the analysis of the interaction between borreliae and human neutrophils. The results also indicate a clear difference in the association with neutrophils between virulent and non-virulent borrelial strains.

Interaction of a neurotropic strain of Borrelia turicatae with the cerebral microcirculation system

Relapsing fever (RF) is a spirochetal infection characterized by relapses of a febrile illness and spirochetemia due to the sequential appearance and disappearance of isogenic serotypes in the blood. The only difference between isogenic serotypes is the variable major outer membrane lipoprotein. In the absence of specific antibody, established serotypes cause persistent infection. Studies in our laboratory indicate that another consequence of serotype switching in RF is a change in neuroinvasiveness. As the next step to elucidate this phenomenon, we studied the interaction of the neurotropic Oz1 strain of the RF agent Borrelia turicatae with the cerebral microcirculation. During persistent infection of antibody-deficient mice, we found that serotype 1 entered the brain in larger numbers and caused more severe cerebral microgliosis than isogenic serotype 2. Microscopic examination revealed binding of B. turicatae to brain microvascular endothelial cells in vivo. In vitro we found that B. turicatae associated with brain microvascular endothelial cells (BMEC) significantly more than with fibroblasts or arachnoidal cells. The binding was completely eliminated by pretreatment of BMEC with proteinase K. Using transwell chambers with BMEC barriers, we found that serotype 1 crossed into the lower compartment significantly better than serotype 2. Heat killing significantly reduced BMEC crossing but not binding. We concluded that the interaction of B. turicatae with the cerebral microcirculation involves both binding and crossing brain microvascular endothelial cells, with significant differences among isogenic serotypes.

Relapsing fever spirochetes Borrelia recurrentis and B. duttonii acquire complement regulators C4b-binding protein and factor H

Relapsing fever is a rapidly progressive and severe septic disease caused by certain Borrelia spirochetes. The disease is divided into two forms, i.e., epidemic relapsing fever, caused by Borrelia recurrentis and transmitted by lice, and the endemic form, caused by several Borrelia species, such as B. duttonii, and transmitted by soft-bodied ticks. The spirochetes enter the bloodstream by the vector bite and live persistently in plasma even after the development of specific antibodies. This leads to fever relapses and high mortality and clearly indicates that the Borrelia organisms utilize effective immune evasion strategies. In this study, we show that the epidemic relapsing fever pathogen B. recurrentis and an endemic relapsing fever pathogen, B. duttonii, are serum resistant, i.e., resistant to complement in vitro. They acquire the host alternative complement pathway regulator factor H on their surfaces in a similar way to that of the less serum-resistant Lyme disease pathogen, B. burgdorferi sensu stricto. More importantly, the relapsing fever spirochetes specifically bind host C4b-binding protein, a major regulator of the antibody-mediated classical complement pathway. Both complement regulators retained their functional activities when bound to the surfaces of the spirochetes. In conclusion, this is the first report of complement evasion by Borrelia recurrentis and B. duttonii and the first report showing capture of C4b-binding protein by spirochetes.

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.

Relapsing fever spirochaetes produce a serine protease that provides resistance to oxidative stress and killing by neutrophils

The spirochaetes that cause tick-borne relapsing fever and Lyme disease are closely related human pathogens, yet they differ significantly in their ecology and pathogenicity. Genome sequencing of two species of relapsing fever spirochaetes, Borrelia hermsii and Borrelia turicatae, identified a chromosomal open reading frame, designated bhpA, not present in the Lyme disease spirochaete Borrelia burgdorferi. The predicted amino acid sequence of bhpA was homologous with the HtrA serine proteases, which are involved with stress responses and virulence in other bacteria. B. hermsii produced an active serine protease that was recognized by BhpA antibodies and the recombinant BhpA protein-degraded beta-casein. bhpA was transcribed in vitro at all growth temperatures and transcription levels were slightly elevated at higher temperatures. These results correlated with the synthesis of BhpA during B. hermsii infection in mice. With the exception of Borrelia recurrentis, the bhpA gene, protein and enzymatic activity were found in all relapsing fever spirochaetes, but not in Lyme disease or related spirochaetes. Heterologous expression of bhpA in B. burgdorferi increased the spirochaete's resistance to both oxidative stress and killing by human neutrophils. Therefore, we propose that bhpA encodes a unique and functional serine protease in relapsing fever spirochaetes. This periplasmic enzyme may prevent the accumulation of proteins damaged by the innate immune response and contribute to the ability of the relapsing fever spirochaetes to achieve high cell densities in blood.

Residual brain infection in relapsing-fever borreliosis

BACKGROUND

Neurological involvement is common in the spirochetal infection relapsing fever (RF) in both humans and experimental animals. RF is best known for antigenic variation caused by the sequential expression of variable outer membrane lipoproteins of 2 sizes, variable small (Vsp) and variable large (Vlp) proteins. Less understood is the persistence of RF borreliae in the brain after they are cleared from the blood, referred to as residual brain infection (RBI). Our goal was to investigate the phenomenon of RBI in RF.

METHODS

We studied RBI in immunocompetent mice by culturing blood and perfused brain samples 1 month after intraperitoneal inoculation with Borrelia turicatae serotype 1 (Bt1). Mice deficient in Toll-like receptor 2 (TLR2-/-) or in B and T cells (scid) were included for comparison.

RESULTS

All scid mice had persistent infection in blood and brain. RBI was found in 3 (19%) of 16 immunocompetent and TLR2-/- mice. RBI was caused by either persistence of the original serotype (Bt1) or newly emerged Vsp (n=1, renamed Bt3) or Vlp serotypes. The Vsp of Bt1 (Vsp1) and Bt3 (Vsp3) were 75% identical.

CONCLUSIONS

RBI in RF is relatively frequent and can occur by persistence of the original or newly emerged serotypes.

White-tailed deer (Odocoileus virginianus) develop spirochetemia following experimental infection with Borrelia lonestari

Borrelia lonestari is considered a putative agent of southern tick-associated rash illness (STARI) and is known to occur naturally only in lone star ticks (Amblyomma americanum) and white-tailed deer (Odocoileus virginianus). We used a low passage isolate of B. lonestari (LS-1) to inoculate white-tailed deer, C3H mice, Holstein cattle, and beagles. Animals were monitored via examination of Giemsa and acridine orange stained blood smears, polymerase chain reaction (PCR), indirect fluorescent antibody (IFA) test, and/or culture isolation. Spirochetes were visualized in blood smears of both deer on days post-inoculation (DPI) 6, 8, 12 and one deer on DPI 15. Whole blood collected from deer tested PCR positive starting on DPI 4 and remained positive as long as DPI 28. Both deer developed antibody titers of >64, with a maximum IFA titer of 1024. The organism was reisolated from the blood of both deer on DPI 6 and one deer on DPI 12. All isolation attempts from mice, calves, or dogs were negative, although one of seven mice was transiently PCR positive. Mice and dogs developed an IFA titer > or =64, while calves lacked a detectable antibody response. These preliminary experimental infection trials show that white-tailed deer are susceptible to infection with B. lonestari and develop a spirochetemia following needle-inoculation, while C3H mice, calves, and dogs do not. Results suggest that deer may serve as a vertebrate reservoir host. Tick transmission studies are needed to confirm that this organism can be maintained in a natural cycle involving deer and A. americanum.

Lyme borreliosis in Portugal caused by Borrelia lusitaniae? Clinical report on the first patient with a positive skin isolate

BACKGROUND

Borrelia lusitaniae was isolated from an Ixodes ricinus tick in Portugal in 1993 for the first time. Further, this borrelia genospecies has been found in ixodid ticks collected around the coasts of southern Portugal and North Africa. Its reservoir has not been defined yet. B. lusitaniae was isolated once until now from a patient with a long standing and expanding skin disorder.

PATIENT AND METHODS

A 46-year-old Portuguese woman presented with a skin lesion on the left thigh which had evolved slowly over ten years. The patient reported limb paraesthesias, cramps, chronic headaches, and cardiac rhythm disturbances. History of tick bites was negative nor had the patient ever noticed a skin lesion comparable with erythema chronicum migrans. Skin biopsies were taken for histological evaluation, culture and DNA detection. Antibodies to borrelia were searched by indirect immunofluorescence assay and Western-blot.

RESULTS

A bilateral carpal tunnel syndrome and local synovitis was diagnosed. Dermato-histology was normal, serology was negative. Spirochaetal organisms were cultured from a skin biopsy and identified as B. lusitaniae. The patient improved after a 2-week course of intravenous ceftriaxone; the skin lesions did not expand further.

CONCLUSIONS

This culture confirmed skin infection by B. lusitaniae in a patient from Portugal suggests an additional human pathogen out of the B. burgdorferi sensu lato complex in Europe, particularly in Portugal.

Infection-Induced Marginal Zone B Cell Production ofBorrelia hermsii-Specific Antibody Is Impaired in the Absence of CD1d

Ab that arise in the absence of T cell help are a critical host defense against infection with the spirochetes Borrelia burgdorferi and Borrelia hermsii. We have previously shown that CD1d-deficient (CD1d(-/-)) mice have impaired resistance to infection with B. burgdorferi. In mice, CD1d expression is highest on marginal zone B (MZB) cells, which produce Ab to blood-borne Ag. In this study we examined MZB cell activation and Ab production in mice infected with B. hermsii, which achieve high levels of bacteremia. We show by flow cytometry that MZB cells associate with B. hermsii and up-regulate the activation markers syndecan I and B7.1 within 16 h of infection. By 24 h, MZB cells secrete B. hermsii-specific IgM, coinciding with the loss of activation marker expression and the reduction in spirochete burden. In contrast, MZB cells from CD1d(-/-) mice remain activated for at least 96 h of infection, but produce only minimal B. hermsii-specific IgM in vivo and ex vivo; pathogen burden in the blood also remains elevated. Wild-type mice depleted of MZB cells using mAb to LFA-1 and alpha(4)beta(1) integrin have reduced serum levels of B. hermsii-specific IgM and increased pathogen burden, similar to B. hermsii-infected CD1d(-/-) mice. Passive transfer of immune mouse serum, but not naive mouse serum, into infected CD1d(-/-) mice leads to down-regulation of activation markers and clearance of B. hermsii from the MZB cells. These results demonstrate that blood-borne spirochetes activate MZB cells to produce pathogen-specific IgM and reveal a role for CD1d in this process.

Demonstration of the involvement of outer surface protein E coiled coil structural domains and higher order structural elements in the binding of infection-induced antibody and the complement-regulatory protein, factor H

Factor H (fH) is an important regulator of the alternative complement cascade. Several human pathogens have been shown to bind fH to their surface, a process that facilitates immune evasion or cell to cell interaction. Among the pathogens that bind fH are some Borrelia species associated with Lyme disease and relapsing fever. The fH-binding proteins of the Lyme spirochetes form two classes (I and II). In Borrelia burgdorferi B31MI, class I includes the outer surface protein E (OspE) paralogs, L39, N38, and P38, whereas the class II group includes A68 and additional proteins that have not yet been identified. To identify the OspE determinants involved in fH and OspE-targeting infection-induced Ab (iAb) binding, deletion, random, and site-directed mutagenesis of L39 were performed. Mutations in several different regions of L39 abolished fH and or iAb binding, indicating that separable domains and residues of OspE are required for ligand binding. Some of the mutants that lost the ability to bind fH, iAb, or both had only a single amino acid change. Site-directed mutagenesis of three putative coiled coil motifs of OspE revealed that these higher order structures are required for fH binding but not for iAb binding. The data presented within demonstrate that the binding of fH and iAb to the OspE protein is mediated by higher order structures and protein conformation. These studies advance our understanding of fH binding as a virulence mechanism and facilitate ongoing efforts to use fH-binding proteins in the development of microbial vaccines.

Hosts and pathogen detection for immature stages of Ixodes ricinus (Acari: Ixodidae) in North-Central Spain

To determine hosts of the immature stages of a southern population of Ixodes ricinus, we trapped rodents and birds in an area of north-central Spain in May-June and August-September of 1998 and 1999. The most frequently trapped rodents were Apodemus sylvaticus (230 specimens) and Clethrionomys glareolus (99), with a larval infestation prevalence of 49% and 81%, respectively (in spring) and 21% and 41% (in summer). C. glareolus was always more heavily parasitized by larvae (mean numbers 19.8 in spring, 3.4 in summer) than A. sylvaticus (6.1 and 1.2, respectively). No nymphs were collected from the rodents. The larval distribution pattern differed considerably between rodent host species but not according to the season of the year. The most commonly trapped birds were members of the Turdidae, which had infestation incidences of about 70% (larvae) and 10% (nymphs) in spring and 20-15% in summer. We also used molecular methods for the identification of reservoir hosts of the larval ticks and of the pathogens they contained, from nymphs collected in the same site in June of 2002 and 2003. The study showed that most of the ticks had fed on birds and few on rodents and ruminants. Pathogens detected in these ticks included Babesia microti, Borrelia garinii, B. valaisiana and B. afzelii. Borrelia afzelii was detected in a tick that had apparently fed on a wild boar.

Concentration of interferon-inducible T cell chemoattractant and monocyte chemotactic protein-1 in serum and cerebrospinal fluid of patients with Lyme borreliosis

PURPOSE

Chronic inflammation in Lyme borreliosis may be sustained by aberrant inflammatory response, characterized by Th1 lymphocyte predominance, which in turn may be determined by chemokines synthesized in inflammatory focus. The aim of the study was to evaluate synthesis of chemokines: interferon-induced T cell chemoattractant (I-TAC--chemoattractant for Th1 lymphocytes), and monocyte chemotactic protein (MCP-1) in Lyme borreliosis.

MATERIAL AND METHODS

Study group consisted of 13 patients with erythema migrans, 10 with Lyme arthritis and 6 with neuroborreliosis. Serum, as well as cerebrospinal fluid (CSF) in neuroborreliosis, was obtained before (examination 1) and during (examination 2) antibiotic treatment. Control serum was obtained from 8 healthy volunteers and control csf from 8 patients in whom meningitis and neuroborreliosis was excluded after diagnostic lumbar puncture. The samples were assayed for MCP-1 and I-TAC by ELISA.

RESULTS

Serum mean I-TAC concentration in examination 1 was 73.0 pg/ml in erythema migrans, 78.9 pg/ml in Lyme arthritis and 87.3 pg/ml in neuroborreliosis (29.9 pg/ml in controls, difference significant for neuroborreliosis) and did not change significantly in examination 2. MCP-1 serum concentration was significantly increased to 497.5 pg/ml in neuroborreliosis in examination 2. I-TAC concentration in csf remained low, while MCP-1 concentration in examination 1 was increased to 589.1 pg/ml, significantly higher than simultaneously in serum.

CONCLUSIONS

I-TAC synthesis is increased in Lyme borreliosis and may be a factor favoring predominance of Th1 lymphocyte subset. MCP-1 creates chemotactic gradient towards central nervous system and may contribute to csf pleocytosis in neuroborreliosis.

Isolation and characterization of Borrelia hermsii associated with two foci of tick-borne relapsing fever in California

Relapsing fever, caused by the spirochete Borrelia hermsii and transmitted by the soft tick Ornithodoros hermsi, is endemic in many rural mountainous areas of California. Between 1996 and 1998, 12 cases of relapsing fever associated with two exposure sites in northern California were investigated. Follow-up at exposure sites included collection of soft ticks and serum specimens from sylvatic rodents. Attempts to cultivate spirochetes were made through inoculation of patient blood into mice and by feeding Ornithodoros ticks on mice. Three isolates of B. hermsii were recovered from two blood specimens and one pool of ticks. The protein and plasmid profiles of the three isolates were comparable to those of previous B. hermsii isolates from the western United States. Western immunoblotting of patient sera demonstrated an expanding immunologic response to antigens within four distinct molecular weight regions by 3 to 4 weeks postonset. Antibody to B. hermsii was detected in sera from 4 of 11 yellow-pine chipmunks (Tamias amoenus); no other rodent species collected were seropositive.