CD55 Facilitates Immune Evasion by Borrelia crocidurae, an Agent of Relapsing Fever

Relapsing fever, caused by diverse Borrelia spirochetes, is prevalent in many parts of the world and causes significant morbidity and mortality. To investigate the pathoetiology of relapsing fever, we performed a high-throughput screen of Borrelia-binding host factors using a library of human extracellular and secretory proteins and identified CD55 as a novel host binding partner of Borrelia crocidurae and Borrelia persica, two agents of relapsing fever in Africa and Eurasia. CD55 is present on the surface of erythrocytes, carries the Cromer blood group antigens, and protects cells from complement-mediated lysis. Using flow cytometry, we confirmed that both human and murine CD55 bound to B. crocidurae and B. persica. Given the expression of CD55 on erythrocytes, we investigated the role of CD55 in pathological B. crocidurae-induced erythrocyte aggregation (rosettes), which enables spirochete immune evasion. We showed that rosette formation was partially dependent on host cell CD55 expression. Pharmacologically, soluble recombinant CD55 inhibited erythrocyte rosette formation. Finally, CD55-deficient mice infected with B. crocidurae had a lower pathogen load and elevated proinflammatory cytokine and complement factor C5a levels. In summary, our results indicate that CD55 is a host factor that is manipulated by the causative agents of relapsing fever for immune evasion. IMPORTANCE Borrelia species are causative agents of Lyme disease and relapsing fever infections in humans. B. crocidurae causes one of the most prevalent relapsing fever infections in parts of West Africa. In the endemic regions, B. crocidurae is present in ~17% of the ticks and ~11% of the rodents that serve as reservoirs. In Senegal, ~7% of patients with acute febrile illness were found to be infected with B. crocidurae. There is little information on host-pathogen interactions and how B. crocidurae manipulates host immunity. In this study, we used a high-throughput screen to identify host proteins that interact with relapsing fever-causing Borrelia species. We identified CD55 as one of the host proteins that bind to B. crocidurae and B. persica, the two causes of relapsing fever in Africa and Eurasia. We show that the interaction of B. crocidurae with CD55, present on the surface of erythrocytes, is key to immune evasion and successful infection in vivo. Our study further shows the role of CD55 in complement regulation, regulation of inflammatory cytokine levels, and innate immunity during relapsing fever infection. Overall, this study sheds light on host-pathogen interactions during relapsing fever infection in vivo.

Tick borne relapsing fever - a systematic review and analysis of the literature

Tick borne relapsing fever (TBRF) is a zoonosis caused by various Borrelia species transmitted to humans by both soft-bodied and (more recently recognized) hard-bodied ticks. In recent years, molecular diagnostic techniques have allowed to extend our knowledge on the global epidemiological picture of this neglected disease. Nevertheless, due to the patchy occurrence of the disease and the lack of large clinical studies, the knowledge on several clinical aspects of the disease remains limited. In order to shed light on some of these aspects, we have systematically reviewed the literature on TBRF and summarized the existing data on epidemiology and clinical aspects of the disease. Publications were identified by using a predefined search strategy on electronic databases and a subsequent review of the reference lists of the obtained publications. All publications reporting patients with a confirmed diagnosis of TBRF published in English, French, Italian, German, and Hungarian were included. Maps showing the epidemiogeographic mosaic of the different TBRF Borrelia species were compiled and data on clinical aspects of TBRF were analysed. The epidemiogeographic mosaic of TBRF is complex and still continues to evolve. Ticks harbouring TBRF Borrelia have been reported worldwide, with the exception of Antarctica and Australia. Although only molecular diagnostic methods allow for species identification, microscopy remains the diagnostic gold standard in most clinical settings. The most suggestive symptom in TBRF is the eponymous relapsing fever (present in 100% of the cases). Thrombocytopenia is the most suggestive laboratory finding in TBRF. Neurological complications are frequent in TBRF. Treatment is with beta-lactams, tetracyclines or macrolids. The risk of Jarisch-Herxheimer reaction (JHR) appears to be lower in TBRF (19.3%) compared to louse-borne relapsing fever (LBRF) (55.8%). The overall case fatality rate of TBRF (6.5%) and LBRF (4-10.2%) appears to not differ. Unlike LBRF, where perinatal fatalities are primarily attributable to abortion, TBRF-related perinatal fatalities appear to primarily affect newborns.

Analysis of selected serological parameters in patients with diagnosed Lyme borreliosis and in seropositive patients with no clinical symptoms

OBJECTIVES

The aim of the study was to analyze some metalloproteinases, cytokines, and chemokines in LB patients and healthy seropositive subjects. The presence of IgM/IgG antibodies against specific Borreliella antigens was analyzed in the presence or absence of clinical manifestations of LB.

MATERIAL AND METHODS

The study involved 38 patients diagnosed with LB and arthralgia and/or arthritis symptoms, and 57 foresters presenting no clinical symptoms of LB. The ELISA test was applied for general screening of anti-Borreliella IgM/IgG. Western blot was used for confirmatory diagnosis of LB for the positive and borderline results. Serum IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ, TNF, IL-8, CCL5, CXCL9/MIG, CCL2/MCP-1, CXCL10/IP-10 concentrations were measured with the use of the Human Cytometric CBA test. The concentration of MMP-2 and MMP-9 in the serum was determined with the use of ELISA tests.

RESULTS

Analysis of the cytokines and chemokines revealed that only the concentration of IL-2 was significantly higher (2.4 pg/m; p=0.00641) in patients with LB symptoms than in the seropositive individuals (0.4 pg/ml). The MMP2 concentration was significantly higher (233.3 ng/ml; p=0.00294) in patients with clinical manifestations of LB than in those occupationally exposed to tick bites, but did not have anti-Borreliella antibodies (192.0 ng/ml).

CONCLUSIONS

The presence of IgG antibodies against a number of Borreliella antigens and the differences in the IL-2 and MMP2 levels in seropositive or seronegative individuals and symptomatic LB patients, may indicate differences in the intensity of the immune response to the infection and, consequently, may induce development of clinical manifestations of the disease in seropositive and seronegative individuals.

Borrelia miyamotoi strain LB-2001 retains plasmids and infectious phenotype throughout continuous culture passages as evaluated by multiplex PCR

Borrelia miyamotoi is a tick-borne spirochete of the relapsing fever borrelia group and an emerging pathogen of public health significance. The genomes of relapsing fever borreliae and Lyme disease borreliae consist of multiple linear and circular plasmids in addition to the chromosome. Previous work with B. burgdorferi sensu lato found diminished infectivity upon continuous in vitro culture passage that was attributable to plasmid loss. The effect of long-term culture passage on B. miyamotoi is not known. We generated a series of plasmid-specific primer sets and developed a multiplex PCR assay to detect the 14 known plasmids of B. miyamotoi North American strains LB-2001 and CT13-2396. We assessed the plasmid content of B. miyamotoi LB-2001 over 64 culture passages spanning 15 months and determined that strain LB-2001 retained all plasmids upon prolonged in vitro cultivation and remained infectious in mice. We also found that strain LB-2001 lacks plasmid lp20-1 which is present in strain CT13-2396. These results suggest that B. miyamotoi remains genetically stable when cultured and passaged in vitro.

Live Imaging

Being able to vizualize a pathogen at a site of interaction with a host is an aesthetically appealing idea and the resulting images can be both informative as well as enjoyable to view. Moreover, the approaches used to derive these images can be powerful in terms of offering data unobtainable by other methods. In this article, we review three primary modalities for live imaging Borrelia spirochetes: whole animal imaging, intravital microscopy and live cell imaging. Each method has strengths and weaknesses, which we review, as well as specific purposes for which they are optimally utilized. Live imaging borriliae is a relatively recent development and there was a need of a review to cover the area. Here, in addition to the methods themselves, we also review areas of spirochete biology that have been significantly impacted by live imaging and present a collection of images associated with the forward motion in the field driven by imaging studies.

Evolutionary ecology of Lyme Borrelia

The bacterial genus, Borrelia, is comprised of vector-borne spirochete species that infect and are transmitted from multiple host species. Some Borrelia species cause highly-prevalent diseases in humans and domestic animals. Evolutionary, ecological, and molecular research on many Borrelia species have resulted in tremendous progress toward understanding the biology and natural history of these species. Yet, many outstanding questions, such as how Borrelia populations will be impacted by climate and land-use change, will require an interdisciplinary approach. The evolutionary ecology research framework incorporates theory and data from evolutionary, ecological, and molecular studies while overcoming common assumptions within each field that can hinder integration across these disciplines. Evolutionary ecology offers a framework to evaluate the ecological consequences of evolved traits and to predict how present-day ecological processes may result in further evolutionary change. Studies of microbes with complex transmission cycles, like Borrelia, which interact with multiple vertebrate hosts and arthropod vectors, are poised to leverage the power of the evolutionary ecology framework to identify the molecular interactions involved in ecological processes that result in evolutionary change. Using existing data, we outline how evolutionary ecology theory can delineate how interactions with other species and the physical environment create selective forces or impact migration of Borrelia populations and result in micro-evolutionary changes. We further discuss the ecological and molecular consequences of those micro-evolutionary changes. While many of the currently outstanding questions will necessitate new experimental designs and additional empirical data, many others can be addressed immediately by integrating existing molecular and ecological data within an evolutionary ecology framework.

Host Competency of the Multimammate Rat Mastomys natalensis Demonstrated by Prolonged Spirochetemias with the African Relapsing Fever Spirochete Borrelia crocidurae

African multimammate rats, Mastomys natalensis, are widely distributed in sub-Saharan Africa and live in close association with humans. In West Africa, numerous field studies have shown these animals may be naturally infected with the relapsing fever spirochete Borrelia crocidurae, the primary cause of tick-borne relapsing fever in this region of the continent. However, naturally infected individual rats have never been examined over time; therefore, the true host competency of these rats for this spirochete is unknown. Therefore, using animals from an established laboratory colony of M. natalensis, rats were experimentally infected with B. crocidurae and their blood examined to 28 days postinoculation. These animals were highly susceptible to infection and displayed prolonged and cyclic spirochetemias. Our results demonstrate these peridomestic rodents are likely competent hosts for infecting argasid tick vectors and play a primary role in the enzootic cycle for B. crocidurae in West Africa.

Identification of immunoreactive linear epitopes of Borrelia miyamotoi

Borrelia miyamotoi is an emerging tick-borne spirochete transmitted by ixodid ticks. Current serologic assays for B. miyamotoi are impacted by genetic similarities to other Borrelia and limited understanding of optimal antigenic targets. In this study, we employed the TBD-Serochip, a peptide array platform, to identify new linear targets for serologic detection of B. miyamotoi. We examined a wide range of suspected B. miyamotoi antigens and identified 352 IgM and 91 IgG reactive peptides, with the majority mapping to variable membrane proteins. These included peptides within conserved fragments of variable membrane proteins that may have greater potential for differential diagnosis. We also identified reactive regions on FlaB, and demonstrate crossreactivity of B. burgdorferi s.l. C6 with a B. miyamotoi C6-like peptide. The panel of linear peptides identified in this study can be used to enhance serodiagnosis of B. miyamotoi.

Questing Ixodes ricinus ticks (Acari, Ixodidae) as a vector of Borrelia burgdorferi sensu lato and Borrelia miyamotoi in an urban area of north-eastern Poland

Green areas located within large cities, as natural ecotypes, are a convenient habitat for ticks and their use as recreational areas is associated with the potential risk of acquiring tick-borne diseases. This study estimated the I. ricinus tick density, prevalence of infection with Borrelia species and the diversity of these bacteria in a green urban area (Olsztyn) of north-eastern Poland, an endemic region of tick-borne diseases. The ticks were collected during spring and autumn of 2015, at sites differing in the degree of human pressure and habitat. Borrelia species detection, typing and a molecular phylogenetic analysis were carried out based on the sequenced flaB gene. The overall mean abundance of I. ricinus was 2.0 ± 1.55 ticks per 100 m². The density of I. ricinus did not vary significantly between sites. According to semi-qualitative tick abundance categories, the collection sites were classified as 'very low' and 'low' tick abundance category. The overall infection rate of I. ricinus with Borrelia spirochaetes was 27.4%. The infection rate of adult ticks (42.0%) was three times higher than with nymphs (14.3%). Based on the restriction patterns and sequencing, B. afzelii (93.1%; 27/29), B. valaisiana 3.5% (1/29) and B. miyamotoi (3.5%; 1/29), related to the relapsing fever (RF) spirochaetes, were detected. No co-infections were found. Borrelia miyamotoi, detected for the first time in ticks in the north-eastern urban areas of Poland, was identical to isolates described as European-type. The Borrelia spirochaete infection rate of I. ricinus ticks in an urban area indicated a high risk of LB. Physicians should also be aware of B. miyamotoi infections among patients with a history of tick-bites in north-eastern Poland.

Rickettsiales Occurrence and Co-occurrence in Ixodes ricinus Ticks in Natural and Urban Areas

Bacteria of Rickettsiaceae and Anaplasmataceae families include disease agents spread by Ixodes ricinus ticks, the most common tick vector in Europe. The aim of the study was to compare the prevalence and co-infection prevalence of particular tick-transmitted Rickettsiales members: Rickettsia spp. (further referred as Rs), Anaplasma phagocytophilum (Ap), and "Candidatus Neoehrlichia mikurensis" (CNM) in I. ricinus ticks in two types of areas, different in terms of human impact: natural and urban. Using additional data, we aimed at investigating co-occurrence of these Rickettsiales with Borreliella spp. A total of 4189 tick specimens, 2363 from the urban area (Warsaw park and forests) and 1826 from the natural area (forests and park in the vicinity of National Parks), were tested for the presence of Rickettsiales DNA by PCRs. The prevalence of selected Rickettsiales was twice higher in urban than natural areas (13.2% vs. 6.9%, respectively). In total ticks, the prevalence of Rs, Ap, and CNM was 6.5%, 5.3%, and 3.6% in urban areas vs. 4.4%, 1.1%, and 2.1% in natural areas, respectively. Co-infections of Rickettsiales were also more prevalent in urban areas (2.6% vs. 0.3%, respectively). The most common Rs was R. helvetica; also R. monacensis and novel "Candidatus Rickettsia mendelii" were detected. Positive association between Ap and CNM infections was discovered. Rickettsiales bacteria occurrence was not associated with Borreliella occurrence, but co-infections with these two groups were more common in ticks in urban areas. In conclusion, three groups of Rickettsiales constituted the important part of the tick pathogen community in Poland, especially in the urbanized central Poland (Mazovia). In the Warsaw agglomeration, there is a greater risk of encountering the I. ricinus tick infected with Rickettsiales and co-infected with Lyme spirochaetes, in comparison to natural areas. This finding raises the question whether cities might in fact be the hot spots for TBDs.

First report of Borrelia miyamotoi in an Ixodes ricinus tick in Augsburg, Germany

Borrelia miyamotoi, a spirochete found in the hard tick Ixodes ricinus, is thought to cause relapsing fever. The disease caused by this bacterium can manifest with high fever, fatigue and other symptoms. It may also lead to central nervous system involvement with symptoms similar to meningoencephalitis. DNA from ticks from the greater Augsburg region in Germany was subjected to qPCR for Borrelia spp., followed by nested PCR and subsequent sequencing for species identification of the qPCR positive samples. From 112 ticks, 20 were found to be positive for Borrelia. The DNA sequenced showed 50% Borrelia afzelli, 15% Borrelia garinii, 5% Borrelia valaisiana and one sequence was identified as Borrelia miyamotoi. The positive identification of Borrelia miyamotoi is unlikely to be due to contamination. In conclusion, Borrelia miyamotoi has been found in a tick in the Augsburg region for the first time. This follows on from previous reports of a low incidence of this bacterium in southern Germany around Lake Constance and in the Munich region. This infectious agent should be taken into account when patients present with recurring fever or neurological symptoms which cannot be otherwise explained. Tick-borne relapsing fever should now be considered as a cause of such symptoms and medical professionals should contemplate differential Borrelia testing when presented with corresponding symptoms.

Ecological niche modeling and distribution of Ornithodoros hermsi associated with tick-borne relapsing fever in western North America

Tick-borne relapsing fever in western North America is a zoonosis caused by the spirochete bacterium, Borrelia hermsii, which is transmitted by the bite of infected Ornithodoros hermsi ticks. The pathogen is maintained in natural cycles involving small rodent hosts such as chipmunks and tree squirrels, as well as the tick vector. In order for these ticks to establish sustained and viable populations, a narrow set of environmental parameters must exist, primarily moderate temperatures and moderate to high amounts of precipitation. Maximum Entropy Species Distribution Modeling (Maxent) was used to predict the species distribution of O. hermsi and B. hermsii through time and space based on current climatic trends and future projected climate changes. From this modeling process, we found that the projected current distributions of both the tick and spirochete align with known endemic foci for the disease. Further, global climate models predict a shift in the distribution of suitable habitat for the tick vector to higher elevations. Our predictions are useful for targeting surveillance efforts in areas of high risk in western North America, increasing the efficiency and accuracy of public health investigations and vector control efforts.

The model presented here provides valuable epidemiological information on tick-borne relapsing fever in western North America. The inference gleaned from these models represents areas where human infection with B. hermsii is likely to occur. The predicted distribution of O. hermsi and B. hermsii may allow health officials to decrease human disease burden by implementing targeted surveillance efforts, thus better utilizing resources. The models we created predict the current distribution of O. hermsi and B. hermsii, as well as the predicted distribution in 2050 under medium and high greenhouse gas (GHG) concentration trajectories. Understanding how the distribution of the pathogen and its vector expand or contract in response to GHG concentrations is necessary for understanding human risk of infection with this debilitating disease both now and in the future.

Transmission of the Lyme Disease Spirochete Borrelia mayonii in Relation to Duration of Attachment by Nymphal Ixodes scapularis (Acari: Ixodidae)

The recently recognized Lyme disease spirochete, Borrelia mayonii, has been detected in host-seeking Ixodes scapularis Say ticks and is associated with human disease in the Upper Midwest. Although experimentally shown to be vector competent, studies have been lacking to determine the duration of time from attachment of a single B. mayonii-infected I. scapularis nymph to transmission of spirochetes to a host. If B. mayonii spirochetes were found to be transmitted within the first 24 h after tick attachment, in contrast to Borrelia burgdorferi spirochetes (>24 h), then current recommendations for tick checks and prompt tick removal as a way to prevent transmission of Lyme disease spirochetes would need to be amended. We therefore conducted a study to determine the probability of transmission of B. mayonii spirochetes from single infected nymphal I. scapularis ticks to susceptible experimental mouse hosts at three time points postattachment (24, 48, and 72 h) and for a complete feed (>72-96 h). No evidence of infection with or exposure to B. mayonii occurred in mice that were fed upon by a single infected nymph for 24 or 48 h. The probability of transmission by a single infected nymphal tick was 31% after 72 h of attachment and 57% for a complete feed. In addition, due to unintended simultaneous feeding upon some mice by two B. mayonii-infected nymphs, we recorded a single occasion in which feeding for 48 h by two infected nymphs resulted in transmission and viable infection in the mouse. We conclude that the duration of attachment of a single infected nymphal I. scapularis tick required for transmission of B. mayonii appears to be similar to that for B. burgdorferi: transmission is minimal for the first 24 h of attachment, rare up to 48 h, but then increases distinctly by 72 h postattachment.

An In Vitro Blood-Feeding Method Revealed Differential Borrelia turicatae (Spirochaetales: Spirochaetaceae) Gene Expression After Spirochete Acquisition and Colonization in the Soft Tick Ornithodoros turicata (Acari: Argasidae)

In the Midwestern, Southwestern, and Southern part of the United States, the soft tick Ornithodoros turicata transmits the spirochete Borrelia turicatae, the causative agent of relapsing fever in humans. In this study, we report a simplified and an efficient method of in vitro feeding to evaluate O. turicata-B. turicatae interactions. Both nymphal and adult female ticks successfully acquired spirochetes upon in vitro feeding on the B. turicatae-infected blood. We also noted transstadial transmission of spirochetes to adult ticks that were molted from nymphs fed on B. turicatae-infected blood. A differential expression pattern for some of the B. turicatae genes was evident after acquisition and colonization of the vector. The levels of arthropod-associated lipoprotein Alp-mRNA were significantly upregulated and the mRNA levels of factor H binding protein FhbA and immunogenic protein BipA were significantly downregulated in the spirochetes after acquisition into ticks in comparison with spirochetes grown in culture medium. In addition, genes such as bta124 and bta116 were significantly upregulated in spirochetes in unfed ticks in comparison with the levels noted in spirochetes after acquisition. These findings represent an efficient in vitro blood-feeding method to study B. turicatae gene expression after acquisition and colonization in these ticks. In summary, we report that B. turicatae survive and develop in the tick host when acquired by in vitro feeding. We also report that B. turicatae genes are differentially expressed in ticks in comparison with the in vitro-grown cultures, indicating influence of tick environment on spirochete gene expression.

Louse-borne relapsing fever in a refugee from Mali

INTRODUCTION

Due to the increasing number of refugees from East Africa, louse-borne relapsing fever (LBRF) has become an emergent disease in Europe. No single case of LBRF has been reported in Europe in refugees from other parts of Africa.

CASE REPORT

We report a case of LBRF in a refugee from Mali, likely acquired in Libya, where several migration routes into Europe meet. The disease must be considered in any febrile refugee regardless the country of origin.

Where Are the Ticks? Solving the Mystery of a Tickborne Relapsing Fever Outbreak at a Youth Camp

During the summer of 2014 an outbreak of tickborne relapsing fever (TBRF) occurred in a group of high school students and staff at a youth camp, which was reported to Coconino County Public Health Services District. Six confirmed and five probable cases of TBRF occurred. During the environmental investigation two rodents tested positive for TBRF, but the vector, soft ticks, could not be found in their "normal" habitat. Ticks were finally located in areas not typical for soft ticks.

Relapsing Fever Borreliae: A Global Review

Relapsing fever borreliae were notorious and feared infectious agents that earned their place in history through their devastating impact as causes of both epidemic and endemic infection. They are now considered more as an oddity, and their burden of infection is largely overshadowed by other infections such as malaria, which presents in a similar clinical way. Despite this, they remain the most common bacterial infection in some developing countries. Transmitted by soft ticks or lice, these fascinating spirochetes have evolved a myriad of mechanisms to survive within their diverse environments.

Detection of borreliae in archived sera from patients with clinically suspect Lyme disease

The diagnoses of Lyme disease based on clinical manifestations, serological findings and detection of infectious agents often contradict each other. We tested 52 blind-coded serum samples, including 20 pre-treatment and 12 post-treatment sera from clinically suspect Lyme disease patients, for the presence of residual Lyme disease infectious agents, using nested PCR amplification of a signature segment of the borrelial 16S ribosomal RNA gene for detection and direct DNA sequencing of the PCR amplicon for molecular validation. These archived sera were split from the samples drawn for the 2-tier serology tests performed by a CDC-approved laboratory, and are used as reference materials for evaluating new diagnostic reagents. Of the 12 post-treatment serum samples, we found DNA evidence of a novel borrelia of uncertain significance in one, which was also positive for the 2-tier serology test. The rest of the post-treatment sera and all 20 control sera were PCR-negative. Of the 20 pre-treatment sera from clinically suspect early Lyme disease patients, we found Borrelia miyamotoi in one which was 2-tier serology-negative, and a Borrelia burgdorferi in two-one negative and one positive for 2-tier serology. We conclude that a sensitive and reliable DNA-based test is needed to support the diagnosis of Lyme disease and Lyme disease-like borreliosis.

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.

Functional insights into recombinant TROSPA protein from Ixodes ricinus

Lyme disease (also called borreliosis) is a prevalent chronic disease transmitted by ticks and caused by Borrelia burgdorferi s. l. spirochete. At least one tick protein, namely TROSPA from I. scapularis, commonly occurring in the USA, was shown to be required for colonization of the vector by bacteria. Located in the tick gut, TROSPA interacts with the spirochete outer surface protein A (OspA) and initiates the tick colonization. Ixodes ricinus is a primary vector involved in B. burgdorferi s. l. transmission in most European countries. In this study, we characterized the capacities of recombinant TROSPA protein from I. ricinus to interact with OspA from different Borrelia species and to induce an immune response in animals. We also showed that the N-terminal part of TROSPA (a putative transmembrane domain) is not involved in the interaction with OspA and that reduction of the total negative charge on the TROSPA protein impaired TROSPA-OspA binding. In general, the data presented in this paper indicate that recombinant TROSPA protein retains the capacity to form a complex with OspA and induces a significant level of IgG in orally immunized rats. Thus, I. ricinus TROSPA may be considered a good candidate component for an animal vaccine against Borrelia.

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.

Elevated carbon monoxide in the exhaled breath of mice during a systemic bacterial infection

Blood is the specimen of choice for most laboratory tests for diagnosis and disease monitoring. Sampling exhaled breath is a noninvasive alternative to phlebotomy and has the potential for real-time monitoring at the bedside. Improved instrumentation has advanced breath analysis for several gaseous compounds from humans. However, application to small animal models of diseases and physiology has been limited. To extend breath analysis to mice, we crafted a means for collecting nose-only breath samples from groups and individual animals who were awake. Samples were subjected to gas chromatography and mass spectrometry procedures developed for highly sensitive analysis of trace volatile organic compounds (VOCs) in the atmosphere. We evaluated the system with experimental systemic infections of severe combined immunodeficiency Mus musculus with the bacterium Borrelia hermsii. Infected mice developed bacterial densities of ∼10⁷ per ml of blood by day 4 or 5 and in comparison to uninfected controls had hepatosplenomegaly and elevations of both inflammatory and anti-inflammatory cytokines. While 12 samples from individual infected mice on days 4 and 5 and 6 samples from uninfected mice did not significantly differ for 72 different VOCs, carbon monoxide (CO) was elevated in samples from infected mice, with a mean (95% confidence limits) effect size of 4.2 (2.8–5.6), when differences in CO₂ in the breath were taken into account. Normalized CO values declined to the uninfected range after one day of treatment with the antibiotic ceftriaxone. Strongly correlated with CO in the breath were levels of heme oxygenase-1 protein in serum and HMOX1 transcripts in whole blood. These results (i) provide further evidence of the informativeness of CO concentration in the exhaled breath during systemic infection and inflammation, and (ii) encourage evaluation of this noninvasive analytic approach in other various other rodent models of infection and for utility in clinical management.

Transovarial transmission of Borrelia spirochetes by Ixodes scapularis: a summary of the literature and recent observations

Transovarial transmission (TOT) of Borrelia burgdorferi (sensu lato), the agent of Lyme disease, by the Ixodes persulcatus group of hard ticks (Ixodidae) has frequently been reported in the literature since the discovery of Lyme disease 1982. Evidence for and against TOT by B. burgdorferi has led to uncertainty and confusion in the literature, causing misconceptions that may have public health consequences. In this report, we review the published information implicating B. burgdorferi as a bacterium transovarially transmitted among ticks of the Ixodes persulcatus group and present new data indicating the transovarially transmitted agent is actually Borrelia miyamotoi. B. miyamotoi, first described in 1995, is antigenically and phylogenetically related to B. burgdorferi, although more closely related to the relapsing fever-group Borrelia typically transmitted by soft ticks (Argasidae). Borrelia infections of unfed larvae derived from egg clutches of wild-caught Ixodes scapularis are demonstrated to result from transovarial transmission of B. miyamotoi, not B. burgdorferi. The presence of this second Borrelia species, apparently sympatric with B. burgdorferi worldwide also may explain other confusing observations reported on Borrelia/Ixodes relationships.

The correlation between tick (Ixodes persulcatus Sch.) questing behaviour and synganglion neuronal responses to odours

We examined the behavioural and electrophysiological responses of taiga ticks (Ixodes persulcatus) to several olfactory stimuli: Osmopherone® (5-a-androst-16-en-3-ol), Osmopherine® (butanoic and 3-methylbutanoic acids), DEET® (N,N-diethyl-meta-toluamide), ethanol (96%), and water (control stimulus). To study individual tick behavioural reactions to these stimuli, we used a Y-shaped glass maze (n=50). To study the electrophysiological reactions of the ticks' synganglia to these olfactory stimuli, we recorded the shifts of total potential (TP) of pre-oesophageal neurons in response to odour stimulation of Haller's organ (n=25). We found that Osmopherine® attracted ticks and frequently evoked negative shifts of TP, whereas the response to Osmopherone® did not differ from the reaction to water. DEET® and ethanol acted as tick repellents and generally evoked positive shifts of TP. We also tested each tick for its questing height (QH) on a glass rod that was at an incline of 75°, and we tested for the presence of pathogens i.e., DNA of Borrelia burgdorferi sp. s.l. and RNA of tick-borne encephalitis virus (TBEV). The degree of response to Osmopherine® positively correlated with the QH. The ticks with the highest values of QH showed a greater prevalence of the tick-borne pathogen Borrelia sp. s.l. compared with the ticks that did not reach the maximum QH. The present results show a correlation between the electrophysiological reaction of the synganglia of ticks and their behavioural responses to different odours.

Tick-borne relapsing fever borreliosis, rural senegal

Detecting spirochetes remains challenging in cases of African tick-borne relapsing fever. Using real-time PCR specific for the 16S rRNA Borrelia gene, we found 27 (13%) of 206 samples from febrile patients in rural Senegal to be positive, whereas thick blood smear examinations conducted at dispensaries identified only 4 (2%) as positive.

Established and emerging pathogens in Ixodes ricinus ticks collected from birds on a conservation island in the Baltic Sea

Tick-borne pathogens such as Lyme borreliosis spirochaetes, Anaplasma phagocytophilum, Rickettsia spp. and Babesia spp. cause a great variety of diseases in animals and humans. Although their importance with respect to emerging human diseases is increasing, many issues about their ecology are still unclear. In spring 2007, 191 Ixodes ricinus (Acari: Ixodidae) ticks were collected from 99 birds of 11 species on a bird conservation island in the Baltic Sea in order to test them for Borrelia spp., A. phagocytophilum, Rickettsia spp. and Babesia spp. infections. Identification of the pathogens was performed by polymerase chain reaction (PCR), restriction fragment length polymorphism and sequence analysis. The majority of birds with ticks testing positive were European robins and thrushes. Borrelia DNA was detected in 14.1%, A. phagocytophilum in 2.6%, rickettsiae in 7.3% and Babesia spp. in 4.7% of the ticks. Co-infections with different pathogens occurred in six ticks (3.1%). The fact that 11 ticks (five larvae, six nymphs) were infected with Borrelia afzelii suggests that birds may, contrary to current opinion, serve as reservoir hosts for this species. Among rickettsial infections, we identified Rickettsia monacensis and Rickettsia helvetica. As we detected five Rickettsia spp. positive larvae and two birds carried more than one infected tick, transmission of those pathogens from birds to ticks appears possible. Further characterization of Babesia infections revealed Babesia divergens and Babesia microti. The occurrence of Babesia spp. in a total of five larvae suggests that birds may be able to infect ticks, at least with Ba. microti, a species considered not to be transmitted transovarially in ticks.

Spirochetemia caused by Borrelia turicatae infection in 3 dogs in Texas

Spirochetemia was diagnosed in 2 Siberian Huskies and a Rottweiler from the northwestern region of Texas between June 1999 and October 2001. Clinical findings were nonspecific; tick exposure was documented in 2 of the dogs. Hematologic abnormalities included anemia (n=2), neutrophilia (n=2, including 1 with a left shift), lymphopenia (n=3), eosinopenia (n=3), and thrombocytopenia (n=2). One anemic dog had a positive Coombs' test. In 1 dog, Western blot analysis of serum yielded multiple positive bands with B turicatae lysate, indicating the spirochetemia most likely was due to B turicatae infection. In 2 dogs, spirochetes were cultured from the blood and identified using DNA analysis as Borrelia turicatae; 1 of these dogs also was seropositive for Ehrlichia canis and B burgdorferi. In 2 cases, spirochetemia was more prominent in blood smears prepared immediately after sample collection than in smears prepared from EDTA blood. Two dogs recovered with doxycycline treatment; 1 dog declined clinically despite treatment and was euthanized. B turicatae is the agent of tick-borne (endemic) relapsing fever in humans and is distinct from B burgdorferi, the agent of Lyme disease; however, serologic cross-reactivity may occur. B turicatae is transmitted by the soft tick, Ornithodoros turicata, and infection should be considered in dogs with spirochetemia and possible exposure to the tick vector.

Transmission of bacterial agents from lone star ticks to white-tailed deer

Amblyomma americanum (L.), the lone star tick, is an aggressive ixodid tick that has been implicated as a vector for several bacteria. Among these bacteria are the disease agents Ehrlichia chaffeensis and Ehrlichia ewingii, and the putative disease agent "Borrelia lonestari." The hypothesis in this study was that wild lone star ticks from northeastern Georgia are capable of transmitting all three agents to white-tailed deer, Odocoileus virginianus, a known reservoir host for E. chaffeensis. In this study, transmission of all three agents from wild caught lone star ticks to captive reared white-tailed deer was demonstrated by polymerase chain reaction (PCR), culture, or serology. Two of three deer showed evidence of E. chaffeensis and E. ewingii infection by polymerase chain reaction assay; all three deer showed evidence of B. lonestari by PCR assay. E. chaffeensis was isolated in culture from both PCR-positive deer on multiple days. All three deer seroconverted to E. chaffeensis, whereas one deer seroconverted to B. lonestari. This study supports the role of lone star ticks and white-tailed deer as a vector and reservoir host for E. chaffeensis and E. ewingii and suggests for the first time, transmission of B. lonestari from lone star ticks to white-tailed deer.

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.

Increased incidence of Lyme borreliosis in southern Sweden following mild winters and during warm, humid summers

The aim of the present study was to investigate the long-term incidence rate of Lyme borreliosis and, additionally, to determine whether a correlation exists between climatic factors and summer-season variations in the incidence of Lyme borreliosis. Climatic variability acts directly on tick population dynamics and indirectly on human exposure to Lyme borreliosis spirochetes. In this study, conducted in primary healthcare clinics in southeastern Sweden, electronic patient records from 1997-2003 were searched for those that fulfilled the criteria for erythema migrans. Using a multilevel Poisson regression model, the influence of various climatic factors on the summer-season variations in the incidence of erythema migrans were studied. The mean annual incidence rate was 464 cases of erythema migrans per 100,000 inhabitants. The incidence was significantly higher in women than in men, 505 and 423 cases per 100,000 inhabitants, respectively (p<0.001). The summer-season variations in the erythema migrans incidence rate correlated with the monthly mean summer temperatures (incidence rate ratio 1.12; p<0.001), the number of winter days with temperatures below 0 degrees C (incidence rate ratio 0.97; p<0.001), the monthly mean summer precipitation (incidence rate ratio 0.92; p<0.05), and the number of summer days with relative humidity above 86% (incidence rate ratio 1.04; p<0.05). In conclusion, Lyme borreliosis is highly endemic in southeastern Sweden. The climate in this area, which is favourable not only for human tick exposure but also for the abundance of host-seeking ticks, influences the summer-season variations in the incidence of Lyme borreliosis.

Beta-amyloid deposition and Alzheimer's type changes induced by Borrelia spirochetes

The pathological hallmarks of Alzheimer's disease (AD) consist of beta-amyloid plaques and neurofibrillary tangles in affected brain areas. The processes, which drive this host reaction are unknown. To determine whether an analogous host reaction to that occurring in AD could be induced by infectious agents, we exposed mammalian glial and neuronal cells in vitro to Borrelia burgdorferi spirochetes and to the inflammatory bacterial lipopolysaccharide (LPS). Morphological changes analogous to the amyloid deposits of AD brain were observed following 2-8 weeks of exposure to the spirochetes. Increased levels of beta-amyloid precursor protein (AbetaPP) and hyperphosphorylated tau were also detected by Western blots of extracts of cultured cells that had been treated with spirochetes or LPS. These observations indicate that, by exposure to bacteria or to their toxic products, host responses similar in nature to those observed in AD may be induced.

A life cycle for Borrelia spirochetes?

Subsequent to Schaudinn and Hoffman's visualization of Treponema pallidum in 1905, many distinguished syphilologists proposed that spirochetes have a life cycle. What is the "essence" of a life cycle? Simply put, life cycles are diverse arrays of life forms, which emerge in an ordered sequence; which are "connected" to one another across primary and secondary hosts, and constitute a cycle with "circular" relationship between hosts. Fecal-oral life cycles and blood-to-blood life cycles are exemplary of host parasite relationships in this realm. The "blood-to-blood" begins and ends with an insect taking a blood "meal". In this operatic scenario, a "blood-less" insect functions simultaneously as a hypodermic needle and as an incubator for some of the infectious components. The initial phase is inside the body fluid compartment of an insect. The second phase is in the blood or body fluid of a warm-blooded mammal. Third, is the phase inside the cell of a mammalian host. And a final portion of the "life" marked by "death" of the parasitized mammalian cells and the release of infectious parasites which return to the "warm" blood where the "cold blooded" vector again takes a blood meal. The cycle then begins again. In each phase of a blood to blood life cycle, the infectious agent changes its shape. Blood phase "profiles" look different from "tissue phase" profiles. Some of the tissue phase profiles may be "invisible". Borrelia spirochetes offer an excellent example of a life cycle, by virtue of the insect vector to mammalian "piece", the blood and intracellular residence "pieces" and the morphologic diversity "piece". Stereotypes of what a spirochete "should " look like, have actually produced a state of "perseveration" in spirochetal pathobiology. We have been "stuck" like a broken record, on the corkscrew form, and have failed to see the rest of the life cycle. Cystic, granular, and cell wall deficient spirochetal profiles, which were well known in the 19th and 20th centuries by such titans as Schaudinn, Hoffman, Noguchi, Delamater, Steiner, and Mattman, have been repudiated by professional microbiologists, and by pathologists who practice and who confer the status of 21st century truths in microbiology matters. Proper microscopic study, as is required by Dr. Robert Koch's second postulate, for establishing links between microbes and disease, presupposes that the microscopist be aware of the complete array of morphologic repertoires of the alleged pathogen. (Morphologies, which are herein introduced.).

Bacteriocidal activity of lizard and mouse serum for Borrelia lonestari, putative agent of a Lyme-like illness (AKA STARI or Masters disease) in Missouri

OBJECTIVE

To determine responses of Borrelia lonestari and Borrelia burgdorferi to Eastern Fence lizard (Sceloporus undulatus) and Swiss-Webster mouse (Mus musculus) sera.

RESULTS

Lizard sera lysed both Borrelia lonestari and Borrelia burgdorferi. Mouse sera lysed only Borrelia lonestari.

CONCLUSIONS

Borrelia lonestari and Borrelia burgdorferi spirochetes did not survive exposure to lizard sera. Mice are reservoirs for Borrelia burgdorferi but may not be a Borrelia lonestari reservoir because spirochetes did not survive exposure to mouse sera.

Relationships of a novel Lyme disease spirochete, Borrelia spielmani sp. nov., with its hosts in Central Europe

To determine whether the pathogenic variant of Lyme disease spirochetes, isolate A14S, is perpetuated in a particular reservoir-vector relationship, we screened vector ticks in various Central European sites for a related spirochete and determined its host association. A14S-like spirochetes infect numerous questing ticks in the Petite Camargue Alsacienne (PC). They frequently infect dormice, but no mice or voles. Garden dormice appear to be better reservoir hosts for A14S-like spirochetes than for Borrelia afzelii, because these spirochetes are retained longer and infect ticks more readily. Spirochetes associated with garden dormice in the PC site form a homologous entity with those isolated from a human patient in The Netherlands. Its unique biological relationship together with previous genetic characterization justifies designating this dormouse-associated genospecies as a distinct entity. Garden dormice serve as the main reservoir hosts of a novel genospecies, Borrelia spielmani sp. nov., one of several that cause Lyme disease in people.

Molecular analysis of the channel-forming protein P13 and its paralogue family 48 from different Lyme disease Borrelia species

The aetiological agent of Lyme disease, Borrelia burgdorferi cycles between its tick vector and mammalian hosts, implying that it can sense different environments and consequently change the expression of genes encoding several surface-associated proteins. The genome of the type strain B. burgdorferi B31 has revealed 175 different gene families. The p13 gene, situated on the chromosome, encodes a channel-forming protein that belongs to the gene family 48 consisting of eight additional paralogous genes. The heterogeneity of the P13 protein from different Lyme disease Borrelia strains was investigated. The predicted surface-exposed domains are the most heterogeneous regions and contain probable epitopes of P13. The membrane-spanning architecture of P13 was determined and a model for the location of this protein in the outer membrane is presented. The transcription of the paralogues of gene family 48 during in vitro culturing and in a mouse infection model was also analysed. The bba01 gene is the only p13 paralogue present in all three Lyme-disease-causing genospecies; it is stable during cultivation in vitro and the BBA01 protein was expressed in all Borrelia strains investigated. Conversely, paralogues bbi31, bbq06 and bbh41 were only detected in B. burgdorferi and the corresponding plasmids harbouring bbi31 and bbh41 were lost during in vitro passage. Finally, p13 and bbi31 are the only members of gene family 48 that are transcribed in mice, suggesting their importance during mammalian infection.

Coinoculation of Borrelia spp. with tick salivary gland lysate enhances spirochete load in mice and is tick species-specific

C3H/HeN mice were inoculated with 10(6) spirochetes, either Borrelia burgdorferi strain N40 or the Portuguese strain of B. lusitaniae, PotiB2. Mice receiving spirochetes coinoculated with salivary gland lysate (SGL) demonstrated significantly higher spirochete loads in target organs as measured by quantitative real-time polymerase chain reaction. This effect was tick dependent, in that Ixodes ricinus SGL specifically enhanced B. lusitaniae load, whereas I. scapularis SGL specifically increased B. burgdorferi N40 load, but did not significantly affect the dissemination of B. lusitaniae. Protein profile analysis indicated at least 5 major protein differences between I. scapularis and I. ricinus SGL, which can possibly account for this specific tick-spirochete interaction.

[Mixed infection in ticks: a rule or an exception?]

A hypothesis for the independence of acts of infection in ticks with pathogens from each other in mixed infection has been tested on the basis of the data available in the literature. In most cases the number of ticks with mixed infection is consistent with the independence hypothesis and fails to reinforce the statement that there is antagonism of pathogens. But in some reports the number of mixed-infected ticks is 3-13 times higher than the calculated number according to the accepted hypothesis. These facts suggest that the natural tolerance of ticks to pathogens due to primary infection may be reduced. Other possible reasons for differences in the actual and calculated number of mixed infected ticks are also discussed.

Use of a sentinel host system to study the questing behavior of Ixodes spinipalpis and its role in the transmission of Borrelia bissettii, human granulocytic ehrlichiosis, and Babesia microti

Ixodes spinipalpis maintains Borrelia bissettii spirochetes in Colorado in a cycle involving wood rats and deer mice. This tick has been described as nidicolous, remaining either attached to its rodent hosts or in the rodent nest. Nidicolous ticks pose little risk of pathogen transmission to humans if they do not actively quest for hosts. To investigate the questing potential of I. spinipalpis, sentinel mice were placed in an area where I. spinipalpis had been commonly found on wood rats and deer mice. Concurrently, wild rodent populations were trapped and analyzed for Lyme disease spirochetes, the agent of human granulocytic ehrlichiosis (aoHGE), and Babesia microti. A total of 122 I. spinipalpis larvae and 10 nymphs were found on 19% of 244 sentinel mice. In addition, 4 sentinel mice became infested with Malaraeus telchinus or Orchopeas neotomae fleas. Questing I. spinipalpis were positively associated with woody shrubs and negatively associated with sunny and grassy areas. Four sentinel mice became infected with aoHGE after having been fed upon only by I. spinipalpis larvae. One sentinel mouse became infected with B. bissettii after having an I. spinipalpis nymph feed on it, and one sentinel mouse became coinfected with aoHGE and B. bissettii after it was fed upon by a single I. spinipalpis nymph. These sentinel mouse conversions suggest the possibility that the aoHGE is transovarially transmitted by I. spinipalpis, and that I. spinipalpis is capable of simultaneously transmitting B. bissettii and the aoHGE. The findings that I. spinipalpis quest away from rodent nests and will attach to and infect sentinel mice may be of public health importance. It suggests the potential transmission of the agents of human granulocytic ehrlichiosis and Lyme disease to other hosts by I. spinipalpis, in regions of the western United States where Ixodes pacificus is not found.

Conversion of Borrelia garinii cystic forms to motile spirochetes in vivo

Cystic forms (also called spheroplasts or starvation forms) and their ability to reconvert into normal motile spirochetes have already been demonstrated in the Borrelia burgdorferi sensu lato complex. The aim of this study was to determine whether motile B. garinii could develop from cystic forms, not only in vitro but also in vivo, in cyst-inoculated mice. The cysts prepared in distilled water were able to reconvert into normal motile spirochetes at any time during in vitro experiments, lasting one month, even after freeze-thawing of the cysts. Motile spirochetes were successfully isolated from 2 out of 15 mice inoculated intraperitoneally with cystic forms, showing the infectivity of the cysts. The demonstrated capacity of the cysts to reconvert into motile spirochetes in vivo and their surprising resistance to adverse environmental conditions should lead to further studies on the role and function of these forms in Lyme disease.

Transmission of Borrelia garinii OspA serotype 4 to BALB/c mice by Ixodes ricinus ticks collected in the field

In Europe, Borrelia garinii OspA serotype 4 has been isolated from the cerebrospinal fluid of patients but, up to now, has never been identified among culture isolates from Ixodes ricinus ticks. This information raises the question of whether OspA serotype 4 is transmitted by I. ricinus in nature. In the present study, I. ricinus nymphs collected in an area of endemicity in southern Germany were allowed to feed on mice. Cultivation of ear biopsy specimens showed that six of seven B. garinii-infected mice were infected by OspA serotype 4. In contrast, very few B. garinii OspA serotype 4 organisms were isolated directly from the ticks which infected the mice; most isolates were B. afzelii. The infected mice transmitted mainly OspA serotype 4 to xenodiagnostic ticks, preferentially in combination with B. afzelii.

The relapsing fever spirochaete, Borrelia crocidurae, activates human endothelial cells and promotes the transendothelial migration of neutrophils

The blood-borne, erythrocyte-aggregating Borrelia crocidurae, the causative agent of African relapsing fever, have been shown to induce severe cellular lesions in mice. In this paper, we present the first report of how the endothelium is stimulated during an African relapsing fever B. crocidurae infection. B. crocidurae co-incubated with cultured human umbilical vein endothelial cells (HUVECs) activated endothelium in such way that E-selectin and intercellular adhesion molecule 1 (ICAM-1) became upregulated in a dose- and time-dependent fashion, as determined by a whole-cell enzyme-linked immunosorbent assay (ELISA). The upregulation was reduced by treatment that killed the bacteria, suggesting that viability is important for the stimulation of HUVECs by B. crocidurae. Furthermore, conditioned medium from HUVECs stimulated with B. crocidurae contained interleukin (IL)-8, which is a chemotactic agent for neutrophils. Activation of HUVECs by B. crocidurae resulted in migration of subsequently added neutrophils across the endothelial monolayers, and this migration was inhibited by antibodies to IL-8. The activation of endothelium by B. crocidurae may constitute a key pathophysiological mechanism in B. crocidurae-induced vascular damage.

Babesia microti and Borrelia bissettii transmission by Ixodes spinipalpis ticks among prairie voles, Microtus ochrogaster, in Colorado

An endemic transmission cycle of Babesia microti was discovered in Colorado in the foothills of the Rocky Mountains. B. microti were found by PCR in 4 of 25 Ixodes spinipalpis tick pools tested (a 3.2 % minimum infection rate) and in 87% (13 of 15) of Microtus ochrogaster (the prairie vole) spleen and blood samples. Using naturally infected I. spinipalpis collected from wild-caught M. ochrogaster as vectors, B. microti and Borrelia bissettii were successfully transmitted to laboratory-born M. ochrogaster. Neither I. spinipalpis, nor M. ochrogaster (the prairie vole) have been previously reported as a vector or a reservoir host of B. microti. Unlike the east coast of the United States where Peromyscus leucopus is an important reservoir for B. microti, evidence for Peromyscus spp. (neither P. maniculatus nor P. difficilis) as B. microti reservoirs was not found in this study.

Direct evidence for involvement of NF-kappaB in transcriptional activation of tumor necrosis factor by a spirochetal lipoprotein

Variable major lipoprotein (Vmp) is a major tumor necrosis factor (TNF)-inducing component of Borrelia recurrentis, the agent of louse-borne relapsing fever. B. recurrentis Vmp rapidly stimulates nuclear translocation of NF-kappaB and proinflammatory cytokine gene expression in the human monocyte-like cell line MonoMac 6. By overexpressing disabled mutant IkappaBalpha in MonoMac 6 cells cotransfected with a reporter gene, we provide evidence that NF-kappaB is essential for the transcriptional activation of TNF in this system.

Variable small protein (Vsp)-dependent and Vsp-independent pathways for glycosaminoglycan recognition by relapsing fever spirochaetes

Tick-borne relapsing fever, caused by pathogenic Borrelia such as B. hermsii and B. turicatae, features recurrent episodes of bacteraemia, each of which is caused by a population of spirochaetes that expresses a different variable major protein. Relapsing fever is also associated with the infection of a variety of tissues, such as the central nervous system. In this study, we show that glycosaminoglycans (GAGs) mediate the attachment of relapsing fever spirochaetes to mammalian cells. B. hermsii strain DAH bound to immobilized heparin, and heparin and dermatan sulphate blocked bacterial binding to host cells. Bacterial binding was diminished by inhibition of host cell GAG synthesis or sulphation, or by the enzymatic removal of GAGs. GAGs mediated the attachment of relapsing fever spirochaetes to potentially relevant target cells, such as endothelial and glial cells. B. hermsii was able to attach to GAGs independently of variable major proteins, because strains expressing the variable major proteins Vsp33, Vlp7 or no variable major protein at all each recognized GAGs. Nevertheless, we found that a variable major protein of B. turicatae directly promoted GAG binding by this relapsing fever spirochaete. B. turicatae strain Oz1 serotype B, which expresses the variable major protein VspB, bound to GAGs more efficiently than did B. turicatae Oz1 serotype A, which expresses VspA. Recombinant VspB, but not VspA, bound to heparin and dermatan sulphate. Previous studies have shown that strain Oz1 serotype B grows to higher concentrations in the blood than does Oz1 serotype A. Thus, relapsing fever spirochaetes have the potential to express Vsp-dependent and Vsp-independent GAG-binding activities and, for one pair of highly related B. turicatae strains, differences in GAG binding correlate with differences in tissue tropism.

Sexual transmission of Borrelia garinii by male Ixodes persulcatus ticks (Acari, Ixodidae)

We investigated the transmission of Borrelia garinii and Borrelia afzelii between male and female Ixodes persulcatus ticks. For this purpose the infection rate of partners from tick couples was determined by polymerase chain reaction and reverse line blot. In couples, where the male tick was infected with B. garinii, four out of nine female partners carried B. garinii. In eight couples, male ticks had a dual infection of B. afzelii and B. garinii and three female partners were infected by Borrelia spirochetes. Two female ticks carried B. garinii, and one female tick had a dual infection. No evidence for transmission of B. afzelii from male to female ticks was found among seven couples. In 45 couples where the female tick was infected, not one male tick carried spirochetes. The difference in the B. garinii infection rate between male and female ticks among these couples is highly significant. Our data suggest that transmission of B. garinii from male ticks to female ticks does occur. Sexual transmission of this pathogen may play an important role in the maintenance of B. garinii in I. persulcatus.

Ixodes ricinus strains in Europe

An analysis of cuticular hydrocarbons (CH) of unfed adult Ixodes ricinus ticks collected throughout Europe showed that there are 10 distinct I. ricinus groups. Studies on the seasonal and annual consistency of CH composition and possible effects of host and environmental factors suggested that CHs may be used as a genuine genetic marker for I. ricinus. Preliminary studies compared the vector competence of ticks from three of the most separated I. ricinus groups and the results suggested that there may be significant differences in tick susceptibility to Borrelia afzelii.

Transmission of the Lyme disease spirochete, Borrelia garinii, between infected and uninfected immature Ixodes persulcatus during cofeeding on mice

The ixodid tick, Ixodes persulcatus, serves as a vector for the Lyme disease spirochete, Borrelia garinii, in Japan. Transmission of the spirochete from infected nymphs to uninfected larvae during their cofeeding on mice was studied under laboratory conditions. Using feeding chambers, infected nymphs and uninfected larvae were allowed to cofeed on heads of normal BALB/c mice. In another group of mice, we separately exposed nymphs to the head and larvae to the back. The resultant engorged larvae were reared and the molted nymphs were examined for spirochetes. Spirochetal infections were found only in ticks that had fed together with infected ticks. The data strongly suggest that spirochetes can migrate from infected feeding ticks to their uninfected neighbors by way of host skin. Moreover, nymphs that had become infected through the cofeeding process could transmit spirochetes to mice.