Members of the paralogous gene family 12 from the Lyme disease agent Borrelia burgdorferi are non-specific DNA-binding proteins.

Lyme disease is the most prevalent vector-borne infectious disease in Europe and the USA. Borrelia burgdorferi, as the causative agent of Lyme disease, is transmitted to the mammalian host during the tick blood meal. To adapt to the different encountered environments, Borrelia has adjusted the expression pattern of various, mostly outer surface proteins. The function of most B. burgdorferi outer surface proteins remains unknown. We determined the crystal structure of a previously uncharacterized B. burgdorferi outer surface protein BBK01, known to belong to the paralogous gene family 12 (PFam12) as one of its five members. PFam12 members are shown to be upregulated as the tick starts its blood meal. Structural analysis of BBK01 revealed similarity to the coiled coil domain of structural maintenance of chromosomes (SMC) protein family members, while functional studies indicated that all PFam12 members are non-specific DNA-binding proteins. The residues involved in DNA binding were identified and probed by site-directed mutagenesis. The combination of SMC-like proteins being attached to the outer membrane and exposed to the environment or located in the periplasm, as observed in the case of PFam12 members, and displaying the ability to bind DNA, represents a unique feature previously not observed in bacteria.

Multiple factors affecting Ixodes ricinus ticks and associated pathogens in European temperate ecosystems (northeastern France).

In Europe, the main vector of tick-borne zoonoses is Ixodes ricinus, which has three life stages. During their development cycle, ticks take three separate blood meals from a wide variety of vertebrate hosts, during which they can acquire and transmit human pathogens such as Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis. In this study conducted in Northeastern France, we studied the importance of soil type, land use, forest stand type, and temporal dynamics on the abundance of ticks and their associated pathogens. Negative binomial regression modeling of the results indicated that limestone-based soils were more favorable to ticks than sandstone-based soils. The highest tick abundance was observed in forests, particularly among coniferous and mixed stands. We identified an effect of habitat time dynamics in forests and in wetlands: recent forests and current wetlands supported more ticks than stable forests and former wetlands, respectively. We observed a close association between tick abundance and the abundance of Cervidae, Leporidae, and birds. The tick-borne pathogens responsible for Lyme borreliosis, anaplasmosis, and hard tick relapsing fever showed specific habitat preferences and associations with specific animal families. Machine learning algorithms identified soil related variables as the best predictors of tick and pathogen abundance.

SCGB1D2 inhibits growth of Borrelia burgdorferi and affects susceptibility to Lyme disease.

Lyme disease is a tick-borne disease caused by bacteria of the genus Borrelia. The host factors that modulate susceptibility for Lyme disease have remained mostly unknown. Using epidemiological and genetic data from FinnGen and Estonian Biobank, we identify two previously known variants and an unknown common missense variant at the gene encoding for Secretoglobin family 1D member 2 (SCGB1D2) protein that increases the susceptibility for Lyme disease. Using live Borrelia burgdorferi (Bb) we find that recombinant reference SCGB1D2 protein inhibits the growth of Bb in vitro more efficiently than the recombinant protein with SCGB1D2 P53L deleterious missense variant. Finally, using an in vivo murine infection model we show that recombinant SCGB1D2 prevents infection by Borrelia in vivo. Together, these data suggest that SCGB1D2 is a host defense factor present in the skin, sweat, and other secretions which protects against Bb infection and opens an exciting therapeutic avenue for Lyme disease.

Antigenicity and immunogenicity of different morphological forms of Borrelia burgdorferi sensu lato spirochetes.

Borrelia burgdorferi sensu lato is a species complex of pleomorphic spirochetes, including species that cause Lyme disease (LD) in humans. In addition to classic spiral forms, these bacteria are capable of creating morphological forms referred to as round bodies and aggregates. The subject of discussion is their possible contribution to the persistence of infection or post-infection symptoms in LD. This study investigates the immunological properties of these forms by monitoring reactivity with early (n = 30) and late stage (n = 30) LD patient sera and evaluating the immune response induced by vaccination of mice. In patient sera, we found a quantitative difference in reactivity with individual morphotypes, when aggregates were recognized most intensively, but the difference was statistically significant in only half of the tested strains. In post-vaccination mouse sera, we observed a statistically significant higher reactivity with antigens p83 and p25 (OspC) in mice vaccinated with aggregates compared to mice vaccinated with spiral forms. The importance of the particulate nature of the antigen for the induction of a Th1-directed response has also been demonstrated. In any of morphological forms, the possibility of inducing antibodies cross-reacting with human nuclear and myositis specific/associated autoantigens was not confirmed by vaccination of mice.

Purification of Borrelia burgdorferi Outer Membrane Vesicles.

Bacterial outer membrane vesicles (OMVs) are spherical membrane constructs shed by gram-negative bacteria. OMVs produced by the Lyme disease pathogen Borrelia burgdorferi have been identified to contain such virulence factors as OspA, OspB, OspC, and genetic material. However, the function and possible pathogenicity of borrelial OMVs are still undetermined. Therefore, further research on borrelial OMVs is required, and for that a standard method for OMV purification is necessary. Here we describe a successful and reproducible purification of borrelial outer membrane vesicles using concentration, filtration, and ultracentrifugation steps.

Use of Specific Borrelia Phages as a New Strategy for Improved Diagnostic Tests.

The high failure rate of tick-borne infection (TBI)-related testing underscores the need for novel approaches that do not rely on serology and two-tier testing. Delayed diagnosis of TBIs, especially Borrelia infections, results in high healthcare costs and great suffering. There is a significant need for a reliable blood test that can aid in the diagnosis of Lyme disease, particularly when the current FDA-approved serological test is not sensitive enough to detect early Lyme patients who have not yet produced antibodies against Borrelia. Bacteriophages are viruses that specifically associate with their bacterial hosts, particularly prophages, bacteriophages residing in bacteria, and have proven to be tightly correlated with their bacterial hosts. They are poised to have wider applications as markers to detect bacteria, particularly in infectious disease. The gene of choice depends on the prevalence of phages within a particular group of bacteria. Phage genes that have been used as molecular markers to examine phage diversity include structural genes encoding the major capsid protein, the portal protein, the DNA polymerase, and the terminase. Borrelia species carry specific phage sequences that can be used as a proxy to identify the bacteria. Using phages as a proxy for bacteria is beneficial, as phages can be detected more easily than bacteria and can be used to bypass the cryptic and tissue-bound feature that typifies human Borrelia infections.We explored a completely new way of detecting Borrelia using Borrelia-specific bacteriophages as a diagnostic tool. Our detection method, patented by Phelix R&D and Leicester University (WO2018083491A1), could potentially transform infectious disease diagnostics through the innovative use of real-time PCR to target circulating bacteriophage DNA in blood from patients with Lyme disease. Firstly, this bacteriophage-based approach offers increased sensitivity since bacteriophages are typically present in five- to tenfold excess over bacterial cells, making it more accurate and sensitive than conventional bacteria-targeting PCR tests. One of the reasons bacteria-based PCR tests are frequently negative is due to the low bacterial concentration in the blood. Bacteriophage-based PCR surpasses this barrier and offers a direct test, as phages are part of bacteria's own genetic material, in contrast to all existing indirect tests (ELISA, Western BLOT, LTT/ELISPOT test). Secondly, a phage-based test can differentiate between different Lyme disease-causing and relapsing fever-causing Borrelia subtypes (B. burgdorferi s. l., B. miyamotoi, etc.), given that bacteriophages are indicators of bacterial identity. Finally, this test can detect Lyme disease in both early and late stages.

Establishing a Zebrafish Model for Borrelia burgdorferi Infection Using Immersion and Microinjection Methods.

Borrelia burgdorferi is the spirochetal bacterium that causes Lyme disease. Even though antimicrobial sensitivity of B. burgdorferi has been widely studied, there is still a need to develop an affordable, practical, high-throughput in vivo model which can be used to find effective antibiotic therapies, especially for the recently discovered persister and biofilm forms. Here, we describe the immersion and microinjection methods to introduce B. burgdorferi spirochetes into zebrafish larvae. The B. burgdorferi-zebrafish model can be produced by immersing 5-day post-fertilization (dpf) zebrafish in a B. burgdorferi culture, or by injecting B. burgdorferi into the hindbrain of zebrafish at 28 h post-fertilization (hpf). To demonstrate that B. burgdorferi indeed infect the fish, nested polymerase chain reaction (PCR), reverse transcription PCR (RT-PCR), live fluorescence imaging, histological staining, and wholemount immunohistochemical (IHC) methods can be used on B. burgdorferi-infected zebrafish.

Sleep fragmentation disrupts Lyme arthritis resolution in mice.

STUDY OBJECTIVES: Lyme arthritis is a common late-stage complication of infection by Borrelia burgdorferi, the agent of Lyme disease. Patients with Lyme arthritis report increased levels of sleep disturbance associated with pain. Using a mouse model of experimental Lyme arthritis, we investigated the effect of disrupted sleep on the development and resolution of joint inflammation. METHODS: Lyme arthritis-susceptible C3H/HeJ mice (n = 10/group) were infected with B. burgdorferi and were left either alone (control) or subjected to sleep fragmentation (SF). Arthritis development or resolution were monitored. The impact of SF on immune and inflammatory parameters such as arthritis severity scores, anti-borrelia antibody production, and bacterial clearance was measured. We also determined the effect of SF on arthritis resolution in C3H mice deficient in leukotriene (LT) B4 signaling (BLT1/2-/-) who display delayed Lyme arthritis resolution. RESULTS: SF had no significant impact on Lyme arthritis development or inflammatory parameters regardless of whether SF treatment began 1 week prior to or congruent with infection. However, initiation of SF at the peak of arthritis resulted in a significant delay in arthritis resolution as measured by joint edema, arthritis severity scores, and decreased bacterial clearance from the joint. This was accompanied by significant changes in joint cytokine transcription levels (e.g., increased TNFα and decreased IL-4). SF has no significant impact on Lyme arthritis resolution in the BLT1/2-/- mice. CONCLUSIONS: Poor sleep, especially near the peak of arthritis inflammation, may delay initiation of resolution programs possibly through altering cytokine production and host immune responses, leading to defects in spirochete clearance and prolonged disease.

Historical associations and spatiotemporal changes of pathogen presence in ticks in Canada: A systematic review.

BACKGROUND: Starting in the early 20th century, ticks and their pathogens have been detected during surveillance efforts in Canada. Since then, the geographic spread of tick vectors and tick-borne pathogens has steadily increased in Canada with the establishment of tick and host populations. Sentinel surveillance in Canada primarily focuses on Ixodes scapularis, which is the main vector of Borrelia burgdorferi, the bacterium causing Lyme disease. Other tick-borne pathogens, such as Anaplasma, Babesia, and Rickettsia species, have lower prevalence in Canada, but they are emerging or re-emerging in tick and host populations. AIMS/MATERIALS & METHODS: Here, we assessed the historical associations between tick vectors, hosts and pathogens and identified spatiotemporal clusters of pathogen presence in ticks in Canada using data extracted from the literature. RESULTS: Approximately one-third of ticks were infected with a pathogen, and these ticks were feeding primarily on bird and mammal hosts. B. burgdorferi was the most detected pathogen and I. scapularis harboured the greatest number of pathogens. We identified several spatial outliers of high pathogen presence in ticks in addition to five spatiotemporal clusters in southern Canada, all of which have long-established tick populations. Six spatiotemporal clusters of high pathogen presence in ticks were also identified based on surveillance method, with four clusters associated with passive surveillance and two clusters associated with active surveillance. DISCUSSION: Our review represents the first systematic assessment of the literature that identifies historical associations and spatiotemporal changes in tick-host-pathogen disease systems in Canada over broad spatial and temporal scales. CONCLUSION: As distinct spatiotemporal clusters were identified based on surveillance method, it is imperative that surveillance efforts employ standardized methods and data reporting to comprehensively assess the presence, spread and risk of tick-borne pathogens in tick and host populations.

Risk of haematologic cancers among individuals tested for Borrelia burgdorferi antibodies, and Borrelia burgdorferi seropositive individuals: a nationwide population-based matched cohort study.

OBJECTIVES: In a nationwide, matched cohort study, we aimed to investigate risks of haematologic cancers among individuals tested for Borrelia burgdorferi (Bb) antibodies, and among serum Bb seropositive individuals. METHODS: We identified all Bb seropositive individuals in Denmark (1993-2020) (n = 52 200) and constructed two age- and sex-matched comparison cohorts: (a) Bb seronegative controls (n = 104 400) and (b) background population controls (n = 261 000). We calculated short-term OR (aOR) (<1 month of study inclusion), and long-term hazard ratios (aHR) (>1 month after study inclusion) adjusted for age and sex. We stratified seropositive individuals on only Bb-IgM seropositive (n = 26 103), only Bb-IgG seropositive (n = 18 698), and Bb-IgM-and-IgG seropositive (n = 7399). RESULTS: Compared with the background population, individuals tested for Bb antibodies had increased short-term (aOR: 12.6, 95% CI: 10.1-15.6) and long-term (aHR: 1.3, 95% CI: 1.2-1.4) risk of haematologic cancers. The Bb seropositive individuals had no increased risk of haematologic cancers compared with those who tested negative for Bb, except that Bb-IgM-and-IgG seropositive individuals had increased long-term risk of chronic lymphatic leukaemia (aHR: 2.0, 95% CI: 1.2-3.4). DISCUSSION: Our results suggest that Bb antibody testing is included in the work-up of unspecific symptoms preceding diagnosis of haematologic cancers. Bb-IgM-and-IgG seropositivity was associated with a two-fold increased long-term risk of chronic lymphatic leukaemia, which warrants further investigation.

Structure of the Borrelia burgdorferi ATP-dependent metalloprotease FtsH in its functionally relevant hexameric form.

ATP-dependent proteases FtsH are conserved in bacteria, mitochondria, and chloroplasts, where they play an essential role in degradation of misfolded/unneeded membrane and cytosolic proteins. It has also been demonstrated that the FtsH homologous protein BB0789 is crucial for mouse and tick infectivity and in vitro growth of the Lyme disease-causing agent Borrelia burgdorferi. This is not surprising, considering B. burgdorferi complex life cycle, residing in both in mammals and ticks, which requires a wide range of membrane proteins and short-lived cytosolic regulatory proteins to invade and persist in the host organism. In the current study, we have solved the crystal structure of the cytosolic BB0789166-614, lacking both N-terminal transmembrane α-helices and the small periplasmic domain. The structure revealed the arrangement of the AAA+ ATPase and the zinc-dependent metalloprotease domains in a hexamer ring, which is essential for ATPase and proteolytic activity. The AAA+ domain was found in an ADP-bound state, while the protease domain showed coordination of a zinc ion by two histidine residues and one aspartic acid residue. The loop region that forms the central pore in the oligomer was poorly defined in the crystal structure and therefore predicted by AlphaFold to complement the missing structural details, providing a complete picture of the functionally relevant hexameric form of BB0789. We confirmed that BB0789 is functionally active, possessing both protease and ATPase activities, thus providing novel structural-functional insights into the protein, which is known to be absolutely necessary for B. burgdorferi to survive and cause Lyme disease.

Diversity and host specificity of Borrelia burgdorferi's outer surface protein C (ospC) alleles in synanthropic mammals, with a notable ospC allele U absence from mixed infections.

Interactions among pathogen genotypes that vary in host specificity may affect overall transmission dynamics in multi-host systems. Borrelia burgdorferi, a bacterium that causes Lyme disease, is typically transmitted among wildlife by Ixodes ticks. Despite the existence of many alleles of B. burgdorferi's sensu stricto outer surface protein C (ospC) gene, most human infections are caused by a small number of ospC alleles ["human infectious alleles" (HIAs)], suggesting variation in host specificity associated with ospC. To characterize the wildlife host association of B. burgdorferi's ospC alleles, we used metagenomics to sequence ospC alleles from 68 infected individuals belonging to eight mammalian species trapped at three sites in suburban New Brunswick, New Jersey (USA). We found that multiple allele ("mixed") infections were common. HIAs were most common in mice (Peromyscus spp.) and only one HIA was detected at a site where mice were rarely captured. ospC allele U was exclusively found in chipmunks (Tamias striatus), and although a significant number of different alleles were observed in chipmunks, including HIAs, allele U never co-occurred with other alleles in mixed infections. Our results suggest that allele U may be excluding other alleles, thereby reducing the capacity of chipmunks to act as reservoirs for HIAs.

Borrelia burgdorferi initiates early transcriptional re-programming in macrophages that supports long-term suppression of inflammation.

Borrelia burgdorferi (Bb), the causative agent of Lyme disease, establishes a long-term infection and leads to disease manifestations that are the result of host immune responses to the pathogen. Inflammatory manifestations resolve spontaneously despite continued bacterial presence, suggesting inflammatory cells become less responsive over time. This is mimicked by in vitro repeated stimulations, resulting in tolerance, a phenotypic subset of innate immune memory. We performed comparative transcriptional analysis of macrophages in acute and memory states and identified sets of Tolerized, Hyper-Induced, Secondary-Induced and Hyper-Suppressed genes resulting from memory induction, revealing previously unexplored networks of genes affected by cellular re-programming. Tolerized gene families included inflammatory mediators and interferon related genes as would be predicted by the attenuation of inflammation over time. To better understand how cells mediate inflammatory hypo-responsiveness, we focused on genes that could mediate maintenance of suppression, such as Hyper-Induced genes which are up-regulated in memory states. These genes were notably enriched in stress pathways regulated by anti-inflammatory modulators. We examined one of the most highly expressed negative regulators of immune pathways during primary stimulation, Aconitate decarboxylase 1 (Acod1), and tested its effects during in vivo infection with Bb. As predicted by our in vitro model, we show its inflammation-suppressive downstream effects are sustained during in vivo long-term infection with Bb, with a specific role in Lyme carditis.

Molecular surveillance reveals a potential hotspot of tick-borne disease in Yakeshi City, Inner Mongolia.

A molecular surveillance of tick-borne diseases was performed in Hulunbuir City, Inner Mongolia. A total of 149 ticks including three species (Ixodes persulcatus, Haemaphysalis concinna, and Dermacentor silvarum) were collected. As many as 11 tick-borne bacterial pathogens were identified in them. Some of them have high positive rates. For example, Candidatus Rickettsia tarasevichiae was detected with a high prevalence of 72.48%, while Candidatus Lariskella sp. was detected in 31.54% of ticks. For both Rickettsia raoultii and Anaplasma phagocytophilum, two distinct genotypes were identified based on their phylogenetic trees based on 16S rRNA, gltA, and groEL sequences. Remarkable genetic diversity was also observed for 16S and flaB genes of Borreliella garinii, an agent of Lyme disease. Rickettsia heilongjiangensis causing Far-Eastern spotted fever (2.68%, 4/149), Ehrlichia muris causing human ehrlichiosis (4.70%, 7/149), Borrelia miyamotoi causing relapsing fever (2.01%, 3/149), and Borreliella afzelii causing Lyme disease (2.01%, 3/149) were also detected. Additionally, a previously uncharacterized Anaplasma species closely related to Anaplasma ovis was identified. Herein we name it "Candidatus Anaplasma mongolica". Based on these results, we propose that Yakeshi City might be a potential hotspot of tick-borne diseases.

Molecular detection of Spirochetes and Borrelia burgdorferi in stray dogs of Nineveh province, Iraq.

Background: Borrelia burgdorferi is a Gram-negative bacterium that causes Lyme disease or borreliosis in domestic and wild animals, including dogs, with the possible transmission to humans. Aim: This study was conducted to investigate the infection rate of Spirochetes and B. burgdorferi in stray dogs in Nineveh province, Iraq. Methods: During the period from May to October (2022), a total of 55 stray dogs were selected randomly from different areas in Nineveh province, Iraq. Blood samples were collected from cephalic venous and tested molecularly using the conventional polymerase chain reaction technique. Results: The present study revealed that the total infection rates of Spirochetes and B. burgdorferi were 41.82% and 27.27%, respectively. Concerning age, values of infection rate, odds ratio, and relative risk of B. burgdorferi were increased significantly in dogs aged ? 4 months (42.86%, 3.505%, and 2.438%, respectively), while decreased in dogs of ? 1-3 (12.5%, 0.337% and 0.42%, respectively) and ? 3 (13.33%, 0.32% and 0.409%) years old when compared to dogs aged 5-12 months (27.27%, 1% and 1%, respectively). While concerning dogs sex, a significantly higher infection rate, odds ratio, and relative risk of B. burgdorferi were shown in females (32.56%, 5.495% and 6.792%, respectively) compared to males (8.33%, 0.182% and 0.147%, respectively). Conclusion: To the best of our knowledge, this represents the first Iraqi study on the prevalence of spirochetes, in particular B. burgdorferi, in stray dogs in Nineveh province (Iraq). However, additional studies of B. burgdorferi infection in other animals as well as vectors such as ticks in different geographic areas, appear necessary to detect variation in the distribution patterns of infection. In addition, owners and veterinarians should be aware of zoonotic diseases transmitted from wild and domestic animals, in particular those with tick-bite histories.

A chemosensory-like histidine kinase is dispensable for chemotaxis in vitro but regulates the virulence of Borrelia burgdorferi through modulating the stability of RpoS.

As an enzootic pathogen, the Lyme disease bacterium Borrelia burgdorferi possesses multiple copies of chemotaxis proteins, including two chemotaxis histidine kinases (CHK), CheA1 and CheA2. Our previous study showed that CheA2 is a genuine CHK that is required for chemotaxis; however, the role of CheA1 remains mysterious. This report first compares the structural features that differentiate CheA1 and CheA2 and then provides evidence to show that CheA1 is an atypical CHK that controls the virulence of B. burgdorferi through modulating the stability of RpoS, a key transcriptional regulator of the spirochete. First, microscopic analyses using green-fluorescence-protein (GFP) tags reveal that CheA1 has a unique and dynamic cellular localization. Second, loss-of-function studies indicate that CheA1 is not required for chemotaxis in vitro despite sharing a high sequence and structural similarity to its counterparts from other bacteria. Third, mouse infection studies using needle inoculations show that a deletion mutant of CheA1 (cheA1mut) is able to establish systemic infection in immune-deficient mice but fails to do so in immune-competent mice albeit the mutant can survive at the inoculation site for up to 28 days. Tick and mouse infection studies further demonstrate that CheA1 is dispensable for tick colonization and acquisition but essential for tick transmission. Lastly, mechanistic studies combining immunoblotting, protein turnover, mutagenesis, and RNA-seq analyses reveal that depletion of CheA1 affects RpoS stability, leading to reduced expression of several RpoS-regulated virulence factors (i.e., OspC, BBK32, and DbpA), likely due to dysregulated clpX and lon protease expression. Bulk RNA-seq analysis of infected mouse skin tissues further show that cheA1mut fails to elicit mouse tnf-α, il-10, il-1ß, and ccl2 expression, four important cytokines for Lyme disease development and B. burgdorferi transmigration. Collectively, these results reveal a unique role and regulatory mechanism of CheA1 in modulating virulence factor expression and add new insights into understanding the regulatory network of B. burgdorferi.

A unique borrelial protein facilitates microbial immune evasion.

IMPORTANCE: Lyme disease is a major tick-borne infection caused by a bacterial pathogen called Borrelia burgdorferi, which is transmitted by ticks and affects hundreds of thousands of people every year. These bacterial pathogens are distinct from other genera of microbes because of their distinct features and ability to transmit a multi-system infection to a range of vertebrates, including humans. Progress in understanding the infection biology of Lyme disease, and thus advancements towards its prevention, are hindered by an incomplete understanding of the microbiology of B. burgdorferi, partly due to the occurrence of many unique borrelial proteins that are structurally unrelated to proteins of known functions yet are indispensable for pathogen survival. We herein report the use of diverse technologies to examine the structure and function of a unique B. burgdorferi protein, annotated as BB0238-an essential virulence determinant. We show that the protein is structurally organized into two distinct domains, is involved in multiplex protein-protein interactions, and facilitates tick-to-mouse pathogen transmission by aiding microbial evasion of early host cellular immunity. We believe that our findings will further enrich our understanding of the microbiology of B. burgdorferi, potentially impacting the future development of novel prevention strategies against a widespread tick-transmitted infection.

Genome diversity of Borrelia garinii in marine transmission cycles does not match host associations but reflects the strains evolutionary history.

Borrelia burgdorferi sensu lato is a species complex of spirochetal bacteria that occupy different ecological niches which is reflected in their reservoir host- and vector-associations. Borrelia genomes possess numerous linear and circular plasmids. Proteins encoded by plasmid genes play a major role in host- and vector-interaction and are important for Borrelia niche adaptation. However, the plasmid composition and therewith the gene repertoire may vary even in strains of a single species. Borrelia garinii, one of the six human pathogenic species, is common in Europe (vector Ixodes ricinus), Asia (vector Ixodes persulcatus) and in marine birds (vector Ixodes uriae). For the latter, only a single culture isolate (Far04) and its genome were previously available. The genome was rather small containing only one circular and six linear plasmids with a notable absence of cp32 plasmids. To further investigate B. garinii from marine transmission cycles and to explore i) whether the small number of plasmids found in isolate Far04 is a common feature in B. garinii from marine birds and presents an adaptation to this particular niche and ii) whether there may be a correlation between genome type and host species, we initiated in vitro cultures from live I. uriae collected in 2017 and 2018 from marine avian hosts and their nests. Hosts included common guillemots, Atlantic Puffin, razorbill, and kittiwake. We obtained 17 novel isolates of which 10 were sequenced using Illumina technology, one also with Pacific Bioscience technology. The 10 genomes segregated into five different genome types defined by plasmid types (based on PFam32 loci). We show that the genomes of seabird associated B. garinii contain fewer plasmids (6-9) than B. garinii from terrestrial avian species (generally ≥10), potentially suggesting niche adaptation. However, genome type did not match an association with the diverse avian seabird hosts investigated but matched the clonal complex they originated from, perhaps reflecting the isolates evolutionary history. Questions that should be addressed in future studies are (i) how is plasmid diversity related to host- and/or vector adaptation; (ii) do the different seabird species differ in reservoir host competence, and (iii) can the genome types found in seabirds use terrestrial birds as reservoir hosts.

Skin microbiota secretomes modulate cutaneous innate immunity against Borrelia burgdorferi s.s.

In Lyme borreliosis, the skin constitutes a major interface for the host, the bacteria and the tick. Skin immunity is provided by specialized immune cells but also by the resident cells: the keratinocytes and the fibroblasts. Discoveries on the role of the microbiome in the modulation of skin inflammation and immunity have reinforced the potential importance of the skin in vector-borne diseases. In this study, we analyzed in vitro the interaction of human primary keratinocytes and fibroblasts with Borrelia burgdorferi sensu stricto N40 in presence or absence of bacterial commensal supernatants. We aimed to highlight the role of resident skin cells and skin microbiome on the inflammation induced by B. burgdorferi s.s.. The secretomes of Staphylococcus epidermidis, Corynebacterium striatum and Cutibacterium acnes showed an overall increase in the expression of IL-8, CXCL1, MCP-1 and SOD-2 by fibroblasts, and of IL-8, CXCL1, MCP-1 and hBD-2 in the undifferentiated keratinocytes. Commensal bacteria showed a repressive effect on the expression of IL-8, CXCL1 and MCP-1 by differentiated keratinocytes. Besides the inflammatory effect observed in the presence of Borrelia on all cell types, the cutaneous microbiome appears to promote a rapid innate response of resident skin cells during the onset of Borrelia infection.

Lyme borreliosis diagnosis: state of the art of improvements and innovations.

With almost 700 000 estimated cases each year in the United States and Europe, Lyme borreliosis (LB), also called Lyme disease, is the most common tick-borne illness in the world. Transmitted by ticks of the genus Ixodes and caused by bacteria Borrelia burgdorferi sensu lato, LB occurs with various symptoms, such as erythema migrans, which is characteristic, whereas others involve blurred clinical features such as fatigue, headaches, arthralgia, and myalgia. The diagnosis of Lyme borreliosis, based on a standard two-tiered serology, is the subject of many debates and controversies, since it relies on an indirect approach which suffers from a low sensitivity depending on the stage of the disease. Above all, early detection of the disease raises some issues. Inappropriate diagnosis of Lyme borreliosis leads to therapeutic wandering, inducing potential chronic infection with a strong antibody response that fails to clear the infection. Early and proper detection of Lyme disease is essential to propose an adequate treatment to patients and avoid the persistence of the pathogen. This review presents the available tests, with an emphasis on the improvements of the current diagnosis, the innovative methods and ideas which, ultimately, will allow more precise detection of LB.