Rapid clearance of Borrelia burgdorferi from the blood circulation

Male C57BL/6J mice have higher presence and abundance of Borrelia burgdorferi in their ventral skin compared to female mice

Borrelia burgdorferi is a tick-borne spirochete that causes Lyme disease in humans. The host immune system controls the abundance of the spirochete in the host tissues. Recent work with immunocompetent Mus musculus mice strain C3H/HeJ found that males had a higher tissue infection prevalence and spirochete load compared to females. The purpose of this study was to determine whether host sex and acquired immunity interact to influence the prevalence and abundance of spirochetes in the tissues of the commonly used mouse strain C57BL/6. Wildtype (WT) mice and their SCID counterparts (C57BL/6) were experimentally infected with B. burgdorferi via tick bite. Ear biopsies were sampled at weeks 4, 8, and 12 post-infection (PI) and five tissues (left ear, ventral skin, heart, tibiotarsal joint of left hind leg, and liver) were collected at necropsy (16 weeks PI). The mean spirochete load in the tissues of the SCID mice was 260.4x higher compared to the WT mice. In WT mice, the infection prevalence in the ventral skin was significantly higher in males (40.0 %) compared to females (0.0 %), and the spirochete load in the rear tibiotarsal joint was significantly higher (4.3x) in males compared to females. In SCID mice, the spirochete load in the ventral skin was 200.0x higher in males compared to females, but there were no significant sex-specific difference in spirochete load in the other tissues (left ear, heart, tibiotarsal joint, or liver). Thus, the absence of acquired immunity greatly amplified the spirochete load in the ventral skin of male mice. It is important to note that the observed sex-specific differences in laboratory mice cannot be extrapolated to humans. Future studies should investigate the mechanisms underlying the male bias in the abundance of B. burgdorferi in the mouse skin.

Pathogenicity and virulence of Borrelia burgdorferi

Infection with Borrelia burgdorferi often triggers pathophysiologic perturbations that are further augmented by the inflammatory responses of the host, resulting in the severe clinical conditions of Lyme disease. While our apprehension of the spatial and temporal integration of the virulence determinants during the enzootic cycle of B. burgdorferi is constantly being improved, there is still much to be discovered. Many of the novel virulence strategies discussed in this review are undetermined. Lyme disease spirochaetes must surmount numerous molecular and mechanical obstacles in order to establish a disseminated infection in a vertebrate host. These barriers include borrelial relocation from the midgut of the feeding tick to its body cavity and further to the salivary glands, deposition to the skin, haematogenous dissemination, extravasation from blood circulation system, evasion of the host immune responses, localization to protective niches, and establishment of local as well as distal infection in multiple tissues and organs. Here, the various well-defined but also possible novel strategies and virulence mechanisms used by B. burgdorferi to evade obstacles laid out by the tick vector and usually the mammalian host during colonization and infection are reviewed.

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.

Single-tier point-of-care serodiagnosis of Lyme disease

Point-of-care (POC) serological testing provides actionable information for several difficult to diagnose illnesses, empowering distributed health systems. Accessible and adaptable diagnostic platforms that can assay the repertoire of antibodies formed against pathogens are essential to drive early detection and improve patient outcomes. Here, we report a POC serologic test for Lyme disease (LD), leveraging synthetic peptides tuned to be highly specific to the LD antibody repertoire across patients and compatible with a paper-based platform for rapid, reliable, and cost-effective diagnosis. A subset of antigenic epitopes conserved across Borrelia burgdorferi genospecies and targeted by IgG and IgM antibodies, were selected based on their seroreactivity to develop a multiplexed panel for a single-step measurement of combined IgM and IgG antibodies from LD patient sera. Multiple peptide epitopes, when combined synergistically using a machine learning-based diagnostic model, yielded a high sensitivity without any loss in specificity. We blindly tested the platform with samples from the U.S. Centers for Disease Control & Prevention (CDC) LD repository and achieved a sensitivity and specificity matching the lab-based two-tier results with a single POC test, correctly discriminating cross-reactive look-alike diseases. This computational LD diagnostic test can potentially replace the cumbersome two-tier testing paradigm, improving diagnosis and enabling earlier effective treatment of LD patients while also facilitating immune monitoring and surveillance of the disease in the community.

Borrelia miyamotoi in wild rodents from four different regions of Turkey

Borrelia miyamotoi is a tick-borne zoonotic agent that causes hard tick-borne relapsing fever, an emerging disease in humans. Some small mammalian and bird species are reported to be reservoirs of B. miyamotoi. This study aims to examine Borrelia species present in rodents captured from rural areas of Turkey. Blood samples of rodents were initially screened with Borrelia 16S rRNA qPCR. The Borrelia flaB gene was subsequently amplified by conventional PCR, after which all positive samples were sequenced. Borrelia miyamotoi was observed in nine out of 536 blood samples (1.7%) collected from wild rodents. Phylogenetic analysis showed that all positive samples belonged to the European genotype clade of B. miyamotoi. PCR positivity was 5.3%, 3.7%, and 1.8% in Apodemus uralensis, Apodemus flavicollis, and Myodes glareolus, respectively. Borrelia burgdorferi sensu lato that causes Lyme borreliosis in humans could not be detected in the rodents. In this study, presence of B. miyamotoi DNA is reported for the first time in rodents in Turkey.

Differential detection of tick-borne pathogens in human platelets and whole blood using microfluidic PCR

The tick-borne pathogens (TBPs) with adhesive phenotype can use platelets for dissemination and colonization of distant tissues and organs, and it has been shown that they can be found concentrated in the platelet fraction of blood. This study shows the differential presence of TBPs in samples of human platelet fraction (n = 68), whole blood samples (n = 68) and ticks collected (n = 76) from the same individuals, using an unbiased high-throughput pathogen detection microfluidic system. The clinical symptoms were characterized in enrolled patients. In patients with suspected TBP infection, serological assays were conducted to test for the presence of antibodies against specific TBPs. Tick species infesting humans were identified as Ixodes ricinus, Dermacentor reticulatus, and Haemaphysalis punctata. Eight patients developed local skin lesions at the site of the tick bite including non-specific lesions, itching sensation at the lesion site, and eschar. Most common TBPs detected in platelet fraction were Borrelia spielmanii and Rickettsia sp., followed by Borrelia afzelii and Anaplasma phagocytophilum. Multiple infections with three TBPs were detected in platelet fraction. In whole blood, most common TBPs detected were Anaplasma spp. and A. phagocytophilum, followed by Rickettsia spp. and B. afzelii. In ticks, the most common TBP detected was Rickettsia spp., followed by Borrelia spp. and Anaplasma spp. Overall, nine different pathogens with variable prevalence were identified using species-specific primers, and the most common was Rickettsia helvetica. In three patients, there were no coincidences between the TBPs detected in whole blood and tick samples. Only in one patient was detected A. phagocytophilum in both, whole blood and tick samples. These results suggest the unequal detection of TBPs in whole blood, platelet fraction and ticks collected, from the same individual. The results justify the use of both whole blood and platelet fraction for molecular diagnosis of TBPs in patients.

Neuropsychiatric Symptoms and Tick-Borne Diseases

In North America, Lyme disease (LD) is primarily caused by the spirochetal bacterium Borrelia burgdorferi, transmitted to humans by Ixodes species tick bites, at an estimated rate of 476,000 patients diagnosed per year. Acute LD often manifests with flu-like symptoms and an expanding rash known as erythema migrans (EM) and less often with neurologic, neuropsychiatric, arthritic, or cardiac features. Most acute cases of Lyme disease are effectively treated with antibiotics, but 10-20% of individuals may experience recurrent or persistent symptoms. This chapter focuses on the neuropsychiatric aspects of Lyme disease, as these are less widely recognized by physicians and often overlooked. Broader education about the potential complexity, severity, and diverse manifestations of tick-borne diseases is needed.

Exploration of the induced cytokine responses in European Lyme neuroborreliosis: A longitudinal cohort study

Lyme neuroborreliosis (LNB) is a prevalent tick-borne disease in Europe caused by Borrelia burgdorferi sensu lato complex. Slightly suppressed induced Th1- and Th17-responses are seen at diagnosis. The induced immune response following antibiotic therapy is unknown. We hypothesized that the immune responses normalize after completing antibiotic treatment. An observational longitudinal cohort study investigating the induced immune response in adult patients with LNB at diagnosis, three and six months after treatment. Whole blood was added to three TruCulture® (Myriad RBM, Austin, USA) tubes each containing one stimulation. An additional TruCulture® tube was without stimulation representing the in vivo activation of blood immune cells. Nine cytokines were measured using Luminex (LX200, R&D Systems, BIO-Teche LTD). Changes in immune response were analyzed with linear mixed model including follow-up as categorical fixed effect. A total of 21 patients with 55 samples were included. All had clinical improvement, but 5/21 patients reported residual symptoms after six months. The non-induced release of IL-17A and IL-1β increased significantly from diagnosis to six month follow-up. Six months after treatment only IFN-α and TNF-α were below the reference range. Minor variations in the induced immune responses were seen during the study period. Th1- and Th17-responses continued to be low with low IFN-γ, IL-12p40, and IL-17A in multiple stimulations. Overall little dynamic was observed. The changes in the cytokine responses are most likely not linked to LNB pathogenesis and our results do not support the implementation of TruCulture® in the diagnostics or follow-up of LNB.

Infection and seroprevalence of Borrelia persica in domestic cats and dogs in Israel

Background

Relapsing fever borreliosis is an infectious disease caused by bacteria of the genus Borrelia, inflicting recurrent episodes of fever and spirochetemia in humans. Borrelia persica, the causative agent of relapsing fever in Israel, is prevalent over a broad geographic area that extends from India to Egypt. It is transmitted by the soft tick Ornithodoros tholozani and causes disease in humans as well as domestic cats and dogs. The goal of this study was to survey domestic dogs and cats in Israel for infection with B. persica.

Methods

Blood, sera and demographic and clinical data were collected from dogs and cats brought for veterinary care in central Israel. PCR followed by DNA sequencing was used to detect B. persica DNA in blood samples, and an enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies reactive with B. persica antigens in sera from the same animals. This is the first serological survey of B. persica in dogs and the first survey for antibodies reactive with a relapsing fever Borrelia sp. in cats globally.

Results

Four of the 208 dogs (1.9%) and three of 103 cats (2.9%) sampled were positive by PCR for B. persica DNA, and 24 dogs (11.5%) and 18 cats (17.5%) were seropositive for B. persica antigen by ELISA. The ratio between PCR-positivity and seropositivity in both the dog and cat populations was 1:6. All four PCR-positive dogs and two of three PCR-positive cats were seronegative, suggesting a probable recent infection. Thrombocytopenia showed significant association with seropositivity in dogs (P = 0.003). In cats, anemia had a significant association with seropositivity (P = 0.0001), and thrombocytopenia was associated with the combined prevalence of seropositivity or PCR-positivity (P = 0.022).

Conclusions

Borrelia persica infection is more prevalent and widespread in domestic canine and feline populations in Israel than previously thought. Dogs and cats may play a role as reservoirs and sentinels for human infection. Precautions should be taken to prevent transfusion-transmitted infection between blood donor and recipient animals.

Graphic Abstract

Role of NK-Like CD8+ T Cells during Asymptomatic Borrelia burgdorferi Infection

Lyme disease (LD) due to Borrelia burgdorferi is the most prevalent vector-borne disease in the United States. There is a poor understanding of how immunity contributes to bacterial control, pathology, or both during LD. Dogs in an area of endemicity were screened for B. burgdorferi and Anaplasma exposure and stratified according to seropositivity, presence of LD symptoms, and doxycycline treatment. Significantly elevated serum interleukin-21 (IL-21) and increased circulating CD3⁺ CD94⁺ lymphocytes with an NK-like CD8⁺ T cell phenotype were predominant in asymptomatic dogs exposed to B. burgdorferi. Both CD94⁺ T cells and CD3^- CD94⁺ lymphocytes, corresponding to NK cells, from symptomatic dogs expressed gamma interferon (IFN-γ) at a 3-fold-higher frequency upon stimulation with B. burgdorferi than the same subset among endemic controls. Surface expression of activating receptor NKp46 was reduced on CD94⁺ T cells from LD, compared to cells after doxycycline treatment. A higher frequency of NKp46-expressing CD94⁺ T cells correlated with significantly increased peripheral blood mononuclear cell (PBMC) cytotoxic activity via calcein release assay. PBMCs from dogs with symptomatic LD showed significantly reduced killing ability compared with endemic control PBMCs. An elevated NK-like CD8⁺ T cell response was associated with protection against development of clinical LD, while excess IFN-γ was associated with clinical disease.

Lyme arthritis: linking infection, inflammation and autoimmunity

Infectious agents can trigger autoimmune responses in a number of chronic inflammatory diseases. Lyme arthritis, which is caused by the tick-transmitted spirochaete Borrelia burgdorferi, is effectively treated in most patients with antibiotic therapy; however, in a subset of patients, arthritis can persist and worsen after the spirochaete has been killed (known as post-infectious Lyme arthritis). This Review details the current understanding of the pathogenetic events in Lyme arthritis, from initial infection in the skin, through infection of the joints, to post-infectious chronic inflammatory arthritis. The central feature of post-infectious Lyme arthritis is an excessive, dysregulated pro-inflammatory immune response during the infection phase that persists into the post-infectious period. This response is characterized by high amounts of IFNγ and inadequate amounts of the anti-inflammatory cytokine IL-10. The consequences of this dysregulated pro-inflammatory response in the synovium include impaired tissue repair, vascular damage, autoimmune and cytotoxic processes, and fibroblast proliferation and fibrosis. These synovial characteristics are similar to those in other chronic inflammatory arthritides, including rheumatoid arthritis. Thus, post-infectious Lyme arthritis provides a model for other chronic autoimmune or autoinflammatory arthritides in which complex immune responses can be triggered and shaped by an infectious agent in concert with host genetic factors.

Pathogens detected in the tick Haemaphysalis concinna in Western Poland: known and unknown threats

In recent years, a new focus of the relict tick Haemaphysalis concinna was discovered in Western Poland, near Wolsztyn, Greater Poland voivodeship. This species may play an important role in the circulation of pathogens of medical and veterinary importance. In the present study we tested 880 juvenile ticks collected from rodents, including 427 H. concinna, 443 Ixodes ricinus and 10 Dermacentor reticulatus for three of the most common pathogens vectored by ticks in Poland: Rickettsia and Babesia spp. and Borrelia burgdorferi s.l. Additionally, molecular techniques were applied for accurate identification of tick host species (the voles Microtus and Alexandromys). Our study found differences in the range and prevalence of vectored pathogens between the three tick species. DNA of all three pathogens was found in I. ricinus. In juvenile H. concinna, DNA of Babesia microti, Borrelia afzelii and Rickettsia sp. was identified. Moreover, DNA of a new unnamed Babesia species related to B. crassa, was found in two H. concinna nymphs. This genotype of Babesia was previously identified in H. concinna in the Far East and then in Central Europe. DNA of Rickettsia raoulti and B. afzelii was detected in D. reticulatus nymphs. Among rodent hosts, Alexandromys oeconomus seems to be host of the highest significance for juvenile tick stages and was the only host species with B. afzelii detected in blood samples. Using phylogenetic methods, we confirmed a clear division between rodents from the genera Microtus and Alexandromys. Moreover, we found that A. oeconomus trapped in Western Poland clustered with a Central European A. oeconomus allopatric phylogroup.

Targeting Multicopy Prophage Genes for the Increased Detection of Borrelia burgdorferi Sensu Lato (s.l.), the Causative Agents of Lyme Disease, in Blood

The successful treatment of Lyme disease (LD) is contingent on accurate diagnosis. However, current laboratory detection assays lack sensitivity in the early stages of the disease. Because delayed diagnosis of LD incurs high healthcare costs and great suffering, new highly sensitive tests are in need. To overcome these challenges, we developed an internally controlled quantitative PCR (Ter-qPCR) that targets the multicopy terminase large subunit (terL) gene encoded by prophages that are only found in LD-causing bacteria. The terL protein helps phages pack their DNA. Strikingly, the detection limit of the Ter-qPCR was analytically estimated to be 22 copies and one bacterial cell in bacteria spiked blood. Furthermore, significant quantitative differences was observed in terms of the amount of terL detected in healthy individuals and patients with either early or late disease. Together, the data suggests that the prophage-targeting PCR has significant power to improve success detection for LD. After rigorous clinical validation, this new test could deliver a step-change in the detection of LD. Prophage encoded markers are prevalent in many other pathogenic bacteria rendering this approach highly applicable to bacterial identification in general.