Chromosome and Linear Plasmid Sequences of a 2015 Human Isolate of the Tick-Borne Relapsing Fever Spirochete, Borrelia turicatae.
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SUBMITTER: Kingry LC
PROVIDER: S-EPMC4945796 | biostudies-literature | 2016 Jul
REPOSITORIES: biostudies-literature
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Chromosome and Linear Plasmid Sequences of a 2015 Human Isolate of the Tick-Borne Relapsing Fever Spirochete, Borrelia turicatae.
Kingry Luke C LC Batra Dhwani D Replogle Adam A Sexton Christopher C Rowe Lori L Stermole Benjamin M BM Christensen Anna M AM Schriefer Martin E ME
Genome announcements 20160714 4
The sequences of the complete linear chromosome and 7 linear plasmids of the relapsing fever spirochete Borrelia turicatae are presented in this report. The 925,547 bp of chromosome and 380,211 bp of plasmid sequence were predicted to contain a total of 1,131 open reading frames, with an average G+C content of 29.7%. ...[more]
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Project description:Borrelia turicatae is a causative agent of tick-borne relapsing fever (TBRF) in the subtropics and tropics of the United States and Latin America. Historically, B. turicatae was thought to be maintained in enzootic cycles in rural areas. However, there is growing evidence that suggests the pathogen has established endemic foci in densely populated regions of Texas. With the growth of homelessness in the state and human activity in city parks, it was important to implement field collection efforts to identify areas where B. turicatae and its vector circulate. Between 2017 and 2020 we collected Ornithodoros turicata ticks in suburban and urban areas including public and private parks and recreational spaces. Ticks were fed on naïve mice and spirochetes were isolated from the blood. Multilocus sequence typing (MLST) was performed on eight newly obtained isolates and included previously reported sequences. The four chromosomal loci targeted for MLST were 16S ribosomal RNA (rrs), flagellin B (flaB), DNA gyrase B (gyrB), and the intergenic spacer (IGS). Given the complexity of Borrelia genomes, plasmid diversity was also evaluated. These studies indicate that the IGS locus segregates B. turicatae into four genomic types and plasmid diversity is extensive between isolates. Furthermore, B. turicatae and its vector have established endemic foci in parks and recreational areas in densely populated settings of Texas.
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Project description:Direct amplification and sequencing of the 16S rRNA gene and a variable region of the flagellin gene from fetal liver-associated spirochetes belonging to the Borrelia parkeri-B. turicatae tick-borne relapsing fever spirochete group with a late-term abortion in a mare are described.
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Project description:Vector competence refers to the ability of an arthropod to acquire, maintain, and successfully transmit a microbial pathogen. Tick-borne relapsing fever (TBRF) spirochetes are globally distributed pathogens, and most species are transmitted by argasid ticks of the genus Ornithodoros. A defining characteristic in vector competence is an apparent specificity of a species of TBRF spirochete to a given tick species. In arid regions of the southern United States, Borrelia turicatae is the primary cause of TBRF. Interestingly, there are two populations of the tick vector distributed throughout this region. Ornithodoros turicata is a western population that ranges from California to Texas. There is a gap through Louisiana, Mississippi, and Alabama where the tick has not been identified. An isolated eastern population exists in Florida and was designated a subspecies, O. turicata americanus. A knowledge gap that exists is the poor understanding of vector competence between western and eastern populations of ticks for B. turicatae. In this study, we generated uninfected colonies of O. turicata that originated in Texas and Kansas and of O. turicataamericanus. B. turicatae acquisition, maintenance through the molt, and subsequent transmission were evaluated. Our findings revealed significant differences in murine infection after feeding infected O. turicata and O. turicataamericanus ticks on the animals. Interestingly, the salivary glands of both tick populations were colonized with B. turicatae to similar densities. Our results suggest that the salivary glands of the tick colonies assessed in this study impact vector competence of the evaluated B. turicatae isolates.IMPORTANCE Several knowledge gaps exist in the vector competence of various geographical populations of O. turicata that transmit B. turicatae A western population of this tick is distributed from California to Texas, and an eastern population exists in Florida. Utilizing western and eastern populations of the vector, we studied acquisition and transmission of two B. turicatae isolates. Regardless of the isolate used, infection frequencies were poor in mice after the eastern population feeding on them. Since salivary gland colonization is essential for B. turicatae transmission, these tissues were further evaluated. Interestingly, the salivary glands from the two populations were similarly colonized with B. turicatae. These findings suggest the role of tick saliva in the establishment of infection and that the salivary glands may be a bottleneck for successful transmission.
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Project description:Tick-borne relapsing fever is an infectious disease caused by Borrelia species and are primarily transmitted by Ornithodoros ticks. Prior work indicated that in vitro cultivated spirochetes remain infectious to mice by needle inoculation; however, the impact of laboratory propagation on the pathogens natural life cycle has not been determined. Our current study assessed the effect of serial cultivation on the natural tick-mammalian transmission cycle. First, we evaluated genomic DNA profiles from B. turicatae grown to 30, 60, 120, and 300 generations, and these spirochetes were used to needle inoculate mice. Uninfected nymphal ticks were fed on these mice and acquisition, transstadial maintenance, and subsequent transmission after tick bite was determined. Infection frequencies in mice that were fed upon by ticks colonized with B. turicatae grown to 30, 60, and 120 generations were 100%, 100%, and 30%, respectively. Successful infection of mice by tick feeding was not detected after 120 generations. Quantifying B. turicatae in tick tissues indicated that by 300 generations they no longer colonized the vector. The results indicate that in vitro cultivation significantly affects the establishment of tick colonization and murine infection. This work provides a foundation for the identification of essential genetic elements in the tick-mammalian infectious cycle.
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Project description:The relapsing fever spirochete Borrelia turicatae possesses a complex life cycle in its soft-bodied tick vector, Ornithodoros turicata. Spirochetes enter the tick midgut during a blood meal, and, during the following weeks, spirochetes disseminate throughout O. turicata. A population persists in the salivary glands allowing for rapid transmission to the mammalian hosts during tick feeding. Little is known about the physiological environment within the salivary glands acini in which B. turicatae persists. In this study, we examined the salivary gland transcriptome of O. turicata ticks and detected the expression of 57 genes involved in oxidant metabolism or antioxidant defences. We confirmed the expression of five of the most highly expressed genes, including glutathione peroxidase (gpx), thioredoxin peroxidase (tpx), manganese superoxide dismutase (sod-1), copper-zinc superoxide dismutase (sod-2), and catalase (cat) by reverse-transcriptase droplet digital polymerase chain reaction (RT-ddPCR). We also found distinct differences in the expression of these genes when comparing the salivary glands and midguts of unfed O. turicata ticks. Our results indicate that the salivary glands of unfed O. turicata nymphs are highly oxidative environments where reactive oxygen species (ROS) predominate, whereas midgut tissues comprise a primarily nitrosative environment where nitric oxide synthase is highly expressed. Additionally, B. turicatae was found to be hyperresistant to ROS compared with the Lyme disease spirochete Borrelia burgdorferi, suggesting it is uniquely adapted to the highly oxidative environment of O. turicata salivary gland acini.
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Project description:Relapsing fever is an infection characterized by peaks of spirochetemia attributable to antibody selection against variable serotypes. In the absence of B cells, serotypes cannot be cleared, resulting in persistent infection. We previously identified differences in spirochetemia and disease severity during persistent infection of severe combined immunodeficiency mice with isogenic serotypes 1 (Bt1) or 2 (Bt2) of Borrelia turicatae. To investigate this further, we studied pathogen load, clinical disease, cytokine/chemokine production, and inflammation in mice deficient in B (Igh6-/-) or B and T (Rag1-/-) cells persistently infected with Bt1 or Bt2. The results showed that Igh6-/- mice, despite lower spirochetemia, had a significantly aggravated disease course compared with Rag1-/- mice. Measurement of cytokines revealed a significant positive correlation between pathogen load and interleukin (IL)-10 in blood, brain, and heart. Bt2-infected Rag1-/- mice harbored the highest spirochetemia and, at the same time, displayed the highest IL-10 plasma levels. In the brain, Bt1, which was five times more neurotropic than Bt2, caused higher IL-10 production. Activated microglia were the main source of IL-10 in brain. IL-10 injected systemically reduced disease and spirochetemia. The results suggest IL-10 plays a protective role as a down-regulator of inflammation and pathogen load during infection with relapsing fever spirochetes.
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