Tick-borne human disease cases are rising and outnumber mosquito-borne diseases in temperate climates. In North America, Ixodes scapularis ranks as the tick of highest public health concern as vector of Borrelia burgdorferi (Bb, an agent of Lyme disease), Anaplasma phagocytophilum (Ap, agent of human anaplasmosis), and Powassan or deer tick virus (agent of Powassan encephalitis), among others. In this resubmission, we will take advantage of our advances in rickettsial genomics to create rickettsiae able to express transgenes in ticks. Transgenic approaches are not yet available for ticks, in part hindered by their months- to year-long generation times. Our ability to generate aposymbiotic ticks coupled with our membrane feeder to reconstitute ticks with transformed R. buchneri and challenge them experimentally with Ap and Bb has opened unprecedented possibilities to dissect the interactions between ticks, their symbionts, and the pathogens they transmit. Symbionts play a fundamental role in shaping an arthropod's immune system. This highlights the need to understand how the tick immune system works when investigating the possibility of a paratransgenic strategy for tick-borne disease control. The tick immune system is not well understood, but Dr. Pedra, a co-investigator in the renewal project, has discovered fundamental differences from the insect immune system. The overarching hypotheses of our proposal are 1) that the rickettsial symbiont of I. scapularis (Rickettsia buchneri) plays a core role in regulating this tick's relationship with pathogens that determines its capacity to be a vector, and 2) that the tick immune system is an important intermediary in this triad. In order to dissect the interacting components, we will address the following aims:
Aim 1) Determine R. buchneri role in tick fitness, exclusion of other rickettsiae, susceptibility to Ap and Bb.
Aim 2) Prepare R. buchneri transposon mutants that are competent to colonize ticks using a Himar1 transposon designed for subsequent replacement using Recombinase Mediated Cassette Exchange (RMCE).
Aim 3) Replace the Himar1 transposon with an expression cassette encoding an anti-Ap Nanobody in colonization competent R. buchneri mutants; determine susceptibility of reconstituted I. scapularis to Ap.
Aim 4. 1) Determine whether R. buchneri presence in I. scapularis affects the activity of the IMD pathway.
Aim 4. 2) Identify host factors that alter immune signaling during colonization of I. scapularis by Ap and Bb in the presence or absence of R. buchneri. At the conclusion of the proposed project we will have gained detailed knowledge about R. buchneri as a provider of essential nutrients to ticks, as a factor required for maturation of a functional tick immune system, and as a controller of pathogen acquisition and transmission. We will further have defined the conditions that must be met to introduce a genetically modified R. buchneri into I. scapularis so that an effective paratransgenesis approach could be devised.
Symbionts of blood-sucking insects have been shown to control pathogen acquisition and transmission by priming the immune system of insects, and to provide essential nutrients, but nearly nothing is known for tick symbionts. In order to implement strategies to control tick-borne diseases based on tick symbionts that block pathogen tansmission, it is necessary to understand the role of symbionts in tick biology, and how symbionts regulate the response of ticks to tick-borne pathogens. We will elucidate the role of tick symbionts in provision of nutrients lacking in blood, in priming the tick immune system, and explore their interactions with tick-borne pathogens to identify new strategies for the prevention of tick-borne diseases.
| Shaw, Dana K; Tate, Ann T; Schneider, David S et al. (2018) Vector Immunity and Evolutionary Ecology: The Harmonious Dissonance. Trends Immunol 39:862-873 |
| McClure Carroll, Erin E; Wang, Xiaowei; Shaw, Dana K et al. (2018) p47 licenses activation of the immune deficiency pathway in the tick Ixodes scapularis. Proc Natl Acad Sci U S A : |
| McClure, Erin E; Chávez, Adela S Oliva; Shaw, Dana K et al. (2017) Engineering of obligate intracellular bacteria: progress, challenges and paradigms. Nat Rev Microbiol 15:544-558 |
| Oliva Chávez, Adela S; Shaw, Dana K; Munderloh, Ulrike G et al. (2017) Tick Humoral Responses: Marching to the Beat of a Different Drummer. Front Microbiol 8:223 |
| Kurtti, Timothy J; Burkhardt, Nicole Y; Heu, Chan C et al. (2016) Fluorescent Protein Expressing Rickettsia buchneri and Rickettsia peacockii for Tracking Symbiont-Tick Cell Interactions. Vet Sci 3: |
| Oliver, Jonathan D; Lynn, Geoffrey E; Burkhardt, Nicole Y et al. (2016) Infection of Immature Ixodes scapularis (Acari: Ixodidae) by Membrane Feeding. J Med Entomol 53:409-15 |
| Kurtti, Timothy J; Felsheim, Roderick F; Burkhardt, Nicole Y et al. (2015) Rickettsia buchneri sp. nov., a rickettsial endosymbiont of the blacklegged tick Ixodes scapularis. Int J Syst Evol Microbiol 65:965-70 |
| Oliver, Jonathan D; Chávez, Adela S Oliva; Felsheim, Roderick F et al. (2015) An Ixodes scapularis cell line with a predominantly neuron-like phenotype. Exp Appl Acarol 66:427-42 |
| Oliver, Jonathan D; Burkhardt, Nicole Y; Felsheim, Roderick F et al. (2014) Motility characteristics are altered for Rickettsia bellii transformed to overexpress a heterologous rickA gene. Appl Environ Microbiol 80:1170-6 |
| Wood, David O; Hines, Andria; Tucker, Aimee M et al. (2012) Establishment of a replicating plasmid in Rickettsia prowazekii. PLoS One 7:e34715 |
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