# Development of a novel multipurpose model to propagate and study the tick transmission cycle of relapsing fever spirochetes from Eurasia.

> **NIH NIH R21** · BAYLOR COLLEGE OF MEDICINE · 2024 · $240,750

## Abstract

Project Summary
Relapsing fever (RF) spirochetes are a group of neglected vector-borne pathogens that are a significant cause
of child morbidity and mortality. The current approaches to grow and assess tick transmission of RF spirochetes
are impractical in resource limited settings where they are prevalent. For example, propagating spirochetes in
culture medium is expensive and labor intensive. Moreover, prolonged in vitro propagation in medium causes
DNA rearrangements of their already exceedingly complex genomes, and this results in diminished vector
colonization and pathogenesis. There is a critical need for cost effective practical approaches to grow and study
RF spirochetes from neglected regions of the globe. This project builds on our prior our publication reporting the
first isolation of Borrelia caucasica, which is part of the Persica species complex and is distributed through
Eurasia and the Middle East. Moreover, our recent advances RF spirochete genomics addressed a major
limitation in the field and resulted in complete chromosome and plasmid assembled and annotated genomes.
The genomics tools we developed can now be utilized to characterize a model for the Persica complex species.
Interestingly, historical literature suggested that embryonated chicken eggs (ECEs) could be infected with RF
spirochetes by tick bite and the bacteria grew in this system. However, at the time molecular and genomics
resources were not available to characterize this model and knowledge gaps remain about the pathogens
genomic stability in ECEs. Leveraging recent advances in RF spirochete genomics, the ECE model can now be
fully developed to study Persica complex species. In this study, two aims are proposed. The first aim is to utilize
genomics resources for RF spirochetes and evaluate plasmid diversity and identify unique plasmid markers of
B. caucasica isolates through a comparative genomic analysis. The first objective is to complete reference quality
genomes assemblies of B. caucasica isolates and perform a comparative genomics analysis to identify plasmid
markers. The second objective is to develop a panel of specific probes needed to evaluate plasmid retention and
rearrangements during the B. caucasica life cycle. In the second aim, we will assess genomic changes of B.
caucasica using the tick – ECE model. The first objective is to develop the B. caucasica model in ECEs and
evaluate spirochete growth, tick acquisition, and subsequent tick transmission of spirochetes to naïve eggs. The
second objective is to assess plasmid stability and the ability of B. caucasica to remain infectious after passage
through ECEs. The establishment of the ECE model will result in a cost-effective approach to amplify RF
spirochetes in the absence of culture medium. Moreover, the development of this model offers a practical system
to study the transmission cycle and vector competence of RF spirochetes in resource limited settings. With the
emergence and health burden of RF ...

## Key facts

- **NIH application ID:** 10881963
- **Project number:** 5R21AI176037-02
- **Recipient organization:** BAYLOR COLLEGE OF MEDICINE
- **Principal Investigator:** Job E Lopez
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $240,750
- **Award type:** 5
- **Project period:** 2023-07-05 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10881963

## Citation

> US National Institutes of Health, RePORTER application 10881963, Development of a novel multipurpose model to propagate and study the tick transmission cycle of relapsing fever spirochetes from Eurasia. (5R21AI176037-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10881963. Licensed CC0.

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