# Spiroplasma effects on Tsetse Flies

> **NIH NIH R21** · YALE UNIVERSITY · 2021 · $243,433

## Abstract

Tsetse flies are prominent vectors of pathogenic African trypanosomes, which cause socio-
economically devastating diseases. Tsetse reproduce by adenotrophic viviparity and depend upon
nutrients produced by their mutualist endosymbiont, Wigglesworthia. In addition to Wigglesworthia,
some tsetse species can harbor parasitic Wolbachia and facultative Sodalis and Spiroplasma. Our
studies on Wolbachia indicate that infection with the bacterium affects male reproductive physiology
and induces Cytoplasmic Incompatibility. Here, we address the molecular dialogue between tsetse
and its newly discovered endosymbiont Spiroplasma, which in other arthropods causes various
reproductive abnormalities. Spiroplasma infects only tsetse species within the Palpalis subgenus,
including Glossina fuscipes fuscipes (Gff), a prolific disease vector. Although its effects on tsetse
reproduction are unknown, Spiroplasma induces enhanced resistance to trypanosome infection in the
laboratory. We propose two research aims designed to dissect the impact of Spiroplasma infections
on 1) male reproductive physiology related to mating success, 2) female fecundity, and 3) tsetse-
Spiroplasma dialogue as it pertains to tsetse’s vector competence.
Aim 1. Spiroplasma effects on male reproductive fitness. We hypothesize that Spiroplasma
infections in male tsetse influence 1) MAG and testis gene expression, 2) spermatophore
composition, and 3) sperm fitness. To test our hypothesis, we will 1) establish Spiroplasma infected
and uninfected Gff lines, 2) perform comparative global gene expression analyses of gonads from Spi-
versus Spi+ males, 3) determine spermatophore contents from the females mated with Spi- or Spi+
males, and 4) evaluate Spiroplasma effects on sperm fitness.
Aim 2. Spiroplasma effects on parasite transmission dynamics. We hypothesize that
Spiroplasma infections diminish tsetse’s vector competence 1) indirectly by a) inducing host immune
responses or b) limiting nutrient availability for parasites, or 2) directly by expressing anti-
trypanosomal products. To test our hypothesis, we will: 1) profile global gene expression from GffSpi-
and GffSpi+ individuals, 2) determine nutritional status of trypanosome infected and uninfected GffSpi-
and GffSpi+ individuals and 3) test cultivated Spiroplasma for trypanolytic activity.
 Enhanced knowledge about the tsetse-Spiroplasma symbiosis will provide a foundation to
elucidate the mechanisms by which different reproductive endosymbionts influence host physiology.
Our results will have translational implications, as reducing either tsetse fecundity or vector
competence will directly reduce disease transmission. Finally, our results will be relevant and
applicable to other medically and agriculturally important insects in which symbiotic microbes persist.

## Key facts

- **NIH application ID:** 10287933
- **Project number:** 1R21AI163969-01
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Serap AKSOY
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $243,433
- **Award type:** 1
- **Project period:** 2021-06-24 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10287933

## Citation

> US National Institutes of Health, RePORTER application 10287933, Spiroplasma effects on Tsetse Flies (1R21AI163969-01). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10287933. Licensed CC0.

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