# Elucidating the mechanisms driving stage conversion in Toxoplasma gondii and Hammondia hammondi

> **NIH NIH F31** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2021 · $20,377

## Abstract

Project summary/abstract:
Elucidating the mechanisms driving stage conversion in Toxoplasma gondii and Hammondia
hammondi. Toxoplasma gondii is the world’s most common human parasitic infection. Although generally
asymptomatic, T. gondii can result in severe disease in utero and in immunocompromised individuals, and this
occurs due the presence of incurable cyst stages that can persist for the life of the host. T. gondii follows a
facultative homoxenous/heteroxenous life cycle, allowing it to infect new and diverse intermediate hosts with
orally infectious agents derived from both sexual (oocysts) and asexual reproduction (tissue cysts). This
phenomenon is unique to T. gondii among other coccidian Apicomplexans, including its closest relative
Hammondia hammondi. Despite extensive genomic similarity, H. hammondi is naturally avirulent and
possesses dramatic phenotypic differences in both gene expression and life cycle progression. These
differences suggest that despite possessing a similar genetic tool kit, H. hammondi and T. gondii differentially
utilize their genetic components to progress through their distinct life stages. I have found these two parasites
differentially develop tissue cysts and that tissue cyst formation in H. hammondi is not initiated by stressors
known to mediate this process in T. gondii. Together, this data suggests that these two species utilize different
mechanisms for stage progression. The goal of this proposal is to use this novel comparative system to
identify parasite and host components uniquely driving stage progression in T. gondii.

## Key facts

- **NIH application ID:** 10017644
- **Project number:** 5F31AI140529-02
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Sarah Louise Sokol
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $20,377
- **Award type:** 5
- **Project period:** 2020-01-01 → 2021-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10017644

## Citation

> US National Institutes of Health, RePORTER application 10017644, Elucidating the mechanisms driving stage conversion in Toxoplasma gondii and Hammondia hammondi (5F31AI140529-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10017644. Licensed CC0.

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