# Bradyzoite subtypes rule the crossroads of Toxoplasma development

## TL;DR

This study reveals that Toxoplasma bradyzoites in cysts are not uniform but consist of multiple subtypes with different developmental roles, which could help in understanding and treating chronic infections.

## Contribution

The discovery of multiple bradyzoite subtypes within Toxoplasma cysts and their distinct developmental pathways provides new insights into the parasite's life cycle.

## Key findings

- ME49EW cysts contain multiple bradyzoite subtypes with distinct developmental fates.
- Single-bradyzoite RNA-sequencing identified five major subtypes within the cysts.
- A crucial bradyzoite subtype in chronically infected mice is missing from a common in vitro model.

## Abstract

Toxoplasmosis is a major risk to chronically infected individuals, especially those who become immunocompromised. Although one-third of the globe is infected with Toxoplasma, no treatments prevent or eliminate cysts in part due to limited understanding of bradyzoite biology. The cyst is central to Toxoplasmosis, as transition from bradyzoites to tachyzoites drive pathology. In this study, we aim to understand the biology of bradyzoites prior to recrudescence and the developmental pathways they initiate. Here, we discover ME49EW cysts from infected mice harbor multiple bradyzoite subtypes with distinct fates. Purified subtypes exhibit defined developmental pathways in animals and in primary astrocytes. Single-bradyzoite RNA-sequencing reveals five major subtypes within cysts. We further show that a crucial subtype in chronically infected mice is absent from a widely used in vitro model of bradyzoite development. Altogether, this work establishes new foundational principles of Toxoplasma cyst development and reactivation that operate during the intermediate life cycle of Toxoplasma.

The authors investigate the heterogeneity of Toxoplasma bradyzoites prior to recrudescence. Tissue cysts from infected mice harbor multiple bradyzoite subtypes with distinct developmental fates as evidenced by single-bradyzoite RNAseq and FACS.