The Trichomonas vaginalis pseudocyst is a viable cell stage with a distinct transcriptome and an intact membrane
- 1Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- 2Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
- 3Department of Biomedical Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
Abstract
Trichomonas vaginalis is the causative agent of trichomoniasis, the most common non-viral sexually transmitted infection (STI). Despite its prevalence, low levels of public knowledge and research funding and the absence of T. vaginalis screening or control programs have led to its categorization as a “neglected” STI. Unlike other STIs in the USA, prevalence increases with age, peaking among individuals in their 40s. Both a motile trophozoite stage and a non-motile pseudocyst state have been described for the parasite, although it was long debated whether the latter is a quiescent stage or a degenerate form on its way to cell death. Here we characterize the T. vaginalis pseudocyst by flow cytometry, membrane integrity assays, transcriptomics, and reversion studies. Pseudocysts were induced by culturing trophozoites in acidic media or in iron depleted media, with a variety of resulting survival rates. Flow cytometry studies showed that pseudocysts have intact cell membranes and express phosphatidylserine on their cell surface. Fluorescence-activated cell sorting studies also identified distinct sub-populations of parasites, revealing the importance of using pure live pseudocyst cultures in reversion studies. Pseudocysts were transcriptionally active for several days and had consistent subsets of genes with increased expression compared to trophozoites, although decreased transcription of genes involved in metabolism. Comparative transcriptomics of pseudocysts and trophozoites of two T. vaginalis strains revealed distinct cell states. Combined, our results provide evidence that the pseudocyst cell state is a stress-induced stage of T. vaginalis that can remain viable for days, with implications for a role in persistent infections. Author summary: The sexually transmitted parasite Trichomonas vaginalis has two well-known cell forms: a free-swimming, flagellated trophozoite and an amoeboid form adhered to host epithelia. A third morphology, the pseudocyst, has been described, but it is unclear whether this is a quiescent stage capable of facilitating persistent infections, or a degenerate form indicating cell death. Here we describe experiments revealing that pseudocysts have overall decreased gene expression compared to trophozoites but exhibit stage-specific gene transcription and plasma membrane integrity for days. Moreover, pseudocysts maintain externalized phosphatidylserine for multiple days. Taken together, our results suggest that pseudocysts are a viable cell stage in T. vaginalis distinct from cell death. Further research into pseudocysts and particularly their interactions with host immune cells is needed to reveal what role they may play in T. vaginalis pathogenesis and persistent or asymptomatic infections.
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BibTeX
@article{shiratori2026trichomonas,
title = {{The Trichomonas vaginalis pseudocyst is a viable cell stage with a distinct transcriptome and an intact membrane}},
author = {Mari Shiratori and Francisco Callejas-Hernández and Jordan C. Orosco and Steven A. Sullivan and Carlos Carmona Fontaine and Jane M. Carlton},
journal = {PLOS Pathogens},
year = {2026},
month = oct,
doi = {10.1371/journal.ppat.1014739},
url = {https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014739},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The Trichomonas vaginalis pseudocyst is a viable cell stage with a distinct transcriptome and an intact membrane
AU - Mari Shiratori
AU - Francisco Callejas-Hernández
AU - Jordan C. Orosco
AU - Steven A. Sullivan
AU - Carlos Carmona Fontaine
AU - Jane M. Carlton
PY - 2026
DA - 2026/10/26
JO - PLOS Pathogens
DO - 10.1371/journal.ppat.1014739
UR - https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014739
AB - Trichomonas vaginalis is the causative agent of trichomoniasis, the most common non-viral sexually transmitted infection (STI). Despite its prevalence, low levels of public knowledge and research funding and the absence of T. vaginalis screening or control programs have led to its categorization as a “neglected” STI. Unlike other STIs in the USA, prevalence increases with age, peaking among individuals in their 40s. Both a motile trophozoite stage and a non-motile pseudocyst state have been described for the parasite, although it was long debated whether the latter is a quiescent stage or a degenerate form on its way to cell death. Here we characterize the T. vaginalis pseudocyst by flow cytometry, membrane integrity assays, transcriptomics, and reversion studies. Pseudocysts were induced by culturing trophozoites in acidic media or in iron depleted media, with a variety of resulting survival rates. Flow cytometry studies showed that pseudocysts have intact cell membranes and express phosphatidylserine on their cell surface. Fluorescence-activated cell sorting studies also identified distinct sub-populations of parasites, revealing the importance of using pure live pseudocyst cultures in reversion studies. Pseudocysts were transcriptionally active for several days and had consistent subsets of genes with increased expression compared to trophozoites, although decreased transcription of genes involved in metabolism. Comparative transcriptomics of pseudocysts and trophozoites of two T. vaginalis strains revealed distinct cell states. Combined, our results provide evidence that the pseudocyst cell state is a stress-induced stage of T. vaginalis that can remain viable for days, with implications for a role in persistent infections. Author summary: The sexually transmitted parasite Trichomonas vaginalis has two well-known cell forms: a free-swimming, flagellated trophozoite and an amoeboid form adhered to host epithelia. A third morphology, the pseudocyst, has been described, but it is unclear whether this is a quiescent stage capable of facilitating persistent infections, or a degenerate form indicating cell death. Here we describe experiments revealing that pseudocysts have overall decreased gene expression compared to trophozoites but exhibit stage-specific gene transcription and plasma membrane integrity for days. Moreover, pseudocysts maintain externalized phosphatidylserine for multiple days. Taken together, our results suggest that pseudocysts are a viable cell stage in T. vaginalis distinct from cell death. Further research into pseudocysts and particularly their interactions with host immune cells is needed to reveal what role they may play in T. vaginalis pathogenesis and persistent or asymptomatic infections.
SN - 1553-7374
ER -