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Published on: August 11, 2012
Chlamydia trachomatis persistence in vitro: an overview
1Department of Microbiology, J H Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA. pbwyrick@mail.etsu.edu
Abstract:
Chlamydiae growing in target mucosal human epithelial cells in vitro can transition from their normal developmental cycle progression, alternating between infectious but metabolically inactive elementary bodies to metabolically active but noninfectious reticulate bodies (RBs) and back to elementary bodies, into a state of persistence. Persistence in vitro is defined as viable but noncultivable chlamydiae involving morphologically enlarged, aberrant, and nondividing RBs. The condition is reversible, yielding infectious elementary bodies after removal of the inducers, including penicillin, interferon-gamma, iron or nutrient starvation, concomitant herpes infection, or maturation of the host cell into its physiologically differentiated state. All aberrant RB phenotypes are not the same, owing to differing up- or down-regulated chlamydial gene sets and subsequent host responses. Although all persistence-inducing conditions exist in vivo, key questions include (1) whether or not aberrant chlamydial RBs occur in vivo during the alternating acute-silent chronic-acute chlamydial infection scenario that exists in infected patients and animals and (2) whether such aberrant RBs can contribute to prolonged, chronic inflammation, fibrosis, and scarring.
Insights
Chlamydia can enter a persistent state in human cells, characterized by non-dividing reticulate bodies (RBs). This reversible state may contribute to chronic inflammation and scarring in persistent chlamydial infections.
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Chlamydiae exhibit a biphasic developmental cycle involving infectious elementary bodies and replicative reticulate bodies (RBs).
- In vitro studies demonstrate Chlamydia's ability to enter a persistent state under various stress conditions.
Purpose of the Study:
- To investigate the occurrence and implications of persistent Chlamydial reticulate bodies (RBs) in vivo.
- To determine if aberrant RBs contribute to chronic inflammation and host tissue damage.
Main Methods:
- In vitro cultivation of Chlamydia in human epithelial cells.
- Induction of persistence using various stressors (e.g., antibiotics, host cell differentiation).
- Morphological and molecular characterization of persistent Chlamydial forms.
Main Results:
- Chlamydiae can enter a viable but noncultivable state in vitro, characterized by enlarged, aberrant, non-dividing RBs.
- Persistence is reversible upon removal of inducers, restoring infectious elementary bodies.
- Aberrant RB phenotypes vary based on gene expression and host response.
Conclusions:
- The in vitro persistence model provides insights into Chlamydial adaptability.
- Key questions remain regarding the in vivo relevance of aberrant RBs in chronic infections and associated pathologies like inflammation and fibrosis.
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