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Transcriptional response patterns of Chlamydophila psittaci in different in vitro models of persistent infection
Stefanie Goellner1, Evelyn Schubert, Elisabeth Liebler-Tenorio
1Institute of Bacterial Infections and Zoonoses, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Jena, Germany.
Abstract:
The obligatory intracellular bacterium Chlamydophila psittaci is the causative agent of psittacosis in birds and humans. The capability of this zoonotic pathogen to develop a persistent phase is likely to play a role in chronicity of infections, as well as in failure of antibiotic therapy and immunoprophylaxis. To elucidate three different in vitro models for transition of C. psittaci to persistence (iron depletion, penicillin G treatment, and gamma interferon [IFN-gamma] exposure), a set of 27 genes was examined by mRNA expression analysis using quantitative real-time PCR. While the phenotypical characteristics were the same as in other chlamydiae, i.e., aberrant morphology of reticulate bodies, loss of cultivability, and rescue of infectivity upon removal of inducers, the transcriptional response of C. psittaci to persistence-inducing factors included several new and distinctive features. Consistent downregulation of membrane proteins, chlamydial sigma factors, cell division protein, and reticulate body-elementary body differentiation proteins from 24 h postinfection onward proved to be a general feature of C. psittaci persistence. However, other genes displayed considerable variations in response patterns from one model to another, which suggests that there is no persistence model per se. In contrast to results for Chlamydia trachomatis, late shutdown of essential genes in C. psittaci was more comprehensive with IFN-gamma-induced persistence, which is probably due to the absence of a functional tryptophan synthesis operon.
Insights
Chlamydophila psittaci can enter a persistent phase, complicating treatment. Gene expression analysis revealed distinct transcriptional patterns during persistence, differing between various in vitro models.
Area of Science:
- Microbiology
- Bacteriology
- Infectious Diseases
Background:
- Chlamydophila psittaci is an intracellular bacterium causing psittacosis in birds and humans.
- Persistent infections by C. psittaci may lead to chronic illness and treatment failure.
Purpose of the Study:
- To investigate the in vitro transition of C. psittaci to a persistent state.
- To analyze the transcriptional response of C. psittaci under different persistence-inducing conditions.
Main Methods:
- Three in vitro models were used: iron depletion, penicillin G treatment, and gamma interferon (IFN-γ) exposure.
- mRNA expression analysis of 27 genes was performed using quantitative real-time PCR.
Main Results:
- C. psittaci exhibited typical chlamydial persistence characteristics: altered morphology, loss of cultivability, and regain of infectivity upon inducer removal.
- A general feature of persistence was the downregulation of membrane proteins, sigma factors, cell division, and differentiation proteins.
- Gene expression patterns varied significantly across the different persistence models, indicating no single universal model.
- IFN-γ-induced persistence showed a more comprehensive shutdown of essential genes compared to Chlamydia trachomatis, likely due to the lack of a tryptophan synthesis operon.
Conclusions:
- C. psittaci persistence involves specific transcriptional changes, with variations depending on the inducing factor.
- The findings highlight the complexity of C. psittaci persistence and suggest distinct mechanisms may be involved.
- Understanding these mechanisms is crucial for developing effective therapeutic strategies against psittacosis.
