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The developmental cycle of Ehrlichia chaffeensis in vertebrate cells
Jian-zhi Zhang1, Vsevolod L Popov, Si Gao
1Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA.
Cellular Microbiology
|September 22, 2006
Summary
Ehrlichia chaffeensis exhibits a developmental cycle in mammalian cells. The dense-cored (DC) form enters host cells, transforming into reticulate cells (RC) that multiply before maturing back into DC.
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Ehrlichia chaffeensis is an obligate intracellular bacterium.
- It exists in two distinct morphological forms within mammalian host cells: dense-cored (DC) and reticulate cells (RC).
Purpose of the Study:
- To elucidate the distinct roles of Ehrlichia chaffeensis's dense-cored (DC) and reticulate cell (RC) forms in the host cell lifecycle.
- To characterize the developmental cycle and outer membrane protein expression during transformation between forms.
Main Methods:
- Electron microscopy was used to observe bacterial morphology and host cell interactions.
- Confocal microscopy analyzed outer membrane protein expression (p28 and gp120).
- TCID50 assays quantified the infectivity of different bacterial forms.
Main Results:
- Dense-cored (DC) cells attach to and enter host cells, while reticulate cells (RC) multiply intracellularly.
- RC express p28, transforming cells express both gp120 and p28, and mature DC express gp120.
- DC exhibit a 6 log10 higher TCID50 than RC, indicating greater infectivity.
Conclusions:
- Ehrlichia chaffeensis undergoes a developmental cycle involving distinct cellular forms.
- The DC form facilitates host cell entry, transitioning to the replicative RC form, which eventually matures back into infectious DC.
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