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Chlamydial elementary bodies are translocated on the surface of epithelial cells
S Campbell1, J Larsen, S T Knight
1Department of Obstetrics and Gynaecology, Royal Infirmary, University of Glasgow, United Kingdom. steven.campbell@udcf.gla.ac.uk
Abstract:
Infection of eukaryotic cells by intracellular pathogens such as chlamydia requires attachment to the host cell surface. Chlamydia are thought to attach to the tips of microvilli in confluent monolayers of polarized cells. In vitro evidence obtained from migrating epithelial cells suggested that during healing the route of pathogen uptake might be different from that in intact epithelia. The small size of infectious chlamydial elementary bodies (approximately 0.3 microm in diameter) has made it difficult, however, to analyze the early stages of pathogen-host cell interaction in living cells by conventional microscopy. Contrast-enhanced video microscopy was therefore used to examine the earliest events of host-pathogen interaction and test the hypothesis that chlamydial uptake into the healing epithelia can involve translocation over the host cell surface. Observations made in this way were validated by scanning and immunofluorescence microscopy. These studies revealed two fates for chlamydiae taken onto the lamellipodial surface: 1) some chlamydiae were moved in a random fashion on the cell surface or were detached into the culture medium, whereas 2) other chlamydiae were translocated across the lamellipodium in a highly directed manner toward the microvillous perinuclear region. After internalization, these latter chlamydiae were found within intracellular inclusions, which demonstrated that this route of attachment and location of uptake resulted in productive growth.
Insights
Chlamydia infection involves host cell attachment. New research shows chlamydial elementary bodies can translocate across healing epithelial cell surfaces for productive infection.
Area of Science:
- Microbiology
- Cell Biology
- Pathogen-Host Interactions
Background:
- Intracellular pathogens like Chlamydia require host cell attachment for infection.
- Conventional microscopy struggles to visualize early Chlamydia-host interactions due to elementary body size.
- Healing epithelia may offer alternative pathogen uptake routes compared to intact tissues.
Purpose of the Study:
- To investigate early host-pathogen interactions during Chlamydia infection in healing epithelia.
- To test the hypothesis that Chlamydia uptake involves translocation over the host cell surface.
- To analyze the route and fate of Chlamydia elementary bodies on migrating epithelial cells.
Main Methods:
- Utilized contrast-enhanced video microscopy to observe early host-pathogen interactions in living cells.
- Employed scanning and immunofluorescence microscopy for validation of observations.
- Examined the behavior of Chlamydia elementary bodies on the surface of healing epithelial cells.
Main Results:
- Two distinct fates were observed for Chlamydiae on the lamellipodial surface: random movement/detachment or directed translocation.
- Chlamydiae translocated across the lamellipodium were directed towards the perinuclear region.
- Internalized Chlamydiae were found within intracellular inclusions, indicating productive growth.
Conclusions:
- Chlamydial uptake into healing epithelia can occur via translocation across the cell surface.
- This translocation route leads to productive infection within intracellular inclusions.
- The study reveals a novel mechanism for Chlamydia entry into migrating host cells.