In vitro response of host cell to Chlamydia pneumoniae infection, an ultra structure investigation

Abstract

Background and objectives: Chlamydiae are obligate intracellular bacterial pathogens that share a unique developmental cycle. The cycle alternates between infectious extracellular elementary bodies (EBs) and metabolically active reticulate bodies (RBs), which multiply within intracellular vacuoles known as inclusions. Recent evidence has demonstrated that C. pneumoniae is present and persistent at active sites of infection and thus contributes to coronary artery and respiratory diseases, the leading causes of death in the developed world. To understand the process of Chlamydia infection, it is important to investigate the morphology of both normal and infected Hep-2 cells.
Materials and Methods: Hep-2 cell lines (ATCC CCL23 ) were obtained from the Virology Laboratory, King Abdulaziz University Hospital, Jeddah, Saudi Arabia. Cells were grown on cover-slip in shell vial at 37oC in 5% CO2 humidified atmosphere. Later C. pneumoniae were inoculated in the cell lines. The infected cells were scanned using transmission electron microscopy (TEM).
Results: TEM showed round shaped cells with a smooth surface. Some holdings were observed on the edges which are believed to be due to the fluidity of the cytoplasm membrane. The TEM micrograph revealed smooth membrane and typical eukaryotic undisturbed organelles. The morphology of C. pneumoniae, the reticulate bodies (RBs), the elementary bodies (EBs), and their diameter with loug axis were determined.
Conclusion: Despite the presence of inclusion bodies within the cytoplasm of the majority of the infected cells, an alternating period of host cell destruction and host cell proliferation was observed. We termed this phenomenon as unsuccessful infection (USI).