ABSTRACT
A gram-negative obligate intracellular bacterium, Chlamydia pneumoniae, is a common respiratory pathogen. Here, we examined the invasion and attachment of C. pneumoniae K6 into nonphagocytic HL epithelial cell line by manipulating host plasma membranes by using cholesterol-depleting methyl-beta-cyclodextrin (MßCD) and cholesterol-loading MßCD complexed cholesterol (chol-MßCD). The invasion was attenuated by MßCD-treatment while chol-MßCD augmented the attachment and invasion. In addition, the invasion was inhibited by cholesterol sequestering reagents, nystatin and filipin. Furthermore, exposure of host cells to sphingomyelinase inhibited the invasion. RNA interference was used to assay the role of clathrin and human scavenger receptor B, type I (SR-BI) in the entry of C. pneumoniae into A549 lung epithelial adenocarcinoma cells. In contrast to Chlamydia trachomatis L2, the entry of C. pneumoniae was found to be independent of clathrin. In addition, the entry was found to be SR-BI-independent, but interestingly, the chlamydial growth was attenuated in the SR-BI-silenced cells. These findings suggest that the attachment and invasion of C. pneumoniae into nonphagocytic epithelial cells is dependent on the formation of cholesterol- and sphingomyelin-rich plasma membrane microdomains, and the entry is a clathrin-independent process. In addition, our data indicate that SR-BI supports the growth of C. pneumoniae in epithelial cells.
Subject(s)
Bacterial Adhesion , Chlamydophila pneumoniae/pathogenicity , Endocytosis , Epithelial Cells/microbiology , Epithelial Cells/physiology , Cell Line , Cell Membrane/metabolism , Clathrin/antagonists & inhibitors , Clathrin/metabolism , Gene Silencing , Humans , Membrane Microdomains/metabolism , RNA Interference , Scavenger Receptors, Class B/antagonists & inhibitors , Scavenger Receptors, Class B/metabolismABSTRACT
In interleukin-10 knock out (IL-10 KO) mice, accelerated clearance of pulmonary Chlamydia pneumoniae infection was observed. On the other hand, the histopathological changes in lung tissue were more pronounced in IL-10 KO mice at all time points after infection and repeated infection than in the wild type mice. Both ex vivo induced antigen-specific proliferation as well as production of proinflammatory cytokines by splenocytes were higher in IL-10 KO mice than in WT mice. Also, intrapulmonary proinflammatory cytokine levels were higher in IL-10 KO mice than in the WT mice. The lack of anti-inflammatory action of IL-10 is likely to contribute to the enhanced clearance but severe inflammation in this experimental model.
Subject(s)
Chlamydia Infections/immunology , Chlamydia Infections/pathology , Chlamydophila pneumoniae/immunology , Interleukin-10/immunology , Pneumonia, Bacterial/immunology , Animals , Cell Proliferation , Chlamydia Infections/microbiology , Chlamydophila pneumoniae/pathogenicity , Chlamydophila pneumoniae/physiology , Cytokines/immunology , Disease Models, Animal , Female , Humans , Interleukin-10/genetics , Lung/immunology , Lung/microbiology , Lung/pathology , Mice , Mice, Inbred C57BL , Mice, Knockout , Pneumonia, Bacterial/microbiology , Pneumonia, Bacterial/pathologyABSTRACT
Vaccination against Chlamydia pneumoniae would be a beneficial strategy for either preventing or controlling infection by this human respiratory pathogen that also causes persistent infections. In the present study, we used recombinant Semliki Forest virus (rSFV) particles for delivering C. pneumoniae antigens major outer membrane protein (MOMP) or outer membrane protein 2 (Omp2) to the mice or applied the prime-boost technique, where mice were first primed with naked DNA and then boosted with the viral vector coding for the same proteins. Partial protection suggested by the reduced number of cultivable bacteria from the lungs of the challenged mice was seen in mice immunized by either method with MOMP expressing constructs. A significant protection was also achieved after DNA/rSFV immunization with Omp2. DNA priming followed by rSFV boosting induced a more prominent IFN-gamma production after challenge at the site of the infection in pulmonary and mediastinal cells.
