Chlamydia pneumoniae is an important human intracellular pathogen; however, the pathogenesis of C. pneumoniae infection is poorly understood, and the bacterial adherence mechanism to host cells is unknown. This study examined the role of glycosaminoglycans (GAGs) in the adhesion of C. pneumoniae to eukaryotic cells. Heparin and heparan sulfate were found to inhibit the attachment of C. pneumoniae to human epithelial cells. Reduction in infectivity resulted from the binding of heparin to the organism. Enzymatic removal of heparan sulfate moieties from the host cell surface led to a marked decrease in C. pneumoniae infectivity. Mutant CHO cell lines that were defective in heparan sulfate biosynthesis were less susceptible to C. pneumoniae infection than was the wild-type cell line. However, preincubation of the GAG-deficient CHO cells with exogenous heparin greatly increased infectivity.

The activation of primary human airway epithelial cells (HAECs) and of the bronchial epithelial cell line BEAS-2B by Chlamydia pneumoniae, an important respiratory pathogen, was characterized. A time-dependent enhanced release of interleukin (IL)-8 and prostaglandin-E(2) and an increased expression of the epithelial adhesion molecule intercellular adhesion molecule-1 (ICAM-1), followed by subsequent transepithelial migration of polymorphonuclear neutrophils (PMN), were also demonstrated. The transepithelial PMN migration could be blocked by an anti-ICAM-1 monoclonal antibody (MAb) but not by MAbs against IL-8. In addition, there was an enhanced C. pneumoniae-mediated activation of NF-kappaB within 30-60 min in HAECs and BEAS-2B, which was followed by increases in mRNA synthesis of IL-8, ICAM-1, and cyclooxygenase-2, with maximal effects occurring 2 h after infection. Thus, C. pneumoniae infects and activates HAECs and BEAS-2B and therefore may be able to trigger a cascade of pro- and anti-inflammatory reactions during chlamydial infections.

Chlamydia pneumoniae is an important obligate intracellular pathogen that replicates within an inclusion in the eukaryotic cell. The initial event of a chlamydial infection is the adherence to and subsequent uptake of the infectious elementary bodies (EBs) by the human cell. These processes require yet-unidentified bacterial and eukaryotic surface proteins. The GroEL1 protein, which exhibits a very strong antigenicity and in vitro can activate various eukaryotic cells, is a potential pathogenicity factor. We localized the protein during the infection process and found it in the inclusion but outside the chlamydial particles. GroEL1 was also localized on the surface of EBs, and the protein could be washed off the EBs. Latex beads coated with recombinantly produced GroEL1 (rGroEL1) bound in a dose-dependent manner to HEp-2 cells. Likewise, GroEL1, when expressed and displayed on the yeast cell surface, mediated adhesion to HEp-2 cells. Interestingly, the homologous GroEL2 and GroEL3 proteins showed no adhesive properties. Incubation of primary umbilical vein endothelial cells with soluble GroEL1 and GroEL1-coated latex beads activated the translocation of the general transcription factor NF-B into the nucleus. Finally, preincubation of HEp-2 cells with rGroEL1 significantly reduced subsequent infection with C. pneumoniae, although adhesion of infectious bacteria to eukaryotic cells was not affected. Taken together, these data support a role for extracellular GroEL1 in the establishment of the chlamydial infection.

Chlamydophila pneumoniae is an important respiratory pathogen. In this study we characterized C. pneumoniae strain TW183-mediated activation of human small airway epithelial cells (SAEC) and the bronchial epithelial cell line BEAS-2B and demonstrated time-dependent secretion of granulocyte macrophage colony-stimulating factor (GM-CSF) upon stimulation. TW183 activated p38 mitogen-activated protein kinase (MAPK) in epithelial cells. Kinase inhibition by SB202190 blocked Chlamydia-mediated GM-CSF release on mRNA and protein levels. In addition, the chemical inhibitor as well as dominant-negative mutants of p38 MAPK isoforms p38alpha, beta2, and gamma inhibited C. pneumoniae-related NF-kappaB activation. In contrast, blocking of MAPK ERK, c-Jun kinase/JNK, or PI-3 Kinase showed no effect on Chlamydia-related epithelial cell GM-CSF release. Ultraviolet-inactivated pathogens as compared with viable bacteria induced a smaller GM-CSF release, suggesting that viable Chlamydiae were only partly required for a full effect. Presence of an antichlamydial outer membrane protein-A (OmpA) antibody reduced and addition of recombinant heat-shock protein 60 from C. pneumoniae (cHsp60, GroEL-1)-enhanced GM-CSF release, suggesting a role of these proteins in epithelial cell activation. Our data demonstrate that C. pneumoniae triggers an early proinflammatory signaling cascade involving p38 MAPK-dependent NF-kappaB activation, resulting in subsequent GM-CSF release. C. pneumoniae-induced epithelial cytokine liberation may contribute significantly to inflammatory airway diseases like chronic obstructive pulmonary disease (COPD) or bronchial asthma.