Protection against Chlamydia trachomatis infection in vitro and modulation of inflammatory response in vivo by membrane-bound glycosaminoglycans

Susceptibility of Chlamydia trachomatis to the excipient hydroxyethyl cellulose: pH and concentration dependence of antimicrobial activity

Hydroxyethyl cellulose (HEC) is used as a neutral excipient in microbicides used against sexually transmitted pathogens. However, HEC inhibits the infection of cervical epithelial cells by Chlamydia trachomatis at pH 5 in a concentration-dependent manner. At pH 7, infection is inversely dependent on the concentration of HEC, possibly due to pH-dependent calcium sequestration.

The Chlamydia outer membrane protein OmcB is required for adhesion and exhibits biovar-specific differences in glycosaminoglycan binding

Chlamydia pneumoniae, an obligate intracellular human pathogen, causes a number of respiratory diseases. We explored the role of the conserved OmcB protein in C. pneumoniae infections, using yeast display technology. (i) Yeast cells presenting OmcB were found to adhere to human epithelial cells. (ii) Pre-incubation of OmcB yeast cells with heparin, but not other glycosaminoglycans (GAGs), abrogated adhesion. (iii) Pre-treatment of the target cells with heparinase inhibited adherence, and GAG-deficient CHO cell lines failed to bind OmcB yeast. (iv) A heparin-binding motif present near the N-terminus of OmcB is required for host cell binding. (v) Pre-treatment of chlamydial elementary bodies (EBs) with anti-OmcB antibody or pre-incubation of target cells with recombinant OmcB protein reduced infectivity upon challenge with C. pneumoniae. (vi) Adhesion of fluorescently labelled EBs to epithelial or endothelial cells was abrogated by prior addition of heparin or OmcB protein. Thus, C. pneumoniae OmcB is an adhesin that binds heparan sulphate-like GAGs. OmcB from Chlamydia trachomatis serovar L1 also adheres to human cells in a heparin-dependent way, unlike its counterpart from serovar E. We show that a single position in the OmcB sequence determines heparin dependence/independence, and variations there may reflect differences between the two serovars in cell tropism and disease pattern.

Involvement of glycosaminoglycans in the attachment of pneumococci to nasopharyngeal epithelial cells

Streptococcus pneumoniae is a major bacterial pathogen involved in the development of otitis media. The pathogenic mechanisms of this middle ear disease, including the bacterial adherence mechanisms to the mucosal epithelial cells of the host, are poorly understood. In this study, the role of glycosaminoglycans in the adhesion of pneumococci to mucosal epithelial cells is examined. Both nasopharyngeal epithelium from rats and an oral epithelial cell line were used for pneumococcal adherence experiments. Preincubation of pneumococci with heparin, heparan sulfate (HS) and to a lesser extent, chondroitin 4-sulfate (C-4S), was found to inhibit attachment of S. pneumoniae to oral epithelial cells, while dermatan sulfate and hyaluronate did not interfere with pneumococcal binding. Enzymatic removal of HS moieties by heparinase III from nasopharyngeal epithelial cells abolished the attachment of pneumococci to nasopharyngeal epithelium. This study demonstrates that heparin, HS and C-4S are involved in pneumococcal binding to mucosal epithelial cells. This knowledge may contribute to the development of a new prophylactic strategy for otitis media.