Cell Surface Display of the Chlamydial Glycolipid Exoantigen (GLXA) Demonstrated by Antibody-Dependent Complement-Mediated Cytotoxicity

Abstract

The chlamydial species are Gram-negative bacterial pathogens critical to human health. Their developmental cycle is associated with the formation and release of the broadly conserved glycolipid exoantigen (GLXA), which has been implicated in the chlamydial elementary body-host cell interaction. This study examines the potential surface display of this glycolipid by chlamydiae-infected cells and the ability of the GLXA they secrete to associate with the plasma membranes of uninfected cells, a prerequisite for exerting influence on them. The sequential incubation of anti-GLXA antibody and complement with Chlamydia trachomatis serovar K or C. pneumoniae AR-39-infected HeLa 229 or macrophage cells resulted in significant cellular cytotoxicity, which preceded the formation of mature elementary bodies. For uninfected cells, co-incubation of GLXA, purified from supernatants of either C. trachomatis or C. pneumoniae-infected HeLa 229 cells, followed by the successive addition of mouse anti-GLXA antibody and complement, yielded similar levels of cellular cytotoxicity. Thus, GLXA indeed is displayed on the surface of infected cells and, therefore, if antibody of appropriate specificity were present, this GLXA could serve to target these infected cells for elimination. Furthermore, released GLXA can associate with uninfected cells and therefore would be positioned to influence their behavior, especially in the context of infection.

The glycolipid exoantigen derived from Chlamydia muridarum activates invariant natural killer T cells

“…7 Chlamydial glycolipid exoantigen (GLXA) is a glycolipid component of the chlamydial membrane and intracellular inclusion bodies, which has been implicated in chlamydial-host cell interaction, and can also be found in the host cell cytoplasm and micromilieu of infected cells. [8][9][10][11][12][13] It is different from chlamydial lipopolysaccharide and possesses a polysaccharide epitope having weak immunogenicity. 8,9,11 Moreover, GLXA has been exploited for its use as a vaccine candidate against the infection.…”

“…[8][9][10][11][12][13] It is different from chlamydial lipopolysaccharide and possesses a polysaccharide epitope having weak immunogenicity. 8,9,11 Moreover, GLXA has been exploited for its use as a vaccine candidate against the infection. 14, 15 Due to poor immunogenicity of the epitope, a monoclonal anti-idiotypic antibody (mAb2) to the epitope has been generated, which mimics the biological features of the epitope.…”

Detection of Chlamydia in the peripheral blood cells of normal donors using in vitroculture, immunofluorescence microscopy and flow cytometry techniques

“…Chlamydiae are known to infect macrophages in vivo [ 17 - 19 ] and in vitro the J774A.1 macrophage monolayers are readily infected by Chlamydia and support growth for ~120 h pi. Using an effective culture method we developed previously and have described [ 30 - 33 ], WBC lysates were prepared and tested in duplicate on J774A.1 monolayers. At 96 h pi the monolayers were rinsed, fixed, and immunostained to detect Chlamydia .…”