Detection of surface-exposed epitopes on Chlamydia trachomatis by immune electron microscopy
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B A Collett1, W J Newhall, R A Jersild
1Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis 46223.
Abstract:
The cell surfaces of two Chlamydia trachomatis serovars were explored by immune electron microscopy with monoclonal antibodies that recognize a number of chlamydial outer-membrane components. Species, subspecies and serovar-reactive epitopes on the major outer-membrane protein (MOMP) of a lymphogranuloma venereum biovar strain, L2/434/Bu, and a trachoma biovar strain, F/UW-6/Cx, were exposed on the surfaces of both elementary bodies (EBs) and reticulate bodies (RBs). Three epitopes on MOMP were inaccessible on EBs and RBs of both strains. These included a genus-reactive, species-reactive, and a subspecies-reactive epitope. In contrast, genus-specific epitopes on lipopolysaccharide (LPS) were not detected on the EB surface, but were clearly expressed on RBs of both L2/434/Bu and F/UW-6/Cx chlamydiae. Antibodies specific for the 60 kDa and 12 kDa 'cysteine-rich' outer-membrane proteins did not react with surface epitopes on either EBs or RBs. These data provide evidence that MOMP is a major surface antigen of both morphological forms, whereas some portions of the LPS molecule are exposed on the RB surface but become inaccessible to antibody after conversion to the infectious EB form.
Insights
Chlamydia trachomatis outer membrane proteins were studied using immune electron microscopy. Major outer-membrane protein (MOMP) is a surface antigen on both elementary bodies (EBs) and reticulate bodies (RBs), while lipopolysaccharide (LPS) is exposed on RBs but not EBs.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Chlamydia trachomatis is an obligate intracellular bacterium with distinct morphological forms: elementary bodies (EBs) and reticulate bodies (RBs).
- The bacterial cell surface, particularly outer membrane components, plays a crucial role in host-cell interaction and immune evasion.
Purpose of the Study:
- To investigate the surface exposure of Chlamydia trachomatis outer membrane components in different developmental stages.
- To characterize the immunogenic epitopes on major outer-membrane protein (MOMP) and lipopolysaccharide (LPS) of C. trachomatis serovars.
Main Methods:
- Immune electron microscopy was employed using monoclonal antibodies targeting various chlamydial outer membrane proteins.
- Two C. trachomatis serovars (lymphogranuloma venereum biovar L2/434/Bu and trachoma biovar F/UW-6/Cx) were analyzed at both EB and RB stages.
Main Results:
- Major outer-membrane protein (MOMP) epitopes, including genus, species, and serovar-reactive ones, were exposed on both EB and RB surfaces, with three exceptions.
- Genus-specific lipopolysaccharide (LPS) epitopes were detected on RBs but were inaccessible on the EB surface.
- Antibodies against 60 kDa and 12 kDa cysteine-rich outer membrane proteins did not react with surface epitopes on either form.
Conclusions:
- MOMP is a significant surface antigen present on both developmental forms of C. trachomatis.
- Lipopolysaccharide (LPS) epitopes are surface-exposed on reticulate bodies (RBs) but become masked upon conversion to the infectious elementary body (EB) form.