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Live-Cell Forward Genetic Approach to Identify and Isolate Developmental Mutants in Chlamydia trachomatis
Published on: June 10, 2020
Immunoreactivity and differential developmental expression of known and putative Chlamydia trachomatis membrane
João P Gomes1, Ru-ching Hsia, Sally Mead
1Department of Bacteriology, National Institute of Health, Avenue Padre Cruz, 1649-016 Lisbon, Portugal.
Abstract:
Chlamydia trachomatis is an intracellular bacterium that causes ocular and urogenital diseases worldwide. Membrane proteins have only been partially characterized, and the discovery of a nine-member polymorphic membrane protein gene family has enhanced interest in defining their function. We previously reported two putative insertion sequence-like elements in pmpC for biovariant Ba and one each for G and L2, suggesting horizontal gene transfer. Because of this and the tissue tropism differences for these biovariants, we analyzed by quantitative real-time RT-PCR pmpC expression relative to immunogenic protein genes ompA, groEL and gseA throughout development. Sera from infected adolescents were reacted by immunoblot against recombinant (r)PmpC and rMOMP. ompA and groEL revealed different developmental transcriptome profiles among the biovariants. pmpC expression occurred at 2 h, peaked at 18 for L2 (at 24 for Ba and G), with the highest mRNA levels throughout development for L2. pmpC expression as a function of time paralleled ompA expression with higher mRNA levels compared with groEL later in development. Only sera from D-, E- and G-infected patients reacted to rPmpC; all infected patients reacted to rMOMP. pmpC expression during logarithmic growth suggests a role in membrane building and/or integrity, which is supported by the presence of a signal peptidase and C-terminal phenylalanine in PmpC. Because phylogenetic analyses of pmpC segregate serovars according to tissue tropism, we speculate that biovariant transcriptome differences may contribute to this tropism. The heterogeneous biovariant pmpC expression throughout development and differential PmpC immunoreactivity also suggest a role for pmpC in antigenic variation.
Insights
Chlamydia trachomatis polymorphic membrane protein C (pmpC) expression varies by biovariant, suggesting roles in tissue tropism and immune evasion. This bacterium causes global ocular and urogenital infections.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Chlamydia trachomatis causes significant global ocular and urogenital diseases.
- The polymorphic membrane protein (PMP) gene family, including pmpC, is crucial for C. trachomatis virulence but remains incompletely understood.
- Previous findings suggested horizontal gene transfer in pmpC and differential tissue tropism among biovariants.
Purpose of the Study:
- To investigate the developmental expression profile of pmpC in different C. trachomatis biovariants.
- To explore the potential role of pmpC in bacterial development, tissue tropism, and immune response.
- To analyze the immunoreactivity of PmpC in patient sera.
Main Methods:
- Quantitative real-time RT-PCR was used to measure pmpC gene expression relative to ompA, groEL, and gseA throughout development.
- Immunoblot assays were performed using sera from infected individuals against recombinant PmpC (rPmpC) and recombinant MOMP (rMOMP).
Main Results:
- pmpC expression varied significantly across biovariants (Ba, G, L2), with L2 exhibiting the highest mRNA levels throughout development.
- pmpC expression kinetics paralleled ompA expression, particularly later in development, suggesting coordinated regulation.
- Differential immunoreactivity was observed, with only sera from C. trachomatis serovars D, E, and G reacting to rPmpC, while all reacted to rMOMP.
Conclusions:
- Heterogeneous pmpC expression and differential immunoreactivity suggest a role for pmpC in antigenic variation and potential contribution to C. trachomatis tissue tropism.
- The presence of a signal peptidase and specific C-terminal amino acid in PmpC supports its proposed function in membrane biogenesis or integrity.
- Understanding pmpC's role is critical for developing effective diagnostics and therapeutics against C. trachomatis infections.
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