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Humoral immune response to plasmid protein pgp3 in patients with Chlamydia trachomatis infection
M Comanducci1, R Manetti, L Bini
1Immunobiological Research Institute Siena, Italy.
Abstract:
We identified, by two-dimensional electrophoretic analysis and microsequencing, a protein of Chlamydia trachomatis elementary bodies which corresponds to the polypeptide (pgp3) encoded by open reading frame 3 (ORF3). Amino acid analysis showed that the first residue (Gly) found in the native protein is the one encoded by the second ORF3 codon, implying a typical bacterial removal of the first Met residue. Relatively large amounts of recombinant pgp3 (r-pgp3) in a stable, water-soluble form were obtained by overexpressing ORF3 in Escherichia coli and purifying the product from periplasmic extracts under nondenaturing conditions. These r-pgp3 preparations allowed specific detection of anti-pgp3 antibodies by enzyme-linked immunosorbent assay. Analysis of a group of 170 sera from healthy blood donors and from patients who were seropositive or -negative for C. trachomatis and Chlamydia pneumoniae showed that an immune response to pgp3 occurs in the majority (ca. 81%) of patients with sexually transmitted diseases who are seropositive for C. trachomatis and generally correlates with the response to cell surface antigens. No reaction between r-pgp3 and C. pneumoniae-positive sera was detected.
Insights
Researchers identified a Chlamydia trachomatis protein (pgp3) and developed a recombinant form (r-pgp3). This recombinant protein effectively detects antibodies in most patients with sexually transmitted Chlamydia trachomatis infections.
Area of Science:
- Microbiology
- Immunology
- Protein Chemistry
Background:
- Chlamydia trachomatis is a significant cause of sexually transmitted diseases.
- Identifying specific antigens is crucial for developing diagnostic tools and understanding host-pathogen interactions.
Purpose of the Study:
- To identify and characterize a protein from Chlamydia trachomatis elementary bodies.
- To develop a recombinant form of the protein for antibody detection.
Main Methods:
- Two-dimensional electrophoresis and microsequencing to identify the protein (pgp3) encoded by ORF3.
- Overexpression of ORF3 in Escherichia coli to produce recombinant pgp3 (r-pgp3).
- Enzyme-linked immunosorbent assay (ELISA) to detect anti-pgp3 antibodies in human sera.
Main Results:
- The pgp3 protein was identified and its N-terminal processing characterized.
- Stable, water-soluble r-pgp3 was successfully produced and purified.
- ELISA demonstrated that 81% of Chlamydia trachomatis-seropositive patients mounted an immune response to pgp3, correlating with cell surface antigen response.
- No cross-reactivity was observed with Chlamydia pneumoniae-positive sera.
Conclusions:
- The pgp3 protein is a potential diagnostic marker for Chlamydia trachomatis infections.
- Recombinant pgp3 is a valuable tool for serological detection of Chlamydia trachomatis.
- The immune response to pgp3 is prevalent in Chlamydia trachomatis infections and specific, distinguishing it from Chlamydia pneumoniae.