Preliminary study on biological characterization of Chlamydia trachomatis plasmid protein p ORF5

Abstract

Objective To localize and characterize the plasmid protein pORF5 in the Chlamydia trachomatis(Ct) infected cells. Methods The open reading frame encoding for pORF5 protein from the Ct plasmid was amplified and cloned into the pGEX-6p vector. The recombinant plasmid pGEX-pORF5 was transformed into XL1-blue E. coli to express fusion protein with the glutathione-s-transferase (GST). After purified with Glutathione Sepharose 4B beads, the pORF5 fusion protein was used to immunize mice to make monoclonal and polyclonal antibody. The antibodies were used to localize the endogenous pORF5 protein and detect the expression pattern in Chlamydia-infected cells using an indirect immunofluorescence assay (IFA). At the same time, ELISA was used to determine whether pORF5 plasmid protein was expressed and immunogenic during Ct infection in humans. Results pORF5 was detected a dominant signal in the cytosol of the Chlamydia-infected cells with a pattern similar to that of anti-CPAF. pORF5 also appeared in the RBs and EBs in small quantity. Athough pattern was similarly, pORF5 did not overlap with CPAF. pORF5 protein was strongly recognized antiserum in an ELISA. Conclusion The pORF5 plasmid protein was identified as a secreted protein with good immunogenicity, pORF5 gene was to express the endogenous target protein during human infection. Key words: Chlamydia trachomatis; Plasmid; Secreted protein; pORF5