Cloning, Expression and Purification of Truncated Chlamydia Trachomatis Outer Membrane Protein 2 (Omp2) and its Application in an ELISA Assay

Background: Although a simple and direct method does not exist for the detection of chlamydial infections, there are situations in which reliable serological tests, with sensi-tivity related to a specific antigen, could be helpful. Objective: The aim of this study was to clone the first 1100 bp of the C. trachomatis outer membrane protein 2 (omp2) gene in order to prepare a recombinant protein for use in an ELISA system designed to recognize the anti- C. trachomatis antibody in patient sera. Methods: The PCR product of the chlamydial omp2 gene was cloned in pBluescript and its first 1100 bp was sub-cloned in the pQE-30 expression vector and induced by IPTG. The recombinant protein was purified by affinity chromatography and its purity was confirmed by SDS-PAGE, gel diffusion and western blot analyses. The purified protein was coated onto a polysty-rene microplate and tested by ELISA using patient serum. Results: We have cloned, over-expressed and purified biologically functional recombinant truncated Omp2 from C. trachomatis for use, as a species-specific recognition antigen, in an ELISA system. In this study we determined a cut-off value of 0.345 for this ELISA system using 55 negative sera and measured six positive sera at dilutions of 1:20-1:2560. Conclusion: As a species-specific recognition antigen, the over-expressed and purified recombinant truncated Omp2 from C. trachomatis performed well in an ELISA system.