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.