Cloning and expression inEscherichia coliof a species-specificChlamydia trachomatisouter membrane antigen

A gene library of Chlamydia trachomatis serovar L2 (strain 434) was constructed in Escherichia coli using plasmid pBR322. Amongst 200 recombinants we have identified and characterized a recombinant E. coli that expresses a protein antigen of Mr 74 000 similar in size to an outer membrane antigen produced by elementary bodies of C. trachomatis. Immunologically, the molecule synthesised by E. coli has the same specificity as the protein encoded by serovar L2. A 1.8 kb DNA fragment from the recombinant insert, used as a hybridization probe, confirmed the species specificity of this clone at the gene level.