Analysis of the Humoral Immune Response to Chlamydia Outer Membrane Protein 2

The humoral immune response to Chlamydia outer membrane protein 2 (Omp2) was studied. Omp2 is a highly genus-conserved structural protein of all Chlamydia species, containing a variable N-terminal fragment. To analyze where the immunogenic parts were localized, seven highly purified truncated fusion proteins constituting different regions of the protein were produced (Chlamydia pneumoniae-Omp2(aa23-aa93), Chlamydia psittaci-Omp2(aa23-aa94), and Chlamydia trachomatis-Omp2(aa23-aa84, aa87-aa547, aa23-aa182, aa167-aa434, aa420-aa547)). By an enzyme-linked immunosorbent assay with serologically defined patient sera, Omp2 was found to be a major immunogen of both C. pneumoniae and C. trachomatis infections (P ≪ 0.0001). The humoral immune responses were not confined to any particular region of the Omp2 protein, and no species-specific anti-Omp2 immunoglobulins were detected.