Identification of conserved regions for species and subspecies specific epitopes on the major outer membrane protein of Chlamydia trachomatis

Abstract

Proteolytic peptides containing the serological epitopes present on the major outer membrane protein of Chlamydia trachomatis were studied by immunoblots. Monoclonal antibodies which have been defined by micro-immunofluorescence typing as serovar-, subspecies- and species-specific were utilized. The reactivity of either serovar-specific or species-specific monoclonal antibodies in the immunoblots was similar to that in the micro-immunofluorescence test. However, monoclonal antibodies which demonstrated subspecies-specific reactivity by the micro-immunofluorescence test expressed species-specific reactivity by the immunoblot method. The serovar-specific epitope which was identified on the major outer membrane protein was lost after proteolytic digestion with Staphylococcus aureus V8 protease. Immunoblots of the proteolytic fragments identified the species-specific epitope on several peptides and the subspecies-specific epitope on fewer peptides than those in which the species-specific epitope was identified. In addition, both the species and subspecies epitopes were present on the same fragments of different serovars. The data indicate that the species epitope is on conserved regions of the major outer membrane protein and is structurally clustered with a subspecies-specific epitope.