IMMUNOREACTIVITY OF THE 60-KDA CYSTEINE-RICH PROTEINS OF CHLAMYDIA-TRACHOMATIS, CHLAMYDIA-PSITTACI AND CHLAMYDIA-PNEUMONIAE EXPRESSED IN ESCHERICHIA-COLI

The 60 kDa cysteine-rich proteins (CrPs) of Chlamydia are developmenta lly regulated outer envelope proteins synthesized late in the chlamydi al growth cycle. These proteins, found only on the extracellular infec tious elementary bodies, elicit major antibody responses in chlamydial infection. We have cloned and expressed in Escherichia coli the compl ete 60 kDa CrP genes from Chlamydia trachomatis, C. psittaci and C. pn eumoniae. The recombinant products were expressed as either 'native' p roteins or as fusions with the bacteriophage T7 gene 10 protein. Elect ron microscopy showed that recombinant proteins were produced as insol uble inclusions within the E. coil host cells. The recombinant 60 kDa CrPs were purified and used to raise high titre polyclonal antisera. I n immunoblot analysis these antisera reacted with the 60 kDa CrPs from purified elementary bodies of all three chlamydial species in a genus -specific manner. Further molecular analysis allowed the genus-specifi c cross-reacting epitopes to be localized by using overlapping synthet ic peptides covering the C. trachomatis 60 kDa CrP. Immunogold labelli ng experiments using purified infectious elementary bodies from the th ree chlamydial species indicated that the 60 kDa CrPs are not surface accessible to antibody binding.