Vaccination with DNA vector expressing chlamydial low calcium response protein E (LcrE) against Chlamydophila pneumoniae infection

Chlamydophila pneumoniae is an obligate intracellular human pathogen, which causes acute respiratory tract infections and can also cause chronic infections. C. pneumoniae possess type III secretion system (TTSS), which allows them to secrete effector molecules into the inclusion membrane and the host cell cytosol. Low calcium response protein E (LcrE) is a part of TTSS. The gene of LcrE in a 6His-tagged form was cloned from C. pneumoniae CWL029, expressed and purified from Escherichia coli using the HIS-select TALON CellThru Resin, this gene was also cloned into a eukaryotic expression vector (pΔRC). One group of BALB/c mice received an intramuscular pΔRC inoculation then the mice were immunized with purified LcrE protein; the second group of mice was immunized two times with the recombinant plasmid (pΔRCLcrE), and the third group was primed with pΔRCLcrE inoculation then boosted with LcrE protein. LcrE-specific antibody response was induced by DNA immunization with a shift towards Th1 isotype pattern compared to protein-immunization, this shifting pattern was observed in plasmid primed then protein-boosted animals. DNA immunization given as a priming and followed by a protein booster significantly reduced the number of viable bacteria in the lungs after challenge with C. pneumoniae. These results confirm that immunization with pΔRCLcrE can be an effective part of a vaccination schedule against C. pneumoniae.