Novel Chlamydia muridarum T Cell Antigens Induce Protective Immunity against Lung and Genital Tract Infection in Murine Models

Using a combination of affinity chromatography and tandem mass spectrometry, we recently identified 8 MHC class II (I-A(b)) -bound Chlamydia peptides eluted from dendritic cells (DCs) infected with Chlamydia muridarum. In this study we cloned and purified the source proteins that contained each of these peptides and determined that three of the eight peptide/protein Ags were immunodominant (PmpG-1, RplF, and PmpE/F-2) as identified by IFN-gamma ELISPOT assay using splenocytes from C57BL/6 mice recovered from C. muridarum infection. To evaluate whether the three immunodominant Chlamydia protein Ags were also able to protect mice against Chlamydia infection in vivo, we adoptively transferred LPS-matured DCs transfected ex vivo with the cationic liposome DOTAP (N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate) and individual PmpG-1(25-500aa), RplF, or PmpE/F-2 (25-575 aa) proteins. The results showed that the transfected Chlamydia proteins were efficiently delivered intracellularly into DCs. Mice vaccinated with DCs transfected with individual Chlamydia protein PmpG-1(25-500), RplF, or PmpE/F-2(25-575) exhibited significant resistance to challenge infection as indicated by reduction in the median Chlamydia inclusion forming units in both the lung and genital tract models. The major outer membrane protein was used as a reference Ag but conferred significant protection only in the genital tract model. Overall, vaccination with DCs transfected with PmpG-1(25-500) exhibited the greatest degree of protective immunity among the four Chlamydia Ags tested. This study demonstrates that T cell peptide Ags identified by immunoproteomics can be successfully exploited as T cell protein-based subunit vaccines and that PmpG-1(25-500) protein may be a suitable vaccine candidate for further evaluation.