Quantitative proteome study of Chlamydia trachomatis ocular serovar B proteins associated with trachomatous trichiasis

Abstract

Purpose : The intracellular bacterium Chlamydia trachomatis (Ct) is the worldwide leading cause of preventable infectious blindness. The aim of the present study was to provide a proteome analysis of Ct ocular serovar B (CtB) elementary bodies (EB) by shotgun proteomics.

Methods : Relative quantification of trachoma-associated antigens was achieved by label-free-quantification. Four biological replicates were used for the qualitative and quantitative study of the CtB strain HAR-36 proteome. All were resolved by SDS PAGE and subjected to in-gel digestion by trypsin. For quantification purposes two biological replicates (out of the four used for shotgun experiments) were used. Both preparations (lyophilized and in solution) were electrophoretically resolved, gels were cut into 13 pieces each and in-gel trypsin digested. Both sets of peptides were analyzed by nano-LC-MS/MS (143 runs in total) in duplicates.

Results : Extensive profiling of CtB EBs was achieved, resulting in coverage of approximately 60% of the Ct genome. The most abundant proteins found include major outer membrane protein (MOMP), Elongation factor (EF) Tu, 60 kDa chaperonin Hp60 (GroEL_1), a hypothetical protein CT875 and ATP synthase subunit beta. Our findings also indicate that eight Pmps abundantly expressed in CtB EBs undergo extensive proteolytic processing, consistent with their function as autotransporters.

Conclusions : The biggest differences in Pmps relative content between ocular and genital serovars were found in PmpD and PmpI. The antigens most relevant for trachomatous trichiasis discovered by immunoproteomics are also the most abundant proteins of CtB (GroEL_1, MOMP, EF-Tu, Type III secretion system ATPase).
Our data add to the understanding of structure and function of proteins of the infectious form of Ct ocular serovar B thereby extending the current knowledge on immunogenic antigens for vaccine development.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.