Transcription, expression, localization and immunoreactivity of Chlamydophila pneumoniae Phospholipase D protein

Chlamydophila pneumoniae, a recognized aethiological agent of respiratory infection, is also suspected to play a immuno-pathogenetic role in atherosclerosis by contributing to inflammation and plaque instability. Phospholipase D (PLD) is an enzyme involved in lipid metabolism, in protein transport and signal transduction, all events which can direct or indirect impact on virulence and inflammatory response. To better understand the role of PLD in cell biology and infection by C. pneumoniae, we cloned and expressed the pld gene in Escherichia coli and generated the recombinant PLD (rCpPLD). This product was highly immunogenic in mice, and capable to efficiently detect anti-PLD antibodies in humans. As shown by real-time PCR, PLD gene was expressed in a bi-phasic pattern, with transcriptional peaks corresponding to early and late chlamydial development. Fluorescence microscopy showed that CpPLD localized mostly in the center of inclusion bodies between 8 and 48 h from infection and at the periphery of inclusions at 72 h. Overall, PLD appears consistently expressed during the developmental cycle of C. pneumoniae and is sensed by the host as an antigen target during infection/exposure to this microorganism. rCpPLD may be a useful tool for future studies concerning the role that this enzyme plays in the pathology of, and immune response to, C. pneumoniae.