Chlamydia psittaci: new insights into genomic diversity, clinical pathology, host-pathogen interaction and anti-bacterial immunity.

The distinctive and unique features of the avian and mammalian zoonotic pathogen Chlamydia (C.) psittaci include the fulminant course of clinical disease, the remarkably wide host range and the high proportion of latent infections that are not leading to overt disease. Current knowledge on associated diseases is rather poor, even in comparison to other chlamydial agents. In the present paper, we explain and summarize the major findings of a national research network that focused on the elucidation of host-pathogen interactions in vitro and in animal models of C. psittaci infection, with the objective of improving our understanding of genomics, pathology, pathophysiology, molecular pathogenesis and immunology, and conceiving new approaches to therapy. We discuss new findings on comparative genome analysis, the complexity of pathophysiological interactions and systemic consequences, local immune response, the role of the complement system and antigen presentation pathways in the general context of state-of-the-art knowledge on chlamydial infections in humans and animals and single out relevant research topics to fill remaining knowledge gaps on this important yet somewhat neglected pathogen.

Chlamydia psittaci inclusion membrane protein IncB associates with host protein Snapin.

Chlamydia (C.) psittaci, the causative agent of psittacosis in birds and humans, is the most important zoonotic pathogen of the family Chlamydiaceae. During a unique developmental cycle of this obligate intracellular pathogen, the infectious elementary body gains access to the susceptible host cell, where it transforms into the replicative reticulate body. C. psittaci uses dynein motor proteins for optimal early development. Chlamydial proteins that mediate this process are unknown. Two-hybrid screening with the C. psittaci inclusion protein IncB as bait against a HeLa Yeast Two-hybrid (YTH) library revealed that the host protein Snapin interacts with IncB. Snapin is a cytoplasmic protein that plays a multivalent role in intracellular trafficking. Confocal fluorescence microscopy using an IncB-specific antibody demonstrated that IncB, Snapin, and dynein were co-localized near the inclusion of C. psittaci-infected HEp-2 cells. This co-localization was lost when Snapin was depleted by RNAi. The interaction of Snapin with both IncB and dynein has been shown in vitro and in vivo. We propose that Snapin connects chlamydial inclusions with the microtubule network by interacting with both IncB and dynein.