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.