Distinct intensity of host-pathogen interactions in Chlamydia psittaci- and Chlamydia abortus-infected chicken embryos.
Factors and mechanisms determining the differences in virulence and host specificity between the zoonotic agents Chlamydia psittaci and Chlamydia abortus are still largely unknown. In the present study, two strains were compared for their invasiveness, virulence, and capability of eliciting an immune response in chicken embryos. On breeding day 10, embryonated chicken eggs were inoculated with 5 × 10(4) inclusion-forming units. As shown by immunohistochemistry and quantitative real-time PCR, C. psittaci displayed a significantly better capability of disseminating in the chorioallantoic membrane (CAM) and internal organs than C. abortus. The higher infectious potential of C. psittaci in birds was underlined by significantly higher mRNA expression rates of essential chlamydial genes, such as incA, groEL (in CAM, liver, and spleen), cpaf, and ftsW (in CAM). Although the immune responses to both pathogens were similar, C. psittaci elicited higher macrophage numbers and a stronger expression of a subset of immune-related proteins. The data imply that invasiveness of Chlamydia spp. and propagation in the host are not solely dependent on the level of host immune response but, even to a greater extent, on the expression of bacterial factors related to virulence. The fact that C. psittaci has coped far better than C. abortus with the avian embryo's response by upregulating essential genes may be a key to understanding the mechanisms underlying host adaptation and etiopathology.
Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Jena, Germany.
Maria
M
Braukmann
Konrad
K
Sachse
Ilse D
ID
Jacobsen
Martin
M
Westermann
Christian
C
Menge
Hans-Peter
HP
Saluz
Angela
A
Berndt
D000818:Animals; D002642:Chick Embryo; D002690:Chlamydia Infections / Q000276:immunology / Q000382:microbiology / Q000473:pathology*; D023501:Chlamydophila / Q000276:immunology / Q000472:pathogenicity*; D023521:Chlamydophila Infections / Q000276:immunology / Q000382:microbiology / Q000473:pathology*; D002691:Chlamydophila psittaci / Q000276:immunology / Q000472:pathogenicity*; D004195:Disease Models, Animal; D020869:Gene Expression Profiling; D054884:Host-Pathogen Interactions; D007150:Immunohistochemistry; D008264:Macrophages / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D014774:Virulence; D037521:Virulence Factors / Q000096:biosynthesis
D037521:Virulence Factors