Reproduction Abstracts

Background: Waddlia chondrophila (W. chondrophila) is an emerging abortifacient pathogen which has been identified in the placentae of humans and cattle. The organism is a member of the order Chlamydiales, and shares many similarities at the genome level, and in growth studies, with other well-characterised zoonotic chlamydial abortifacients, such as Chlamydia abortus (C. abortus). We have previously observed significant responses in the expression of pro-inflammatory mediators including CXCL8 following active infection with W. chondrophila. This study investigates the growth of the organism together with the signalling pathways responsible for CXCL-8 release in a ruminant placental cell line.

Methodology/Principal findings: Using qPCR, fluorescent immunocytochemistry and electron microscopy, we characterised the infection and growth of W. chondrophila within the ovine trophoblast AH-1 cell line. Inclusions were visible from 6 h post-infection (p.i.) and exponential growth of the organism could be observed over a 60h time-course. CXCL-8 release was significantly elevated in AH-1 cells at 24 h p.i. by active-infection with live W. chondrophila but not by exposure to UV-killed organisms. Chloramphenicol treatment of infected cells reduced, but did not completely ablate, CXCL-8 release indicating that active infection and organism growth are key stimuli for CXCL-8 release. MAPK signalling pathways have been demonstrated to be central to chlamydial induction of CXCL-8 in epithelial cells, and in this study we have now demonstrated that W. chondrophila induced phosphorylation of both p38 and p42/44 MAPK. Inhibition of either of these pathways significantly reduced the release of CXCL-8 in response to infection.

Conclusions/ significance: The abortifacient pathogen W. chondrophila actively infects and replicates within ruminant trophoblast cells, stimulating CXCL-8 release. Release of CXCL-8 is significantly reduced by inhibition of either p38 or p42/44 MAPK, indicating a key role for this pathway in the innate immune response to infection with W. chondrophila.