Waddlia chondrophila,: role of surface proteins in adhesion, internalization, and intracellular trafficking of this Chlamydia-related abortigenic agent in macrophages

• Research unit: COST
• Project number: C06.0100

Key words (English)

Chlamydia; Waddlia; macrophages; cell biology; chlamydial divisome; genome

Research programs (English)

COST-Action 855 - Animal Chlamydiosis and the Zoonotic Implications

Short description (English)

Waddlia chondrophila is an emerging pathogen. It has been independently isolated twice from aborted bovine foetuses. Serological studies indicate a role in ruminant and possibly human abortion. The medical importance has been recognised with W. chondrophila being chosen for full genome sequencing and characterisation. Unfortunately, virtually nothing is known of the pathogenesis and biology of this obligate intracellular bacteria. To fill this gap, we plan to initiate an investiga-tion into specific aspects of W. chondrophila pathogenesis used by this organism to invade and proliferate within the host. We will focus initially on three key areas: the bacterial outer membrane receptors, the cell cycle control mechanisms and cellular trafficking. The knowledge gained on the pathogenesis of W. chondrophila will help develop improved treatment and monitoring strategies. Furthermore, we hope we can take the first steps towards the identification of future vaccine targets to be developed through collaboration at a European level.

Further information (English)

Full name of research-institution/enterprise: Centre hospitalier universitaire vaudois CHUV Institut de Microbiologie IMU 03-321 Faculty of Biology and Medicine

Partners and International Organizations (English)

BE, BG, CH, DE, ES, FR, GR, HR, HU, IE, IL, IT, MK, NL, PL, SE, SI, UK

Abstract (English)

Waddlia chondrophila is a strict intracellular bacteria considered as a potential agent of miscarriage in both humans and bovines. It enters and multiplies rapidly within human macrophages and induces lysis of the infected cells. However, the strategy used by this Chlamydia-like organism to resist the microbicidal effectors of macrophages is unknown. Hence, we initiated an investigation of the intracellular trafficking of W. chondrophila in human macrophages to understand how these organisms invade and proliferate within host cells. The trafficking of W. chondrophila within monocyte-derived human macrophages was characterized by analysing the presence or the absence of various markers on the bacteria replicative vacuole at different times post infection. All vacuoles containing W. chondrophila acquired the early endosomal marker EEA1 (early endosome associated antigen) during the first 30 minutes following uptake. However, contrarily to the vacuoles containing heat-inactivated bacteria, the live W. chondrophila vacuoles never co-localised with the late endosome/lysosome markers LAMP1 (lysosomal associated membrane protein 1), v-ATPase (vacuolar proton pump) and lysotracker (acidic vacuoles), indicating the bacteria rapidly evade the endocytic pathway after internalisation. Instead of interacting with the endosomal pathway, W. chondrophila immediately colocalise with the mitochondrial marker mitotracker and shortly after with several endoplasmic reticulum (ER) resident proteins such as calnexin, PDI (protein disulfide isomerase) and KDEL (tetrapeptide motif for ER localization). The W. chondrophila vacuoles localise in the ER very early after uptake but become decorated with the various ER proteins only 4 hours post infection. Seven hours following uptake, more than 70% of the W. chondrophila vacuoles are surrounded by mitochondrial and ER markers. The acquisition of ER markers corresponds precisely to a significant increase in the differentiation of infectious metabolically inactive elementary bodies (infective stage) into non-infectious metabolically active reticulate bodies (replicative form) and thus to the beginning of bacterial replication. W. chondrophila survives to destruction by human macrophages likely by evading the endocytic pathway and by associating with mitochondria and the ER in order to sustain its replication. The intracellular trafficking of W. chondrophila in human macrophages represents a novel route that strongly differs from that used by all other members of the Chlamydiales order. How chlamydial division is regulated during trafficking is an aspect which is currently further investigated.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C06.0100