Adhesins and Host Serum Factors Drive Yop Translocation by Yersinia into Professional Phagocytes during Animal Infection

Abstract

Yersinia delivers Yops into numerous types of cultured cells, but predominantly into professional phagocytes and B cells during animal infection. The basis for this cellular tropism during animal infection is not understood. This work demonstrates that efficient and specific Yop translocation into phagocytes by Yersinia pseudotuberculosis (Yptb) is a multi-factorial process requiring several adhesins and host complement. When WT Yptb or a multiple adhesin mutant strain, ΔailΔinvΔyadA, colonized tissues to comparable levels, ΔailΔinvΔyadA translocated Yops into significantly fewer cells, demonstrating that these adhesins are critical for translocation into high numbers of cells. However, phagocytes were still selectively targeted for translocation, indicating that other bacterial and/or host factors contribute to this function. Complement depletion showed that complement-restricted infection by ΔailΔinvΔyadA but not WT, indicating that adhesins disarm complement in mice either by prevention of opsonophagocytosis or by suppressing production of pro-inflammatory cytokines. Furthermore, in the absence of the three adhesins and complement, the spectrum of cells targeted for translocation was significantly altered, indicating that Yersinia adhesins and complement direct Yop translocation into neutrophils during animal infection. In summary, these findings demonstrate that in infected tissues, Yersinia uses adhesins both to disarm complement-dependent killing and to efficiently translocate Yops into phagocytes.

Alveolar Macrophages and Neutrophils Are the Primary Reservoirs for Legionella pneumophila and Mediate Cytosolic Surveillance of Type IV Secretion

“…Therefore, we set out to identify host cells that receive T4SS-translocated effectors during infection with L. pneumophila. BlaM reporter systems have been used during in vivo infection with Yersinia pseudotuberculosis (67,68), Yersinia pestis (69,70), Yersinia enterocolitica (71), Salmonella enterica serovar Typhimurium (72,73), and Pseudomonas aeruginosa (74,75) to detect the translocation of effectors into host cells by the type III and type IV secretion systems. We demonstrate in this study that by using ␤-lactamase (BlaM) translationally fused to the T4SS-translocated effector protein RalF, we can successfully track injection by the T4SS into host cells during both in vitro and in vivo infection, and we describe the first use of this BlaM reporter during in vivo pulmonary infection with L. pneumophila.…”

Effector CD8+T Cells Are Generated in Response to an Immunodominant Epitope in Type III Effector YopE during Primary Yersinia pseudotuberculosis Infection

“…YopE functions as an antiphagocytic factor (22) and also as an inhibitor of the generation of reactive oxygen species (ROS) (23). In mice infected with Y. pseudotuberculosis, YopE is translocated preferentially into neutrophils but also into APCs such as dendritic cells, macrophages, and B cells (24). The eukaryotic host cell targets of YopE include the small GTPases RhoA, Rac1, and Rac2 (22,23,25,26).…”

Yersinia pestis YopK Inhibits Bacterial Adhesion to Host Cells by Binding to the Extracellular Matrix Adaptor Protein Matrilin-2

“…Adhesins anchored on bacterial membranes tether bacteria to host cells, whereas free molecules of YopK impede the intimate bacterium-host cell contacts by binding to MATN2, an ECM protein ubiquitously expressed at the surface of eukaryotic cells. Our results explain why pla, psa, and ail mutations hamper Yop delivery (38), whereas a yopK mutation leads to a hypertranslocation phenotype (12).…”

“…All these adhesins are outer membrane proteins that are firmly embedded in the bacterial membrane. Despite the functional differences among these adhesins, defects in any of them impair the efficient translocation of Yops (25,38).…”