Yersinia pseudotuberculosis Efficiently Escapes Polymorphonuclear Neutrophils during Early Infection

Abstract

ABSTRACTThe human-pathogenic species of the Gram-negative genusYersiniapreferentially target and inactivate cells of the innate immune defense, suggesting that this is a critical step by which these bacteria avoid elimination and cause disease. In this study, bacterial interactions with dendritic cells, macrophages, and polymorphonuclear neutrophils (PMNs) in intestinal lymphoid tissues during earlyYersinia pseudotuberculosisinfection were analyzed. Wild-type bacteria were shown to interact mainly with dendritic cells, but not with PMNs, on day 1 postinfection, while avirulentyopHandyopEmutants interacted with PMNs as well as with dendritic cells. To unravel the role of PMNs during the early phase of infection, we depleted mice of PMNs by using an anti-Ly6G antibody, after which we could see more-efficient initial colonization by the wild-type strain as well as byyopH,yopE, andyopKmutants on day 1 postinfection. Dissemination ofyopH,yopE, andyopKmutants from the intestinal compartments to mesenteric lymph nodes was faster in PMN-depleted mice than in undepleted mice, emphasizing the importance of effective targeting of PMNs by theseYersiniaouter proteins (Yops). In conclusion, escape from interaction with PMNs due to the action of YopH, YopE, and YopK is a key feature of pathogenicYersiniaspecies that allows colonization and effective dissemination.