Analysis of Cells Targeted by Salmonella Type III Secretion In Vivo

PLoS Pathogens

Fred Heffron¹  Kaoru Geddes¹  Frank Cruz III² 

[1] Department of Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, United States of America;Department of Pathology, Oregon Health and Science University, Portland, Oregon, United States of America

关键词: Salmonella;    Spleen;    Salmonellosis;    Secretion;    Neutrophils;    Macrophages;    Monocytes;    Cell fusion;   

DOI  :  10.1371/journal.ppat.0030196

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

The type III secretion systems (TTSS) encoded in Salmonella pathogenicity island-1 and -2 (SPI-1 and -2) are virulence factors required for specific phases of Salmonella infection in animal hosts. However, the host cell types targeted by the TTSS have not been determined. To investigate this, we have constructed translational fusions between the ß-lactamase reporter and a broad array of TTSS effectors secreted via SPI-1, SPI-2, or both. Secretion of the fusion protein to a host cell was determined by cleavage of a specific fluorescent substrate. In cultured cells, secretion of all six effectors could be observed. However, two to four days following i.p. infection of mice, only effectors secreted by SPI-2 were detected in spleen cells. The cells targeted were identified via staining with nine different cell surface markers followed by FACS analysis as well as by conventional cytological methods. The targeted cells include B and T lymphocytes, neutrophils, monocytes, and dendritic cells, but not mature macrophages. To further investigate replication in these various cell types, Salmonella derivatives were constructed that express a red fluorescent protein. Bacteria could be seen in each of the cell types above; however, most viable bacteria were present in neutrophils. We find that Salmonella is capable of targeting most phagocytic and non-phagocytic cells in the spleen but has a surprisingly high preference for neutrophils. These findings suggest that Salmonella specifically target splenic neutrophils presumably to attenuate their microbicidal functions, thereby promoting intracellular survival and replication in the mouse.

【 授权许可】

CC BY