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Updated: Sep 8, 2026
High-throughput Assay to Phenotype Salmonella enterica Typhimurium Association, Invasion, and Replication in Macrophages
Published on: August 11, 2014
Genetic requirements for salmonella-induced cytopathology in human monocyte-derived macrophages
Sara H Browne1, Marc L Lesnick, Donald G Guiney
1Department of Medicine, School of Medicine, University of California at San Diego, La Jolla 92093-0640, USA.
Abstract:
Infection of human macrophages with Salmonella enterica serovar Typhimurium or Salmonella enterica serovar Dublin produces delayed cytotoxicity characterized by cell detachment and associated apoptosis. Using a site-specific mutant in the SpvB active site, we verify that the ADP-ribosylation activity of SpvB is required for delayed cytotoxicity in human macrophages infected with Salmonella: SipB and the type III protein secretion system (TTSS) encoded by Salmonella pathogenicity island 1 (SPI1) are not involved, whereas the SPI2 TTSS is absolutely required for SpvB-dependent cytotoxicity. Furthermore, we show that infection of macrophage cultures with wild-type or sipB mutant bacteria led to a complete loss of polymerized actin in over half of the cells after 24 h. In contrast, macrophages infected with the spvB or SPI2 (ssaV or ssaJ) mutant strain retained normal F-actin filaments, despite similar numbers of intracellular bacteria. We conclude that SpvB and a functional SPI2 TTSS are essential for Salmonella-induced delayed cytotoxicity of human macrophages.
Insights
Salmonella Typhimurium and Dublin cause delayed cell death in human macrophages. The SpvB protein
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Salmonella enterica serovars Typhimurium and Dublin induce delayed cytotoxicity in human macrophages.
- This cytotoxicity involves cell detachment and apoptosis.
Purpose of the Study:
- To investigate the role of Salmonella SpvB ADP-ribosylation activity in delayed cytotoxicity.
- To determine the involvement of Salmonella Pathogenicity Island 1 (SPI1) and SPI2 type III protein secretion systems (TTSS) in this process.
Main Methods:
- Utilized site-specific mutants in the SpvB active site.
- Infected human macrophage cultures with wild-type and mutant Salmonella strains (spvB, sipB, SPI2 mutants).
- Assessed cytotoxicity, apoptosis, and F-actin filament integrity post-infection.
Main Results:
- SpvB ADP-ribosylation activity is essential for delayed cytotoxicity.
- SPI1 TTSS is not involved, but SPI2 TTSS is required for SpvB-dependent cytotoxicity.
- Salmonella infection leads to F-actin loss, dependent on SpvB and SPI2 TTSS.
Conclusions:
- SpvB and a functional SPI2 TTSS are critical for Salmonella-induced delayed cytotoxicity in human macrophages.
- The mechanism involves disruption of F-actin filaments.
