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Quantification of Cytosolic vs. Vacuolar Salmonella in Primary Macrophages by Differential Permeabilization
09:25

Quantification of Cytosolic vs. Vacuolar Salmonella in Primary Macrophages by Differential Permeabilization

Published on: July 28, 2015

The mechanism of Salmonella entry determines the vacuolar environment and intracellular gene expression

Dan Drecktrah1, Leigh A Knodler, Robin Ireland

  • 1Laboratory of Intracellular Parasites, National Institutes of Allergy and Infectious Diseases, Rocky Mountain Laboratories, Hamilton, MT 59840, USA.

Traffic (Copenhagen, Denmark)
|February 1, 2006
PubMed

Insights

Salmonella entry into macrophages affects its survival and virulence gene expression. Different internalization methods alter the Salmonella-containing vacuole environment and type III secretion system (TTSS) gene regulation.

Area of Science:

  • Microbiology
  • Immunology
  • Cell Biology

Background:

  • Macrophages are key hosts for Salmonella during systemic infections.
  • Salmonella utilizes two type III secretion systems (TTSS), SPI1 and SPI2, for invasion and intracellular survival, respectively.
  • Salmonella can enter macrophages via SPI1-dependent invasion or host cell-mediated phagocytosis.

Purpose of the Study:

  • To investigate how Salmonella internalization mechanisms influence the intracellular environment.
  • To determine the impact of entry method on TTSS gene expression within macrophages.

Main Methods:

  • Comparing intracellular survival rates of Salmonella based on opsonization (complement, IgG) and SPI1 induction.
  • Analyzing the acidification kinetics of the Salmonella-containing vacuole.
  • Utilizing quantitative polymerase chain reaction (qPCR) to assess SPI1 and SPI2 gene expression.

Main Results:

  • Bacterial replication varied significantly based on entry route; complement-opsonized and SPI1-induced Salmonella replicated, while IgG-opsonized and non-opsonized bacteria were initially killed.
  • Vacuolar acidification was faster for non-opsonized or SPI1-induced Salmonella compared to IgG-opsonized or complement-opsonized bacteria.
  • SPI2 gene induction was dependent on the internalization mechanism, and unexpectedly, SPI1 genes were induced intracellularly after phagocytic uptake.

Conclusions:

  • The mechanism of Salmonella entry into macrophages critically impacts intracellular survival and vacuolar environment.
  • Internalization route dictates the transcriptional response of key virulence genes (SPI1 and SPI2).
  • Phagocytic uptake can lead to intracellular induction of SPI1 genes, revealing a novel regulatory mechanism in Salmonella-macrophage interactions.

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