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Enhancing effect of Salmonella enteritidis SPA on nonspecific resistance
Abstract:
The peritoneal macrophages from mice treated with soluble protective antigen (SPA) or lipopolysaccharide (LPS) showed an increase in chemotactic activity, but muramyl dipeptide (MDP)-induced macrophages did not show any enhancing effect. Conversely, the chemotactic activity of mice peritoneal neutrophils was enhanced by SPA, LPS or MDP treatment. The superoxide anion (O2-)-generating activity of SPA-induced macrophages was higher than LPS or MDP. And even 30 days after SPA treatment, a significant increase of O2(-)-generating activity was evident as compared to the control. SPA-induced macrophages showed a higher degree of intracellular killing of Listeria monocytogenes, in vitro, as compared to macrophages obtained from normal mice. In the studies of in vivo protection, the number of bacteria in the liver after challenging with L. monocytogenes was smaller in SPA-treated mice than in untreated mice. Also, SPA-treated mice showed an increased resistance to L. monocytogenes infection.
Insights
Soluble protective antigen (SPA) enhances immune cell activity and Listeria monocytogenes killing in mice. SPA-treated mice exhibit increased resistance to infection, demonstrating its protective potential.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- The immune system's response to pathogens is crucial for host defense.
- Macrophages and neutrophils are key immune cells involved in combating bacterial infections.
- Soluble protective antigen (SPA) is a component of certain bacterial pathogens.
Purpose of the Study:
- To investigate the immunomodulatory effects of SPA on peritoneal macrophages and neutrophils.
- To assess the impact of SPA on the intracellular killing of Listeria monocytogenes.
- To evaluate the in vivo protective efficacy of SPA against L. monocytogenes infection.
Main Methods:
- Peritoneal macrophages and neutrophils were isolated from mice treated with SPA, lipopolysaccharide (LPS), or muramyl dipeptide (MDP).
- Chemotactic activity and superoxide anion (O2-)-generating activity of these cells were measured.
- In vitro intracellular killing assays using Listeria monocytogenes were performed.
- In vivo protection studies involved challenging SPA-treated and untreated mice with L. monocytogenes.
Main Results:
- SPA and LPS enhanced macrophage chemotactic activity, while MDP did not.
- SPA, LPS, and MDP all increased neutrophil chemotactic activity.
- SPA-induced macrophages exhibited higher O2(-)-generating activity compared to LPS or MDP, with sustained elevation for at least 30 days.
- SPA-treated macrophages demonstrated enhanced in vitro killing of L. monocytogenes.
- In vivo, SPA-treated mice had fewer bacteria in the liver and showed increased resistance to L. monocytogenes infection.
Conclusions:
- SPA significantly enhances the functional activities of macrophages and neutrophils.
- SPA confers protection against Listeria monocytogenes infection by boosting innate immune responses.
- SPA demonstrates potential as an immunomodulatory agent for enhancing host defense against bacterial pathogens.